Production of liquefied petroleum gas (LPG) hydrocarbons from carbon dioxide-containing feedstocks

Abstract

Disclosed are routes for producing liquefied petroleum gas (LPG) products including propane and / or butane, and potentially renewable products with non-petroleum derived carbon. In particular, gaseous feed mixtures including CO2 in combination with CH4 and / or H2 are converted by reforming and / or reverse water-gas shift (RWGS) reactions in combination with further LPG synthesis. Preferred gaseous feed mixtures include biogas, or mixtures of CO2 and H2 that are not easily upgraded using conventional processes. The catalysts described herein have high activity to catalyze RWGS simultaneously with CH4 reforming (including dry reforming). These attributes improve management of CO2 input to the disclosed processes, especially those processes that utilize recycle operations to increase total CO2 conversion. Optionally, the economics of small scale operations can be improved by using electrically heated reforming reactors in the initial or early reforming or RWGS stages.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims U.S. Patent Application No. 17 / 470,195, filed September 9, 2021, which is incorporated by reference in its entirety.

[0002] An embodiment of the invention relates to a process and associated catalysts for producing products comprising propane and / or butane, e.g., products having compositions approximating liquefied petroleum gas (LPG), from a gaseous feed mixture comprising carbon dioxide (CO2). Exemplary processes utilize at least one or both of (i) reforming and / or reverse water-gas shift (RWGS) reactions in combination with (ii) LPG synthesis. Other embodiments relate more broadly to the conversion of synthesis gas, optionally comprising CO2, to LPG. [Background technology]

[0003] The search for alternatives to crude oil as the traditional carbon source for hydrocarbon products continues and is increasingly driven by a number of factors. These include declining oil reserves, projected increases in energy demand, and growing concerns over greenhouse gas (GHG) emissions from non-renewable carbon sources. In terms of replacing the carbon content of hydrocarbon products with non-petroleum derived carbon, the hydrocarbon products of greatest industrial importance and interest include transportation and heating fuels and precursors to specialty chemicals. The specific hydrocarbons propane and / or butane are present in many of these products, a common example being liquefied petroleum gas (LPG).

[0004] Carbon dioxide (CO2) is a major source of GHG emissions and is found in gases produced from combustion, both in engines, power generation, and commercial and residential heating. Numerous small- and large-scale processes generally produce waste gases containing CO2 derived from the crude oil-based hydrocarbon products mentioned above. CO2 may be obtained as a component of gaseous mixtures containing hydrogen (H2) and / or methane (CH4), which may or may not be a combustion product. Examples of such mixtures include industrial off-gases obtained by reforming CH4 to produce H2, where CO2 is used as a reactant (in the case of dry reforming) and / or produced by the water-gas shift reaction. In addition, while natural gas sources are primarily methane, they may also contain significant amounts of CO2 extracted from this resource. Other gaseous mixtures of CO2 and CH4 include, for example, (i) biogas obtained from anaerobic bacterial digestion of biowaste or wastewater treatment, (ii) gaseous products of biomass conversion (e.g., gasification, pyrolysis or hydropyrolysis of biomass in the case of supercritical water gasification of biomass), (iii) waste landfill gas, or (iv) gaseous products of the electrochemical reduction of carbon dioxide, in certain cases where the latter component in these mixtures is a renewable resource.

[0005] Methane has been the focus of many possible synthesis routes, given the abundance of natural gas reserves and oil-related gas. Currently, natural gas is the most underutilized fossil resource, and frequent reburning (flaring) and transporting it to large-scale processing facilities is an uneconomic proposition, especially when "stagnant" natural gas and other resources are too isolated or in short supply. In addition, hydraulic fracturing techniques have lowered the price of natural gas in the United States and the supply of this resource is increasing globally. Moreover, methane is one of the most common products that can be produced from renewable resources, especially those obtained from the processing of biological waste and biomass, as well as the other resources mentioned above. Thus, the conversion of methane, especially methane obtained from renewable carbon sources such as biowaste, has become an area of ​​great interest for development on an industrial scale with favorable economics.

[0006] The main commercial process for converting methane to fuel involves a first conversion step to produce synthesis gas (syngas) followed by a second downflow Fischer-Tropsch (FT) synthesis step. With respect to the above-mentioned first conversion step upstream of the FT, known processes for producing synthesis gas from methane include partial oxidation reforming and autothermal reforming (ATR), which are based on the exothermic oxidation of methane with oxygen. Conversely, steam methane reforming (SMR) uses steam as the oxidant and therefore has significantly different thermodynamics, since not only does the generation of the steam itself require an energy investment, but the reaction of methane with water absorbs heat. Recently, it has also been proposed to use carbon dioxide (CO2) as an oxidant for methane, which would result in the formation of the desired synthesis gas by the reaction of the most oxidized form of carbon with the most reduced form of carbon. CH4+CO2→2CO+2H2

[0007] This reaction is called "dry reforming" of methane, and since it is highly endothermic, methane dry reforming is less thermodynamically favorable than ATR or SMR. However, the stoichiometric consumption of one mole of carbon dioxide per mole of methane may reduce the overall carbon footprint of liquid fuel production and result in a "greener" consumption of methane. When reforming higher hydrocarbons (e.g., C2-C6 paraffins), for example, for the purpose of producing hydrogen (e.g., for refining processes), an increased CO2 consumption per mole of feedstock is desirable. In both cases, the thermodynamic barrier remains the main challenge, which is related to the fact that CO2 is fully oxidized and is very stable, so a large amount of energy is required to activate it as an oxidizing agent. In view of this, many catalytic systems have been studied to overcome the activation energy obstacle of methane dry reforming, which are summarized, for example, in a review by Lavoie (Frontiers in Chemistry (Nov.2014), Vol.2(81):1-17). In terms of catalytic approaches to carry out this reaction, heterogeneous catalytic systems have been identified as being the most common.

[0008] Nickel-based catalysts have shown efficacy in lowering the activation energy of the dry reforming reactions mentioned above, but Lavoie also reported high carbon deposition (coking) rates for these catalysts. The undesirable conversion of methane to elemental carbon can proceed via methane decomposition (CH4 → C + 2H2) or the Boudouard reaction (2CO → C + CO2) at the reaction temperatures typically required for dry reforming of methane. Recently, other types of catalysts, including catalysts containing noble metals on ceria-containing supports, have been described in US Patent No. 10,738,247, US Patent No. 10,906,808, US Patent No. 2020 / 0087144, and US Patent No. 2020 / 0087576, belonging to the Gas Technology Institute (Des Plaines, Illinois). The catalysts show high activity and stability (low coking rates) in reforming based on CO2 alone or in combination with CO2 and steam. In addition, these catalysts exhibit high tolerance to sulfur-containing contaminants (e.g., H2S), which can further improve the economics of the process in that it reduces costs normally associated with pre-treatment of the feedstock.

[0009] In the second step, which involves FT conversion, the synthesis gas, which contains a mixture of hydrogen and carbon monoxide (CO), undergoes successive cleavage of C-O bonds and formation of C-C bonds by uptake of hydrogen. This mechanism results in the formation of hydrocarbons, especially linear alkanes, with a molecular weight distribution that can be controlled to some extent by varying the FT reaction conditions (temperature and feed CO:H2 ratio) and catalyst properties. These properties include the pore size and other properties of the support material. The choice of catalyst can affect the yield of FT products in other ways. For example, iron-based FT catalysts tend to produce more oxygen-containing compounds, while the active metal ruthenium tends to produce only paraffins. The reaction pathways of FT synthesis follow a statistical kinetic model, resulting in hydrocarbons with an Anderson-Schultz-Flory distribution of carbon numbers. For C3 and C4 hydrocarbons, i.e., propane and butane, this generally involves operation in a low conversion regime with significant co-production of methane and ethane. On the other hand, high conversions are achieved with C5, which are liquid at room temperature. +Other potential routes for producing LPG hydrocarbons from synthesis gas have been described by K. Asami et al. (Surface Science and Catalysis Research 147 (2004) 427-432); Q. Zhang et al. (Fuel Processing Technology 85 (2004) 1139-1150); and Q. Ge et al. (Journal of Molecular Catalysis A: Chemistry 278 (2007) 215-219).

[0010] With regard to known pathways that offer potential conversion routes from methane, and preferably renewable methane such as that present in biogas, to LPG hydrocarbons, improvements are needed in many areas. These include selectivity and yield of reaction products, and / or management of CO2 (e.g., water-gas shift), which is typically present in the gaseous feed mixture or may be produced by the primary process chemistry. In general, the prior art would benefit from technologies that efficiently convert industrially available gaseous mixtures containing CO2 and other important reactants such as H2 and / or CH4 to products containing propane and / or butane, e.g., products with compositions close to liquefied petroleum gas (LPG). With regard to the practical impact of such technologies, the current goal of many countries around the world is to reduce deforestation and pollution generation associated with burning wood for heating and cooking. However, due to the remoteness of many locations and the long transportation routes involved, petroleum-derived LPG is expensive and is therefore not considered a viable substitute for wood. Thus, many notable advantages can be obtained by efficiently obtaining LPG hydrocarbons from renewable resources and other readily available gaseous mixtures. These benefits include eliminating the need to import petroleum-derived LPG, reduced GHG emissions, improved air quality and the potential stimulation of local economies, especially in poorer areas. Summary of the Invention

[0011] Aspects of the present invention relate to the discovery of new production routes for liquefied petroleum gas (LPG) products, including propane and / or butane, and in certain cases, renewable LPG products, i.e., a portion or all (e.g., at least about 70%) of the carbon content of the renewable LPG products (whether expressed on a weight % or mole % basis) is renewable carbon that is not derived from petroleum. Advantageously, regardless of whether the carbon content is renewable carbon or not, at least a portion (e.g., at least about 20%, at least about 30%, or at least about 40%) of the total carbon content of the exemplary LPG products described herein can be derived from CO2 as initially present in the gaseous feed mixture or fresh make-up feed. In the case of renewable carbon content also derived from CO2, such CO2 may be obtained, for example, from biogas, a bacterial digestion product originally contained in the biogas, from a biomass conversion gas product such as a biomass vaporizer product (e.g., such CO2 was originally contained in the vaporizer product). In the case of non-renewable carbon content derived from CO2, such CO2 (e.g., initially present in the gaseous feed mixture or fresh supplemental feedstock) may be obtained, for example, as a fossil fuel combustion product or a fossil fuel reforming product. In either case, it is understood that the CO2 to provide at least a portion of the total carbon content is not released directly into the atmosphere, but is useful as LPG.

