Process for converting olefins to distillate fuels with oligomerate recycle.

Abstract

A process for dimerizing and oligomerizing olefins to distillate fuels utilizing a solid acid catalyst for ethylene oligomerization in a first stage and a metal catalyst for further oligomerization in a second stage. Distillate fuels can be produced from this process. The oligomerized olefins can be recycled to the first stage oligomerization reaction to ensure sufficient oligomerization of the smaller olefins.

Description

[Technical Field]

[0001] (Statement of priority) This application claims priority to Indian Provisional Patent Application No. 202211049524 filed on August 30, 2022, Indian Provisional Patent Application No. 202211049522 filed on August 30, 2022, and Indian Provisional Patent Application No. 202211049525 filed on August 30, 2022, which are incorporated herein in their entireties.

[0002] FIELD OF THE INVENTION 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 oligomerized into olefins, such as C4, C6, and C8 olefins. Olefin oligomerization is a process by which smaller olefins can be oligomerized into larger olefins. More specifically, olefins, including oligomerized olefins, can be converted into 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 substituted in electric motor systems, as fueling an aircraft requires a high energy density that batteries cannot provide. Significant tax incentives are currently available for green jet fuel in certain regions.

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

[0007] The present inventors have devised a process for oligomerizing olefins to produce distillate fuels that utilizes a zeolite catalyst for ethylene in the first stage oligomerization and a metal catalyst for the oligomeric olefins in the second stage oligomerization.

[0008] The present inventors have also devised a process for oligomerizing olefins into distillate fuels in which the oligomerized olefins are recycled downstream to the first stage oligomerization catalyst bed. [Brief explanation of the drawings]

[0009] [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. 2 is a schematic diagram of an alternative embodiment of the oligomerization section of the process and apparatus of FIG. 1. [Figure 4] 1 is a plot of ethylene conversion over time. [Figure 5] 1 is a plot of product selectivity over time. DETAILED DESCRIPTION OF THE INVENTION

[0010] definition The term "communication" means that fluid flow is operably permitted between the listed components, which may be characterized as "fluid communication."

[0011] 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.

[0012] 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.

[0013] The term "direct communication" means that fluid flow from an upstream component enters a downstream component without passing through any other intervening vessel.

[0014] The term "indirect communication" means that fluid flow from an upstream component enters a downstream component after passing through an intervening vessel.

[0015] The term "bypass" means that an object is out of downstream communication with a bypass subject, at least to the extent that it bypasses.

[0016] As used herein, the term "predominant" or "predominantly" means more than 50%, suitably more than 75%, and preferably more than 90%.

[0017] 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 the column to the 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.

[0018] 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."

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] Detailed Description The disclosed process involves oligomerizing an olefin stream containing ethylene in a first oligomerization stage, followed by further oligomerization of the ethylene oligomers in a second oligomerization stage. The process utilizes a zeolite catalyst for the first stage oligomerization of ethylene and a metal catalyst for the second stage oligomerization.

[0026] The process and apparatus may include oligomerization section 10 of FIG. 1 and hydrogenation section 110 of FIG.

[0027] 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 one embodiment, the input olefin stream can comprise at least 95 mole % ethylene. The input olefin stream in line 12 is sometimes referred to as an ethylene stream. The olefin stream can be provided by the dehydration of ethanol or can be provided from an MTO unit. The input olefin stream can be at a temperature of 60° C. (140° F.) to 150° C. (302° F.), preferably 80° C. (176° F.) to 100° C. (212° F.), and at a pressure of 3.5 MPa (500 psig) to 8.4 MPa (1200 psig).

[0028] An olefin stream may first be contacted with a first-stage oligomerization catalyst to oligomerize ethylene into dimers and oligomers, and then with a second-stage oligomerization catalyst to oligomerize the oligomerized ethylene. The dimerization reaction 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.

[0029] 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, flow through the control valve in input line 12d may not be permitted, and the input olefin stream is fed only to the upstream catalyst beds 22a-22c. 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 where the flow rate of the input olefin stream from line 12 predominates, such as 40-60% in line 12a, a stream where the flow rate of the input olefin stream from line 12 is less predominate, such as 15-40% in lines 12b and 12c, and no stream in line 12d. Preferably, the flow rate of the input olefin stream fed to upstream bed 22a is the highest of the upstream catalyst beds 22a-22c.

