Process for decomposition into light olefins accompanied by isomerization

Abstract

A process for the catalytic production of olefins comprises the steps of delivering an n-paraffin-rich stream to an isomerization unit to provide a first hydrocarbon stream rich in iso-paraffin, and contacting the first hydrocarbon stream with a stream of a first flow catalyst in a first reactor riser to produce a first mixture of spent catalyst and product gas. The process comprises the step of separating the first mixture of spent catalyst and product gas into a first cracking product stream and a first cooling catalyst stream in a first separation vessel. The process comprises the steps of contacting a second hydrocarbon stream with a stream of a second flow catalyst in a second reactor riser to produce a second mixture of spent catalyst and product gas; and separating the second mixture of spent catalyst and product gas in a second separation vessel to provide a second cracking product stream and a second cooling catalyst stream. The first cracking product stream and the second cracking product stream are delivered upward through a gas recovery conduit and further separated from the catalyst in a series of cyclones to produce a high-temperature product stream.

Description

Technology Field

[0001] Priority statement

[0002] This application claims priority to U.S. provisional patent application No. 63 / 614,347 filed on December 22, 2023, the entirety of which is incorporated herein by reference.

[0003] Technology field

[0004] This field relates to reacting a feed with a flow catalyst. In particular, this field relates to an FCC process for producing light olefins using a dual reactor system. Background Technology

[0005] Catalytic cracking can produce various products from a wide range of hydrocarbons. Typically, a feed of heavy hydrocarbons, such as vacuum gas oil, is supplied to a catalytic cracking reactor, such as a fluid catalytic cracking (FCC) reactor. Various products, including gasoline products and / or light products (e.g., propylene and / or ethylene), can be produced from the FCC unit.

[0006] In an FCC system, a single reactor or a dual reactor may be used. While using a dual reactor system may incur additional capital costs, one of the reactors can be operated to adjust conditions to maximize products such as light olefins including propylene and / or ethylene.

[0007] It is generally advantageous to maximize the product yield and minimize dry gas formation within a single reactor. Additionally, there may be a need to maximize the production of a product from a single reactor that can be recirculated to another reactor to produce a desired product, such as propylene.

[0008] Therefore, there may be a need to provide an efficient reactor process for catalytic decomposition to maximize propylene products and minimize dry gas formations.

[0009] A process for the catalytic production of olefins comprises the step of contacting a first hydrocarbon stream in a first riser with a stream of a first flow catalyst to produce a first mixture of spent catalyst and product gas. The process may comprise the step of separating the first mixture of spent catalyst and product gas into a first cracking product stream and a first cooling catalyst stream in a first separation vessel. The process comprises the step of contacting a second hydrocarbon stream in a second riser with a stream of a second flow catalyst to produce a second mixture of spent catalyst and product gas. In the second separation vessel, the second mixture of spent catalyst and product gas is separated to provide a second cracking product stream and a second cooling catalyst stream. The first cracking product stream and the second cracking product stream are transferred upward through a gas recovery conduit and further separated from the catalyst in a series of cyclones to produce a hot product stream. The hot product stream is separated into a C2 gas stream, a C3 hydrocarbon stream, a C4 hydrocarbon stream, and a C5+ hydrocarbon stream. The process subsequently includes the step of oligomerizing the olefin in the C2 gas stream to produce a second hydrocarbon stream containing a C4+ oligomer. Brief explanation of the drawing

[0010] The drawing is a cross-sectional elevation view of the process and apparatus of the present invention. definition The term "downstream connection" means that at least a portion of the fluid flowing downstream to the subject of the connection can flow operablely from the object with which the subject is fluidly connected. The term "upstream connection" means that at least a portion of the fluid flowing from the subject of the upstream connection can flow operablely to the object with which the subject fluidly connects. The term "direct connection" refers to fluid flow from an upstream component entering a downstream component without passing through any other intervening vessel. The term "indirect connection" refers to fluid flow from an upstream component entering a downstream component after passing through an intervening vessel. The term "bypass" means that an object is separated from downstream communication with the bypassing entity, at least to the extent of bypassing. As used herein, “Naphtha” or “Full Range Naphtha” refers to a hydrocarbon mixture having a 10% point below 175°C (347°F) and a 95% point below 240°C (464°F) when measured by distillation according to the standard method of ASTM D86; “Light Naphtha” refers to a naphtha fraction having a boiling range within the range of C4 to 166°C (330°F); and “Heavy Naphtha” refers to a naphtha fraction having a boiling range within the range of 166°C (330°F) to 211°C (412°F). As used herein, the term “abundant” may mean an amount of at least 50 mole%, preferably 70 mole%, of a compound or class of compounds in a stream. As used herein, the term “paraffinic” with respect to a feed or stream refers to a light hydrocarbon mixture comprising at least 80 weight% paraffin, 10 weight% or less aromatic compounds, and 40 weight% or less cycloparaffin. As used herein, the term “mixed C4’s” with respect to a feed or stream refers to a light hydrocarbon mixture comprising at least 90 weight percent of a hydrocarbon compound having four carbon atoms. As used herein, the term “dominant” or “dominant” means more than 50%, suitably more than 75%, preferably more than 90%. The term “column” refers to a distillation column or columns for separating one or more components of different volatility. Unless otherwise specified, each column comprises a condenser located at the overhead of the column for condensing and recirculating a portion of the overhead stream back to the top of the column, and a reboiler located at the bottom of the column for vaporizing and recirculating a portion of the bottom stream back to the bottom of the column. Feed to the column may be preheated. Top pressure is the pressure of the overhead vapor at the vapor outlet of the column. Bottom temperature is the temperature at the liquid bottom outlet. The overhead line and bottom line refer to the net line from downstream of the column to the column for any reflux or reboiling. A stripper column may omit the reboiler at the bottom of the column and instead provide the heating requirements and separation drive from a fluidized inert medium, such as steam. A stripping column typically feeds to the top tray and takes the main product from the bottom. As used herein, the term "separator" refers to a vessel having an inlet and at least one overhead vapor outlet and a bottom liquid outlet, and may also have an aqueous stream outlet from a boot. A flash drum is a type of separator that can be downstream connected to a separator capable of operating at a higher pressure. Specific details for implementing the invention

[0011] The inventors have discovered that charging a catalytic cracking reactor with an iso-paraffin-rich stream results in greater conversion and yield of propylene. The inventors propose isomerizing the hydrocarbon feedstock to provide a reaction feed favorable to the FCC reactor in order to maximize the yield of propylene.

