Process for converting olefins to distillate fuels by regeneration

Abstract

A process for oligomerizing olefins and a process for oligomerizing olefins to distillate fuels, which process regenerates the first stage oligomerization catalyst bed and / or the second stage oligomerization catalyst bed in situ by contacting the catalyst with oxygen gas at elevated temperatures. The oligomerization catalyst can be restored to full activity. The regeneration process can allow for continuous operation.

Description

[Technical Field]

[0001] (Priority statement) This application claims priority to Indian Provisional Patent Application No. 202211049525, filed on August 30, 2022, which is incorporated herein in its entirety.

[0002] The field is the conversion of olefins to distillates. The field may particularly relate to the oligomerization of olefins and the oligomerization of oligomerized olefins to distillate fuels. [Background technology]

[0003] Ethylene can be dimerized to olefins, such as C4, C6, and C8 olefins. Olefin oligomerization is a process by which smaller olefins can be oligomerized to larger olefins. More specifically, olefins, including dimerized olefins, can be converted to distillates, including jet fuel and diesel range products. The oligomerized distillates can be saturated for use as transportation fuels.

[0004] The dimerization reaction of ethylene is highly exothermic. The exotherm generated by the dimerization of ethylene can be difficult to manage.

[0005] Jet fuel is one of the few petroleum fuels that cannot be easily replaced by electric motor systems because fueling an airplane requires a high energy output that cannot be provided by an electric motor. In certain regions, significant tax incentives are currently available for green jet fuel.

[0006] An efficient process for converting ethylene to distillate fuels is desired. Summary of the Invention

[0007] The present inventors have devised a process for oligomerizing olefins into distillate fuels in which the oligomerization catalyst bed is regenerated in situ by contact with oxygen gas at elevated temperatures, allowing for continuous oligomerization over extended periods of time without loss of performance. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of the oligomerization section of the process and apparatus of the present disclosure. [Figure 2] FIG. 1 is a schematic diagram of the hydrogenation section of the process and apparatus of the present disclosure. [Figure 3] FIG. 1 is a schematic diagram of a regeneration process for the oligomerization section of the process and apparatus of the present disclosure. [Figure 4] FIG. 1 is a further regeneration process schematic of the oligomerization section of the process and apparatus of the present disclosure. [Figure 5] 1 is a table of the continuous operation and regeneration schedule of the present disclosure. [Figure 6] 1 is a plot of conversion versus time before and after regeneration. [Figure 7] 1 is a plot of selectivity versus time before and after regeneration.

[0009] definition The term "communication" means that fluid flow is operably permitted between the listed components, which may be characterized as "fluid communication."

[0010] The term "downstream communication" means that at least a portion of the fluid flowing to an object in downstream communication can operatively flow from the object in fluid communication.

[0011] The term "upstream communication" means that at least a portion of the fluid flowing from the object with which it is in upstream communication can operatively flow to the object with which it is in fluid communication.

[0012] The term "direct communication" means that fluid flow from an upstream component enters a downstream component without passing through any other intervening vessel.

[0013] The term "indirect communication" means that fluid flow from an upstream component enters a downstream component after passing through an intervening vessel.

[0014] The term "bypass" means that an object is out of downstream communication with a bypass subject, at least to the extent that it bypasses.

[0015] As used herein, the term "predominant" or "predominantly" means more than 50%, suitably more than 75%, and preferably more than 90%.

[0016] The term "column" refers to a distillation column or columns for separating one or more components of different volatility. Unless otherwise indicated, each column includes a condenser at the top of the column for condensing and refluxing a portion of the overhead stream that returns to the top of the column, and a reboiler at the bottom of the column for vaporizing a portion of the bottom stream and returning it to the bottom of the column. The feed to the column may be preheated. The top pressure is the pressure of the overhead vapor at the vapor outlet of the column. The bottom temperature is the liquid bottom outlet temperature. The overhead and bottom lines refer to the net lines from column to column downstream of any reflux or reboil. A stripper column may omit the reboiler at the bottom of the column and instead provide the required heat and driving force for separation from a fluidized inert medium such as steam. A stripping column typically feeds the feed to the top tray and removes the main product from the bottom.

[0017] As used herein, the term "separator" means a vessel having an inlet and at least an overhead vapor outlet and a bottoms liquid outlet, and may also have an aqueous outlet from a boot. A flash drum is a type of separator that may be in downstream communication with a separator that may be operated at a higher pressure. As used herein, the term "boiling point temperature" means the atmospheric equivalent boiling point (AEBP) calculated from the observed boiling point and distillation pressure, calculated using the formula provided in ASTM D1160 Appendix A7, entitled "Practice for Converting Observed Vapor Temperatures to Atmospheric Equivalent Temperatures."

[0018] As used herein, the term "True Boiling Point" (TBP) refers to a test method for determining the boiling point of a substance, which test method corresponds to ASTM D-2892 for producing liquefied gases, distillate fractions, and bottoms of standardized quality for which analytical data can be obtained, and for determining the yield of said fractions by both mass and volume, where a graph of temperature versus mass % distilled is produced using 15 theoretical plates in a column with a reflux ratio of 5:1.

[0019] As used herein, the terms "T5," "T90," or "T95" refer to the temperature at which 5 percent, 90 percent, or sometimes 95 percent by weight of a sample boils using ASTM D-86 or TBP, respectively.

[0020] As used herein, the term "initial boiling point" (IBP) means the temperature at which a sample begins to boil using ASTM D-7169, ASTM D-86, or TBP, as the case may be.

[0021] As used herein, the term "end point" (EP) means the temperature at which the sample has completely evaporated using ASTM D-7169, ASTM D-86, or TBP, as the case may be.

[0022] As used herein, the term "diesel" refers to hydrocarbons boiling within a range of "diesel cut points" including an IBP of 125°C (257°F) to 175°C (347°F) or a T5 of 150°C (302°F) to 200°C (392°F), and a T95 of 343°C (650°F) to 399°C (750°F) using the TBP distillation method or a T90 of 280°C (536°F) to 340°C (644°F) using ASTM D-86. The term "green diesel" refers to diesel containing hydrocarbons not derived from fossil fuels.

[0023] As used herein, the term "jet fuel" means a hydrocarbon that boils in the range of a T10 of 190°C (374°F) to 215°C (419°F) and an endpoint of 290°C (554°F) to 310°C (590°F). The term "green jet fuel" means a jet fuel that contains hydrocarbons that do not originate from fossil fuels. DETAILED DESCRIPTION OF THE INVENTION

[0024] The disclosed process involves dimerizing and oligomerizing an olefin stream containing ethylene, followed by further oligomerizing the ethylene oligomers, and utilizes a zeolite catalyst for ethylene oligomerization in a first stage and a metal catalyst for olefin oligomerization in a second stage.

[0025] The process and apparatus may include oligomerization section 10 of FIG. 1 and hydrogenation section 110 of FIG.

[0026] Referring to oligomerization section 10 of FIG. 1 , an input olefin stream in line 12 is fed to oligomerization section 10. The input olefin stream can comprise substantial ethylene. The input olefin stream can comprise primarily ethylene. In embodiments, the input olefin stream can comprise at least 95 mole % ethylene. The input olefin stream in line 12 may also be referred to as an ethylene stream. The olefin stream may be provided by the dehydration of ethanol or from an MTO unit. The input olefin stream may have a temperature of 60° C. (140° F.) to 150° C. (302° F.), preferably 80° C. (176° F.) to 100° C. (212° F.), and a pressure of 3.4 bar (500 psig) to 8.4 bar (1200 psig).

[0027] The olefin stream may first be contacted with a first-stage oligomerization catalyst to oligomerize ethylene and / or propylene into oligomers, and then with a second-stage oligomerization catalyst to further oligomerize the ethylene and / or propylene oligomers and unreacted ethylene and propylene. The oligomerization of ethylene generates a large exotherm. For example, the dimerization of ethylene can generate 612 kcal / kg (1100 BTU / lb) of heat. As a result, this large exotherm must be managed. Meanwhile, the dimerization of butene can generate 222 kcal / kg (400 BTU / lb) of heat.

[0028] Thus, the olefin stream in line 12 may be divided into multiple olefin streams. In FIG. 1 , the olefin stream is divided into four separate streams: a first olefin stream in input line 12a, a second olefin stream in input line 12b, a third olefin stream in input line 12c, and a fourth or final olefin stream in input line 12d. In one embodiment, the stream may not be able to pass through the control valve in input line 12d or through input line 12c, so that the input olefin stream is fed only to the upstream first-stage oligomerization catalyst beds 22a-22c or simply 22a-22b, respectively. More or fewer separate olefin streams may also be used. Up to six olefin streams are readily contemplated. The input olefin stream in line 12 may be divided into multiple olefin streams of equal portions. Alternatively, the input olefin stream in line 12 may be divided into unequal streams. For example, the input olefin stream may be divided into streams of increasing flow rates, with subsequent olefin streams having greater flow rates than preceding streams. In one embodiment, the input olefin stream is divided into three streams: a stream in which the flow rate of the input olefin stream from line 12 predominates (e.g., 40-60% in line 12a), a stream in which the flow rate of the input olefin stream from line 12 is less predominately present (e.g., 15-40% in lines 12b and 12c), and no stream in line 12d. Preferably, a greater flow rate of the input olefin stream is fed to bed 22a upstream of the first-stage oligomerization catalyst beds 22a-22c. In one embodiment, the input olefin stream from line 12 may be split, perhaps equally, only between lines 12a and 12b. Additionally, all of the input olefin stream in line 12 may be sent to input line 12a.