[0030] 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, after splitting into multiple olefin streams, the diluent stream is added to the first olefin stream in line 12a to provide a first diluted olefin stream in line 16a, so that the diluent stream passes through all of the first-stage oligomerization reactions. Alternatively, the diluent stream can also be split into multiple parallel 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 in line 12. The first diluted olefin stream can contain 35 wt.% or less olefins, suitably 17 wt.% or less olefins, and preferably 6 wt.% or less olefins. The first dilute olefin stream may comprise up to 35 wt% ethylene, suitably up to 14 wt% ethylene, preferably up to 6 wt% ethylene.The first dilute olefin stream may comprise up to 35 wt% propylene, suitably up to 14 wt% propylene, preferably up to 6 wt% propylene.

[0031] The first dilute olefin stream in line 16a may be cooled in a first input 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 a first-stage oligomerization reactor 22. The cooled, diluted first input olefin stream in line 20a may be charged at a temperature of from 180°C (356°F) to 260°C (500°F) and a pressure of from 3.5 MPag (500 psig) to 8.4 MPag (1200 psig). The input cooler 18a may be equipped with a steam generator. The first-stage oligomerization reactor 22 may comprise a series of first-stage oligomerization catalyst beds 22a, 22b, 22c, and 22d, each for charging a plurality of olefin streams 12a, 12b, 12c, and 12d, respectively. As previously mentioned, in one embodiment, there may be no input olefin stream in line 12d; therefore, in this embodiment, the input olefin stream from line 12 is fed only to the upstream first-stage oligomerization catalyst beds 22a-22c. The first-stage oligomerization reactor preferably contains four fixed first-stage oligomerization catalyst beds 22a, 22b, 22c, and 22d. It is also contemplated that each first-stage 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. A parallel first stage oligomerization reactor may be used when first stage oligomerization reactor 22 is deactivated while first stage oligomerization reactor 22 is regenerated in situ by burning coke from the catalyst.

[0032] A recycled olefin stream in line 26 may be input to first-stage oligomerization catalyst beds 22a-22d. In one embodiment, the recycled olefin stream is fed only to downstream 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 to first-stage oligomerization catalyst beds 22c and 22d, respectively. In one embodiment, line 26c may have a predominant flow rate of the recycled olefin stream, and 26d may have the remainder of the flow rate of the recycled olefin stream in line 26. Preferably, a majority of the flow rate of the recycled olefin stream is fed to bed 22c upstream of downstream catalyst beds 22c and 22d. In one embodiment, first-stage catalyst bed 22c is the upstream bed for the input olefin from line 12 and the downstream bed for the recycled olefin feed from line 26.

[0033] The first cooled, diluted olefin stream may be charged to first catalyst bed 22a in line 20a, preferably in downflow operation; however, upflow operation may be preferred. As first-stage oligomerization of ethylene occurs in first first-stage oligomerization catalyst bed 22a, an exotherm is generated due to the exothermic nature of the ethylene first-stage oligomerization reaction. The first-stage oligomerization of the first olefin stream produces a first oligomerized olefin stream in first oligomerization effluent line 24a at an elevated outlet temperature, despite cooling and dilution. The elevated outlet temperature is limited to 25°C (45°F) to 61°C (110°F) above the inlet temperature to catalyst bed 22a.

[0034] The second olefin stream in line 12b may be diluted with a first oligomerized olefin stream in line 24a removed from the first first-stage oligomerization catalyst bed 22a to provide a second diluted olefin stream in line 16b. The first oligomerized olefin stream in line 24a comprises the diluent stream from diluent line 14 added to the first olefin stream in line 12a. The second diluted olefin stream may comprise 35 wt% or less olefins, suitably 22 wt% or less olefins, and preferably 15 wt% or less olefins. The second diluted olefin stream may comprise 35 wt% or less ethylene, suitably 15 wt% or less ethylene, and preferably 6 wt% or less ethylene. The second diluted olefin stream may comprise 35 wt% or less propylene, suitably 15 wt% or less propylene, and preferably 6 wt% or less propylene. The second dilute olefin stream in line 16b is cooled in a second input cooler 18b, which may be located external to the first-stage oligomerization reactor 22, to provide a second cooled dilute olefin stream in line 20b that may be input to a second bed 22b of first-stage oligomerization catalyst in the first-stage oligomerization reactor 22. The second input cooler 18b may be a steam generator. The second cooled dilute olefin stream in line 20b may be input 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). The second dilute olefin stream comprises diluent and olefins from the first oligomerization olefin stream. The olefins from the first oligomerization olefin stream are further oligomerized in the second catalyst bed 22b. First-stage oligomerization of ethylene in the second olefin stream in second bed 22b of first-stage oligomerization catalyst produces a second oligomerized olefin stream in second oligomerization effluent line 24b at an elevated outlet temperature, which may be limited to 25°C (45°F) to 61°C (110°F) above the inlet temperature to second first-stage catalyst bed 22b.