[0012] Now, returning to the drawing where similar numbers designate similar components, the process and apparatus generally include an isomerization unit (400), an FCC unit (6), and a product recovery section (90). The FCC unit section (6) includes a first FCC reactor (200) comprising a first FCC reactor unit (202).

[0013] The first hydrocarbon feedstock stream in line (402) is C4-C 10 It may contain hydrocarbons. Preferably, the first hydrocarbon feedstock stream contains light naphtha, such as C5-C7 hydrocarbons. The first hydrocarbon feedstock stream may contain at least 50 weight% paraffin, suitably at least 60 weight% paraffin, preferably at least 70 weight% paraffin. The first hydrocarbon feedstock stream may contain 25 weight% or less olefin, suitably 15 weight% or less olefin, preferably 1 weight% or less olefin. The first hydrocarbon feedstock stream may be dominated by normal paraffin.

[0014] In one embodiment, the first hydrocarbon feedstock stream in line (402) is a paraffin-rich naphtha stream, which is isomerized under isomerizing conditions in an isomerizing unit (400) in the presence of a hydrogen stream in line (404) to produce an isomerizing reactor effluent. The isomerizing reactor effluent is an iso-paraffin-rich hydrocarbon stream in line (410), which is then sent to the first reactor riser (212).

[0015] Hydrogen is mixed with or remains with the isomerization feed to the isomerization unit, providing a hydrogen-to-hydrocarbon feed molar ratio of 0.01 to 20. Hydrogen may be supplied entirely from outside the process or supplemented by hydrogen recirculated to the feed after separation from the isomerization reactor effluent. Light hydrocarbons and small amounts of inert substances (e.g., nitrogen and argon) may be present in the hydrogen. Water should preferably be removed from the hydrogen supplied from outside the process by an adsorption system as known in the art.

[0016] The isomerization of the paraffin-rich naphtha stream in line (402) can be achieved by any method known in the art or by using any suitable catalyst known in the art. One or more layers of catalyst may be used in the reactor(s). Isomerization is preferably performed in a co-current operating mode. Both a fixed bed, trickle bed down-flow mode and a fixed bed liquid filled up-flow mode are suitable. Additionally, refer to WO2023129920A1, which discloses that suitable catalysts may include, for example, alumina chloride, zirconia sulfate, zirconia tungstenide, or zeolite-containing isomerization catalysts. Superior isomerization catalysts may be amorphous, for example, based on amorphous alumina or zeolite. Zeolite catalysts will still typically contain an amorphous binder. The catalyst may comprise sulfated zirconia and platinum as described in U.S. Patent No. 5,036,035 and European Patent No. 0666109 A1, or platinum group metals on chlorinated alumina as described in U.S. Patent No. 5,705,730 and U.S. Patent No. 6,214,764. Other suitable catalysts are described in U.S. Patent No. 5,922,639. U.S. Patent No. 6,818,589 discloses a catalyst comprising a tungstenized support of an oxide or hydroxide metal of Group IVB (IUPAC 4), preferably zirconium oxide or zirconium hydroxide, at least one first component which is a lanthanide element and / or yttrium component, and at least one second component which is a platinum group metal component.

[0017] The isomerization conditions may include a temperature of 40 to 250°C (104 to 482°F) and a pressure of 100 kPa absolute pressure (14 psia) to 10,000 kPa absolute pressure (1450 psia). In another embodiment, the isomerization conditions include a temperature of 150 to 220°C (302 to 428°F) and a pressure of 3102 kPa absolute pressure (450 psia) to 3792 kPa absolute pressure (550 psia). The liquid hourly space velocity (LHSV) is a range of 0.2 to 25 volumes of hydrocarbon feed per hour per volume of catalyst. Other operating conditions for the isomerization zone are well known in the art. The isomerized product may be withdrawn continuously. In one embodiment, unreacted paraffin can be separated from isoparaffin in the reactor effluent by conventional means such as fractional distillation or adsorption, while unreacted normal paraffin can be recirculated to the isomerization reactor as part of the first hydrocarbon feedstock stream in line (402).

[0018] The drawing illustrates a first FCC reactor unit (202) comprising a first reactor riser (212) and a first reactor vessel (210). The first FCC reactor unit (202) comprises a first reactor riser (212), wherein a first hydrocarbon stream in a line (152) through one or more distributors near the base of the first reactor riser (212) comes into contact with a stream of a first flow catalyst.

[0019] The first hydrocarbon stream in line (152) may be provided as a mixture of the C5+ hydrocarbon stream in line (150) obtained from the product recovery section (90) and the iso-paraffin-rich hydrocarbon stream in line (410). Since the first hydrocarbon stream in line (152) is predominantly isoparaffin-based, it will decompose more easily and more selectively with respect to olefins. Process conditions in the first reactor riser (212) may include a decomposition reaction temperature of 400°C to 650°C, preferably 538°C to 650°C, at the reactor outlet. Decomposition occurs at an absolute pressure of 100 kPa (14 psia) to 650 kPa (94 psia), preferably 140 kPa (20 psia) to 450 kPa (65 psia). A first hydrocarbon stream with a steam flow rate of 5 to 25 weight percent is added to the first reactor riser (212). Control valves on the first high-temperature catalyst pipe (220) and the first recirculating catalyst pipe (222) can be used to adjust the catalyst density within the first reactor riser (212), thereby enabling control of the space velocity within it.