[0029] To manage the heat release, the olefin stream can be diluted with a diluent stream to provide a diluted olefin stream for absorbing the heat release. The diluent stream can include a paraffin stream in diluent line 14. The diluent stream in diluent line 14 can be added to the input olefin stream in line 12 before splitting the input olefin stream into multiple olefin streams. Preferably, a diluent stream is added to the first olefin stream in line 12a after splitting into multiple olefin streams to provide a first diluted olefin stream in line 16a, so that the diluent stream passes through all of the oligomerization reaction. Alternatively, the diluent stream can be split into multiple streams, with each diluent stream being added to a corresponding olefin stream. The diluent stream can have a volumetric flow rate that is 2 to 8 times, preferably 3 to 6 times, the mass flow rate of the input olefin stream. The first diluted olefin stream can contain 17 wt.% or less olefins, suitably 10 wt.% or less olefins, and preferably 6 wt.% or less olefins. The first dilute olefin stream may contain up to 14 wt.% ethylene, suitably up to 10 wt.% ethylene, and preferably up to 6 wt.% ethylene. Similarly, the first dilute olefin stream may contain up to 14 wt.% propylene, suitably up to 10 wt.% propylene, and preferably up to 6 wt.% propylene. The first dilute olefin stream in line 16a may be cooled in first feed cooler 18a to provide a first cooled, dilute olefin stream in line 20a and charged to a first bed 22a of first-stage oligomerization catalyst in first-stage oligomerization reactor 22. The cooled, diluted first feed olefin stream in line 20a may be charged at a temperature of 180°C (356°F) to 260°C (500°F) and a pressure of 3.5 MPag (500 psig) to 8.4 MPag (1200 psig). Feed cooler 18a may include a steam generator.

[0030] First-stage oligomerization reactor 22 can include a series of first-stage oligomerization catalyst beds 22a, 22b, 22c, and 22d for inputting each of the plurality of olefin streams 12a, 12b, 12c, and 12d, respectively. As previously mentioned, in one embodiment, there can be no input olefin stream in line 12d, and thus the input olefin stream from line 12 is fed only to the upstream first-stage oligomerization catalyst beds 12a-12c. Alternatively, as also previously mentioned, in one embodiment, there can be no input olefin stream in lines 12c or 12d, and thus the input olefin stream from line 12 is fed only to the upstream first-stage oligomerization catalyst beds 12a and 12b. The first-stage oligomerization reactor preferably contains four fixed oligomerization catalyst beds 22a, 22b, 22c, and 22d. It is also contemplated that each oligomerization catalyst bed 22a, 22b, 22c, and 22d may be in a dedicated first-stage oligomerization reactor, or that multiple first-stage oligomerization catalyst beds may be in two or more separate first-stage oligomerization reactors. Up to six first-stage oligomerization catalyst beds are readily contemplated. Parallel first-stage oligomerization reactors may be used when first-stage oligomerization reactor 22 is deactivated while it is regenerated in situ by burning coke from the catalyst, as described below.

[0031] The recycled olefin stream in line 26 can be injected into oligomerization catalyst beds 22a-22d. In one embodiment, the recycled olefin stream in line 26 is fed only to downstream oligomerization catalyst beds 22c and 22d. The recycled olefin stream in line 26 may be split into multiple recycled olefin streams in lines 26c and 26d and fed only to oligomerization catalyst beds 22c and 22d, respectively. In one embodiment, line 26c can have a predominant flow rate of the recycled olefin stream in line 26, and 26d can have the remainder of the flow rate of the recycled olefin stream in line 26. Preferably, a greater flow rate of the recycled olefin stream is fed to the downstream catalyst bed 22d of downstream catalyst beds 22c and 22d to achieve a similar lean olefin concentration to manage exotherms.

[0032] The first cooled, diluted olefin stream may be introduced into the first upstream first-stage oligomerization catalyst bed 22a in line 20a, preferably in downflow operation. However, upflow operation may be preferred. As ethylene and / or propylene oligomerization occurs in the first upstream first-stage oligomerization catalyst bed 22a, an exotherm is generated due to the exothermic nature of the ethylene and / or propylene oligomerization reaction. As the first olefin stream is oligomerized, a first oligomerized olefin stream is produced in the upstream first oligomerization effluent line 24a at an elevated outlet temperature despite the cooling and dilution. The elevated outlet temperature is limited to 25°C (45°F) to 61°C (110°F) above the inlet temperature to the upstream first first-stage catalyst bed 22a.

[0033] The second olefin stream in line 12b can be diluted with a first oligomerized olefin stream in an upstream first oligomerization effluent line 24a removed from the upstream first-stage oligomerization reactor 22 to provide a second diluted olefin stream in line 16b. The upstream first oligomerized olefin stream in line 24a comprises a diluent stream from diluent line 14 added to the first olefin stream in line 12a. The second diluted olefin stream can contain up to 22 wt% olefins, suitably up to 15 wt% olefins, and preferably up to 10 wt% olefins. The second diluted olefin stream can contain up to 15 wt% ethylene, suitably up to 10 wt% ethylene, and preferably up to 6 wt% ethylene. The second diluted olefin stream can contain up to 15 wt% propylene, suitably up to 10 wt% propylene, and preferably up to 6 wt% propylene. The second dilute olefin stream in line 16b is cooled in a second charge air cooler 18b, which may be located external to the downstream first-stage oligomerization reactor 22, to provide a second cooled dilute olefin stream in line 20b, which may be injected into the first-stage oligomerization reactor 22b downstream of the oligomerization catalyst in the first-stage oligomerization reactor 22. The charge air cooler 18b may include a steam generator. The second cooled dilute olefin stream in line 20b may be injected at a temperature of 180°C (356°F) to 260°C (500°F) and a pressure of 3.4 MPa (500 psig) to 8.4 MPa (1200 psig). The second dilute olefin stream comprises diluent and olefins from the first oligomerization olefin stream. The olefins from the first oligomerization olefin stream are oligomerized in the downstream first-stage catalyst bed 22b. Oligomerization of ethylene, propylene, and oligomers in the second olefin stream in the first first stage bed 22b downstream of the oligomerization catalyst produces a downstream first first stage oligomerized olefin stream at an elevated outlet temperature in downstream first oligomerization effluent line 24b, which may be limited to 25°C (45°F) to 61°C (110°F) above the inlet temperature to catalyst bed 22b.

[0034] The third olefin stream in line 12c can be diluted with the downstream first-stage oligomerized olefin stream in line 24b removed from the second first-stage oligomerization reactor 22b and mixed with the first recycled olefin stream in line 26c to provide the upstream second first-stage diluted olefin stream in line 16c. The downstream first-stage oligomerized olefin stream in line 24b comprises the diluent stream from diluent line 14 added to the first olefin stream in line 12a. The third diluted olefin stream can contain up to 23 wt% olefins, suitably up to 15 wt% olefins, and preferably up to 10 wt% olefins. The third diluted olefin stream can contain up to 13 wt% ethylene, suitably up to 10 wt% ethylene, and preferably up to 6 wt% ethylene. The third diluted olefin stream can contain up to 13 wt% propylene, suitably up to 10 wt% propylene, and preferably up to 6 wt% propylene. The third dilute olefin stream in line 16c is cooled in a third charge air cooler 18c, which may be located external to the first-stage oligomerization reactor 22, to provide a third cooled dilute olefin stream in line 20c, which may be injected into a third bed 22c of oligomerization catalyst in the first-stage oligomerization reactor 22. The charge air cooler 18c may be equipped with a steam generator. The third cooled dilute olefin stream in line 20c may be injected at a temperature of from 180°C (356°F) to 260°C (500°F) and a pressure of from 3.4 MPag (500 psig) to 8.4 MPag (1200 psig). The third dilute olefin stream comprises diluent and olefins from the downstream second first-stage oligomerization olefin stream and the first recycled olefin stream. Olefins from the downstream first first-stage oligomerized olefin stream and the first recycled olefin stream are oligomerized in the upstream second first-stage catalyst bed 22c. Oligomerization of ethylene and propylene in the third dilute olefin stream in the upstream second first-stage oligomerization catalyst bed 22c produces an upstream second first-stage oligomerized olefin stream at an elevated exit temperature in the upstream second first-stage oligomerization effluent line 24c.In one embodiment, the upstream second first-stage oligomerized olefin stream is the penultimate oligomerized olefin stream, and the upstream second first-stage oligomerization effluent line 24c is the penultimate oligomerization effluent line 24c. The elevated outlet temperature is limited to 25°C (45°F) to 61°C (110°F) above the inlet temperature to catalyst bed 22c.

