Patent Application
20150329790
The invention relates to systems and methods for treating or upgrading heavy oil feeds and crude products produced using such systems and methods.
The petroleum industry is increasingly turning to heavy crudes, resids, coals and tar sands as sources for feedstocks. Feedstocks derived from these heavy materials contain more sulfur and nitrogen than feedstocks derived from more conventional crude oils, requiring a considerable amount of upgrading in order to obtain usable products. These heavier and higher sulfur crudes and resids also present problems as they invariably contain much higher metal contaminants such as nickel, vanadium and iron, which represent operating problems in terms of metal deposit/build-up in the equipment.
There is still a need for improved systems and methods to upgrade/treat heavy oil feeds.
In one aspect, the invention relates to process for upgrading a heavy oil feedstock, the process comprising: (a) contacting a heavy oil feedstock and a hydrogen-containing gas with at least one supported catalyst under hydrocracking conditions in a first contacting zone consisting of one or more ebullated bed reactors to convert at least a portion of the heavy oil feedstock to upgraded products comprising lower boiling hydrocarbons and form a first effluent comprising the upgraded products, the hydrogen-containing gas, and an unconverted portion of the heavy oil feedstock; (b) sending the first effluent to a first separation zone, whereby the upgraded products are separated with the hydrogen-containing gas as an overhead stream, and the unconverted portion of the heavy oil feedstock is separated as a first non-volatile stream; (c) contacting at least a portion of the first non-volatile stream with a slurry catalyst and an additional hydrogen-containing gas feed under hydrocracking conditions in a second contacting zone consisting of one or more slurry phase reactors to convert at least a portion of the unconverted portion of the heavy oil feedstock to lower boiling hydrocarbons to additional upgraded products comprising lower boiling hydrocarbons and form a second effluent comprising additional upgraded products, additional hydrogen-containing gas, the slurry catalyst and an unconverted portion of the heavy oil feedstock; and (d) sending the second effluent to a second separation zone, whereby the additional upgraded products are removed with the additional hydrogen-containing gas as an overhead stream, and the slurry catalyst and the unconverted heavy oil feedstock are removed as a second non-volatile stream.
In another aspect, the invention relates to process for upgrading a heavy oil feedstock, the process comprising: (a) contacting a heavy oil feedstock and a hydrogen-containing gas with at least one supported catalyst under hydrocracking conditions in a first contacting zone consisting of one or more ebullated bed reactors to convert at least a portion of the heavy oil feedstock to upgraded products comprising lower boiling hydrocarbons and form a first effluent comprising the upgraded products, hydrogen-containing gas, and an unconverted portion of the heavy oil feedstock; (b) contacting at least a portion of the first effluent with a slurry catalyst and an additional hydrogen-containing gas feed under hydrocracking conditions in a second contacting zone consisting of one or more slurry phase reactors to convert at least a portion of the unconverted portion of the heavy oil feedstock to additional upgraded products comprising lower boiling hydrocarbons and form a second effluent comprising additional upgraded products, hydrogen-containing gas, and an unconverted portion of the heavy oil feedstock; and (c) sending the second effluent to a separation zone, whereby volatile upgraded products are removed with the hydrogen-containing gas as an overhead stream, and the slurry catalyst and the unconverted heavy oil feedstock are removed as a non-volatile stream.
The present invention relates to an improved system to treat or upgrade heavy oil feeds.
The following terms will be used throughout the specification and will have the following meanings unless otherwise indicated.
“Heavy oil” feed or feedstock refers to heavy and ultra-heavy crudes, including but not limited to resids, coals, bitumen, tar sands, oils obtained from the thermo-decomposition of waste products, polymers, biomasses, oils deriving from coke and oil shales, etc. Heavy oil feedstock can be liquid, semi-solid, and/or solid. Examples of heavy oil feedstock include, but are not limited to, Canada tar sands and vacuum residuum from the Brazilian Santos and Campos basins, the Egyptian Gulf of Suez, Chad, Venezuelan Zulia, Malaysia, or Indonesia Sumatra. Other examples of heavy oil feedstock include residuum left over from refinery processes, including “bottom of the barrel” and “residuum” (or “resid”), atmospheric tower bottoms, which have a boiling point of at least 650° F. (343° C.), or vacuum tower bottoms, which have a boiling point of at least 975° F. (524° C.), or “resid pitch” and “vacuum residue” which have a boiling point of 975° F. (524° C.) or greater.