[0012] A further aspect of the present invention relates to the discovery that a common CO2 source, and in particular a gaseous mixture of CO2 with either or both CH4 and H2, can be efficiently used as a feedstock in the production of an LPG product. Importantly, the entire feedstock and therefore all of these components can be reactants in one or both of the reforming and reverse water-gas shift (RWGS) reactions to produce a synthesis gas intermediate. This reaction(s) is / are used in combination with further conversion by LPG synthesis to obtain propane and / or butane in the LPG product. In the case of a gaseous feed mixture or fresh feedstock that contains both CH4 and CO2, e.g., is or contains biogas, these components can be reacted in the reforming stage according to the following: The dry reforming reaction described above produces a synthesis gas intermediate (i.e., a H2 / CO mixture) that contains H2 and CO. This intermediate can be converted to an LPG product by LPG synthesis. In the case of a gaseous feed mixture or fresh make-up feed containing both H2 and CO2, e.g., a gaseous mixture or fresh make-up feed that is or contains an industrial off-gas such as a "PSA tail gas" (or "PSA off-gas"), these components can be reacted according to the RWGS reaction to produce a synthesis gas intermediate for conversion to an LPG product as described above. As is known, the PSA tail gas is a by-product obtained by reforming CH4 to produce H2. Simultaneously with the RWGS reaction, the CH4 and CO2 components of the gaseous feed mixture or fresh make-up feed (e.g., as components of the PSA tail gas or other industrial off-gas) can be reacted according to the dry reforming reaction described above, thereby increasing the yield of H2 and CO in the synthesis gas intermediate.

[0013] Thus, another aspect of the invention relates to the discovery that the catalysts described herein have high activity for catalyzing reforming (including dry reforming) of CH4, and are similarly effective for catalyzing RWGS reactions under the same conditions. These properties of such catalysts are therefore particularly advantageous for producing LPG products from gaseous feed mixtures or fresh make-up feeds containing CO2, CH4 and / or H2, as described herein, all of which can be beneficially used as reactants in these reactions. Importantly, the RWGS activity, optionally combined with the recycle of the H2 / CO2-rich fraction of the LPG synthesis effluent (or a H2 / CO2-rich fraction separated therefrom) as described herein, allows for the effective management / conversion of, for example, large amounts (e.g., at least about 20 mol%) of CO2 present in the gaseous feed mixture or fresh make-up feed. Such mixtures or feeds may otherwise be difficult to monetize and / or may be conventionally combusted to obtain heating value. In the case of reforming and / or RWGS reactions (either at the reforming stage or at the RWGS stage), which are then followed by LPG synthesis, further integration with a recycle of the H2 / CO2 enriched fraction can significantly improve the total LPG yield (e.g., based on carbon in the fresh make-up feedstock) and the overall process economics.

[0014] A particular aspect of the invention relates to the advantages obtained by recycling H2 and CO2 present in the LPG synthesis effluent to the first stage of the method (e.g., the reforming stage, e.g., the reforming / RWGS stage, or the RWGS stage) or to the second LPG synthesis stage of the process. For example, it has been found that recycling H2 and CO2, in particular to the LPG synthesis stage (e.g., by combining H2 and CO2 separated from the LPG synthesis effluent with the synthesis gas intermediate or a part thereof obtained as a product of the first stage), leads to a dramatic increase in the selectivity of the LPG synthesis reaction towards LPG hydrocarbons, i.e. C3 and C4 hydrocarbons. To some extent, the CO conversion per pass in the LPG synthesis stage can be optimized (e.g., increased) by adjusting the LPG synthesis conditions, such as decreasing the space velocity to increase the residence time of the reactants and / or increasing the pressure to increase the reactant concentration, where the observed increase in selectivity corresponds to an increase in the product yield per pass with respect to that obtained in a baseline process with the same CO conversion level but without recycling. In this regard, those skilled in the art will recognize that even small increases in selectivity and / or yield per pass generally result in very large economic benefits on a commercial scale, such advantages being attributable, for example, to reduced formation of undesirable by-products and / or reduced recycle gas requirements.

[0015] Furthermore, in some embodiments, such as those involving relatively small-scale processing of gaseous feed mixtures, the use of an electrically heated reforming reactor to perform one or both of these reactions in a first or initial stage (e.g., reforming stage or RWGS stage) can further improve processing efficiency and compactness of the equipment, leading to reduced costs. Small-scale operations may include, for example, processing of gaseous feed mixtures or fresh make-up feeds obtained from low-volume biogas production facilities or holdup gas reserves. The electrically heated reforming reactor may include one or more resistive or inductive heating elements to control the amount of heat input to the reforming / RWGS catalyst bed, as described herein. Exemplary electrically heated reforming reactors thereby provide localized and responsive bed temperature control, examples of which are described in co-pending U.S. Provisional Application No. 63 / 107,537, which is incorporated herein by reference in its entirety.

[0016] Certain embodiments of the present invention are directed to processes for producing LPG products containing propane and / or butane, as well as LPG products obtained from such processes. These include LPG products, in which at least a portion (e.g., at least about 70% by weight or molar basis) of the carbon content of the propane and / or butane contained in these products is renewable carbon. A representative process includes a first stage in which a gaseous feed mixture or a fresh make-up feed is reformed and / or RWGS reacted, i.e., in a reforming stage, a RWGS stage, or a reforming / RWGS stage. The first stage is followed by a second stage in which at least a portion of the synthesis gas intermediate produced in the first stage is converted to include H2 and CO (i.e., a H2 / CO mixture). In particular, this intermediate or a portion thereof is converted to the propane and / or butane contained in the LPG product in a stage of LPG synthesis. According to a specific embodiment, in the first stage, a gaseous feed mixture or fresh make-up feed mainly containing (i) CH4 and CO2, or (ii) H2 and CO2 is contacted with a catalyst (e.g., reforming / RWGS catalyst) as described herein to produce a synthesis gas intermediate. In the second stage, the synthesis gas intermediate or a part thereof can be converted to LPG, for example, by a methanol synthesis reaction mechanism in which methanol produced from H2 and CO in the synthesis gas intermediate is dehydrated into LPG hydrocarbons and water. The synthesis gas intermediate or a part thereof used for the second stage LPG synthesis may have a H2:CO molar ratio of at least about 2.0, for example, about 2.0 to about 2.5, taking into account the hydrogen demand for methanol synthesis and dehydration. Such a molar ratio can be obtained from the first stage after adjusting the H2:CO molar ratio as desired.

[0017] Converting the synthesis gas intermediate to the LPG product can include contacting the intermediate, or a portion thereof, with an LPG synthesis catalyst system having methanol synthesis and dehydration activity. The catalyst system can include a catalyst mixture including both a methanol synthesis catalyst and a dehydration catalyst, such as when the catalysts are separate compositions (e.g., each in the form of separate particles). The catalyst system can alternatively or in combination include a bifunctional catalyst having a methanol synthesis functional component and a dehydration functional component. In the case of a catalyst mixture or bifunctional catalyst, (i) the corresponding methanol synthesis catalyst or methanol synthesis functional component can include one or more methanol synthesis active metals selected from the group consisting of Cu, Zn, Al, Pt, Pd, and Cr, and / or (ii) the corresponding dehydration catalyst or dehydration functional component can include a zeolite or a non-zeolitic molecular sieve.

[0018] Further embodiments of the present invention relate to processes for producing an LPG product from a synthesis gas comprising H2 and CO, e.g., a synthesis gas intermediate or an LPG synthetic feedstock obtained after one or more intermediate operations, as described herein. More broadly, any synthesis gas source may be used as an LPG synthetic feedstock in a representative LPG synthesis process, including an LPG synthetic feedstock having an H2:CO molar ratio representative of a synthesis gas intermediate, as described herein. The synthesis gas intermediate or LPG synthetic feedstock may be produced by reforming and / or RWGS reactions, as described herein. More broadly, however, the LPG synthesis process according to some embodiments does not require a specific synthesis gas source, and these embodiments are directed to those processes (e.g., processes including an LPG synthesis stage, e.g., in the case of a one-stage process) that do not necessarily require a given upstream conversion step (e.g., a reforming stage as described herein). A representative process includes contacting the LPG synthetic feedstock with any synthesis gas source containing H2 and CO (e.g., greater than about 50 mol% in total), more specifically, the H2 and CO in the synthesis gas, and optionally the CO2, with the LPG synthesis catalyst system described herein to convert the H2 and CO, and optionally the CO2, in the synthesis gas to hydrocarbons including propane and / or butane provided in the LPG product. In some cases, the LPG synthetic feedstock can also contain CO2, for example, in an amount of at least about 5 mol% (e.g., from about 5 mol% to about 50 mol%), at least about 10 mol% (e.g., from about 10 mol% to about 35 mol%), or at least about 15 mol% (e.g., from about 15 mol% to about 30 mol%). In such cases, the balance of the LPG synthetic feedstock can be or can be essentially a combination of H2 and CO, for example, in a H2:CO molar ratio representative of the synthesis gas intermediate described herein. It will be apparent to one of ordinary skill in the art with knowledge of this disclosure that particularly advantageous results are obtained with LPG synthetic feedstocks containing CO2.

[0019] Other particular embodiments relate to the above processes in which biogas is converted into an LPG product, i.e. the gaseous feed mixture or fresh make-up feed is or comprises biogas. Advantageously, the biogas provides a readily available gaseous feed mixture or fresh make-up feed, or any part thereof, mainly comprising CH4 and CO2. Importantly, large amounts of biogas may exist at locations remote from traditional LPG sources, and certain processes involving the processing of biogas may represent an economical and effective alternative to obtain propane and / or butane, useful for example for heating (e.g. cooking) applications. Also, the carbon content of the propane and / or butane of the LPG product thus produced is derived from CH4 and CO2 from organic waste, i.e. the carbon content is renewable. An exemplary process according to these particular embodiments includes contacting biogas (or a gaseous feed mixture or fresh make-up feed comprising biogas) with a reforming / RWGS catalyst in a reforming stage (and possibly not in the reforming / RWGS stage) to produce a synthesis gas intermediate comprising a H2 / CO mixture. The process may also include converting at least a portion of the synthesis gas intermediate to an LPG product, for example, via the methanol synthesis reaction scheme described herein.