[0035] The fourth olefin stream in line 12d can be diluted with the upstream second first-stage or penultimate oligomerized olefin stream in line 24c removed from the upstream second first-stage oligomerization reactor 22 and the second recycled olefin stream in line 26d to provide a fourth dilute olefin stream in line 16d. The upstream second first-stage or penultimate oligomerized olefin stream in line 24c comprises the diluent stream from diluent line 14 added to the first olefin stream in line 12a. The fourth dilute olefin stream can contain 24 wt% or less olefins, suitably 18 wt% or less olefins, and preferably 10 wt% or less olefins. The fourth dilute olefin stream can contain 11 wt% or less ethylene, suitably 8 wt% or less ethylene, and preferably 6 wt% or less ethylene. The fourth dilute olefin stream can contain 11 wt% or less propylene, suitably 8 wt% or less propylene, and preferably 6 wt% or less propylene. The fourth dilute olefin stream in line 16d is cooled in a fourth charge air cooler 18d, which may be located external to the first-stage oligomerization reactor 22, to provide a fourth cooled dilute olefin stream in line 20d, which may be injected into the second downstream first-stage bed 22d in the first-stage oligomerization reactor 22. The charge air cooler 18d may be equipped with a steam generator. The fourth cooled dilute olefin stream in line 20d may be injected at a temperature of 180°C (356°F) to 260°C (500°F) and a pressure of 3.4 MPag (500 psig) to 8.4 MPag (1200 psig). The fourth or final dilute olefin stream comprises diluent and olefins from the upstream second first-stage or penultimate oligomerization olefin stream and the second recycled olefin stream. Olefins from the upstream second first-stage or penultimate oligomerized olefin stream and the second recycled olefin stream are oligomerized in downstream second first-stage catalyst bed 22d. Oligomerization of ethylene and propylene in the fourth olefin stream in downstream second first-stage oligomerization catalyst bed 22d produces a downstream second first-stage oligomerized olefin stream at an elevated exit temperature in fourth oligomerization effluent line 24d.The elevated outlet temperature is limited to 25°C (45°F) to 61°C (110°F) above the inlet temperature to the downstream second first stage catalyst bed 22d.

[0036] Recycle olefin streams 26c and 26d provide olefins that can be oligomerized over catalyst beds 22c and 22d, respectively, but also can help manage the exotherm generated during the oligomerization of ethylene.

[0037] In one embodiment, the downstream second first-stage oligomerization olefin stream is the final olefin stream, and the downstream second first-stage oligomerization effluent line 24d is the final oligomerization effluent line 24d.

[0038] The oligomerization reaction takes 0.5 to 10 hours based on the olefin. -1 The process is carried out primarily in the liquid phase or in a mixed gas-liquid phase in an LHSV of 1000 MPa. The present inventors have found that a majority of the ethylene in the olefin stream is converted to higher olefins. Typically, at least 20-40 mole percent of the ethylene oligomerizes across the oligomerization catalyst bed. Ethylene initially oligomerizes over the catalyst to butenes.

[0039] The first-stage oligomerization catalyst can include a zeolite catalyst. The first-stage oligomerization catalyst can be considered a solid acid catalyst. The zeolite can comprise 5 to 95 wt. % of the catalyst, e.g., 5 to 85 wt. %. Suitable zeolites include zeolites having a structure from one of the following classes: MFI, MEL, ITH, IMF, TUN, FER, BEA, FAU, BPH, MEI, MSE, MWW, UZM-8, MOR, OFF, MTW, TON, MTT, AFO, ATO, and AEL. Three-letter codes for zeotypes are as defined by the Structure Commission of the International Zeolite Association and maintained at http: / / www.iza-structure.org / databases. UZM-8 is as described in U.S. Patent No. 6,756,030. In a preferred embodiment, the first-stage oligomerization catalyst may comprise a zeolite having a framework with a 10-ring pore structure. Examples of suitable zeolites having a 10-ring pore structure include TON, MTT, MFI, MEL, AFO, AEL, EUO, and FER. In a further preferred embodiment, the first-stage oligomerization catalyst comprising a zeolite having a 10-ring pore structure may comprise a one-dimensional pore structure. A one-dimensional pore structure refers to a zeolite containing non-intersecting pores that are substantially parallel to one of the crystal axes. The pores preferably extend throughout the zeolite crystal. A suitable example of a zeolite having a 10-ring one-dimensional pore structure may include MTT. In a further embodiment, the first-stage oligomerization catalyst comprises an MTT zeolite.

[0040] The first-stage oligomerization catalyst can be formed by combining a zeolite with a binder and then forming the catalyst into pellets. The pellets can optionally be treated with a phosphorus reagent to produce a zeolite having a phosphorus component of 0.5 to 15% by weight of the treated catalyst. The binder is used to impart hardness and strength to the catalyst. Binders include alumina, aluminum phosphate, silica, silica-alumina, zirconia, titania, and combinations of these metal oxides, as well as other refractory oxides and clays such as montmorillonite, kaolin, palygorskite, smectite, and attapulgite. Preferred binders are aluminum-based binders such as alumina, aluminum phosphate, silica-alumina, and clays.

[0041] One of the components of the catalyst binder utilized in this disclosure is alumina. The alumina source can be any of a variety of hydrous aluminum oxides or alumina gels, such as alpha-alumina monohydrate with boehmite or pseudo-boehmite structure, alpha-alumina trihydrate with gibbsite structure, or beta-alumina trihydrate with bayerite structure. A suitable alumina is available from UOP LLC under the VERSAL trademark. A preferred alumina is available from Sasol North America Alumina Product Group under the Catapal trademark. This material is an extremely high purity alpha-alumina monohydrate (pseudo-boehmite) that has been shown to yield high purity gamma-alumina after high temperature calcination.

[0042] Suitable first-stage oligomerization catalysts are prepared by mixing proportional volumes of zeolite and alumina to achieve the desired zeolite to alumina ratio. In embodiments, the MTT content may be 5 to 85, e.g., 20 to 82 wt. % MTT zeolite, with the remainder being alumina powder to provide a suitably supported catalyst. Silica supports are also contemplated.

[0043] A monobasic acid such as nitric acid or formic acid may be added to the mixture in aqueous solution to peptize the alumina in the binder. Additional water may be added to the mixture to provide sufficient wettability to form a dough with sufficient consistency to be extruded or spray-dried. An extrusion aid such as cellulose ether powder may also be added. A preferred extrusion aid is available from The Dow Chemical Company under the Methocel trademark.

[0044] The paste or dough may be prepared in the form of shaped particles; a preferred method is to extrude the dough through a die having openings of the desired size and shape, followed by dividing the extruded material into extrudates of the desired length and drying. A further calcination step may be used to provide additional strength to the extrudates. Typically, calcination is carried out in a stream of air at a temperature of 260°C (500°F) to 815°C (1500°F). The MTT catalyst is not selective to neutralize acidic sites such as amines.

[0045] The extruded particles can have any suitable cross-sectional shape, i.e., symmetrical or asymmetrical, but most often have a symmetrical cross-sectional shape, preferably spherical, cylindrical, or multilobal. The cross-sectional diameter of the particles can be as small as 40 μm. However, it is usually between 0.635 mm (0.25 inch) and 12.7 mm (0.5 inch), preferably between 0.79 mm (1 / 32 inch) and 6.35 mm (0.25 inch), and most preferably between 0.06 mm (1 / 24 inch) and 4.23 mm (1 / 6 inch).

[0046] In one exemplary embodiment, an MTT-type zeolite catalyst disposed on a high purity pseudoboehmite alumina substrate in a ratio of 90 / 10 to 20 / 80, preferably 20 / 80 to 50 / 50, is provided in a catalyst bed or more in the first stage oligomerization reactor 22.

[0047] The first-stage oligomerization catalyst can be regenerated upon deactivation. Suitable regeneration conditions include subjecting the first-stage oligomerization catalyst, for example, in situ, to hot air at 500°C for three hours. In practice, regeneration can be accomplished by purging with hot nitrogen at 300-500°C, preferably 350-450°C, to strip heavy hydrocarbon species from the spent catalyst. Alternatively, the spent catalyst can be purged with a stream of light olefins or washed with a solvent or another hydrocarbon stream. The purge or wash step is followed by 20-40 hours of coke burning in 0.3-0.7 mol% oxygen and proof burning in 3-10 mol% oxygen until all coke has burned or until at least 1.2 wt% or less of the coke has burned on the catalyst. A swinging bed system can be used with an alternative first-stage oligomerization reactor to facilitate regeneration without downtime. Alternatively, a lead-lag swinging bed system can be employed. The regeneration gas stream can be input to the first-stage oligomerization reactor 22 in need of regeneration. The regeneration gas can comprise air with either increased or decreased oxygen concentration. The activity and selectivity of the regenerated catalyst are comparable to that of fresh catalyst.

[0048] Zeolite catalysts are advantageous as first-stage oligomerization catalysts. Zeolite catalysts have a relatively low susceptibility to oxygenate (oxygenate) contamination. As a result, less oxygenate removal is required from the olefin feed in line 12 when produced from an ethanol dehydration process.

[0049] The final oligomerized olefin stream in final oligomerization effluent line 24d has an increased concentration of ethylene dimers and oligomers compared to the input olefin stream in line 12. The oligomerized olefin stream is cooled to generate steam in steam generator 27, then cooled by heat exchange with the oligomerized stream in line 37 in heat exchanger 29, and then cooled in air cooler 31 before being input to second-stage oligomerization reactor 32 in oligomerization input line 28. Second-stage oligomerization reactor 32 can include a series of second-stage oligomerization catalyst beds 32a and 32b. It is contemplated that each second-stage oligomerization catalyst bed 32a and 32b can be in a dedicated second-stage oligomerization reactor, or that multiple second-stage oligomerization catalyst beds can be in two or more separate second-stage oligomerization reactors. Two second-stage oligomerization catalyst beds are readily contemplated. A parallel second stage oligomerization reactor can be used when the second stage oligomerization reactor 32 is deactivated while the second stage oligomerization reactor 32 is regenerated in situ by burning coke from the catalyst.