[0035] The third olefin stream in line 12c may be diluted with the second oligomerized olefin stream in line 24b removed from the first-stage oligomerization reactor 22 and combined with the first recycled olefin stream in line 26c to provide a third diluted olefin stream in line 16c. The second 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 may comprise 35 wt% or less olefins, suitably 23 wt% or less olefins, and preferably 15 wt% or less olefins. The third diluted olefin stream may comprise 35 wt% or less ethylene, suitably 13 wt% or less ethylene, and preferably 6 wt% or less ethylene. The third diluted olefin stream may comprise 35 wt% or less propylene, suitably 13 wt% or less propylene, and preferably 6 wt% or less propylene. The third dilute olefin stream in line 16c is cooled in a third input 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 input to a third bed 22c of first-stage oligomerization catalyst in the first-stage oligomerization reactor 22. The third input cooler 18c may be a steam generator. The third cooled dilute olefin stream in line 20c may be input at a temperature of from 180°C (356°F) to 260°C (500°F) and a pressure of from 3.5 MPag (500 psig) to 8.4 MPag (1200 psig). The third dilute olefin stream comprises diluent and olefins from the second oligomerization olefin stream and the first recycled olefin stream. Olefins from the second oligomerized olefin stream and the first recycled olefin stream are further oligomerized in third, first-stage oligomerization catalyst bed 22c. Oligomerization of ethylene in the third dilute olefin stream in third bed 22c of first-stage oligomerization catalyst produces a third oligomerized olefin stream in third oligomerization effluent line 24c at an elevated outlet temperature. In one embodiment, the third oligomerized olefin stream is the penultimate oligomerized olefin stream, and third 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.

[0036] The fourth olefin stream in line 12d may be diluted with the third or penultimate oligomerized olefin stream in line 24c removed from the third first-stage oligomerization catalyst bed 22c of the first-stage oligomerization reactor 22 and the second recycled olefin stream in line 26d to provide a fourth diluted olefin stream in line 16d. The third 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 diluted olefin stream may comprise 35 wt% or less olefins, suitably 24 wt% or less olefins, and preferably 15 wt% or less olefins. The fourth diluted olefin stream may comprise 35 wt% or less ethylene, suitably 11 wt% or less ethylene, and preferably 6 wt% or less ethylene. The fourth diluted olefin stream may comprise 35 wt% or less propylene, suitably 11 wt% or less propylene, and preferably 6 wt% or less propylene. The fourth dilute olefin stream in line 16d may be cooled in a fourth input 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 input to a fourth bed 22d of first-stage oligomerization catalyst in the first-stage oligomerization reactor 22. The fourth input cooler 18d may be a steam generator. The fourth cooled dilute olefin stream in line 20d may be input at a temperature of from 180°C (356°F) to 260°C (500°F) and a pressure of from 3.5 MPag (500 psig) to 8.4 MPag (1200 psig). The fourth or final dilute olefin stream comprises diluent and olefins from the third or penultimate oligomerization olefin stream and the second recycled olefin stream. Olefins from the third or penultimate oligomerized olefin stream and the second recycled olefin stream are further oligomerized in fourth catalyst bed 22d. Oligomerization of ethylene and oligomers in the fourth dilute olefin stream in fourth first stage bed 22d of first stage oligomerization catalyst produces a fourth oligomerized olefin stream in fourth oligomerization effluent line 24d at an elevated outlet temperature.The elevated outlet temperature is limited to 25°C (45°F) to 61°C (110°F) above the inlet temperature to the fourth first stage catalyst bed 22d.

[0037] Recycle olefin streams 26c and 26d provide olefins that can be dimerized over catalyst beds 22c and 22d, respectively, but also help manage the exotherm generated during the oligomerization of ethylene and olefins.

[0038] In one embodiment, the fourth olefin stream in line 12d is the final olefin stream, the fourth oligomerized olefin stream is the final oligomerized olefin stream, and the fourth oligomerization effluent line 24d is the final oligomerization effluent line 24d.