[0020] According to certain further aspects and related embodiments, the present invention relates to a process for producing an LPG product comprising propane and / or butane, the process comprising: (a) contacting a gaseous feed mixture, preferably comprising primarily (i) CH4 and CO2, or (ii) H2 and CO2, with a reforming / RWGS catalyst in a reforming or RWGS stage to produce a synthesis gas intermediate comprising a H2 / CO mixture; and (b) converting the synthesis gas intermediate to an LPG product in an LPG synthesis stage.

[0021] According to certain further aspects and related embodiments, the present invention relates to a process for producing an LPG product comprising propane and / or butane, the process comprising the steps of: (a) in a reforming or RWGS stage, contacting a gaseous feed mixture comprising CH, CO and H (preferably in a combined amount of at least 30 mol %) with a reforming / RWGS catalyst to produce a synthesis gas intermediate comprising a H / CO mixture; preferably (b) in an LPG synthesis stage, contacting the synthesis gas intermediate with an LPG catalyst system to produce an LPG synthesis effluent; and preferably (c) separating the LPG product from the LPG synthesis effluent.

[0022] According to certain further aspects and related embodiments, the present invention relates to a process for producing an LPG product comprising propane and / or butane, the process comprising the step of contacting an LPG synthesis feedstock comprising H and CO, and optionally CO, preferably with an LPG synthesis catalyst system, the LPG synthesis catalyst system preferably comprising a mixture of: (i) a methanol synthesis catalyst, preferably (ii) a dehydration catalyst that converts at least a portion of the H and CO, and optionally at least a portion of the CO, in the synthesis gas to hydrocarbons comprising propane and / or butane, which are provided in the LPG product.

[0023] In at least one of the above aspects and related embodiments, the invention may have at least one of (eg, any combination of one or more of) the following further preferred features.

[0024] Preferably, the gaseous feed mixture comprises (i) at least about 75 mol % combined amount of CH4 and CO2 or (ii) at least about 75 mol % combined amount of H2 and CO2. Preferably, the gaseous feed mixture comprises less than about 10 mol % of one or more of CO, H2O, and O2, either independently or in a combined amount. Preferably, the gaseous feed mixture comprises biogas. Preferably, the LPG product is separated from an LPG synthesis effluent obtained from an LPG synthesis reactor of the LPG synthesis stage. Preferably, the LPG product comprises at least about 80 mol % combined amount of propane and butane. Preferably, the gaseous feed mixture comprises a recycled portion of the H2 / CO2 enriched fraction separated from the LPG synthesis effluent. The conversion of (b) is preferably performed by a methanol synthesis reaction mechanism. Preferably, converting the synthesis gas intermediate to the LPG product comprises contacting the synthesis gas intermediate with (i) a catalyst mixture comprising a methanol synthesis catalyst and a dehydration catalyst, or (ii) an LPG synthesis catalyst system comprising a bifunctional catalyst having: Preferably, the methanol synthesis catalyst or the methanol synthesis functional component comprises one or more methanol synthesis active metals selected from the group consisting of Cu, Zn, Al, Pt, Pd and Cr; Preferably, the dehydration catalyst or the dehydration functional component comprises a zeolite or a non-zeolitic molecular sieve; Preferably, at least about 70% of the feed carbon content of CH4 and CO2 in the gaseous feed mixture forms propane and / or butane; Preferably, the LPG product comprises propane and / or butane having at least about 70% renewable carbon content; Preferably, at least about 20% of the total carbon content of the LPG product is derived from CO2; Preferably, the CO2 is derived from biogas. Preferably, the process comprises the step of separating from the LPG synthesis effluent one or both of (i) an H2 / CO2-rich fraction and (ii) a water-rich fraction. Preferably, the process comprises the step of recycling one or both of (i) the H2 / CO2-rich fraction and (ii) the water-rich fraction to the reforming stage or to the RWGS stage, or recycling one or both of (i) the H2 / CO2-rich fraction and (ii) the water-rich fraction to the LPG synthesis stage.Preferably, the gaseous feed mixture comprises biogas present in the gaseous feed mixture as a fresh make-up feed portion of the gaseous feed mixture. Preferably, the reforming / RWGS catalyst is disposed in a catalyst bed volume in an electrically heated reforming reactor. Preferably, the methanol synthesis catalyst and / or the dehydration catalyst comprises yttrium in elemental or compound form. Preferably, the process comprises using an electrically heated reforming reactor in the reforming stage and / or the RWGS stage. Preferably, the electrically heated reforming reactor comprises one or more resistive or inductive heating elements for controlling the amount of heat input to the reforming / RWGS catalyst bed. Preferably, the synthesis gas intermediate or portion thereof for the second stage LPG synthesis has a H2:CO molar ratio of at least about 2.0, more preferably from about 2.0 to about 2.5. Preferably, the LPG synthetic feedstock comprises at least about 5 mol% CO2 (e.g., about 5 mol% to about 50 mol%), more preferably at least about 10 mol% (e.g., about 10 mol% to about 35 mol%), or more preferably at least about 15 mol% (e.g., about 15 mol% to about 30 mol%). Preferably, the gaseous feed mixture comprises CH4 and CO2 in a combined amount of at least 75 mol%, more preferably at least about 90 mol%, or more preferably at least about 95 mol%. Preferably, the gaseous feed mixture comprises H2 and CO2 in a combined amount of at least 75 mol%, more preferably at least about 90 mol%, or more preferably at least about 95 mol%. Preferably, the gaseous feed mixture comprises CH4, CO2 and H2 in a combined amount of at least 50 mol%, more preferably at least about 75 mol%, more preferably at least about 90 mol%, or more preferably at least about 95 mol%. Preferably, the gaseous feed mixture comprises no or only minor amounts of other components. Preferably, the gaseous feed mixture contains H2 in an amount of less than about 25 mol%, more preferably less than about 10 mol%, more preferably less than about 5 mol%, or more preferably less than about 1 mol%. Preferably, the gaseous feed mixture contains CH4 in an amount of less than about 25 mol%, more preferably less than about 10 mol%, more preferably less than about 5 mol%, or more preferably less than about 1 mol%.Preferably, the gaseous feed mixture contains oxygen-containing components other than CO2 in corresponding amounts (singly or in combination) of less than about 10 mol%, more preferably less than about 5 mol%, or more preferably less than about 1 mol%. Preferably, the reforming of CH4 occurring in the reforming stage or reforming / RWGS stage is substantially or completely dry reforming and / or substantially or completely free of partial oxidation. The biogas preferably comprises anaerobic bacterial digestion of biowaste and / or landfill gas. Preferably, the gaseous feed mixture is natural gas comprising about 65 mol% to about 98 mol% methane and about 3 mol% to about 35 mol% CO2. Preferably, the gaseous feed mixture comprises methane in an amount of about 5 mol% to about 45 mol%, CO2 in an amount of about 20 mol% to about 75 mol%, and H2 in an amount of about 10 mol% to about 45 mol%. Preferably, the gaseous feed mixture is one or more C2s, preferably selected from the group consisting of ethane, propane, butane, pentane and combinations thereof. + Preferably, the paraffinic hydrocarbon or combination of paraffinic hydrocarbons is present in an amount of at least about 1 mol %, more preferably at least about 3 mol %, or in a total amount (of the combination). Preferably, the gaseous feed mixture contains one or more C2 olefins, preferably selected from the group consisting of ethylene, propylene, butenes, pentenes, and combinations thereof. +Preferably, the olefin or combination of olefins is present in an amount or total amount (of the combination) of at least about 0.3 mole %, more preferably at least about 1 mole %. Preferably, the gaseous feed mixture contains at least about 1 molar ppm (e.g., about 1 molar ppm to about 1 molar %), more preferably at least about 3 molar ppm (e.g., about 3 molar ppm to about 5000 molar ppm), more preferably at least about 10 molar ppm (e.g., about 10 molar ppm to about 1000 molar ppm), or more preferably at least about 100 molar ppm (e.g., about 100 molar ppm to about 1000 molar ppm). Preferably, all sulfur is present in the form of H2S and / or other sulfur-containing components. Preferably, the reforming / RWGS catalyst contains a precious metal, which may be two or more precious metals, preferably on a solid support. Preferably, the solid support comprises cerium oxide, or a combination of cerium oxide and a suitable binder, such as alumina. Preferably, the cerium oxide is bound with a suitable binder in an amount of about 5 wt% to about 35 wt% based on the weight of the solid support. Preferably, the cerium oxide is bound with a suitable binder in an amount of at least about 60 wt%, more preferably at least about 75% by weight. Preferably, the cerium content is about 30% to about 80% by weight, more preferably about 40% to about 65% by weight, based on the weight of the catalyst. Preferably, one or more of silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, iron oxide, vanadium oxide, chromium oxide, nickel oxide, tungsten oxide, and strontium oxide are substantially absent in the solid support. Preferably, the solid support includes, in addition to cerium oxide, a second metal oxide as a cerium oxide binder. Preferably, the second metal oxide is selected from the group consisting of aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, iron oxide, vanadium oxide, chromium oxide, nickel oxide, tungsten oxide, and strontium oxide. Preferably, the second metal oxide is present in an amount of about 1% to about 45% by weight, more preferably about 5% to about 35% by weight, more preferably about 10% to about 25% by weight, based on the weight of the solid support.Preferably, the solid support comprises cerium oxide and a second metal oxide, the total amount of which is at least about 85% by weight, more preferably at least about 95% by weight, more preferably at least about 99% by weight, based on the weight of the solid support. Preferably, the second metal oxide as the cerium oxide binder is aluminum oxide. Preferably, the support and / or catalyst has an average pore size of about 2 to about 75 nm, more preferably about 5 to about 50 nm. Preferably, the support and / or catalyst has a pore volume of about 10% to about 80%, more preferably about 30% to about 55%, due to large pores of more than 50 nm. Preferably, the support and / or catalyst has a pore volume of about 20% to about 85%, more preferably about 35% to about 60%, due to mesopores of 2 to 50 nm. Preferably, the support and / or catalyst has a pore volume of less than about 2%, more preferably less than about 0.5%, due to pores of less than 2 nm. Preferably, the precious metal of the reforming / RWGS catalyst is selected from the group consisting of platinum (Pt), rhodium (Rh), ruthenium (Ru), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir) and gold (Au). Preferably, the reforming / RWGS catalyst comprises at least two precious metals selected from the group consisting of platinum (Pt), rhodium (Rh), ruthenium (Ru), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir) and gold (Au). Preferably, the precious metal is present in an amount of about 0.05% to about 5% by weight, about 0.3% to about 3% by weight, or about 0.5% to about 2% by weight, based on the weight of the catalyst, or optionally, the at least two precious metals are each independently present in an amount of about 0.05% to about 5% by weight. Preferably, the reforming and / or RWGS reactions can be carried out simultaneously, more preferably by contacting the gaseous feed mixture with the reforming / RWGS catalyst, preferably using a continuous stream of the gaseous feed mixture to improve process efficiency. Preferably, the contacting is carried out by continuously flowing the gaseous feed mixture through the reactor. Preferably, the reforming / RWGS conditions in the reactor used for one or both of these reactions include a temperature of from about 649°C (1200°F) to about 871°C (1600°F).Preferably, the reforming / RWGS conditions include a pressure greater than ambient. Preferably, the reforming / RWGS conditions include a weight flow rate of the feed gas mixture of about 0.05 hours. -1 About 10 hours from -1 up to about 0.1 hours, more preferably -1 Approximately 8.0 hours from -1 up to about 0.5 hours, more preferably -1 Approximately 5.0 hours from -1 Preferably, the methanol synthesis catalyst or the methanol synthesis functional component of the bifunctional catalyst comprises one or more of the methanol synthesis active metals. Preferably, the methanol synthesis active metals are selected from the group consisting of copper (Cu), zinc (Zn), aluminum (Al), platinum (Pt), palladium (Pd) and chromium (Cr). Preferably, the methanol synthesis catalyst or the methanol synthesis functional component of the bifunctional catalyst comprises Cu / ZnO / Al2O3 or is mainly composed of Cu / ZnO / Al2O3. Preferably, the dehydration catalyst or the dehydration functional component of the bifunctional catalyst is a zeolite (zeolitic molecular sieve) or a non-zeolitic molecular sieve. Preferably, yttrium is present in the methanol synthesis catalyst, methanol synthesis functional component, dehydration catalyst or dehydration functional component in an amount of about 0.01% to about 10% by weight, more preferably about 0.05% to about 5% by weight, more preferably about 0.1% to about 1% by weight.

