By-product recirculation to provide a green hydrogen stream for methanol-jet fuel processes.

Abstract

In methanol-jet fuel complexes, hydrogen is required for several different processes, including oligomerization. Hydrogen is produced by steam methane reforming and autothermal reforming. Greater efficiency is provided by increasing the amount of available hydrogen by feeding an off-gas stream from a tower, including demethane units, depropane units, and flash strippers, into the reforming reactor.

Description

Technical Field

[0001] This field is the conversion of olefins to distillates. This field may relate particularly to the use of by-products for hydrogen production.

Background Art

[0002] Molecular sieves, such as microporous crystalline zeolites and non-zeolite catalysts, particularly silicoaluminophosphate (SAPO), are known to promote the conversion of oxygenates, such as methanol, to light olefins. A highly efficient Methanol to Olefin (MTO) process can convert oxygenates to light olefins that have typically been considered for plastic production. The light olefins produced from the MTO process are highly concentrated in ethylene and propylene.

[0003] The ethanol dehydration process involves dehydrating ethanol molecules to produce ethylene and water. The process of converting ethanol to ethylene is essentially endothermic, and the heat of the endothermic reaction is typically provided to an adiabatic reactor by a heating furnace.

[0004] Ethylene can oligomerize to olefins such as C4, C6, and C8 olefins. Propylene can oligomerize to olefins such as C6, C9, and C12 olefins. The oligomerization of olefins is a process that can oligomerize smaller olefins to larger olefins. More specifically, olefins containing oligomerized 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.

[0005] Jet fuel is one of the few petroleum fuels that cannot be easily replaced by electric motor systems because the fuel for aircraft requires a high energy output that electric motors cannot provide. Jet fuel has an endpoint boiling point specification of less than 300°C when using ASTM D86. Significant incentives are currently available for green jet fuel in certain regions.

[0006] The oligomerization unit requires hydrogen to meet the requirements for sustainable jet fuel. An improved process is provided to recirculate a hydrogen-rich off-gas flow to supplement the hydrogen produced by reforming.

[0007] definition The term "communication" means that fluid flow is operably permitted between the enumerated components, and this can be characterized as "fluid communication."

[0008] The term "downstream communication" means that at least a portion of the fluid flowing to the downstream-communicating object can be operably flowed from the fluid-communicating object. The term "upstream communication" means that at least a portion of the fluid flowing from an upstream communication object can flow operably into a fluid-communicated object.

[0009] The term "direct communication" means that the fluid flow from the upstream component enters the downstream component without passing through any other intervening container. The term "indirect communication" refers to the flow of fluid from an upstream component entering a downstream component after passing through an intervening container.

[0010] The term "bypass" means that an object is removed from downstream communication with the object it is bypassing, at least to the extent that it is bypassing it. As used herein, the terms “main” or “major” mean more than 50%, preferably more than 75%, and more preferably more than 90%.

[0011] The term “column” refers to one or more distillation columns for separating one or more different volatile components. Unless otherwise specified, each column includes a condenser at the top to condense and reflux a portion of the top flow returning to the top of the column, and a reboiler at the bottom to vaporize a portion of the bottom flow and return it to the bottom of the column. The feed into the column may be preheated. The top pressure is the pressure of the top vapor at the column’s vapor outlet. The bottom temperature is the liquid bottom outlet temperature. The top line and bottom line refer to the net lines from column to column downstream of any reflux or reboil. Stripping columns may omit the reboiler at the bottom of the column, but instead may provide heating requirements and the propulsion for separation from fluidizing inert media such as steam. Stripping columns typically feed to an upper tray and remove the main product from the bottom.

