Patent Application
20190091670
The present invention relates to inorganic, porous, framework—layered double hydroxide (LDH) core-shell materials as catalyst supports, to methods of making them and to their us in ethylene polymerisation.
Layered double hydroxides (LDHs) are a class of compounds which comprise two or more metal cations and have a layered structure. A review of LDHs is provided in Structure and Bonding; Vol. 119, 2005 Layered Double Hydroxides ed. X Duan and D. G. Evans. The hydrotalcites, perhaps the most well-known examples of LDHs, have been studied for many years. LDHs can intercalate anions between the layers of the structure.
LDHs have captured much attention in recent years due to their impact across a range of applications, including catalysis, optics, medical science and in inorganic-organic nanocomposites. A new family of dispersible, hydrophobic
LDHs using an aqueous miscible organic solvent treatment (AMOST) method has been synthesized. These, so called, AMO-LDHs may exhibit surface areas in excess of 400 m2g−1 and pore volumes in excess of 2.15 cc g−1, which is nearly two orders of magnitude higher than conventional LDHs. AMO-LDHs have a unique chemical composition, which may be defined by the formula A
[Mz+1−x M′y+x (OH)2]a+ (An−)a/n.bH2O.c(AMO-solvent) (A),
where Mz+ is a metal cation of charge z or a mixture of two or more metal cations of charge z; M′y+ is a metal cation of charge y or a mixture of two or more metal cations of charge y; z is 1 or 2; and y is 3 or 4, 0<x<1, b=0-10, c=0.01-10, A is a charge compensating anion, n, n>0 (typically 1-5) and a=z(1−x)+xy−2. AMO-solvents are those which are 100% miscible in water. Typically, the AMO-solvent is acetone or methanol.
Core shell particles are described in the literature by “core@shell” (for example by Teng et al, Nano Letters, 2003, 3, 261-264), or by “core/shell” (for example J. Am. Chem. Soc., 2001, 123, pages 7961-7962). We have adopted the “core@shell” nomenclature as it is emerging as the more commonly accepted abbreviation.
SiO2/LDH core-shell microspheres are described by Shao et al, Chem. Mater. 2012, 24, pages 1192-1197. Prior to treatment with a metal precursor solution, the SiO2 microspheres are primed by dispersing them in an Al(OOH) primer sol for two hours with vigorous agitation followed by centrifuging, washing with ethanol and drying in air for 30 minutes. This priming treatment of the SiO2 microspheres was repeated 10 times before the SiO2 spheres thus coated with a thin Al(OOH) film were autoclaved at 100° C. for 48 hours in a solution of Ni(NO3)2.6H2O and urea. Hollow SiO2—NiAl-LDH microspheres obtained by this process were reported as exhibiting excellent pseudocapacitance performance. Unfortunately, the requirement for the Al(OOH) priming of the SiO2 surface, prior to LDH growth, makes this process unsuitable for use on an industrial scale.
Chen et al, J. Mater. Chem. A, 1, 3877-3880 describes the synthesis of SiO2@MgAl-LDHs having use in the removal of pharmaceutical pollutants from water.
Furthermore, coating LDHs and similar materials onto a given inorganic, porous, framework typically results in a reduction of porosity and surface area of the core@framework material. This usually arises due to the coating ‘filling in’ or covering the pores of the inorganic framework.
Polyethylene is the most widely used polyolefin with a global production in 2011 of over 75 million tons per year. Innovation in both the synthesis and the properties of polyethylene is still at the forefront in both industry and academia. It is now more than thirty years since the first discoveries of highly active homogeneous catalysts for olefin polymerisation. Since then, intensive research has led to greater control over polymerisation activity and polymer structure than can generally be obtained with the original type of heterogeneous Ziegler-Natta catalysts. Many different supports (e.g. SiO2, Al2O3, MgCl2 and clays) and immobilisation procedures have been investigated.
The problem to be solved by the present invention is to provide a novel support material for heterogeneous ethylene polymerisation that gives high polymerisation activity per mol transition metal, good molecular weight control and regular free-flowing polymer particles.
Furthermore, it is an objective of the present invention to provide novel support material for heterogeneous ethylene polymerisation that have high surface areas and porosities, preferably surface areas and porosities that not significantly altered by the coating process.
According to a first aspect of the present invention, there is provided a catalyst system comprising an activated solid support material and having, on its surface, one or more catalytic transition metal complex, wherein the solid support material comprises a core@layered double hydroxide shell material having the formula I
Tp @ {[Mz+(1−x)M′xy+(OH)2]a+(Xn−)a/n.bH2O.c(AMO-solvent)}q (I)
wherein T is a solid, porous, inorganic oxide-containing framework material, Mz+ and My+ are independently selected charged metal cations; Mz+ is a metal cation of charge z or a mixture of two or more metal cations each independently having the charge z; M′y+ is a metal cation of charge y or a mixture of two or more metal cations each independently having the charge y;
0<x<0.9;
b is 0 to 10;
c is 0.01 to 10;
p>0;
q>0;
Xn− is an anion; with n>0;
a=z(1−x)+xy−2; and
According to a second aspect of the present invention, there is provided a method of making the catalyst system according to any of the preceding claims which comprises
Tp @ {[Mz+(1−x)M′xy+(OH)2]a+(Xn−)a/n.bH2O.c(AMO-solvent)}q (I)
According to a third aspect of the present invention, there is provided a catalyst system, as defined herein above, obtainable by, obtained by, or directly obtained by the method defined herein.
