Process for preparing an olefin stream for oligomerization with removal of oxygenates - Patent Application 20070122999

Abstract

A process for preparing an olefin stream for oligomerization includes fractionating the olefin stream to provide a light gas stream and an olefin-rich stream. Oxygenates are adsorbed from the olefin-rich stream into a water wash stream to provide an oxygenate-rich water wash stream and a washed olefin stream. Oxygenates can then be adsorbed from the washed olefin-rich stream before the deoxygenated stream is oligomerized.

Description

[Technical Field]

[0001] The field is the conversion of olefins to distillates. The field may specifically relate to preparing olefins for oligomerization to distillate fuels. [Background technology]

[0002] Molecular sieves, such as microporous crystalline zeolites, and non-zeolitic catalysts, particularly silicoaluminophosphate (SAPO), are known to promote the conversion of oxygenates, such as methanol, to light olefins. Highly efficient methanol to olefin (MTO) processes can convert oxygenates to light olefins that have typically been considered for plastic production. Light olefins produced from the MTO process are concentrated in ethylene and propylene, but also contain C4 to C8 olefins.

[0003] Ethylene can be oligomerized to olefins such as C4, C6, and C8 olefins. Propylene can be oligomerized to olefins such as C6, C9, and C12 olefins. Larger MTO olefins can also be oligomerized. Olefin oligomerization is a process by which smaller olefins can be oligomerized to larger olefins. More specifically, it can convert olefins to molecules with carbon lengths in the distillate range, including jet fuel and diesel range products. The oligomerized distillate can be saturated for use as transportation fuel.

[0004] Jet fuel is one of the few petroleum fuels that cannot be easily substituted in electric motor systems because of the high energy output required to fuel airplanes that electric motors cannot provide. Jet fuel has an end boiling point specification of less than 300 °C using ASTM D86. In certain regions, significant tax incentives are currently available for renewable jet fuel.

[0005] The product olefin stream from an MTO unit contains water and oxygenates that must be removed before encountering the oligomerization catalyst. In addition, the product olefin stream may contain diolefins and acetylenes, which can polymerize in the oligomerization reactor, fouling the process, requiring cleanup, and significantly reducing selectivity to distillate range fuels. An efficient process for preparing a renewable olefin feedstream for oligomerization to distillate range fuels is desired. Summary of the Invention

[0006] The inventors have developed a process for preparing an olefin stream for oligomerization that includes fractionating the olefin stream to provide a light gas stream and an olefin-rich stream. Oxygenates are adsorbed from the olefin-rich stream into a water wash stream to provide an oxygenate-rich water wash stream and a washed olefin stream. Oxygenates can then be adsorbed from the washed olefin-rich stream before the deoxygenated stream is oligomerized. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of the olefin feed preparation process and apparatus of the present disclosure. [Figure 2] FIG. 1 is a schematic diagram of the oligomerization feed preparation process and apparatus of the present disclosure. [Figure 3] FIG. 1 is a schematic diagram of an alternative embodiment of the oligomerization feed preparation process and apparatus of the present disclosure. [Figure 4]FIG. 2 is a schematic diagram of a further alternative embodiment of the oligomerization feed preparation process and apparatus of the present disclosure.

[0008] definition The term "communication" means that fluid flow is operably permitted between the listed components, which may be characterized as "fluid communication."

[0009] 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.

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

[0011] The term "direct communication" means that fluid flow from an upstream component enters a downstream component without passing through any other intervening vessel.

[0012] The term "indirect communication" means that fluid flow from an upstream component passes through an intervening vessel before entering a downstream component.

[0013] The term "bypass" means that an object is out of downstream communication with a bypass subject, at least to the extent that it bypasses.

[0014] As used herein, the term "predominant" or "majority" means more than 50%, suitably more than 75%, preferably more than 90%.

[0015] 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 stripping column may omit the reboiler at the bottom of the column and instead provide the heating requirements and separation driving force from a fluidized inert medium such as steam. Stripping columns typically feed a top tray and remove the main product from the bottom. The column may also refer to an extraction column for separating one or more components from a stream into an extract stream via liquid-liquid contact. A tower can also refer to an adsorption tower for separating one or more components from a gas stream into a liquid solvent stream.

[0016] 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."

[0017] 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.

[0018] As used herein, the terms "T5," "T10," "T90," or "T95" mean the temperature at which 5 percent, 10 percent, 90 percent, or 95 percent, by weight, of a sample boils, respectively, using ASTM D-86 or TBP, as the case may be.

[0019] 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.

[0020] 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.

[0021] As used herein, the term "diesel" refers to hydrocarbons boiling within a range of "diesel cut points" including an IBP of about 125°C (257°F) to about 175°C (347°F) or a T5 of about 150°C (302°F) to about 200°C (392°F), and a T95 of about 343°C (650°F) to about 399°C (750°F) using the TBP distillation method or a T90 of 280°C (536°F) to about 340°C (644°F) using ASTM D-86. The term "green diesel" or "renewable diesel" refers to diesel containing hydrocarbons not derived from fossil fuels.

[0022] As used herein, the term "jet fuel" means hydrocarbons boiling in the range of about 190°C (374°F) to about 215°C (419°F) T10 and about 290°C (554°F) to about 310°C (590°F). The terms "green jet fuel" or "renewable jet fuel" mean jet fuel containing hydrocarbons not derived from fossil fuels.