[0012] As used herein, the term “separator” means a vessel having an inlet and at least a top vapor outlet and a bottom liquid outlet, and which may also have an aqueous outlet from the boot. A flash drum is a type of separator that may be downstream-communicated with a separator that may operate at higher pressures. As used herein, the term “boiling temperature” means the atmospheric equivalent boiling point (AEBP) calculated from the observed boiling point and distillation pressure using the formulas provided in ASTM D1160 Appendix A7, entitled “Practice for Converting Observed Vapor Temperatures to Atmospheric Equivalent Temperatures.”

[0013] As used herein, the term “True Boiling Point” (TBP) means a test method for determining the boiling point of a substance, which corresponds to ASTM D-2892 for producing standardized quality liquefied gas, distilled fractions, and residues from which analytical data can be obtained, and for determining the yield of the above fractions by both mass and volume, with a temperature versus mass % graph produced using 15 theoretical stages in a column with a reflux ratio of 5:1.

[0014] As used herein, the terms "T5," "T90," or "T95" mean, using ASTM D-86 or TBP, the boiling point of 5 mass percent, 90 mass percent, or 95 mass percent of the sample, respectively.

[0015] As used herein, the term “initial boiling point” (IBP) means the temperature at which the sample begins to boil, using ASTM D-7169, ASTM D-86, or TBP, as applicable.

[0016] As used herein, the term “end point” (EP) means the temperature at which the sample has completely evaporated, as may be determined using ASTM D-7169, ASTM D-86, or TBP.

[0017] As used herein, the term “diesel” means hydrocarbons that boil within the range of IBP at approximately 125°C (257°F) to approximately 175°C (347°F) or T5 at approximately 150°C (302°F) to approximately 200°C (392°F). The “diesel cut point” includes T95 between approximately 343°C (650°F) and approximately 399°C (750°F) using the TBP distillation method, or T90 between 280°C (536°F) and approximately 340°C (644°F) using ASTM D-86. The term “green diesel” means diesel containing hydrocarbons that do not originate from fossil fuels.

[0018] As used herein, the term “jet fuel” means hydrocarbons that boil within the range of T10 from about 190°C (374°F) to about 215°C (419°F) and an endpoint of about 290°C (554°F) to about 310°C (590°F). The term “green jet fuel” means jet fuel containing hydrocarbons that are not of fossil fuel origin.

[0019] As used herein, the terms “main” or “major” mean more than 50%, preferably more than 75%, and more preferably more than 90%. As used herein, the terms “concentrated stream” or “concentrated stream” mean that the concentrated stream coming out of the container has a higher concentration of the component than the feed into the container, and preferably all other streams being withdrawn from the container.

[0020] As used herein, the terms “dilute stream” or “dilute stream” mean that the dilute stream leaving the container has a lower concentration of the component than the supply to the container, and preferably all other streams withdrawn from the container.

[0021] As used herein, the term “concentrated” means more than 50%, preferably more than 75%, and more preferably more than 90%. As used herein, the term “separator” means a vessel having an inlet and at least a top vapor outlet and a bottom liquid outlet, and which may also have an aqueous outlet from the boot. A flash drum is a type of separator that can be downstream-communicated with a separator that can operate at higher pressures. [Brief explanation of the drawing]

[0022] [Figure 1] This shows the block flow. [Modes for carrying out the invention]

[0023] A method for converting methanol to jet fuel is provided. The process may start with methanol derived at least in part from a biological source, and other methanol may be derived from a petroleum source. The methanol is sent to a methanol-olefin reactor to produce a light olefin stream containing mainly ethylene and propylene, but also some impurities including higher molecular weight olefins, alkanes, carbon dioxide, and hydrogen. The light olefin stream is processed in a light olefin recovery process where the dried liquid and vapor olefin products are fractionated and sent to an oligomerization process and then to a hydrogenation section to produce jet fuel and renewable diesel and naphtha streams. It has been found that, in addition to offgas streams and other waste streams, the diesel and naphtha streams can be sent to a steam reformer or an autothermal reformer to produce hydrogen that can be used in the process.