According to a fourth aspect of the present invention, there is provided a use of a catalyst system, as defined herein, in combination with a suitable scavenger as a catalyst in the polymerisation and/or copolymerisation of at least one olefin for producing a homopolymer and/or copolymer.
According to a fifth aspect of the present invention, there is provided a process for preparing a polyolefin homopolymer or a polyolefin copolymer which comprises reacting olefin monomers in the presence of a catalyst system, as defined herein, wherein the polyolefin is preferably polyethylene and the olefin monomer is preferably ethylene.
The following terms “core@layered double hydroxide shell”, “inorganic porous framework@LDH core-shell material”, “core@LDH” and “core@AMO-LDH” are be used synonymously throughout the application. All of these terms may be used interchangeably to refer to a central core material (e.g. an inorganic porous framework material) which is coated with a layer of layered double hydroxide. Similarly, the term “Tp @ {[Mz+(1−x)M′xy+(OH)2]a+(Xn−)a/n.bH2O.c(AMO-solvent)}q” will be understood as referring to a solid, porous, inorganic oxide-containing framework material that is coated with one or more layers of layered double hydroxide of the given formula.
Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.
The present invention provides a catalyst system comprising an activated solid support material having, on its surface, one or more catalytic transition metal complex wherein the solid support material comprises a core@layered double hydroxide shell material having the formula
Tp @ {[Mz+(1−x)M′xy+(OH)2]a+(Xn−)a/n.bH2O.c(AMO-solvent)}q (I)
wherein T is a solid, porous, inorganic oxide-containing framework material, Mz+ is a metal cation of charge z or a mixture of two or more metal cations each independently having the charge z; M′y+ is a metal cation of charge y or a mixture of two or more metal cations each independently having the charge y;
The catalyst systems of the present invention advantageously allow for novel catalyst supports with high porosities and surface areas, that allow for good turn overs and molecular weight control in the polymerisation of ethylene.
A core-layered double hydroxide shell material comprises a core microparticle having solid AMO-LDH attached to its surface. Such a material is denoted as core@AMO-LDH. The core microparticles are negatively charged, which compliments the positive charged surface of AMO-LDHs, allowing for additive-free binding of the AMO-LDH by electrostatic interactions.
The core microparticles are solid, porous, inorganic oxide-containing framework materials, and thus are synonymously referred to as such throughout this application.
The core@layered double hydroxide shell materials are prepared by growing a LDH on to the surface of the solid, porous, inorganic oxide-containing framework material.
By growing the LDHs on the surface of the solid, porous, inorganic oxide-containing framework material the inventors surprising found that discrete particles of core@layered double hydroxide material with high porosities, surface area and excellent absorption properties could be achieved. The treatment with and subsequent inclusion of an aqueous miscible organic (AMO) solvent in the core@layered double hydroxide shell material was found to further increase the improvement in porosity, surface area and absorption demonstrated by the core@layered double hydroxide shell materials.
Furthermore, by growing the LDHs on the surface of the solid, porous, inorganic oxide-containing framework material the thickness of the LDH layer is able to be controlled, which advantageously allows for uniform particles to be prepared.
Suitably, the core@layered double hydroxide materials of the present invention comprise an LDH layer with an average thickness of between 5 nm and 300 nm. More suitably, the core@layered double hydroxide materials of the present invention comprise an LDH layer with an average thickness of between 30 nm and 200 nm. Yet more suitably, the core@layered double hydroxide materials of the present invention comprise an LDH layer with an average thickness of between 40 nm and 150 nm. Most suitably, the core@layered double hydroxide materials of the present invention comprise an LDH layer with an average thickness of between 40 nm and 100 nm.
Furthermore, the core@layered double hydroxide materials of the present invention allow for coated solid, porous, inorganic oxide-containing framework materials which retain the surface area and porosity characteristics of their component materials.
In a particular embodiment, the core@layered double hydroxide materials have specific surface area (a Brunauer-Emmett Teller (BET) surface area) of at least 50 m2/g, preferably at least 100 m2/g, more preferably at least 250 m2/g, yet more preferably at least 350 m2/g, even more preferably at least 450 m2/g, still more preferably at least 550 m2/g, and most preferably at least 650 m2/g.
In another embodiment, the core@layered double hydroxide materials have an external surface area of at least 50 m2/g, preferably at least 100 m2/g, more preferably at least 125 m2/g, even more preferably at least 150 m2/g, and most preferably at least 175 m2/g.
In a further embodiment, the core@layered double hydroxide materials have a micropore surface area of at least 50 m2/g, preferably at least 100 m2/g, more preferably at least 150 m2/g, yet more preferably at least 200 m2/g, even more preferably at least 300 m2/g, and most preferably at least 400 m2/g.
The core material T, as stated above, is a solid, porous, inorganic oxide-containing framework material. Typically, this framework material is a molecular sieve which is composed of a porous framework structure which contains ring structures comprising atoms in a tetrahedral arrangement. The framework, as stated above, is porous and comprises pores having a diameter of up to 50 nm, suitably up to 40 nm, more suitably up to 30 nm and most suitably up to 20 nm. Accordingly, the framework material may be either microporous, containing pores with a diameter less than 2 nm, or mesoporous, containing pores with a diameter of between 2 and 50 nm.