[0023] As used herein, the term "component-rich stream" means that the rich stream exiting the vessel has a higher concentration of the component than the feed to the vessel, and preferably than all other streams withdrawn from the vessel.

[0024] As used herein, the term "component lean stream" means that the lean stream exiting the vessel has a lower concentration of components than the feed to the vessel, and preferably than all other streams withdrawn from the vessel. DETAILED DESCRIPTION OF THE INVENTION

[0025] The disclosed process and apparatus involve treating an olefin reactor product produced by the reaction of methanol over a catalyst to serve as a feedstock for oligomerization utilizing a zeolite catalyst. Zeolite catalysts used in the oligomerization of olefinic hydrocarbons are sensitive to a variety of contaminants, including CO, ethers, ketones, aldehydes, dienes, acetylenes, sulfur, and nitriles. Finding a suitable feedstock can be difficult because these contaminants can cause permanent or temporary catalyst deactivation at ppm levels.

[0026] The olefin product from the reaction of methanol over the catalyst is a highly olefinic material and an excellent feedstock for oligomerization using a zeolite catalyst. However, the olefin product also contains various contaminants that must be removed for the zeolite catalyst to be effective. The olefin reactor effluent may contain CO in the range of about 100 to about 1000 wppm, CO2 in the range of about 50 to about 500 wppm, dimethyl ether (DME) in the range of about 1 to about 1.5 wt%, acetylene in the range of about 20 to about 50 wppm, and dienes in the range of about 1000 to about 3000 wppm, all of which must be addressed before sending to the oligomerization reactor. The olefin reactor effluent may also contain unreacted methanol.

[0027] The process and apparatus may include an olefin recovery section 10 illustrated in FIG. 1 and an oligomerization feed preparation section 110 illustrated in FIG.

[0028] Referring to FIG. 1 of the process and apparatus 10, a superheated feed stream in line 12 is supplied to an oxygenate conversion reactor 16, which reacts oxygenates, such as methanol or dimethyl ether (DME), with a fluidized catalyst. A hot vaporous reactor effluent stream in line 14 is withdrawn from the oxygenate conversion reactor 16, which periodically or continuously recycles the fluidized catalyst to a regeneration zone 18 in a conventional manner to maintain the desired selectivity and conversion. The oxygenate conversion reactor 16 is maintained at conditions effective for the conversion of oxygenates to produce light olefin products and oxygenated by-products. The hot vaporous reactor effluent stream may include light olefins, water, and oxygenates. The oxygenate conversion reactor 16 can be operated to produce a significant or predominant amount of propylene.

[0029] The hot vaporous reactor effluent stream in line 14 may be pre-cooled in reactor effluent heat exchanger 15 to recover heat before being passed to quench tower 20. In quench tower 20, the vaporous reactor effluent is directly contacted with a water stream provided in line 19, which may be taken from the stripped water stream in line 21, to remove superheat, neutralize organic acids, and remove catalyst fines. The quenched reactor effluent stream in line 22 leaves quench tower 20 and is provided to product separator column 24, which may be in downstream communication with oxygenate conversion reactor 16.

[0030] Product separator column 24 includes two sections for separating the reactor effluent stream into a product olefin stream in overhead line 40, an intermediate liquid stream in intermediate line 28, and a product water stream in bottoms line 26. The first, or lower, section receives the quenched reactor effluent stream in line 22. The lower section removes most of the heat from the quenched reactor effluent stream while partially condensing the water in the quenched reactor effluent stream to produce a product water stream in bottoms line 26 containing a portion of the oxygenate by-products in the quenched reactor effluent stream in line 22. A portion of the product water stream is cooled and pumped around to the top of the first section of product separator column 24 to cool the quenched reactor effluent stream in line 22. A second portion of the product water stream in bottoms line 26 is passed to water stripper column 30. A water return stream containing oxygenate by-products from compression section 80 in return line 32 may also be passed to water stripper column 30. The water stripper column 30 may be in downstream communication with the product separator column 24 .

[0031] The vapor stream from the first section of product separator column 24 is passed to the second, or upper, section of the product separator. An intermediate stream in line 28 containing hydrocarbons, oxygenate by-products, and liquid-phase water is withdrawn at the bottom of the upper section. A portion of the intermediate stream in line 28 is cooled and passed as a pumparound to the top of the second section of product separator column 24. The remainder of the intermediate stream in line 28 is passed to coalescer 29 to separate a hydrocarbon overhead stream from an aqueous stream in line 34, which is fed back to the product water stream sent to water stripper column 30 in line 36. An overhead product stream in line 40 containing olefins from product separator column 24 in line 40 is delivered to compression section 80.

[0032] The product water stream in line 36 contains dilute hydrocarbon oxygenates such as DME, methanol, acetaldehyde, acetone, and methyl ethyl ketone (MEK). Water stripper column 30 separates or strips the oxygenates into a methanol and oxygenate-rich stream in overhead 49 that is rich in both methanol and at least one other oxygenate, and an oxygenate-lean water stream in bottoms line 46. A first portion of the oxygenate-lean water stream in line 46 is recycled to the process via the stripped water stream in line 21. A second portion is discharged to the wastewater stream in line 23.

[0033] In one embodiment, water stripper column 30 may operate at a temperature of from about 115°C (239°F) to 200°C (392°F) at the bottom of the water stripper column, and a pressure of from about 70 kPa(g) (10 psig) to about 830 kPa(g) (120 psig) at the top of water stripper column 30.