Properties of heavy oil feedstock can include, but are not limited to, a total acid number (TAN) of at least 0.1 mg KOH/g (e.g., at least 0.3 mg KOH/g, or at least 1 mg KOH/g); a viscosity of at least 10 mm2/s; an API gravity of at most 15 (e.g., at most 10). In one embodiment, a gram of heavy oil feedstock contains at least 0.0001 g of Ni/V/Fe; at least 0.005 g of heteroatoms; at least 0.01 g of residue; at least 0.04 g of C5 asphaltenes; at least 0.002 g of micro-carbon residue/g of crude; at least 0.00001 g of alkali metal salts of one or more organic acids; and at least 0.005 g of sulfur. In one embodiment, the heavy oil feedstock has a sulfur content of at least 5 wt. % and an API gravity ranging from −5 to +5. A heavy oil feed such as Athabasca bitumen (Canada) typically has at least 50% by volume vacuum residue. In one embodiment, the heavy oil feedstock contains at least 100 ppm of vanadium/g of heavy oil feedstock.
“Treatment,” “treated,” “upgrade,” “upgrading” and “upgraded,” when used in conjunction with a heavy oil feedstock, describes a heavy oil feedstock that is being or has been subjected to hydroprocessing, or a resulting material or crude product, having a reduction in the molecular weight of the heavy oil feedstock, a reduction in the boiling point range of the heavy oil feedstock, a reduction in the concentration of asphaltenes, a reduction in the concentration of hydrocarbon free radicals, and/or a reduction in the quantity of impurities, such as sulfur, nitrogen, oxygen, halides, and metals.
The upgrade or treatment of heavy oil feeds is generally referred herein as “hydroprocessing” (hydrocracking or hydroconversion). Hydroprocessing is meant as any catalytic process that is carried out in the presence of hydrogen, including, but not limited to, hydroconversion, hydrocracking, hydrogenation, hydrotreating, hydrodesulfurization, hydrodenitrogenation, hydrodemetallation, hydrodearomatization, hydroisomerization, hydrodewaxing and hydrocracking including selective hydrocracking. The products of hydroprocessing can show improved viscosities, viscosity indices, saturates content, low temperature properties, volatilities and depolarization, etc.
“Hydrocracking” refers to a catalytic process whose primary purpose is to reduce the boiling range of a heavy oil feedstock and in which a substantial portion of the feedstock is converted into products with boiling ranges lower than that of the original feedstock. Hydrocracking generally involves fragmentation of larger hydrocarbon molecules into smaller molecular fragments having a fewer number of carbon atoms and a higher hydrogen-to-carbon ratio. The mechanism by which hydrocracking occurs typically involves the formation of hydrocarbon free radicals during fragmentation followed by capping of the free radical ends or moieties with hydrogen. The hydrogen atoms or radicals that react with hydrocarbon free radicals during hydrocracking are generated at or by active catalyst sites.
“Hydrogen” refers to hydrogen, and/or a compound or compounds that when in the presence of a heavy oil feed and a catalyst react to provide hydrogen.
“Supported catalyst” refers to a catalyst that is affixed onto a shaped/preformed solid (“a carrier” or a support) comprising any of alumina, silica, magnesia, titania, aluminosilicates, aluminophosphates, carbon, porous metals, and combinations thereof. The catalyst is affixed onto the support via methods including, but not limited to, impregnation or deposition.
“Slurry catalyst” (or sometimes referred to as “slurry” or “dispersed catalyst”) refers to a liquid medium, e.g., oil, water, or mixtures thereof, in which catalyst and/or catalyst precursor particles (aggregates, particulates or crystallites) are dispersed within. The term slurry catalyst refers to a fresh catalyst, or a catalyst that has been used in heavy oil upgrading and with diminished activity (“used catalyst”). For example, if a reaction rate constant of a fresh catalyst at a specific temperature is assumed to be 100%, the reaction rate constant for a used catalyst is 95% or less e.g., 80% or less, or 70% or less. The term “used catalyst” herein can be used interchangeably with “recycled catalyst,” “used slurry catalyst” or “recycled slurry catalyst.”
“Contacting zone” refers to an equipment in which the heavy oil feed is treated or upgraded by contact with a catalyst in the presence of hydrogen. In a contacting zone, at least a property of the crude feed can be changed or upgraded. The contacting zone can be a reactor, a portion of a reactor, multiple portions of a reactor, or combinations thereof. The term “contacting zone” can be used interchangeably with “reaction zone.”
