Process for recovery of oxocarbon gases from dehydrogenation system

Abstract

The present disclosure provides a method for recovering oxocarbon gases from a dehydrogenation reactor, which includes withdrawing an oxocarbon-containing off-gas from a dehydrogenation reactor, the oxocarbon-containing off-gas further comprising hydrogen and one or more C1-C4 hydrocarbons; separating the oxocarbon-containing off-gas into a condensed hydrocarbon-rich liquid stream and a first oxocarbon-rich gas; purifying a portion of the first oxocarbon-rich gas to form a purified hydrogen gas and a second oxocarbon-rich gas; and feeding the first and second oxocarbon-rich gases to a reforming reactor adapted for syngas production. A system for recovering oxocarbon gases from a dehydrogenation reactor is also provided.

Description

PROCESS FOR RECOVERY OF OXOCARBON GASES FROM DEHYDROGENATION SYSTEMTECHNOLOGICAL FIELD

[0001] The present disclosure relates to methods and systems for recovering oxocarbon gases from a dehydrogenation reactor.BACKGROUND

[0002] Fixed bed dehydrogenation units are used for production of olefins and / or alkynes from alkanes and / or olefins. Generally, a fixed bed dehydrogenation unit comprises three or more parallel fixed bed reactors and a catalyst regeneration system. When the fixed bed dehydrogenation unit is in operation, one or more reactors are online (in dehydrogenation mode), and one or more fixed bed reactors are in regeneration mode.

[0003] In a typical fixed bed dehydrogenation process, an aliphatic hydrocarbon (e.g., propane, isobutane, n-butane, 1 -butene, or isopentane) passes through a dehydrogenation catalyst bed and is dehydrogenated to a complementary olefin. The product (dehydrogenated hydrocarbon) of the fixed bed dehydrogenation unit may comprise, for example, propylene, isobutylene, pentene, isoprene, butadiene, or combinations thereof. The dehydrogenation reactions may include reactions (i) and / or (ii) as follows, where "n" in reactions (i) and (ii) is the number of carbon atoms in a hydrocarbon molecule, and "n" is less than 5:(i) CnH2n+2<-^CnH2n+H2, and / or(ii) CnH2n<"^CnH2n-2+H2.

[0004] A fixed bed reactor in dehydrogenation mode first dehydrogenates the hydrocarbon feed for a period of time. Then, the fixed bed reactor is purged with steam. In a subsequent regeneration mode, heated air is blown through to decoke the catalyst disposed in the fixed bed reactor. The reactor is in turn evacuated and the catalyst in the reactor undergoes reduction. After catalyst reduction, the reactor is placed back online for dehydrogenation reaction. The same sequence is repeated automatically for each fixed bed reactor using a programmable logic controller (PLC) to ensure continuous production of the entire dehydrogenation unit.

[0005] The dehydrogenation process produces olefins and hydrogen, as well as light hydrocarbons and oxocarbon gases (e.g., CO and CO2) as byproducts. Theamount of byproducts produced varies as a function of several parameters, such as lifetime of operation or days on stream, reaction selectivity, reactor temperature profiles, and total feed flow. Typically, the light gases formed in the dehydrogenation will go through a low-temperature recovery system, where the majority of C3-C4 light hydrocarbons are reclaimed and recycled back to the main dehydrogenation process. A slip stream is typically redirected to a hydrogen purification unit. Finally, the rejected light off-gases, rich in hydrogen, CO, CO2 and C1-C2 hydrocarbons, are typically sent to a fuel storage system for the application of heat generation in a boiler system, which will ultimately result in release of oxocarbon gases in a flue gas from the boiler. There remains a need in the art to find an efficient way to capture the oxocarbon gases from the dehydrogenation process for reuse.BRIEF SUMMARY

[0006] Example implementations of the present disclosure are directed to processes and systems for recovering oxocarbon gases from a dehydrogenation reactor. In certain embodiments, the present disclosure provides a method that includes withdrawing an oxocarbon-containing off-gas from a dehydrogenation reactor, separating the oxocarbon-containing off-gas into a condensed hydrocarbon- rich liquid stream, a first oxocarbon-rich gas, and a hydrogen-rich gas, purifying the hydrogen-rich gas to form a purified hydrogen gas and a second oxocarbon-rich gas, and thereafter feeding the first and second oxocarbon-rich gases to a reforming reactor adapted for syngas production. In this manner, oxocarbon gases are efficiently recovered from the dehydrogenation process and used for syngas production, which avoids release of the oxocarbons into the environment, reduces natural gas consumption, and reduces reforming process energy intensity.