[0034] The product olefin stream in product overhead line 40 carries valuable olefin product that needs to be recovered. Compression section 80 increases the pressure of the product olefin stream necessary for downstream processing such as that used in conventional light olefin recovery units. Compression section 80 may include a first knockout drum 82 that separates the product olefin stream into a pressurized first olefin-rich stream in overhead line 83 at a temperature of from about 20°C (68°F) to about 60°C (140°F) and a pressure of from about 150 kPa(g) (22 psig) to about 280 kPa(g) (41 psig), and an oxygenate-rich first aqueous stream in bottoms line 84. The olefin-rich stream in overhead line 83 may be fed to compressor 85, cooled, and directed to second knockout drum 86. The aqueous stream in bottoms line 84 is pumped via manifold line 76 to return line 32 which returns the water stream to water stripper column 30 along with the product water stream in product separator bottoms line 36 .

[0035] Compression section 80 may include a second knockout drum 86 that separates the pressurized first olefin-rich stream into a second pressurized olefin-rich stream in overhead line 87 at a pressure of from about 300 kPa(g) (44 psig) to about 400 kPa(g) (58 psig) and a temperature of from about 20°C (68°F) to about 60°C (140°F), and a second oxygenate-rich aqueous stream in bottoms line 88. The second olefin-rich stream in overhead line 87 may be fed to compressor 89, cooled, and directed to third knockout drum 90. The aqueous stream in bottoms line 88 is pumped to return line 32 via manifold line 76 that returns the water stream to water stripper column 30 along with the product water stream in product separator bottoms line 36.

[0036] Compression section 80 may include a third knockout drum 90 that separates the pressurized second olefin-rich stream into a third pressurized olefin-rich stream in overhead line 91 and a third oxygenate-rich aqueous stream in bottoms line 92. The third olefin-rich stream in overhead line 91 may be fed to oxygenate adsorber 50. The aqueous stream in bottoms line 92 is passed to return line 32 via manifold line 76 that returns the water stream to water stripper column 30 along with the product water stream in product separator bottoms line 36.

[0037] Suitable compressor types may include centrifugal, positive displacement, piston, diaphragm, screw, etc. In one embodiment, compressors 85, 89 in compressor section 80 are centrifugal compressors. The final discharge pressure may be from about 1.0 MPa(g) (145 psig) to about 2.1 MPa(g) (305 psig). The compressor discharge may be cooled to about ambient temperature using conventional heat transfer methods.

[0038] 1 , and in accordance with a preferred embodiment, at least a portion of the compressed product stream via overhead line 91 is contacted with a cooled lean water stream in line 102 in oxygenate adsorber column 50 at conditions effective to adsorb at least some of the effluent oxygenates without prior removal of oxygenates and without water being taken directly from product separator column 24. The contact in oxygenate adsorber column 50 produces an adsorbed olefin-rich stream in overhead line 54 and an adsorbed water-rich stream containing some of the effluent oxygenates in bottoms line 52. Oxygenate adsorber column 50 may have operating conditions including a bottoms temperature range of about 30° C. (86° F.) to about 60° C. (140° F.) and a tops pressure range of about 700 kPa(g) (101 psig) to about 1 MPa(g) (145 psig).

[0039] The adsorbed olefin-rich stream in overhead line 54 is fed to third-stage knockout drum 60, where a gaseous olefin stream is taken in overhead line 61 to third compressor 62, while water and oxygenates are taken in bottoms line 59 to manifold line 76. Third-stage knockout drum 60 may operate at about the same pressure as the oxygenate adsorber overhead and at a temperature of from about 32°C (90°F) to about 52°C (125°F). The gaseous olefin stream in line 61 is compressed in third compressor 62 to form a compressed gaseous olefin stream in line 63, which then combines with a stream in stripper overhead line 71, is partially condensed by cooling in feed chiller 64, and is fed in line 65 to stripper separator 66. Stripper separator 66 separates an aqueous stream containing oxygenates in the boot in line 67 which feeds manifold line 76, a light olefin vapor stream in overhead line 68 containing C3- olefins, and a heavy olefin liquid stream containing C4+ olefins in line 69. The heavy olefin liquid stream in line 69 is stripped in DME stripper column 70 to remove C3 and heavier vapors in stripper overhead line 71 from the heavy olefin liquid stream in stripper bottoms line 168. In one embodiment, a reboil stream is taken from the heavy olefin liquid stream in stripper bottoms line 168 which is reboiled in DME stripper reboiler 167 and returned to DME stripper column 70. Most of the oxygenates will be stripped into stripper overhead line 71 and separated as they are recycled to stripper separator 66 after cooling. The bottoms stream exiting DME stripper column 70 may be sent through line 168 and via line 169 to selective hydrogenation reactor 170, as shown in Figure 2. This stream contains primarily C4+ olefins, but also diolefins that will inhibit the oligomerization catalyst requiring selective hydrogenation. DME stripper column 70 may operate at an overhead temperature of from about 60°C (140°F) to about 82°C (180°F) and a bottoms pressure of from about 1.8 MPa(g) (260 psig) to about 2.2 MPa(g) (320 psig).Stripper separator 66 may operate at a temperature of about 10°C (50°F) to about 60°C (140°F) and a pressure of about 1.7 MPa(g) (250 psig) to about 2.1 MPa(g) (300 psig). The light olefin vapor stream in overhead line 68 is scrubbed in caustic scrubber 73 by countercurrent contact with a caustic solution in line 42 to adsorb acid gases, such as carbon dioxide, from the light olefin vapors exiting caustic scrubber 73 in overhead line 74. The acid gas-rich caustic solution exits caustic scrubber 73 in line 44. Caustic scrubber 73 may operate at an overhead temperature of about 32°C (90°F) to about 54°C (130°F) and a pressure of about 1.7 MPa(g) (250 psig) to about 2.0 MPa(g) (290 psig).

