Patent Application
20220056168
The present disclosure relates to processes for polymerizing olefin(s) using dual catalyst systems. In particular, methods include combining a catalyst component slurry with a catalyst component solution to form a third catalyst composition and introducing the third composition into a polymerization reactor.
Gas-phase polymerization processes are valuable processes for polymerizing polyethylene and ethylene copolymers comprising polymerizing ethylene. Moreover polymerization processes in fluidized beds are particularly economical.
A number of methodologies used for delivering catalysts to reactors involve the catalyst being supported on an inert carrier such as silica. However, large particles (>25 micrometers) of the support material can be found in the finished polymer product. These particles may adversely affect polymer properties. This has been observed in film applications where silica particles appear as defects or gels.
For a typical methodology, a supported catalyst is added to a diluent to form a catalyst slurry and pumped to a polymerization reactor. A high solids concentration within the catalyst slurry is desirable to reduce the amount of slurry. A reduction in the amount of slurry reduces transportation expenses and also reduces the amount of diluent that must be ultimately isolated and either discarded or recycled. This separation process is timely and can greatly increase capital cost.
However, a high solids concentration typically increases the slurry viscosity. A high solids concentration also increases the amount of foaming which is typically generated in a catalyst slurry vessel. A high slurry viscosity and foaming often cause handling problems, storage problems as well as reactor injection problems.
Low viscosity diluents can be added to the slurry to reduce the viscosity. However, the reduced viscosity promotes settling of the slurry in the solution, which can result in plugging of reactor components and accumulation of solids on the walls of catalyst slurry vessels.
A second catalyst solution can be added (i.e. “trimmed”) to the slurry to adjust one or more properties “in-situ” of polymer being formed in a reactor. Such “trim” processes are very economical because they do not require a polymerization to cease in order to adjust polymer properties in the event a catalyst system is not behaving a desirable way. However, a second catalyst is typically delivered to the slurry as a low viscosity solution, which can promote settling of the slurry solution and subsequent gelling and/or plugging of reactor components.
There is a need for polymerization processes utilizing slurry solutions that do not form gels or foul a reactor and that are capable of forming low density polyolefins.
References for citing in an Information Disclosure Statement (37 CFR 1.97(h): U.S. Pub. No. 2016/0347874; U.S. Pub. No. 2010/0041841; U.S. Pat. Nos. 6,825,287; 6,689,847; 6,608,149; 6,605,675; 7,980,264; 7,973,112; U.S. Pub. No. 2019/0119413; WO 2019/027585; WO 2018/151903; U.S. Pub. No. US 2018/0155474.
The present disclosure relates to processes for polymerizing olefin(s) using dual catalyst systems. In particular, methods include combining a catalyst component slurry with a catalyst component solution to form a third catalyst composition and introducing the third composition into a polymerization reactor. The present disclosure further provides methods for preparing catalyst component slurries, catalyst component solutions, and the third catalyst compositions.
In at least one embodiment, a method for producing a polyolefin includes contacting a first composition and a second composition in a line to form a third composition, the first composition including a contact product of a first catalyst, a second catalyst, a support, an activator, a mineral oil, and a wax, and the second composition comprising a contact product of an activator, a diluent, and the first catalyst or the second catalyst. The method includes introducing the third composition from the line into a gas-phase fluidized bed reactor, exposing the third composition to polymerization conditions, and obtaining a polyolefin.
The present disclosure relates to processes for polymerizing olefin(s) using dual catalyst systems. In particular, methods include combining a catalyst component slurry with a catalyst component solution to form a third catalyst composition and introducing the third composition into a polymerization reactor. The present disclosure further provides methods for preparing catalyst component slurries, catalyst component solutions, and the third catalyst compositions.
Catalyst pairs or multi-catalyst mixtures can produce polymers having a molecular weight and composition distribution depending on the catalyst's response to the reactor conditions. In at least one embodiment, a method includes trimming a second catalyst.
Melt Index (MI), for example, is indicative of a polymer's molecular weight and the Melt Index Ratio (MIR) is indicative of the molecular weight distribution. A polymer that exhibits a higher MI has a shorter polymer chain length. As MIR increases, the molecular weight distribution (MWD) of the polymer broadens. A polymer that exhibits a narrower molecular weight distribution has a lower MIR.
MIR is High Load Melt Index (HLMI) divided by MI as determined by ASTM D1238. MI, also referred to as 12, reported in g/10 min, is determined according to ASTM D1238, 190° C., 2.16 kg load. HLMI, also referred to as I21, reported in g/10 min is determined according to ASTM D1238, 190° C., 21.6 kg load.
The present disclosure provides processes for forming polyethylene including polymerizing ethylene in the presence of a catalyst system in a reactor, where the catalyst system includes a first catalyst and a second catalyst.
In at least one embodiment, by extending this concept to mixed catalyst systems, the MIR can be adjusted by changing flow of trim solution to the reactor. By adding an additional catalyst system, the change in MI of each independent system results in a change in the breadth of the molecular weight distribution. Changing this breadth affects the MIR of the final product and may be used to tune the product properties.
As used herein, Mn is number average molecular weight, Mw is weight average molecular weight, and Mz is z average molecular weight, wt % is weight percent, and mol % is mole percent. Unless otherwise noted, all average molecular weights (e.g., Mw, Mn, Mz) are reported in units of g/mol. The MWD, also referred to as polydispersity index (PDI), is defined to be Mw divided by Mn.
Unless otherwise indicated, “catalyst productivity” is a measure of how many grams of polymer (P) are produced using a polymerization catalyst comprising W g of catalyst (cat), over a period of time of T hours; and may be expressed by the following formula: P/(T×W) and expressed in units of gPgcat−1 hr−1. Unless otherwise indicated, “catalyst activity” is a measure of how active the catalyst is and is reported as the mass of product polymer (P) produced per mole of catalyst (cat) used (kgP/molcat). Unless otherwise indicated, “conversion” is the amount of monomer that is converted to polymer product, and is reported as mol % and is calculated based on the polymer yield and the amount of monomer fed into the reactor.
An “olefin,” alternatively referred to as “alkene,” is a linear, branched, or cyclic compound of carbon and hydrogen having at least one double bond. For purposes of this specification and the claims appended thereto, when a polymer or copolymer is referred to as comprising an olefin, the olefin present in such polymer or copolymer is the polymerized form of the olefin. For example, when a copolymer is said to have an “ethylene” content of 35 wt % to 55 wt %, it is understood that the mer unit in the copolymer is derived from ethylene in the polymerization reaction and said derived units are present at 35 wt % to 55 wt %, based upon the weight of the copolymer. A “polymer” has two or more of the same or different mer units. A “homopolymer” is a polymer having mer units that are the same. A “copolymer” is a polymer having two or more mer units that are different from each other. A “terpolymer” is a polymer having three mer units that are different from each other. “Different” as used to refer to mer units indicates that the mer units differ from each other by at least one atom or are different isomerically. Accordingly, the definition of copolymer, as used herein, includes terpolymers and the like. An “ethylene polymer” or “ethylene copolymer” is a polymer or copolymer comprising at least 50 mole % ethylene derived units, a “propylene polymer” or “propylene copolymer” is a polymer or copolymer comprising at least 50 mole % propylene derived units, and so on.
For the purposes of the present disclosure, ethylene shall be considered an α-olefin.
For purposes of the present disclosure and claims thereto, the term “substituted” means that a hydrogen group has been replaced with a heteroatom, or a heteroatom containing group. For example, a “substituted hydrocarbyl” is a radical made of carbon and hydrogen where at least one hydrogen is replaced by a heteroatom or heteroatom containing group.
Unless otherwise indicated, room temperature is 23° C.
“Different” or “not the same” as used to refer to R groups in any formula herein (e.g., R2 and R8 or R4 and R10) or any substituent herein indicates that the groups or substituents differ from each other by at least one atom or are different isomerically.
The following abbreviations may be used herein: Me is methyl, Et is ethyl, Pr is propyl, cPr is cyclopropyl, nPr is n-propyl, iPr is isopropyl, Bu is butyl, nBu is normal butyl, iBu is isobutyl, sBu is sec-butyl, tBu is tert-butyl, Oct is octyl, Ph is phenyl, Bn is benzyl, MAO is methylalumoxane.
A “catalyst system” is a combination of at least two catalyst compounds, an activator, an optional co-activator, and an optional support material. For the purposes of the present disclosure, when catalyst systems are described as comprising neutral stable forms of the components, it is well understood by one of ordinary skill in the art, that the ionic form of the component is the form that reacts with the monomers to produce polymers. Catalyst systems, catalysts, and activators of the present disclosure are intended to embrace ionic forms in addition to the neutral forms of the compounds/components.
A metallocene catalyst is an organometallic compound with at least one π-bound cyclopentadienyl moiety (or substituted cyclopentadienyl moiety) and more frequently two π-bound cyclopentadienyl moieties or substituted cyclopentadienyl moieties bonded to a transition metal.
In the description herein, the metallocene catalyst may be described as a catalyst precursor, a pre-catalyst compound, metallocene catalyst compound or a transition metal compound, and these terms are used interchangeably. An “anionic ligand” is a negatively charged ligand which donates one or more pairs of electrons to a metal ion.
For purposes of the present disclosure, in relation to metallocene catalyst compounds, the term “substituted” means that a hydrogen group has been replaced with a hydrocarbyl group, a heteroatom, or a heteroatom containing group. For example, methyl cyclopentadiene (Cp) is a Cp group substituted with a methyl group.
“Alkoxides” include an oxygen atom bonded to an alkyl group that is a C1 to C10 hydrocarbyl. The alkyl group may be straight chain, branched, or cyclic. The alkyl group may be saturated or unsaturated. In at least one embodiment, the alkyl group may comprise at least one aromatic group.
“Asymmetric” as used in connection with the instant indenyl compounds means that the substitutions at the 4 positions are different, or the substitutions at the 2 positions are different, or the substitutions at the 4 positions are different and the substitutions at the 2 positions are different.
The properties and performance of the polyethylene may be advanced by the combination of: (1) varying reactor conditions such as reactor temperature, hydrogen concentration, comonomer concentration, and so on; and (2) selecting and feeding a dual catalyst system having a first catalyst and second catalyst trimmed or not with the first catalyst or the second catalyst.
With respect to at least one embodiment of the catalyst system, the first catalyst is a high molecular weight component and the second catalyst is a low molecular weight component. In other words, the first catalyst may provide primarily for a high molecular-weight portion of the polyethylene and the second catalyst may provide primarily for a low molecular weight portion of the polyethylene. In at least one embodiment, a dual catalyst system is present in a catalyst pot of a reactor system, and a molar ratio of a first catalyst to a second catalyst of the catalyst system is from 99:1 to 1:99, such as from 90:10 to 10:90, such as from 85:15 to 50:50, such as from 75:25 to 50:50, such as from 60:40 to 40:60. The first catalyst and or the second catalyst can be added to a polymerization process as a trim catalyst to adjust the molar ratio of first catalyst to second catalyst. In at least one embodiment, the first catalyst and the second catalyst are each a metallocene catalyst compound.
Hence, in at least one embodiment, metallocene bis(n-propylcyclopentadienyl) Hafnium (IV) dimethyl (also referred to as “HfP”), shown as structure (I) below may be selected as the first catalyst to produce a high molecular weight (HMW) component of the polymer. As used herein, an HMW polymer is a polymer having an Mw value of 110,000 g/mol or greater. In some instances, the first catalyst may be fed in slurry to the polymerization reactor. A second catalyst such as the metallocene meso and rac enantiomers of di(1-ethylindenyl) zirconium dimethyl (collectively referred to as “EtInd”), shown as structures (IIA) and (II-B) below, may be selected to produce a low molecular weight (LMW) component of the polymer. As used herein, an LMW polymer is a polymer having an Mw value of less than 110,000 g/mol. The second catalyst can be included in the same catalyst system as the first catalyst, e.g. may be co-supported with the first catalyst. Some or all of the first catalyst and/or second catalyst may be fed as a trim catalyst into the catalyst slurry (e.g., in-line/on-line) having the first catalyst in route to the polymerization reactor.
Of course, other metallocene catalysts (or non metallocene catalysts), as described herein, may be selected, and other catalyst system configurations carried out. The appropriate metallocene catalysts selected may depend on the specified properties of the polymer and the desired subsequent applications of the formed polymer resins, such as for pipe applications, packaging, film extrusion and cosmetics, blow-molding, injection molding, rotation molding applications, and so forth. The catalysts selected may include catalysts that promote good (high) or poor (low) incorporation of comonomer (e.g., 1-hexene) into the polyethylene, have a relatively high response to hydrogen concentration in the reactor or a relatively low response to reactor hydrogen concentration, and so forth. As used herein, good/high comonomer incorporation refers to a polyethylene formed by a process of the present disclosure, where the polyethylene has a comonomer content of 7 wt % or greater. As used herein, poor/low comonomer incorporation refers to a polyethylene formed by a process of the present disclosure, where the polyethylene has a comonomer content of less than 7 wt %.