In one embodiment, the framework material is microporous, i.e. having pores of diameter less than 2 nm, suitably less than 1.5 nm and more suitably less than 1 nm.
In another embodiment, the framework material is mesoporous, i.e. having pores of diameter of between 2 nm to 50 nm, suitably between 2 nm and 30 nm, more suitably between 2 nm and 20 nm and most suitably between 2 nm and 10 nm.
Preferably, the molecular sieve comprises a silicate, for example aluminium silicate, vanadium silicate or iron silicate. Alternatively, the molecular sieve comprises silicon-aluminium phosphate (SAPO) or aluminium phosphate (A1PO).
According to an embodiment of the invention, the molecular sieve material is aluminium silicate. Typically, the silicon : aluminium molar ratio is from 1 to 100. Preferably, the aluminium silicate is one in which the silicon:aluminium ratio is 1 to 50, more preferably 1 to 40. A further preferred aluminium silicate has a silicon:aluminium ratio of 5:100, preferably 5 to 50, more preferably 5 to 40.
According to an embodiment, the solid, porous, inorganic oxide-containing framework material T is a zeolite material. Zeolites are microporous crystalline solids with well-defined structures and, generally, they contain silicon, aluminium and oxygen in their framework and cations, water and/or other molecules within their pores. Typically, the zeolite material will be composed of aluminium silicate. Preferably, the aluminium silicate zeolite has a framework structure selected from zeolite types A, X, Y, LTA, FAU, BEA, MOR and MFI. In the case of the latter (BEA, MOR and MFI), this is the framework code according to the Structure Commission of the International Zeolite Association. Such three letter codes are assigned to particular zeolite structures to identify the type of material they are composed of and the structure they adopt. For example, LTA is the code for zeolite type Linde Type A and MFI is the code for zeolite type ZSM-5.
The aluminium silicate zeolite may have a framework structure containing non-framework cations. Such cations may be organic cations or inorganic cations. A framework structure may contain both inorganic and organic cations as non-framework cations. Such non-framework cations may, for example, be selected from NR4+, where R is an optionally-substituted alkyl group, (e.g. R=Me, Et, Pr, Bu), Na+, K+, Cs+ and H+. Suitably, the non-framework cation is selected from Na+, H+ or NR4+, wherein R is methyl or ethyl.
The aluminium silicate zeolite may be a crystalline aluminosilicate zeolite having a composition, in terms of mole ratios of oxides, as follows:
0.9±0.2 Mα2/n O:Al2O3 :βSiO2:γH2O
wherein Mα is at least one cation having a valence n, β is at least 2 and γ is between 0 and 40.
Each zeolite classification type (e.g. LTA, FAU etc) may have one or more further sub divisions associated with it. For example, FAU zeolites can be further sub divided into X or Y zeolites depending on the silica-to-alumina ratio of their framework; with X zeolites having a silica-to-alumina ratio of between 2 to 3 and Y zeolites having a silica-to-alumina ratio of greater than 3. It will be understood that all such sub-divisions are covered by the definitions recited above.
In a particular embodiment of the present invention, the solid, porous, inorganic oxide-containing framework material is selected from: i) an aluminium silicate with a framework structure selected from zeolite types LTA, FAU, BEA, MOR or MFI; ii) an aluminophosphate; iii) a silicoaluminophosphate; or iv) a mesoporous silicate. Suitably, the solid, porous, inorganic oxide-containing framework material is selected from: i) an aluminium silicate with a framework structure selected from zeolite types LTA, FAU or MFI; ii) a microporous aluminophosphate; iii) a microporous silicoaluminophosphate; or iv) a mesoporous silicate selected from MCM-41 (Mobil Composition of Matter No. 41) or SBA-15 (Santa Barbara Amorphous No. 15). More suitably, the solid, porous, inorganic oxide-containing framework material is selected from; i) an aluminium silicate with a framework structure selected from zeolite types FAU or MFI; ii) a microporous aluminophosphate; iii) a microporous silicoaluminophosphate; or iv) a mesoporous silicate selected from MCM-41 (Mobil Composition of Matter No. 41) or SBA-15 (Santa Barbara Amorphous No. 15). Most suitably, the solid, porous, inorganic oxide-containing framework material is selected from; i) an aluminium silicate with a framework structure selected from zeolite types FAU or MFI; ii) a microporous aluminophosphate; or iii) a microporous silicoaluminophosphate.
In further embodiment, the solid, porous, inorganic oxide-containing framework material is selected from a zeolite selected from HY 5.1 or ZSM5-23, the microporous aluminophosphate AIPOS, the microporous silicoaluminophosphate SAPOS, or a mesoporous silicate selected from MCM-41 (Mobil Composition of Matter No. 41) or SBA-15 (Santa Barbara Amorphous No. 15).
The LDH grown on the surface of the solid, porous, inorganic oxide-containing framework material comprises, and preferably consists of, LDH represented by the general formula (I)
[Mz+1−x M′y+x(OH)2]a+(Xn−)a/n.bH2O.c(AMO-solvent) (I),
wherein;
As stated above, Mz+ and M′y+ are different charged metal cations. Mz+ is a metal cation of charge z or a mixture of two or more metal cations of charge z; M′y+ is a metal cation of charge y or a mixture of two or more metal cations of charge y.