[0020] The catalyst may be a single catalyst or a mixture of different catalysts. Generally, the catalyst comprises two components or catalysts, namely, a first component or catalyst and a second component or catalyst. Such a mixture of catalysts is disclosed, for example, in U.S. Patent No. 7,312,370 B2. Generally, the first component may comprise any of the well-known catalysts used in the field of FCC, for example, an active amorphous clay-type catalyst and / or a highly active crystalline molecular sieve. Zeolites may be used as molecular sieves in the FCC process. Preferably, the first component comprises a large-pore zeolite such as a Y-type zeolite, an active alumina material, a binder material comprising silica or alumina, and an inert filler such as kaolin.

[0021] Typically, a zeolite molecular sieve suitable for the first component has a large average pore size. Generally, a molecular sieve having a large pore size has pores with an effective diameter greater than 0.7 nm, defined as a 12-membered ring, greater than 10. The pore size index of the large pores may be greater than 31. Suitable large pore zeolite components may include synthetic zeolites such as X and Y zeolites, mordenite, and sporesite. A portion of the first component, such as the zeolite, may have any suitable amount of a rare earth metal or a rare earth metal oxide.

[0022] The second component may comprise an intermediate or smaller pore zeolite catalyst, such as MFI zeolite, as exemplified by at least one of ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48, and other similar materials. Other suitable intermediate or smaller pore zeolites include ferririte and erionite. Preferably, the second component is an intermediate or smaller pore zeolite dispersed on a matrix comprising a binder material such as silica or alumina and an inert filler material such as kaolin. The second component may also comprise some other active material, such as beta zeolite. These compositions may have a crystalline zeolite content of 10 to 50 weight% or more and a matrix material content of 50 to 90 weight%. A component containing 40 weight% of crystalline zeolite material is preferred, and those having a larger crystalline zeolite content may be used. Generally, medium and small pore zeolites are characterized by having an effective pore opening diameter of 0.7 nm or less, rings of 10 or less, and a pore size index of less than 31.

[0023] The total catalyst mixture in the first FCC reactor (200) may contain 1 to 100 weight percent of a second component, i.e., a medium to small pore crystalline zeolite, and at least 30 weight percent of the second component is preferred. The first component may comprise the remainder of the catalyst composition. In some preferred embodiments, the relative ratio of the first and second components in the mixture may not change substantially throughout the first FCC reactor (200). High concentration medium or small pore zeolite as the second component of the catalyst mixture may improve selectivity for light olefins. In one exemplary embodiment, the second component may be a ZSM-5 zeolite catalyst, and the catalyst mixture may contain 4 to 50 weight percent of ZSM-5 zeolite, excluding any other components such as binders and / or fillers.

[0024] Preferably, at least one of the first and / or second catalysts is an MFI zeolite having a silicon-to-aluminum ratio of greater than 15, preferably greater than 75. In an exemplary embodiment, the silicon-to-aluminum ratio may be 15:1 to 35:1.

[0025] Contact may occur within a narrow first reactor riser (212) extending upward to the bottom of the first reactor vessel (210). A stream of the first flow catalyst may be fluidized with steam distributed from a distributor (218) at the bottom of the first reactor riser (212). The stream of the first flow catalyst may be provided as a mixture of a stream of the first high-temperature catalyst from the first high-temperature catalyst pipe (220) and a stream of the first recirculating catalyst from the first recirculating catalyst pipe (222). Heat from the catalyst vaporizes the first hydrocarbon feedstock, and the first hydrocarbon feedstock is then decomposed into a first decomposition product stream of lighter molecular weight in the presence of the first catalyst stream, both of which are transferred over the first reactor riser (212) into the first reactor vessel (210) and provide a first mixture of spent catalyst and product gas.

[0026] The first reactor riser (212) is terminated in the upper end of the first separation chamber (211) located within the first reactor vessel (210) in a curved duct (214) or a plurality thereof. The curved duct (214) can centrifugally discharge a first mixture of spent catalyst and product gas into the first separation chamber (211). By centrifugal discharge, the first mixture is discharged from inward to outward. The centrifugal discharge of the gas and catalyst creates a swirling spiral pattern inside the first separation chamber (211) to separate the first mixture of spent catalyst and product gas within the first separation chamber (211) into a first decomposition product stream and a first cooling catalyst stream.

[0027] The stream of the first cooling catalyst is collected within a dense catalyst layer (228). The first stream of product gas passes upward through a gas recovery conduit (226), is further separated from the catalyst in a cyclone (232), and is discharged from the first reactor vessel (210) through a product outlet (230) in a product line (231) as a gaseous FCC high-temperature product stream.

[0028] The drawing illustrates a second FCC reactor unit (302), wherein a second hydrocarbon stream in a line (315) distributed through one or more distributors near the base of the second reactor riser (312) comes into contact with a stream of the second flow catalyst in the second riser. In one embodiment, the second FCC reactor unit (302) is integrated with the first FCC reactor unit (202). However, the second FCC reactor unit (302) may be independent of the first FCC reactor (202) within its own FCC reactor.