By using structures such as Ethlnd as the second catalyst trimmed on-line at various ratios onto slurry feeding the first catalyst such as the first metallocene catalyst HfP, or vice versa, along with varying reactor conditions involving temperature, reaction mixture component concentrations, and the like, beneficial polyethylene products may be formed. In at least one embodiment, a reverse trim is employed considering the LMW catalyst species Ethlnd as the first catalyst and the HMW catalyst species HfP as the second catalyst or catalyst trim. Additionally, it should also be contemplated that for the distinct catalysts selected, some of the second catalyst may be initially co-deposited with the first catalyst on a common support, and the remaining amount of the first catalyst or second catalyst added as trim.
In at least one embodiment, the amount of first or second catalyst fed (or the catalyst trim ratio), and the reactor conditions (e.g., temperature and hydrogen concentration), may be varied to give a range of MI and MIR while maintaining polyethylene density. The embodiments may advantageously hold a broad range of MI's with the same catalyst system, e.g., the same dual catalyst system. For a catalyst system fed to the polymerization reactor, the polymer MI, MIR, density and CD may be controlled by varying reactor conditions such as the reactor mixture including operating temperature, hydrogen concentration, and comonomer concentration in the reaction mixture.
Table 1 summarizes some example aspects of reactor control with respect to polyethylene properties. For instance, the hydrogen/ethylene (H2/C2) weight ratio or mol ratio may be an adjustment or control knob or a “primary adjustment knob, for polyethylene MI adjustment. The comonomer-ethylene (e.g., Comonomer/C2) weight ratio or mol ratio may be an adjustment or control knob or a “primary” adjustment knob, for polyethylene density. The reactor temperature, and the weight or mol ratio of the two catalysts (or the catalyst trim ratio) may be an adjustment or control knob for the polyethylene MIR. Other adjustment and control points are considered. Moreover, a range of MIR values of the polymer can be considered for a given catalyst system used to produce the polymer. Other polymer properties such as density and MI may be calibrated. Furthermore, the techniques for reactor control described herein including the determinants considered in Table 1 may apply to (1) polyethylene product development, (2) direct control of the reactor during the actual production of the polyethylene, (3) targeted formulations development for reactor conditions for (a) various catalyst systems, (b) amounts of catalyst systems, (c) polyethylene grades or products, and so forth.
Exemplary ranges of MIR include 10 to 80, such as 15 to 70, such as 20 to 70, such as 20 to 65. Exemplary ranges of MI (grams/10 minutes) include 0.1 to 4 (e.g., for film), 5 to 50 or 5 to 100 (e.g., for molding such as rotational and/or injection molding), and so on. Exemplary ranges for density include 0.915 g/cm3 to 0.935 g/cm3, 0.912 g/cm3 to 0.940 g/cm3, 0.910 g/cm3 to 0.945 g/cm3, and the like.
Herein, at least one embodiment address the importance of developing well-controlled techniques for the formation of polyethylene copolymers holding a MWD×CD. Therefore, improving the physical properties of polymers with the tailored MWD×CD can be beneficial for commercially desirable products. Without judiciously tailoring MWD×CD, polyethylene copolymers could display some compromises among the desirable attribute, such as improving stiffness to the detriment of toughness for instance. Control of these properties may be achieved for the most part by the choice of the catalyst system.
In at least one embodiment, reactor temperature may be used as a control variable for MIR adjustment. Subsequently, at the chosen reactor temperature for a starting MIR, a trim-catalyst level may be added to further increase MIR until a pre-set MIR range is reached. The component concentrations in the polymerization mixture, such as hydrogen and comonomer (e.g., ethylene) concentrations may be adjusted for specific MI and density targets of the polyethylene at the given MIR range. The amount of trim catalyst and reactor concentration adjustments may be repeated for various levels of MIR range and specific MI and density targets.
Embodiments demonstrate a novel technology to independently control a polyethylene product's MIR from its MI and density in a single reactor environment. Consequently, some polyethylene products may have a wide range of MWD×CD compositions and product attribute combinations. For instance, some of the polyethylene polymers may have the same or similar nominal MI and density but different MIR and MWD×CD. Other polyethylene polymers in the instances have the same or similar nominal MI (I-2), density, and MIR but are different in MWD×CD. In some of the instances, the MI may range from 0.1 to 5.0 g/10 min, such as from 0.5 to 1.5 g/10 min, and the density may range from 0.913 to 0.925 g/cm3, or other ranges.
In at least one embodiment, the catalysts may be applied separately in a single-reactor or multiple-reactor polymerization systems. In some other embodiments, the multiple catalysts may be applied on a common support to a given reactor, applied via different supports, and/or utilized in reactor systems having a single polymerization reactor or more than one polymerization reactor, and so forth.
At least one embodiment is related to multiple catalysts, e.g., a first catalyst and a second catalyst, impregnated on a catalyst support for polymerization of monomer into a polymer. A catalyst support impregnated with multiple catalysts may be used to form polymeric materials with improved balance of properties, such as stiffness, environmental stress crack resistance (ESCR), toughness, processability, among others. Controlling the amounts and types of catalysts present on the support contributes to reach this balance. Selection of the catalysts and ratios may adjust the combined MWD of the polymer produced. The MWD can be controlled by combining catalysts giving the desired weight average molecular weight (Mw) and individual molecular weight distributions of the produced polymer. For example, the typical MWD for linear metallocene polymers is 2.5 to 3.5. Blend studies indicate it would be desirable to broaden this distribution by employing mixtures of catalysts that each provides different average molecular weights. The ratio of the Mw for a LMW component and a HMW component would be between 1:1 and 1:10, or about 1:2 and 1:5. When a support is impregnated with multiple catalysts, new polymeric materials with improved balance of stiffness, toughness and processability can be achieved, e.g., by controlling the amounts and types of catalysts present on the support. Appropriate selection of the catalysts and ratios may be used to adjust the MWD, short chain branch distribution (SCBD), and long chain branch distribution (LCBD) of the polymer, for example, to provide a polymer with a broad orthogonal composition distribution (BOCD). The MWD, SCBD, and LCBDs would be controlled by combining catalysts with the appropriate Mw, comonomer incorporation, and long chain branching (LCB) formation under the conditions of the polymerization. Polymers having a BOCD in which the comonomer is incorporated in the HMW chains can lead to improved physical properties, such as processability, stiffness, toughness, ESCR, and so forth. Controlled techniques for forming polyethylene copolymers having a broad orthogonal composition distribution may be beneficial.
A number of catalyst compositions containing single site, e.g., metallocene, catalysts have been used to prepare polyethylene copolymers, producing relatively homogeneous copolymers at good polymerization rates. In contrast to traditional Ziegler-Natta catalyst compositions, single site catalyst compositions, such as metallocene catalysts, are catalytic compounds in which each catalyst molecular structure can produce one or only a few polymerization sites. Single site catalysts often produce polyethylene copolymers that have a narrow molecular weight distribution. Although there are single site catalysts that can produce broader molecular weight distributions, these catalysts often show a narrowing of the molecular weight distribution as the reaction temperature is increased, for example, to increase production rates. Further, a single site catalyst will often incorporate comonomer among the molecules of the polyethylene copolymer at a relatively uniform rate. The MWD and the amount of comonomer incorporation can be used to determine a SCBD. For an ethylene alpha-olefin copolymer, short chain branching (SCB) on a polymer chain is typically created through comonomer incorporation during polymerization. The SCBD refers to the distribution of the short chains (comonomer) along the polymer backbone.
The resin is said to have a “broad SCBD” when the amount of SCB varies among the polyethylene molecules. When the amount of SCB is similar among the polyethylene molecules of different chain lengths, the SCBD is said to be “narrow”. SCBD is known to influence the properties of copolymers, such as extractable content stiffness, heat sealing, toughness, environmental stress crack resistance, among others. The MWD and SCBD of a polyolefin is largely dictated by the type of catalyst used and is often invariable for a given catalyst system. Polymers with broad SCBD are in general produced by Ziegler-Natta catalysts and chromium based catalysts, whereas metallocene catalysts normally produce polymers with narrow SCBD.
Using multiple pre-catalysts that are co-supported on a single support mixed with an activator, such as a silica methylaluminoxane (SMAO), can be economically advantageous by making the polymer product in one reactor instead of multiple ones. Additionally, using a single support also eases intimate mixing of the polymers while off improving the process relative to preparing a mixture of polymers of different Mw and density independently from multiple catalysts in a single reactor. As described herein, a pre-catalyst is a catalyst compound prior to exposure to activator. The catalysts can be co-supported during a single operation, or may be used in a trim operation, in which one or more additional catalysts are added to catalysts that are supported.
Evidence of the incorporation of comonomer into a polymer is indicated by the density of a polyethylene copolymer, with lower densities indicating higher incorporation. The difference in the densities of the low molecular weight (LMW) component and the high molecular weight (HMW) component would be greater than about 0.02, or greater than about 0.04, with the HMW component having a lower density than the LMW component.
Satisfactory control of the MWD and SCBD lead to the adjustment of these factors, which can be adjusted by tuning the relative amount of the two pre-catalysts on the support. This may be adjusted during the formation of the pre-catalysts, for instance, by supporting two catalysts on a single support. In at least one embodiment, the relative amounts of the pre-catalysts can be adjusted by adding one of the components to a catalyst mixture progressing into the reactor in a process termed “trim.” Furthermore, the amount of catalyst addition can be controlled by means of feedback of polymer property data obtained.
Moreover, a variety of polymers with different MWD, SCBD, and LCBD may be prepared from a limited number of catalysts. Indeed, the pre-catalysts should trim well onto activator supports. Two parameters that benefit trimming well are solubility in alkane solvents and rapid supportation on the catalyst slurry en-route to the reactor. This favors the use of MCNs to achieve controlled MWD, SCBD, and LCBD. Techniques for selecting catalysts that can be used to generate targeted molecular weight compositions may be employed.
In at least one embodiment, the mixed catalyst system provides a polymer with a mix of beneficial properties as a result of a tailored combination of MWD and the CD. The ability to control the MWD and the CD of the system is typically crucial in determining the processability and strength of the resultant polymer.
These factors can be tailored by controlling the MWD, which, in turn, can be adjusted by changing the relative amount of the combination of pre-catalysts on the support. This may be regulated during the formation of the pre-catalysts, for instance, by supporting the two, or more, catalysts on a single support. In at least one embodiment, the relative amounts of the pre-catalysts can be adjusted by adding one of the components as trim to a catalyst mixture progressing into the reactor. Controlling the amount of catalyst addition can be achieved by using the feedback of polymer property data.
Altogether, certain embodiments provide a polymerization system, method, and catalyst system for producing polyethylene. The techniques include polymerizing ethylene in the presence of a catalyst system in a reactor to form the polyethylene, wherein the catalyst system has a first catalyst such as metallocene catalyst, and a second catalyst such as another metallocene catalyst or a non-metallocene catalyst. The reactor conditions and an amount of the second catalyst (or ratio of second catalyst to first catalyst) fed to the reactor may be adjusted to control MI and the density of the polyethylene based on a target MIR and a desired combination of MWD and CD. The reactor conditions adjusted may be operating temperature of the reactor, a comonomer concentration and/or hydrogen concentration in the polymerization mixture in the reactor, and the like. The reactant concentrations may be adjusted to meet a MI target and/or density target of the polyethylene, for example, at a given MIR range of the polyethylene. In examples, the MI of the polyethylene is in a range from 0.5 g/10 min to 1.5 g/10 min, and the density of the polyethylene is in a range from 0.916 g/cm3 to 0.93 g/cm3.
In at least one embodiment, the first catalyst includes the metallocene catalyst HfP and the second catalyst is the metallocene EtInd. Further, the catalyst system may be a common supported catalyst system. Furthermore, the second catalyst may be added as a trim catalyst to a slurry having the first catalyst fed the reactor. The first catalyst and the second catalyst may be impregnated on a single support. Furthermore, in certain embodiments, the first catalyst promotes polymerization of the ethylene into a high molecular weight portion of the polyethylene, and the second catalyst promotes polymerization of the ethylene into a low molecular-weight portion of the polyethylene. An amount of the second catalyst fed (or the catalyst trim ratio) to the polymerization reactor may be adjusted along with reactor conditions to control polyolefin properties at a given MIR, for instance.
Other embodiments provide for a method of producing polyethylene, including: polymerizing ethylene in the presence of a catalyst system in a reactor to form polyethylene, where the catalyst system comprises a first catalyst and a second catalyst; and adjusting reactor temperature, reactor hydrogen concentration, and/or an amount of the trim catalyst (first catalyst and/or second catalyst) fed to the reactor, to give a range of MIR of the polyethylene while maintaining density and MI of the polyethylene. An initial amount of the second catalyst may be co-deposited with first catalyst prior to being fed to the reactor. The adjusted amount of the second catalyst fed to the reactor may be the catalyst trim ratio. In certain embodiments, the first catalyst promotes polymerization of the ethylene into a high molecular-weight portion of the polyethylene, and wherein the second catalyst promotes polymerization of the ethylene into a low molecular-weight portion of the polyethylene. In particular embodiments, the reactor hydrogen concentration as a ratio of hydrogen to ethylene in the reactor is a control variable for MI, a ratio of comonomer (e.g., 1-hexene) to ethylene in the reactor is a primary control variable for the density, and the reactor temperature and the amount of the second catalyst fed to the reactor as a catalyst trim ratio are primary control variables of the MIR. In some instances, the MIR is in the range of 20 to 70 and the density is in the range of 0.912 g/cm3 to 0.940 g/cm3.