[0025] These and other embodiments, aspects, and advantages of the present invention will become apparent from the following detailed description. [Brief description of the drawings]

[0026] Exemplary embodiments of the present invention and their advantages may be more fully understood by reference to the following description in consideration of the accompanying drawing, which provides a process flow diagram for producing an LPG product.

[0027] The figure should be understood as illustrating the process and some of the principles involved. For ease of explanation and understanding, the figure provides a simple overview with the understanding that the depicted elements are not necessarily drawn to scale. Valves, instruments, and other equipment and systems that are not important to understanding the various aspects of the invention are not shown. It will be apparent to one of ordinary skill in the art having understood this disclosure that the process for producing LPG hydrocarbons by reforming and / or RWG reactions may have alternative configurations and elements controlled by specific operational objectives, but these alternatives are still within the scope of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The expressions "wt. %" and "mol. %" used herein denote weight percentage and molar percentage, respectively. The expressions "ppm by weight" and "ppm by mole" denote molar percentage. For ideal gases, "mol. %" and "ppm by mole" are equivalent to volume percentage and volume percentage, respectively. In some cases, a percentage "%" may be given for the same value, whether expressed as weight percentage or molar percentage. For example, (i) the feed carbon content of the propane and / or butane that forms the LPG product, or (ii) the carbon content of the LPG product that is renewable carbon or CO2-derived carbon, has the same value whether expressed as weight percentage or molar percentage.

[0029] As used herein, the term "substantially" means to the extent of at least 95%. For example, the phrase "substantially all" may be replaced with "at least 95%."

[0030] A "gaseous feed mixture" as described herein can refer to, for example, the feed or all the feedstocks input in one stream or two or more individual or combined streams to a reactor used in the first stage of the process, i.e., the reforming stage or the RWGS stage (e.g., the reforming / RWGS stage). In certain embodiments utilizing recycle, the gaseous feed mixture can be fed to the reactor or reaction stage as described herein as a combination of (i) fresh make-up feed and (ii) the H2 / CO2-rich fraction in the LPG synthesis effluent. That is, the gaseous feed mixture can include (i) and (ii) such that the fresh make-up feed can be part of such gaseous feed mixture according to certain embodiments related to any "gaseous feed mixture" described herein. According to alternative embodiments, any reference to a "H2 / CO2-rich fraction" can more specifically refer to a "portion" of such "H2 / CO2-rich fraction", e.g., such a recycled portion, or a portion of such a recycled portion, consistent with the further disclosure below. For example, e.g., a purge stream, sampling stream, etc. may be removed from the H2 / CO2-rich fraction of the LPG synthesis effluent and only a recycled portion of such portion may be sent to the process (e.g., the first stage (e.g., a reforming / RWGS stage, or a reforming stage such as a RWGS stage) and / or the LPG synthesis stage, and optionally a different portion of this recycled portion may be sent to a different stage. In view of the above discussion and further discussion regarding recycle operations herein, the gaseous feed mixture may include a recycled portion of the H2 / CO2-rich fraction (or even a portion of such fraction) separated from fresh make-up feed and / or the LPG synthesis effluent.

[0031] Similarly, the "LPG synthetic feed" described herein may refer to the entirety of the feedstock that is fed or input to the reactor used in the second stage of the process, i.e., the LPG synthesis stage, e.g., in one stream or in two or more separate or combined streams. In certain embodiments utilizing recycle, the LPG synthetic feed may be fed to the reactor or reaction stage as a combination of (i) a synthesis gas intermediate or a portion thereof (e.g., extracted directly from the reactor used in the first stage of the process) and (ii) a portion of the H2 / CO2-enriched LPG synthetic effluent, as described herein. That is, the LPG synthetic feed may, according to certain embodiments, include (i) and (ii), such that the synthesis gas intermediate or a portion thereof is part of such LPG synthetic feed. As mentioned above, according to alternative embodiments, the "H2 / CO2-enriched fraction" may more specifically refer to a "portion" of such "H2 / CO2-enriched fraction," e.g., such a recycled portion, or a portion of such a recycled portion, consistent with the further disclosure below.

[0032] In the exemplary process described herein, the first (upstream) or initial stage may be referred to as the "reforming / RWGS stage" to indicate that both reforming and reverse water-gas shift (RWGS) reactions occur to some extent. As will be understood by those skilled in the art, in the context of this disclosure, reforming refers to reacting CH4 with an oxidant to produce H2 and CO (synthesis gas), which is preferably CO2 but may include any one or more of CO2, H2O, and O2. The RWGS reaction is understood in the art as follows: H2+CO2→H2O+CO In a broader embodiment, the first or initial stage may be a "reforming stage" where reforming of CH4 occurs as described above, but not necessarily where RWGS reactions occur. In other broader embodiments, the first or initial stage may be a "RWGS stage" where RWGS reactions occur as described above, but not necessarily where CH4 reforming occurs. For example, in the case of a gaseous feed mixture comprising CH4 and CO2, the first stage may be a reforming stage where these components react to produce synthesis gas. Typically, however, the RWGS reaction will cause at least some H2 of the synthesis gas present in the reaction mixture to react with CO2 also present in the reaction mixture, with the reforming stage being more specifically characterized as a "reforming / RWGS stage." In the case of a gaseous feed mixture comprising H2 and CO2, the first stage may be a RWGS stage where these components react as described above. It is therefore understood that in the case of a gaseous feed mixture comprising CO2, CH4, or H2, the first or initial stage may be a reforming stage or a RWGS stage. For any gaseous feed mixture including CH4 and CO2 (eg, including CH4, CO2 and H2), the first or initial stage may be a reforming / RWGS stage.

[0033] Typically, the first reforming or RWGS stage is followed by a second (downstream) stage of LPG synthesis utilizing at least a portion of the synthesis gas intermediate produced in the first stage, optionally followed by one or more intermediate operations as described herein. According to an exemplary embodiment, the first and second stages may be the only stages of the process involving reactions and / or using a catalyst or catalyst system to carry out these reactions. If desired, the process may include other reaction stages. That is, the designation of the reforming or RWGS stage as the "first" stage and the LPG synthesis stage as the "second" stage does not exclude the possibility of one or more other reaction stages before the first stage, between the first and second stages, and / or between the second stage: For example, an additional reaction stage may be used to carry out a water-gas shift reaction to produce H2 and CO2. Gaseous Feed Mixture

[0034] An exemplary process for producing an LPG product comprising propane and / or butane includes (a) contacting a gaseous feed mixture with a reforming / RWGS catalyst in a reforming or RWGS stage to produce a synthesis gas intermediate comprising a H2 / CO mixture, and (b) converting the synthesis gas intermediate to an LPG product, for example, by methanol synthesis and dehydration. Exemplary gaseous feed mixtures comprise primarily (i) CH4 and CO2, or (ii) H2 and CO2, with the term "predominantly" meaning that these gaseous feed mixtures comprise at least 50 mol% combined amount of (i) CH4 and CO2, or at least 50 mol% combined amount of (ii) H2 and CO2. In more specific embodiments, the gaseous feed mixtures comprise at least 75 mol%, at least about 90 mol%, or at least about 95 mol% combined amount of (i) CH4 and CO2, or (ii) at least 75 mol%, at least about 90 mol%, or at least about 95 mol% combined amount of H2 and CO2. According to other embodiments, the representative gaseous feed mixture may include CH4, CO2, and H2 in a combined amount of at least 50 mol%, at least about 75 mol%, at least about 90 mol%, or at least about 95 mol%. Alternatively, in combination with any of the features described herein, the representative gaseous feed mixture may include little or no other components. For example, (i) in the case of a gaseous feed mixture mainly including CH4 and CO2, such a gaseous feed mixture may include H2 in an amount of less than about 25 mol%, less than about 10 mol%, less than about 5 mol%, or less than about 1 mol%. (ii) in the case of a gaseous feed mixture mainly including H2 and CO2, such a gaseous feed mixture may include CH4 in an amount of less than about 25 mol%, less than about 10 mol%, less than about 5 mol%, or less than about 1 mol%. Any gaseous feed mixture described herein may contain oxygen-containing components other than CO, such as one or more of CO, HO, O, in corresponding amounts (singly or in combination) of less than about 10 mol%, less than about 5 mol%, or less than about 1 mol%.In this case, the reforming of CH4 may occur in the reforming stage or in the reforming / RWGS stage, may be substantially or completely dry reforming, and / or may be substantially or completely free of partial oxidation due to the limited presence or absence of oxidants other than CO2.