[0040] The scrubbed light olefins vapor stream in overhead line 74 is cooled with propylene refrigerant in dryer feed chiller 75 to liquefy a portion of the light olefins vapor stream and provide a cooled, scrubbed first vapor olefins stream in line 33. The cooled, scrubbed first vapor olefins stream in line 33 is separated in dryer separator 45 to provide an aqueous stream from the boot in line 47 that is carried over to manifold line 76, a vaporous light olefins stream comprising C3− hydrocarbons and gases in overhead line 77, and a liquid light olefins stream in bottoms line 78 comprising C3+ hydrocarbons. The vaporous light olefins stream in overhead line 77 is dried in dryer 79a to provide a vaporous product olefins stream in line 112. The liquid light olefins stream in bottoms line 78 is pumped to dryer 79b for drying and to provide a liquid product olefins stream in line 114. The product olefin streams in lines 112 and 114 are processed in oligomerization feed preparation section 110 of FIG.

[0041] Referring to oligomerization feed preparation section 110 of Figure 2, a vaporous product olefin stream in line 112 is fed to fractionation section 108. The vaporous product olefin stream in line 112 comprises a C2-olefin stream and may comprise primarily ethylene. In an embodiment, a liquid product olefin stream in line 114 may be fed to fractionation section 108. The liquid product olefin stream in line 114 comprises a C3+ olefin stream and may comprise primarily propylene. The C3 olefin stream may also comprise C4 to C8 olefins. In the fractionation section, the vaporous product olefin stream in line 112 and / or the liquid product olefin stream in line 114 are fractionated to provide a light gas stream in line 120 and an olefin-rich stream in line 122.

[0042] In some embodiments, the vaporous product olefin stream in line 112 may be fed to demethylator fractionation column 116. The vaporous product olefin stream in line 112 may be fed to the top half of demethylator fractionation column 116. In some embodiments, the vaporous product olefin stream in line 112 may be passed to first suction drum 113 and then compressed in first compressor 133. The vaporous product olefin stream may be removed from first compressor 133 in line 115 and passed to first heat exchanger 107. The cooled vaporous product olefin stream is removed from heat exchanger 107 in line 117 and passed to demethanizer fractionation column 116.

[0043] In some embodiments, the liquid product olefin stream in line 114 may be fed to demethanizer fractionation column 116. The liquid product olefin stream in line 114 may be fed to the bottom half of demethylator fractionation column 116. In some embodiments, the liquid product olefin stream in line 114 may be passed to a second heat exchanger 109. A cooled liquid product olefin stream is removed from heat exchanger 109 in line 119 and passed to demethanizer fractionation column 116. The vaporous product olefin stream and the liquid product olefin stream may be fractionated together in demethanizer fractionation column 116.

[0044] In one embodiment, the vaporous product olefin stream in line 115 and the liquid product olefin stream in line 114 may be combined and passed to a combining heat exchanger (not shown). The combined heat exchanged streams may be separated in demethanizer fractionation column 116.

[0045] The vaporous product olefin stream and / or liquid product olefins are preferably fractionated together in demethanizer fractionation column 116 to provide an overhead light gas stream in overhead light gas line 118 and an olefin-rich bottoms stream in bottoms line 122, which may be considered a demethanized olefin-rich stream. The overhead light gas stream in line 118 may contain methane light gases and lighter gases such as carbon monoxide, carbon dioxide, methane, nitrogen, and hydrogen. Essentially all of the carbon monoxide will exit in the overhead light gas stream in line 118. The overhead light gas stream in line 118 is condensed in demethanizer condenser 123 and fed to demethanizer receiver 124. The condensed light gases are refluxed from demethanizer receiver 124 to column 116 in reflux line 121, while the light gas stream is removed in net overhead line 120. A reactor purge gas stream in line 126 may be taken from the light gas stream to the oxygenate conversion reactor 16 and a fuel gas stream may be taken in line 127 .

[0046] An olefin-rich stream comprising C2+ olefins, typically C2 to C8 olefins, in demethanizer bottoms line 122 may be split into a reboil stream in line 128 that is reboiled in demethanizer reboiler 111 and returned to the column, and a net olefin-rich stream in net bottoms line 130. The demethanizer bottoms temperature may be from about 0°C (32°F) to about 45°C (113°F) and a pressure from about 2.4 MPa(g) (350 psig) to about 3.5 MPa(g) (500 psig). Alternatively, the demethanizer bottoms temperature may be from about -40°C (-40°F) to about 10°C (50°F) and the bottoms pressure may be from about 0.7 MPa(g) (102 psig) to about 2.1 MPa(g) (305 psig).

[0047] The olefin-rich stream contains significant levels of dienes, acetylene, dimethyl ether, and other oxygenates, all of which are poisonous to the oligomerization catalyst. In some embodiments, the olefin-rich stream may be further fractionated to separately prepare ethylene and propylene. If the ethylene is routed to the selective hydrogenation reactor 170, it may become completely saturated with ethane, rendering it inactive in the oligomerization reactor and unable to oligomerize, adversely affecting jet fuel yield. Therefore, the net olefin-rich stream in line 130 may be further fractionated in the deethanizer column 132.