“Separation zone” refers to an equipment in which an effluent stream from a contacting zone is either fed directly into or subjected to one or more intermediate processes and then fed directly into the separation zone, which is a high pressure high temperature flash drum or flash separator, wherein gases and volatile liquids are separated from the non-volatile fraction. The separation zone, in one embodiment, refers to an interstage flash separator (“ISF”) if it is located between two contacting zones. In one embodiment, the term “separating zone” refers to a plurality of separators in series, e.g., one separator operated at high pressure followed by another separator operated at a lower pressure. As used herein, high pressure as referring to a separation zone means a pressure of at least 1000 psi (6.9 MPa), e.g., from 1000 to 3000 psi (6.9 to 20.7 MPa). Medium pressure refers to a pressure of from 200 to less than 1000 psi (1.4 to less than 6.9 MPa), e.g., from 200 to 800 psi (1.4 to 5.5 psi). Low pressure means less than 200 psi (1.4 MPa). With respect to operating temperatures, a high temperature means greater than 600° F. (316° C.), e.g., from 650° F. to 850° F. (343° C. to 454° C.). A medium temperature means that the separation zone operates at 400° F. to 600° F. (204° C. to 316° C.). A low temperature means from 100° F. to 300° F. (38° C. to 149° C.).
As used herein, the numbering scheme for the Periodic Table Groups is as disclosed in Chem. Eng. News, 63(5), 27 (1985).
Ebullated Bed Reactor Conversion Zone
In one embodiment, the upgrade process employs a plurality of contacting zones. The first contacting zone consists of one or more ebullated bed reactors in series and/or parallel. In the case of reactors in series, one or more separators can be present on the overhead effluent from each of the reactors. In one embodiment, the first contacting zone consists of only a single ebullated bed reactor.
In general, an ebullated bed reactor includes concurrently flowing streams of liquids or slurries of liquids, solids and gas, through a vertically-oriented cylindrical vessel containing catalyst. The supported catalyst is placed in motion in the liquid and has a gross volume dispersed through the liquid medium that is greater than the volume of the mass when stationary. In an ebullated bed reactor, the catalyst is in an expanded bed, thereby countering plugging problems associated with conventional fixed-bed reactors. The fluidized nature of the catalyst in an ebullated bed reactor also allows for on-line catalyst replacement of a small portion of the bed. This results in a high net bed activity which does not vary with time.
Suitable catalysts used in ebullated bed hydroprocessing systems typically comprise at least one Group VIII metal (e.g., Ni and/or Co) most often in combination with at least one Group VIB metal (e.g., Mo) on a refractory inorganic oxide support such as alumina or silica. The supported catalysts generally contain from 0.5 to 10 wt. % of at least one Group VIII metal (calculated as metal oxide) and from 1 to 30 wt. % of the at least one Group VIB metal (calculated as metal oxide). The supported catalysts are commonly produced as cylindrical pellets, spherical solids, or extrudates.
Most of the metals (e.g., V, Ni, etc.) in the feed are converted and adsorbed on the ebullated bed catalyst in the first reactor and can be removed from the upgrade system during catalyst replacement, thereby minimizing metal deposition on the process equipment (walls, internals, etc.). In one embodiment, the first contacting zone provides for a vanadium conversion of at least 50% (e.g., at least 70%, or at least 80%) and a nickel conversion of at least 40%.
In one embodiment, no more than 70% (e.g., from 30 to 70%, or from 50 to 65%) of heavy oil feed is converted to lighter products in the first conversion zone. As used herein, “conversion” refers to the conversion of heavy oil feedstock to less than 1000° F. (538° C.) boiling point materials.
Slurry Phase Reactor Conversion Zone
The second contacting zone consists of one or more slurry phase reactors in series and/or parallel. In one embodiment, the second contacting zone consists of only a single slurry phase reactor. In another embodiment, the second contacting zone consists of two slurry phase reactor in series.
