Process for converting olefins into distillate fuels

Abstract

A process for dimerizing and oligomerizing olefins to produce a distillate fuel, the process managing the heat of dimerization by diluting with a paraffin that is inert in the dimerization. The olefin stream can be split and fed to a plurality of dimerization reactors to further reduce the heat generated. The ethylene feed may be cooled before entering the dimerization reactor. The paraffin can be obtained from the saturated oligomerization effluent.

Description

Technical Field

[0001] (Priority Claim) This application claims priority to U.S. Patent Application No. 17 / 872,714, filed Jul. 25, 2022, which is hereby incorporated by reference in its entirety.

[0002] (Field of the Invention) This field is the conversion of olefins to distillates. This field can relate in particular to the dimerization of olefins and the oligomerization of the dimerized olefins to distillate fuels.

Background Art

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

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

[0005] Jet fuel is one of the few petroleum fuels and cannot be easily replaced by an electric motor system because high energy output is required for fueling airplanes and an electric motor cannot provide it. In certain regions, significant incentives are currently available for green jet fuel.

[0006] An efficient process for converting ethylene to distillate fuel is desired.

Summary of the Invention

[0007] The inventors have devised a process for dimerizing and oligomerizing olefins into a distillate fuel, which manages the exotherm of ethylene dimerization by diluting with a paraffin stream that is inert in the dimerization. The olefin stream can be split and fed to a plurality of dimerization reactors to further reduce the heat generated. The ethylene feed may be cooled before entering the dimerization reactor. The paraffin stream can be obtained from the saturated oligomerization effluent.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

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

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

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

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

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

[0014] The term "bypass" means that the object is removed from downstream communication with the bypass target to at least the extent of bypassing.

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

[0016] The term "column" means a distillation column (singular or plural) for separating one or more components of different volatilities. Unless otherwise indicated, each column includes a condenser at the top of the column to condense and reflux a portion of the overhead stream returning to the top of the column, and a reboiler at the bottom of the column to vaporize a portion of the bottoms stream and return it to the bottom of the column. The feed to the column can 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 bottoms outlet temperature. The overhead line and bottoms line refer to the net line from the column downstream of any reflux or reboiling to the column. A stripper column omits the reboiler at the bottom of the column and instead can provide the required heat and the driving force for separation from a fluidized inert medium such as steam. A stripping column typically feeds the raw material to the top tray and withdraws 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 the boot. A flash drum is a type of separator that can be in downstream communication with a separator that can operate 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 using the equation provided in Appendix A7 of ASTM D1160 entitled "Practice for Converting Observed Vapor Temperatures to Atmospheric Equivalent Temperatures".

[0018] As used herein, the term "True Boiling Point" (TBP) means a test method for determining the boiling point of a substance, which test method is capable of obtaining analytical data and producing liquefied gas, distillation fractions, and residual oil of standardized quality, and for determining the yields of the above fractions by both mass and volume, where a graph of temperature versus mass percent distilled is generated using 15 theoretical plates in a column with a reflux ratio of 5:1, corresponding to ASTM D-2892.

[0019] As used herein, the terms "T5", "T90", or "T95" mean the temperatures at which 5 mass percent, 90 mass percent, or in some cases 95 mass percent of a sample boils, respectively, using ASTM D-86 or TBP.

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

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

[0022] As used herein, the term "diesel" means hydrocarbons that boil within the 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" means diesel containing hydrocarbons not of fossil fuel origin.

[0023] As used herein, the term "jet fuel" means hydrocarbons that boil in the range of T10 of 190°C (374°F) to 215°C (419°F) and an end point of 290°C (554°F) to 310°C (590°F). The term "green jet fuel" means a jet fuel that includes hydrocarbons not of fossil fuel origin.

DETAILED DESCRIPTION OF THE INVENTION

[0024] The disclosed process includes dimerizing an olefin stream containing ethylene, followed by further oligomerizing the ethylene dimer and ethylene oligomers. The resulting oligomers can be separated to provide a distillate stream, which can be saturated to provide a distillate fuel. The saturated stream can be recycled to the ethylene dimerization as a diluent for absorbing heat of reaction. Further, the olefin stream can be split and charged to several dimerization catalyst beds to manage the heat of reaction in a similar manner. Since the dimerization product of the catalyst bed that may contain unreacted olefins is also sent to the downstream bed, the overall conversion per pass is increased. Further, the dimerization product of the upstream catalyst bed functions as an additional diluent for absorbing the heat of reaction in the downstream catalyst bed.

[0025] This process and apparatus can include the oligomerization section 10 of FIG. 1 and the hydrogenation section 110 of FIG. 2.

[0026] Referring to the oligomerization section 10 of FIG. 1, the charged olefin stream in line 12 is supplied to the oligomerization section 10. The charged olefin stream can contain substantial ethylene. The charged olefin stream can mainly contain ethylene. In an embodiment, the charged olefin stream can contain at least 95 mol% ethylene. The charged olefin stream in line 12 may sometimes be referred to as an ethylene stream. The olefin stream may be provided by dehydration of ethanol or may be provided from an MTO unit. The charged olefin stream may be at a temperature of 60 °C (140 °F) to 150 °C (302 °F), preferably 80 °C (176 °F) to 100 °C (212 °C) and a pressure of 5.6 MPag (800 psig) to 8.4 MPag (1200 psig).

[0027] First, the olefin stream can be contacted with a dimerization catalyst to dimerize ethylene into dimers, and then contacted with an oligomerization catalyst to oligomerize the dimerized ethylene. The dimerization reaction produces a large amount of heat. For example, by dimerization of ethylene, 612 kcal / kg (1100 BTU / lb) of heat can be generated. As a result, this large amount of heat must be managed.