Having regard to the fact that z=1 or 2, M will be either a monovalent metal or a divalent metal. M′, in view of the fact that y=3 or 4, will be a trivalent metal or a tetravalent metal.
A preferred example of a monovalent metal, for M, is Li. Examples of divalent metals, for M, include Ca, Mg, Zn, Fe, Co, Cu and Ni and mixtures of two or more of these. Preferably, the divalent metal M, if present, is Ca, Ni or Mg. Examples of metals, for M′, include Al, Ga, In, Y and Fe. Preferably, M′ is Al. Preferably, the LDH will be a Li—Al, an Mg—Al or a Ca—Al AMO-LDH.
The anion Xn− in the LDH is any appropriate inorganic or organic anion. Examples of anions that may be used, as Xn−, in the LDH include carbonate, hydroxide, nitrate, borate, sulphate, phosphate and halide (F−, Cl−, Br−, I−) anions. Preferably, the anion Xn−is selected from CO32−, NO3− and Cl−.
The AMO-solvent is any aqueous miscible organic solvent, preferably a solvent which is >95%, more preferably >98% and most suitably 100% miscible with water. Examples of suitable water-miscible organic solvents for use in the present invention include one or more of acetone, acetonitrile, dimethylformamide, dimethylsulfoxide, dioxane, ethanol, methanol, n-propanol, isopropanol, or tetrahydrofuran. Preferably, the AMO-solvent is selected from acetone, methanol, isopropanol and ethanol, with acetone and ethanol being the particularly preferred solvent and ethanol being the most preferred solvent.
According to one preferred embodiment, the layered double hydroxides are those having the general formula I above in which:
Preferably, in the LDH of the above formula, M is Mg or Ca and M′ is Al. The counter anion Xn−is typically selected from CO32−, OH−, F−, Cl−, Br−, I−, SO42−, NO3− and PO43−. In a most preferred embodiment, the LDH will be one wherein M is Mg, M′ is Al and Xn− is CO32−.
The following represent particular embodiments of the core@layered double hydroxide shell material:
Tp@{[Mz+(1−x)M′y+x(OH)2]a+(Xn−)a/n.bH2O.c(AMO-solvent)}q (I)
Tp@{[Mz+(1−x)M′y+x(OH)2]a+(Xn−)a/n.bH2O.c(AMO-solvent)}q (Ia)
Tp@{[Mz+(1−x)M′y+x(OH)2]a+(Xn−)a/n.bH2O.c(AMO-solvent)}q (Ib)
Tp@{[Mz+(1−x) M′y+x(OH)2]a+(Xn−)a/n.bH2O.c(ethanol)}q (Ic)
Tp@{[Mz+(1−x)M′y+x(OH)2]a+(Xn−)a/n.bH2O.c(ethanol)}q (Id)
The core@LDH shell material of the invention, as described above, may be prepared by a method which comprises the steps:
In carrying out the method of preparing the core@AMO-LDHs, typically the core microparticles are dispersed in an aqueous solution containing the desired anion salt, for example Na2CO3. A metal precursor solution, i.e. a solution combining the required monovalent or divalent metal cations and the required trivalent cations may then be added, preferably drop-wise, into the dispersion of the core microparticles. Preferably, the addition of the metal precursor solution is carried out under stirring. The pH of the reaction solution is preferably controlled within the pH range 8 to 11, more preferably 9 to 10. At pH 9 AMO-LDH nanosheets are attached to the surface of the core particles. When pH was adjusted to 10, it is clearly observed that a uniform layer of LDH nanosheets is homogeneously grown on the surface of the particles with hierarchal texture. The AMO-LDH layer thickness achieved at pH 10 is typically 80-110 nm. Increasing the pH to 11 also shows full coverage of the surface with AMO-LDH nanosheets. Typically, NaOH may be used to adjust the pH of the solution.
During the reaction, the LDH produced from the metal precursor solution reaction is formed on the surfaces of the core material particles as nanosheets.
Without wishing to be bound by theory, it is believed that a small amount of aluminium leaching from the porous, inorganic framework material allows the seeded growth of the LDHs on to their surface.
It is preferred that the temperature of the metal ion containing solution in step (a) is within a range of from 20 to 150° C., more preferably, from 20 to 80° C., yet more preferably, from 20 to 50° C. and most preferably from 20 to 40° C.
The obtained solid product is collected from the aqueous medium. Examples of methods of collecting the solid product include centrifugation and filtration. Typically, the collected solid may be re-dispersed in water and then collected again. Preferably, the collection and re-dispersion steps are repeated twice. In order to obtain a product containing AMO-solvent, the material obtained after the centrifugation/re-dispersion procedure described above is washed with, and preferably also re-dispersed in, the desired solvent, for instance acetone. If re-dispersion is employed, the dispersion is preferably stirred. Stirring for more than 2 hours in the solvent is preferable. The final product may then be collected from the solvent and then dried, typically in an oven for several hours.
The growth of AMO-LDH nanosheets on the surface of the SiO2 microspheres is “tuneable”. That is to say, by varying the chemistry of the precursor solution and the process conditions, for instance the pH of the reaction medium, temperature of the reaction and the rate of addition of the precursor solution to the dispersion of core microparticles, the extent of, and the length and/or thickness of the AMO-LDH nanosheets formed on the surfaces of the core microparticles can be varied.