At least one embodiment provides for a method of producing polyethylene, including: polymerizing ethylene in the presence of a catalyst system in a reactor to form polyethylene, wherein the catalyst system comprises a first catalyst and a second catalyst, and adjusting reactor conditions and an amount of the trim catalyst fed to the reactor, to adjust the MI and/or MIR of polymer product.
Assorted catalyst systems and components may be used to generate the polymers. These are discussed in the sections to follow regarding the catalyst compounds that can be used in embodiments, including the first metallocene and the second metallocene catalysts, among others; generating catalyst slurries that may be used for implementing the techniques described; supports that may be used; catalyst activators that may be used; the catalyst component solutions that may be used to add additional catalysts in trim systems; gas-phase polymerization reactor with a trim feed system; use of the catalyst composition to control product properties; polymerization processes.
Metallocene catalyst compounds can include catalyst compounds having one or more Cp ligands (cyclopentadienyl and ligands isolobal to cyclopentadienyl) bound to at least one Group 3 to Group 12 metal atom, and one or more leaving group(s) bound to the at least one metal atom. As used herein, all references to the Periodic Table of the Elements and groups thereof is to the NEW NOTATION published in HAWLEYS CONDENSED CHEMICAL DICTIONARY. Thirteenth Edition, John Wiley & Sons, Inc., (1997) (reproduced there with permission from IUPAC), unless reference is made to the Previous IUPAC form noted with Roman numerals (also appearing in the same), or unless otherwise noted.
The Cp ligands are one or more rings or ring system(s), at least a portion of which includes π-bonded systems, such as cycloalkadienyl ligands and heterocyclic analogues. The ring(s) or ring system(s) typically include atoms selected from the group consisting of Groups 13 to 16 atoms, and, in a particular exemplary embodiment, the atoms that make up the Cp ligands are selected from the group consisting of carbon, nitrogen, oxygen, silicon, sulfur, phosphorous, germanium, boron, aluminum, and combinations thereof, where carbon makes up at least 50% of the ring members. In a more particular exemplary embodiment, the Cp ligand(s) are selected from the group consisting of substituted and unsubstituted cyclopentadienyl ligands and ligands isolobal to cyclopentadienyl, non-limiting examples of which include cyclopentadienyl, indenyl, fluorenyl and other structures. Further non-limiting examples of such ligands include cyclopentadienyl, cyclopentaphenanthreneyl, indenyl, benzindenyl, fluorenyl, octahydrofluorenyl, cyclooctatetraenyl, cyclopentacyclododecene, phenanthrindenyl, 3,4-benzofluorenyl, 9-phenylfluorenyl, 8-Hcyclopentalacenaphthylenyl, 7-H-dibenzofluorenyl, indeno 1.2-9anthrene, thiophenoindenyl, thiophenofluorenyl, hydrogenated versions thereof (e.g., 4,5,6,7-tetrahydroindenyl, or “H4 Ind”), substituted versions thereof (as discussed and described in more detail below), and heterocyclic versions thereof.
The metal atom “M” of the metallocene catalyst compound can be selected from the group consisting of Groups 3 through 12 atoms and lanthanide Group atoms in one exemplary embodiment; and selected from the group consisting of Groups 3 through 10 atoms in a more particular exemplary embodiment; and selected from the group consisting of Sc, Ti, Zr, Hf, V, Nb, Ta, Mn, Re, Fe, Ru, Os, Co. Rh, Ir, and Ni in yet a more particular exemplary embodiment; and selected from the group consisting of Groups 4, 5, and 6 atoms in yet a more particular exemplary embodiment; and Ti, Zr, Hf atoms in yet a more particular exemplary embodiment; and Zr in yet a more particular exemplary embodiment. The oxidation state of the metal atom “M” can range from 0 to +7 in one exemplary embodiment; and in a more particular exemplary embodiment, can be +1, +2, +3, +4, or +5; and in yet a more particular exemplary embodiment can be +2, +3 or +4. The groups bound to the metal atom “M” are such that the compounds described below in the formulas and structures are electrically neutral, unless otherwise indicated. The Cp ligand forms at least one chemical bond with the metal atom M to form the “metallocene catalyst compound.” The Cp ligands are distinct from the leaving groups bound to the catalyst compound in that they are not highly susceptible to substitution/abstraction reactions.
The one or more metallocene catalyst compounds can be represented by the structure (III):
CpACpBMXn (III),
in which M is as described above; each X is chemically bonded to M, each Cp group is chemically bonded to M and n is 0 or an integer from 1 to 4, and either 1 or 2 in a particular exemplary embodiment.
The ligands represented by CpA and CpB in structure (III) can be the same or different cyclopentadienyl ligands or ligands isolobal to cyclopentadienyl, either or both of which can contain heteroatoms and either or both of which can be substituted by a group R. In at least one specific embodiment, CpA and CpB are independently selected from the group consisting of cyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl, and substituted derivatives of each.
Independently, each CpA and CpB of structure (III) can be unsubstituted or substituted with any one or combination of substituent groups R. Non-limiting examples of substituent groups R as used in structure (III) as well as ring substituents in structures discussed and described below, include groups selected from the group consisting of hydrogen radicals, alkyls, alkenyls, alkynyls, cycloalkyls, aryls, acyls, aroyls, alkoxys, aryloxys, alkylthiols, dialkylamines, alkylamidos, alkoxycarbonyls, aryloxycarbonyls, carbomoyls, alkyl- and dialkyl-carbamoyls, acyloxys, acylaminos, aroylaminos, and combinations thereof. More particular non-limiting examples of alkyl substituents R associated with any of the catalyst structures of the present disclosure (e.g., formula (III)) include methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopentyl, cyclohexyl, benzyl, phenyl, methylphenyl, and tert-butylphenyl groups and the like, including all their isomers, for example, tertiary butyl, isopropyl, and the like. Other possible radicals include substituted alkyls and aryls such as, for example, fluoromethyl, fluroethyl, difluroethyl, iodopropyl, bromohexyl, chlorobenzyl, hydrocarbyl substituted organometalloid radicals including trimethylsilyl, trimethylgermyl, methyldiethylsilyl, and the like, and halocarbyl-substituted organometalloid radicals, including tris(trifluoromethyl)silyl, methylbis(difluoromethyl)silyl, bromomethyldimethylgermyl and the like; and disubstituted boron radicals including dimethylboron, for example; and disubstituted Group 15 radicals including dimethylamine, dimethylphosphine, diphenylamine, methylphenylphosphine, as well as Group 16 radicals including methoxy, ethoxy, propoxy, phenoxy, methylsulfide and ethylsulfide. Other substituent groups R include, but are not limited to, olefins such as olefinically unsaturated Substituents including vinyl-terminated ligands such as, for example, 3-butenyl, 2-propenyl, 5-hexenyl, and the like. In one exemplary embodiment, at least two R groups (two adjacent R groups in a particular exemplary embodiment) are joined to form a ring structure having from 3 to 30 atoms selected from the group consisting of carbon, nitrogen, oxygen, phosphorous, silicon, germanium, aluminum, boron, and combinations thereof. Also, a substituent group R Such as 1-butanyl can form a bonding association to the element M.
Each leaving group, or X, in the structure (III) (and X of the catalyst structures shown below) is independently selected from halogen, hydrides, C1 to C12 alkyls, C2 to C12 alkenyls, C6 to C12 aryls, C7 to C20 alkylaryls, C1 to C12 alkoxys, C6 to C16 aryloxys, C7 to C8 alkylaryloxys, C1 to C12 fluoroalkyls, C6 to C12 fluoroaryls, and C1 to C12 heteroatom containing hydrocarbons and substituted derivatives thereof, in a more particular exemplary embodiment; hydride, halogen ions, C1 to C6 alkyls, C2 to C6 alkenyls, C7 to C18 alkylaryls, C1 to C6 alkoxys, C6 to C14 aryloxys, C7 to C16 alkylaryloxys, C1 to C6 alkylcarboxylates, C1 to C6 fluorinated alkylcarboxylates, C6 to C12 arylcarboxylates, C7 to C18 alkylarylcarboxylates, C1 to C6 fluoroalkyls, C2 to C6 fluoroalkenyls, and C7 to C18 fluoroalkylaryls in yet a more particular exemplary embodiment; hydride, chloride, fluoride, methyl, phenyl, phenoxy, benzoxy, tosyl, fluoromethyls and fluorophenyls, in yet a more particular exemplary embodiment; C1 to C12 alkyls, C2 to C12 alkenyls, C6 to C12 aryls, C7 to C20 alkylaryls, substituted C1 to C12 alkyls, substituted C6 to C12 aryls, substituted C7 to C20 alkylaryls and C1 to C12 heteroatom-containing alkyls, C1 to C12 heteroatom-containing aryls, and C1 to C12 heteroatom-containing alkylaryls, in yet a more particular exemplary embodiment; chloride, fluoride, C1 to C6 alkyls, C2 to C6 alkenyls, C7 to C18 alkylaryls, halogenated C1 to C6 alkyls, halogenated C2 to C6 alkenyls, and halogenated C7 to C18 alkylaryls, in yet a more particular exemplary embodiment; chloride, methyl, ethyl, propyl, phenyl, methylphenyl, dimethylphenyl, trimethylphenyl, fluoromethyls (mono-, di- and trifluoromethyls) and fluorophenyls (mono-, di-, tri-, tetra- and pentafluorophenyls), in yet a more particular exemplary embodiment.
Other non-limiting examples of X groups include amides, amines, phosphines, ethers, carboxylates, dienes, hydrocarbon radicals having from 1 to 20 carbon atoms, fluorinated hydrocarbon radicals (e.g., —C6F5 (pentafluorophenyl)), fluorinated alkylcarboxylates (e.g., CF3C(O)O—), hydrides, halogen ions and combinations thereof. Other examples of X ligands include alkyl groups such as cyclobutyl, cyclohexyl, methyl, heptyl, tolyl, trifluorom ethyl, tetramethylene, pentamethylene, methylidene, methyoxy, ethyoxy, propoxy, phenoxy, bis(N-methylanilide), dimethylamide, dimethylphosphide radicals and the like. In one exemplary embodiment, two or more X's form a part of a fused ring or ring system.
In at least one specific embodiment, X can be a leaving group selected from the group consisting of chloride ions, bromide ions, C1 to C10 alkyls, and C2 to C12 alkenyls, carboxylates, acetylacetonates, and alkoxides.
The metallocene catalyst compound includes those of structure (III) where CpA and CpB are bridged to each other by at least one bridging group, (A) such that the structure is represented by structure (IV):
CpA(A)CpBMXn (IV).
These bridged compounds represented by structure (IV) are known as “bridged metallocenes.” The elements CpA, CpB, M, X and n in structure (IV) are as defined above for structure (III); where each Cp ligand is chemically bonded to M, and (A) is chemically bonded to each Cp. The bridging group (A) can include divalent hydrocarbon groups containing at least one Group 13 to 16 atom, such as, but not limited to, at least one of a carbon, oxygen, nitrogen, silicon, aluminum, boron, germanium, tin atom, and combinations thereof; where the heteroatom can also be C1 to C12 alkyl, or aryl substituted to satisfy neutral valency. In at least one specific embodiment, the bridging group (A) can also include substituent groups R as defined above (for structure (III)) including halogen radicals and iron. In at least one specific embodiment, the bridging group (A) can be represented by C1 to C6 alkylenes, substituted C1 to C6 alkylenes, oxygen, sulfur, R2C═R2Si, —Si(R′)2Si(OR′)2—, R′2Ge—, and RP═, where “═” represents two chemical bonds, R is independently selected from hydride, hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, hydrocarbyl-substituted organometalloid, halocarbyl-substituted organometalloid, disubstituted boron, disubstituted Group 15 atoms, substituted Group 16 atoms, and halogen radical; and where two or more R′ can be joined to form a ring or ring system. In at least one specific embodiment, the bridged metallocene catalyst compound of structure (IV) includes two or more bridging groups (A). In one or more embodiments, (A) can be a divalent bridging group bound to both CpA and CpB selected from divalent C1 to C20 hydrocarbyls and C1 to C20 heteroatom containing hydrocarbonyls, where the heteroatom containing hydrocarbonyls include from one to three heteroatoms.
The bridging group (A) can include methylene, ethylene, ethylidene, propylidene, isopropylidene, diphenylmethylene, 1,2-dimethylethylene, 1,2-diphenylethylene, 1,1,2,2-tetramethylethylene, dimethylsilyl, diethylsilyl, methyl-ethylsilyl, trifluoromethylbutylsilyl, bis(trifluoromethyl)silyl, di(n-butyl)silyl, di(n-propyl)silyl, di(i-propyl)silyl, di(n-hexyl)silyl, dicyclohexylsilyl, diphenylsilyl cyclohexylphenylsilyl, t-butylcyclohexylsilyl, di(t-butylphenyl) silyl, di(p-tolyl)silyl and the corresponding moieties where the Si atom is replaced by a Ge or a C atom; as well as dimethylsilyl, diethylsilyl, dimethylgermyl and diethylgermyl.