[0024] The disclosed processes and apparatus include the production of liquid fuels from carbon dioxide and hydrogen. The process includes reacting a mixture of carbon dioxide and hydrogen to produce methanol, carbon monoxide, and water. The methanol is contacted with an MTO catalyst to produce an olefin stream. The olefin stream is oligomerized with an oligomerization catalyst to produce an oligomerized olefin stream containing jet fuel, diesel fuel, and alkanes. The oligomerized olefin stream is separated into (1) a liquid fuel stream and (2) an alkane stream. A syngas stream containing carbon oxides and hydrogen is produced by (1) reforming the alkane stream with steam in a steam reformer, an autothermal reformer, or a dry reformer, or (2) partially oxidizing the alkane stream.

[0025] The conversion of methanol to liquid fuel streams such as sustainable aviation fuel (SAF) is highly selective, but the light and heavy by-products of the reaction must be disposed of. One way to improve the overall selectivity of CO2 to liquid fuel streams, such as jet composites (and reduce the carbon intensity) is to recycle heavier hydrocarbons through a route from CO2 to syngas such as reforming (steam reforming, autothermal reforming or dry reforming) or partial oxidation. The resulting syngas can be recycled to a methanol synthesis unit, thereby increasing the jet yield of CO2 to the jet facility.

[0026] Excess oxygen from the hydrolyzer can be introduced into the partial oxidation reactor to convert the by-products to syngas, which can then be used as a feedstock ready for use in a methanol synthesis unit.

[0027] The methane and hydrogen produced by this process can be mixed with CO2 and reacted without using steam. This requires a non-noble metal-based catalyst developed by Linde and BASF. The resulting syngas can be used to produce methanol. It may also be possible to process small amounts of other light hydrocarbons in this way. The advantage of this route is to create syngas without requiring hydrogen from an electrolyzer, which is the most energy-intensive part of the CO2 to jet composite.

[0028] The liquid by-products from the MTJ composite are mixed with oxygen from the hydrolysis unit and reacted over a catalyst to convert the hydrocarbons to CO. CO2 can be co-fed as a raw material to improve the total yield of CO. This process is exothermic when it reaches a sufficiently high temperature.

[0029] There are two alternatives to this approach. (1) Steam reforming at high temperature using CO2 and steam creates a syngas mixture that can be fed directly as a raw material to methanol synthesis. This is an endothermic process and thus requires a significant amount of external heat.

[0030] (2) Autothermal reforming combines both partial oxidation and steam reforming. Oxygen, steam, and CO2 from the hydrolysis unit react on the catalyst to produce a synthesis gas mixture suitable for conversion to methanol. Methane and hydrogen (and possibly ethane) from the MTJ off-gas stream are mixed with CO2 to form a synthesis gas mixture of H2 and CO. This is an endothermic process, but can act as a heat sink from other exothermic processes.

[0031] A third alternative method, dry reforming, can also be used. Methane and carbon dioxide react on a catalyst in an endothermic process to form a synthesis gas mixture of H2 and CO. In the oligomerization process, the flow leaving the depropane unit is sent to a reactor, where it is converted to synthesis gas via steam reforming, partial oxidation, autothermal reforming, or dry reforming. The synthesis gas is then sent to a methanol synthesis unit. When partial oxidation or autothermal reforming is selected to produce synthesis gas, air or oxygen must also be supplied, although additional steam can be extracted from the reactor for use elsewhere in the facility. If steam reforming is selected to produce synthesis gas from ethane / propane, a steam feed (which can be supplied entirely by a methanol-jet process) and an energy input (which can be supplied partially by steam from the methanol-jet process) are also required.