[0035] (i) In the case of a gaseous feed mixture mainly comprising CH4 and CO2, step (a) may be a reforming step or, if necessary, a reforming / RWGS step, according to which in either case the reaction of H2 and CO2 in the H2 / CO mixture of the synthesis gas intermediate can produce CH4 and CO. (ii) In the case of a gaseous feed mixture mainly comprising H2 and CO2, step (a) may be a RWGS step or, if necessary, a reforming / RWGS step, as described above. If step (a) is a RWGS step, the H2 in the H2 / CO mixture of the synthesis gas intermediate can be H2 representing the unreacted or equilibrium amount in the RWGS reaction of H2 and CO2 as described above, and the CO in the H2 / CO mixture can be CO produced in the RWGS reaction. If step (a) is a reforming / RWGS step, (ii) the gaseous feed mixture mainly comprising H2 and CO2 can further comprise CH4. Thus, the H2 and CO in the H2 / CO mixture of the synthesis gas intermediate can be produced by reacting with CH4 and CO2. It is also understood that H2 and CO in the intermediate H2 / CO mixture of the synthesis gas can represent equilibrium amounts in the RWGS reaction, whether or not the gaseous feed mixture includes CH4 that is reformed to produce H2. In a specific embodiment where the gaseous feed mixture includes CH4, H2 and CO in the intermediate H2 / CO mixture of the synthesis gas can represent equilibrium amounts in the combined reforming and RWGS reaction. In the reforming or reforming / RWGS stage, CH4 and CO2 can be reacted via the dry reforming reaction described above, and CH4 can be reacted with one or both of the other oxidants HO and O2 to produce H2 and / or CO in the intermediate H2 / CO mixture of the synthesis gas. For example, these other oxidants can also be present in the gaseous feed mixture, or HO can be present in the reaction mixture as a product of the RWGS reaction (although not necessarily in the gaseous feed mixture).

[0036] The gaseous feed mixture, or at least the components of the mixture (e.g., CO2, CH4, and / or H2), can be obtained from a number of sources. Advantageously, such sources include waste gases that are believed to have little or no economic value and that may otherwise contribute to atmospheric CO2 levels. For example, the gaseous feed mixture may be or include industrial process waste gases obtained from iron and steel manufacturing processes or non-ferrous product manufacturing processes. Other processes from which all or part of the gaseous feed mixture can be obtained include petroleum refining processes (e.g., processes that produce refinery tail gases), renewable hydrocarbon fuel (biofuel) production processes (e.g., hydropyrolysis processes, or fatty acid / triglyceride hydroconversion processes), biomass and coal (e.g., lignocellulose and coke) gasification processes, power production processes, carbon black production processes, ammonia production processes, other chemical (e.g., methanol) production processes, and coke production processes. In some cases, the gaseous feed mixture may be or include (i) well gases containing methane, or (ii) the gaseous products of the electrochemical reduction of carbon dioxide.

[0037] A particular gaseous feed mixture of interest is biogas, understood to include (i) the product of anaerobic bacterial digestion of biowaste, and (ii) waste landfill gas. Typically, methane gas contains about 35 mol% to about 90 mol% (e.g., about 40 mol% to about 80 mol%, or about 50 mol% to about 75 mol%) methane and about 10 mol% to about 60 mol% (e.g., about 15 mol% to about 55 mol%, or about 25 mol% to about 50 mol%) CO2. The gases N2, H2, H2S, O2 may be in small amounts (e.g., less than 20 mol% or less than 10 mol% in total). Thus, in some embodiments, the gaseous feed mixture may be or include biogas or other gases having these compositional characteristics.

[0038] Another gaseous feed mixture of interest is natural gas containing methane in an amount of about 65 mol% to about 98 mol% (e.g., about 70 mol% to about 95 mol%, or about 75 mol% to about 90 mol%) and CO2 in an amount of about 3 mol% to about 35 mol% (e.g., about 5 mol% to about 30 mol%, or about 10 mol% to about 25 mol%). Other hydrocarbons (e.g., ethane, propane), nitrogen may be present in small amounts. Of particular interest is stranded natural gas, which is not easily converted to a synthesis gas intermediate in an economical manner using known processes. Thus, in some embodiments, the gaseous feed mixture may be or include natural gas, such as natural gas containing relatively high amounts of CO2, such as at least about 10 mol% or at least about 25 mol%.

[0039] A further gaseous feed mixture of interest is hydrogen-depleted PSA tail gas, for example as described above, obtained from a hydrogen production process involving steam methane reforming (SMR). This mixture can include (i) methane in an amount of about 5 mol% to about 45 mol% (e.g., about 10 mol% to about 35 mol%, or about 15 mol% to about 25 mol%), (ii) CO2 in an amount of about 20 mol% to about 75 mol% (e.g., about 25 mol% to about 70 mol%, or about 35 mol% to about 60 mol%), and (iii) H2-% to about 40 mol%, or about 20 mol% to about 35 mol%) in an amount of about 10 mol% to about 45 mol% (e.g., about 15 mol%). The remainder of this stream may include primarily water vapor and / or CO. Thus, in some embodiments, the gaseous feed mixture may be or include hydrogen-depleted PSA tail gas.

[0040] A further gaseous feed mixture of interest is a gaseous effluent from a biological (bacterial) fermentation integrated with a hydrogen production process. Such integrated fermentation processes are described, for example, in U.S. Pat. No. 9,605,286, U.S. Pat. No. 9,145,300, U.S. Pat. No. 2013 / 0210096, and U.S. Pat. No. 2014 / 0028598. Such a gaseous effluent may contain (i) methane in an amount of about 5 to about 55 mol % (e.g., about 5 to about 45 mol %, or about 10 to about 40 mol %), (ii) CO2 in an amount of about 5 to about 75 mol % (e.g., about 5 to about 60 mol %, or about 10 to about 50 mol %), and (iii) H2 in an amount of about 5 to about 40 mol % (e.g., about 5 to about 40 mol %) to about 30 mol %, or about 10 to about 25 mol %). The remainder of this stream may contain primarily water vapor and / or CO. Thus, in some embodiments the gaseous feed mixture may be or may include such a gaseous effluent from a fermentation.

[0041] In some embodiments, the composition of the gaseous feed mixture described herein may represent the composition of two or more streams that are fed or input to the reactor used in the reforming or RWGS stage, respectively. With respect to the gaseous feed mixture, the individual streams may include, for example, fresh feed and / or recycle streams (e.g., fresh make-up feed and / or H2 / CO2 enriched fractions as described herein, or recycled portions of such fractions), or streams of one component, or streams enriched in one component (e.g., CH4 enriched fractions). According to alternative embodiments, any of the compositional features described above with respect to the gaseous feed mixture may be applied to a fresh make-up feed that may be part of the gaseous feed mixture fed or input to the reactor used in the reforming or RWGS stage, for example in the case of a recycle operation. Reforming / RWGS Catalyst

[0042] As mentioned above, one important aspect related to the present invention is the discovery that the catalysts described herein can catalyze reforming (including dry reforming) and RWGS reactions of CH4 to different extents depending on the composition of the particular gaseous feed mixture or fresh make-up feed described herein and the particular reforming / RWGS conditions used. This provides great flexibility in the composition of the gaseous feed mixture that can be processed into a synthesis gas intermediate utilizing reforming and / or RWGS reactions. As used herein, the term "reforming / RWGS catalyst" refers to a catalyst that has at least some of the activity to catalyze reforming and / or at least some of the activity to catalyze RWGS in an early or upstream stage of the process, whether characterized as a reforming stage or a RWGS stage. In a preferred embodiment, given a gaseous feed mixture and conditions used, such catalyst catalyzes these two reactions at least to some extent in the reforming / RWGS stage.

[0043] An exemplary embodiment includes contacting a gaseous feed mixture with a reforming / RWGS catalyst as described herein in a reforming or RWGS stage. This contacting can be performed batchwise, but is preferably performed continuously (e.g., such that the catalyst is disposed within a catalyst bed volume within the reactor) by continuously flowing the gaseous feed mixture to one or more reactors (preferably a single reactor) used in this stage that contain the reforming / RWGS catalyst. Thus, the reforming or RWGS stage can also include a continuous withdrawal from the reactor(s) of a synthesis gas intermediate that includes a H2 / CO mixture, i.e., an intermediate product that includes both H2 and CO produced from the reforming and / or RWGS reactions as described above.

[0044] The catalysts described herein have the advantage that they are particularly effective in reducing the amount of C2 +They exhibit many important advantages in their tolerance to components that may be present in gaseous feed mixtures, such as hydrocarbons (paraffins and olefins) and / or H2S or other sulfur-containing components (e.g., mercaptans). This property reduces the significant pre-treatment requirements of conventional processes, thereby improving flexibility in economically producing synthesis gas intermediates from normal process flows that contain significant concentrations of such components, even at relatively small operating scales. In some embodiments, any of the gaseous feed mixtures described herein contain, in addition to CO2, CH4, and / or H2, (i) one or more C2 + Paraffinic Hydrocarbons, and / or C6 + paraffinic hydrocarbons, and (ii) ethylene, propylene, butenes, pentenes, and / or C2 + One or more C6, such as olefinic hydrocarbons + In one embodiment, the gaseous feed mixture comprises one or more C2 olefinic hydrocarbons selected from the group consisting of ethane, propane, butane, pentane, and combinations thereof. + Any of these paraffinic hydrocarbons or combinations of paraffinic hydrocarbons may be present, for example, in an amount of at least about 1 mol % (e.g., from about 1 mol % to about 35 mol %), or in a total (combined) amount, for example, at least about 3 mol % (e.g., from about 3 mol % to about 20 mol %). In another embodiment, the gaseous feed mixture comprises one or more C2 olefins selected from the group consisting of ethylene, propylene, butenes, pentenes, and combinations thereof. +The olefins may include α-olefins. Any of these olefins or combinations of olefins may be present, for example, in an amount of at least about 0.3 mol % (e.g., from about 0.3 mol % to about 15 mol %), or in a total amount (combined), for example, at least about 1 mol % (e.g., from about 1 mol % to about 10 mol %). In general, any one or more hydrocarbons other than CH4 may be present in the gaseous feed mixture in an amount of at least about 3 mol % (e.g., from about 3 mol % to about 45 mol %) or in a total amount (combined), for example, at least about 5 mol % (e.g., from about 5 mol % to about 30 mol %). In terms of sulfur tolerance, the reforming / RWGS catalysts described herein provide additional advantages related to their ability to process sulfur-containing gaseous feed mixtures, such as those that include or are derived from natural gas, which may contain forms of sulfur, H2S or other sulfur-containing components depending on the source. Generally, the gaseous feed mixture may contain at least about 1 molar ppm (e.g., from about 1 molar ppm to about 1 molar ppm) total sulfur (e.g., present in the form of H2S and / or other sulfur-containing components), for example, at least about 3 molar ppm (e.g., from about 3 molar ppm to about 5000 molar ppm), at least about 10 molar ppm (e.g., from about 10 molar ppm to about 1000 molar ppm), or at least about 100 molar ppm (e.g., from about 100 molar ppm to about 1000 molar ppm).