The production of the core@AMO-LDH microparticles according to the invention can be carried out as a batch process or, with appropriate replenishment of reactants, as a continuous process.
In another aspect of the present invention, there is provided a core@layered double hydroxide shell material obtainable by, obtained by, or directly obtained by the process described hereinabove.
Catalyst systems
As stated above, the catalyst system of the invention comprises a solid support material, as described above, having on its surface one or more catalytic transition metal complexes.
The catalyst system of the invention exhibit superior catalytic performance when compared with current permethyl pentalene metallocene compounds/compositions used in the polymerisation of α-olefins.
By the term “transition metal” it is meant a d-block metal, examples of which include, but are not limited to, zirconium, iron, chromium, cobalt, nickel, titanium and hafnium. The transition metal will be complexed with one or more ligands, or aromatic or heteroaromatic cyclic compounds to achieve complexes which may be summarized under the term metallocene. Such aromatic compounds, useful for complexing with the transition metal, include optionally-substituted cyclopentadiene, optionally-substituted indene and optionally-substituted pentalene. The aromatic compound used to complex the transition metal may, further, contain two linked, optionally-substituted cyclopentadiene groups or two linked, optionally-substituted indene and optionally-substituted pentalene groups. In such linked moieties, the linking group may be provided by a lower alkylene group. Preferably, the catalytic transition metal complex is a metallocene containing zirconium or hafnium.
Examples of catalysts include known polymerisation catalysts, for example metallocenes, constrained geometry, Fl complexes and dimino complexes.
According to one embodiment of the invention, the transition metal complex used in the catalyst system will be selected from:
According to another embodiment of the invention, the transition metal complex used in the catalyst system will be selected from:
In the formulae shown above, EBI is ethylene bridged indene, 2-Me,4-PhSBI is dimethylsilyl bridged 2-methyl,4-phenylindene, nBuCp is n-butylcyclopentadiene.
As stated above, the catalyst system of the invention may contain more than one catalytic transition metal complex, preferably 1 to 4 and more preferably 1 to 2 catalytic transition metal complexes.
In a preferred embodiment, the system is obtainable by a process comprising the step of activating the solid support material with an alkylaluminoxane or trisobutylaluminium (TIBA), triethylaluminium (TEA) or diethylaluminium chloride (DEAC).
In a further preferred embodiment, the alkylaluminoxane is methylaluminoxane (MAO) or modified methylaluminoxane (MMAO).
According to another aspect of the present invention, there is provided a method of making the catalyst system which comprises
Tp @ {[Mz+(1−x)M′xy+(OH)2]a+(Xn−)a/n.bH2O.c(AMO-solvent)}q (I)
Preferably, the solid support material has the formula I in which M′ is Al.
More preferably, the solid support material has the formula I in which M is Li, Mg or Ca or mixtures thereof.
Most preferably, the solid support material has the formula I in which Xn− is selected from CO32−, OH−, F−, Cl−, Br−, I−, SO42−, NO3− and PO43−, preferably CO32−, Cl− and NO3−, or mixtures thereof.
It is preferred that the solid support material has the formula I in which M is Mg, M′ is Al and Xn− is CO3−.
It is further preferred that c, in the formula I for the solid support material, is >0 and AMO-solvent is acetone and/or methanol, preferably acetone.
In a more preferred embodiment, the catalytic transition metal complex is at least one complex of a metal selected from zirconium, iron, chromium, cobalt, nickel, titanium and hafnium, the complex containing one or more aromatic or heteroaromatic ligands.
It is preferred that the catalytic transition metal complex is a metallocene containing zirconium or hafnium. The catalyst system of the present invention may be made by a process comprising treating the core@AMO-LDH, as described above, with at least one transition metal complex, as described above, having catalytic activity in the polymerisation of olefins. Typically, the treatment will be carried out in a slurry of the core@AMO-LDH in an organic solvent, for example toluene. According to this slurry process, a slurry of the core@AMO-LDH in, e.g., toluene is prepared. Separately, a solution of the catalytic transition metal complex in e.g. toluene is prepared and then added to the core@AMO-LDH containing slurry. The resulting combined mixture is then heated, for instance at 80° C., for a period of time. The solid product may then be filtered from the solvent and dried under vacuum.
Preferably, the core@ AMO-LDH is heat-treated, for instance at a temperature greater than 110° C., before it is slurried in the organic solvent.
Preferably, the heat treated material is contacted with an activator, for example an alkylaluminium activator such as methylaluminoxane, before or after being treated with the catalytic transition metal complex. Typically, methylaluminoxane is dissolved in a solvent, e.g. toluene, and the resulting solution is added to a slurry of calcined core@AMO-LDH in toluene. The slurry may then be heated, for instance at 80° C., for 1-3h prior to being filtered from the solvent and dried. According to a preferred embodiment, the core@AMO-LDH is treated with methylaluminoxane before being treated with a solution of the catalytic material.
In an embodiment, the heat treated material obtained from the thermal treatment step (b) is activated with an alkylaluminoxane or trisobutylaluminium (TIBA), triethylaluminium (TEA) or diethylaluminium chloride (DEAC). Suitably, the heat treated material obtained from the thermal treatment step (b) is activated with methylaluminoxane (MAO) or modified methylaluminoxane (MMAO).