[0028] Thus, the olefin stream within line 12 may be split into a plurality of olefin streams. In FIG. 1, the olefin stream is split into four separate streams, namely, a first olefin stream within charge line 12a, a second olefin stream within charge line 12b, a third olefin stream within charge line 12c, and a fourth or last olefin stream within charge line 12d. More or fewer separate olefin streams may also be used. Up to six olefin streams are readily contemplated. The charged olefin stream within line 12 can be split into a plurality of olefin streams of equal split amounts. Alternatively, the charged olefin stream within line 12 may be split into unequal flows. For example, the charged olefin stream may be split into flows of increasing flow rate where subsequent olefin streams have a greater flow rate than the preceding stream. In an embodiment, the charged olefin stream is split into four flows of equal flow rate each containing 25 volume % of the charged olefin stream.

[0029] To manage heat generation, an olefin stream can be diluted with a diluent stream to provide a diluted olefin stream for absorbing heat generation. The diluent stream can include a paraffin stream within diluent line 14. The diluent stream in diluent line 14 may be added to the feed olefin stream in line 12 before splitting the feed olefin stream into a plurality of olefin streams. Preferably, the diluent stream is added to the first olefin stream in line 12a after being split into a plurality of olefin streams to provide a first diluted olefin stream in line 16a, so that the diluent stream passes through all of the dimerization reactions. Alternatively, the diluent stream can be split into a plurality of streams and each diluent stream can be added to the corresponding olefin stream. The diluent stream can have a volumetric flow rate that is 2 to 8 times, preferably 3 to 6 times, the volumetric flow rate of the feed olefin stream. The first diluted olefin stream can include 25 wt% or less olefin, suitably 10 wt% or less olefin, preferably 6 wt% or less olefin. The first diluted olefin stream can include 25 wt% or less ethylene, suitably 10 wt% or less ethylene, preferably 6 wt% or less ethylene. The first diluted olefin stream in line 16a can be cooled in a first feed cooler 18a to provide a first cooled diluted olefin stream in line 20a and charged to a first bed 22a of a dimerization catalyst within dimerization reactor 22. The first cooled diluted olefin stream in line 20a may be charged at a temperature of 54 °C (130 °F) to 165 °C (329 °F) and a pressure of 5.6 MPag (800 psig) to 8.4 MPag (1200 psig).

[0030] The dimerization reactor 22 can include a series of dimerization catalyst beds 22a, 22b, 22c, and 22d for charging each of the plurality of olefin streams 12a, 12b, 12c, and 12d, respectively. The dimerization reactor preferably contains four fixed dimerization catalyst beds 22a, 22b, 22c, and 22d. Each dimerization catalyst bed 22a, 22b, 22c, and 22d may be within a dedicated dimerization reactor, or it is also contemplated that a plurality of dimerization catalyst beds may be within two or more separate dimerization reactors. Up to six dimerization catalyst beds are readily contemplated. The parallel dimerization reactor can be used when the dimerization reactor 22 is deactivated and during which the dimerization reactor 22 is regenerated in situ by combustion of coke from the catalyst.

[0031] The first cooled diluted olefin stream can preferably be charged to the first catalyst bed 22a in line 20a in a downward flow operation. However, an upward flow operation may be suitable in some cases. When dimerization of ethylene occurs in the first catalyst bed 22a, heat is generated due to the exothermic nature of the ethylene dimerization reaction. When the first olefin stream is dimerized, a first dimerized olefin stream is produced in the first dimerization effluent line 24a at an elevated outlet temperature despite cooling and dilution. The elevated outlet temperature is limited to a temperature 50 °C (90 °F) to 61 °C (110 °F) higher than the inlet temperature to the catalyst bed 22a.

[0032] The second olefin stream within line 12b can be diluted with the first dimerized olefin stream within line 24a withdrawn from the dimerization reactor 22 to provide a second diluted olefin stream within line 16b. The first dimerized olefin stream within line 24a includes a diluent stream from diluent line 14 added to the first olefin stream within line 12a. The second diluted olefin stream can include ethylene at 25 wt% or less, suitably at 10 wt% or less, preferably at 6 wt% or less. The second diluted olefin stream within line 16b can be cooled in a second charge cooler 18b that can be located external to the dimerization reactor 22 to provide a second cooled diluted olefin stream within line 20b, which can be charged to a second bed 22b of the dimerization catalyst within the dimerization reactor 22. The second cooled diluted olefin stream within line 20b can be charged at a temperature of 54 °C (130 °F) to 165 °C (329 °F) and a pressure of 5.6 MPag (800 psig) to 8.4 MPag (1200 psig). The second diluted olefin stream includes a diluent and an olefin from the first dimerized olefin stream. The olefin from the first dimerized olefin stream dimerizes in the second catalyst bed 22b. When ethylene in the second olefin stream in the second bed 22b of the dimerization catalyst is dimerized, a second dimerized olefin stream is produced within the second dimerization effluent line 24b at an elevated outlet temperature. The elevated outlet temperature can be limited to a temperature 50 °C (90 °F) to 61 °C (110 °F) higher than the inlet temperature to the catalyst bed 22b.