[0045] The improved stability of the reforming / RWGS catalysts described herein, particularly for gaseous feed mixtures containing non-CH4 hydrocarbons and / or sulfur-containing components described herein, which generally promote catalyst deactivation and are at least partially due to their high activity, which manifests itself as lower operating temperatures (reactor or catalyst bed). This reduces the rate of coke formation / deposition on the catalyst surface, allowing for stable operation. The reforming / RWGS catalysts described herein are alternatively referred to as "cold" reforming catalysts and the associated processes as "cold" reforming processes, in view of their ability to achieve a given or targeted performance level (e.g., in terms of CH4 conversion) at the relatively low operating (or average catalyst bed) temperatures that are reforming / RWGS conditions.

[0046] Exemplary reforming / RWGS catalysts suitable for catalyzing the reforming and / or RWGS reactions described herein include a precious metal, which may be two or more precious metals, on a solid support. The solid support may include cerium oxide, and more specifically, cerium oxide in combination with a suitable binder (e.g., alumina) in an appropriate amount (e.g., about 5% to about 35% by weight) to provide mechanical strength.

[0047] The expression "on a solid support" is intended to encompass catalysts in which the active metal(s) are on the support surface and / or within the porous internal structure of the support. The solid support preferably comprises a metal oxide, in particular cerium oxide. The cerium oxide may be present in an amount of at least about 60% by weight, preferably at least about 75% by weight, based on the weight of the solid support (e.g., relative to the total amount(s) of metal oxides in the solid support). The cerium, whether present in oxide form or not, may be present in an amount of about 30% to about 80% by weight, preferably about 40% to about 65% by weight of the catalyst. The solid support may comprise all or substantially all (e.g., greater than about 95% by weight) of the cerium oxide, or a combined amount of all or substantially all (e.g., greater than about 95% by weight) of the cerium oxide and a second metal oxide (e.g., alumina) as a binder. One or more other metal oxides, such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, iron oxide, vanadium oxide, chromium oxide, nickel oxide, tungsten oxide, strontium oxide, etc., may also be present in individual amounts, or in combination, in the case of two or more such other metal oxides, and when expressed in small parts, corresponds to, for example, less than about 50% by weight, less than about 30% by weight, less than about 10% by weight, or less than about 5% by weight, based on the solid support. Preferably, one or more of silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, iron oxide, vanadium oxide, chromium oxide, nickel oxide, tungsten oxide, strontium oxide are substantially absent in the solid support. For example, these metal oxides are present in individual amounts, or when expressed in small parts, corresponds to, for example, less than about 3% by weight, less than about 0.5% by weight, or even less than about 0.1% by weight, based on the solid support, in the case of two or more other metal oxides. For purposes of illustration, in specific embodiments, (i) silicon oxide (silicon dioxide) can be present in an amount of less than about 0.5% by weight of the solid support, (ii) nickel oxide can be present in an amount of less than about 0.5% by weight of the solid support, or (iii) a combination of silicon oxide and nickel oxide may be present in an amount of less than about 0.5% by weight of the solid support.In other embodiments, the solid support may also be present in individual amounts independently or in otherwise combined amounts, and when expressed in larger portions, may include, for example, greater than about 50% by weight, greater than about 70% by weight, or greater than about 90% by weight of the solid support. In addition to cerium oxide and such one or more other metal oxides, other components may also be present in the solid support, and may be present in combined amounts that represent a smaller portion of the solid support, such as, preferably, less than about 10% by weight, less than about 5% by weight, or less than about 1% by weight. Such a smaller portion of cerium oxide may also represent all or substantially all of the balance of the solid support, not being representative of one or more of such other metal oxides.

[0048] According to certain embodiments, the solid support may further comprise a second metal oxide as a cerium oxide binder in addition to the cerium oxide. The second metal oxide may be selected from the group consisting of other metal oxides of aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, iron oxide, vanadium oxide, chromium oxide, nickel oxide, tungsten oxide, and strontium oxide. Such second metal oxide may be present in an amount of typically about 1% to about 45% by weight of the solid support, typically about 5% to about 35% by weight, and typically about 10% to about 25% by weight. Preferably, the solid support comprises cerium oxide and a second metal oxide, the total amount of which is at least about 85% by weight, at least about 95% by weight, and at least about 99% by weight of the solid support. The solid support may substantially comprise at least about 85% by weight, typically at least about 92% by weight, and typically at least about 95% by weight of the cerium oxide and the second metal oxide of the reforming / RWGS catalyst. The preferred second metal oxide for the cerium oxide binder is alumina.

[0049] A favorable property of solid supports (e.g., containing primarily cerium oxide), and therefore reforming / RWGS catalysts, is low acidity. In this regard, excess acid sites, especially strong Brønsted acid sites, on the support or catalyst are believed to contribute to coking and catalyst deactivation during reforming and / or RWGS reactions. Importantly, despite the fact that strong acid sites are known to promote the activity of many important commercial reactions, a low percentage or concentration of Brønsted acid sites offers advantages in terms of establishing a commercially viable catalyst life. A widely used method for measuring and quantifying acid site strength on solid materials is temperature programmed desorption using ammonia as a molecular probe (NH3-TPD). According to this method, a sample of the solid material is prepared by degassing and activating at high temperature and inert environment to remove water and other bound species. The sample is then saturated with NH3 at saturation temperature (e.g., 100°C) and then purged with an inert gas (e.g., helium gas) to provide conditions to remove physically adsorbed NH3. Start the temperature programmed desorption of the activated and saturated sample by increasing the temperature at a predetermined rate (e.g., 10 °C / min) to a final temperature (e.g., 400 °C) under a flow of inert gas. Measure the NH3 concentration in the gas continuously while driving the gas from the acid sites of the solid material with increased strength corresponding to the increased desorption temperature. Measurement of the NH3 concentration in the flowing inert gas can be performed, for example, using a gas chromatograph equipped with a thermal conductivity detector (GC-TCD).

[0050] Typically, the NH3 concentration versus temperature profile includes low and high temperature peaks corresponding to locations of solid materials with relatively low and high acid strength, respectively. The areas under these peaks can then provide the relative concentrations of acid sites of different types of acid strength (e.g., expressed as a percentage of total acid sites), or these areas can be used to determine the absolute concentrations of the different types (e.g., expressed in milliequivalents per gram of solid material). If the solid support or modified / RWGS catalyst produces two peaks on the NH3 concentration-temperature curve over the relevant range (e.g., from 100°C to 400°C), the first low temperature peak can be associated with weak Lewis acid sites and the second high temperature peak can be associated with strong Brønsted acid sites. For a typical solid support (e.g., primarily comprising cerium oxide) and a reforming / RWGS catalyst having such a support (considering that catalytically active metals deposited on such a support have a relatively small or negligible effect on the NH3-TPD analysis), an NH3 concentration versus temperature profile obtained from an NH3-TPD analysis over a temperature range of 100°C to 400°C (such a profile may have, for example, two discernible peaks) may exhibit a maximum NH3 concentration at a temperature below about 300°C (e.g., from about 150°C to about 300°C), more typically below about 250°C (e.g., from about 150°C to about 250°C). This maximum NH3 concentration may then be associated with a low-temperature peak corresponding to weak Lewis acid sites, and the maximum NH3 concentration and the temperature at which this concentration is exhibited define a point on this low-temperature peak. Based on the peak area of ​​this low temperature peak, the Lewis acid sites can represent at least about 25%, at least about 30%, or at least about 35% of the total acid sites (e.g., total Lewis acid sites and Bronsted acid sites combined) relative to the peak area of ​​the higher temperature peak corresponding to the strong Bronsted acid sites. For example, the higher temperature peak can exhibit a maximum NH3 concentration at about 300° C. to about 350° C., more typically from about 300° C. to about 325° C.The maximum NH3 concentration associated with the low temperature peak is typically greater than the maximum NH3 concentration associated with the high temperature peak, further indicating that weak Lewis acid sites contribute to a majority of the total acid sites of the solid support or modified / RWGS catalyst. In an exemplary embodiment, the solid support or modified / RWGS catalyst may have a Lewis acid site concentration of at least about 0.25 meq / g (e.g., from about 0.25 meq / g to about 1.5 meq / g), more typically at least about 0.35 meq / g (e.g., from about 0.35 meq / g to about 0.85 meq / g).

[0051] Solid supports (e.g., cerium oxide-based) and reforming / RWGS catalysts containing such supports are typically about 1 m 2 / g~about 100m 2 / g, for example, about 10m 2 / g~about 50m 2 The support and / or catalyst may have a surface area of ​​about 1.7 to about 300 nm (nm) in size, with a total pore volume of about 0.01 cc / g to about 0.5 cc / g, for example about 0.08 cc / g to about 0.25 cc / g. The pore volume may be measured by mercury intrusion porosimetry. The support and / or catalyst may have an average pore diameter of about 2 to about 75 nm, for example about 5 to about 50 nm. The support and / or catalyst may have (i) from about 10% to about 80% of its pore volume attributable to macropores greater than 50 nm, e.g., from about 30% to about 55% of its pore volume attributable to mesopores greater than 2 nm, and / or (iii) less than about 2% of its pore volume attributable to pores less than 2 nm, e.g., less than about 0.5% of its pore volume attributable to pores less than 2 nm. Pore size distributions can be obtained using the Barrett, Joyner, and Halenda methods.