The bridging group (A) can also be cyclic, having, for example, 4 to 10 ring members; in a more particular exemplary embodiment, bridging group (A) can have 5 to 7 ring members. The ring members can be selected from the elements mentioned above, and, in a particular embodiment, can be selected from one or more of B, C, Si, Ge, N, and O. Non-limiting examples of ring structures which can be present as, or as part of the bridging moiety are cyclobutylidene, cyclopentylidene, cyclohexylidene, cycloheptylidene, cyclooctylidene and the corresponding rings where one or two carbon atoms are replaced by at least one of Si, Ge, N and O. In one or more embodiments, one or two carbon atoms can be replaced by at least one of Si and Ge. The bonding arrangement between the ring and the Cp groups can be cis-, trans-, or a combination thereof.
The cyclic bridging groups (A) can be saturated or unsaturated and/or can carry one or more substituents and/or can be fused to one or more other ring structures. If present, the one or more substituents can be, in at least one specific embodiment, selected from the group consisting of hydrocarbyl (e.g., alkyl, such as methyl) and halogen (e.g., F, Cl). The one or more Cp groups to which the above cyclic bridging moieties can optionally be fused can be saturated or unsaturated, and are selected from the group consisting of those having 4 to 10, more particularly 5, 6, or 7 ring members (selected from the group consisting of C, N, O, and S in a particular exemplary embodiment) such as, for example, cyclopentyl, cyclohexyl and phenyl. Moreover, these ring structures can themselves be fused such as, for example, in the case of a naphthyl group. Moreover, these (optionally fused) ring structures can carry one or more substituents. Illustrative, non-limiting examples of these substituents are hydrocarbyl (particularly alkyl) groups and halogen atoms. The ligands CpA and CpB of structure (III) and (IV) can be different from each other. The ligands CpA and CpB of structure (III) and (IV) can be the same. The metallocene catalyst compound can include bridged mono ligand metallocene compounds (e.g., mono cyclopentadienyl catalyst components).
It is considered that the metallocene catalyst components discussed and described above include their structural or optical or enantiomeric isomers (racemic mixture), and, in one exemplary embodiment, can be a pure enantiomer. As used herein, a single, bridged, asymmetrically substituted metallocene catalyst compound having a racemic and/or meso-isomer does not, itself, constitute at least two different bridged, metallocene catalyst components.
The amount of the transition metal component of the one or more metallocene catalyst compounds in the catalyst system can range from 0.2 wt %, 0.3 wt %, 0.5 wt %, or 0.7 wt % to 1 wt %, 2 wt %, 2.5 wt %, 3 wt %, 3.5 wt %, or 4 wt %, based on the total weight of the catalyst system wt %
The metallocene catalyst compounds can include any suitable combination. For example, the metallocene catalyst compound can include, but is not limited to, bis(n-butylcyclopentadienyl) zirconium (CH3)2, bis(n-butylcyclopentadienyl)ZrCl2, bis(n-butylcyclopentadienyl)ZrCl2, (n-propylcyclopentadienyl, tetramethylcyclopentadienyl)ZrCl2, or any combinations thereof. Other metallocene catalyst compounds are contemplated.
Although the catalyst compounds may be written or shown with methyl-, chloro-, or phenyl-leaving groups attached to the central metal, it can be understood that these groups may be different. For example, each of these ligands may independently be a benzyl group (Bn), a methyl group (Me), a chloro group (Cl), a fluoro group (F), or any number of other groups, including organic groups, or heteroatom groups. Further, these ligands will change during the reaction, as a pre-catalyst is converted to the active catalyst for the reaction.
The catalyst system may include a catalyst component in a slurry, which may have an initial catalyst compound, and an added solution catalyst component that is added to the slurry. Generally, the first metallocene catalyst and/or second metallocene catalyst will be supported in the initial slurry, depending on solubility. However, in at least one embodiment, the initial catalyst component slurry may have no catalysts. In this case, two or more solution catalysts may be added to the slurry to cause each to be supported.
Any number of combinations of catalyst components may be used in embodiments. For example, the catalyst component slurry can include an activator and a support, or a supported activator. Further, the slurry can include a catalyst compound in addition to the activator and the support. As noted, the catalyst compound in the slurry may be supported.
The slurry may include one or more activators and supports, and one or more catalyst compounds. For example, the slurry may include two or more activators (such as alumoxane and a modified alumoxane) and a catalyst compound, or the slurry may include a supported activator and more than one catalyst compounds. In at least one embodiment, the slurry includes a support, an activator, and two catalyst compounds. In another embodiment the slurry includes a support, an activator and two different catalyst compounds, which may be added to the slurry separately or in combination. The slurry, containing silica and alumoxane, may be contacted with a catalyst compound, allowed to react, and thereafter the slurry is contacted with another catalyst compound, for example, in a trim system.
The molar ratio of metal in the activator to metal in the catalyst compound in the slurry may be 1000:1 to 0.5:1, 300:1 to 1:1, 100:1 to 1:1, or 150:1 to 1:1. The slurry can include a support material which may be any inert particulate carrier material known in the art, including, but not limited to, silica, fumed silica, alumina, clay, talc or other support materials such as disclosed above. In at least one embodiment, the slurry contains silica and an activator, such as methyl aluminoxane (“MAO”), modified methyl aluminoxane (“MMAO), as discussed further below.
One or more diluents or carriers can be used to facilitate the combination of any two or more components of the catalyst system in the slurry or in the trim catalyst solution. For example, the single site catalyst compound and the activator can be combined together in the presence of toluene or another non-reactive hydrocarbon or hydrocarbon mixture to provide the catalyst mixture. In addition to toluene, other suitable diluents can include, but are not limited to, ethylbenzene, xylene, pentane, hexane, heptane, octane, other hydrocarbons, or any combination thereof. The support, either dry or mixed with toluene can then be added to the catalyst mixture or the catalyst/activator mixture can be added to the support.
The diluent can be or include mineral oil. Mineral oil can have a density of from 0.85 g/cm3 to 0.9 g/cm3 at 25° C. according to ASTM D4052, such as from 0.86 g/cm3 to 0.88 g/cm3. Mineral oil can have a kinematic viscosity at 25° C. of from 150 cSt to 200 cSt according to ASTM D341, such as from 160 cSt to 190 cSt, such as about 170 cSt. Mineral oil can have an average molecular weight of from 400 g/mol to 600 g/mol according to ASTM D2502, such as from 450 g/mol to 550 g/mol, such as about 500 g/mol. In at least one embodiment, a mineral oil is HYDROBRITE® 380 PO White Mineral Oil (“HB380”) from Sonneborn, LLC.
The diluent can further include a wax, which can provide increased viscosity to a slurry (such as a mineral oil slurry). A wax is a food grade petrolatum also known as petroleum jelly. A wax can be a paraffin wax. Paraffin waxes include SONO JELL® paraffin waxes, such as SONO JELL® 4 and SONO JELL® 9 from Sonneborn, LLC. In at least one embodiment, a slurry has 5 wt % or greater of wax, such as 10 wt % or greater, such as 25 wt % or greater, such as 40 wt % or greater, such as 50 wt % or greater, such as 60 wt % or greater, such as 70 wt % or greater. For example, a mineral oil slurry can have 70 wt % mineral oil, 10 wt % wax, and 20 wt % supported catalyst(s) (e.g., supported dual catalysts). It has been discovered that the increased viscosity provided by a wax in a slurry, such as a mineral oil slurry, provides reduced settling of supported catalyst(s) in a vessel or catalyst pot. It has further been discovered that using an increased viscosity mineral oil slurry does not inhibit trim efficiency. In at least one embodiment, a wax has a density of from about 0.7 g/cm3 (at 100° C.) to about 0.95 g/cm3 (at 100° C.), such as from about 0.75 g/cm3 (at 100° C.) to about 0.87 g/cm3 (at 100° C.). A wax can have a kinematic viscosity of from 5 mm2/s (at 100° C.) to about 30 mm2/s (at 100° C.). A wax can have a boiling point of about 200° C. or greater, such as about 225° C. or greater, such as about 250° C. or greater. A wax can have a melting of from about 25° C. to about 100° C., such as from about 35° C. to about 80° C.
As used herein, “trim efficiency” is the amount of trim catalyst that contributes to polymerization relative to the amount of trim metallocene fed. Trim efficiency can be calculated for catalyst systems that exhibit a relationship between MIR and catalyst ratio. As a non-limiting example: the polymer formed by a catalyst ratio of 90:10 can have an MIR of 23, a polymer formed by a catalyst ratio of 80:20 can have an MIR of 37, and a polymer formed by a catalyst ratio of 70:30 can have an MIR of 50. Using trim with the second catalyst, the catalyst ratio can be adjusted from 90:10 to a targeted 70:30 by using trim, where Xf is the amount of trim catalyst fed to adjust the catalyst ratio from 90:10 to 70:30. The resultant polymer from trimming Xf has an MIR that is below the expected MIR for 100% efficient trim, and the catalyst ratio can be determined from the trim baseline. The amount of trim required to adjust the catalyst ratio from 90:10 to the ratio determined by the polymer product's MIR is Xe. Trim efficiency is then calculated as E=Xe/Xf. It should be noted that trim efficiency as calculated above is not bounded to 100% due to the possibility of displacement, where the trim (e.g., second) catalyst can displace some supported first catalyst in the case of high trim flows. In at least one embodiment, the trim efficiency of a trim process of the present disclosure has a value of 20% or greater, such as 50% or greater, such as 60% or greater, such as 70% or greater, such as 80% or greater, such as 90% or greater, such as from 20% to 99%, such as from 50% to 99%, such as from 60% to 80%.
The catalyst is not limited to a slurry arrangement, as a mixed catalyst system may be made on a support and dried. The dried catalyst system can then be fed to the reactor through a dry feed system.
As used herein, the terms “support” and “carrier” are used interchangeably and refer to any support material, including a porous support material, such as talc, inorganic oxides, and inorganic chlorides. The one or more single site catalyst compounds of the slurry can be supported on the same or separate supports together with the activator, or the activator can be used in an unsupported form, or can be deposited on a support different from the single site catalyst compounds, or any combination thereof. This may be accomplished by any technique commonly used in the art. There are various other suitable methods for supporting a single site catalyst compound. For example, the single site catalyst compound can contain a polymer bound ligand. The single site catalyst compounds of the slurry can be spray dried. The support used with the single site catalyst compound can be functionalized.
The support can be or include one or more inorganic oxides, for example, of Group 2, 3, 4, 5, 13, or 14 elements. The inorganic oxide can include, but is not limited to silica, alumina, titania, zirconia, boria, zinc oxide, magnesia, or any combination thereof. Illustrative combinations of inorganic oxides can include, but are not limited to, alumina-silica, silica-titania, alumina-silica-titania, alumina-zirconia, alumina-titania, and the like. The support can be or include silica, alumina, or a combination thereof. In at least one embodiment described herein, the support is silica.
Suitable commercially available silica supports can include, but are not limited to, ES757, ES70, and ES70W available from PQ Corporation. Suitable commercially available silica-alumina supports can include, but are not limited to, SIRAL® 1, SIRAL® 5, SIRAL® 10, SIRAL® 20, SIRAL® 28M, SIRAL® 30, and SIRAL® 40, available from SASOL®. Generally, catalyst supports comprising silica gels with activators, such as methylaluminoxanes (MAOs), are used in the trim systems described, since these supports may function better for co-supporting solution carried catalysts.
In at least one embodiment, the support material comprises a support material treated with an electron-withdrawing anion. The support material can be silica, alumina, silica-alumina, silica-zirconia, alumina-zirconia, aluminum phosphate, heteropolytungstates, titania, magnesia, boria, zinc oxide, mixed oxides thereof, or mixtures thereof; and the electron-withdrawing anion is selected from fluoride, chloride, bromide, phosphate, triflate, bisulfate, sulfate, or any combination thereof.
The electron-withdrawing component used to treat the support material can be any component that increases the Lewis or Brønsted acidity of the support material upon treatment (as compared to the support material that is not treated with at least one electron-withdrawing anion). In at least one embodiment, the electron-withdrawing component is an electron-withdrawing anion derived from a salt, an acid, or other compound, such as a volatile organic compound, that serves as a source or precursor for that anion. Electron-withdrawing anions can be sulfate, bisulfate, fluoride, chloride, bromide, iodide, fluorosulfate, fluoroborate, phosphate, fluorophosphate, trifluoroacetate, triflate, fluorozirconate, fluorotitanate, phospho-tungstate, or mixtures thereof, or combinations thereof. An electron-withdrawing anion can be fluoride, chloride, bromide, phosphate, triflate, bisulfate, or sulfate, or any combination thereof, at least one embodiment of this disclosure. In at least one embodiment, the electron-withdrawing anion is sulfate, bisulfate, fluoride, chloride, bromide, iodide, fluorosulfate, fluoroborate, phosphate, fluorophosphate, trifluoroacetate, triflate, fluorozirconate, fluorotitanate, or combinations thereof.
Thus, for example, the support material suitable for use in the catalyst systems of the present disclosure can be one or more of fluorided alumina, chlorided alumina, bromided alumina, sulfated alumina, fluorided silica-alumina, chlorided silica-alumina, bromided silica-alumina, sulfated silica-alumina, fluorided silica-zirconia, chlorided silica-zirconia, bromided silica-zirconia, sulfated silica-zirconia, fluorided silica-titania, fluorided silica-coated alumina, sulfated silica-coated alumina, phosphated silica-coated alumina, or combinations thereof. In at least one embodiment, the activator-support can be, or can comprise, fluorided alumina, sulfated alumina, fluorided silica-alumina, sulfated silica-alumina, fluorided silica-coated alumina, sulfated silica-coated alumina, phosphated silica-coated alumina, or combinations thereof. In another embodiment, the support material includes alumina treated with hexafluorotitanic acid, silica-coated alumina treated with hexafluorotitanic acid, silica-alumina treated with hexafluorozirconic acid, silica-alumina treated with trifluoroacetic acid, fluorided boria-alumina, silica treated with tetrafluoroboric acid, alumina treated with tetrafluoroboric acid, alumina treated with hexafluorophosphoric acid, or combinations thereof. Further, any of these activator-supports optionally can be treated with a metal ion.