[0033] The third olefin stream within line 12c can be diluted with the second dimerized olefin stream within line 24b withdrawn from the dimerization reactor 22 to provide a third diluted olefin stream within line 16c. The second dimerized olefin stream within line 24b includes a diluent stream from diluent line 14 added to the first olefin stream within line 12a. The third diluted olefin stream can contain ethylene at 25 wt% or less, preferably 10 wt% or less, and more preferably 6 wt% or less. The third diluted olefin stream within line 16c can be cooled within a third charge cooler 18c that can be located external to the dimerization reactor 22 to provide a third cooled diluted olefin stream within line 20c and charged to a third bed 22c of the dimerization catalyst within the dimerization reactor 22. The third cooled diluted olefin stream within line 20c can be charged at a temperature of 54 °C (130 °F) to 165 °C (329 °F) and a pressure of 5.6 MPag (800 psig) to 8.4 MPag (1200 psig). The third diluted olefin stream includes a diluent and an olefin from the second dimerized olefin stream. The olefin from the second dimerized olefin stream dimerizes in the third catalyst bed 22c. When the ethylene in the third olefin stream within the third bed 22c of the dimerization catalyst is dimerized, a third dimerized olefin stream is generated in the third dimerized effluent line 24c at an elevated outlet temperature. In an embodiment, the third dimerized olefin stream is the second-to-last dimerized olefin stream and the third dimerized effluent line 24c is the second-to-last dimerized effluent line 24c. The elevated outlet temperature is limited to a temperature 50 °C (90 °F) to 61 °C (110 °F) higher than the inlet temperature to the catalyst bed 22c.

[0034] The fourth olefin stream within line 12d can be diluted with the third or second-to-last dimerized olefin stream within line 24c withdrawn from the dimerization reactor 22 to provide a fourth diluted olefin stream within line 16d. The third or second-to-last dimerized olefin stream within line 24c includes a diluent stream from diluent line 14 added to the first olefin stream within line 12a. The fourth diluted olefin stream can contain ethylene at 25 wt% or less, preferably at 10 wt% or less, and more preferably at 6 wt% or less. The fourth diluted olefin stream within line 16d can be cooled within a fourth charge cooler 18d that can be located external to the dimerization reactor 22 to provide a fourth cooled diluted olefin stream within line 20d, which can be charged to a fourth bed 22d of the dimerization catalyst within the dimerization reactor 22. The fourth cooled diluted olefin stream within line 20d can be charged at a temperature of 54 °C (130 °F) to 165 °C (329 °F) and a pressure of 5.6 MPag (800 psig) to 8.4 MPag (1200 psig). The fourth or last diluted olefin stream includes a diluent and an olefin from the third or second-to-last dimerized olefin stream. The olefin from the third or second-to-last dimerized olefin stream dimerizes in the fourth catalyst bed 22b. When the ethylene in the fourth olefin stream within the fourth bed 22d of the dimerization catalyst is dimerized, a fourth dimerized olefin stream is produced in the fourth dimerization effluent line 24d at an elevated outlet temperature. The elevated outlet temperature is limited to a temperature 50 °C (90 °F) to 61 °C (110 °F) higher than the inlet temperature to the catalyst bed 22d.

[0035] In an embodiment, the fourth olefin stream is the last olefin stream, the fourth dimerized olefin stream is the last dimerized olefin stream, and the fourth dimerization effluent line 24d is the last dimerization effluent line 24d.

[0036] The dimerization reaction is 0.5 to 10 hr on an olefin basis -1In the LHSV, it is mainly carried out in the liquid phase or the gas-liquid mixed phase. The inventors have found that most of the ethylene in the olefin stream is converted to higher olefins. Typically, at least 90-95 mol% of the ethylene dimerizes throughout the dimerization catalyst bed. Ethylene first dimerizes on the catalyst to form butene.

[0037] The dimerization catalyst is preferably an amorphous silica-alumina base having a metal from either Group VIII and / or Group VIB of the periodic table using the Chemical Abstracts Service notation. In one embodiment, the catalyst has a Group VIII metal promoted with a Group VIB metal. Typically, since silica and alumina are only present in the base, the ratio of silica to alumina is the same for both the catalyst and the base. The metal can be impregnated on the silica-alumina base or ion-exchanged with 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, preferably exceeding 0.25, as measured by Ammonia Temperature Programmed Desorption (ammonia TPD) described below. In addition, a suitable catalyst has a surface area of 50-400 m 2 / g as determined by the nitrogen BET method.

[0038] The preferred dimerization catalyst is described below. The preferred dimerization catalyst comprises an amorphous silica-alumina support. One of the components of the catalyst support utilized in the present invention is alumina. Alumina can be any of various hydrated aluminum oxides or alumina gels such as alpha-alumina monohydrate of boehmite structure or pseudo-boehmite structure, alpha-alumina trihydrate of gibbsite structure, beta-alumina trihydrate of bayleyite structure. Particularly preferred alumina is available under the trademark Catapal from Sasol North America Alumina Product Group. This material is an extremely high-purity alpha-alumina monohydrate (pseudo-boehmite) and has been shown to result in high-purity gamma-alumina after firing at high temperature. Another component of the catalyst support is amorphous silica-alumina. A suitable silica-alumina with a silica to alumina ratio of 2.6 is available, for example, from CCIC, a subsidiary of JGC of Japan.

[0039] Another component utilized in the preparation of the catalyst utilized in the present invention is a surfactant. The surfactant is preferably mixed with the above-mentioned alumina and silica-alumina powders. The resulting mixture of surfactant, alumina, and silica-alumina is then formed, dried, and fired as described below. Firing effectively removes the organic components of the surfactant by combustion, but only after the surfactant has faithfully performed its function according to the present invention. Any suitable surfactant can be utilized according to the present invention. The preferred surfactant is a surfactant selected from a series of commercially available surfactants sold under the trademark "Antarox" by Solvay S.A. The "Antarox" surfactant is generally characterized as a modified linear aliphatic polyether and is a low-foaming biodegradable detergent and wetting agent.