[0007] Dehydrogenation systems according to the present disclosure typically include a dehydrogenation reactor comprising a catalyst bed in fluid communication with a hydrocarbon feed source, such as propane, isobutane, pentane, isopentane, n- butane, 1 -butene, or combinations thereof; a purge gas source in fluid communication with the reactor to remove remaining hydrocarbon, a regeneration air source in fluid communication with the dehydrogenation reactor to regenerate the catalyst and remove remaining impurities; and a reducing gas source in fluid communication with the dehydrogenation reactor to reduce the catalyst.

[0008] The present disclosure includes, without limitation, the following embodiments.

[0009] Embodiment 1 : A process for recovering oxocarbon gases from a dehydrogenation reactor, comprising: withdrawing an oxocarbon-containing off-gas from a dehydrogenation reactor, the oxocarbon-containing off-gas further comprising hydrogen and one or more C1-C4 hydrocarbons; separating the oxocarbon-containing off-gas into a condensed hydrocarbon-rich liquid stream and a first oxocarbon-rich gas; purifying a portion of the first oxocarbon-rich gas to form a purified hydrogen gas and a second oxocarbon-rich gas; and feeding the first and second oxocarbon-rich gases to a reforming reactor adapted for syngas production.

[0010] Embodiment 2: The process of Embodiment 1, further comprising adjusting the temperature and / or pressure of the first and second oxocarbon-rich gases prior to the feeding step, optionally after combining the first and second oxocarbon- rich gases.

[0011] Embodiment 3: The process of Embodiment 1 or 2, further comprising feeding a methane-containing gas and steam to the reforming reactor, optionally wherein the first and second oxocarbon-rich gases comprise about 20% by weight or less of the total feed to the reforming reactor, based on the total weight of all gases fed to the reforming reactor including steam, methane-containing gas, and the oxocarbon- rich gases.

[0012] Embodiment 4: The process of any one of Embodiments 1 to 3, wherein the reforming reactor is a catalytic steam reforming reactor or an autothermal reforming reactor.

[0013] Embodiment 5: The process of any one of Embodiments 1 to 4, wherein the purifying comprises treating a portion of the first oxocarbon-rich gas using pressure swing adsorption.

[0014] Embodiment 6: The process of any one of Embodiments 1 to 5, wherein the dehydrogenation reactor comprises a fixed bed dehydrogenation unit, a compression unit, and a recovery unit; wherein a total content of oxocarbons and Cl- C3 hydrocarbons within the oxocarbon-containing off-gas from the dehydrogenation reactor is about 25% or less by weight, based on the total weight of the oxocarbon- containing off-gas, such as about 10% or less or about 5% or less; and / or wherein thefirst and second oxocarbon-rich gases further comprise one or more C1-C3 hydrocarbons.

[0015] Embodiment 7: The process of any one of Embodiments 1 to 6, wherein the separating comprises treatment of the oxocarb on-containing off-gas in a series of heat exchangers including at least one heat exchanger using a refrigerant as heat transfer medium.

[0016] Embodiment 8: A system for recovering oxocarbon gases from a dehydrogenation reactor, comprising: a dehydrogenation reactor comprising a catalyst bed in fluid communication with a hydrocarbon feed source, the dehydrogenation reactor adapted to produce an oxocarbon-containing off-gas effluent, the oxocarbon- containing off-gas effluent further comprising hydrogen and one or more C1-C4 hydrocarbons; a low temperature separation system in fluid communication with the oxocarbon-containing off-gas effluent and adapted to produce a condensed hydrocarbon-rich liquid stream and a first oxocarbon-rich gas; a hydrogen purification system in fluid communication with a portion of the first oxocarbon-rich gas and adapted to produce a purified hydrogen gas and a second oxocarbon-rich gas; and a reforming reactor adapted to produce syngas and in fluid communication with the first and second oxocarbon-rich gases.