[0029] The second hydrocarbon feedstock may be olefin-dominant. The second hydrocarbon stream is more olefinic than the first hydrocarbon stream. The second hydrocarbon stream may contain at least 20 weight% olefin, suitably at least 40 weight% olefin, preferably at least 60 weight% olefin. The second hydrocarbon stream may contain at least 1 weight% paraffin, suitably at least 15 weight% paraffin, preferably at least 25 weight% paraffin. The second hydrocarbon stream comprises C4 hydrocarbon and C4+ oligomer streams recovered from the product recovery section (90). The second hydrocarbon stream may further contain C5 to C7 hydrocarbons that have been decomposed from the product gas of the first riser.

[0030] The stream of the second flow catalyst may have the same catalyst composition as the stream of the first catalyst. In another preferred embodiment, the stream of the second flow catalyst may predominantly contain the second component, and in further embodiments, may contain only the second component, preferably ZSM-5 zeolite, as a catalyst.

[0031] The stream of the second flow catalyst can be fluidized with steam distributed from the distributor (358) at the bottom of the second reactor riser (312). The stream of the second flow catalyst can be provided as a mixture of the stream of the second high-temperature catalyst from the second high-temperature catalyst pipe (362) and the stream of the second recirculating catalyst from the second recirculating catalyst pipe (264). The second hydrocarbon feedstock is vaporized and converted or decomposed into a second cracking product stream containing ethylene and propylene at a higher concentration within the second hydrocarbon stream. Molar expansion and vaporization cause the second hydrocarbon stream and the second cracking product stream to rapidly rise up the second reactor riser (312), accompanied by the stream of the second flow catalyst as a second mixture of spent catalyst and product gas.

[0032] Process conditions in the second reactor riser (312) may be less stringent than in the first reactor riser (212). The second reactor riser (312) may operate under one or more of the following conditions compared to the first reactor riser (212): a lower outlet temperature, a lower residence time, and a lower catalyst density than the first riser. The hydrocarbon partial pressure may also be varied to adjust the stringency of the second reactor riser. The hydrocarbon partial pressure may be varied by adjusting the total pressure in the second reactor riser (312) independently of the pressure in the first FCC reactor (202) and possibly by adjusting the amount of steam for the third reactor riser (312).

[0033] Conditions within the second reactor riser (312) may include a decomposition reaction temperature of 400°C to 600°C, preferably 565°C to 600°C, at the reactor outlet. Decomposition occurs at an absolute pressure of 100 kPa (14 psia) to 506 kPa (74 psia), preferably 138 kPa (20 psia) to 310 kPa (45 psia). A vapor of 5 to 25 weight percent of the second hydrocarbon stream is added to the second reactor riser (312). Control valves on the second high-temperature catalyst pipe (362) and the second recirculating catalyst pipe (264) may be used to adjust the catalyst density within the second reactor riser (312), thereby enabling control of the space velocity therein.

[0034] The second reactor riser (312) of the second FCC reactor unit (302) may be located outside the first FCC reactor (202), but may share the first reactor vessel (210) with the first reactor riser (212) and the first FCC reactor (202). The second reactor riser (312) includes an exhaust opening (349) within the second separation chamber (360). The second separation chamber (360) includes the exhaust opening (349) of the second reactor riser (312). The second separation chamber (360) may be located within the first reactor vessel (210). In one embodiment, the horizontal transfer line (348) of the second reactor riser (312) is terminated within the second separation chamber (360). The discharge opening (349) of the second reactor riser (312) discharges the second mixture of spent catalyst and product gas tangentially into the second separation chamber (360). In another embodiment, the horizontal transfer line (348) may be replaced with an alternative connector, such as a T-type connector or an elbow having a more acute or more obtuse angle. The tangential discharge of the second mixture of spent catalyst and product gas from the second reactor riser (312) through the discharge opening (349) creates a swirling spiral pattern inside the second separation chamber (360). The separation of the second mixture of spent catalyst and product gas into a stream of the second cooling catalyst and a stream of the second decomposition product may be guided outwardly and concentrically to the separation of the first mixture of spent catalyst and product gas into a stream of the first decomposition product and a stream of the first cooling catalyst. To maximize selectivity for propylene, it is important that the first mixture of catalyst and product gas is not mixed with the second mixture of catalyst and product gas until the bulk of the catalyst is removed from the product gas.

[0035] In one embodiment, the stream of the second cooling catalyst is collected within a dense catalyst layer (228) together with the stream of the first cooling catalyst. In a further embodiment, the second decomposition product stream is delivered upward through a gas recovery conduit (226) together with the first decomposition product stream, further separated from the catalyst in a cyclone (232), and discharged from the first reactor vessel (210) through a product outlet (230) in a product line (231) as a gaseous FCC high-temperature product stream.

[0036] A mixed stream of cooling catalyst separated from the dense catalyst layer (228) is delivered downward through the stripping section (284). The stripping fluid, typically vapor, enters the lower part of the stripping section (284) through the distributor (234). Countercurrent contact between the catalyst and the stripping fluid through a series of stripping baffles, packings, or gratings displaces the product gas from the catalyst as the product gas continues downward through the stripping section (284).

[0037] A stream of the first stripped catalyst from the stripping section (284) passes through the heater conduit (236) and proceeds to the catalyst heater (238). The catalyst heater (238) provides a stream of the first high-temperature catalyst in the first high-temperature catalyst pipe (220) supplied to the first reactor riser (212) and a stream of the second high-temperature catalyst in the second high-temperature catalyst pipe (362) supplied to the second reactor riser (312).