[0050] To achieve the most desirable olefin products, second-stage oligomerization reactor 32 operates at a temperature of 38°C (100°F) to 180°C (356°F). Second-stage oligomerization reactor 32 is operated at a pressure of 4.9 MPa (700 psig) to 7.6 MPa (1100 psig), more preferably 3.4 MPa (500 psig) to 6.9 MPa (1000 psig). A first oligomerization stream from first second-stage oligomerization catalyst bed 32a may be removed from first second-stage oligomerization reactor 32 in line 33, cooled in cooler 34 back to a temperature of 38°C (100°F) to 180°C (356°F), and charged to second second-stage oligomerization catalyst bed 32b in line 35.

[0051] The second-stage oligomerization reactor 32 may be in downstream communication with the first-stage oligomerization reactor 22. The second-stage oligomerization reactor 32 preferably operates in downflow operation; however, upflow operation may be preferred. The input oligomerized olefin stream is contacted with a second-stage oligomerization catalyst to dimerize and trimerize C2 to C8 olefins to provide distillate range olefins. For the second-stage oligomerization reactor 32, process conditions are selected to produce a higher proportion of jet range olefins, which, when hydrogenated in subsequent steps as described below, result in desired jet range hydrocarbon products. A majority of the unconverted ethylene in the input oligomerized olefin stream is oligomerized in the second-stage oligomerization reactor 32. In one embodiment, at least 90 mole percent of the ethylene in the input oligomerized olefin stream is oligomerized in the second-stage oligomerization reactor 32. The second stage oligomerization catalyst, which is a metal, is efficient at dimerizing non-dimerized ethylene. An oligomerized olefin stream having an increased average carbon number greater than the oligomerized olefin stream charged in oligomerization charge line 28 exits oligomerization reactor 32 in line 37.

[0052] The second-stage oligomerization catalyst is preferably an amorphous silica-alumina base having a metal from either Group VIII and / or Group VIB of the Periodic Table, using Chemical Abstracts Service notation. In one embodiment, the catalyst has a Group VIII metal promoted with a Group VIB metal. Typically, the silica and alumina are present only in the base, so the silica to alumina ratio is the same for both the catalyst and the base. The metal can be impregnated onto the silica-alumina base or ion-exchanged into the silica-alumina base. Co-mulling is also contemplated. The catalyst of the present invention can have a low temperature acidity ratio of at least 0.15, suitably 0.2, and preferably greater than 0.25, as measured by Ammonia Temperature Programmed Desorption (TPD), as described below. Additionally, suitable second-stage oligomerization catalysts have a low temperature acidity ratio of 50 to 400 m as determined by the nitrogen BET method. 2 / g of surface area.

[0053] A preferred second-stage oligomerization catalyst comprises an amorphous silica-alumina support. One of the components of the catalyst support utilized in the present invention is alumina. The alumina can be any of a variety of hydrous aluminum oxides or alumina gels, such as alpha-alumina monohydrate with a boehmite or pseudo-boehmite structure, alpha-alumina trihydrate with a gibbsite structure, or beta-alumina trihydrate with a bayerite structure. A particularly preferred alumina is available from Sasol North America Alumina Product Group under the Catapal trademark. This material is an extremely high-purity alpha-alumina monohydrate (pseudo-boehmite) that has been shown to yield high-purity gamma-alumina after calcination at high temperatures. Another component of the catalyst support is amorphous silica-alumina. Suitable silica-alumina having a silica to alumina ratio of 2.6 is available, for example, from CCIC, a subsidiary of JGC in Japan.

[0054] Another component utilized in the preparation of the second-stage oligomerization catalyst utilized in the present invention is a surfactant. The surfactant is preferably mixed with the alumina and silica-alumina powders described above. The resulting surfactant, alumina, and silica-alumina mixture is then formed, dried, and calcined as described below. Calcination effectively removes the organic components of the surfactant by combustion, but only after the surfactant has faithfully performed its function in accordance with the present invention. Any suitable surfactant can be utilized. A preferred surfactant is a surfactant selected from the series of commercially available surfactants sold by Solvay SA under the "Antarox" trademark. "Antarox" surfactants are generally characterized as modified linear aliphatic polyethers and are low-foaming biodegradable detergents and wetting agents.

[0055] A suitable silica-alumina mixture is prepared by mixing proportional volumes of silica-alumina and alumina to achieve the desired silica to alumina ratio. In embodiments, 75-95 wt. % amorphous silica-alumina having a silica to alumina ratio of 2.6 and 10-20 wt. % alumina powder provides a suitable support. In embodiments, other ratios of amorphous silica-alumina to alumina may be suitable.

[0056] Any convenient method can be used to incorporate the surfactant into the mixture of silica-alumina and alumina. The surfactant is preferably mixed during the mixing and formation of the alumina and silica-alumina. A preferred method is to mix an aqueous solution of the surfactant with the alumina and silica-alumina blend prior to final formation of the carrier. The surfactant is preferably present in the paste or dough in an amount of 0.01 to 10% by weight, based on the weight of the alumina and silica-alumina.

[0057] A monobasic acid such as nitric acid or formic acid can be added to the mixture in aqueous solution to peptize the alumina in the binder. Additional water can be added to the mixture to provide sufficient wettability to form a dough with sufficient consistency to be extruded or spray dried.

[0058] The paste or dough may be prepared in the form of shaped particles; a preferred method is to extrude a dough mixture of alumina, silica-alumina, surfactant, and water through a die having openings of the desired size and shape, after which the extruded material is divided into extrudates of the desired length and dried. A further calcination step may be used to provide additional strength to the extrudates. Typically, calcination is carried out in a stream of dry air at a temperature of 260°C (500°F) to 815°C (1500°F).

[0059] The extruded particles can have any suitable cross-sectional shape, i.e., symmetrical or asymmetrical, but most often have a symmetrical cross-sectional shape, preferably spherical, cylindrical, or multilobal. The cross-sectional diameter of the particles can be as small as 40 μm. However, it is usually between 0.635 mm (0.25 inch) and 12.7 mm (0.5 inch), preferably between 0.79 mm (1 / 32 inch) and 6.35 mm (0.25 inch), and most preferably between 0.06 mm (1 / 24 inch) and 4.23 mm (1 / 6 inch).

[0060] Typical properties of the amorphous silica-alumina supports utilized herein are total pore volume, average pore diameter, and a surface area large enough to provide substantial space and area for depositing the active metal components. The total pore volume of the support, as measured by conventional mercury porosimetry, is typically 0.2-2.0 cc / gram, preferably 0.25-1.0 cc / gram, and most preferably 0.3-0.9 cc / gram. Typically, the amount of pore volume of the support in pores with diameters greater than 100 angstroms is less than 0.1 cc / gram, preferably less than 0.08 cc / gram, and most preferably less than 0.05 cc / gram. Surface area, as measured by the BET method, is typically less than 50 m 2 / g or more, e.g. 200m 2 / g, preferably at least 250m 2 / gram, most preferably 300m 2 grams ~ 400m 2 / gram.

[0061] To prepare the catalyst, the support material is combined with one or more precursors of at least one metal component from Group VIII or Group VIB of the Periodic Table, such as by single or multiple impregnation of calcined amorphous refractory oxide support particles. The Group VIII metal, preferably nickel, should be present in a concentration of 0.5 to 15 wt. %, and the Group VIB metal, preferably tungsten, should be present in a concentration of 0 to 12 wt. %. Impregnation can be accomplished by any method known in the art, such as spray impregnation, in which a solution containing the metal precursors in dissolved form is sprayed onto the support particles. Another method is a multi-dip procedure, in which the support material is repeatedly contacted with the impregnation solution, with or without intermittent drying. Yet another method involves immersing or circulating the support in a large volume of the impregnation solution, and yet another method is the pore volume or pore saturation technique, in which the support particles are introduced into a volume of impregnation solution just sufficient to fill the pores of the support. In some cases, the pore saturation technique may be modified to utilize an impregnation solution having a volume between 10 percent less and 10 percent more than the volume that would just fill the pores.

[0062] If the active metal precursors are incorporated by impregnation, a subsequent or second calcination at elevated temperatures, for example, 399°C (750°F) to 760°C (1400°F), converts the metals to their respective oxide forms. Optionally, a calcination may be performed after each individual active metal impregnation. Subsequent calcinations result in a catalyst containing the active metals in their respective oxide forms.

[0063] The preferred second-stage oligomerization catalyst of the present invention is in the form of 3.175 mm (0.125 inch) extrudates of an amorphous silica-alumina substrate impregnated with 0.5 to 15 weight percent nickel and has a density of 0.45 to 0.65 g / ml. It is also contemplated that the metal can be incorporated onto the support by other methods such as ion exchange and co-mulling.

[0064] The second-stage oligomerization catalyst can be regenerated upon deactivation. Suitable regeneration conditions include subjecting the catalyst to hot air at 500°C for three hours, for example, in situ. In practice, regeneration can be accomplished by purging with hot nitrogen at 300-500°C, preferably 350-450°C, to strip heavy hydrocarbon species from the spent catalyst. Alternatively, the spent catalyst can be purged with a stream of light olefins or washed with a solvent or another hydrocarbon stream. The purging or washing step is followed by 20-40 hours of coke combustion in 0.3-0.7 mol% oxygen and proof combustion in 3-10 mol% oxygen until all coke is burned. To facilitate regeneration without downtime, a swing-bed system can be used with an alternative second-stage oligomerization reactor. The regeneration gas can contain air with increased or decreased oxygen concentrations. The activity and selectivity of the regenerated catalyst are comparable to that of fresh catalyst.