[0039] The first stage oligomerization reaction is carried out for 0.5 to 10 hours based on the olefin. -1 The process is conducted primarily in the liquid phase or mixed gas-liquid phase at an LHSV of 1000 MPa. The inventors have found that a majority of the ethylene in the olefin stream is converted to higher olefins. Typically, at least 30-50 mole percent of the ethylene dimerizes across the first-stage oligomerization catalyst bed. Ethylene initially dimerizes over the catalyst to butenes.

[0040] 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.

[0041] 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 create 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.

[0042] One of the components of the catalyst binder utilized in the present invention 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.

[0043] A suitable first-stage oligomerization catalyst is prepared by mixing proportional volumes of zeolite and alumina to achieve the desired zeolite to alumina ratio. In one embodiment, the MTT content can 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.

[0044] 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.

[0045] 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 between 260°C (500°F) and 815°C (1500°F). The MTT catalyst is not selective to neutralize acidic sites such as amines.

[0046] 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).

[0047] 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.

[0048] The first-stage oligomerization catalyst can be regenerated upon deactivation. Suitable regeneration conditions include, for example, subjecting the first-stage oligomerization catalyst 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 most of the coke is burned off and less than 1.2 wt% coke remains on the catalyst. To facilitate regeneration without downtime, a swinging bed system can be used in conjunction with an alternative first-stage oligomerization reactor. Alternatively, a lead-lag swinging bed system can be used. 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 increased or decreased oxygen concentration. The activity and selectivity of the regenerated catalyst are comparable to that of fresh catalyst.

[0049] 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.

[0050] 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 an oligomerate 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. Oligomerization reactor 32 may comprise a series of oligomerization catalyst beds 32a and 32b assembled in series. It is also contemplated that each second-stage oligomerization catalyst bed 32a and 32b may be in a dedicated oligomerization reactor, or multiple oligomerization catalyst beds may be in two or more separate oligomerization reactors. Two second-stage oligomerization catalyst beds are readily contemplated. A parallel second stage oligomerization reactor can be used where the second stage oligomerization reactor 32 is deactivated while the second stage oligomerization reactor 32 is regenerated in situ by burning off coke from the catalyst.

[0051] 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 may be operated at a pressure of 4.9 MPa (700 psig) to 7.6 MPa (1100 psig), more preferably 3.4 MPa (500 psig) to 8.3 MPa (1200 psig). A first oligomerate stream from first second-stage oligomerization catalyst bed 32a may be removed from second-stage oligomerization reactor 32 in line 33a, 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.

[0052] 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 in the second-stage input line 28 is contacted with a second-stage oligomerization catalyst to dimerize, trimerize, and tetramerize unconverted ethylene. For the second-stage oligomerization reactor 32, process conditions may be selected to produce a higher proportion of jet-range olefins, which, when hydrogenated in a subsequent step as described below, result in desired jet-range hydrocarbon products. The predominant unconverted ethylene in the input oligomerized olefin stream is oligomerized. In one embodiment, at least 99 mole percent of the butenes in the input oligomerized olefin stream are oligomerized. The metal oligomerization catalyst is efficient at dimerizing and oligomerizing the non-oligomerized ethylene from the first stage oligomerization. An oligomerate 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.

[0053] The second-stage oligomerization catalyst may comprise a metal catalyst, preferably a metal on a support. The second-stage oligomerization catalyst is preferably an amorphous silica-alumina base with a metal from either Group VIII and / or Group VIB of the Periodic Table, using Chemical Abstracts Service notation. In one embodiment, the catalyst comprises a Group VIII metal promoted with a Group VIB metal. Typically, 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 may 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 may 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. In addition, suitable catalysts have a nitrogen BET assay of 50 to 400 m 2 / g of surface area.

[0054] 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.

[0055] 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 may be utilized in accordance with the present invention. A preferred surfactant is 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.

[0056] 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 one embodiment, 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 some embodiments, other ratios of amorphous silica-alumina to alumina may be suitable.

[0057] 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.

[0058] 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.

[0059] 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).

[0060] 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).

[0061] 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 greater than 100 angstroms in diameter 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.

[0062] To prepare the second-stage 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 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] The 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 first-stage oligomerization catalyst beds 22a-22d. The diluent stream is then transported in line 28 to second-stage oligomerization reactor 32 to absorb the exotherm in the second-stage oligomerization reactor.