In a slurry phase reactor, the heavy oil feed stream is mixed with a stream of hydrogen and a slurry catalyst which is as dispersed as possible in order to obtain a hydrogenating activity which is also as uniformly distributed as possible in the hydroconversion reaction zone. This mixture supplies the catalytic slurry hydroconversion section. This section is constituted by a preheating furnace for the feedstock and hydrogen and by a reaction section constituted by one or more reactors disposed in series and/or in parallel, depending on the capacity required. In the case of slurry phase reactors in series, one or more separators can be present on the overhead effluent from each of the reactors. In the reaction section, the hydrogen can supply a single, some or all of the reactors, in equal or different proportions. In the reaction section, the slurry catalyst can supply a single, some or all of the reactors, in equal or different proportions. The slurry catalyst is maintained in suspension in the slurry reactor, moves from the bottom to the top of the reactor with the gas and the feedstock and is evacuated with the effluent. Preferably, at least one (preferably all) of the slurry phase reactors is provided with a recirculating pump which can be either internal or external to the reactor.
Slurry phase reactors can be operated at higher temperatures than ebullated bed reactors, thereby achieving higher conversion. In one embodiment, up to 95% of heavy oil feed is converted to lighter product in the second conversion zone. In another embodiment, up to 90% of heavy oil is converted to lighter product in the second conversion zone. In a third embodiment, up to 85% of heavy oil is converted to lighter product in the second conversion zone.
The slurry catalyst is in the dispersed form in the reaction medium. It can be formed in situ, but it is preferable to prepare it outside the slurry reactor and inject it continuously with the feedstock. The catalyst promotes the hydrogenation of free radicals obtained from thermal cracking and reduces the formation of coke. When coke is formed, it is evacuated with the catalyst.
The slurry catalyst comprises an active catalyst in a hydrocarbon oil diluent. In one embodiment, the slurry catalyst is a sulfided catalyst comprising at least one Group VIB metal, or at least one Group VIII metal, or at least one Group IIB metal, e.g., a molybdenum sulfide, an iron sulfide, a nickel sulfide, a zinc sulfide, or an iron zinc catalyst.
In one embodiment, the slurry catalyst is a multi-metallic catalyst comprising at least one Group VIII non-noble metal and at least two Group VIB metals, and wherein the ratio of the at least two Group VIB metals to the Group VIII non-noble metal is from 10:1 to 1:10.
In one embodiment, the slurry catalyst is of the formula (Mt)a(Xu)b(Sv)d(Cw)e(Hx)f(Oy)g(Nz)h, wherein M represents at least one Group VIB metal, such as Mo, W, etc. or a combination thereof, and X functions as a promoter metal, representing at least one of a non-noble Group VIII metal such as Fe, Ni, Co; a Group IVB metal such as Ti; a Group JIB metal such as Zn; and combinations thereof (X is hereinafter referred to as “Promoter Metal”). Also in the equation, superscripts t, u, v, w, x, y, and z represent the total charge for each of the components M, X, S, C, H, O and N, respectively; and (ta+ub+vd+we+xf+yg+zh)=0. The subscript ratio of b to a has a value of from 0 to 5 (0≦b/a≦5). S represents sulfur with subscript d having a value of from (a+0.5b) to (5a+2b). C represents carbon with subscript e having a value of from 0 to 11(a+b). H is hydrogen with subscript f having a value of from 0 to 7(a+b). O represents oxygen with the value of subscript g having a value of from 0 to 5(a+b). N represents nitrogen with subscript h having a value of 0 to 0.5(a+b). In one embodiment, subscript b has a value of 0, for a single metallic component catalyst, e.g., a Mo only catalyst (no promoter).
In one embodiment, the slurry catalyst is prepared from catalyst precursor compositions including organometallic complexes or compounds, e.g., oil soluble compounds or complexes of transition metals and organic acids. Examples of such compounds include naphthenates, pentanedionates, octoates, and acetates of Group VIB and Group VIII metals. In another embodiment, the slurry catalyst is prepared from grinded or recovered supported hydroprocessing catalyst powder in oil.
In one embodiment, the slurry catalyst has an average particle size of at least 1 micron in a hydrocarbon oil diluent. In one embodiment, the slurry catalyst has an average particle size of from 1 to 20 microns, e.g., from 2 to 10 microns. In one embodiment, the slurry catalyst particle comprises aggregates of catalyst molecules and/or extremely small particles that are colloidal in size (i.e., less than 100 nm, less than about 10 nm, less than about 5 nm, or less than about 1 nm). In one embodiment, the slurry catalyst comprises aggregates of single layer MoS2 clusters of nanometer sizes, e.g., 5 to 10 nm on edge. In operations, the colloidal/nanometer sized particles aggregate in a hydrocarbon diluent forming a slurry catalyst with an average particle size of from 1 to 20 microns.