[0040] A suitable silica-alumina mixture is prepared by mixing proportional volumes of silica-alumina and alumina to achieve the desired ratio of silica to alumina. In embodiments, 75-95 wt% amorphous silica-alumina having a silica to alumina ratio of 2.6 and 10-20 wt% alumina powder provide a suitable carrier. In embodiments, other ratios of amorphous silica-alumina to alumina may be suitable.

[0041] 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 alumina and silica-alumina. A preferred method is to mix an aqueous solution of the surfactant with the blend of alumina and silica-alumina prior to the final formation of the carrier. The surfactant is preferably present in the paste or dough in an amount of 0.01-10 wt% based on the weight of alumina and silica-alumina.

[0042] 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 wetting to form a dough having sufficient viscosity to be extruded or spray dried.

[0043] The paste or dough can 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, and then divide the extruded material into extrudates of the desired length and dry them. A further firing step can be used to provide additional strength to the extrudates. Generally, firing is carried out in a stream of dry air at a temperature of 260 °C (500 °F) to 815 °C (1500 °F).

[0044] The extruded particles can have any suitable cross-sectional shape, i.e., symmetric or asymmetric, but in most cases, they have a symmetric cross-sectional shape, preferably spherical, cylindrical, or lobed. The cross-sectional diameter of the particles can be as small as about 40 μm. However, usually it is from 0.635 mm (0.25 inch) to 12.7 mm (0.5 inch), preferably from 0.79 mm (1 / 32 inch) to 6.35 mm (0.25 inch), and most preferably from 0.06 mm (1 / 24 inch) to 4.23 mm (1 / 6 inch).

[0045] Typical properties of the amorphous silica-alumina carrier utilized herein are a total pore volume, an 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 carrier measured by the conventional mercury porosimeter method is usually from 0.2 to 2.0 cc / gram, preferably from 0.25 to 1.0 cc / gram, and most preferably from 0.3 to 0.9 cc / gram. Usually, the amount of the pore volume of the carrier in pores with a diameter larger 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. The surface area measured by the B.E.T. method is typically more than 50 m 2 / gram, for example, more than 200 m 2 / gram, preferably at least 250 m 2 / gram, and most preferably from 300 m 2 / gram to 400 m 2 / gram.

[0046] To prepare the catalyst, the support material is formulated with one or more precursors of at least one metal component from Group VIII or Group VIB of the Periodic Table by single or multiple impregnations of the calcined amorphous refractory oxide support particles. The Group VIII metal, preferably nickel, must be present at a concentration of 0.5 to 15 wt%, and the Group VIB metal, preferably tungsten, must be present at a concentration of 0 to 12 wt%. The impregnation can be achieved by any method known in the art, for example, by spray impregnation in which a solution containing the metal precursor in dissolved form is sprayed onto the support particles. Another method is the 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 the support in a large volume of the impregnation solution or circulating the support therein, and still another method is the pore volume or pore saturation technique in which the support particles are introduced into an impregnation solution of a volume just sufficient to fill the pores of the support. Optionally, 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 just sufficient to fill the pores.

[0047] When the active metal precursors are incorporated by impregnation, the metals are converted to their respective oxide forms, for example, by subsequent or second calcination at a high temperature of 399 °C (750 °F) to 760 °C (1400 °F). Optionally, calcination may be carried out after each impregnation of the individual active metals. The subsequent calcination yields a catalyst containing the active metals in their respective oxide forms.

[0048] A preferred dimerization catalyst of the present invention comprises an amorphous silica-alumina substrate impregnated with 0.5 to 15 wt% nickel in the form of 3.175 mm (0.125 inch) extrudates and has a density of 0.45 to 0.65 g / mL. It is also contemplated that the metals can be incorporated onto the support by other methods such as ion exchange and co-mulling.

[0049] The dimerization catalyst can be regenerated upon deactivation. Suitable regeneration conditions include subjecting the catalyst, for example in-situ, to hot air at 500 °C for 3 hours. To promote regeneration without downtime, a swing bed arrangement may be used along with an alternative dimerization reactor. The regeneration gas may include air with an increased or decreased oxygen concentration. The activity and selectivity of the regenerated catalyst are comparable to those of fresh catalyst.

[0050] The final dimerization olefin stream in the final dimerization effluent line 24d with an increased concentration of ethylene dimers and oligomers compared to the charged olefin stream in line 12 is mixed with the oligomer recycle stream in line 26 to provide a charged oligomerized stream in line 28. The charged oligomerized stream is heated by exchanging heat with the net olefin splitter bottoms stream in line 30 and charged to the oligomerization reactor 32 at a temperature of 204 °C (400 °F) to 265 °C (509 °F) and a pressure of 5.6 MPa (800 psig) to 8.4 MPa (1200 psig).

[0051] The oligomerization reactor 32 may be in downstream communication with the dimerization reactor 22. The oligomerization reactor 32 preferably operates in a downflow mode. However, an upflow mode may be suitable in some cases. The charged oligomerized stream is contacted with an oligomerization catalyst to dimerize and trimerize C2 - C8 olefins to provide olefins in the distillate range. Most of the butenes in the charged oligomerized stream are oligomerized. In an embodiment, at least 99 mol% of the butenes in the charged oligomerized stream are oligomerized. An oligomerized stream having an average carbon number increased more than that of the charged oligomerized olefin stream in line 28 exits the oligomerization reactor 32 in line 34.