[0017] Embodiment 9: The system of Embodiment 8, further comprising a gas expander vessel upstream of the reforming reactor and in fluid communication with both the first and second oxocarbon-rich gases and adapted to reduce gas pressure, the effluent from the gas expander vessel in fluid communication with the reforming reactor.

[0018] Embodiment 10: The system of Embodiment 8 or 9, wherein the reforming reactor is in fluid communication with a methane-containing feed gas and steam.

[0019] Embodiment 11 : The system of any one of Embodiments 8 to 10, wherein the reforming reactor is a catalytic steam reforming reactor or an autothermal reforming reactor.

[0020] Embodiment 12: The system of any one of Embodiments 8 to 11, wherein the hydrogen purification system comprises one or more pressure swing adsorption vessels containing an adsorbent, such as a zeolite adsorbent.

[0021] Embodiment 13: The system of any one of Embodiments 8 to 12, wherein the dehydrogenation reactor comprises a fixed bed dehydrogenation unit, acompression unit, and a recovery unit; wherein a total content of oxocarbons and Cl- C3 hydrocarbons within the oxocarbon-containing off-gas effluent from the dehydrogenation reactor is about 25% or less by weight, based on the total weight of the oxocarbon-containing off-gas effluent, such as about 10% or less or about 5% or less; and / or wherein the first and second oxocarbon-rich gases further comprise one or more C1-C3 hydrocarbons.

[0022] Embodiment 14: The system of any one of Embodiments 8 to 13, wherein the low temperature separation system comprises a series of heat exchangers including at least one heat exchanger using a refrigerant as heat transfer medium.

[0023] Embodiment 15: Use of one or more oxocarbon-rich gases separated from an oxocarbon-containing off-gas effluent from a dehydrogenation reactor as a feed stream for a reforming reactor.

[0024] These and other features, aspects, and advantages of the present disclosure will be apparent from a reading of the following detailed description together with the accompanying figures, which are briefly described below. The present disclosure includes any combination of two, three, four or more features or elements set forth in this disclosure, regardless of whether such features or elements are expressly combined or otherwise recited in a specific example implementation described herein. This disclosure is intended to be read holistically such that any separable features or elements of the disclosure, in any of its aspects and example implementations, should be viewed as combinable, unless the context of the disclosure clearly dictates otherwise.

[0025] It will therefore be appreciated that this Brief Summary is provided merely for purposes of summarizing some example implementations so as to provide a basic understanding of some aspects of the disclosure. Accordingly, it will be appreciated that the above described example implementations are merely examples and should not be construed to narrow the scope or spirit of the disclosure in any way. Other example implementations, aspects and advantages will become apparent from the following detailed description taken in conjunction with the accompanying figures which illustrate, by way of example, the principles of some described example implementations.BRIEF DESCRIPTION OF THE FIGURES

[0026] Having thus described aspects of the disclosure in the foregoing general terms, reference will now be made to the accompanying figures, which are not necessarily drawn to scale, and wherein:

[0027] FIG. l is a schematic representation of a dehydrogenation reactor system according to an example implementation of the present disclosure;

[0028] FIG. 2 is a schematic representation of a system for recovering oxocarbon gases from a dehydrogenation reactor according to an example implementation of the present disclosure;

[0029] FIG. 3 graphically illustrates an example composition of an off-gas stream received by the low temperature recovery unit of the process of FIG. 2;

[0030] FIG. 4 graphically illustrates an average quantification of an example composition of an off-gas stream received by the low temperature recovery unit of the process of FIG. 2; and

[0031] FIG. 5 graphically illustrates an example of the net CO2 recovery capacity resulting from recovery of the light hydrocarbon gases and oxocarbon gases from the low temperature recovery unit of the process of FIG. 2.DETAILED DESCRIPTION

[0032] Some implementations of the present disclosure will now be described more fully hereinafter with reference to the accompanying figures, in which some, but not all implementations of the disclosure are shown. Indeed, various implementations of the disclosure may be embodied in many different forms and should not be construed as limited to the implementations set forth herein; rather, these example implementations are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals refer to like elements throughout.