In one embodiment, a sufficient amount of slurry catalyst is fed to the slurry phase reactor(s) for each reactor to have a slurry catalyst concentration of from 300 wppm to 3 wt. % (catalyst metal to heavy oil ratio).
The slurry catalyst feed used herein can comprise one or more different slurry catalysts as a single feed stream or as separate feed streams.
In one embodiment, the slurry catalyst feed is first pre-conditioned before entering the contacting zone(s), or before being brought into contact with the heavy oil feed before entering the contacting zone(s). It is believed that instead of contacting the cold catalyst with the heavy oil feed, pre-conditioning helps with hydrogen adsorption into the active catalyst sites and, ultimately, improves the conversion rate. In one embodiment, operating conditions in the pre-conditioning unit can include a temperature of from 300° F. to 1000° F. (149° C. to 538° C.), a pressure of from 300 to 3200 psi (2.1 to 22.1 MPa), and hydrogen gas rate of from 500 to 8000 SCF/B (89 to 1425 m3/m3).
In one embodiment, the upgrade system operates in “once-through” mode, wherein the heavy oil feedstock flows through the contacting zones once instead of being recycled or recirculated around the system. In the once-through mode, the non-volatile materials from the last separation zone in the upgrade system, comprising unconverted materials, heavier hydrocracked liquid products (synthetic products or non-volatile/less volatile upgraded products), slurry catalyst, small amounts of coke, asphaltenes, etc., are sent off-site for further processing/regeneration of the slurry catalyst, or sent to a deoiling unit to separate the spent slurry catalyst from the hydrocarbons subsequently to a metal recovery unit to recover precious metals from the spent slurry catalyst.
In one embodiment, the upgrade system operates in “recycled” mode, wherein at least a portion of the non-volatile materials from the last separation zone in the upgrade system is recycled to at least one of the contacting zones as part of the feed. Depending on the final heavy oil upgrade conversion, the amount of recycled stream can range from 2 to 50 wt. % (e.g., from 3 to 25 wt. %, or from 5 to 15 wt. %) of the heavy oil feed to the system. In the recycled mode, at least a portion of the non-volatile materials from the last separation zone is removed as a bleed stream. The bleed stream can range from 1 to 50 wt. % (e.g., from 3 to 35 wt. %, or from 5 to 20 wt. %) of total heavy oil feed to the system. The amount of bleed stream removed can vary depending on the operating conditions, e.g., conversion rate and time in operation. In one embodiment the bleed stream contains an amount of slurry catalyst ranging from 1 to 15 wt. % in concentration.
Optional Additional Hydrocarbon Feed
In one embodiment, additional hydrocarbon oil feed, e.g., vacuum gas oil (VGO), heavy cycle oil (HCO), medium cycle oil (MCO), light cycle oil (LCO), naphtha, solvent donor, or other aromatic solvents can be optionally added (e.g., in an amount of from 2 to 40 wt. % of the heavy oil feed) as part of the heavy oil feed stream to any of the contacting zones in the system. In one embodiment, the additional hydrocarbon feed functions as a diluent to lower the viscosity of the heavy oil feed.
Process Conditions
In one embodiment, the upgrade system is maintained under hydrocracking conditions, e.g., at a minimum temperature to effect hydrocracking of a heavy oil feedstock.
Hydrocracking in the first contacting zone can be carried out at a temperature of from 752° F. to 1112° F. (400° C. to 600° C.), a hydrogen partial pressure of from 250 to 5000 psig (1.8 to 34.6 MPa), a liquid hourly space velocity (LHSV) of from 0.1 to 10 h−1, and a hydrogen treat gas rate of from 200 to 10,000 SCF/B (35.6 to 1781 m3/m3). Typically, in most cases, the conditions will include a temperature of from 752° F. to 932° F. (400° C. to 500° C.), a hydrogen partial pressure of from 500 to 2500 psig (3.5 to 17.2 MPa), a LHSV of from 0.1 to 2 h−1, and a hydrogen treat gas rate of from 1200 to 6000 SCF/B (213 to 1068 m3/m3).