[0052] Noble metals are understood to refer to a type of metal element that is resistant to oxidation. In a representative embodiment, the noble metals of the reforming / RWGS catalyst are at least two noble metals selected from the group consisting of platinum (Pt), rhodium (Rh), ruthenium (Ru), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir) and gold (Au), and according to a specific embodiment, the term "consisting of" is used only to describe the group member from which the noble metal(s) are selected, but does not exclude the addition of other noble metals and / or other common metals. Thus, catalysts containing noble metals include catalysts containing at least two noble metals, catalysts containing at least three noble metals, and also catalysts containing two noble metals and a third non-noble metal (e.g., a transition metal) such as a promoter metal. According to preferred embodiments, the precious metal or, optionally, at least two precious metals are each independently present in an amount of about 0.05% to about 5%, about 0.3% to about 3%, or about 0.5% to about 2% by weight based on the weight of the catalyst. For example, a representative catalyst may include two precious metals Pt and Rh, where Pt and Rh may be independently present in any of these ranges of amounts (e.g., about 0.05% to about 5% by weight). That is, Pt may be in this amount, Rh may be in this amount, or both Pt and Rh may be in this amount. Particularly preferred precious metal-containing reforming / RWGS catalysts of the present invention have Pt and Rh independently present in an amount of about 0.5% to about 2% by weight, each on a support, the support comprising substantially all or substantially cerium oxide and, optionally, a metal oxide binder (e.g., alumina). Regardless of the precious metal(s) used or the particular amounts used, it is preferred that these precious metals are in elemental (metallic or zero oxidation state) form. For example, particularly preferred precious metal-containing reforming / RWGS catalysts of the present invention may contain Pt and Rh independently in their elemental forms in amounts of from about 0.5% to about 2% by weight based on the weight of the catalyst.Other (compound) forms of Pt and / or Rh, preferably non-elemental Pt and / or Rh, or generally non-elemental forms of the precious metals, may be present independently in any single amount, but in the case of two or more precious metals, may be present independently in a combined amount of less than about 1 wt. %, less than about 0.5 wt. %, or even less than about 0.1 wt. % of the reforming / RWGS catalyst.

[0053] In representative embodiments, the at least two precious metals (e.g., Pt and Rh) are substantially the only precious metals present in the catalyst, e.g., the abundance or combined amount of any other precious metal(s) is less than about 0.1 wt. % or less than about 0.05 wt. % based on the weight of the catalyst. In further representative embodiments, the at least two precious metals (e.g., Pt and Rh) are substantially the only metals present in the catalyst, except for metals present in the solid support (e.g., cerium present as cerium oxide in the solid support). For example, the abundance or combined amount of any other metals, in addition to the at least two precious metal(s) and the metal of the solid support, can be less than about 0.1 wt. % or less than about 0.05 wt. % based on the weight of the catalyst. In some embodiments, the catalyst is substantially free of a particular metal, whether in elemental or compound form (e.g., in oxide form as a metal oxide component of the solid support). For example, certain metals can provide unfavorable acidity in the solid support, provide poor catalytic activity, and / or catalyze unfavorable reactions. In certain embodiments, one or more of Si, Ti, Zr, Mg, Ca, Fe, V, Cr, Ni, W and Sr are substantially absent in the solid support. For example, these metals may be present in separate amounts independently, or in the case of two or more of such metals, may be present in combined amounts of less than about 0.5 wt.%, less than about 0.1 wt.%, or even less than about 0.05 wt.% of the reforming / RWGS catalyst or the solid support of the catalyst. For example, one or more of Si, Zr, Mg, Ni may be present in these alone or in combination amounts. Any metal present in the catalyst, including the precious metal(s), may have a metal particle size generally in the range of about 0.3 nanometers (nm) to about 20 nm, generally in the range of about 0.5 nm to about 10 nm, and generally in the range of about 1 nm to about 5 nm.

[0054] The precious metal(s) can be incorporated into the solid support according to known catalyst preparation techniques, including sublimation, impregnation, or dry mixing. Impregnation is a preferred technique, in which an impregnation solution of soluble compounds of one or more precious metals in a polar (aqueous) or non-polar (e.g., organic) solvent can be contacted with the solid support, preferably under an inert atmosphere. For example, the contacting can be carried out in an ambient atmosphere of nitrogen, argon, and / or helium, or in a non-inert atmosphere such as air, preferably with stirring. The solvent can then be evaporated from the solid support, for example using heating, gas flow, and / or vacuum conditions, leaving a dry precious metal-impregnated support. The precious metal(s) can be dissolved in the same impregnation liquid, or impregnated separately using contact steps with different impregnation liquids, for example when two precious metals are simultaneously impregnated. In either case, the precious metal-impregnated support may undergo further preparation steps, such as washing with a solvent to remove excess precious metal(s) and impurities, further drying, calcination, etc., to provide the catalyst.

[0055] The solid support itself can be prepared according to known methods, such as extrusion to form cylindrical particles (extrudates) or spray drying to form oil droplets. Regardless of the specific shape of the solid support and the resulting catalyst particles (e.g., any shape, such as cylindrical or spherical), as described above, the amount of precious metal(s) present in the catalyst refers to the average weight of such precious metal(s) in a given catalyst particle, regardless of the specific distribution of the precious metal(s) in the particle. In this regard, it is understood that different preparation methods can provide different distributions, such as the precious metal(s) being supported primarily on or near the surface of the solid support, or the precious metal(s) being uniformly distributed throughout the solid support. In general, the weight percentages described herein, based on the weight of the solid support or otherwise based on the weight of the catalyst, can refer to the weight percentage in a single catalyst particle, but more typically refer to the average weight percentage of a number of catalyst particles, such as the number in the reactor that form the catalyst layer used in the methods described herein. Modification / RWGS conditions

[0056] The reforming and / or RWGS reactions are performed at a first (upstream) or early stage, preferably both simultaneously, by contacting the gaseous feed mixture with the reforming / RWGS catalyst described herein, preferably using a continuous stream of the gaseous feed mixture. For example, the contacting can be performed by continuously flowing the gaseous feed mixture through a reactor (which can be referred to as a reforming / RWGS reactor) containing a precious metal-containing reforming / RWGS catalyst as described herein. The reactor maintains reforming / RWGS conditions, i.e., the conditions within the reactor vessel, more specifically, the conditions within the reforming / RWGS catalyst bed contained within the vessel. These conditions include temperatures, pressures and flow rates for efficient conversion of methane and optionally other hydrocarbons to hydrogen when these conditions are used to perform reforming. Alternatively, these conditions may be combined to be effective for converting CO2 to CO and thereby performing the RWGS reaction.

[0057] Reforming / RWGS conditions useful for either or both of these reactions typically include temperatures from about 649° C. (1200° F.) to about 871° C. (1600° F.). In preferred embodiments, the processes described herein efficiently reform (oxidize) CH4 and / or allow the RWGS reaction to occur at temperatures significantly lower than the traditional typical reforming temperature of 816° C. (1500° F.) due to the high activity of the catalyst. For example, reforming / RWGS conditions can include temperatures ranging from about 677° C. (1250° F.) to about 788° C. (1450° F.), or from about 704° C. (1300° F.) to about 760° C. (1400° F.). When dry reforming is performed, higher temperatures, for example, from about 843°C (1550°C) to about 1010°C (1850°C), or from about 885°C (1625°C) to about 941°C (1725°C), can be used when the gaseous feed mixture includes CO2 as the reforming oxidant and includes HO and / or O2. If H2S and / or other sulfur-containing contaminants are present in significant concentrations (e.g., 100-1000 mol-ppm), it may be necessary to increase the temperature, for example, from about 732°C (1350°F) to about 843°C (1550°F), from about 760°C (1400°F) to about 816°C (1500°F), to maintain the desired conversion level (e.g., greater than about 85% CH4 conversion). Advantageously, it has been found that the compensation effect of increasing the temperature in response to increasing sulfur concentration in the gas feed mixture does not adversely affect catalyst stability, i.e., the overall catalyst life remains essentially unchanged for comparison between baseline sulfur-free operation and sulfur-containing operation run at the higher compensation temperature.

[0058] Particularly in the case of large-scale operation, the reactor is operated with limited heat release to its surroundings (e.g., in the case of adiabatic operation), and the catalyst bed temperature varies with the progress of a given reaction (e.g., in the case of exothermic or endothermic reactions, the fixed bed temperature profile is characterized by an increasing or decreasing profile along the axial length of the reactor, respectively). Thus, the temperatures given herein in relation to reforming / RWGS conditions or downstream LPG synthesis reaction conditions should be understood as average (or weighted average) catalyst bed temperatures. However, with respect to the high activity of the catalyst compositions described herein, particularly the reforming / RWGS catalysts, the temperatures described herein, particularly those associated with reforming / RWGS conditions, may be maximum or peak catalyst bed temperatures in some embodiments.

[0059] Still other reforming / RWGS conditions can include pressures above ambient pressure, i.e., pressures above 0 kPa (0 psig) gauge pressure, which corresponds to an absolute pressure of 101 kPa (14.7 psia). In reforming reactions, the number of moles of product is high relative to the number of moles of reactants, and therefore, in some cases, equilibrium may be achieved at relatively low pressures. Representative reforming / RWGS conditions can generally include gauge pressures from about 0 kPa (0 psig) to about 517 kPa (75 psig), typically from about 0 kPa (0 psig) to about 345 kPa (50 psig), and often from about 103 kPa (15 psig) to about 207 kPa (50 psig). According to some embodiments, it may be desirable to operate at higher pressures, for example, in the range of about 207 kPa (30 psig) to about 6.9 MPa (1000 psig), about 1.4 MPa (200 psig) to about 5.5 MPa (800 psig), or about 2.1 MPa (300 psig) to about 4.8 MPa (700 psig). In some cases, it may be preferred that the pressure used in the reactor(s) of the first stage (e.g., reforming / RWGS stage, or RWGS stage) is equal to or greater than the pressure used in the reactor(s) of the second stage (LPG synthesis stage), thereby avoiding intermediate pressurization operations. Representative reforming / RWGS conditions are generally about 0.05 hr -1 About 10 hours from -1 , typically about 0.1 hr-1 From about 8.0 hours -1 , often about 0.5 hours -1 From about 5.0 hours -1 The WHSV may further include a WHSV of 0.1 to 0.25%. As understood in the art, the WHSV is the weight flow rate of the gaseous feed mixture (or the total weight flow rate of the total charge of one or more reactors used in the reforming or RWGS stage) divided by the total weight of catalyst in the reforming / RWGS reactor(s), and represents the equivalent catalyst bed weight of the gaseous feed mixture (or total charge) processed per hour. The WHSV is related to the inverse of the residence time of the reactor. The reforming / RWGS catalyst may be contained within the reactor(s) in the form of a fixed bed, although other catalyst systems such as moving bed and fluidized bed systems are possible, which may be beneficial in processes that use continuous catalyst regeneration. Regardless of the particular layer configuration, the catalyst bed preferably includes individual particles of the reforming / RWGS catalyst, as opposed to a monolithic form of catalyst. For example, such individual catalyst particles may have a spherical or cylindrical diameter of less than about 10 mm, often less than about 5 mm (e.g., about 2 mm). In the case of cylindrical catalyst particles (eg, produced by extrusion), they may have a similar linear dimension (eg, from about 1 mm to about 10 mm, such as about 5 mm).