[0052] The oligomerization catalyst may include a zeolite catalyst. The zeolite may constitute 5 to 95% by weight, for example 5 to 85% by weight, of the catalyst. Suitable zeolites include those 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. The three-letter code indicating the zeotype is as defined by the Structure Commission of the International Zeolite Association and is managed 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 oligomerization catalyst may include a zeolite having a framework with a 10-membered ring pore structure. Examples of suitable zeolites having a 10-membered ring pore structure include TON, MTT, MFI, MEL, AFO, AEL, EUO, and FER. In a more preferred embodiment, the oligomerization catalyst including a zeolite having a 10-membered ring pore structure may include a one-dimensional pore structure. The 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 through the zeolite crystal. A suitable example of a zeolite having a 10-membered ring one-dimensional pore structure may include MTT. In a further embodiment, the oligomerization catalyst includes MTT zeolite.

[0053] The oligomerization catalyst can be formed by combining zeolite with a binder and then shaping 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 wt% of the treated catalyst. The binder is used to impart hardness and strength to the catalyst. Examples of 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 clay.

[0054] One of the components of the catalyst binder utilized in the present invention is alumina. The alumina source can be any of various hydrated aluminums or alumina gels such as alpha-alumina monohydrate with a boehmite structure or a pseudo-boehmite structure, alpha-alumina trihydrate with a gibbsite structure, beta-alumina trihydrate with a bayerite structure. Suitable alumina is available under the trademark VERSAL from UOP LLC. Preferred alumina is available under the trademark Catapal from Sasol North America Alumina Product Group. This material is an extremely high-purity alpha-alumina monohydrate (pseudo-boehmite) and has been shown to result in high-purity gamma-alumina after firing at high temperatures.

[0055] Suitable oligomerization catalysts are prepared by mixing proportional volumes of zeolite and alumina to achieve the desired ratio of zeolite to alumina. In embodiments, the MTT content can be 5 to 85, such as 20 to 82 wt% MTT zeolite, and the remaining alumina powder preferably provides a suitably supported catalyst. Silica carriers are also contemplated.

[0056] A monobasic acid such as nitric acid or formic acid can be added to the mixture in an aqueous solution to peptize the alumina in the binder. Additional water can be added to the mixture to provide sufficient wetting to form a dough having sufficient viscosity to be extruded or spray dried. An extrusion aid such as cellulose ether powder can also be added. A preferred extrusion aid is available from The Dow Chemical Company under the Methocel trademark.

[0057] The paste or dough can be prepared in the form of shaped particles. The preferred method is to extrude the dough through a die having openings of the desired size and shape, and then divide the extruded material into extrudates of the desired length and dry them. A further firing step can be used to provide additional strength to the extrudates. Generally, firing is carried out in an air stream at a temperature of 260 °C (500 °F) to 815 °C (1500 °F). The MTT catalyst has no selectivity to neutralize acidic sites such as amines.

[0058] The extruded particles can have any suitable cross-sectional shape, i.e., symmetric or asymmetric, but in most cases, they have a symmetric cross-sectional shape, preferably spherical, cylindrical, or multi-lobed. The cross-sectional diameter of the particles can be as small as about 40 μm. However, it is usually 0.635 mm (0.25 inch) to 12.7 mm (0.5 inch), preferably 0.79 mm (1 / 32 inch) to 6.35 mm (0.25 inch), and most preferably 0.06 mm (1 / 24 inch) to 4.23 mm (1 / 6 inch).

[0059] Regarding the oligomerization reactor 32, process conditions are selected such that a higher percentage of jet-range olefins are produced, and the jet-range olefins, when hydrogenated in subsequent steps as described below, result in hydrocarbon products in the desired jet range. In an exemplary embodiment, an MTT-type zeolite catalyst disposed in a ratio of 90 / 10 to 20 / 80, preferably 20 / 80 to 50 / 50, on a high-purity pseudo-boehmite alumina substrate is provided in the catalyst bed or more within the oligomerization reactor 32. The feed oligomerization stream in line 28 is heated and charged to the oligomerization reactor 32. To achieve the most desirable olefin products, the oligomerization reactor 32 operates at a temperature of 204 °C (400 °F) to 260 °C (500 °F). The oligomerization reactor 70 is operated at a pressure of 2.1 MPa (300 psig) to 7.6 MPa (1100 psig), more preferably 4.9 MPa (710 psig) to 6.9 MPa (1000 psig).

[0060] The oligomerization reaction is also essentially exothermic. The final dimerized olefin stream in line 24d is added to the first olefin stream in line 12a and carried through the dimerization catalyst beds 22a - 22d, including a diluent stream from the diluent line 14. The diluent stream is then transported to the oligomerization reactor 32 in line 28 to absorb the heat generated within the oligomerization reactor.

[0061] When the oligomerization reaction is carried out according to the above process conditions, a C4 olefin conversion rate of 95% or more or 97% or more is achieved. The resulting oligomerized olefin stream in line 34 contains a plurality of olefin products that are hydrocarbons in the distillate range.

[0062] The oligomerization catalyst can be regenerated upon deactivation. Suitable regeneration conditions include subjecting the oligomerization catalyst, for example in-situ, to hot air at 500 °C for 3 hours. To facilitate regeneration without downtime, a swing bed arrangement may be used with an alternative oligomerization reactor. The regeneration gas stream can be fed into the oligomerization reactor 32 that requires regeneration. The regeneration gas can include air with an increased or decreased oxygen concentration. The activity and selectivity of the regenerated catalyst are comparable to those of fresh catalyst.