[0032] Liquid fuels can be produced from carbon dioxide and hydrogen through the following process: (a) A step of reacting a mixture of carbon dioxide and hydrogen to produce methanol, carbon monoxide, and water. (b) A step of contacting the methanol with an MTO catalyst to generate an olefin flow, (c) A step of oligomerizing the olefin stream with an oligomerizing catalyst to produce an oligomerized olefin stream containing jet fuel, diesel fuel, and alkanes. (d) A step of separating the oligomerized olefin stream into (1) a liquid fuel stream and (2) an alkane stream, (e) Below, (1) Reforming the alkane stream with steam in a steam reforming reactor, a self-thermal reforming reactor, or a dry reforming reactor, (2) A step of generating a synthesis gas stream containing carbon oxide and hydrogen by partially oxidizing the alkane stream.

[0033] The process of producing liquid fuel from carbon dioxide and hydrogen may include the following steps: (a) A step of reacting a mixture of carbon dioxide and hydrogen to produce a crude methanol stream containing methanol, water, and other contaminants including one or more of hydrogen, CO, CO2, methane, ethanol, and other oxygenated hydrocarbons. (b) A step of purifying the crude methanol stream by distillation to remove light contaminants into the first exhaust gas stream and heavy contaminants and water into the second heavy waste stream, thereby producing a purified methanol stream. (c) A step of contacting the purified methanol stream with an MTO catalyst to produce a crude olefin stream containing ethylene, propylene, butylene, and other contaminants including one or more of hydrogen, CO, CO2, methane, dimethyl ether, ethanol, and other oxygenated hydrocarbons. (d) A step of purifying the crude olefin stream by distillation, transferring the light fraction into a third exhaust gas stream, then absorbing water to remove heavy oxygenated hydrocarbons, extracting water to remove dimethyl ether into a DME (dimethyl ether) recirculation stream, and generating one or more purified olefin streams. (e) A step of using one or more reaction vessels to react one or more of the purified olefin stream with one or more oligomerization catalysts to produce a crude oligomerized olefin stream containing oligomerized olefins having a carbon length of 4 to 24 carbon atoms, and contaminants including one or more of hydrogen, methane, and alkanes lighter than pentane. (f) A step of removing hydrogen and light alkanes from the crude oligomerized olefin stream by fractional distillation, into (1) a fourth exhaust gas stream, (2) a recirculated stream of light oligomerized olefins, and (3) a purified oligomerized olefin stream containing olefins having a carbon length of 12 to 24 carbon atoms. (g) A step of reacting the purified oligomerized olefin stream with hydrogen using a hydrogenation catalyst to saturate the olefin with paraffin and produce a crude jet fuel stream. (h) A step of fractionally distilling the crude jet fuel stream by distillation to remove excess hydrogen and light hydrocarbons into (1) a fifth exhaust gas stream, (2) a sixth exhaust gas stream containing naphtha, (3) a seventh exhaust gas stream containing diesel, and (4) liquid fuel containing jet fuel. (i) Below: (1) In a steam reforming process, a self-heating reforming process, or a dry reforming process, reforming one or more of the exhaust gas streams with steam, or (2) A step of generating a recirculated synthesis gas flow containing carbon oxide and hydrogen by partially oxidizing one or more of the exhaust gas flows, (j) A step of supplying the recirculated synthesis gas stream to the methanol synthesis process of step A.

[0034] One or more exhaust gas streams may also be reacted with oxygen in a partial oxidation reactor to produce a second recirculated synthesis gas stream containing CO and hydrogen. The reaction in step (i) may also be carried out by reacting one or more exhaust gas streams with oxygen and steam in a self-heating reactor to produce a third recirculating synthesis gas stream containing CO and hydrogen.

[0035] The reaction in step (i) may be carried out by reacting the sixth exhaust gas stream with steam in the steam reforming process, by reacting the seventh exhaust gas stream with steam in the steam reforming process, or by partial oxidation, and the resulting recirculated synthesis gas stream is thermally integrated with the fractional distillation process of step (j) to provide some or all of the energy required for distillation.

[0036] Hydrogen for steps (a) and / or (g) may be produced by a water electrolysis unit, and / or oxygen for self-thermal reforming may be produced by a water electrolysis unit. If the reaction in step (i) is carried out by partial oxidation, the oxygen for partial oxidation can be generated by a water electrolysis unit.