[0033] Unless specified otherwise or clear from context, references to first, second or the like should not be construed to imply a particular order. A feature described as being above another feature (unless specified otherwise or clear from context) may instead be below, and vice versa; and similarly, features described as being to the left of another feature else may instead be to the right, and vice versa. Also, while reference may be made herein to quantitative measures, values, geometric relationships or the like, unless otherwise stated, any one or more if not all of thesemay be absolute or approximate to account for acceptable variations that may occur, such as those due to engineering tolerances or the like.

[0034] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., ranges of “up to 25 wt.%, or, more specifically, 5 wt.% to 20 wt.%”, are inclusive of the endpoints and all intermediate values of the ranges of “5 wt.% to 25 wt.%,” etc.). “Combination” is inclusive of blends, mixtures, alloys, reaction products, and the like.

[0035] The term “about” is defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment, the terms are defined to be within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.

[0036] As used herein, unless specified otherwise or clear from context, the “or” of a set of operands is the “inclusive or” and thereby true if and only if one or more of the operands is true, as opposed to the “exclusive or” which is false when all of the operands are true. Thus, for example, “[A] or [B]” is true if [A] is true, or if [B] is true, or if both [A] and [B] are true. Further, the articles “a” and “an” mean “one or more,” unless specified otherwise or clear from context to be directed to a singular form.

[0037] The terms “wt.%”, “vol.%”, or “mol.%” refer to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume of material, or total moles, that includes the component. In a non-limiting example, 10 grams of component in 100 grams of the material is 10 wt.% of component.

[0038] The present disclosure relates to a method and system for recovering oxocarbon gases from a dehydrogenation process. Example dehydrogenation processes include CATOFIN® dehydrogenation processes and ODH-E (Oxidative Dehydrogenation of Ethane) processes, such as EDHOX™ technology available from Linde Engineering, as well as other redox oxidative dehydrogenation (redox-ODH) reactions, such as those used for production of styrene as set forth in Zhu, X., Gao, Y, Wang, X. et al. “A Tailored Multi-Functional Catalyst for Ultra-Efficient Styrene Production Under a Cyclic Redox Scheme.” Nat Commun 12, 1329 (2021). For purposes of illustration only, use of the system and method of the disclosure isdescribed herein in the context of a dehydrogenation reaction used to convert alkanes to alkenes.Dehydrogenation Process and System

[0039] In one embodiment, the present disclosure relates to recovery of oxocarbon gases from a dehydrogenation process used to convert alkanes to alkenes over, for example, a chromia-alumina catalyst. As used herein, “oxocarbon gases” refers to gaseous compounds consisting of carbon and oxygen atoms, including carbon monoxide and carbon dioxide.

[0040] The dehydrogenation process typically takes place in fixed bed reactors that operate on a cyclic basis to permit continuous flow of the major process streams. In one cycle, hydrocarbon vapors are dehydrogenated and the reactor is then purged with steam and blown with air to burn off coke. These steps are followed by an evacuation and reduction and then another cycle starts.

[0041] The catalyzed conversion of alkanes to alkenes typically produces byproducts, including light hydrocarbons, such as C1-C4 hydrocarbons, and oxocarbons, as a result of hydrocarbon cracking, and these byproducts become entrapped in the solid catalyst bed. The purging / regeneration steps of the dehydrogenation process produce an off-gas containing these byproducts.

[0042] In a typical fixed bed dehydrogenation process, an aliphatic hydrocarbon (e.g., propane, isobutane, n-butane, 1 -butene, or isopentane) passes through a dehydrogenation catalyst bed and is dehydrogenated to a complementary olefin. The olefin is then flushed from the catalyst bed, the catalyst is regenerated and reduced, and the cycle is repeated. The product (dehydrogenated hydrocarbon) of the fixed bed dehydrogenation unit may comprise, for example, propylene, isobutylene, pentene, isoprene, butadiene, or combinations thereof.

[0043] This process can be run as an adiabatic, cyclic process. Each cycle includes a catalyst reduction step and a dehydrogenation step, and typically further includes a step to purge the remaining hydrocarbon from the reactor, and finally a regeneration step with air. Following this, the cycle begins again with the catalyst reduction step.

[0044] The reactors in dehydrogenation processes operate under vacuum during various steps of the reaction process, such as during dehydrogenation and duringcatalyst reduction. The final reactor pressure after evacuation is typically about 0.6 bar or less, such as about 0.2 bar to about 0.6 bar (Absolute).