[0065] The second-stage oligomerization reaction is also exothermic in nature. The final oligomerized olefin stream in line 24d comprises the diluent stream from diluent line 14, added to the first olefin stream in line 12a and conveyed through oligomerization catalyst beds 22a-22d. The diluent stream is then conveyed in line 28 to second-stage oligomerization reactor 32 to absorb the exotherm in the second-stage oligomerization reactor. It is contemplated that the diluent may be introduced into second-stage oligomerization catalyst beds 22a-22d with or without first passing the diluent through the first-stage oligomerization catalyst beds.

[0066] When the oligomerization reaction is carried out according to the above process conditions, C4 olefin conversions of 95% or more, or even 97% or more, are achieved. The resulting oligomerized olefin stream in line 37 contains a plurality of olefin products that are distillate range hydrocarbons.

[0067] The oligomerized olefin stream in line 37, which has been heat exchanged in heat exchanger 29 with the final oligomerized olefin stream in line 24d, having an increased C9+ olefin concentration compared to the oligomerized olefin stream in line 28, and the olefin splitter bottoms stream in line 41 in heat exchanger 43, are reduced in pressure and fed to olefin splitter column 36. The oligomerized olefin stream in line 37 has a temperature of 140°C (284°F) to 200°C (392°F) and a pressure of 3.9 MPa (gauge) (550 psig) to 6.3 MPa (gauge) (900 psig).

[0068] In olefin splitter column 36, jet range hydrocarbons, typically oligomers boiling at temperatures lower than C8- hydrocarbons having atmospheric boiling points below 150°C, are separated into an olefin splitter overhead stream in overhead line 38 from a bottoms stream in bottoms line 40 containing distillate range C9+ hydrocarbons, typically C9 to C22 olefins. Olefin splitter column 36 can operate at a bottoms temperature of 200°C (400°F) to 315°C (600°F) and an overhead pressure of 35 kPa (gauge) (5 psig) to 350 kPa (gauge) (50 psig). It is envisioned that olefin splitter column 36 may be two columns.

[0069] The olefin splitter overhead stream may be cooled to 66°C (150°F) to 93°C (200°F), with the resulting condensed liquid portion refluxed from olefin splitter receiver 42 back to olefin splitter column 36. The net vapor stream in receiver overhead line 44 from olefin splitter receiver 42 can be compressed to oligomerization pressure in off-gas compressor 46 to provide, after cooling, a light oligomer stream in line 48 in either the vapor or liquid phase. Alternatively, the olefin splitter overhead stream in receiver overhead line 44 can be fully condensed, perhaps by cooling in an external refrigeration loop, to provide a liquid light oligomer stream in line 48. Line 48 may also be withdrawn from receiver 42. The light oligomer stream in line 48 may be divided into a light olefins drag stream in line 50 and an oligomers recycle stream in line 26 which may be recycled to second-stage oligomerization reactor 32 or to first-stage oligomerization reactor 22. The light olefins drag stream in line 50 may comprise 1 to 15 weight percent of the light oligomer stream in line 48. The light oligomers stream in line 48 may comprise 30 to 80 weight percent light olefins.

[0070] In one embodiment, the oligomer recycle stream in line 26 can be combined with the final oligomerized olefin stream in final dimerization effluent line 24d to provide an input oligomerization stream in line 28 for input to second-stage oligomerization reactor 32. The oligomer recycle stream in line 26 can be combined with the first diluent olefin stream in line 16a or appropriately divided by first through fourth diluent olefin streams in lines 16a-16d to oligomerize unreacted C4-C7 olefins. In a preferred embodiment, the oligomer recycle stream in line 26 can be divided into a first oligomer recycle stream in line 26c and a second oligomer recycle stream in line 26d. The first oligomer recycle stream in line 26c may be combined with the upstream second first-stage oligomerized olefin stream in downstream first-stage oligomerization effluent line 24b and possibly a third olefin stream in third olefin line 12c to provide a third dilute olefin stream in line 16c for input to the upstream second first-stage oligomerization catalyst bed 22c. The second oligomer recycle stream in line 26d may be combined with the upstream second first-stage oligomerized olefin stream in upstream second first-stage oligomerization effluent line 24c and possibly a third olefin stream in third olefin line 12c to provide a fourth dilute olefin stream in line 16d for input to the downstream second first-stage oligomerization catalyst bed 22d.

[0071] The heavy olefins stream in splitter bottoms line 40 may be split into a reboil stream in line 51 that is reboiled back to olefin splitter column 36 and a heavy olefins stream in net splitter bottoms line 41. The heavy olefins stream in net bottoms line 30 is cooled by heat exchange with an oligomerized olefins stream in line 37 before being transported to hydrogenation section 110 of Figure 2. The reboil stream in line 51 may be heated by heat exchange with a reboil stream in line 83 from jet fractionation bottoms line 76 that is returned to the jet fractionation column in line 85 of Figure 2.

[0072] Turning to the hydrogenation section 110 of FIG. 2, the heavy olefin stream in net olefin splitter bottoms line 30 from FIG. 1, containing C9+ oligomerized olefins in the distillate range, can be hydrogenated in hydrogenation reactor 52 to saturate the olefinic bonds and provide a fuel. This step is performed to ensure that the product motor fuel meets or exceeds the thermal oxidation requirements specified in ASTM D7566-10a for hydrotreated synthetic paraffinic kerosene (SPK). Furthermore, saturating the oligomerized heavy olefins results in a paraffinic stream that can be used as a diluent stream in line 14. The heavy olefin stream in line 30 can be cooled to produce steam and combined with a light olefin drag stream containing C2-C8 olefins, also in line 50 from FIG. 1, to produce a mixed olefin stream in line 54. Alternatively, the combined olefin stream in line 54 can be combined with a hydrogen stream in line 56 to provide a combined hydrogenation input stream in line 58 that is cooled and input to hydrogenation reactor 52 at 125°C (257°F) to 315°C (600°F) and 3.5 MPa (500 psig) to 6.9 MPa (1000 psig). An excess of hydrogen, such as 1.5 to 2.5 stoichiometric hydrogen, can be used to ensure complete saturation.

[0073] Hydrogenation is typically carried out using conventional hydrogenation or hydrotreating catalysts, which may include, for example, metal catalysts containing palladium, rhodium, nickel, ruthenium, platinum, rhenium, cobalt, molybdenum, or combinations thereof, and supported metal catalysts thereof. The catalyst support may be any solid, inert material, including, but not limited to, oxides such as silica, alumina, titania, calcium carbonate, barium sulfate, and carbon. The catalyst support may be in the form of a powder, granules, pellets, etc.

[0074] In an exemplary embodiment, the hydrogenation is carried out in a hydrogenation reactor 52 containing an alumina-supported platinum catalyst, for example, 0.5 wt % to 0.9 wt % alumina-supported platinum catalyst. The hydrogenation reactor 52 converts the olefins to paraffin products having the same carbon number distribution as the olefins, thereby forming paraffins in the distillate range suitable for use as jet and diesel fuels.

[0075] The saturated heavy stream discharged from the hydrotreating reactor 52 in line 60 may be cooled by heat exchange with a saturated heavy liquid stream in a separator bottoms line 66 and fed to a hydrotreating separator 62. In the hydrotreating separator 62, the saturated heavy stream is separated into a hydrotreating separator vapor stream in an overhead line 64 and a saturated heavy liquid stream in a hydrotreating separator bottoms line 66. A purge in line 65 may be removed from the hydrotreating separator vapor stream in line 64, and the remainder may be compressed and combined with make-up hydrogen in line 68 to provide a hydrogen stream in line 56. The saturated heavy liquid stream in the bottoms line 66 may be heated by heat exchange with the saturated heavy stream in line 60 and a diluent stream in line 14 and fed to a jet fractionation column 70. In one embodiment, a high temperature and low temperature separator system may be used in place of a single hydrotreating separator 62.

[0076] The saturated heavy liquid stream in bottoms line 66 may be fed to jet fractionation column 70 without prior stripping in a stripper column. Alternatively, a stripper column may be utilized upstream of jet fractionation column 70. In jet fractionation column 70, the saturated heavy liquid stream may be separated into a net off-gas stream in net overhead line 80, a green jet stream in net liquid overhead line 74, and a green diesel stream in net bottoms line 82. Jet fractionation column 70 may operate at a bottoms temperature of 316°C (600°F) to 482°C (900°F) and an overhead pressure of 35 kPa (5 psig) to 350 kPa (50 psig).

[0077] The jet fractionation overhead stream in overhead line 72 may be cooled, and a resulting condensed stream is produced in line 79 from the bottom of receiver 78. A portion of the condensate in line 79 is refluxed back to jet fractionation column 70, while the jet fuel stream in line 84 is transported to jet stripper column 90. A net off-gas stream comprising C8-hydrocarbons is taken from jet fractionation receiver 78 in receiver overhead line 80. The majority of the hydrocarbons in the net off-gas stream in receiver overhead line 80 are lighter hydrocarbons and can be used to fuel the reboilers for jet fractionation column 70, olefin splitter column 36, and / or other complex furnaces.