[0038] A stream of the second stripped catalyst from the dense catalyst layer (228) is delivered into the recirculation conduit (240) to provide the stream of the first recirculated catalyst in the first recirculated catalyst pipe (222) to the first reactor riser (212) and the stream of the second recirculated catalyst in the second recirculated catalyst pipe (264) to the second reactor riser (312). The catalyst in the first FCC reactor unit (202) and the second FCC reactor unit (302) is not coked to such an extent. Therefore, insufficient coke may be burned to balance the heat demand in the reactor. To replenish heat in the first FCC reactor (202) and the second FCC reactor unit (302), a gaseous or liquid fuel (not shown in the drawing) is burned to heat the catalyst. The catalyst from the first FCC reactor (202) and the second FCC reactor unit (302) can be transferred to the catalyst heater (238) by the heater conduit (236).

[0039] A portion of the stream of the first flow catalyst is heated in a catalyst heater (238) before contacting the stream of the first flow catalyst with the first hydrocarbon stream. A portion of the stream of the second flow catalyst is heated in a catalyst heater (238) before contacting the stream of the second flow catalyst with the second hydrocarbon feedstock stream. The flue gas stream in line (242) generated out of the catalyst heater (238) can be appropriately sent to a flue gas treatment unit. In another embodiment, fuel combustion in the catalyst heater (238) can be replaced by an electric coil powered by renewable or fossil fuel-based electricity.

[0040] To generate more coke on the catalyst, a C4+ hydrocarbon stream may be supplied to the catalyst in the catalyst heater (238) directly from the first coking line (221) or from one or more of the stream of the first high-temperature catalyst in the first high-temperature catalyst pipe (220) to the second coking line (223), the stream of the second high-temperature catalyst in the second high-temperature catalyst pipe (362) to the third coking line (225), the recirculating catalyst in the first recirculating catalyst pipe (222) to the fourth coking line (227), and the recirculating catalyst in the second recirculating catalyst pipe (264) to the catalyst heater (238). The C4+ injection in the catalyst pipe will help optimize the level of coke in the catalyst to maximize propylene selectivity in the first and second risers. The C4+ hydrocarbon injection should be located downstream of the control valve in the catalyst pipe. The coke distribution in the catalyst must be 0.1 to 5 weight percent coke on the catalyst, preferentially 0.1 to 2 weight percent coke on the catalyst in the first reactor riser (212), and 0.1 to 1 weight percent coke on the catalyst in the second reactor riser (312).

[0041] The product recovery section (90) is in downstream communication with the product outlet (230). “Communication” means that material flow between the listed components is operablely allowed. Within the product recovery section (90), the gaseous FCC high-temperature product stream in the product line (231) is directed to the lower section of the FCC main fractionation column (92). The main column (92) is in downstream communication with the product outlet (230). Various fractions of the FCC product may be separated and taken from the main column, including heavy slurry oil from the bottom in line (93), a heavy cycle oil stream in line (94), light cycle oil in line (95) taken from outlet (95a), and a heavy naphtha stream in line (96) taken from outlet (96a). Any one or all of the lines (93 to 96) may be cooled and pumped back into the main column (92) to cool the main column, typically at a higher position. Gasoline and gaseous light hydrocarbons are removed from the main column (92) within the overhead line (97) and condensed before entering the main column receiver (99). The main column receiver (99) is in downstream communication with the product outlet (230), and the main column (92) is in upstream communication with the main column receiver (99). "Upstream communication" means that at least a portion of the material flowing from the component of the upstream communication can flow operablely to the component of the communication.

[0042] The aqueous stream is removed from the boot in the receiver (99). Additionally, the condensed light naphtha stream is removed in line (101), while the overhead stream is removed in line (102). The overhead stream in line (102) contains gaseous light hydrocarbons, which may include a diluted ethylene stream. The streams in lines (101 and 102) may enter the vapor recovery section (120) of the product recovery section (90).

[0043] Although the vapor recovery section (120) is depicted as an absorption-based system, any vapor recovery system including a cold box system may be used. To obtain sufficient separation of the light gas components, the gaseous stream in line (102) is compressed in the compressor (104). More than one compressor stage may be used, but typically dual-stage compression is utilized. The compressed light hydrocarbon stream in line (106) is joined by the streams in lines (107 and 108), cooled, and delivered to the high-pressure receiver (110). The aqueous stream in line (111) from the receiver (110) may be sent to the main column receiver (99). The gaseous hydrocarbon stream in line (112) containing the diluted ethylene stream is sent to the primary absorber (114), where it comes into contact with the destabilized gasoline from the main column receiver (99) in line (101) to form C3 + Hydrocarbons and C2 - Separation between hydrocarbons is achieved. The primary absorber (114) is connected downstream to the main column receiver (99). Liquid C3 in line (107) + The stream is returned to line (106) before cooling. The primary off-gas stream in line (116) from the primary absorber (114) contains a diluted ethylene stream for the purposes of the present invention. However, to further concentrate the ethylene stream and recover heavier components, line (116) may optionally be directed to a secondary absorber (118), where the circulating stream of light cycle oil in line (121) diverted from line (95) contains the remaining C5 in the primary off-gas stream. + and absorbs most of some C3-C4 substances. The secondary absorber (118) is downstream connected to the primary absorber (114). C3 +Light cycle oil from the bottom of the secondary absorber in the material-rich line (119) is returned to the main column (92) via a pump around line (95). C2 having hydrogen sulfide, ammonia, carbon dioxide, and hydrogen predominantly - The overhead of the secondary absorber (118) containing the dry gas of the hydrocarbon is removed in the secondary off-gas stream in line (122) to contain a diluted ethylene stream.