The catalytic compounds will be present on the surface of the solid support material. For instance, they may be present on the surface as a result of adsorption, absorption or chemical interactions.
The following represent particular embodiments of the catalyst system:
Tp@{[Mz+(1−x)M′y+x(OH)2]a+(Xn−)a/n.bH2O.c(AMO-solvent)}q (II)
Tp@{[Mz+(1−x)M′y+x(OH)2]a+(Xn−)a/n.bH2O.c(AMO-solvent)}q (IIa)
Tp@{[Mz+(1−x)M′y+x(OH)2]a+(Xn−)a/n.bH2O.c(AMO-solvent)}q (IIb)
Tp@{[Mz+(1−x)M′y+x(OH)2]a+(Xn−)a/n.bH2O.c(ethanol)}q (IIc)
Tp@{[Mz+(1−x)M′y+x(OH)2]a+(Xn−)a/n.bH2O.c(ethanol)}q (Id)
The catalyst systems of the present invention may be used in the polymerisation of olefins, in particular ethylene.
Thus, according to a further aspect of the present invention, there is provided a use of the inventive catalyst system in combination with a suitable scavenger as a catalyst in the polymerisation and/or copolymerisation of at least one olefin for producing a homopolymer and/or copolymer, preferably comprising 1 to 10 wt % of a (4-8C)-α-olefin.
The present invention also provides a process for producing a polymer of an olefin which comprises contacting the olefin, preferably ethylene, with a catalyst system according to the invention, as described above.
Thus, as discussed hereinbefore, the present invention also provides the use of a composition defined herein as a polymerisation catalyst, preferably to produce polyethylene.
In one embodiment, the polyethylene is a homopolymer made from polymerized ethene monomers.
In another embodiment, the polyethylene is a copolymer made from polymerized ethene monomers comprising 1-10 wt % of (4-8C) α-olefin (by total weight of the monomers). Suitably, the (4-8C) α-olefin is 1-butene, 1-hexene, 1 -octene, or a mixture thereof.
It will be appreciated that any suitable scavenger may be used in combination with the catalyst system in the polymerisation and/or copolymerisation of at least one olefin for producing a homopolymer and/or copolymer. Suitably, the scavenger is selected from an alkylaluminoxane, trisobutylaluminium (TIBA), triethylaluminium (TEA) or diethylaluminium chloride (DEAC). More suitably, the scavenger is selected from methylaluminoxane (MAO), modified methylaluminoxane (MMAO), trisobutylaluminium (TIBA), triethylaluminium (TEA) or diethylaluminium chloride (DEAC). Most suitably, the scavenger is selected from methylaluminoxane (MAO) or modified methylaluminoxane.
As discussed hereinbefore, the present invention also provides a process for preparing (forming) a polyolefin (e.g. a polyethylene) which comprises reacting olefin monomers in the presence of a composition (catalyst system) defined herein.
In another embodiment, the olefin monomers are ethene monomers.
In another embodiment, the olefin monomers are ethene monomers comprising 1-10 wt % of (4-8C) α-olefin (by total weight of the monomers). Suitably, the (4-8C) α-olefin is 1-butene, 1-hexene, 1-octene, or a mixture thereof.
A person skilled in the art of olefin polymerisation will be able to select suitable reaction conditions (e.g. temperature, pressures, reaction times etc.) for such a polymerisation reaction. A person skilled in the art will also be able to manipulate the process parameters in order to produce a polyolefin having particular properties.
In a particular embodiment, the polyolefin is polyethylene.
Finally, it is preferred that the process is performed at a temperature of 50 to 100° C., preferably 60 to 100° C., more preferably 70 to 80° C.
Experimental Methods
1. General Details
1.1 Powder X-Ray Diffraction
Powder X-ray diffraction (XRD) data were collected on a PANAnalytical X'Pert Pro diffractometer in reflection mode and a PANAnalytical Empyrean Series 2 at 40 kV and 40 mA using Cu Ka radiation (α1=1.54057 Å, α2=1.54433 Å, weighted average=1.54178 Å). Scans were recorded from 5°≤0≤70° with varying scan speeds and slit sizes. Samples were mounted on stainless steel sample holders. The peaks at 43-44° are produced by the XRD sample holder and can be disregarded.
1.2 Thermogravimetric Analysis
Thermogravimetric analysis (TGA) measurements were collected using a Netzsch STA 409 PC instrument. The sample (10-20 mg) was heated in a corundum crucible between 30° C. and 800° C. at a heating rate of 5° C. min−1 under a flowing stream of nitrogen.
1.3 Transmission Electron Microscopy
Transmission Electron Microscopy (TEM) analysis was performed on a JEOL 2100 microscope with an accelerating voltage of 200 kV. Particles were dispersed in water or ethanol with sonication and then cast onto copper grids coated with carbon film and left to dry.
1.4 Brunauer-Emmett-Teller Surface Area Analysis
Brunauer-Emmett-Teller (BET) specific surface areas were measured from the N2 adsorption and desorption isotherms at 77 K collected from a Quantachrome Autosorb surface area and pore size analyser.