[0048] The net olefin-rich stream in line 130 is deethanized by fractionation in deethanizer column 132 to provide an ethylene stream in net overhead line 134 and a fractionated olefin-rich stream in net deethanized bottoms line 136. The fractionated olefin-rich stream may be considered a deethanized olefin-rich stream. Deethanizer column 132 may operate at a bottoms temperature of from about 43°C (110°F) to about 104°C (220°F) and an overhead pressure of from about 1.8 MPa(g) (260 psig) to about 3.2 MPa(gauge) (460 psig).

[0049] The ethylene overhead stream in overhead line 138 is condensed in deethanizer condenser 139 and separated in deethanizer receiver 140. Liquid from deethanizer receiver 140 may be refluxed from the bottom of deethanizer receiver 140 back to deethanizer column 132 in reflux line 141. The net overhead vapor stream from deethanizer receiver 140 in line 134 is sent to acetylene feed effluent exchanger 143 where it may be heated by heat exchange with a concentrated ethylene stream in line 212 and combined with a hydrogen stream from line 214 to provide an acetylene conversion feed stream in combined line 216. The acetylene converter feed stream in line 216 may be further heated in acetylene converter feed heater 145 to provide a heated acetylene converter feed stream in line 217, which is charged to acetylene conversion reactor 210. In acetylene conversion reactor 210, acetylene is converted to ethylene in the presence of hydrogen over an acetylene conversion catalyst, thereby producing a concentrated ethylene stream in line 212. The concentrated ethylene stream in line 212 is cooled in acetylene feed effluent heat exchanger 143 by heat exchange with the net overhead vapor stream in line 134 to provide an ethylene stream in line 213. The deethanized stream in bottoms line 142 may be split between a reboil stream in line 144 that is reboiled in deethanizer reboiler 147 and a reboil stream that boils back to deethanizer column 132 to provide the column heating requirements. The acetylene conversion catalyst may be a palladium and silver catalyst on aluminum oxide. The acetylene conversion conditions may include a pressure of about 1.4 MPa(g) (200 psig) to about 2.8 MPa(g) (400 psig) and a temperature of about 38°C (100°F) to about 93°C (200°F).

[0050] The fractionated olefin-rich stream in net bottoms line 136 may contain oxygenates such as dimethyl ether, methanol, and acetaldehyde in concentrations that poison the selective hydrogenation catalyst and the oligomerization catalyst. Thus, the olefin-rich stream in line 136 is routed to a water wash column 150 to adsorb the oxygenates such as dimethyl ether, methanol, and acetaldehyde from the fractionated olefin-rich stream to provide an oxygenate-rich water wash stream and a washed olefin-rich stream. The washed olefin-rich stream may be oligomerized.

[0051] In water wash column 150, the water wash stream from DME wash water stripper column 160 is routed to the upper third of the water wash column in cooled, stripped wash water line 152 and countercurrently contacted with the fractionated, deethanized olefin-rich stream in net bottoms line 136, which feeds the lower third of the water wash column. Countercurrent contact between the fractionated, deethanized olefin-rich stream and the water wash stream causes oxygenates, including DME, to be adsorbed from the fractionated, deethanized olefin-rich stream into the water wash stream. The adsorption produces a washed olefin-rich stream in overhead line 154 and an oxygenate-rich water wash stream in bottoms line 156. The washed olefin-rich stream in overhead line 154 has a total oxygenate concentration of 1000 wppm or less, which is acceptable for the selective hydrogenation catalyst in selective hydrogenation reactor 170. Suitably, the washed olefin-rich stream in overhead line 154 has a total oxygenate concentration of 500 wppm or less to accommodate the adsorbent bed size in oxygenate removal unit 180. Preferably, the washed olefin-rich stream in overhead line 154 has a total oxygenate concentration of 50 wppm or less. Water wash column 150 may operate at a bottoms temperature of from about 10°C (50°F) to about 66°C (150°F) and an overhead pressure of from about 2.4 MPa(g) (350 psig) to about 3.2 MPa(g) (450 psig).

[0052] The oxygenate-rich water wash stream in bottoms line 156 is heated in DME wash water exchanger 149 to produce a heated oxygenate-rich water wash stream in line 157, which is fed to DME wash water stripper column 160 to strip DME and other oxygenates. In DME wash water stripper column 160, DME and oxygenates are stripped from the oxygenate-rich water wash stream to produce a recycled DME stream in line 162, which also contains other oxygenates that may be recycled to oxygenate conversion reactor 16 of FIG. 1. A stripped water wash stream is produced in bottoms line 164. A reboil stream in line 166 is removed from the stripped water wash stream in bottoms line 164, reboiled in DME wash water stripper reboiler 161, and transported back to DME wash water stripper column 160. A cooled, stripped wash water stream is removed from the stripped water wash stream in bottoms line 164 and cooled in DME wash water exchanger 149, possibly followed by wash water cooler 151, to produce a cooled, stripped wash water stream in line 152, which is recycled to water wash column 150, possibly after being supplemented with make-up water in line 158. In an alternative embodiment, the make-up water stream in line 158 may be passed directly to DME wash water stripper column 160.