Nonlimiting examples of cations suitable for use in the present disclosure in the salt of the electron-withdrawing anion include ammonium, trialkyl ammonium, tetraalkyl ammonium, tetraalkyl phosphonium, H+, [H(OEt2)2]+, or combinations thereof.
Further, combinations of one or more different electron-withdrawing anions, in varying proportions, can be used to tailor the specific acidity of the support material to a desired level. Combinations of electron-withdrawing components can be contacted with the support material simultaneously or individually, and in any order that provides a desired chemically-treated support material acidity. For example, in at least one embodiment, two or more electron-withdrawing anion source compounds in two or more separate contacting steps.
In at least one embodiment of the present disclosure, one example of a process by which a chemically-treated support material is prepared is as follows: a selected support material, or combination of support materials, can be contacted with a first electron-withdrawing anion source compound to form a first mixture; such first mixture can be calcined and then contacted with a second electron-withdrawing anion source compound to form a second mixture; the second mixture can then be calcined to form a treated support material. In such a process, the first and second electron-withdrawing anion source compounds can be either the same or different compounds.
The method by which the oxide is contacted with the electron-withdrawing component, typically a salt or an acid of an electron-withdrawing anion, can include gelling, co-gelling, impregnation of one compound onto another, or combinations thereof. Following a contacting method, the contacted mixture of the support material, electron-withdrawing anion, and optional metal ion, can be calcined.
According to another embodiment of the present disclosure, the support material can be treated by a process comprising: (i) contacting a support material with a first electron-withdrawing anion source compound to form a first mixture; (ii) calcining the first mixture to produce a calcined first mixture; (iii) contacting the calcined first mixture with a second electron-withdrawing anion source compound to form a second mixture; and (iv) calcining the second mixture to form the treated support material.
As used herein, the term “activator” may refer to any compound or combination of compounds, supported, or unsupported, which can activate a single site catalyst compound or component. Such as by creating a cationic species of the catalyst component. For example, this can include the abstraction of at least one leaving group (the ‘X’ group in the single site catalyst compounds described herein) from the metal center of the single site catalyst compound/component. The activator may also be referred to as a “co-catalyst’. For example, the activator can include a Lewis acid or a non-coordinating ionic activator or ionizing activator, or any other compound including Lewis bases, aluminum alkyls, and/or conventional-type co-catalysts. In addition to methylaluminoxane (“MAO”) and modified methylaluminoxane (“MMAO”) mentioned above, illustrative activators can include, but are not limited to, aluminoxane or modified aluminoxane, and/or ionizing compounds, neutral or ionic, such as tri (n-butyl)ammonium tetrakis(pentafluorophenyl) boron, a trisperfluorophenyl boron metalloid precursor, a trisperfluoronaphthyl boron metalloid precursor, or any combinations thereof.
Aluminoxanes can be described as oligomeric aluminum compounds having Al(R)—O— subunits, where R is an alkyl group. Examples of aluminoxanes include, but are not limited to, methylaluminoxane (“MAO”), modified methylaluminoxane (“MMAO”), ethylaluminoxane, isobutylaluminoxane, or a combination thereof. Aluminoxanes can be produced by the hydrolysis of the respective trialkylaluminum compound. MMAO can be produced by the hydrolysis of trimethylaluminum and a higher trialkylaluminum, such as triisobutylaluminum. MMAOs are generally more soluble in aliphatic solvents and more stable during storage. There are a variety of methods for preparing aluminoxane and modified aluminoxanes.
As noted above, one or more organo-aluminum compounds such as one or more alkylaluminum compounds can be used in conjunction with the aluminoxanes. For example, alkylaluminum species that may be used are diethylaluminum ethoxide, diethylaluminum chloride, and/or disobutylaluminum hydride. Examples of trialkylaluminum compounds include, but are not limited to, trimethylaluminum, triethylaluminum (“TEAL”), triisobutylaluminum “TiBAl”), tri-n-hexylaluminum, tri-n-octylaluminum, tripropylaluminum, tributylaluminum, and the like.
The catalyst component solution may include only catalyst compound(s), such as a metallocene, or may include an activator. In at least one embodiment, the catalyst compound(s) in the catalyst component solution is unsupported. The catalyst solution used in the trim process can be prepared by dissolving the catalyst compound and optional activators in a liquid solvent. The liquid solvent may be an alkane, such as a C5 to C30 alkane, or a C5 to C10 alkane. Cyclic alkanes such as cyclohexane and aromatic compounds such as toluene may also be used. Mineral oil may be used as a solvent alternatively or in addition to other alkanes such as a C5 to C30 alkane. Mineral oil can have a density of from 0.85 g/cm3 to 0.9 g/cm3 at 25° C. according to ASTM D4052, such as from 0.86 g/cm3 to 0.88 g/cm3. Mineral oil can have a kinematic viscosity at 25° C. of from 150 cSt to 200 cSt according to ASTM D341, such as from 160 cSt to 190 cSt, such as about 170 cSt. Mineral oil can have an average molecular weight of from 400 g/mol to 600 g/mol according to ASTM D2502, such as from 450 g/mol to 550 g/mol, such as about 500 g/mol. In at least one embodiment, a mineral oil is HYDROBRITE® 380 PO White Mineral Oil (“HB380”) from Sonneborn, LLC.
The solution employed should be liquid under the conditions of polymerization and relatively inert. In at least one embodiment, the liquid utilized in the catalyst compound solution is different from the diluent used in the catalyst component slurry. In another embodiment, the liquid utilized in the catalyst compound solution is the same as the diluent used in the catalyst component solution.
If the catalyst solution includes both activator and catalyst compound, the ratio of metal in the activator to metal in the catalyst compound in the solution may be 1000:1 to 0.5:1, 300:1 to 1:1, or 150:1 to 1:1. In various embodiments, the activator and catalyst compound are present in the solution at up to about 90 wt %, at up to about 50 wt %, at up to about 20 wt %, such as at up to about 10 wt %, at up to about 5 wt %, at less than 1 wt %, or between 100 ppm and 1 wt %, based upon the weight of the solvent and the activator or catalyst compound.
The one or more activators used in a catalyst component solution of the present disclosure can be the same or different as the one or more activators used in a catalyst slurry composition.
The catalyst component solution can include any one of the catalyst compound(s) of the present disclosure. As the catalyst is dissolved in the solution, a higher solubility is desirable. Accordingly, the catalyst compound in the catalyst component solution may often include a metallocene, which may have higher solubility than other catalysts.
In the polymerization process, described below, any of the above described catalyst component containing solutions may be combined with any of the catalyst component containing slurry/slurries described above. In addition, more than one catalyst component solution may be utilized.
In gas-phase polyethylene production processes, it may be desirable to use one or more static control agents to aid in regulating static levels in the reactor. As used herein, a static control agent is a chemical composition which, when introduced into a fluidized bed reactor, may influence or drive the static charge (negatively, positively, or to zero) in the fluidized bed. The specific static control agent used may depend upon the nature of the static charge, and the choice of static control agent may vary dependent upon the polymer being produced and the single site catalyst compounds being used.
Control agents such as aluminum stearate may be employed. The static control agent used may be selected for its ability to receive the static charge in the fluidized bed without adversely affecting productivity. Other suitable static control agents may also include aluminum distearate, ethoxylated amines, and anti-static compositions such as those provided by Innospec Inc. under the trade name OCTASTAT. For example, OCTASTAT 2000 is a mixture of a polysulfone copolymer, a polymeric polyamine, and oil soluble sulfonic acid.
Any of the mentioned control agents may be employed either alone or in combination as a control agent. For example, the carboxylate metal salt may be combined with an amine containing control agent (e.g., a carboxylate metal salt with any family member belonging to the KEMAMINE® (available from Crompton Corporation) or ATMER® (available from ICI Americas Inc) family of products).
Other useful continuity additives include ethyleneimine additives useful in embodiments disclosed herein may include polyethyleneimines having the following general formula: —(CH2—CH2—NH)n-, where n may be from about 10 to about 10,000. The polyethyleneimines may be linear, branched, or hyper branched (e.g., forming dendritic or arborescent polymer structures). They can be a homopolymer or copolymer of ethyleneimine or mixtures thereof (referred to as polyethyleneimine(s) hereafter). Although linear polymers represented by the chemical formula —(CH2—CH2—NH)n- may be used as the polyethyleneimine, materials having primary, secondary, and tertiary branches can also be used. Commercial polyethyleneimine can be a compound having branches of the ethyleneimine polymer.
In at least one embodiment, a slurry of the present disclosure has a % solids content of from 1 wt % to 40 wt %, such as from 15 wt % to 37.5 wt %, such as from 20 wt % to 37.5 wt %, such as from 30 wt % to 37.5 wt %, such as from 35 wt % to 37.5 wt %.
Paraffin waxes can include SONO JELL® paraffin waxes, such as SONO JELL® 4 and SONO JELL® 9 from Sonneborn, LLC. SONO JELL® paraffin waxes are compositions that typically contain 10 wt % or more of wax and up to 90 wt % of mineral oil. For example, a SONO JELL® paraffin wax can be 20 wt % wax and 80 wt % mineral oil. In at least one embodiment, a mineral oil slurry has 5 wt % or greater of wax, such as 10 wt % or greater, such as 25 wt % or greater, such as 40 wt % or greater, such as 50 wt % or greater, such as 60 wt % or greater, such as 70 wt % or greater. For example, a mineral oil slurry can have 70 wt % mineral oil, 10 wt % wax, and 20 wt % supported dual catalyst. It has been discovered that the increased viscosity provided by including a wax in the mineral oil slurry provides reduced settling of supported dual catalyst in a vessel or catalyst pot. It has further been discovered that using an increased viscosity mineral oil slurry does not inhibit trim efficiency.
Cat pot 102 is an agitated holding tank designed to keep the solids concentration homogenous. In at least one embodiment, cat pot 102 is maintained at an elevated temperature, such as from 30° C. to 75° C., such as from 40° C. to 45° C., for example about 43° C. or about 60° C. Elevated temperature can be obtained by electrically heat tracing cat pot 102 using, for example, a heating blanket. Cat pot 102 that is maintained at an elevated temperature can provide a wax-containing mineral oil slurry that has slurry stability for 6 days or more, e.g. a settling rate of supported catalyst of 40% or less after 6 days. Furthermore, it has been discovered that maintaining cat pot 102 at an elevated temperature can also reduce or eliminate foaming, in particular when a wax is present in the mineral oil slurry. Without being bound by theory, a synergy provided by increased viscosity of the slurry provided by the wax and decreased viscosity provided by elevated temperature of the slurry can provide the reduced or eliminated foam formation in a cat pot vessel. Maintaining cat pot 102 at an elevated temperature can further reduce or eliminate solid residue formation on vessel walls which could otherwise slide off of the walls and cause plugging in downstream delivery lines. In at least one embodiment, cat pot 102 has a volume of from about 300 gallons to 2,000 gallons, such as from 400 gallons to 1,500 gallons, such as from 500 gallons to 1,000 gallons, such as from 500 gallons to 800 gallons, for example about 500 gallons.
In at least one embodiment, cat pot 102 is also maintained at pressure of 25 psig or greater, such as from 25 psig to 75 psig, such as from 30 psig to 60 psig, for example about 50 psig. Conventional trim processes involve slurry cylinders rolled at 25 psig, and foam is created when transferred down in pressure to the slurry vessel. It has been discovered that operating a slurry vessel (e.g., cat pot 102) at higher pressures can reduce or prevent foam.
In at least one embodiment, piping 130 and piping 140 of gas-phase reactor system 100 is maintained at an elevated temperature, such as from 30° C. to 75° C., such as from 40° C. to 45° C., for example about 43° C. or about 60° C. Elevated temperature can be obtained by electrically heat tracing piping 130 and or piping 140 using, for example, a heating blanket. Maintaining piping 130 and or piping 140 at an elevated temperature can provide the same or similar benefits as described for an elevated temperature of cat pot 102.
A catalyst component solution, prepared by mixing a solvent and at least one catalyst compound and/or activator, is placed in another vessel, such as a trim pot 104. Trim pot 104 can have a volume of from about 100 gallons to 2,000 gallons, such as from 100 gallons to 1,500 gallons, such as from 200 gallons to 1,000 gallons, such as from 200 gallons to 500 gallons, for example about 300 gallons. Trim pot 104 can be maintained at an elevated temperature, such as from 30° C. to 75° C., such as from 40° C. to 45° C., for example about 43° C. or about 60° C. Elevated temperature can be obtained by electrically heat tracing trim pot 104 using, for example, a heating blanket. Maintaining trim pot 104 at an elevated temperature can provide reduced or eliminated foaming in piping 130 and or piping 140 when the catalyst component slurry from cat pot 102 is combined in-line (also referred to herein as “on-line”) with the catalyst component solution from trim pot 104.