[0063] The oligomerized olefin stream in line 34 having an increased C9+ olefin concentration compared to the charged oligomerized olefin stream in line 28 is heat exchanged with the olefin splitter bottoms stream in line 30, the pressure is reduced, and it is fed to the olefin splitter 36.

[0064] In olefin splitter tower 36, oligomers that boil at a temperature lower than hydrocarbons in the jet range, typically C8 - hydrocarbons having an atmospheric boiling point of less than 150°C, are separated from the bottoms stream in bottoms line 40, which contains C9+ hydrocarbons in the distillate range, typically C9 - C22 olefins, to the olefin splitter overhead stream in overhead line 38. The olefin splitter tower 36 can operate at a bottoms temperature of 400°C (750°F) - 427°C (800°F) and an overhead pressure of 172 kPa (25 psig) - 517 kPa (75 psig). It is assumed that the olefin splitter tower 36 may be two towers. The olefin splitter overhead stream may be cooled, and a portion of the resulting condensate is refluxed from olefin splitter receiver 42 back to olefin splitter tower 36. The net vapor stream in receiver overhead line 44 from olefin splitter receiver 42 is compressed to oligomerization pressure in off - gas compressor 46 and can provide a light oligomer stream in line 48 in either the gas phase or the liquid phase after cooling. Alternatively, the olefin splitter overhead stream in overhead line 38 can be completely 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 that is recycled to oligomerization reactor 32. The light olefin drag stream in line 50 can constitute 3 - 15 wt% of the light oligomer stream in line 48. The light oligomer stream in line 48 can consist of 50 - 80 wt% light olefins. The oligomer recycle stream in line 26 is mixed with the final dimerization olefin stream in final dimerization effluent line 24d to provide a charged oligomerization stream in line 28 for charging to oligomerization reactor 32. It is also assumed that the oligomer recycle stream in line 26 is mixed with the first diluent olefin stream in line 16a or split into the first - fourth diluent olefin streams in lines 16a - 16d to dimerize unreacted ethylene.

[0065] The heavy olefin stream within the splitter bottom line 40 can be split between a reboil stream that is reboiled and returned to the olefin splitter column 36 and the heavy olefin stream within the net splitter bottom line 30. The heavy olefin stream within the net bottom line 30 is cooled by heat exchanging with the oligomerized olefin stream within line 34 and then the charged oligomerized stream within line 28, and then transported to the hydrogenation section 110 of FIG. 2.

[0066] Turning to the hydrogenation section 110 of FIG. 2, the heavy olefin stream within the net olefin splitter bottom line 30 from FIG. 1 containing the overhead-range C9+ oligomerized olefins can be hydrogenated within the hydrogenation reactor 52 to saturate the olefin bonds to provide fuel. This step is carried out to ensure that the product motor fuel meets or exceeds the thermal oxidation requirements specified in ASTM D7566-10a for hydrogenated synthesized paraffinic kerosene (SPK). Further, saturating the oligomerized heavy olefins results in a paraffin stream that can be used as a diluent stream within line 14. The heavy olefin stream within line 30 can be cooled to generate vapor and combined with the light olefin drag stream containing C2 - C8 olefins within line 50 from FIG. 1 to generate a combined olefin stream within line 54. Also, the combined olefin stream within line 54 can be combined with the hydrogen stream within line 56 to provide a combined hydrogenation feed stream within line 58 that is cooled and charged to the hydrogenation reactor 52 at 125 °C (257 °F) to 204 °C (400 °F) and 3.5 MPa (500 psig) to 6.9 MPa (1000 psig). Excess hydrogen such as 1.5 - 2.5 stoichiometric hydrogen can be used to ensure complete saturation.

[0067] Hydrogenation is typically carried out using conventional hydrogenation or hydrotreating catalysts, including, for example, metal catalysts containing palladium, rhodium, nickel, ruthenium, platinum, rhenium, cobalt, molybdenum, or combinations thereof, and supported metal catalysts thereof. The catalyst support can be any solid inert substance, including, but not limited to, oxides such as silica, alumina, titania, calcium carbonate, barium sulfate, and carbon. The catalyst support can be in the form of powder, granules, pellets, etc.

[0068] In an exemplary embodiment, hydrogenation is carried out in a hydrogenation reactor 52 containing an alumina-supported platinum catalyst, for example, an alumina-supported platinum catalyst containing 0.5 wt% to 0.9 wt%. The hydrogenation reactor 52 converts olefins to paraffin products having the same carbon number distribution as the olefins, thereby forming paraffins in a distillate range suitable for use as jet and diesel fuels.

[0069] The saturated heavy stream discharged from the hydrogenation reactor 52 in line 60 can be cooled by heat exchange with the saturated heavy liquid stream in the separator bottom line 66 and supplied to the hydrogenation separator 62. In the hydrogenation separator 62, the saturated heavy stream is separated into a hydrogenation separator vapor stream in the top line 64 and a saturated heavy liquid stream in the hydrogenation separator bottom line 66. The purge in line 65 can be withdrawn from the hydrogenation separator vapor stream in line 64, and the remainder can be compressed and combined with the make-up hydrogen in line 68 to provide a hydrogen stream in line 56. The saturated heavy liquid stream in the bottom line 66 can be heated by heat exchange with the saturated heavy stream in line 60 and the diluent stream in line 14 and supplied to the jet fractionator 70.