The operating conditions in the second contacting zone can be similar to those used in the first contacting zone, or the process conditions can be different. In one embodiment, the process conditions in the second hydrocracking zone can be more severe than the hydrocracking conditions in the first contacting zone. In one embodiment, the temperature in the second contacting zone process is 10° F. to 50° F. more (e.g., 15° F. to 50° F. more, 20° F. to 50° F. more, 25° F. to 50° F. more, 30° F. to 50° F. more, 40° F. to 50° F. more, 15° F. to 40° F. more, 20° F. to 40° F. more, or 25° F. to 40° F. more) than the temperature in the first contacting zone process.
In one embodiment, each contacting zone comprises a single reactor or a plurality of reactors in series, providing a total residence time of from 0.1 to 15 hours, e.g., from 0.5 to 5 hours, or from 0.2 to 2 hours.
System Performance
In one embodiment, at least 75 wt. % (at least 85 wt. %, at least 95%, or at least 98%) of heavy oil feed is converted to lighter products in a high throughput one pass process.
In one embodiment, the upgrade system provides a sulfur conversion rate of at least 60% (e.g., at least 75%), a nitrogen conversion of at least 20%, and a Micro-Carbon Residuum (MCR) conversion of at least 50% (e.g., at least 60%, or at least 70%), a vanadium conversion of at least 80% (e.g., at least 90%, or at least 95%) and a nickel conversion of at least 70%, for a slurry catalyst concentration of from 300 to 5000 wppm catalyst metal.
Depending on the conditions and location of the separation zone, in one embodiment, the amount of heavier hydrocracked products in the non-volatile fraction stream is less than 50 wt. % (e.g., less than 25 wt. %, or less than 15 wt. %) of the total weight of the non-volatile stream. The solid level in the residue stream can be less than 40 wt. % solid (e.g., less than 25 wt. % solid, from 1 to 10 wt. % solid, or from 2 to 5 wt. % solid).
In one embodiment, the upgrade system produces a volume yield of least 103% (compared to the heavy oil input) in upgraded products as added hydrogen expands the heavy oil total volume. The upgraded products, i.e., lower boiling hydrocarbons, in one embodiment include liquefied petroleum gas (LPG), gasoline, diesel, vacuum gas oil (VGO), and jet and fuel oils. In a second embodiment, the upgrade system provides a volume yield of at least 110% in upgraded products.
Process Flow Scheme
A variety of process flow schemes are available according to various embodiments of the invention.
First, a heavy oil feedstock 104 is introduced into the first hydrocracking reaction zone in the system together with hydrogen-containing gas stream 121 via conduit 122. The heavy oil feedstock can be preheated in a heater prior to feeding into the first hydrocracking reaction zone. The feedstock is hydroprocessed in the presence of one or more supported catalyst beds under effective conditions. Additional hydrocarbon oil feed 105, e.g., vacuum gas oil (VGO), decant oil (DCO), heavy cycle oil (HCO), medium cycle oil (MCO), naphtha, etc. in an amount of from 2 to 30 wt. % of the heavy oil feed can be optionally added as part of the feed stream to any of the hydrocracking reaction zones in the system.
In one embodiment, effluent stream 123 comprising upgraded materials, unconverted heavy oil feed, hydrogen, etc. is withdrawn from the first hydrocracking reaction zone 120 and sent to separation zone 130 (e.g., an interstage flash separator or ISF). The separation zone 130 causes or allows the separation gas and volatile liquids from the non-volatile fractions.
In one embodiment (shown in dotted lines with optional by-pass), the effluent stream 123 is introduced directly into the second hydrocracking reaction zone 140 together with a slurry catalyst feed 145 without the need for the separation zone 130.
Target conversion in the first hydrocracking reaction zone 120 can range from 30 to 70 wt. %, depending on the feedstock being processed. However, conversion should be maintained below a level wherein sediment formation becomes excessive.