[0044] The liquid from the high-pressure receiver (110) in line (124) is sent to the stripper (126). Most of the C2 -It is removed within the overhead of the stripper (126) and returned to line (106) through the overhead line (108). The liquid bottom stream from the stripper (126) is sent to the first debutane column (130) within the bottom line (128). The first debutane column (130) provides an overhead stream within line (132) containing a C3-C4 hydrocarbon stream from the first debutane column. The bottom stream within line (134) may contain a debutaneized naphtha stream. The debutaneized naphtha stream containing C5+ paraffin is recirculated within line (134) and becomes part of the first fill material within line (152). A C3-C4 hydrocarbon stream taken from line (132) can be separated into a C3 hydrocarbon stream in the overhead line (146) and a C4 hydrocarbon stream in the bottom column (148) within a C3-C4 splitter column (144). A C4 hydrocarbon stream containing olefinic C4 hydrocarbons taken from the bottom column (148) of the C3-C4 splitter column, which is also downstream connected to the main column (92) in line (97), can be recirculated to a second FCC reactor unit (302) in the second hydrocarbon stream (315) as at least a part of the second hydrocarbon stream. The C3 hydrocarbon stream in the overhead line (146) can be further processed for propylene recovery. The second hydrocarbon stream (315) is preheated to a temperature of 221°C (400°F) to 621°C (1150°F) and charged into the second FCC reactor unit (302).

[0045] The diluted ethylene stream may be a secondary off-gas stream within line (122) and may comprise an FCC dry gas stream containing 5 to 65 weight percent ethylene, preferably 10 to 55 weight percent ethylene. Methane will typically be the dominant component in the diluted ethylene stream at a concentration of 25 to 55 weight percent, and ethane is typically substantially present at 5 to 45 weight percent. Hydrogen and nitrogen may each be present in the diluted ethylene stream at 0.5 to 25 weight percent, typically 1 to 20 weight percent. Saturated levels of water may also be present in the diluted ethylene stream. If a secondary absorber (118) is used, C3 of 5 weight percent or less + It will typically be present with less than 0.5 weight percent of propylene.

[0046] In addition to hydrogen, other impurities such as hydrogen sulfide, ammonia, carbon dioxide, and acetylene may also be present in the diluted ethylene stream. These impurities in the dry gas ethylene stream can impart toxicity to the oligomerization catalyst. Hydrogen and carbon monoxide can reduce and deactivate metal sites. Carbon dioxide and ammonia can attack acidic sites on the catalyst. Hydrogen sulfide can attack metals on the catalyst to form metal sulfides. Acetylene can polymerize and adhere to the catalyst or equipment.

[0047] A secondary off-gas stream in line (122) containing a diluted ethylene stream can be introduced into a selective amine absorber unit (160) to remove hydrogen sulfide at a lower concentration. A dilute aqueous amine solution, such as one containing monoethanolamine or diethanolamine, is introduced into the absorber (160) through line (162) and comes into contact with the flowing secondary off-gas stream to absorb hydrogen sulfide, and the hydrogen sulfide-rich aqueous amine absorbing solution is removed from the absorbing zone (160) through line (163), recovered, and possibly further processed.

[0048] The amine-treated diluted ethylene stream in line (164) is introduced into an optional water wash unit (166) to remove residual amines carried from the amine absorber (160) and to reduce the concentration of ammonia and carbon dioxide in the diluted ethylene stream in line (164). Water is introduced into the water wash unit in line (165). The water in line (165) is typically slightly acidified to enhance the capture of basic molecules such as amines. The aqueous stream in line (167), rich in amines and potentially ammonia and carbon dioxide, leaves the water wash unit (166) and can be further treated.

[0049] In one embodiment, optionally amine-treated diluted ethylene and possibly water-washed streams in line (168) may then be treated in an optional guard layer (170) to remove one or more impurities, such as carbon monoxide, hydrogen sulfide, and ammonia, to a lower concentration. The guard layer (170) may contain an adsorbent to adsorb impurities, such as hydrogen sulfide, which can impart toxicity to the oligomerization catalyst. The guard layer (170) may contain multiple adsorbents to adsorb more than one type of impurity. A conventional adsorbent for adsorbing hydrogen sulfide is ADS-12, an adsorbent for adsorbing CO is ADS-106, and an adsorbent for adsorbing ammonia is UOP MOLSIV 3A, all of which are available from UOP, LLC. The adsorbents may be mixed within a single layer or arranged within a continuous layer.

[0050] In another embodiment, optionally amine-treated diluted ethylene and possibly a water-washed stream in line (168) may be treated to recover or reduce the hydrogen concentration in the diluted ethylene stream in line (168) to a lower level. In an exemplary embodiment, unit (170) is a pressure swing adsorption (PSA) unit instead of a guard layer. Optionally amine-treated diluted ethylene and possibly a water-washed stream in line (168) may be transferred to a pressure swing adsorption (PSA) unit (170) to recover or reduce the hydrogen concentration in the diluted ethylene stream in line (168) to a lower level. Optionally amine-treated diluted ethylene and possibly a water-washed stream in line (168) may enter the PSA (170) at high pressure. Molecules heavier than hydrogen present in the optionally amine-treated diluted ethylene and possibly a water-washed stream in line (168) are adsorbed onto the adsorbent, whereas hydrogen molecules are not adsorbed onto the adsorbent and pass through the layer. The adsorbent may be selected from one or more of molecular sieves, including but not limited to silica gel, alumina, activated carbon, zeolite, metal-organic framework (MOF), or mixtures thereof. The PSA (170) may comprise a single layer or multiple layers of adsorbents of different compositions. Light molecules, such as hydrogen, leave the PSA (170) at high pressure in line (173) and are recovered. Adsorbed heavy molecules are then desorbed from the PSA (170) at lower pressure and recovered in a PSA tail gas stream containing ethylene in line (171).

[0051] In one embodiment, the PSA unit (170) can be operated at an adsorption pressure of 1500 kPa (220 psi) to 3500 kPa (515 psi) and a desorption pressure of 100 kPa (15 psi) to 300 kPa (44 psi).