[0078] Jet stripper column 90 strips light ends from the jet fuel stream in line 84 and sends them overhead in line 92, returning them to condenser 73 along with the jet fractionation overhead stream in line 72. The stripped jet fuel product is taken in jet stripper bottoms line 94, while a portion is reboiled and returned to jet stripper column 90. A jet fuel product stream in line 74 is removed from the stripped jet fuel product in line 94, cooled in cooler 95, and recovered as a jet fuel product. The green jet stream removed in line 74 comprises C9 to C17 hydrocarbons in the kerosene range and can be cooled and removed as a product meeting applicable SPK specifications. In an alternative embodiment, the green jet stream can be removed from an id line from the side of jet fractionation column 70.

[0079] The green diesel bottoms stream in bottoms line 76 can be split into a reboil stream in line 81 that is reboiled back to jet fractionation column 70, a green diesel product stream in line 82, and a diluent stream in line 14. The diluent stream in line 14 can be cooled by heat exchange with separator bottoms line 66 and steam generation and recycled to combine with the olefin stream in line 12, preferably the first olefin stream in line 12a, in oligomerization section 10 of FIG. 1 to provide a first diluted olefin stream in line 16a to absorb heat generation in first-stage oligomerization reactor 22. Because the green diesel in diluent line 14 is paraffinic, it is inert to the oligomerization and hydrogenation reactions it may undergo. Both the jet fuel stream in line 74 and the diesel stream in line 82 can be cooled and fed to their respective fuel pools. The diesel stream meets ASTM D975 standards for diesel. The reboil stream in line 81 may be diverted in line 83 to olefin splitter column 70 for reboiling the reboil stream in line 51 from the olefin splitter bottoms stream in line 40 in Figure 1. The cooled reboil stream may be returned in line 85 where it is heated to boiling in a heater and returned to jet fractionation column 70.

[0080] The disclosed process can efficiently produce green jet fuel and green diesel fuel starting from ethylene that meet applicable fuel requirements while managing heat generation. Carbon recovery in the process can exceed 95%.

[0081] At the end of 15 or 20 days, suitably after the end of two weeks, or more preferably after at least 30 days, after reaching maximum temperature to compensate for declining catalyst activity, the catalyst cycle in both the first-stage oligomerization reactor 22 and / or the second-stage oligomerization reactor 32 must be restarted. The catalysts must be regenerated to restore their initial activity. Regeneration of the zeolite-based oligomerization catalyst in the first-stage oligomerization reactor 22 is accomplished by taking the first-stage oligomerization reactor 22 offline by stopping olefin input to the first-stage oligomerization reactor 22. The reactor is depressurized to 280 kPa(g) (40 psig) to 600 kPa(g) (85 psig) and the liquid is discharged, possibly by pumping to the olefin splitter column 36. The first-stage oligomerization reactor 22 is then purged with a hot, dry purge gas to strip the heavy hydrocarbons C8 to C21 from the first-stage oligomerization catalyst. An inert gas such as nitrogen, a hydrocarbon stream, or a solvent can be used as the purge gas. The purge gas can be introduced downflow into the first-stage oligomerization reactor 22 at 350-450°C and 175 kPa(g) (25 psig) to 280 kPa(g) (40 psig), which is high enough to recover the light olefins in the liquid phase. Once the liquid olefins are completely recovered, the flow of purge gas to the first-stage oligomerization reactor 22 is stopped. An air supply is then sent to the first-stage oligomerization reactor for 10-25 hours. At the inlet, the oxygen concentration should not exceed 0.3-0.7 mol%, and at the outlet, the temperature should be below 400°C to 500°C. Once the heat of combustion no longer increases, the oxygen concentration can be increased to 5-10 mole percent to prove sufficient carbon combustion. GHSV based on total flow rate is maintained for 400-4000 hours. -1 and preferably 1000 hours -1The oxygen can then be purged from the first stage oligomerization reactor by an inert gas purge or by filling the first stage oligomerization reactor with a paraffinic liquid. Regeneration of the second stage oligomerization catalyst comprising metal on a support in second stage oligomerization reactor 32 can be accomplished following the same procedure.

[0082] The present inventors have developed a process for regenerating the catalyst systems of both the first stage oligomerization reactor 22 and the second stage oligomerization reactor 32 that allows for continuous operation. Figure 3 shows the regeneration process for the first stage oligomerization reactor 22.

[0083] The process may utilize three first-stage oligomerization reactors 22: first reactor 22A, second reactor 22B, and third reactor 22C. The three reactors are switched between lead, lag, and regeneration modes. In Figure 3, first reactor 22A is in lead mode, second reactor 22B is in lag mode, and third reactor 22C is in regeneration mode. Figure 3 is related to Figure 1. In Figure 3, the unloaded valves are open and the loaded valves are closed. Additionally, capital letters in reference letters are distinguished from lowercase letters.

[0084] Line 20a in FIG. 1 introduces a first cooled, diluted olefin stream into a first, first-stage oligomerization catalyst bed 22a upstream of a first reactor 22A in lead mode through an open valve on a connecting line 120. The input olefin stream is oligomerized in the first, first-stage oligomerization catalyst bed 22a to produce an upstream first oligomerized olefin stream. The corresponding valves on connecting lines 121 and 122 to a second reactor 22B and a third reactor 22C, which are in downstream communication with line 20a, are closed in this mode. The first, first-stage oligomerization catalyst bed 22a upstream of the first reactor 22A has previously undergone regeneration in a regeneration mode. The first, first-stage oligomerization catalyst bed 22a upstream of the first reactor 22A may have previously oligomerized the input olefin stream in a lag mode to produce an upstream second oligomerized olefin stream before regeneration. The upstream first oligomerized olefin stream is discharged from the upstream first first-stage oligomerization catalyst bed 22a through an open valve on connecting line 124 to the upstream first oligomerization effluent line 24a and transported to line 12b and second charge air cooler 18b shown in Figure 1. The corresponding valves on connecting lines 125 and 126 from the second and third reactors 22B and 22C, which are in upstream communication with line 24a, are closed in this mode.

[0085] The second cooled, diluted olefin stream in line 20b in FIG. 1 is introduced into the downstream first-stage oligomerization catalyst bed 22b in lead mode through an open valve on connecting line 130 to oligomerize the input olefin stream on the downstream first-stage oligomerization catalyst bed to produce a downstream first oligomerized olefin stream. The corresponding valves on connecting line 131 to second reactor 22B and connecting line 132 to third reactor 22C, which are in downstream communication with line 20b, are closed in this mode. The first-stage oligomerization catalyst bed downstream of first reactor 22A previously underwent regeneration in regeneration mode. The first-stage oligomerization catalyst bed 22b downstream of first reactor 22A may have previously oligomerized the input olefin stream in lag mode to produce a downstream second oligomerized olefin stream before regeneration. A downstream first oligomerization olefin stream is discharged from the downstream first first-stage oligomerization catalyst bed 22b in downstream first oligomerization effluent line 24b through an open valve on connecting line 135 and transported to line 12c and third feed cooler 18c in Figure 1 for second reactor 22B. Corresponding valves on connecting lines 136 and 137 for second reactor 22B and third reactor 22C, respectively, in upstream communication with line 24b are closed when first reactor 22A is in reed mode.

[0086] In lag mode, line 20c in FIG. 1 first-stage inputs a third cooled diluted olefin stream through an open valve on connecting line 141 to second oligomerization catalyst bed 22c upstream of second reactor 22B, where the input olefin stream is oligomerized on the upstream second first-stage oligomerization catalyst bed to produce an upstream second oligomerized olefin stream. The corresponding valves on connecting line 140 to first reactor 22A and connecting line 142 to third reactor 22C, which are in downstream communication with line 20c, are closed in this mode. The second first-stage oligomerization catalyst bed 22c upstream of second reactor 22B previously underwent regeneration in regeneration mode. The second first-stage oligomerization catalyst bed 22c upstream of second reactor 22B may previously have oligomerized the input olefin stream in lead mode to produce an upstream second oligomerized olefin stream after regeneration. The upstream second oligomerized olefin stream is discharged from the upstream second first-stage oligomerization catalyst bed 22c through an open valve on connecting line 145 to the upstream second oligomerization effluent line 24c and transported to line 12d and fourth feed cooler 18d shown in Figure 1. The corresponding valves on connecting lines 144 and 146 from the second reactor 22B and third reactor 22C, respectively, in upstream communication with line 24a, are closed in this mode.

[0087] The fourth cooled, diluted olefin stream in line 20d in FIG. 1 is fed to the downstream second first-stage oligomerization catalyst bed 22d in lag mode through an open valve on connecting line 151 to oligomerize the input olefin stream on the downstream second first-stage oligomerization catalyst bed to produce a downstream second oligomerized olefin stream. The corresponding valves on connecting line 150 to first reactor 22A and connecting line 152 to third reactor 22C, which are in downstream communication with line 20d, are closed in this mode. The second first-stage oligomerization catalyst bed 22d downstream of second reactor 22B previously underwent regeneration in regeneration mode. The second first-stage oligomerization catalyst bed 22d downstream of second reactor 22B may previously have oligomerized the input olefin stream in lead mode to produce an upstream second oligomerized olefin stream after regeneration. A downstream second oligomerized olefin stream is discharged from the downstream second first-stage oligomerization catalyst bed 22d in downstream second oligomerization effluent line 24d through an open valve in connecting line 156 and transported to cooler 27 of Figure 1. Corresponding valves on connecting lines 155 and 157 for first reactor 22A and third reactor 22C, respectively, in upstream communication with line 24d, are closed when second reactor 22B is in reed mode.