[0053] The washed olefin-rich stream in line 154 may be oligomerized, possibly in the liquid phase, in oligomerization reactor 200. However, the washed olefin-rich stream in water wash overhead line 154, which contains C3-C6 olefins, also contains diolefins, which can cause cross-polymerization in the oligomerization reactor. Therefore, it may be selectively hydrogenated to convert diolefins and acetylenes to monoolefins before passing to the oligomerization reactor. Because the C4+ olefins in DME-stripped line 168 from FIG. 1 may also contain diolefins, they may also benefit from selective hydrogenation before oligomerization. The washed olefin-rich stream in water wash overhead line 154 may be combined with the heavy olefin stream in line 168 to provide a combined olefin stream in combined line 169. The combined olefin stream in combined line 169 may be mixed with hydrogen from line 155, possibly heated by heat exchange in heat exchanger 171 with a mono-olefin stream in line 174, and input to selective hydrogenation reactor 170 via selective hydrogenation reactor input line 172. In selective hydrogenation reactor 170, di-olefins and residual acetylene are converted to mono-olefins to provide a mono-olefin stream in line 174. Selective hydrogenation results in only minimal hydrogenation of mono-olefins to paraffins.

[0054] The selective hydrogenation reactor 170 typically operates under relatively mild hydrogenation conditions. These conditions typically result in hydrocarbons existing as liquid phase materials. The reactants typically will be maintained under a minimum pressure sufficient to maintain the reactants as liquid phase hydrocarbons. Suitable operating pressures include from about 2.3 MPa(g) (330 psig) to about 3.1 MPa(g) (450 psig). Relatively mild temperatures of from about 20°C (68°F) to about 100°C (212°F) are typically used. The liquid hourly space velocity of the reactants over the selective hydrogenation catalyst is about 1.0 hr -1 Super ~ about 35.0 hours -1To avoid undesired saturation of significant amounts of monoolefinic hydrocarbons, the molar ratio of hydrogen to diolefinic hydrocarbons in the selective hydrogenation reactor input line 172 entering the selective hydrogenation catalyst bed is maintained between 1:1 and 4.5:1.

[0055] Suitable selective hydrogenation catalysts include, but are not limited to, catalysts comprising copper and at least one other metal, such as titanium, vanadium, chromium, manganese, cobalt, nickel, zinc, molybdenum, palladium, and cadmium, or mixtures thereof. The metal is preferably supported on an inorganic oxide support, such as, for example, silica and alumina. The monoolefin stream may exit the reactor in line 174 having a higher concentration of monoolefins and a lower concentration of acetylenes and dienes than the selective hydrogenation reactor input stream in line 172. The monoolefin stream in line 174 may contain an acetylene and diolefin concentration of about 50 to about 80 wppm or less.

[0056] The mono-olefin stream in line 174 may be oligomerized in oligomerization reactor 200, possibly in a mixed or liquid phase. However, the mono-olefin stream still has a high concentration of oxygenates that may suppress oligomerization catalyst activity. Therefore, the selectively hydrogenated stream in line 174 may be transported to oxygenate removal unit 180 for adsorbing the remaining oxygenates, including DME, water, and other trace oxygenates. Oxygenate removal unit 180 may include one or more adsorber vessels 182, 184, such that one or more adsorber vessels 182 or 184 may be fed with the mono-olefin stream in line 174 to adsorb oxygenates therefrom by appropriate valve control, and one of the other adsorber vessels 184 or 182 may be fed with a regenerant stream via line 188 to undergo regeneration by appropriate valve control. The mono-olefin stream in line 174 may flow upward through adsorber vessels 182, 184, although downward flow is also preferred. Three adsorber vessels may be used in the oxygenate removal unit. A deoxygenated olefin stream may be recovered from oxygenate removal unit 180 in line 186. An oxygenated regenerant stream may be recovered from oxygenate removal unit 180 in line 190. The deoxygenated olefin stream in line 186 comprises C3-C8 olefins and less than 1 wppm of oxygenates, including DME and water.

[0057] When adsorber vessels 182, 184 require regeneration, they may be taken off stream with the selectively hydrogenated stream in line 174 and contacted with heated vaporous regenerant from line 188 by appropriate valve control in a direction opposite to the normal flow of the olefinic selectively hydrogenated stream. The regenerant may be a clean inert gas, such as nitrogen, hydrogen, natural gas, or light paraffins, such as propane, butane, and pentane. The regenerant may fully restore the capacity of the adsorbent in the regenerated vessels 182, 184. Spent regenerant may leave the oxygenate removal unit 180 in spent regenerant line 190. The oxygenate removal unit may operate at an inlet temperature of about 26°C (50°F) to about 66°C (150°F) and an inlet pressure of about 2.3 MPa(g) (330 psig) to about 3 MPa(g) (430 psig). The adsorbent in oxygenate removal unit 180 may be a large pore molecular sieve, such as 13x.

[0058] The deoxygenated olefin stream in line 186 may provide an oligomerization input stream in line 198 that may be input to oligomerization reactor 200. Alternatively, or cumulatively, the concentrated ethylene stream in line 213 may be compressed to a higher pressure in compressor 157 and input to one or more oligomerization reactors 200 in the oligomerization input stream in line 198. Oligomerization reactor 200 may comprise a two-stage reactor system, and each stage may comprise multiple layers.