[0052] In another embodiment, optionally amine-treated diluted ethylene and possibly a water-washed stream in line (168) may pass through a membrane unit (170) to recover or reduce the hydrogen concentration in the diluted ethylene stream in line (168) to a lower level. In the membrane unit (170), the optionally amine-treated diluted ethylene and possibly a water-washed stream in line (168) pass through the membrane at high pressure. In an exemplary embodiment, the membrane unit (170) may comprise a polyimide or polyethersulfone-polyimide blend membrane. Other suitable membranes may comprise a polymer, porous ceramic, dense ceramic, or metal membrane. After contact, molecules heavier than hydrogen present in the optionally amine-treated diluted ethylene and possibly a water-washed stream in line (168) are mostly rejected by the membrane as residues. Heavy molecules containing ethylene leave the membrane unit (170) at high pressure and are drawn from the membrane unit (170) into a residue stream containing ethylene in line (171). Optionally, hydrogen present in the amine-treated diluted ethylene and possibly in the water-washed stream in line (168) permeates through the membrane with higher selectivity than the retained molecules, and the hydrogen is recovered at a lower pressure in the hydrogen stream in line (173) on the other side of the membrane.

[0053] The membrane unit (170) can be operated at temperatures ranging from 40°C (104°F) to 80°C (176°F). The differential pressure across the membrane can be as low as 70 kPa (10 psi) or as high as 14.5 MPa (2100 psi), depending on many factors such as the specific membrane used, the flow rate of the inlet stream, and the availability of a compressor to compress the permeate stream where such compression is required. In one embodiment, the differential pressure across the membrane can be in the range of a supply pressure of 446 kPa (50 psig) to 6996 kPa (1000 psig).

[0054] To remove more hydrogen sulfide, ammonia, and carbon monoxide, the diluted ethylene stream in line (171), which is possibly amine-treated, possibly washed with water, and possibly adsorbed, will typically have at least one of the following impurity concentrations: 0.1 wt% to 5.0 wt% carbon monoxide and / or 0.1 wt% to 5.0 wt% carbon dioxide, and / or 1 wppm to 500 wppm hydrogen sulfide and / or 1 wppm to 500 wppm ammonia, and / or 0.1 wt% to 10 wt% hydrogen. The type and concentration of the impurities present will vary depending on the treatment and origin of the diluted ethylene stream.

[0055] Line (171) carries the diluted ethylene stream to the compressor (172) to pressurize it to reactor pressure. The compressor (172) is in downstream communication with the main column (92), the product recovery section (90), and the product outlet (230). The compressed diluted ethylene stream can be compressed to 3,550 kPa (500 psia) or more and possibly 10,445 kPa (1500 psia) or less, suitably 4,930 kPa (700 psia) to 7,687 kPa (1100 psia). To prevent rapid catalyst deactivation, it is preferable that the diluted ethylene stream be pressurized to a critical pressure of ethylene, which is 4,992 kPa (724 psia) for pure ethylene. The compressor (172) may include one or more stages with cooling between stages. A heater may be required to raise the compressed stream to the reaction temperature. The compressed diluted ethylene is transported in line (174) to an oligomerization reactor (176).

[0056] The oligomerization reactor (176) is in downstream communication with the compressor (172) and the primary and secondary absorbers (114 and 118), respectively. The oligomerization reactor preferably comprises a fixed catalyst layer (178). The diluted ethylene feed stream preferably comes into contact with the catalyst in downward flow operation. However, upward flow operation may be suitable. The catalyst is preferably an amorphous silica-alumina base having metals of Group 6, 8, 9, and 10 in the periodic table using IUPAC notation. In one embodiment, the catalyst has a Group 8, 9, or 10 metal promoted by a Group 6 metal (hereinafter 8 to 10). In one embodiment, the catalyst may have a silica-to-alumina ratio of less than 30, preferably less than 20. Typically, since silica and alumina exist only within the base, the silica-to-alumina ratio will be the same for the catalyst as for the base. The metal can be impregnated with or ion-exchanged with a silica-alumina base. Co-mulling is also considered. Additionally, suitable catalysts are 50 to 400 m as measured by nitrogen BET. 2 It will have a surface area of ​​ / g.

[0057] A preferred oligomerization catalyst of the present invention has an amorphous silica-alumina base impregnated with 0.5 to 15 weight percent nickel in the form of a 3.175 mm (0.125 inch) extruder with a density of 0.45 to 0.65 g / mL. It is also considered that the metal may be incorporated on the support by other methods such as ion exchange and co-grinding.

[0058] The diluted ethylene feed in line (174) can be contacted with an oligomerization catalyst in a catalyst layer (178) at a temperature of 100°C to 400°C. The reaction is carried out at a GHSV of 50 to 1000 hr based on ethylene. -1It occurs predominantly in the gaseous state. The conversion of ethylene in the feed stream into heavier hydrocarbons varies from 40% by weight to 75% by weight. Ethylene will first be oligomerized into heavier olefins via a catalyst. Some of the heavier olefins can be cyclized via a catalyst, and the presence of hydrogen can facilitate the conversion of the olefins into paraffins, which are hydrocarbons heavier than ethylene. However, the decomposition of the cyclized and saturated product into propylene is undesirable and must be minimized through the appropriate selection of catalysts and reaction conditions.

[0059] The catalyst can be maintained stably despite impure feed, but can be regenerated upon deactivation. Suitable regeneration conditions may include, for example, exposing the catalyst in-situ to high-temperature air at 500°C for 3 hours. The activity and selectivity of the regenerated catalyst may be comparable to those of a new catalyst.