[0088] After the upstream first first-stage oligomerization catalyst bed 22a and the downstream first first-stage oligomerization catalyst bed 22b in first reactor 22A are consumed in lead mode, the introduction of olefin flow to the respective beds may be discontinued and regeneration may be initiated. Alternatively, after the upstream second first-stage oligomerization catalyst bed 22c and the downstream second first-stage oligomerization catalyst bed 22d in second reactor 22B are consumed in lag mode, the introduction of olefin flow to the upstream first first-stage oligomerization catalyst bed 22a and the downstream first first-stage oligomerization catalyst bed 22b in first reactor 22A may be continued, albeit in lag mode, while second reactor 22B transitions to regeneration mode.

[0089] In FIG. 3, the third reactor is in regeneration mode. Line 100 inputs a regeneration gas stream through connection line 162 and an open valve thereon to the third first-stage oligomerization catalyst bed 22e upstream of the third first-stage reactor 22C, which is in regeneration mode. The corresponding valves on connection line 160 to the first first-stage reactor 22A in reed mode and the corresponding valves on connection line 161 to the second first-stage reactor 22B in lag mode, which communicates downstream with line 100, are closed. The regeneration gas may contain oxygen and may be at a high temperature. The upstream third first-stage oligomerization catalyst bed 22e was previously in reed mode, or alternatively, was immediately previously in lag mode. Regeneration gas from the upstream third first-stage oligomerization catalyst bed 22e can be supplied to the downstream third first-stage oligomerization catalyst bed 22f through an open valve on line 102c to regenerate the catalyst therein. The corresponding valves on lines 102a and 102b of the first first-stage reactor 22A and the second first-stage reactor 22B, which are in downstream communication with the upstream first-stage catalyst beds 22a and 22b, are closed. The regenerated flue gas exits the downstream third first-stage oligomerization catalyst bed 22f, enters connecting line 167 with the valve open, and is discharged to line 106. When the third reactor 22C is in regeneration mode, the corresponding valves on connecting line 165 for the first first-stage reactor 22A and connecting line 166 for the second first-stage reactor 22B, which are in upstream communication with line 106, are closed. After regeneration, the third reactor 22C can transition from regeneration reactor to lead reactor, the first reactor 22A transitions from lead reactor to lag reactor, and the second reactor 22B transitions from lag mode to regeneration mode.

[0090] FIG. 4 illustrates a regeneration process for the second-stage oligomerization reactor 32. The process may utilize three second-stage oligomerization reactors 32: a first reactor 32A, a second reactor 32B, and a third reactor 32C. The three reactors are switched between lead, lag, and regeneration modes. In FIG. 4, the first reactor 32A is in lead mode, the second reactor 32B is in lag mode, and the third reactor 32C is in regeneration mode. FIG. 4 is related to FIG. 1. In FIG. 4, the uncharged valves are open and the charged valves are closed. Additionally, capital letters in the reference letters are distinguished from lowercase letters.

[0091] 1 introduces the cooled oligomerized olefin stream through an open valve on connecting line 220 into the first second-stage oligomerization catalyst bed 32a of the first second-stage reactor 32A in lead mode, where the oligomerized olefin stream is oligomerized in the first second-stage oligomerization catalyst bed 32a to produce a first oligomerized stream. The corresponding valves on connecting line 221 to the second second-stage reactor 32B and connecting line 222 to the third reactor 32C, which are in downstream communication with line 28, are closed in this mode. The first second-stage oligomerization catalyst bed 32a upstream of the first reactor 32A previously underwent regeneration in regeneration mode. The first second-stage oligomerization catalyst bed 32a of the first reactor 32A may be oligomerizing the input olefin stream in lag mode to produce a second oligomerized stream prior to regeneration. The first oligomerization stream is discharged from the first second-stage oligomerization catalyst bed 32a through an open valve on connecting line 235 to a first oligomerization line 33 and transported to a second feed cooler 34 shown in Figure 1 by line 33. The corresponding valves on connecting lines 236 and 237 from the second and third reactors 32B and 32C, respectively, in upstream communication with line 33, are closed in this mode.

[0092] The first cooled oligomerization stream in line 35 from FIG. 1 is introduced into the second second-stage oligomerization catalyst bed 32b in the second second-stage oligomerization catalyst bed 32b in lag mode through an open valve on connecting line 241 to oligomerize the oligomerization stream on the second second-stage oligomerization catalyst bed and produce a second oligomerization stream. The corresponding valves on connecting line 240 to the first reactor 32A and connecting line 242 to the third reactor 32C, which are in downstream communication with line 35, are closed in this mode. The second second-stage oligomerization catalyst bed in the second second-stage reactor 32B has previously undergone regeneration in regeneration mode. The second second-stage oligomerization catalyst bed 32b in the second reactor 32A may have previously oligomerized the oligomerization stream in lead mode to produce the first oligomerization stream after regeneration. The second oligomerization stream is discharged from the second second-stage oligomerization catalyst bed 32b in the second second-stage reactor 32B through an open valve on connecting line 256, transported in second oligomerate line 37 to heat exchanger 29 of Figure 1, and finally fractionated in olefin splitter column 36. The corresponding valves on connecting lines 255 and 257 of the first and third second-stage reactors 32A and 32C, respectively, in upstream communication with line 37 are closed when the second reactor 32B is in lag mode.

[0093] After the first second-stage oligomerization catalyst bed 32a in the first second-stage reactor 32A is consumed in lead mode, the introduction of oligomerization stream to the first second-stage oligomerization reactor may be discontinued and regeneration may be initiated. Alternatively, after the second second-stage oligomerization catalyst bed 32b in the second second-stage reactor 32B, which is in lag mode, is consumed, the introduction of oligomerization stream to the first second-stage oligomerization catalyst bed 32a in the first second-stage reactor 32A may be continued while the second second-stage reactor 32B is moved to regeneration mode.

[0094] In FIG. 4, the third reactor 32C is in regeneration mode. Line 200 inputs a regeneration gas stream through connecting line 262 and the open valve thereon to the third second-stage oligomerization catalyst bed 32c of the third second-stage reactor 32C, which is in regeneration mode. The corresponding valves on connecting line 260 to the first second-stage reactor 32A in reed mode and on connecting line 261 to the second second-stage reactor 22B in lag mode, which communicates downstream with line 200, are closed. The regeneration gas may contain oxygen and may be hot. The third second-stage oligomerization catalyst bed 32c was previously in reed mode, or alternatively, was in lag mode immediately before regeneration mode. Regeneration flue gas exits the downstream third second-stage oligomerization catalyst bed 32c, enters connecting line 267 with the valve open, and is discharged to line 206. When the third reactor 32C is in regeneration mode, the corresponding valves on the connecting line 265 for the first second-stage reactor 32A and on the connecting line 266 for the second second-stage reactor 32B, which are in upstream communication with line 206, are closed. After regeneration, the third reactor 32C can be moved from a regeneration reactor to a lead reactor, while the first reactor 32A can be moved from a lead reactor to a lag reactor, and the second reactor 22B can be moved from a lag reactor to a regeneration mode.

[0095] To allow one regeneration system to regenerate each catalyst within a two-week period, a scheduling system was developed that accommodates the regeneration timing requirements and still allows some flexibility in scheduling with planned downtime, as shown in Figure 5. Regenerations can occur no more than twice per month per reactor, more preferably no more than once per month per reactor, or more preferably no more than once every five weeks per reactor. [Example]

[0096] Example 1 The spent first-stage oligomerization MTT zeolite catalyst and second-stage oligomerization amorphous silica-alumina supported nickel catalyst from the first pilot plant cycle test were regenerated in situ by contacting them with ethylene feed and light paraffin diluent in a stacked bed configuration. The regeneration procedure consisted of heating at 400°C for 600-800 hours. -1 The process consisted of a warm nitrogen purge at a gas hourly space velocity, coke combustion at 450 °C in a controlled O2 environment of 2 wt% and 7 wt% O2 in N2, and a compensatory coke combustion at 18 wt% O2 in N2. As shown in Table 1, the 400 °C nitrogen purge removed a significant amount of carbonaceous species. Based on gas chromatography analysis, the purged hydrocarbon species were C8–C20 olefins. While the carbon combustion step completely removed the coke on the second-stage Ni / ASA catalyst, the regenerated first-stage zeolite MTT catalyst contained 1 wt% recalcitrant coke. As experimentally demonstrated, the recalcitrant coke on the first-stage oligomerization catalyst did not adversely affect catalyst performance. The recalcitrant coke remained at the same level after successive regenerations in all subsequent cycles and never accumulated beyond 1 wt%.

[0097] [Table 1]

[0098] Example 2 Pilot plant testing using both a first stage oligomerization catalyst comprising MTT zeolite and a second stage oligomerization catalyst comprising nickel on amorphous silica-alumina confirmed that over two weeks of operation provided satisfactory conversion at acceptable temperatures in the first cycle, with full performance recovery in the second cycle after in situ regeneration.