[0059] The oligomerization input olefin stream in line 198 may contact an oligomerization catalyst in oligomerization reactor 200 to oligomerize ethylene, propylene, and C4+ olefins into oligomers. A third stream containing unreacted C3+ olefins in recycle line 199 may be passed to oligomerization reactor 200. In some embodiments, the third stream in line 199 may be combined with the oligomerization input stream in line 198 and passed to oligomerization reactor 200. The oligomerization reaction generates a large exotherm. As a result, this large exotherm must be managed. To manage the exotherm, the input olefin stream may be diluted with a diluent stream in line 202 to provide a diluted olefin stream to absorb the exotherm. The diluent stream may include a light paraffin stream. Additionally, the input olefin stream may be split and fed to multiple oligomerization reactors 200. The oligomerization reaction temperature may be from about 110°C (230°F) to about 260°C (500°F), and the oligomerization pressure may be from about 3.5 MPa(g) (500 psig) to about 8.4 MPa(g) (1200 psig). The input olefin stream in line 198 may be cooled prior to entry into oligomerization reactor 200. The oligomerized stream may be discharged from oligomerization reactor 200 in line 204.

[0060] Figure 3 illustrates an embodiment that omits the deethanizer column and acetylene converter. Many of the elements in Figure 3 have the same configuration and bear the same reference numbers as in Figure 2. Elements in Figure 3 that correspond to elements in Figure 2 but have a different configuration bear the same reference numbers as in Figure 2 but are prefixed with a prime (').

[0061] In the embodiment of Figure 3, fractionation section 108' includes only demethanizer fractionation column 116. The olefin-rich stream in demethanizer net bottoms line 130' is transported directly to water wash column 150. Water wash column 150 adsorbs oxygenates from the olefin-rich stream into a water wash stream of cooled, stripped wash water in line 152 to provide an oxygenate-rich water wash stream in line 156 and a washed olefin stream in line 154, which may be selectively hydrogenated in selective hydrogenation reactor 170 and / or subjected to oxygenate removal in oxygenate removal unit 180 to provide an input stream in line 198' to oligomerization reactor 200. With the exceptions noted above, Figure 3 is constructed and operates like the embodiment illustrated in Figure 2.

[0062] FIG. 4 illustrates an embodiment in which the deethanizer column 132'' and the acetylene converter are moved downstream of the water wash column 150''. Many of the elements in FIG. 4 have the same configuration as in FIG. 2 and bear the same reference numbers. Elements in FIG. 4 that correspond to elements in FIG. 2 but have a different configuration bear the same reference numbers as in FIG. 2 but are prefixed with a double prime symbol ('').

[0063] In the embodiment of FIG. 4 , in fractionation section 108″, the olefin-rich stream in demethanizer net bottoms line 130″ is transported directly to water wash column 150″. Water wash column 150″ adsorbs oxygenates from the olefin-rich stream into a cooled, stripped wash water stream in line 152 to provide an oxygenate-rich water wash stream in line 156 and a washed olefin stream in line 154″. The washed olefin stream in line 154″ is dried in dryer 163 to provide a dried, washed olefin stream in line 165. The dried, washed olefin stream in line 165 is then deethanized in deethanizer fractionation column 132″ to provide a fractionated olefin-rich stream in deethanizer net bottoms line 136″ and an ethylene stream in deethanizer overhead line 138″. The fractionated olefin-rich stream in deethanizer net bottoms line 136" may be selectively hydrogenated in selective hydrogenation reactor 170 and / or subjected to oxygenate removal in oxygenate removal unit 180 to provide an input stream in line 198" to oligomerization reactor 200. The ethylene stream in deethanizer overhead line 138" may be subjected to acetylene conversion in acetylene conversion reactor 210" to produce an enriched ethylene stream in line 134". The enriched ethylene stream may be combined with the mono-olefins stream in line 174 or the deoxygenated olefins stream in line 186 to provide an oligomerization input stream in line 198" and oligomerized in oligomerization reactor 200. With the exceptions noted above, FIG. 4 is configured and operates like the embodiment illustrated in FIG. 2. [Example]

[0064] The inventors conducted a simulation to demonstrate the effectiveness of a water wash tower in scrubbing DME from an olefin stream. The feed olefin stream contained a DME concentration of about 2.7 wt.%. The feed olefin stream was washed with water in the water wash tower. The concentration of DME in the wash olefin stream at the top of the tower was less than 50 wppm.

[0065] 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.

[0066] A first embodiment of the present disclosure is a process for treating an olefin stream, comprising: fractionating the olefin stream to provide a light gas stream and an olefin-rich stream; adsorbing oxygenates from the olefin-rich stream in a water wash stream to provide an oxygenate-rich water wash stream and a washed olefin-rich stream; and adsorbing oxygenates from the washed olefin-rich stream. Certain embodiments of the present disclosure are one, any, or all of the preceding through first embodiments of this paragraph, further comprising oligomerizing the washed olefin-rich stream after adsorption. Certain embodiments of the present disclosure are one, any, or all of the preceding through first embodiments of this paragraph, wherein fractionating the olefin stream comprises deethanizing the olefin stream to provide an ethylene stream and an olefin-rich stream.