[0045] With reference to FIG. 1, a process schematic diagram for an example implementation of a fixed bed dehydrogenation unit 100 is shown, with different reactors at different points in the process cycle. Note that the exemplified dehydrogenation embodiment is merely illustrative of the type of reaction system suitable for use in the present disclosure and is not limiting. The fixed bed dehydrogenation unit 100 may include a fixed bed reactor 101 in purge mode, a fixed bed reactor 102 in dehydrogenation mode, and a fixed bed reactor 103 in regeneration mode. Each of the fixed bed reactors comprises a catalyst bed. The catalyst may include Cr / Al (chromium oxide over alumina), Sn — Pt / Al (tin-platinum over alumina), or combinations thereof.

[0046] The inlet of fixed bed reactor 102 in dehydrogenation mode may be connected to a heater 110 that is configured to heat a hydrocarbon feed to a reaction temperature, and the outlet of fixed bed reactor 102 in dehydrogenation mode may be connected to a heat exchanger 108 to cool down the effluent from fixed bed reactor 102 in dehydrogenation mode. In the illustrated embodiment, the combined hydrocarbon stream 13 from a hydrocarbon feed stream 11 and a recycled hydrocarbon stream 12 may be vaporized and heated to a reaction temperature by heater 110. Note that recycled hydrocarbon 12 stream may originate from various sources other than shown in the illustrated embodiment, such as downstream processing units. The reaction temperature is typically about 540 °C to about 750 °C. The reaction pressure may be in a range of about 0.2 bara to about 1.2 bara, such as about 0.2 bara to about 0.6 bara.

[0047] Fixed bed dehydrogenation unit 100 may further include a regeneration air system comprising an air compressor 104 configured to blow air into fixed bed reactor 103 in regeneration mode, a regeneration air heater 105 configured to heat the air from air compressor 104, a fuel injector 106 configured to inject fuel gas into fixed bed reactor 103 in regeneration mode, and a heat exchanger 107 configured to cool down the effluents from fixed bed reactor 103 in regeneration mode and fixed bed reactor 101 in purge mode. The effluent from the reactor in purge mode may be configured to be cooled in either of heat exchanger 107 or 108 with a suitable condensate recovery system. Fuel injector 106 may be disposed between aircompressor 104 and regeneration air heater 105 as shown or placed downstream from the regeneration air heater. A stream 16 leaving fixed bed reactor 103 in regeneration mode may be used for generating steam via heat exchanger 107. The regenerating conditions can include a regenerating pressure of about 0.1 bar to about 10 bar. The regenerating conditions can include a regenerating period that may be in a range of about 7 minutes to about 18 minutes.

[0048] Fixed bed dehydrogenation unit 100 may further include a compression and recovery system 109 to recover and purify a dehydrogenated hydrocarbon obtained from fixed bed reactor 102 in dehydrogenation mode. Specifically, effluent stream 14 from fixed bed reactor 102 in dehydrogenation mode may be cooled, recovered, and purified through compression and recovery system 109. Purified dehydrogenated hydrocarbon may flow in stream 17. In some embodiments, recovered unreacted hydrocarbon may be recycled back to combined hydrocarbon stream 13 via recycled hydrocarbon stream 12.

[0049] Fixed bed dehydrogenation unit 100 may further include a purge gas source 20 (e.g., steam) in fluid communication with each reactor for use in the purge step, and a reducing gas source 22 (e.g., hydrogen) in fluid communication with each reactor to reduce the catalyst.

[0050] Process sequence can be controlled, for example, using programmable logic controllers. See, for example, the programmable logic controllers set forth in US Pat. No. 11,370,729 to Ansari et al. and US Pat. Publ. No. 2022 / 0055002 to Bodas et al, which are incorporated by reference herein in their entirety.Oxocarbon Recovery System

[0051] According to the present disclosure, an oxocarbon recovery system is combined with a dehydrogenation reactor system for recovery of oxocarbons for use in syngas production. An example implementation of an oxocarbon recovery system 200 is shown in FIG. 2. For the sake of simplicity, the dehydrogenation reactor system 202 is not shown with all input streams, but can be, for example, fixed bed dehydrogenation unit 100 shown in FIG. 1. Dehydrogenation reactor system 202 produces a primary product stream 204 comprising the desired product along with some impurities, which is subjected to a compression and recovery system as shown in FIG. 1. In certain embodiments, this primary product stream 204 has a flow rate of about 100-150 t / h per reactor / dehydrogenation unit.