[0099] Figure 6 shows the ethylene conversion over time for three cycles. The first cycle, shown as a dashed line, uses a fresh MTT zeolite catalyst and an amorphous silica-alumina-supported nickel catalyst arranged in a stacked-bed configuration in a pilot plant reactor. The second cycle, shown as a triangle, and the third cycle, shown as a circle, represent conversion over the regenerated catalyst. The regenerated cycle has a conversion comparable to that of the fresh catalyst before regeneration.

[0100] Figure 7 shows oligomer selectivity over time for three cycles. Again, the first cycle, shown as a dashed line, uses a fresh MTT zeolite catalyst and an amorphous silica-alumina-supported nickel catalyst arranged in a stacked-bed configuration in a pilot plant reactor. The second cycle, shown as a triangle, and the third cycle, shown as a circle, represent conversion over the regenerated catalyst. The regenerated cycle has selectivity comparable to that of the fresh catalyst before regeneration.

[0101] Specific Embodiments While the following will be described in conjunction with specific embodiments, it will be understood that this description is illustrative, but not intended to limit the scope of the preceding description and appended claims.

[0102] A first embodiment of the present disclosure is a process for oligomerizing an olefin stream, comprising: oligomerizing an input olefin stream over a first, first-stage oligomerization catalyst bed to produce a first oligomerized olefin stream; regenerating the first oligomerization catalyst bed; oligomerizing the input olefin stream over a second, first-stage oligomerization catalyst bed to produce a second oligomerized olefin stream; and oligomerizing the input olefin stream over the first, first-stage oligomerization catalyst bed to produce the first oligomerized olefin stream. An embodiment of the present disclosure is one, any, or all of the preceding through first embodiments of this paragraph, further comprising regenerating the second oligomerization catalyst bed. An embodiment of the present disclosure is one, any, or all of the preceding through first embodiments of this paragraph, further comprising regenerating the first, first-stage oligomerization catalyst bed by supplying oxygen gas to the catalyst bed at an elevated temperature. An embodiment of the present disclosure is one, any, or all of the preceding embodiments through the first embodiment of this paragraph, further comprising oligomerizing the input olefin stream over a third, first-stage oligomerization catalyst bed to produce an oligomerized olefin stream. An embodiment of the present disclosure is one, any, or all of the preceding embodiments through the first embodiment of this paragraph, further comprising discontinuing oligomerizing the input olefin stream over the first, first-stage oligomerization catalyst bed before regenerating the first, first-stage oligomerization catalyst bed. An embodiment of the present disclosure is one, any, or all of the preceding embodiments through the first embodiment of this paragraph, further comprising discontinuing oligomerizing the input olefin stream over the second, first-stage oligomerization catalyst bed before regenerating the second, first-stage oligomerization catalyst bed.An embodiment of the present disclosure is any one, any, or all of the preceding through first embodiments of this paragraph, further comprising: oligomerizing the oligomerized olefin stream over a first, second-stage oligomerization catalyst bed to produce a first oligomerization stream; regenerating the first, second-stage oligomerization catalyst bed; and oligomerizing the oligomerized olefin stream over a second, second-stage oligomerization catalyst bed to produce a second oligomerization stream. An embodiment of the present disclosure is any one, any, or all of the preceding through first embodiments of this paragraph, further comprising regenerating the second, second-stage oligomerization catalyst bed. An embodiment of the present disclosure is any one, any, or all of the preceding through first embodiments of this paragraph, further comprising regenerating the first, second-stage oligomerization catalyst bed by supplying oxygen gas to the catalyst bed at an elevated temperature. An embodiment of the present disclosure is any one, any, or all of the preceding through first embodiments of this paragraph, further comprising regenerating the first, second-stage oligomerization catalyst bed while oligomerizing the oligomerized olefin stream over the second, second-stage oligomerization catalyst bed. An embodiment of the present disclosure is any one, any, or all of the preceding through first embodiments of this paragraph, further comprising continuously oligomerizing the input olefin stream over the first-stage oligomerization catalyst for at least one month. An embodiment of the present disclosure is any one, any, or all of the preceding through first embodiments of this paragraph, further comprising continuously oligomerizing the oligomerized olefin stream over the second-stage oligomerization catalyst for at least two weeks.

[0103] A second embodiment of the present disclosure is a process for oligomerizing an olefin stream, comprising: oligomerizing an input olefin stream over a first, first-stage oligomerization catalyst bed to produce a first oligomerized olefin stream; oligomerizing the first oligomerized olefin stream over a first, second-stage oligomerization catalyst bed to produce a first oligomerized stream; regenerating the first, second-stage oligomerization catalyst bed; and oligomerizing the first oligomerized olefin stream over a second, second-stage oligomerization catalyst bed to produce a second oligomerized stream. An embodiment of the present disclosure is one, any, or all of the preceding embodiment of this paragraph through the second embodiment of this paragraph, further comprising regenerating the second, second-stage oligomerization catalyst bed. An embodiment of the present disclosure is any one, any, or all of the preceding through second embodiments of this paragraph, further comprising regenerating the first, second-stage oligomerization catalyst bed by supplying oxygen gas to the first, second-stage oligomerization catalyst bed at an elevated temperature. An embodiment of the present disclosure is any one, any, or all of the preceding through second embodiments of this paragraph, further comprising interrupting oligomerization of the oligomerized olefin stream over the first, second-stage oligomerization catalyst bed before regenerating the first, second-stage oligomerization catalyst bed. An embodiment of the present disclosure is any one, any, or all of the preceding through second embodiments of this paragraph, further comprising interrupting oligomerization of the oligomerized olefin stream over the second, second-stage oligomerization catalyst bed before regenerating the second, second-stage oligomerization catalyst bed. An embodiment of the present disclosure is one, any, or all of the preceding embodiment of this paragraph through the second embodiment of this paragraph, further comprising continuously oligomerizing the oligomerized olefin stream over a second-stage oligomerization catalyst for at least two weeks.

[0104] A third embodiment of the present disclosure is a process for oligomerizing an olefin stream, comprising: oligomerizing an input olefin stream over a first, first-stage oligomerization catalyst bed to produce a first oligomerized olefin stream; regenerating the first oligomerization catalyst bed; oligomerizing the input olefin stream over a second, first-stage oligomerization catalyst bed to produce a second oligomerized olefin stream; oligomerizing the first oligomerized olefin stream or the second oligomerized olefin stream over a first, second-stage oligomerization catalyst bed to produce a first oligomerized stream; regenerating the first, second-stage oligomerization catalyst bed; and oligomerizing the first oligomerized olefin stream or the second oligomerized olefin stream over a second, second-stage oligomerization catalyst bed to produce a second oligomerized stream. An embodiment of the present disclosure is one, any, or all of the preceding embodiment of this paragraph through the third embodiment of this paragraph, further comprising interrupting oligomerization of the input olefin stream over the first first-stage oligomerization catalyst bed before regenerating the first first-stage oligomerization catalyst bed.

[0105] Without further elaboration, it is believed that, using the preceding description, one skilled in the art can utilize the present disclosure to its fullest extent and easily ascertain the essential characteristics of the present disclosure, and can make various changes and modifications to the present disclosure to adapt it to various uses and conditions, without departing from the spirit and scope of the present disclosure. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way, and are intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

[0106] Above, all temperatures are set forth in degrees Celsius and all parts and percentages are by weight unless otherwise indicated.

Claims

1. 1. A process for oligomerizing an olefin stream, comprising: oligomerizing an input olefin stream over a first first-stage oligomerization catalyst bed to produce a first oligomerized olefin stream; regenerating the first first-stage oligomerization catalyst bed; oligomerizing the input olefin stream over a second first-stage oligomerization catalyst bed to produce a second oligomerized olefin stream; and oligomerizing said input olefin stream over said first stage oligomerization catalyst bed to produce said first oligomerized olefin stream.

2. 10. The process of claim 1 further comprising regenerating the second first-stage oligomerization catalyst bed.

3. 10. The process of claim 1, further comprising regenerating said first first-stage oligomerization catalyst bed by supplying oxygen gas to said first first-stage oligomerization catalyst bed at an elevated temperature.

4. 10. The process of claim 1, further comprising oligomerizing the input olefin stream over a third first-stage oligomerization catalyst bed to produce an oligomerized olefin stream.

5. 10. The process of claim 1, further comprising discontinuing oligomerization of the input olefin stream over the first first-stage oligomerization catalyst bed prior to regenerating the first first-stage oligomerization catalyst bed.

6. 10. The process of claim 1, further comprising discontinuing oligomerization of the input olefin stream over the second, first-stage oligomerization catalyst bed prior to regenerating the second, first-stage oligomerization catalyst bed.

7. 10. The process of claim 1, further comprising regenerating the first first-stage oligomerization catalyst bed by supplying an inert gas, hydrocarbon, or solvent to the catalyst bed at an elevated temperature.

8. 8. The process of claim 7, further comprising supplying oxygen gas at an elevated temperature to the catalyst bed.

9. oligomerizing the oligomerized olefin stream over a first second-stage oligomerization catalyst bed to produce a first oligomerized stream; regenerating the first second-stage oligomerization catalyst bed; 10. The process of claim 1, further comprising oligomerizing the oligomerized olefin stream over a second second-stage oligomerization catalyst bed to produce a second oligomerized stream.

10. 10. The process of claim 9 further comprising regenerating the second second-stage oligomerization catalyst bed.

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