[0013] Certain embodiments of the present disclosure are any one, any, or all of the preceding through first embodiments of this paragraph, wherein fractionating the olefin stream further comprises demethanizing the olefin stream to provide a light gas stream and a demethanized olefin-rich stream, and deethanizing the demethanized olefin-rich stream to provide an ethylene stream and a deethanized olefin-rich stream, and wherein the olefin-rich stream onto which the oxygenates are adsorbed is the deethanized olefin-rich stream. Certain embodiments of the present disclosure are any one, any, or all of the preceding through first embodiments of this paragraph, further comprising selectively hydrogenating the washed olefin-rich stream prior to adsorption. Certain embodiments of the present disclosure are any one, any, or all of the preceding through first embodiments of this paragraph, further comprising selectively hydrogenating the washed deethanized olefin stream prior to adsorption. Certain embodiments of the present disclosure are one, any, or all of the preceding through first embodiments of this paragraph, further comprising regenerating the adsorbent with a hot inert gas regenerant. Certain embodiments of the present disclosure are one, any, or all of the preceding through first embodiments of this paragraph, further comprising oligomerizing the washed olefin-rich stream in the liquid phase.An embodiment of the present disclosure is one, any, or all of the preceding embodiments through the first embodiment of this paragraph, further comprising converting acetylene in the ethylene stream to ethylene in the presence of hydrogen to provide an enriched ethylene stream, and oligomerizing the enriched ethylene stream. An embodiment of the present disclosure is one, any, or all of the preceding embodiments through the first embodiment of this paragraph, further comprising oligomerizing the enriched ethylene stream with the washed olefin-rich stream. An embodiment of the present disclosure is one, any, or all of the preceding embodiments through the first embodiment of this paragraph, wherein the demethanized olefin-rich stream comprises C2 to C8 olefins. An embodiment of the present disclosure is one, any, or all of the preceding embodiments through the first embodiment of this paragraph, wherein the deethanied olefin-rich stream comprises C3 to C8 olefins. An embodiment of the present disclosure is one, any, or all of the preceding through first embodiments of this paragraph, wherein the lighter gas stream comprises one or more of carbon monoxide, carbon dioxide, nitrogen, hydrogen, and methane. An embodiment of the present disclosure is one, any, or all of the preceding through first embodiments of this paragraph, further comprising selectively hydrogenating the washed olefin-rich stream in the presence of hydrogen to convert dienes and acetylenes to mono-olefins prior to the oligomerization step. An embodiment of the present disclosure is one, any, or all of the preceding through first embodiments of this paragraph, wherein the selective hydrogenation step precedes the adsorption step. An embodiment of the present disclosure is one, any, or all of the preceding through first embodiments of this paragraph, further comprising stripping the oxygenate-rich water wash stream to provide a water wash stream. An embodiment of the present disclosure is one, any, or all of the preceding embodiment of this paragraph through the first embodiment of this paragraph, wherein the olefin stream is taken from an oxygenate conversion reactor.An embodiment of the present disclosure is one, any, or all of the preceding embodiment of this paragraph through the first embodiment of this paragraph, further comprising: compressing the product olefin stream to provide a compressed product olefin stream; stripping the compressed product olefin stream to provide a light olefin stream and a heavy olefin stream; and using the washed olefin-rich stream to adsorb oxygenates from the heavy olefin stream.

[0067] A second embodiment of the present disclosure is a process for treating an olefin stream, comprising: fractionating the olefin stream to provide a light gas stream and an olefin-rich stream; adsorbing oxygenates from the olefin-rich stream into a water wash stream to provide an oxygenate-rich water wash stream and a washed olefin-rich stream; and adsorbing oxygenates from the washed olefin-rich stream.

[0068] A third embodiment of the present disclosure is a process for treating an olefin stream, comprising: fractionating a vaporous olefin stream and a liquid olefin stream to provide a light gas stream and an olefin-rich stream; adsorbing oxygenates from the olefin-rich stream into a water wash stream to provide an oxygenate-rich water wash stream and a washed olefin-rich stream; and adsorbing oxygenates from the washed olefin-rich stream.

[0069] 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.

[0070] 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 treating an olefin stream, comprising: fractionating the olefin stream to provide a light gas stream and an olefin-rich stream; adsorbing oxygenates from the olefin-rich stream into a water wash stream to provide an oxygenate-rich water wash stream and a washed olefin-rich stream; adsorbing oxygenates from said washed olefin-rich stream.

2. 10. The process of claim 1, further comprising oligomerizing the washed olefin-rich stream after adsorption.

3. 10. The process of claim 1, wherein fractionating the olefin stream comprises deethanizing the olefin stream to provide an ethylene stream and the olefin-rich stream.

4. 2. The process of claim 1, wherein fractionating the olefin stream further comprises demethanizing the olefin stream to provide the light gas stream and a demethanized olefin-rich stream; and deethanizing the demethanized olefin-rich stream to provide an ethylene stream and a deethanized olefin-rich stream, wherein the olefin-rich stream onto which oxygenates are adsorbed is the deethanized olefin-rich stream.

5. 10. The process of claim 1 further comprising selectively hydrogenating the washed olefin-rich stream prior to adsorption.

6. 5. The process of claim 4, further comprising selectively hydrogenating the washed, deethanized olefin stream prior to adsorption.

7. 10. The process of claim 1 further comprising regenerating the adsorbent with a hot inert gas regenerant.

8. 10. The process of claim 1, further comprising oligomerizing the washed olefin-rich stream in the liquid phase.

9. 5. The process of claim 4, further comprising converting acetylene in the ethylene stream to ethylene in the presence of hydrogen to provide a concentrated ethylene stream; and oligomerizing the concentrated ethylene stream.

10. 10. The process of claim 9, further comprising oligomerizing said concentrated ethylene stream with said washed olefin-rich stream.

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