[0052] Dehydrogenation reactor system 202, which includes a compression and recovery system, also produces an off-gas stream 206 rich in light hydrocarbons and oxocarbon gases. The total content of oxocarbons and C1-C3 hydrocarbons within the oxocarbon-containing off-gas stream 206 from dehydrogenation reactor system 202 is typically about 25 wt.% or less (e.g., about 5 wt.% to about 25 wt.%), based on the total weight of the oxocarbon-containing off-gas stream. An example composition of off-gas stream 206 is about 5 wt.% to about 15 wt.% hydrogen, about 1 wt.% to about 6 wt.% CO2, about 1 wt.% to about 8 wt.% CO, about 5 wt.% to about 50 wt.% C1-C2 hydrocarbons, and about 20 wt.% to about 40 wt.% C3-C4 hydrocarbons. In certain embodiments, this off-gas stream 206 has a flow rate of about 15-30 t / h per reactor / dehydrogenation unit.

[0053] As shown in FIG. 2, off-gas stream 206 is directed to a low temperature recovery system (LTRS) 208, which typically includes treatment of the off-gas stream in a series of heat exchangers including at least one heat exchanger using a refrigerant as heat transfer medium. Low temperature recovery system 208 is adapted to separate light gases (e.g., hydrogen, oxocarbons, and C1-C2 hydrocarbons) from condensable gases (e.g., C3-C4 hydrocarbons). Low temperature recovery system 208 is designed to recover a C4-rich liquid stream 212 for recycle back to the dehydrogenation reactor system 202, which can include recycling back to the compression and recovery train of the dehydrogenation reactor system. Alternatively, the low temperature recovery system 208 is designed to recover C4-rich liquid stream 212 for further processing in downstream units.

[0054] The system of the present disclosure is also designed to recover hydrogen from the light gases remaining after removal of C4-rich liquid stream 212, such as by removing a slip stream 210 of the light gases and producing purified hydrogen, such as by pressure swing adsorption, in a hydrogen purification system 218, to produce a purified hydrogen stream 220 and a first oxocarbon-rich stream 216, which also typically contains C1-C3 hydrocarbons. Although not shown, a portion of slip stream 210 can also be recycled back to the dehydrogenation reactor system 202 for use as a reducing gas. The remainder of the light gases are recovered from the low temperature recovery system 208 as a second oxocarbon-rich stream 214, which also typically contains C1-C3 hydrocarbons and hydrogen.

[0055] The pressure swing adsorption (PSA) process used for hydrogen purification is understood to refer to use of the phenomenon that under high pressure, gases tend to be trapped onto solid surfaces, such as zeolite adsorbent materials. Higher pressure leads to greater gas adsorption. When the pressure is dropped, the gas is released or desorbed. Typical pressure swing adsorption systems comprises two vessels in parallel such that one vessel can function in adsorption mode while the other vessel is regenerated. Multiple stages of vessels arranged in parallel can also be used.

[0056] At least a portion of second oxocarbon-rich stream 214 and at least a portion of first oxocarbon-rich stream 216 are in fluid communication with an optional temperature / pressure regulation and storage system 222, which can include, for example a gas expander vessel to reduce gas pressure and / or a heat exchanger to raise the temperature of the oxocarbon-rich stream. The effluent 224 from the optional temperature / pressure regulation and storage system 222 is ultimately fed to a reforming reactor 226 (which may comprise a steam reformer) adapted to produce a syngas stream 228.

[0057] Although low temperature recovery system 208 may vary, in one embodiment, the system has two parts. In the first part, the off-gas stream 206 is typically cooled to a temperature of about 5 °C to about 10 °C in a heat exchanger using a refrigerant (e.g., a C3 hydrocarbon refrigerant) as the cooling medium. As temperature is decreased, part of the off-gas is liquefied and the condensed liquid (primarily C4 hydrocarbons) is separated in a gas-liquid separator to produce the C4- rich liquid stream 212.