[0037] If the reaction in step (i) is carried out in steam in a steam reforming process, the exhaust gas stream(s) supplied to the steam reforming reactor may contain approximately 10% to 50% by weight of propane. The reaction in step (i) may be carried out using a dry reforming process.

[0038] A water electrolysis unit (electrolytic cell) generates hydrogen and oxygen from water. In this disclosure, methanol is supplied to a process that may take place at a different location. The resulting methanol is then contacted with an MTO catalyst to generate an olefin flow. The block flow diagram shown in the figure relates to the most relevant part of the flow scheme 200 that provides the hydrogen required for the process. Off-gas flow 202 is sent from several different towers, including the oligomerization unit and the LORP unit, to the pre-reforming section 205, flow 210 is sent to the steam methane reforming unit 215, and flow 204 is sent to the pre-reforming section 205 and the steam methane reforming unit 215. A portion of the off-gas 220 is used in line 225 to provide fuel to the steam methane reforming unit 225, and line 270 can be separated in the pressure swing adsorption unit 250 to provide hydrogen 260. In addition, the hydrogen-rich off-gas flow 250 is added to the effluent 245 of the water-gas shift unit 235.

[0039] The off-gas from Tower 202 is the net overhead vapor flow from several process units not shown in the diagram, including the demethane unit, depropane unit, flash stripper, and jet fractionation unit. The depropane unit off-gas is the best candidate as feed, while the flash stripper or demethane unit off-gas would be the best candidate to go to the pressure swing adsorption unit. Pre-reforming takes in components in the feed gas that are heavier than methane and breaks them down into methane. This protects the steam methane reforming (SMR) reactor from excessive coking. SMR uses a catalyst at very high temperatures to convert methane and water into synthesis gas (a mixture of carbon monoxide and hydrogen). This is a very endothermic reaction and therefore requires an external fuel flow to provide the heat of reaction.

[0040] The water-gas shift reaction is at a much lower temperature. This shift involves the reaction of CO with additional water to form CO2 and additional hydrogen. It is a mildly exothermic reaction. In the pressure swing adsorption process, the products from the water-gas shift reactor, which have a mixture of hydrogen, CO2, CO, and unconverted methane, are processed. The PSA product gas is high-purity hydrogen, and the tail gas contains CO2, CO, and unconverted methane, which is used as fuel for the SMR reactor.

[0041] If the CO and unconverted methane from the PSA are insufficient to provide the necessary reaction heat in the SMR, additional fuel gas can be supplied from off-gas from the tower. If the hydrogen in the off-gas is concentrated, it will be sent to the PSA for hydrogen recovery. If the hydrogen in the off-gas is not concentrated, it will go directly to the SMR reactor as fuel.

[0042] Specific Embodiments The following will be explained in conjunction with specific embodiments, but it should be understood that this explanation is intended to illustrate the scope of the preceding explanation and the attached claims, and is not intended to limit them.