In the embodiment with the use of separation zone 130, the gaseous and volatile liquid fractions 131 are withdrawn from the top of separation zone 130 and taken for further processing in a lean contactor or a downstream process 160. The bottom stream 133, comprising unconverted heavy oil feedstock, newly generated non-volatile hydrocarbons, etc. is withdrawn and introduced into the second hydrocracking reaction zone 140 in the system together with a slurry catalyst feed 145. Additional hydrogen 141 can be introduced together with the bottom stream/slurry catalyst in the same conduit 222 as shown, or optionally, as a separate feed stream. The stream is hydroprocessed under effective conditions. Effluent stream 142 comprising upgraded materials along with slurry catalyst, hydrogen, coke, unconverted heavy oil, etc. flows to the next separation zone 150 for separation of gases and volatile liquids 151 from the non-volatile fractions. The gaseous and volatile fractions 151 are withdrawn from the top of the separation zone and combined with the gaseous and liquid fractions from a preceding separation zone as stream 161 for further processing in a hydrotreatment system 160 or downstream product purification system. In one embodiment (not shown), stream 161 is quenched with a hydrocarbon stream such as light gas oil (LGO) in a lean oil contactor. In one embodiment, the non-volatile (or less volatile) fraction stream (comprising, e.g., slurry catalyst, unconverted oil containing coke and asphaltenes, heavier hydrocracked liquid products, optional sacrificial material, etc.) is collected as residue stream 152 and sent to a downstream process for deoiling and/or metal recovery in a metal recovery unit. In one embodiment, a portion of the residue 152 is sent to at least one of the hydrocracking reaction zones as recycled feed stream 152 (shown in dotted lines).
Target conversion exiting the second hydrocracking reaction zone 140 can range from 50 to 95 wt. %, depending on the feedstock being processed.
The hydrotreater 160, in one embodiment, employs conventional hydrotreating catalysts and is operated at similarly high pressure (e.g., within 50 psig) as the rest of the upgrade system. The hydrotreater is capable of removing sulfur, nitrogen and other impurities from the upgraded products with hydrodenitrogenation (HDN) conversion level of greater than 99%, lowering the sulfur level fractions above 70° F. (21° C.) boiling point in stream 162 to less than 20 ppm (e.g., less than 10 ppm).
The following illustrative examples are intended to be non-limiting.
A vacuum residuum (VR) feedstock having the properties in Table 1 was hydroprocessed in a once-through microunit equipped with two 1-L continuously stirred tank reactors connected in series. The first reactor served as an ebullated bed reactor with a hydroprocessing catalyst, while the second reactor was a slurry reactor. A few percent of diluent, e.g., cycle oil, was also injected together with VR.
The hydroprocessing catalyst in the ebullated bed reactor contained about 4.3 wt. % MoO3, 0.5 wt. % NiO and balanced with Al2O3. The surface area and total pore volume of the catalyst were 188 m2/g and 0.73 cm3/g, respectively.
The slurry catalyst in the slurry reactor was prepared according to the teaching of U.S. Patent Application Publication No. 2006/0058174, e.g., a Mo compound was first mixed with aqueous ammonia forming an aqueous Mo compound mixture, sulfided with a sulfur-containing compound, promoted with a Ni compound, then transformed in a hydrocarbon oil, e.g., VGO, at a temperature of at least 350° F. and a pressure of at least 200 psig, forming an active slurry catalyst.
Table 2 summarizes the performance of the ebullated bed/slurry dual operation process at various temperatures and catalyst dosages.
Example 1 shows that the sediment in the slurry liquid filtrate (SLF) was low. Increasing the slurry reactor temperature to 825° F. (average reactor temperature of 808° F.) in Example 2 increased the VR (1075° F.+) conversion to 89.4%. Decreasing the slurry catalyst dosage to 841 ppm Mo/VR in Example 3 resulted in only a slight decrease in catalytic conversion while the cracking conversion, whole liquid product (WLP) API and coke-make did not change significantly. By further increasing the average reactor temperature to 815° F. as in Example 4, the VR (1075° F.+) conversion can be further increased to 91.5%. Further reducing the slurry catalyst dosage to 583 ppm Mo/VR (Example 5) and 473 ppm Mo/VR (Example 6), high VR conversion (90.9% and 92.4%, respectively) was maintained with good WLP API and low coke-make.
For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained. It is noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the,” include plural references unless expressly and unequivocally limited to one referent. As used herein, the term “include” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items. As used herein, the term “comprising” means including elements or steps that are identified following that term, but any such elements or steps are not exhaustive, and an embodiment can include other elements or steps.
Unless otherwise specified, the recitation of a genus of elements, materials or other components, from which an individual component or mixture of components can be selected, is intended to include all possible sub-generic combinations of the listed components and mixtures thereof.
The patentable scope is defined by the claims, and can include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. To an extent not inconsistent herewith, all citations referred to herein are hereby incorporated by reference.