[0058] The second part of the system treats the gas stream from the gas-liquid separator and typically includes at least one dryer to remove moisture followed by splitting the gas stream into slip stream 210 and second oxocarbon-rich stream 214. In certain embodiments, slip stream 210 can be compressed to a pressure suitable for the PSA process and directed to the hydrogen purification system 218. In an alternative embodiment, the gaseous stream remaining after removal of the C4-rich liquid stream 212 is directed to one or more turbo-expanders. In such an embodiment, slip stream 210 can be taken out upstream at a higher pressure while the majority of the oxocarbon-rich gas is taken out at a lower pressure downstream after expansion.The use of turbo-expander(s) can be beneficial because of the production of work that can be used to drive a compressor or generator.

[0059] The optional temperature / pressure regulation and storage system 222 is needed in certain embodiments to regulate the temperature and / or pressure of the oxocarbon-rich gases in preparation for injection into reforming reactor 226. For example, the oxocarbon-rich gases can have a temperature in the range of about 15 °C to about 40 °C, whereas the reforming reactor 226 may operate at a temperature in the range of about 300 °C to 500 °C. Accordingly, in certain embodiments, the process of the invention can include increasing the temperature of the oxocarbon-rich gases from, for example, a range of about 15 °C to about 40 °C, to a range of about 150 °C to 500 °C.

[0060] The type of reforming reactor 226 is not limiting, and can include catalytic steam reforming reactors and autothermal reforming reactors. In certain embodiments, reforming reactor 226 is a catalytic steam reforming reactor, such as packed bed steam reformers that include a catalyst bed (e.g., a nickel catalyst) wherein steam reacts with hydrocarbons, such as C1-C4 hydrocarbons, to produce syngas, which is understood to refer to a mixture of hydrogen and carbon monoxide in various ratios. Accordingly, in certain embodiments, in addition to oxocarbon-rich effluent 224, reforming reactor 226 will also receive a methane feed stream and a steam feed stream. The produced syngas can be used in downstream processes that require syngas as a feedstock, including methanol production.

[0061] First and second oxocarbon-rich gas streams 216 and 214 would typically constitute only a minor component of the total feed to reforming rector 226, which means introduction of these streams to an existing reformer in operation should not cause significant process control challenges. In certain embodiments, first and second oxocarbon-rich gas streams 216 and 214, will comprise about 20 wt.% or less of the total feed to the reforming reactor 226, or about 15 wt.% or less (e.g., about 1 wt.% to about 20 wt.% or about 10 wt.% to about 15 wt.%), based on the total weight of all gases fed to the reforming reactor including steam, methane-containing gas, and the oxocarbon-rich gases.EXPERIMENTAL

[0062] An existing dehydrogenation plant was monitored over a two-year period to determine the composition of an off-gas stream received into a low temperature recovery system (LTRS). FIG. 3 graphically illustrates the variance in weight percent of C1-C3 light hydrocarbons and oxocarbon gases in this composition over the two- year period. These components are recovered in the system described in the present disclosure for feed to the reforming process. For this existing dehydrogenation plant, it can be expected that the portion of off-gas stream fed to the reforming reactor accounts for about 15 wt.% of the total feed to the LTRS. FIG. 4 graphically illustrates the variance of an example composition of an off-gas stream received by the LTRS from the existing dehydrogenation plant in terms of flow rate over the same time period. FIG. 5 displays the net CO2 recovery capacity resulting from injecting the light hydrocarbon and oxocarbon gases originating from the LTRS to a reformer. The figure also shows the overall flow rate of the off-gas received into the LTRS. Based on the analysis of the existing dehydrogenation plant, an average rate of 10 T / hr of CO2 per plant could be captured and used for syngas production.

[0063] In general, the invention may alternately comprise, consist of, or consist essentially of, any appropriate components herein disclosed. The invention may additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any components, materials, ingredients, adjuvants or species used in the prior art compositions or that are otherwise not necessary to the achievement of the function and / or objectives of the present invention.