[0067] 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 oligomerate stream in line 37 contains multiple olefin products that are distillate range hydrocarbons.

[0068] The oligomerate stream in line 37, having an increased C9+ olefin concentration compared to the input oligomerized olefin stream in line 28, is heat exchanged with the final oligomerized olefin stream in line 24d in heat exchanger 29 and the olefin splitter bottoms stream in line 41 in heat exchanger 43 to reduce its pressure and is fed to olefin splitter column 36. The oligomerate stream in line 37 can be at a temperature of from 140°C (284°F) to 200°C (392°F) and a pressure of from 3.4 MPa (gauge) (500 psig) to 8.3 MPa (gauge) (1200 psig), and preferably from 3.9 MPa (gauge) (550 psig) to 6.3 MPa (gauge) (900 psig).

[0069] 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 may 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 420 kPa (gauge) (60 psig). It is envisioned that olefin splitter column 36 may be two columns.

[0070] The olefin splitter overhead stream may be cooled to 66°C (150°F) to 93°C (200°F), with the resulting condensate portion returned to the olefin splitter column 36 via olefin splitter receiver 42 as reflux. The net vapor stream in receiver overhead line 44 from the 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 overhead line 38 can be fully condensed, perhaps by cooling in an external refrigeration loop, to provide a liquid light oligomer stream in line 48. The light oligomer stream in line 48 can be split into a light olefin drag stream in line 50 and an oligomer recycle stream in line 26, which can be recycled to the second-stage oligomerization reactor 32, but preferably to the first-stage oligomerization reactor 22. The light olefins drag stream in line 50 may comprise 1 to 15 weight percent of the light oligomers stream in line 48. The light oligomers stream in line 48 may comprise 30 to 80 weight percent light olefins.

[0071] In one embodiment, the oligomer recycle stream in line 26 may be combined with the final oligomerized olefin stream in final oligomerization effluent line 24d to provide an input oligomerization stream in line 28 for input to second-stage oligomerization reactor 32. It is also contemplated that the oligomer recycle stream in line 26 may be combined with the first diluent olefin stream in line 16a or split into first through fourth diluent olefin streams in lines 16a-16d for dimerizing or oligomerizing unreacted ethylene.

[0072] The heavy olefins stream in splitter bottoms line 40 may be split between a reboil stream 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 41 is cooled by heat exchange with an oligomerized olefins stream in line 37 and then 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 of Figure 2 that is returned to the jet fractionator in line 85 of Figure 2.

[0073] 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). Additionally, 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. The combined olefin stream in line 54 may also 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, may be used to ensure full saturation.

[0074] 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.

[0075] 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.

[0076] 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 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 fractionator 70. In one embodiment, a high temperature and low temperature separator system may be used in place of a single hydrotreating separator 62.

[0077] The saturated heavy liquid stream in bottoms line 66 may be fed to jet fractionator 70 without prior stripping in a stripper column. Alternatively, a stripper column may be utilized upstream of jet fractionator 70. In jet fractionator 70, the saturated heavy liquid stream may be separated into an off-gas stream in overhead line 80, a green jet stream in net liquid overhead line 74, and a green diesel stream in bottoms line 76. Jet fractionator 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).

[0078] The jet fractionation overhead stream in overhead line 72 may be cooled, and a resulting condensate portion is produced from the bottom of receiver 78 in line 79. 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 and / or olefin splitter column 36.

[0079] 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.

[0080] The green diesel bottoms stream in bottoms line 76 can be split into a reboil stream that is reboiled back to jet fractionator 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 the heat release of the first stage in oligomerization reactor 22. The green diesel stream in diluent line 14 is paraffinic and therefore inert to the oligomerization and hydrogenation reactions to which it may be subjected. 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 streams meet 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, heated to boiling in a heater, and returned to the jet fractionator.

[0081] Figure 3 shows one embodiment of oligomerization section 10 in which recycled olefins are introduced into upstream first-stage oligomerization catalyst beds 22a and 22b. Elements in Figure 3 having the same configuration as Figure 1 will have the same reference numbers as Figure 1. Elements in Figure 3 having a different configuration from the corresponding elements in Figure 1 will have the same reference numbers but will be indicated with a prime ('). The configuration and operation of the embodiment of Figure 3 is essentially the same as Figure 1, with noted exceptions.