[0070] The saturated heavy liquid stream in the bottom line 66 can be supplied to the jet fractionator 70 without undergoing prior stripping in the stripper column. Alternatively, the stripper column may be utilized upstream of the jet fractionator 70. In the jet fractionator 70, the saturated heavy liquid stream can be separated into an off-gas stream in the top line 72, a green jet stream in the side line 74 from the side of the jet fractionator 70, and a green diesel stream in the bottom line 76. The jet fractionator 70 can operate at a bottom temperature of 427 °C (800 °F) to 482 °C (900 °F) and a top pressure of 35 kPa (5 psig) to 350 kPa (50 psig).

[0071] The jet fractionator top stream in the top line 72 may be cooled, and the resulting condensate portion is refluxed from the jet fractionator receiver 78 back to the jet fractionator 70 in line 79. Meanwhile, the net off-gas stream containing C8-hydrocarbons is taken out from the jet fractionator receiver 78 to the receiver top line 80. Most of the hydrocarbons in the net off-gas stream in the receiver top line 80 are lighter hydrocarbons and can be used to fuel a reboiler for the jet fractionator 70 and / or the olefin splitter column 36.

[0072] The green jet stream taken out in the side line 74 contains C9 - C17 hydrocarbons in the kerosene range, can be cooled, and taken out as a product meeting the applicable SPK specifications. In an alternative embodiment, the green jet stream can be taken out from the condensate stream in line 79 from the jet fractionator receiver 78 instead of refluxing all of the condensate back to the column. This green jet stream taken out from line 79 must be stripped to remove the light fraction. In such an embodiment, the side line 74 for recovering the green jet fuel stream is not provided.

[0073] The green diesel bottoms stream within bottoms line 76 can be split into a reboil stream that is reboiled and returned to the jet fractionator 70, a green diesel product stream within line 82, and a diluent stream within line 14. The diluent stream within line 14 is cooled by heat exchange with the bottoms line 66 of the separator and steam generation, recycled, and mixed with the olefin stream within line 12 in the oligomerization section 10 of FIG. 1, preferably the first olefin stream within line 12a, to provide a first diluted olefin stream within line 16a and absorb the heat generated within the dimerization reactor 22. Since the green diesel within the diluent line 14 is paraffinic, it is inert to the dimerization, oligomerization, and hydrogenation reactions it may undergo. Both the jet fuel stream within the sideline 74 and the diesel stream within line 82 can be cooled and fed to their respective fuel pools. The diesel stream meets the ASTM D975 standard for diesel.

[0074] The disclosed process can efficiently produce green jet fuel and green diesel fuel that meet applicable fuel requirements while managing the generation of heat of reaction, starting from ethylene. The carbon recovery rate in the process can exceed 95%.

[0075] Specific Embodiments The following is described in conjunction with specific embodiments, it being understood that this description is illustrative of the foregoing description and the scope of the appended claims and is not intended to limit them.

[0076] A first embodiment of the present invention is a process for oligomerizing an olefin stream, comprising diluting the olefin stream with a paraffin stream to provide a diluted olefin stream, dimerizing the diluted olefin stream with a dimerization catalyst to generate a dimerized olefin stream, and oligomerizing the dimerized olefin stream with an oligomerization catalyst to provide an oligomerized olefin stream. An embodiment of the present invention is one, any, or all of the embodiments from the previous embodiment of this paragraph to the first embodiment of this paragraph, further comprising dividing the olefin stream into a plurality of olefin streams, diluting a first olefin stream of the plurality of olefin streams with a paraffin stream to provide a first diluted olefin stream, and dimerizing the first diluted olefin stream to generate a first dimerized olefin stream. An embodiment of the present invention is one, any, or all of the embodiments from the previous embodiment of this paragraph to the first embodiment of this paragraph, further comprising cooling the first diluted olefin stream before dimerizing the olefin stream. An embodiment of the present invention is one, any, or all of the embodiments from the previous embodiment of this paragraph to the first embodiment of this paragraph, further comprising diluting a second olefin stream of the plurality of olefin streams with the first dimerized olefin stream to provide a second diluted olefin stream, and dimerizing the second diluted olefin stream to generate a second dimerized olefin stream. An embodiment of the present invention is one, any, or all of the embodiments from the previous embodiment of this paragraph to the first embodiment of this paragraph, further comprising cooling the second diluted olefin stream before dimerizing the second diluted olefin stream. An embodiment of the present invention is one, any, or all of the embodiments from the previous embodiment of this paragraph to the first embodiment of this paragraph, further comprising diluting the last olefin stream of the plurality of olefin streams with the second last dimerized olefin stream to provide a last diluted olefin stream, and dimerizing the last diluted olefin stream to generate a dimerized olefin stream. An embodiment of the present invention is one, any, or all of the embodiments from the previous embodiment of this paragraph to the first embodiment of this paragraph, further comprising saturating the oligomerized olefin stream to provide a paraffin stream.Embodiments of the present invention include, one, any, or all of the embodiments from the previous embodiment of this paragraph to the first embodiment of this paragraph, further comprising removing a heavy olefin stream from an oligomerized olefin stream, saturating the heavy olefin stream to produce a saturated heavy stream, and removing a paraffin stream from the saturated heavy stream. Embodiments of the present invention include, one, any, or all of the embodiments from the previous embodiment of this paragraph to the first embodiment of this paragraph, further comprising removing a diesel stream from the saturated heavy stream and removing a paraffin stream from the diesel stream. Embodiments of the present invention include, one, any, or all of the embodiments from the previous embodiment of this paragraph to the first embodiment of this paragraph, wherein the olefin stream is mainly ethylene. Embodiments of the present invention include, one, any, or all of the embodiments from the previous embodiment of this paragraph to the first embodiment of this paragraph, wherein the diluted olefin stream has 6 wt% or less ethylene. Embodiments of the present invention include, one, any, or all of the embodiments from the previous embodiment of this paragraph to the first embodiment of this paragraph, further comprising recycling the oligomerized olefin removed from the oligomerized olefin stream to the oligomerization process.