It has been discovered that if the catalyst component slurry includes a wax, then it is advantageous that a diluent of the catalyst component solution have a viscosity that is greater than the viscosity of an alkane solvent, such as isopentane (iC5) or isohexane (iC6). Using iC5 or iC6 as a diluent in a trim pot can promote catalyst settling and static mixer plugging. Accordingly, in at least one embodiment, the catalyst component slurry of cat pot 102 includes a wax, as described above, and the catalyst component solution of trim pot 104 includes a diluent that is mineral oil. It has been discovered that trim efficiency is maintained or improved using wax in the catalyst component slurry and mineral oil in the catalyst component solution. Furthermore, use of wax and mineral oil reduces or eliminates the amount of iC5 and iC6 used in a trim process, which can reduce or eliminate emissions of volatile material (such as iC5 and iC6). Mineral oil can have a density of from 0.85 g/cm3 to 0.9 g/cm3 at 25° C. according to ASTM D4052, such as from 0.86 g/cm3 to 0.88 g/cm3. Mineral oil can have a kinematic viscosity at 40° C. of from 70 cSt to 240 cSt according to ASTM D445, such as from 160 cSt to 190 cSt, such as about 170 cSt. Mineral oil can have an average molecular weight of from 400 g/mol to 600 g/mol according to ASTM D2502, such as from 450 g/mol to 550 g/mol, such as about 500 g/mol. In at least one embodiment, a mineral oil is HB380 from Sonneborn, LLC or HydroBrite 1000 white mineral oil.
The catalyst component slurry can then be combined in-line with the catalyst component solution to form a final catalyst composition. A nucleating agent 106, such as silica, alumina, fumed silica or any other particulate matter may be added to the slurry and/or the solution in-line or in the vessels 102 or 104. Similarly, additional activators or catalyst compounds may be added in-line. For example, a second catalyst slurry (catalyst component solution) that includes a different catalyst may be introduced from a second cat pot (which may include wax and mineral oil). The two catalyst slurries may be used as the catalyst system with or without the addition of a solution catalyst from the trim pot.
The catalyst component slurry and solution can be mixed in-line. For example, the solution and slurry may be mixed by utilizing a static mixer 108 or an agitating vessel. The mixing of the catalyst component slurry and the catalyst component solution should be long enough to allow the catalyst compound in the catalyst component solution to disperse in the catalyst component slurry such that the catalyst component, originally in the solution, migrates to the supported activator originally present in the slurry. The combination forms a uniform dispersion of catalyst compounds on the supported activator forming the catalyst composition. The length of time that the slurry and the solution are contacted is typically up to about 220 minutes, such as about 1 to about 60 minutes, about 5 to about 40 minutes, or about 10 to about 30 minutes.
In at least one embodiment, static mixer 108 of gas-phase reactor system 100 is maintained at an elevated temperature, such as from 30° C. to 75° C., such as from 40° C. to 45° C., for example about 43° C. or about 60° C. Elevated temperature can be obtained by electrically heat tracing static mixer 108 using, for example, a heating blanket. Maintaining static mixer 108 at an elevated temperature can provide reduced or eliminated foaming in static mixer 108 and can promote mixing of the catalyst component slurry and catalyst solution (as compared to lower temperatures) which reduces run times in the static mixer and for the overall polymerization process.
When combining the catalysts, the activator and the optional support or additional co-catalysts in the hydrocarbon solvents immediately prior to a polymerization reactor, the combination can yield a new polymerization catalyst in less than 1 h, less than 30 min, or less than 15 min Shorter times are more effective, as the new catalyst is ready before being introduced into the reactor, which can provide faster flow rates.
In another embodiment, an aluminum alkyl, an ethoxylated aluminum alkyl, an aluminoxane, an anti-static agent or a borate activator, such as a C1 to C15 alkyl aluminum (for example tri-isobutyl aluminum, trimethyl aluminum or the like), a C1 to C15 ethoxylated alkyl aluminum or methyl aluminoxane, ethyl aluminoxane, isobutylaluminoxane, modified aluminoxane or the like are added to the mixture of the slurry and the solution in line. The alkyls, antistatic agents, borate activators and/or aluminoxanes may be added from an alkyl vessel 110 directly to the combination of the solution and the slurry, or may be added via an additional alkane (such as hexane, heptane, and or octane) carrier stream, for example, from a carrier vessel 112. The additional alkyls, antistatic agents, borate activators and/or aluminoxanes may be present at up to 500 ppm, at 1 to 300 ppm, at 10 ppm to 300 ppm, or at 10 to 100 ppm. A carrier gas 114 such as nitrogen, argon, ethane, propane, and the like, may be added in-line to the mixture of the slurry and the solution. Typically the carrier gas may be added at the rate of about 1 to about 100 lb/hr (0.4 to 45 kg/hr), or about 1 to about 50 lb/hr (5 to 23 kg/hr), or about 1 to about 25 lb/hr (0.4 to 11 kg/hr).
In at least one embodiment, a liquid carrier stream is introduced into the combination of the solution and slurry. The mixture of the solution, the slurry and the liquid carrier stream may pass through a mixer or length of tube for mixing before being contacted with a gaseous carrier stream. Similarly, a comonomer 116, such as hexene, another alpha-olefin, or diolefin, may be added in-line to the mixture of the slurry and the solution.
In at least one embodiment, a gas stream 126, such as cycle gas, or re-cycle gas 124, monomer, nitrogen, or other materials is introduced into an injection nozzle 300 having a support tube 128 that surrounds an injection tube 120. The slurry/solution mixture is passed through the injection tube 120 to a reactor 122. In at least one embodiment, the injection tube may aerosolize the slurry/solution mixture. Any number of suitable tubing sizes and configurations may be used to aerosolize and/or inject the slurry/solution mixture.
In at least one embodiment, nozzle 300 is an “effervescent” nozzle. It has been discovered that use of an effervescent nozzle can provide a 3-fold increase or more in nozzle efficiency of a trim process as compared to conventional trim process nozzles.
Feed line (“first feed line”) 240A can be in fluid communication with an annulus defined by the inner surface of the first conduit 220 and the outer surface of the second conduit 240. In one or more embodiments, a feed line (“second feed line”) 242A provides the feed provided by piping 140 (shown in
Any of the one or more catalyst or catalyst systems, purge gases, and monomers can be injected into any of the one or more feed lines 240A, 242A, 244A. The one or more catalyst or catalyst systems can be injected into the first conduit 220 using the first feed line 242A (“catalyst feed line”). The one or more purge gases or inert gases can be injected into the second conduit 240 using the second feed line 240A (“purge gas feed line”). The one or more monomers can be injected into the support member 128 using the third feed line 244A (“monomer feed line”). The feed lines 240A, 242A, 244A can be any conduit capable of transporting a fluid therein. Suitable conduits can include tubing, flex hose, and pipe. A three way valve 215 can be used to introduce and control the flow of the fluids (i.e. catalyst slurry, purge gas and monomer) to the injection nozzle 300. Any suitable commercially available three way valve can be used.
Support member 128 can include a first end having a flanged section 252. The support member 128 can also include a second end that is open to allow a fluid to flow there through. In one or more embodiments, support member 128 is secured to a reactor wall 210. In one or more embodiments, flanged section 252 can be adapted to mate or abut up against a flanged portion 205 of the reactor wall 210 as shown.
In one or more embodiments, at least a portion of the support tube 128 has a tapered outer diameter. The second end (“open end”) of support tube 128 can be tapered to reduce the wall thickness at the tip of the support tube 128. Minimizing the area at the tip of support tube 128 helps prevent fouling. Fouling can be caused due to agglomerate formation of polymer on a nozzle, a concept referred to as “pineappling”. A suitable effervescent nozzle for at least one embodiment of the present disclosure is shown in U.S. Patent Pub. No. 2010/0041841 A1, which is incorporated herein by reference in its entirety.
As shown in
An effervescent nozzle as described herein can further provide control of slurry droplet size into a reactor as a function of gas velocity and not liquid velocity, which allows a desired droplet size to be achieved by adjusting, for example, the carrier gas flow rate (e.g, 114 of
In at least one embodiment, a plurality of effervescent nozzles (not shown) is coupled with a reactor. For example, two or more effervescent nozzles are coupled with a reactor, and the flow rate of slurry from each nozzle is less than if only one effervescent nozzle was coupled with the reactor. In one embodiment, a flow rate of slurry from two effervescent nozzles is about 11 kg/hr from each of the nozzles. An additional nozzle (e.g., a third nozzle) can also be coupled with the reactor and can remain inactive (e.g., offline) until one of the first two nozzles becomes inactive. In one embodiment, each effervescent nozzle (e.g., all three nozzles) is active (e.g., online) during a polymerization process. Each component (e.g., catalyst slurry from one cat pot 102) can be fed to the nozzles using a catalyst flow splitter. A suitable catalyst flow splitter is described in U.S. Pat. No. 7,980,264, which is incorporated herein by reference in its entirety.
Returning to
The example above is not limiting, as additional solutions and slurries may be included. For example, a slurry can be combined with two or more solutions having the same or different catalyst compounds and or activators. Likewise, the solution may be combined with two or more slurries each having the same or different supports, and the same or different catalyst compounds and or activators. Similarly, two or more slurries combined with two or more solutions, for example in-line, where the slurries each comprise the same or different supports and may comprise the same or different catalyst compounds and or activators and the solutions comprise the same or different catalyst compounds and or activators. For example, the slurry may contain a supported activator and two different catalyst compounds, and two solutions, each containing one of the catalysts in the slurry, and each are independently combined, in-line, with the slurry.
The properties of the product polymer may be controlled by adjusting the timing, temperature, concentrations, and sequence of the mixing of the solution, the slurry and any optional added materials (nucleating agents, catalyst compounds, activators, etc.) described above. The MWD, MI, density, MIR, relative amount of polymer produced by each catalyst, and other properties of the polymer produced may also be changed by manipulating process parameters. Any number of process parameters may be adjusted, including manipulating hydrogen concentration in the polymerization system, changing the amount of the first catalyst in the polymerization system, or changing the amount of the second catalyst in the polymerization system. Other process parameters that can be adjusted include changing the relative ratio of the catalysts in the polymerization process (and optionally adjusting their individual feed rates to maintain a steady or constant polymer production rate). The concentrations of reactants in the reactor 122 can be adjusted by changing the amount of liquid or gas that is withdrawn or purged from the process, changing the amount and/or composition of a recovered liquid and/or recovered gas returned to the polymerization process, wherein the recovered liquid or recovered gas can be recovered from polymer discharged from the polymerization process. Further process parameters including concentration parameters that can be adjusted include changing the polymerization temperature, changing the ethylene partial pressure in the polymerization process, changing the ethylene to comonomer ratio in the polymerization process, changing the activator to transition metal ratio in the activation sequence. Time dependent parameters may be adjusted such as changing the relative feed rates of the slurry or solution, changing the mixing time, the temperature and or degree of mixing of the slurry and the solution in-line, adding different types of activator compounds to the polymerization process, and or adding oxygen or fluorobenzene or other catalyst poison to the polymerization process. Any combinations of these adjustments may be used to control the properties of the final polymer product.
In at least one embodiment, the MWD of the polymer product is measured at regular intervals and one of the above process parameters, such as temperature, catalyst compound feed rate, the ratios of the two or more catalysts to each other, the ratio of comonomer to monomer, the monomer partial pressure, and or hydrogen concentration, is altered to bring the composition to the desired level, if necessary. The MWD may be measured by size exclusion chromatography (SEC), e.g., gel permeation chromatography (GPC), among other techniques.
In one embodiment, a polymer product property is measured in-line and in response the ratio of the catalysts being combined is altered. In at least one embodiment, the molar ratio of the catalyst compound in the catalyst component slurry to the catalyst compound in the catalyst component solution, after the slurry and solution have been mixed to form the final catalyst composition, is 500:1 to 1:500, or 100:1 to 1:100, or 50:1 to 1:50 or 40:1 to 1:10. In another embodiment, the molar ratio of a catalyst compound in the slurry to a metallocene catalyst compound in the solution, after the slurry and solution have been mixed to form the catalyst composition, is 500:1, 100:1, 50:1, 10:1, or 5:1. The product property measured can include the dynamic shear viscosity, flow index, melt index, density, MWD, comonomer content, and combinations thereof. In another embodiment, when the ratio of the catalyst compounds is altered, the introduction rate of the catalyst composition to the reactor, or other process parameters, is altered to maintain a desired production rate.
The catalyst system can be used to polymerize one or more olefins to provide one or more polymer products therefrom. Any suitable polymerization process can be used, including, but not limited to, high pressure, solution, slurry, and/or gas phase polymerization processes. In embodiments that use other techniques besides gas phase polymerization, modifications to a catalyst addition system that are similar to those discussed with respect to
The terms “polyethylene” and “polyethylene copolymer” refer to a polymer having at least 50 wt % ethylene derived units. In various embodiments, the polyethylene can have at least 70 wt % ethylene-derived units, at least 80 wt % ethylene-derived units, at least 90 wt % ethylene-derived units, or at least 95 wt % ethylene-derived units. The polyethylene polymers described herein are generally copolymer, but may also include terpolymers, having one or more other monomeric units. As described herein, a polyethylene can include, for example, at least one or more other olefins or comonomers. Suitable comonomers can contain 3 to 16 carbon atoms, from 3 to 12 carbon atoms, from 4 to 10 carbon atoms, and from 4 to 8 carbon atoms. Examples of comonomers include, but are not limited to, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methylpent-1-ene, 1-decene, 1-dodecene, 1-hexadecene, and the like.