[0082] The recycled olefin stream in line 26 may be fed to first-stage oligomerization catalyst beds 22a-22d. In one embodiment, the recycled olefin stream is divided into multiple recycled olefin streams: a first recycled olefin stream in line 26a, a second recycled olefin stream in line 26b, a third recycled olefin stream in line 26c, and a fourth recycled olefin stream in line 26d. The flow rates of each recycled olefin stream may be equal or may be stepped, with a greater bias toward the upstream beds 26a-26d or a greater bias toward the downstream beds 26d-26a. The recycled olefin stream in line 26 may be divided into multiple recycled olefin streams in lines 26a-26d, each of which is fed to a respective first-stage oligomerization catalyst bed 22a-22d.

[0083] In one embodiment, a first input olefin stream in line 12a, a diluent stream in line 14, and a first recycled olefin stream in line 26a are combined to provide a first diluted olefin stream in line 16a', which is cooled in first input cooler 18a to provide a first cooled diluted olefin stream in line 20a and charged to first first stage catalyst bed 22a. The ethylene and recycled olefins are oligomerized over first first stage oligomerization catalyst bed 22a to produce a first oligomerized olefin stream in line 24a, which is removed from first first stage oligomerization catalyst bed 22a.

[0084] The second input olefin stream in line 12b' may be mixed with a second recycled olefin stream in line 26b and diluted with a first oligomerized olefin stream in line 24a removed from the first first-stage oligomerization catalyst bed 22a to provide a second diluted olefin stream in line 16b'. The first oligomerized olefin stream in line 24a comprises the diluent stream from diluent line 14 added to the first olefin stream in line 12a. The second diluted olefin stream in line 16b' may be cooled in a second input cooler 18b, which may be located external to the first stage oligomerization reactor 22, to provide a second cooled diluted olefin stream in line 20b for input to the second bed 22b of the first stage oligomerization catalyst in the first stage oligomerization reactor 22. The second dilute olefin stream comprises diluent and olefins from the first oligomerized olefin stream, the second input olefin stream, and the second recycled olefin stream. The olefins from the first oligomerized olefin stream, the second input olefin stream, and the second recycled olefin stream are further oligomerized in second catalyst bed 22b. First-stage oligomerization of ethylene and olefins in the first oligomerized olefin stream, the second input olefin stream, and the second recycled olefin stream in second bed 22b of first-stage oligomerization catalyst produces a second oligomerized olefin stream in second oligomerization effluent line 24b at an elevated outlet temperature.

[0085] The third input olefin stream in line 12c' may be mixed with a third recycled olefin stream in line 26c and diluted with a second oligomerized olefin stream in line 24b removed from the second first-stage oligomerization catalyst bed 22b to provide a third diluted olefin stream in line 16c'. The first oligomerized olefin stream in line 24a comprises the diluent stream from diluent line 14 added to the first olefin stream in line 12a. The third diluted olefin stream in line 16b' may be cooled in a third input cooler 18c, which may be located external to the first-stage oligomerization reactor 22, to provide a third cooled diluted olefin stream in line 20c and charged to the third bed 22c of first-stage oligomerization catalyst in the first-stage oligomerization reactor 22. The third dilute olefin stream comprises diluent and olefins from the second oligomerized olefin stream, the third input olefin stream, and the third recycled olefin stream. The olefins from the second oligomerized olefin stream, the third input olefin stream, and the third recycled olefin stream are further oligomerized in third catalyst bed 22c. First-stage oligomerization of ethylene and olefins in the second oligomerized olefin stream, the third input olefin stream, and the third recycled olefin stream in third bed 22c of first-stage oligomerization catalyst produces a third oligomerized olefin stream in third oligomerization effluent line 24c at an elevated outlet temperature.

[0086] The fourth input olefin stream in line 12d' may be mixed with a fourth recycled olefin stream in line 26d and diluted with a third oligomerized olefin stream in line 24c removed from the third first-stage oligomerization catalyst bed 22c to provide a fourth dilute olefin stream in line 16d'. The first oligomerized olefin stream in line 24a comprises the diluent stream from diluent line 14 added to the first olefin stream in line 12a. The fourth dilute olefin stream in line 16d' may be cooled in a fourth input 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 and charged to the fourth bed 22d of first-stage oligomerization catalyst in the first-stage oligomerization reactor 22. The fourth dilute olefin stream comprises diluent and olefins from the third oligomerized olefin stream, the fourth input olefin stream, and the fourth recycled olefin stream. The olefins from the third oligomerized olefin stream, the fourth input olefin stream, and the fourth recycled olefin stream further oligomerize in fourth catalyst bed 22c. First-stage oligomerization of ethylene and olefins in the fourth input olefin stream, the third oligomerized olefin stream, and the fourth recycled olefin stream in fourth bed 22c of first-stage oligomerization catalyst produces a fourth oligomerized olefin stream in fourth oligomerization effluent line 24d at an elevated outlet temperature.