General Method of Synthesis of Catalyst Support Material
Zeolite (100 mg) was dispersed in deionised water (20 mL) using ultrasound treatment. After 30 minutes, the sodium carbonate was added to the solution and a further 6 minutes of sonication was carried out to form solution A. An aqueous solution (19.2 mL) containing magnesium nitrate hexahydrate and aluminium nitrate nonahydrate was added at a rate of 60 mL/h to solution A under vigourous stirring. The pH of the reaction solution was controlled with the addition of 1 M NaOH by an autotitrator. The obtained suspension was stirred for 1 h. The obtained solid was collected and then re-dispersed in deionised water (40 mL) and stirred for 1 h. The collection and re-dispersion was repeated once. The samples (Zeolite@LDH) were then dried under vacuum. The Zeolite@AMO-LDH was synthesized using the same procedure. However, before final isolation, the solid was treated with AMOST method, which was washed with acetone (40 mL) and then re-dispersed in acetone (40 mL) under stirring for overnight. The solid was then dried under vacuum for materials characterization.
Using this general method, zeolite@LDH shell materials were synthesised using the different zeolite types HY5.1, HY30, HY15, ZSM5, ZSM5-23 and ZSM5-40.
The zeolite@LDH shell materials obtained using these different zeolite types were characterised and/or studied according to the following.
Characterisation of HY5.1@LDH
The zeolite HY5.1 was used to attempt the synthesis of the first Zeolite@AMO-LDH.
Comparison between HY5.1@AMO-LDH and HY5.1@LDH
A similar procedure was used to synthesise and characterise zeolite core-shell material using conventionally synthesised LDH, HY5.1@LDH,
Variation of Si/Al Ratio in HY@AMO-LDH
Variation of Other Parameters using HY30@LDH
The coating of LDH on the HY30 surface did not increase by changing temperature and Mg/Al ratio. However, a change in pH and Na2CO3 soaking time demonstrated a small improvement in affinity of LDH on the surface.
Variation of Zeolite to LDH Ratio in HY15@AMO-LDH
Variation of Si/Al Ratio in ZSM5@LDH
LDH can easily grow on the surface of ZSM5 regardless of the Si/Al ratio.
Variation of Zeolite to LDH Ratio in ZSM5-23@LDH
By increasing the amount of ZSM5-23, the free LDH was reduced. However, less ZSM5 was coated with LDH.
Variation of the Drop Rate in ZSM5-40@LDH
Change in the drop rate has no significant effect.
Characterisation of ZSM5-23@AMO-LDH
LDH-W means the LDH was prepared by the conventional method in water. LDH-A means the LDH was treated with acetone.
Further Core @ Layered Double Hydroxide Shell Materials
Variation of the Anion of the LDH
Example Method of HY5.1@Mg2Al—NO3 LDH-A
HY5.1 (100 mg) was dispersed in deionised water (20 mL) using ultrasound treatment. After 36 minutes, an aqueous solution (19.2 mL) containing magnesium nitrate hexahydrate and aluminium nitrate nonahydrate was added at a rate of 60 mL/h to HY5.1 solution under vigour stirring. The pH of the reaction solution was controlled to 10 with the addition of 1 M NaOH by an autotitrator. The obtained suspension was stirred for 1 h. The obtained solid was collected and then re-dispersed in deionised water (40 mL) and stirred for 1 h. The collection and re-dispersion was repeated once. The solid was treated with AMOST method, which was washed with acetone (40 mL) and then re-dispersed in a fresh acetone (40 mL) under stirring for overnight. The solid was then dried under vacuum oven for materials characterization.
Characterisation
HY5.1@Mg2Al—NO3 LDH
The same synthesis method is applied to LDH-NO3. The TEM (
Variation of the Metal of the LDH
Example Method of HY5.1@ Mg2Al0.8Fe0.2—CO3 LDH-A
HY5.1 (100 mg) was dispersed in deionised water (20 mL) using ultrasound treatment. After 36 minutes, an aqueous solution (19.2 mL) containing magnesium nitrate hexahydrate, iron nitrate nonahydrate and aluminium nitrate nonahydrate (Mg:Al:Fe 2:0.8:0.2) was added at a rate of 60 mL/h to HY5.1 solution under vigour stirring. The pH of the reaction solution was controlled to 10 with the addition of 1 M NaOH by an autotitrator. The obtained suspension was stirred for 1 h. The obtained solid was collected and then re-dispersed in deionised water (40 mL) and stirred for 1 h. The collection and re-dispersion was repeated once. The solid was treated with AMOST method, which was washed with acetone (40 mL) and then re-dispersed in a fresh acetone (40 mL) under stirring for overnight. The solid was then dried under vacuum oven for materials characterization.
HY5.1@Mg2Al0.8Fe0.2—CO3 LDH
The TEM (
Example Method of HY5.1@ Mg1.8AlNi0.2—CO3 LDH-A
HY5.1 (100 mg) was dispersed in deionised water (20 mL) using ultrasound treatment. After 36 minutes, an aqueous solution (19.2 mL) containing magnesium nitrate hexahydrate, nickel nitrate hexahydrate and aluminium nitrate nonahydrate (Mg:Al:Ni 1.8:1:0.2) was added at a rate of 60 mL/h to HY5.1 solution under vigour stirring. The pH of the reaction solution was controlled to 10 with the addition of 1 M NaOH by an autotitrator. The obtained suspension was stirred for 1h. The obtained solid was collected and then re-dispersed in deionised water (40 mL) and stirred for 1 h. The collection and re-dispersion was repeated once. The solid was treated with AMOST method, which was washed with acetone (40 mL) and then re-dispersed in a fresh acetone (40 mL) under stirring for overnight. The solid was then dried under vacuum oven for materials characterization.