Referring again to
The reactor temperature of the fluid bed process can be greater than 30° C., greater than 40° C., greater than 50° C., greater than 90° C., greater than 100° C., greater than 110° C., greater than 120° C., greater than 150° C., or higher. In general, the reactor temperature is operated at a suitable temperature taking into account the sintering temperature of the polymer product within the reactor. Thus, the upper temperature limit in at least one embodiment is the melting temperature of the polyethylene copolymer produced in the reactor. However, higher temperatures may result in narrower MWDs, which can be improved by the addition of a catalyst, or other co-catalysts, as described herein.
Hydrogen gas can be used in olefin polymerization to control the final properties of the polyolefin, such as described in the “Polypropylene Handbook, at pages 76-78 (Hanser Publishers, 1996). Using certain catalyst systems, increasing concentrations (partial pressures) of hydrogen can increase a flow index such as MI of the polyethylene copolymer generated. The MI can thus be influenced by the hydrogen concentration. The amount of hydrogen in the polymerization can be expressed as a mole ratio relative to the total polymerizable monomer, for example, ethylene, or a blend of ethylene and hexene or propylene.
The amount of hydrogen used in the polymerization process can be an amount necessary to achieve the desired MI of the final polyolefin polymer. For example, the mole ratio of hydrogen to total monomer (H2:monomer) can be 0.0001 or greater, 0.0005 or greater, or 0.001 or greater. Further, the mole ratio of hydrogen to total monomer (H2:monomer) can be 10 or less, 5 or less, 3 or less, or 0.10 or less. A range for the mole ratio of hydrogen to monomer can include any combination of any upper mole ratio limit with any lower mole ratio limit described herein. The amount of hydrogen in the reactor at any time can range to up to 5,000 ppm, up to 4,000 ppm in another embodiment, up to 3,000 ppm, or from 50 ppm to 5,000 ppm, or from 50 ppm to 2,000 ppm in another embodiment. The amount of hydrogen in the reactor can range from 1 ppm, 50 ppm, or 100 ppm to 400 ppm, 800 ppm, 1,000 ppm, 1,500 ppm, or 2,000 ppm, based on weight. Further, the ratio of hydrogen to total monomer (H2:monomer) can be 0.00001:1 to 2:1, 0.005:1 to 1.5:1, or 0.0001:1 to 1:1. The one or more reactor pressures in a gas phase process (either single stage or two or more stages) can vary from 690 kPa (100 psig) to 3,448 kPa (500 psig), in the range from 1,379 kPa (200 psig) to 2,759 kPa (400 psig), or in the range from 1,724 kPa (250 psig) to 2,414 kPa (350 psig).
The gas phase reactor can be capable of producing from 10 kg of polymer per hour (25 lbs/hr) to 90,900 kg/hr (200,000 lbs/hr), or greater, and greater than 455 kg/hr (1,000 lbs/hr), greater than 4.540 kg/hr (10,000 lbs/hr), greater than 11,300 kg/hr (25,000 lbs/hr), greater than 15,900 kg/hr (35,000 lbs/hr), and greater than 22,700 kg/hr (50,000 lbs/hr), and from 29,000 kg/hr (65,000 lbs/hr) to 45,500 kg/hr (100,000 lbs/hr).
As noted, a slurry polymerization process can also be used in embodiments. A slurry polymerization process generally uses pressures in the range of from 101 kPa (1 atmosphere) to 5,070 kPa (50 atmospheres) or greater, and temperatures from 0° C. to 120° C., and more particularly from 30° C. to 100° C. In a slurry polymerization, a suspension of solid, particulate polymer can be formed in a liquid polymerization diluent medium to which ethylene, comonomers, and hydrogen along with catalyst can be added. The suspension including diluent can be intermittently or continuously removed from the reactor where the volatile components are separated from the polymer and recycled, optionally after a distillation, to the reactor. The liquid diluent employed in the polymerization medium can be an alkane having from 3 to 7 carbon atoms, such as, for example, a branched alkane. The medium employed should be liquid under the conditions of polymerization and relatively inert. When a propane medium is used the process should be operated above the reaction diluent critical temperature and pressure. In at least one embodiment, a hexane, isopentane iC5, or isobutane iC4 medium can be employed. The slurry can be circulated in a continuous loop system.
A number of tests can be used to compare resins from different sources, catalyst systems, and manufacturers. Such tests can include melt index, high load melt index, melt index ratio, density, die swell, environmental stress crack resistance, among others.
The product polyethylene can have a melt index ratio (MIR) ranging from 10 to less than 300, or, in many embodiments, from 20 to 66. The melt index (MI, I2) can be measured in accordance with ASTM D-1238.
Density can be determined in accordance with ASTM D-792. Density is expressed as grams per cubic centimeter (g/cm3) unless otherwise noted. The polyethylene can have a density ranging from 0.89 g/cm3, 0.90 g/cm3, or 0.91 g/cm3 to 0.95 g/cm3, 0.96 g/cm3, or 0.97 g/cm3. The polyethylene can have a bulk density, measured in accordance with ASTM D-1895 method B, of from 0.25 g/cm3 to 0.5 g/cm3. For example, the bulk density of the polyethylene can range from 0.30 g/cm3, 0.32 g/cm3, or 0.33 g/cm3 to 0.40 g/cm3, 0.44 g/cm3, or 0.48 g/cm3.
In embodiments herein, the present disclosure provides polymerization processes where monomer (such as propylene or ethylene), and optionally comonomer, are contacted with a catalyst system comprising an activator and at least one catalyst compound, as described above. The catalyst compound and activator may be combined in any order, and are combined typically prior to contacting with the monomer.
In at least one embodiment, a polymerization process includes a) contacting one or more olefin monomers with a catalyst system comprising: i) an activator and ii) a catalyst compound of the present disclosure. The activator is a non-coordination anion activator. The one or more olefin monomers may be propylene and/or ethylene and the polymerization process further comprises heating the one or more olefin monomers and the catalyst system to 70° C. or more to form propylene polymers or ethylene polymers, such as propylene polymers.
Monomers useful herein include substituted or unsubstituted C2 to C40 alpha olefins, such as C2 to C20 alpha olefins, such as C2 to C12 alpha olefins, such as ethylene, propylene, butene, pentene, hexene, heptene, octene, nonene, decene, undecene, dodecene and isomers thereof. In at least one embodiment, the monomer comprises propylene and one or more optional comonomers selected from propylene or C4 to C40 olefins, such as C4 to C20 olefins, such as C6 to C12 olefins. The C4 to C40 olefin monomers may be linear, branched, or cyclic. The C4 to C40 cyclic olefins may be strained or unstrained, monocyclic or polycyclic, and may optionally include heteroatoms and/or one or more functional groups. In at least one embodiment, the monomer comprises propylene and an optional comonomer that is one or more C3 to C40 olefins, such as C4 to C20 olefins, such as C6 to C12 olefins. The C3 to C40 olefin monomers may be linear, branched, or cyclic. The C3 to C40 cyclic olefins may be strained or unstrained, monocyclic or polycyclic, and may optionally include heteroatoms and/or one or more functional groups.
Exemplary C2 to C40 olefin monomers and optional comonomers include propylene, propylene, butene, pentene, hexene, heptene, octene, nonene, decene, undecene, dodecene, norbornene, norbornadiene, dicyclopentadiene, cyclopentene, cycloheptene, cyclooctene, cyclooctadiene, cyclododecene, 7-oxanorbornene, 7-oxanorbornadiene, substituted derivatives thereof, and isomers thereof, such as hexene, heptene, octene, nonene, decene, dodecene, cyclooctene, 1,5-cyclooctadiene, 1-hydroxy-4-cyclooctene, 1-acetoxy-4-cyclooctene, 5-methylcyclopentene, cyclopentene, dicyclopentadiene, norbornene, norbornadiene, and their respective homologs and derivatives, such as norbornene, norbornadiene, and dicyclopentadiene.
In at least one embodiment, one or more dienes are present in the polymer produced herein (in other words, the polymer has diene residues) at up to 10 wt %, such as at 0.00001 to 1.0 wt %, such as 0.002 to 0.5 wt %, such as 0.003 to 0.2 wt %, based upon the total weight of the composition. In at least one embodiment 500 ppm or less of diene is added to the polymerization, such as 400 ppm or less, such as 300 ppm or less. In other embodiments at least 50 ppm of diene is added to the polymerization, or 100 ppm or more, or 150 ppm or more.
Diene monomers include any hydrocarbon structure, such as C4 to C30, having at least two unsaturated bonds, wherein at least two of the unsaturated bonds are readily incorporated into a polymer by either a stereospecific or a non-stereospecific catalyst(s). The diene monomers can be selected from alpha, omega-diene monomers (i.e. di-vinyl monomers). The diolefin monomers are linear di-vinyl monomers, such as those containing from 4 to 30 carbon atoms. Examples of dienes include butadiene, pentadiene, hexadiene, heptadiene, octadiene, nonadiene, decadiene, undecadiene, dodecadiene, tridecadiene, tetradecadiene, pentadecadiene, hexadecadiene, heptadecadiene, octadecadiene, nonadecadiene, icosadiene, heneicosadiene, docosadiene, tricosadiene, tetracosadiene, pentacosadiene, hexacosadiene, heptacosadiene, octacosadiene, nonacosadiene, triacontadiene, 1,6-heptadiene, 1,7-octadiene, 1,8-nonadiene, 1,9-decadiene, 1,10-undecadiene, 1,11-dodecadiene, 1,12-tridecadiene, 1,13-tetradecadiene, and low molecular weight polybutadienes (Mw less than 1000 g/mol). Cyclic dienes include cyclopentadiene, vinylnorbornene, norbornadiene, ethylidene norbornene, divinylbenzene, dicyclopentadiene or higher ring containing diolefins with or without substituents at various ring positions.
In at least one embodiment, a catalyst of the present disclosure is capable of producing ethylene polymers having an Mw from 40,000 g/mol to 1,500,000 g/mol, such as from 70,000 g/mol to 1,000,000 g/mol, such as from 90,000 g/mol to 1,000,000 g/mol, such as from 100,000 g/mol to 600,000 g/mol, such as from 100,000 g/mol to 300,000 g/mol, such as from 100,000 g/mol to 200,000 g/mol.
In at least one embodiment, a catalyst of the present disclosure is capable of producing ethylene polymers having a melt index (MI) of 0.6 or greater g/10 min, such as 0.7 or greater g/10 min, such as 0.8 or greater g/10 min, such as 0.9 or greater g/10 min, such as 1.0 or greater g/10 min, such as 1.1 or greater g/10 min, such as 1.2 or greater g/10 min.
“Catalyst productivity” is a measure of how many grams of polymer (P) are produced using a polymerization catalyst comprising W g of catalyst (cat), over a period of time of T hours; and may be expressed by the following formula: P/(T×W) and expressed in units of gPgcat−1 hr−1. In at least one embodiment, the productivity of the catalyst system of a polymerization of the present disclosure is at least 50 g(polymer)/g(cat)/hour, such as 500 or more g(polymer)/g(cat)/hour, such as 800 or more g(polymer)/g(cat)/hour, such as 5,000 or more g(polymer)/g(cat)/hour, such as 6,000 or more g(polymer)/g(cat)/hour.
Useful chain transfer agents are typically alkylalumoxanes, a compound represented by the formula AlR3, ZnR2 (where each R is, independently, a C1-C8 aliphatic radical, such as methyl, ethyl, propyl, butyl, phenyl, hexyl octyl or an isomer thereof) or a combination thereof, such as diethyl zinc, methylalumoxane, trimethylaluminum, triisobutylaluminum, trioctylaluminum, or a combination thereof.
The multi-modal polyolefin produced by the processes disclosed herein and blends thereof are useful in such forming operations as film, sheet, and fiber extrusion and co-extrusion as well as blow molding, injection molding, and rotary molding Films include blown or cast films formed by co-extrusion or by lamination useful as shrink film, cling film, stretch film, sealing films, oriented films, snack packaging, heavy duty bags, grocery sacks, baked and frozen food packaging, medical packaging, industrial liners, membranes, etc., in food-contact and non-food contact applications. Fibers include melt spinning, solution spinning and melt blown fiber operations for use in woven or non-woven form to make filters, diaper fabrics, medical garments, geotextiles, etc. Extruded articles include medical tubing, wire and cable coatings, pipe, geomembranes, and pond liners. Molded articles include single and multi-layered constructions in the form of bottles, tanks, large hollow articles, rigid food containers and toys, etc.
Specifically, any of the foregoing polymers, such as the foregoing ethylene copolymers or blends thereof, may be used in mono- or multi-layer blown, extruded, and/or shrink films. These films may be formed by any number of well-known extrusion or coextrusion techniques, such as a blown bubble film processing technique, wherein the composition can be extruded in a molten state through an annular die and then expanded to form a uni-axial or biaxial orientation melt prior to being cooled to form a tubular, blown film, which can then be axially slit and unfolded to form a flat film. Films may be subsequently unoriented, uniaxially oriented, or biaxially oriented to the same or different extents.