[0043] A first embodiment of the present invention is a process for supplying hydrogen in a process of producing jet fuel from methanol, comprising sending an off-gas stream to a reforming section to generate a gas stream, sending a hydrogen-rich off-gas stream to combine with the gas stream to provide a hydrogen-enriched gas stream, and purifying the hydrogen-enriched gas stream to generate a hydrogen stream. One embodiment of the present invention is one or all of the prior embodiments to the first embodiment in this paragraph, wherein the off-gas stream is first sent to a pre-reforming reactor in the reforming section and then to a water-gas shift reactor. Another embodiment of the present invention is one or all of the prior embodiments to the first embodiment in this paragraph, wherein, after passing through the water-gas shift reactor, the gas stream is sent to a pressure swing adsorption unit to generate a hydrogen stream. One embodiment of the present invention is one or all of the prior embodiments to the first embodiment in this paragraph, wherein the off-gas flow is fed from at least one tower selected from a demethane unit, a depropane unit, a flash stripper, or a jet fractionation unit, or a combination thereof. One embodiment of the present invention is one or all of the prior embodiments to the first embodiment in this paragraph, wherein the pressure swing adsorption unit processes a mixture of hydrogen, carbon dioxide, carbon monoxide, and unconverted methane. One embodiment of the present invention is one or all of the prior embodiments to the first embodiment in this paragraph, wherein the pressure swing adsorption unit generates a tail gas flow containing carbon dioxide, carbon monoxide, and unconverted methane. One embodiment of the present invention is one or all of the prior embodiments to the first embodiment in this paragraph, wherein a portion of the off-gas flow is sent to a steam methane reforming reactor to supplement a fuel feed. One embodiment of the present invention is one or all of the preceding embodiments to the first embodiment described in this paragraph, wherein the tail gas stream is sent to a steam reforming reactor as fuel gas.One embodiment of the present invention is one or all of the prior embodiments to the first embodiment described in this paragraph, wherein the off-gas flow contains at least 10 mol% hydrogen. One embodiment of the present invention is one or all of the prior embodiments to the first embodiment described in this paragraph, wherein the off-gas flow contains at least 20 mol% hydrogen. One embodiment of the present invention is one or all of the prior embodiments to the first embodiment described in this paragraph, wherein the hydrogen flow contains at least 95 mol% hydrogen. One embodiment of the present invention is one or all of the prior embodiments to the first embodiment described in this paragraph, wherein the hydrogen flow contains at least 98 mol% hydrogen. One embodiment of the present invention is one or all of the prior embodiments described in this paragraph to the first embodiment described in paragraph 1, further comprising a control unit for measuring the hydrogen concentration in the off-gas stream, then sending an off-gas stream containing a hydrogen concentration below a predetermined value to the reforming section as a fuel gas, and when the hydrogen concentration exceeds the predetermined level, sending the off-gas stream to a pressure swing adsorption unit.

Claims

1. A process for supplying hydrogen in a process for producing jet fuel from methanol, Sending a hydrocarbon-rich off-gas stream to a reforming reactor or partial oxidation reactor to generate a gas stream, To provide a hydrogen-enriched gas flow by sending a hydrogen-rich off-gas flow that is combined with the aforementioned gas flow, A process comprising purifying the hydrogen-enriched gas stream to generate a hydrogen stream.

2. The process according to claim 1, wherein the off-gas flow is first sent to a pre-reforming reactor and then to a water-gas shift reactor.

3. The process according to claim 2, wherein after passing through the water-gas shift reactor, the gas stream is sent to a pressure swing adsorption unit to purify the hydrogen-enriched gas stream.

4. The process according to claim 1, wherein the hydrocarbon-rich off-gas stream comes from at least one tower selected from a dealkane tower and a jet fractionation tower, or a combination thereof.

5. The process according to claim 1, wherein the hydrogen-rich off-gas stream comes from at least one tower selected from a demethane tower and a stripper tower, or a combination thereof.

6. The process according to claim 3, wherein the pressure swing adsorption unit processes a mixture of hydrogen, carbon dioxide, carbon monoxide, and unconverted methane to generate the hydrogen stream.

7. The process according to claim 3, wherein the pressure swing adsorption unit generates a tail gas stream containing carbon dioxide, carbon monoxide, and unconverted methane.

8. The process according to claim 1, wherein a portion of the off-gas flow, which is concentrated with the hydrocarbon, is sent to a reformer or partial oxidation reactor to supplement the fuel feed.

9. The process according to claim 7, wherein the tail gas flow is sent as fuel gas to a steam reforming reactor or a partial oxidation reactor.

10. The process according to claim 1, wherein a gas stream containing the hydrocarbon is sent to a water-gas shift reactor after the reforming reactor or the partial oxidation reactor.

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