[0087] In one embodiment illustrated in FIG. 3, the splitter overhead stream in splitter overhead line 38′ from olefin splitter column 36′ may be cooled to full condensation, possibly in an external cooling loop, and fed to olefin splitter receiver 42′. The vent stream in line 44′ from receiver 42′ may be equipped with a condenser chiller 45 to ensure full condensation. The condensate from olefin splitter receiver 42′ may provide reflux to the column and a light oligomers stream in line 48′. The light oligomers stream in line 48′ may be split into a light olefins drag stream in line 50 and an oligomers recycle stream in line 26 that may be recycled to second-stage oligomerization reactor 32, but preferably to first-stage oligomerization reactor 22. The light olefins drag stream in line 50 may comprise 1 to 15 wt. % of the light oligomers stream in line 48′. The light oligomer stream in line 48 may comprise 30 to 80 weight percent light olefins.

[0088] Other than these, the embodiment of FIG. 3 operates and is configured similarly to the embodiment of FIG.

[0089] 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%. [Example]

[0090] A first-stage oligomerization catalyst comprising MTT zeolite and a second-stage oligomerization catalyst comprising nickel on an amorphous silica-alumina catalyst were loaded into a pilot plant reactor in a stacked-bed configuration. The reactor was fed with ethylene and a light paraffin diluent and operated in a recycle mode to fully utilize the light olefins. Tests were conducted at a pressure of 6.2 MPa (gauge) (900 psig), with the inlet temperature to the first oligomerization stage catalyst varying from 210 to 250°C and the inlet temperature to the second oligomerization stage catalyst varying from 130 to 170°C, and with a WHSV of the fresh ethylene charge varying from 0.5 to 1.0 hours. -1Depending on the test conditions, the results show ethylene conversions of over 90 wt % as shown in Figure 4 and high jet range selectivities as shown in Figure 5.

[0091] 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.

[0092] A first embodiment of the present disclosure is a process for oligomerizing an olefin stream, comprising: oligomerizing the olefin stream with a first stage oligomerization catalyst comprising a solid acid catalyst to produce an oligomerized olefin stream; and oligomerizing the oligomerized olefin stream with a second stage oligomerization catalyst comprising a metal to provide an oligomerate stream. An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section through the first embodiment of this section, wherein the first stage oligomerization catalyst is a zeolite catalyst. An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section through the first embodiment of this section, wherein the zeolite is an acid catalyst. An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section through the first embodiment of this section, wherein the zeolite is an MTT catalyst. An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section through the first embodiment of this section, wherein the second stage oligomerization catalyst is a metal catalyst. An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section through the first embodiment of this section, wherein the metal catalyst is a nickel catalyst. An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section through the first embodiment of this section, wherein the oligomerization with the first stage oligomerization catalyst occurs in multiple catalyst beds. An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section through the first embodiment of this section, further comprising splitting the olefin stream into multiple input olefin streams and charging each of the multiple input olefin streams to one of the multiple catalyst beds. An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section through the first embodiment of this section, further comprising mixing a diluent stream with the olefin stream. An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section through the first embodiment of this section, further comprising mixing the diluent stream with the plurality of input olefin streams.

[0093] A second embodiment of the present disclosure is a process for oligomerizing an olefin stream, the process comprising: oligomerizing an input olefin stream and a recycle olefin stream with a first stage oligomerization catalyst to produce a first oligomerized olefin stream; oligomerizing the first oligomerized olefin stream with the first stage oligomerization catalyst to produce a second oligomerized olefin stream; oligomerizing the second oligomerized olefin stream with a second stage oligomerization catalyst to provide an oligomerate stream; and removing a recycle olefin stream from the oligomerate stream. An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section up to the second embodiment of this section, further comprising oligomerizing the first oligomerized olefin stream and the recycle olefin stream with a first stage oligomerization catalyst to produce the second oligomerized olefin stream.