[0064] Many modifications and other implementations of the disclosure will come to mind to one skilled in the art to which this disclosure pertains having the benefit of the teachings presented in the foregoing descriptions and the associated figures. Therefore, it is to be understood that the disclosure is not to be limited to the specific implementations disclosed herein and that modifications and other implementations are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

CLAIMS:

1. A process for recovering oxocarbon gases from a dehydrogenation reactor, comprising:(1) withdrawing an oxocarbon-containing off-gas from a dehydrogenation reactor, the oxocarbon-containing off-gas further comprising hydrogen and one or more C1-C4 hydrocarbons;(2) separating the oxocarbon-containing off-gas into a condensed hydrocarbon-rich liquid stream and a first oxocarbon-rich gas;(3) purifying a portion of the first oxocarbon-rich gas to form a purified hydrogen gas and a second oxocarbon-rich gas; and(4) feeding the first and second oxocarbon-rich gases to a reforming reactor adapted for syngas production.

2. The process of claim 1, further comprising adjusting the temperature and / or pressure of the first and second oxocarbon-rich gases prior to the feeding step, optionally after combining the first and second oxocarbon-rich gases.

3. The process of claim 1, further comprising feeding a methane-containing gas and steam to the reforming reactor, optionally wherein the first and second oxocarbon-rich gases comprise about 20% by weight or less of the total feed to the reforming reactor, based on the total weight of all gases fed to the reforming reactor including steam, methane-containing gas, and the oxocarbon-rich gases.

4. The process of claim 1, wherein the reforming reactor is a catalytic steam reforming reactor or an autothermal reforming reactor.

5. The process of claim 1, wherein the purifying comprises treating a portion of the first oxocarbon-rich gas using pressure swing adsorption.

6. The process of claim 1, wherein the dehydrogenation reactor comprises a fixed bed dehydrogenation unit, a compression unit, and a recovery unit; wherein a total content of oxocarbons and C1-C3 hydrocarbons within the oxocarbon- containing off-gas from the dehydrogenation reactor is about 25% or less by weight, based on the total weight of the oxocarbon-containing off-gas; and / or wherein the first and second oxocarbon-rich gases further comprise one or more C1-C3 hydrocarbons.

7. The process of claim 1, wherein the separating comprises treatment of the oxocarbon-containing off-gas in a series of heat exchangers including at least one heat exchanger using a refrigerant as heat transfer medium.

8. A system for recovering oxocarbon gases from a dehydrogenation reactor, comprising:(1) a dehydrogenation reactor comprising a catalyst bed in fluid communication with a hydrocarbon feed source, the dehydrogenation reactor adapted to produce an oxocarbon-containing off-gas effluent, the oxocarbon-containing off-gas effluent further comprising hydrogen and one or more C1-C4 hydrocarbons;(2) a low temperature separation system in fluid communication with the oxocarbon-containing off-gas effluent and adapted to produce a condensed hydrocarbon-rich liquid stream and a first oxocarbon-rich gas;(3) a hydrogen purification system in fluid communication with a portion of the first oxocarbon-rich gas and adapted to produce a purified hydrogen gas and a second oxocarbon-rich gas; and(4) a reforming reactor adapted to produce syngas and in fluid communication with the first and second oxocarbon-rich gases.

9. The system of claim 8, further comprising a gas expander vessel upstream of the reforming reactor and in fluid communication with both the first and second oxocarbon-rich gases and adapted to reduce gas pressure, the effluent from the gas expander vessel being in fluid communication with the reforming reactor.

10. The system of claim 8, wherein the reforming reactor is in fluid communication with a methane-containing feed gas and steam.

11. The system of claim 8, wherein the reforming reactor is a catalytic steam reforming reactor or an autothermal reforming reactor.

12. The system of claim 8, wherein the hydrogen purification system comprises one or more pressure swing adsorption vessels containing an adsorbent, such as a zeolite adsorbent.

13. The system of claim 8, wherein the dehydrogenation reactor comprises a fixed bed dehydrogenation unit, a compression unit, and a recovery unit; wherein a total content of oxocarbons and C1-C3 hydrocarbons within the oxocarbon - containing off-gas effluent from the dehydrogenation reactor is about 25% or less by weight, based on the total weight of the oxocarbon-containing off-gas effluent; and / or wherein the first and second oxocarbon-rich gases further comprise one or more C1-C3 hydrocarbons.

14. The system of claim 8, wherein the low temperature separation system comprises a series of heat exchangers including at least one heat exchanger using a refrigerant as heat transfer medium.

15. Use of one or more oxocarbon-rich gases separated from an oxocarbon- containing off-gas effluent from a dehydrogenation reactor as a feed stream for a reforming reactor.

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