[0077] A second embodiment of the present invention is a process for oligomerizing an olefin stream, the process comprising dividing the olefin stream into a plurality of olefin streams, dimerizing a first olefin stream of the plurality of olefin streams to produce a first dimerized olefin stream, dimerizing a last olefin stream of the plurality of olefin streams to produce a dimerized olefin stream, and oligomerizing the dimerized olefin stream with an oligomerization catalyst to provide an oligomerized olefin stream. An embodiment of the present invention further comprises diluting the first olefin stream with a paraffin stream to provide a first diluted olefin stream, and dimerizing the first diluted olefin stream to produce a first dimerized olefin stream, and is any one, any combination, or all of the embodiments from the previous embodiment of this paragraph to the second embodiment of this paragraph. An embodiment of the present invention further comprises cooling the first diluted olefin stream before dimerizing the olefin stream, and is any one, any combination, or all of the embodiments from the previous embodiment of this paragraph to the second embodiment of this paragraph. An embodiment of the present invention further comprises diluting a second olefin stream of the plurality of olefin streams with the first dimerized olefin stream to provide a second diluted olefin stream, and dimerizing the second diluted olefin stream to produce a second dimerized olefin stream, and is any one, any combination, or all of the embodiments from the previous embodiment of this paragraph to the second embodiment of this paragraph. An embodiment of the present invention further comprises cooling the second diluted olefin stream before dimerizing the second diluted olefin stream, and is any one, any combination, or all of the embodiments from the previous embodiment of this paragraph to the second embodiment of this paragraph. An embodiment of the present invention further comprises removing a heavy olefin stream from the oligomerized olefin stream, saturating the heavy olefin stream to produce a saturated heavy stream, and removing a paraffin stream from the saturated heavy stream, and is any one, any combination, or all of the embodiments from the previous embodiment of this paragraph to the second embodiment of this paragraph.

[0078] A third embodiment of the present invention is a process for oligomerizing an olefin stream, the process comprising dividing the olefin stream into a plurality of olefin streams, dimerizing a first olefin stream of the plurality of olefin streams to produce a first dimerized olefin stream, and dimerizing a last olefin stream of the plurality of olefin streams to produce a dimerized olefin stream. An embodiment of the present invention further comprises oligomerizing the dimerized olefin stream with an oligomerization catalyst to provide an oligomerized paraffin stream, and is one, any, or all of the embodiments from the previous embodiment to the third embodiment of this paragraph.

[0079] Without further elaboration, using the foregoing description, one of ordinary skill in the art should be able to utilize the present disclosure to its fullest extent without departing from the spirit and scope of the present disclosure, and should be able to readily ascertain the essential characteristics of the present disclosure, make various changes and modifications to the present disclosure, and adapt it to various uses and conditions. Accordingly, the preceding preferred specific embodiments should be construed as merely illustrative and not in any way limiting of the remainder of the present disclosure, which is intended to cover various modifications and equivalent configurations within the scope of the appended claims.

[0080] In the above, all temperatures are given in degrees Celsius and all parts and percentages are by weight unless otherwise indicated.

Claims

1. A process for oligomerizing an olefin stream, comprising: diluting the olefin stream with a paraffin stream to provide a diluted olefin stream; dimerizing the diluted olefin stream with a dimerization catalyst to produce a dimerized olefin stream; oligomerizing the dimerized olefin stream with an oligomerization catalyst to provide an oligomerized olefin stream. A process for oligomerizing an olefin stream, comprising the above steps.

2. The process according to claim 1, further comprising: splitting the olefin stream into a plurality of olefin streams; diluting a first olefin stream of the plurality of olefin streams with the paraffin stream to provide a first diluted olefin stream; dimerizing the first diluted olefin stream to produce a first dimerized olefin stream.

3. The process according to claim 2, further comprising cooling the first diluted olefin stream before dimerizing the olefin stream.

4. The process according to claim 2, further comprising: diluting a second olefin stream of the plurality of olefin streams with the first dimerized olefin stream to provide a second diluted olefin stream; dimerizing the second diluted olefin stream to produce a second dimerized olefin stream.

5. The process according to claim 4, further comprising cooling the second diluted olefin stream before dimerizing the second diluted olefin stream.

6. The process according to claim 4, further comprising: diluting the last olefin stream of the plurality of olefin streams with the second last dimerized olefin stream to provide a last diluted olefin stream; dimerizing the last diluted olefin stream to produce the dimerized olefin stream.

7. The process according to claim 1, further comprising saturating the oligomerized olefin stream to provide the paraffin stream.

8. The process according to claim 7, further comprising: removing a heavy olefin stream from the oligomerized olefin stream; saturating the heavy olefin stream to produce a saturated heavy stream; removing the paraffin stream from the saturated heavy stream.

9. The process according to claim 8, further comprising: removing a diesel stream from the saturated heavy stream; removing the paraffin stream from the diesel stream.

10. The process according to claim 1, wherein the olefin stream is mainly ethylene.

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