[0094] A third embodiment of the present disclosure is a process for oligomerizing an olefin stream, comprising: oligomerizing an input olefin stream with a first stage oligomerization catalyst to produce a first oligomerized olefin stream; oligomerizing the first oligomerized olefin stream and a recycle olefin stream with the first stage oligomerization catalyst to produce a second oligomerized olefin stream; oligomerizing the second oligomerized olefin stream with a second stage oligomerization catalyst to provide an oligomerate stream; and removing a recycle olefin stream from the oligomerate stream. An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section through the third embodiment of this section, further comprising: splitting the input olefin stream into the first input olefin stream and a second input olefin stream; and oligomerizing the second input olefin stream with the first oligomerized olefin stream and the recycle olefin stream. An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section through the third embodiment of this section, further comprising: diluting the first input olefin stream with a diluent stream prior to oligomerizing the first input olefin stream. An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section through the third embodiment of this section, further comprising: splitting the input olefin stream into a plurality of input olefin streams, including a first input olefin stream and a second input olefin stream, and introducing a first input olefin stream of the plurality of input olefin streams into an upstream first-stage oligomerization reactor. An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section through the third embodiment of this section, further comprising: splitting the recycled olefin stream into a plurality of recycled olefin streams, including a first recycled olefin stream and a second recycled olefin stream, and introducing a first recycled olefin stream of the plurality of recycled olefin streams into a downstream first-stage oligomerization reactor.An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section through the third embodiment of this section, further comprising: charging a first input olefin stream of the plurality of input olefin streams to a first first stage oligomerization reactor and a second input olefin stream of the plurality of input olefin streams to a second first stage oligomerization reactor. An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section through the third embodiment of this section, further comprising: charging a first recycled olefin stream of the plurality of recycled olefin streams to a third first stage oligomerization reactor and a second recycled olefin stream of the plurality of recycled olefin streams to a fourth first stage oligomerization reactor. An embodiment of the present disclosure is one, any, or all of the preceding embodiments of this section through the third embodiment of this section, wherein removing a recycled olefin stream from the oligomerate stream comprises fractionating the oligomerate stream to provide an overhead stream comprising the recycled olefin stream. 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.

[0095] 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 the olefin stream with a first stage oligomerization catalyst comprising a solid acid catalyst to produce an oligomerized olefin stream; oligomerizing said oligomerized olefin stream with a second stage oligomerization catalyst comprising a metal to provide an oligomerate stream.

2. 10. The process of claim 1, wherein the first-stage oligomerization catalyst is a zeolite catalyst.

3. 3. The process of claim 2 wherein the zeolite is an acid catalyst.

4. 4. The process of claim 3, wherein the zeolite catalyst is an MTT catalyst.

5. 10. The process of claim 1, wherein the second-stage oligomerization catalyst is a metal catalyst.

6. 1. A process for oligomerizing an olefin stream, comprising: oligomerizing the input olefin stream and the recycle olefin stream over a first stage oligomerization catalyst to produce a first oligomerized olefin stream; oligomerizing the first oligomerized olefin stream with a first stage oligomerization catalyst to produce a second oligomerized olefin stream; oligomerizing the second oligomerized olefin stream with a second stage oligomerization catalyst to provide an oligomerate stream; removing said recycled olefin stream from said oligomerate stream.

7. 7. The process of claim 6, further comprising oligomerizing the first oligomerized olefin stream and the recycle olefin stream over the first stage oligomerization catalyst to produce the second oligomerized olefin stream.

8. 1. A process for oligomerizing an olefin stream, comprising: oligomerizing an input olefin stream with a first stage oligomerization catalyst to produce a first oligomerized olefin stream; oligomerizing the first oligomerized olefin stream and the recycle olefin stream with a first stage oligomerization catalyst to produce a second oligomerized olefin stream; oligomerizing the second oligomerized olefin stream with a second stage oligomerization catalyst to provide an oligomerate stream; removing said recycled olefin stream from said oligomerate stream.

9. 9. The process of claim 8, further comprising: dividing an input olefin stream into a first input olefin stream and a second input olefin stream; and oligomerizing said second input olefin stream with said first oligomerized olefin stream and said recycled olefin stream.

10. 9. The process of claim 8, wherein removing the recycled olefin stream from the oligomerate stream comprises fractionating the oligomerate stream to provide an overhead stream comprising the recycled olefin stream.

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