[0060] The oligomerization product stream from the oligomerization reactor in line (180) can be transferred to an oligomerization separation unit (182). The oligomerization separation unit may be a simple flash drum for separating a gaseous stream from a liquid stream. The oligomerization separation unit (182) is in downstream communication with the oligomerization reactor (176). A light raffinate stream in the overhead line (184), containing light gases such as hydrogen, methane, ethane, unreacted olefins, and light impurities, can be transferred to a combustion unit (186) to generate steam in line (187). Alternatively, the light raffinate stream in the overhead line (184) may provide a source of flue gas to be burned in a heater (not shown) and / or to rotate a gas turbine (not shown) to generate power. The overhead line (184) is in upstream communication with the combustion unit (186). C 4+The liquid bottom stream in line (185) containing olefins, preferably C4 and C6 olefins, can be further used to produce additional propylene.

[0061] C 4+ The oligomerized liquid bottom stream taken in line (185), comprising olefins and other C2 oligomers, may be combined with the C4 hydrocarbon stream in line (148) for recirculation to the second FCC reactor unit (302) in the second hydrocarbon stream (315) as at least a portion of the second hydrocarbon stream. The second hydrocarbon stream will be richly olefinic and will be broken down into propylene molecules for recovery in line (146).

[0062] Examples

[0063] Example 1

[0064] A decomposition catalyst was prepared by extruding an MFI zeolite (SiO2 / Al2O3 molar ratio 400 to 500) with a silica binder and steam-treating the extruder until the activity was attenuated, using a feed consisting of 40 wt% mixed butene and 60 wt% mixed butane at a weight-hour space velocity (WHSV) of 13.5 and a temperature of 568°C to produce the following product:

[0065] [Table 1]

[0066]

[0067] Example 2

[0068] The attenuated catalyst from Example 1 is used to decompose two different C5 hydrocarbon feedstocks, one rich in normal pentane and the other rich in iso-pentane, under the same conditions listed in Table 2 below. The applicant observed that the decomposition product of the iso-rich feedstock contained higher light olefins.

[0069] [Table 2]

[0070]

[0071] Example 3

[0072] The attenuated catalyst from Example 1 is used for the decomposition of a mixed C4 feed (37.7 wt% iso-butane, 10.3 wt% n-butane, the remainder being mixed linear C4 olefins) under the conditions listed in Table 3 below. The applicant observed that while the conversion of n-butane is negligible, a significant conversion of iso-butane can be observed.

[0073] [Table 3]

[0074]

Claims

Claim 1 A process for the catalytic production of olefins, comprising the steps of: delivering a feed stream to an isomerization unit to provide a first hydrocarbon stream rich in iso-paraffin; contacting the first hydrocarbon stream with a stream of a first flow catalyst in a first reactor riser to produce a first mixture of spent catalyst and product gas; separating the first mixture of spent catalyst and product gas into a first cracking product stream and a stream of a first cooling catalyst; separating a diluted ethylene stream from the first cracking product stream; oligomerizing the diluted ethylene stream to produce a second hydrocarbon stream containing a C4+ oligomer; and contacting the second hydrocarbon stream with a stream of a second flow catalyst in a second reactor riser to produce a second mixture of spent catalyst and product gas. Claim 2 A process according to claim 1, wherein the first mixture of the spent catalyst and the product gas is separated in a first separation vessel, and the process further comprises the step of separating the second mixture of the spent catalyst and the product gas in a second separation vessel to provide a second decomposition product stream and a second cooling catalyst stream. Claim 3 A process according to paragraph 2, further comprising the steps of: transferring the first decomposition product stream upward together with the second decomposition product stream through a gas recovery conduit; and further separating from the catalyst in a series of cyclones to produce a gaseous FCC high-temperature product stream. Claim 4 A process according to claim 3, further comprising the step of separating the gaseous FCC high-temperature product stream into the diluted ethylene stream, C3 hydrocarbon stream, C4 hydrocarbon stream, and C5+ hydrocarbon stream. Claim 5 A process according to claim 4, further comprising the step of contacting the C4 hydrocarbon stream and the second hydrocarbon stream with the stream of the second flow catalyst within the second reactor riser to produce a second mixture of the spent catalyst and product gas. Claim 6 A process according to claim 4, further comprising the step of contacting the C5+ hydrocarbon stream and the first hydrocarbon stream with the stream of the first flow catalyst within the first reactor riser to produce a first mixture of the spent catalyst and product gas. Claim 7 A process according to claim 1, wherein the first hydrocarbon stream is rich in isoparaffins and the second hydrocarbon stream is more olefinic than the first hydrocarbon stream. Claim 8 A process for the catalytic production of olefins, comprising the steps of: contacting a first hydrocarbon stream with a first flow catalyst stream in a first reactor riser to produce a first mixture of spent catalyst and product gas; separating the first mixture of spent catalyst and product gas to provide a first cracking product stream and a first cooling catalyst stream; separating a gaseous FCC high-temperature product stream into a diluted ethylene stream, a C3 hydrocarbon stream, a C4 hydrocarbon stream, and a C5+ hydrocarbon stream; oligomerizing the diluted ethylene stream to produce a second hydrocarbon stream containing a C4+ oligomer; and contacting the second hydrocarbon stream with a second flow catalyst stream in a second reactor riser to produce a second mixture of spent catalyst and product gas. Claim 9 A process according to claim 8, further comprising the step of separating a first mixture of the spent catalyst and product gas in a first separation vessel to provide a first decomposition product stream and a first cooling catalyst stream, and separating a second mixture of the spent catalyst and product gas in a second separation vessel to provide a second decomposition product stream and a second cooling catalyst stream. Claim 10 A process according to claim 9, further comprising the steps of: transferring the first decomposition product stream upward together with the second decomposition product stream through a gas recovery conduit; and further separating from the catalyst in a series of cyclones to produce a high-temperature product stream.

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