The polymers produced herein may be further blended with additional ethylene polymers (referred to as “second ethylene polymers” or “second ethylene copolymers”) and use in film, molded part and other typical polyethylene applications.
In one aspect of the present disclosure, the second ethylene polymer is selected from ethylene homopolymer, ethylene copolymers, and blends thereof. Useful second ethylene copolymers can comprise one or more comonomers in addition to ethylene and can be a random copolymer, a statistical copolymer, a block copolymer, and/or blends thereof. The method of making the second ethylene polymer is not critical, as it can be made by slurry, solution, gas phase, high pressure or other suitable processes, and by using catalyst systems appropriate for the polymerization of polyethylenes, such as Ziegler-Natta-type catalysts, chromium catalysts, metallocene-type catalysts, other appropriate catalyst systems or combinations thereof, or by free-radical polymerization. In at least one embodiment, the second ethylene polymers are made by the catalysts, activators and processes described in U.S. Pat. Nos. 6,342,566; 6,384,142; 5,741,563; PCT publications WO 03/040201; and WO 97/19991. Such catalysts are well known in the art, and are described in, for example, Ziegler Catalysts (Gerhard Fink, Rolf Mülhaupt and Hans H. Brintzinger, eds., Springer-Verlag 1995); Resconi et al.; and I, II Metallocene-based Polyolefins (Wiley & Sons 2000).
The present disclosure provides, among others, the following aspects, each of which may be considered as optionally including any alternate aspects.
Clause 1. A method for producing a polyolefin comprising:
Ethylene support tube flow rate of 180-250 kg/hr was attempted. Conventional trim processes involve ethylene flow rates of 1200 kg/hr or greater per nozzle while a trim process of the present disclosure can be performed successfully at an ethylene support tube flow rate of 180-250 kg/hr. This was demonstrated experimentally by starting production on the pilot plant by feeding the slurry catalyst to the reactor with ethylene support tube flow in excess of 1300 kg/hr and gradually reducing ethylene support tube flow until reactor continuity events (agglomerations of resin form trapping the heat of reaction and causing chunks and plugging catalysts feeder tubes). Table 1 details the minimum acceptable flow of a conventional trim process versus a trim process of the present disclosure.
Catalyst particle and nozzle droplet numerical balance and liquid mass balance were performed confirming the effervescence nozzle increased efficiency over a conventional trim nozzle. The catalyst system used was obtained by introducing HfP to MAO followed by supportation to form (HfP+SMAO) in a manner analogous to that described in paragraph [0093] of WO 2014/123598.
Below details the objective and results of the catalyst particle and droplet numerical balance and liquid mass balance. To provide desired dispersion into the reactor, the goal for this particular embodiment was for one catalyst particle to be contained in one droplet average. An effervescent nozzle was used because, at adequately high gas velocity through the effervescent nozzle the liquid flow can be increased or decreased moderately (for example +/−50 percent) without changing the size of the droplets produced. This feature is important because the gas velocity can be adjusted to produce the desired droplet size by performing the calculations in paragraph 170 then measuring droplet size versus gas velocity in the lab. Once the target gas velocity is identified it is constant during commercial operations and ensuring the droplet size is constant while the liquid flow rate of iC5 and slurry varies slightly during production.
Furthermore, 0.0625 inch nozzle tip diameter was discovered to work well for a slurry and iC5 mixture to be delivered to the reactor.
First a numerical balance determines how many droplets are required to contain each catalyst particle. For this calculation, the catalyst structural density must be known. Catalyst density was calculated to be 2.50 gm/cc by utilizing the difference in density of the liquid only versus liquid+catalyst solids slurry. The pore volume of ES70 silica is about 1.2 cc/gm and the calculations for the density particle are listed in steps one through five below:
Next a target droplet size basis was taken. A conservative operating scenario is one catalyst particle per droplet average. Catalyst particles can average 55 microns in diameter so the target droplet size will be between 75 micron and 110 micron.
Install 3 Rx. Injection Nozzles for Trim Catalyst Feed
Conventional trim processes involve one nozzle per reactor. Furthermore, spray-dried catalysts have “Fast Light Off” kinetics. “Light off” kinetics is a term that describes how rapidly and vigorously a catalyst will produce polymer as a function of reaction time. Some catalysts exhibit a steady, growing instantaneous polymerization rate (that eventually decays at longer reaction times) while others with a strong “light off” behavior will have a significant spike in instantaneous polymerization rate followed by a decrease in polymerization rate over time.
Spray-dried catalysts would involve very high support tube flow and limited quantity of catalyst through each nozzle to deliver the catalyst into the fluidized bed far enough from the nozzle to prevent “Pineapple” nozzle build up or continuity issues. Because silica-supported catalysts of the present disclosure have slower “light off” kinetics, it is believed that the fluidized bed provides adequate mixing to carry the catalyst away from the nozzles without having to restrict catalyst flow per nozzle. At 36 TPH production rate, the expected slurry catalyst flow rate required is 22.5 kg/hr as calculated in Table 3. The 22.5 kg/hr slurry flow rate can be split between 2 Rx nozzles during normal operation and have a third slurry nozzle installed spare available to switch to if needed.
Catalyst flow rate and productivity reference points:
Conventional trim slurry solutions have a slurry stability of about 5-10% settling at 2-4 days. Below are the results of the slurry stability study. The slurry media studied had mineral oil HB380, higher viscosity mineral oil HB550, HB1000, or HB HV, and Sono Jell (wax/oil specially made material), as shown in Table 4 below and
The result is that only 25-50% Sono Jell with the remainder HB380 showed acceptable Catalyst A slurry stability at 4-6 days.
The impact of higher temperature (40° C. or 104° F.) was studied, as shown in
Note that none of the HB mineral oil samples showed acceptable stability at 3 days. However, as shown in
HB380 Mineral oil and iC5 are two possible trim media. The iC5 trim was found to be a low viscosity trim and when combined with the slurry solution caused catalyst settling and frequent static mixer plugging. Therefore, a higher viscosity HB380 mineral oil trim can be used instead of iC5. Because the higher viscosity Sono Jell can be used to suspend the silica supported catalyst, there were initial concerns that using a mineral oil trim would retard the trim and catalyst molecules reducing trim efficiency. However, it was discovered that excellent trim efficiency was achieved using mineral oil trim media.
Low viscosity hydrocarbon (iC5/iC6) and higher viscosity HB380 mineral oil were tested in a pilot plant and both resulted in good trim efficiency (summary detailed below). The plant uses both iC5 and iC6. HB380 for the trim media reduced settling at the static mixer.
After the successful multi-part trim study with iC5/iC6, trimming EtInd in HB380 mineral oil was tested. This represents a “high viscosity” trim, as opposed to the lower viscosity iC5/iC6 trim solution. The slurry used was the 50/50 mineral oil/Sono Jell mixture with HfP:EtInd in a co-supported 90:10 ratio.
The trial started out at baseline, and then trim was added to target an 80:20 HfP:EtInd ratio. The product MIR response was observed to examine trim impact.
The trial results are plotted in
A sample of the slurry in a small pressure cell was pressured to 100 PSIG with nitrogen and held for 30 minutes at 20° C. to allow nitrogen saturation equilibrium to be reached. Then the pressure was decreased to 25 PSIG. Video and pictures were taken immediately before depressurization, and at 5 seconds, 10 seconds, and 7 minutes. The presence of foam is indicated by the formation and propagation of bubbles. Software quantified the volume of the foam bubbles created.
Slurry/liquid conditions that resulted in foam:
This results in two interesting learnings. First, foam initiation and propagation will occur even if no solid catalyst particles are present in the liquid. Second, a liquid with Sono Jell can create foam but a liquid of HB380 only did not create foam.
The second objective was to study increasing pressure and its impact on foam. Again, foam was created by holding the slurry at 100 PSIG with nitrogen, then the pressure was reduced to 25 PSIG. For this test, the pressure was then increased to 50 PSIG and observations made. Within 5 seconds of increased pressure, the volume of the bubbles shrinks to 50% of their original volume, then remain approximately constant for the next 30 minutes. This change in volume does not exceed the ideal gas law's estimate of the pressure change impact to gas volume. This indicates that diffusion back into the solution may be negligible. Increasing the pressure is an effective way of reducing the impact of foam by cutting the volume of the bubbles but likely has little effect on the gas re-solublizing into the slurry.
This fundamental study of pressure impact on foam prompted two additional tests to be performed. Slurry was placed in a 3 gallon cylinder and rolled at 25 PSIG for 2 hours (matching commercial conditions) then discharged to atmospheric pressure. This entire slurry became foam matching the results above. Slurry in a 3 gallon cylinder was rolled at atmospheric pressure then transferred using 5 PSIG nitrogen to atmospheric pressure. The resulting slurry only contained small bubbles matching the slurry conditions when mixed for use in a plant that are deemed acceptable for both plant and commercial operation.
The tests highlighted a vulnerability in the planned slurry vessel operating conditions. The initial agitated slurry feed pot operating condition was 10 PSIG. Because slurry cylinders are rolled at 25 PSIG foam would be created when transferred down in pressure to the slurry vessel. This was corrected by adjusting the agitated slurry vessel operating condition to 50 PSIG preventing foam creation. This matches plant slurry feed pot operating conditions.
The third aspect studied was temperature impact on existing foam. First, temperature impact on the ability to create foam was studied. Samples at 20° C., 40° C., and 60° C. were soaked at 100 PSIG with nitrogen for 30 minutes then the pressure reduced to 25 PSIG. Samples at 20° C. and 40° C. created foam as typical but the sample at 60° C. created no foam and no small bubbles. Next, whether foam could be eliminated by heating the slurry foam sample to 60° C. was studied. Foam was created by holding the slurry at 100 PSIG with nitrogen then the pressure was reduced to 25 PSIG. Then, the slurry sample was heated to 60° C. The foam bubbles merged and increased in size but the bubbles remained in the slurry. Initially the increase in bubble size was viewed as a negative result indicating temperature would not eliminate foam. However, upon further investigation, the pressure cell used for this experiment had no headspace for gas to escape to. Considering the lack of headspace in the small-scale test, a larger scale test was performed as detailed in the paragraph below.
Foam was not created when pressure was let down at 60° C. However, when existing foam slurry was heated to 60° C., the bubbles merged and became larger but did not disappear. Because the second data point added concern that temperature could not undo foam the following test was performed at BTEC. Foam was created and placed into two glass jars. One glass jar was placed in an oven at 60° C. and the other was the control at room temperature. After two hours in the oven, the foam began to be reduced. After six hours, all of the foam was eliminated and slurry settled out due to reduced viscosity. This finding provides a way to eliminate foam and can be implemented while the slurry is agitated to prevent settling.
Per a standard operating procedure, the slurry will not experience a step down in pressure to prevent foam creation, but these findings allow foam elimination if needed. The agitated slurry vessel heating system was upgraded to 60° C. capability and sight glasses added to the agitated slurry vessel and transfer lines. If foam is created during cylinder rolling and transfer or any other part of the process, the slurry can be transferred to the agitated slurry vessel and heated to 60° C. to eliminate the foam. Then, the setpoint can return to a standard 40° C. and operation can continue as normal. Note that there is no part of the design preventing operating the catalyst slurry delivery system at 60° C., so there is no need to wait for the slurry to cool before proceeding.
Operations request vessel capacity greater than or equal to 3 days at typical rates. The slurry vessel working volume was reduced from 1050 gal to 500 gal. The trim vessel increased to 300 gal with pressure control and level measurement. Table 5 show slurry and trim flow rates and vessel capacity.
Overall, processes of the present disclosure can provide improved trim polymerization processes and can provide low density polyolefins.
All documents described herein are incorporated by reference herein, including any priority documents and/or testing procedures to the extent they are not inconsistent with this text. As is apparent from the foregoing general description and the specific embodiments, while forms of the embodiments have been illustrated and described, various modifications can be made without departing from the spirit and scope of the present disclosure. Accordingly, it is not intended that the present disclosure be limited thereby. Likewise, the term “comprising” is considered synonymous with the term “including.” Likewise whenever a composition, an element or a group of elements is preceded with the transitional phrase “comprising,” it is understood that we also contemplate the same composition or group of elements with transitional phrases “consisting essentially of,” “consisting of,” “selected from the group of consisting of,” or “I” preceding the recitation of the composition, element, or elements and vice versa, e.g., the terms “comprising,” “consisting essentially of,” “consisting of” also include the product of the combinations of elements listed after the term.
For the sake of brevity, only certain ranges are explicitly disclosed herein. However, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, within a range includes every point or individual value between its end points even though not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.
All priority documents are herein fully incorporated by reference for all jurisdictions in which such incorporation is permitted and to the extent such disclosure is consistent with the description of the present disclosure. Further, all documents and references cited herein, including testing procedures, publications, patents, journal articles, etc. are herein fully incorporated by reference for all jurisdictions in which such incorporation is permitted and to the extent such disclosure is consistent with the description of the present disclosure. While the present disclosure has been described with respect to a number of embodiments and examples, those skilled in the art, having benefit of the present disclosure, will appreciate that other embodiments can be devised which do not depart from the scope and spirit of the present disclosure as described herein.
This application claims the benefit of Ser. No. 62/754,248, filed Nov. 1, 2018, the disclosure of which is hereby incorporated by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2019/058903 | 10/30/2019 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62754248 | Nov 2018 | US |