Characterisation
HY5.1@Mg1.8AlNi0.2—CO3 LDH
The TEM (
Mesoporous Silica Based Materials
Example Method of MSN@ Mg3Al—CO3 LDH
Generally, MCM-41 (50 mg) was dispersed in deionised water (20 mL) using ultrasound treatment. After 30 minutes, the sodium carbonate was added to the solution and a further 6 minutes of sonication was carried out to form solution A. An aqueous solution (19.2 mL) containing magnesium nitrate hexahydrate and aluminium nitrate nonahydrate was added at a rate of 60 mL/h to solution A under vigorous stirring. The pH of the reaction solution was controlled with the addition of 1 M NaOH by an autotitrator. The obtained suspension was stirred for 1 h. The obtained solid was collected and then re-dispersed in deionised water (40 mL) and stirred for 1 h. The collection and re-dispersion was repeated once. Before final isolation, the solid was treated with AMOST method, which was washed with acetone (40 mL) and then re-dispersed in acetone (40 mL) under stirring for overnight. The samples (MCM-41@AMO-LDH) were then dried under vacuum. The other MSN@AMO-LDH (such as SBA-15@AMO-LDH) was synthesized using the same procedure.
Characterisation
MSN@Mg3Al—CO3 LDH
According to X-ray diffraction (XRD) pattern (
Microporous Molecular Sieves @ LDH
Example Method of ALPO-5/SAPO-5@LDH
Generally, ALPO-5(100 mg) was dispersed in deionised water (20 mL) using ultrasound treatment. After 30 minutes, the sodium carbonate was added to the solution and a further 6 minutes of sonication was carried out to form solution A. An aqueous solution (19.2 mL) containing magnesium nitrate hexahydrate and aluminium nitrate nonahydrate was added at a rate of 60 mL/h to solution A under vigorous stirring. The pH of the reaction solution was controlled with the addition of 1 M NaOH by an autotitrator. The obtained suspension was stirred for 1 h. The collection and re-dispersion was repeated once. Before final isolation, the solid was treated with AMOST method, which was washed with acetone (40 mL) and then re-dispersed in acetone (40 mL) under stirring for overnight. The samples (ALPO-5@AMO-LDH) were then dried under vacuum. The SAPO-5@AMO-LDH was synthesized using the same procedure.
SAPO5@Mg3Al—CO3 LDH & ALPO5@Mg3Al—CO3 LDH
XRD (
Polymerisation of Ethylene Using Zeolite@LDH
Synthesis of ZSM5-23/MAO and ZSM5-23@LDH/MAO
A sample of ZSM5-23@LDH, prepared as described above, was thermally treated at 150° C. for 6 h before being reacted with methylaluminoxane (MAO) in a 2:1 ratio (support:MAO) in toluene at 80° C. for 2 h. The solvent was removed under vacuum to give ZSM5-23@LDH/MAO as a free-flowing colourless powder.
A sample of the zeolite ZSM5-23 was also thermally treated and then reacted with MAO, according to the procedure described above. Following removal of the solvent, the solid product ZSM5-23/MAO was obtained.
Synthesis of Catalysts Based on ZSM5-23
The ZSM5-23@LDH/MAO, obtained as described above, was reacted with rac-(EBI)ZrCl2 in a 200:1 ratio (support/MAO:(EBI)ZrCl2) in toluene. The reaction was carried out at 60° C. for 1 h. After removing the solvent, the beige solid product ZSM5-23@LDH/MAO/(EBI)ZrCl2 was obtained. The same process was carried out with the ZSM5-23/MAO to give ZSM5-23/MAO/(EBI)ZrCl2. In addition, the same process was carried out using, as support, LDH/MAO to give the product LDH/MAO/(EBI)ZrCl2.
Ethylene Polymerisation Studies
The catalysts were tested for their ability to act as a catalyst for ethylene polymerisation under slurry conditions in the presence of TIBA (TIBA)0/[Zr]0=1000). The reactions were performed with ethylene (2 bar) in a 200 mL ampoule, with the catalyst precursor (10 mg) suspended in hexane (50 mL). The reactions were run for 15-120 minutes at 50-90° C. controlled by heating in an oil bath. The polyethylene product was washed with pentane (3×50 mL) and the resulting polyethylene was filtered through a sintered glass frit.
The polymerisation activity of the catalyst supported metallocene complexes plotted against temperature is shown in
Catalysts were also produced using the zeolite HY5.1 according to the processes described above. Each of these catalysts, HY5.1@LDH/MAO/(EBI)ZrCl2, LDH/MAO/(EBI)ZrCl2 and pure HY5.1/MA0/(EBI)ZrCl2, was also tested for its ability to act as a catalyst for ethylene polymerisation as described above. The polymerisation activities of these plotted against temperature are shown in
The features disclosed in the foregoing description, in the claims and in the accompanying drawings may, both separately and in any combination, be material for realising the invention in diverse forms thereof.
While specific embodiments of the invention have been described herein for the purpose of reference and illustration, various modifications will be apparent to a person skilled in the art without departing from the scope of the invention as defined by the appended claims
| Number | Date | Country | Kind |
|---|---|---|---|
| 1512452.2 | Jul 2015 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2016/052160 | 7/15/2016 | WO | 00 |