[0060] Advantageously, for a gaseous feed mixture containing CH4 in any of the above temperature ranges, the high activity of the catalyst can result in a component conversion of at least about 80% (e.g., about 80% to about 99%), at least about 85% (e.g., about 85% to about 99%), or at least about 90% (e.g., about 90% to about 97%). For a given gaseous feed mixture and reforming / RWGS catalyst, it will be understood by those skilled in the art based on knowledge gained from the present disclosure that a desired conversion level can be obtained or controlled by adjusting the particular reactor or catalyst bed temperature and / or other reforming / RWGS conditions (e.g., WHSV and / or pressure). Advantageously, the precious metal-containing catalysts described herein can have sufficient activity to achieve significant CH4 conversion, such as at least about 85%, in a stable manner at temperatures up to about 732°C (1350°F), at most about 704°C (1300°F) (e.g., as the peak or maximum temperature of the catalyst bed). In the case of dry reforming, for example, when the oxidant used in reforming (depending on the composition of the gaseous feed mixture) is primarily, or substantially, all CO2, this CH4 conversion level can be achieved at higher temperatures, for example, up to about 918°C (1685°F), or in some cases up to about 885°C (1625°F) (e.g., as a peak or maximum catalyst bed temperature). As understood in the art, the conversion of CH4 can be calculated based on the following conditions: 100*(CH4 原料 -CH4 生成物 ) / CH4 原料 Here, CH4 原料 is the total amount (e.g., total weight or total moles, etc.) of CH4 in the gas feed mixture (or total amount of all inputs) supplied to the reactor(s) for the reforming or RWGS stage, 生成物is the total amount of CH4 in the synthesis gas intermediate resulting from this step. For continuous processes, these total amounts are more conveniently expressed in terms of flow rate or total amount per unit time (e.g., total weight / hour or total moles / hour). These CH4 conversion levels can be based on the "single pass" conversion achieved in one pass through the reforming / RWGS stage (e.g., reforming / RWGS reactor), or the total conversion achieved by returning a recycled portion of the LPG synthesis effluent to the reforming / RWGS stage (e.g., reforming / RWGS reactor), as described in more detail below. In this regard, the recycled portion of the portion of the H2 / CO2-rich effluent can also include residual or unconverted CH4 that can be converted during the continuous process through the first reaction stage to increase the overall conversion of CH4.

[0061] Given that the CH4 reforming reaction produces H2 and CO, the concentrations of these components in the synthesis gas intermediate (reformed product) can be increased compared to the gaseous feed mixture (or the combined input to one or more reactors for the reforming or RWGS stages). In some embodiments, depending on the H2 concentration in the gaseous feed mixture and the extent of the RWGS reaction, the CO concentration can be increased and the H2 concentration can be decreased. In exemplary embodiments, the synthesis gas intermediate may include an amount of CO of at least about 5 mol% (e.g., about 5 mol% to about 50 mol%) or at least about 8 mol% (e.g., about 8 mol% to about 35 mol%). In other embodiments that achieve high levels of conversion of CH4, the synthesis gas intermediate may include a higher amount of CO, such as at least about 30 mol% (e.g., about 30 mol% to about 65 mol%) or at least about 40 mol% (e.g., about 40 mol% to about 55 mol%). In further exemplary embodiments, the synthesis gas intermediate may include H in an amount of at least about 30 mol % (e.g., about 30 mol % to about 90 mol %) or at least about 40 mol % (e.g., about 40 mol % to about 80 mol %). With respect to the gaseous feed mixture, depending on the amount of H present, and the amount of CO and HO present (which react with CH4O to produce stoichiometric molar ratios of H2:CO of 1:1 and 3:1, respectively), the H2:CO molar ratio of the synthesis gas intermediate may be from about 1.0 to about 7.0, e.g., from about 4.0 to about 6.5 for high ratios. Alternatively, for lower ratios, the H2:CO molar ratio of the synthesis gas intermediate may be from about 1.0 to about 3.0, e.g., from about 1.8 to about 2.4. According to other embodiments, for example when CH4 is reformed with an oxidant, the oxidant may be primarily, substantially entirely, or entirely CO2, and the H2:CO molar ratio of the synthesis gas intermediate may be low, for example, from about 0.5 to about 1.5, such as from about 0.8 to about 1.2, based solely on considerations of the stoichiometry of the dry reforming reaction.

[0062] Considering the reaction chemistry for the subsequent LPG synthesis (e.g., methanol synthesis and dehydration), the synthesis gas intermediate or a portion thereof used in this step may have a H2:CO molar ratio of at least 1.0 (e.g., from about 1.0 to about 3.5, or from about 1.5 to about 3.0), more preferably at least about 2.0 (e.g., from about 2.0 to about 4.0, from about 2.0 to about 3.0, or from about 2.0 to about 2.5). In some cases, an excess of H2 (i.e., H2 exceeds the stoichiometric amount required to form the methanol intermediate by reaction with CO and / or CO2) may be required to improve the stability of the catalyst system for the downstream LPG synthesis. In any case, the above molar ratios may represent the synthesis gas intermediate or a portion thereof for LPG synthesis obtained directly from the reactor used in the reforming or RWGS stage, or obtained after adjusting the H2:CO molar ratio according to an intermediate operation, for example, by adding a H2 source and / or a CO source before (e.g., upstream) the LPG synthesis stage. As described herein, a representative source of H2 and / or CO is the H2 / CO2-enriched fraction of the LPG synthesis effluent, or a recycled portion thereof. Other representative sources of H2a and / or CO are purified hydrogen gas (e.g., separated by PSA or membrane) or impure hydrogen gas (e.g., synthesis gas). In other embodiments, water (e.g., condensation) can be removed from the synthesis gas intermediate used in the LPG synthesis, or a portion thereof, between (a) the reforming or RWGS stage and (b) the LPG synthesis stage, e.g., to facilitate dehydration (water-producing) reactions. Synthesis of liquefied petroleum gas (LPG)

[0063] As mentioned above, a first (upstream) or initial reaction step producing a synthesis gas intermediate comprising H and CO (i.e., a H / CO mixture) can be followed by a second (downstream) step of converting the synthesis gas intermediate, or a portion thereof, to propane and / or butanes in the LPG product. Such conversion of synthesis gas to LPG can be carried out, for example, according to the first pathway, by a methanol synthesis reaction mechanism in which methanol produced from the H and CO in the synthesis gas is dehydrated to LPG hydrocarbons and water. Propane (CH) and butanes (CH 10 ) is prepared according to this reaction scheme, the following exemplary chemistry is illustrated: 14H2+7CO→(7CH3OH and 7CH3OH+2H2→C3H8+C4H 10 +7H2O Alternatively, but preferably in combination, according to a second pathway, CO2 present in the synthesis gas intermediate or part thereof used as feedstock for the LPG synthesis stage (LPG synthesis feedstock) can also be advantageously reacted in the initial methanol synthesis. For example, to produce the same number of moles of CH3OH as shown in the above reactions producing propane and butane, CO2 can be consumed instead of CO as follows: 21H2+7CO2→7CH3OH+7H2O

[0064] With respect to the hydrogen requirements for the synthesis and dehydration of methanol via the first pathway involving hydrogenation of CO, the synthesis gas intermediate or portions thereof used in these steps may have a H2:CO molar ratio as described above, or may be adjusted to obtain such a H2:CO molar ratio to provide an LPG synthetic feedstock. In other embodiments, a higher H2:CO molar ratio of the LPG synthetic feedstock may be desirable, such as to account for the additional hydrogen consumption associated with CO2 hydrogenation via the second pathway. In general, a representative process includes feeding or injecting all or a portion of the synthesis gas intermediate, optionally after one or more intermediate operations that may be used to provide an LPG synthetic feedstock having a different composition and / or properties than the synthesis gas intermediate. Such intermediate operations include cooling, heating, pressurization, depressurization, separation of one or more components (e.g., removal of condensate), addition of one or more components (e.g., addition of H2 and / or CO to adjust the H2:CO molar ratio of the LPG synthetic feed to the syngas intermediate), and / or reaction of one or more components (e.g., reaction of H2 and / or CO using another water gas shift reaction or a reverse water gas shift reaction), which operation(s) are performed on the syngas intermediate to provide the LPG synthetic feed to the LPG synthesis reactor(s) of the LPG synthesis stage.

[0065] Considering that the temperatures and pressures typically used in the LPG synthesis reactor(s) of the LPG synthesis stage are relative to the temperatures and pressures used in the reactor(s) of the reforming stage or RWGS stage, the synthesis gas intermediate can be cooled, separated from condensed water, and pressurized. In some embodiments, these may be the only intermediate operations that the synthesis gas intermediate undergoes to provide the LPG synthesis feedstock. In other embodiments, cooling and pressurization may be the only intermediate operations. In other embodiments, the intermediate operation may be the addition of the fraction in the H2 / CO2-enriched LPG synthesis effluent (or a portion thereof, e.g. a recycled portion thereof) (with the synthesis gas intermediate or a portion thereof). The addition of the H2 / CO2-enriched fraction or a portion thereof may be the only intermediate operation, and in some embodiments may be combined with one or more of cooling, removal of condensed water, and pressurization. In other embodiments, optional intermediate operations can include removing CO2 using a water vapor selective adsorbent such as 5A molecular sieves and / or following a conventional acid gas treatment step (e.g., amine scrubbing) as opposed to gas phase HO (hence condensed liquid phase HO). According to some embodiments, CO2 removal can be performed on the synthesis gas intermediate upstream of the LPG synthesis stage (e.g., as an intermediate operation). It is preferred that the water produced in the reactor(s) of the reforming stage or RWGS stage is condensed from the synthesis gas intermediate prior to the LPG synthesis reactor(s) and / or that the H2:CO molar ratio of the synthesis gas intermediate is not adjusted. The non-use of intermediate operations, limited intermediate operations, and / or omission of intermediate operations or several intermediate operations between the reforming stage or RWGS stage and the LPG synthesis stage brings advantages related to the overall simplification of the process for producing the LPG product.

[0066] The conditions of the LPG synthesis stage, and more specifically the LPG synthesis reactor(s) used in this stage, are suitable for converting H2 and CO into the LPG product propane and / or butane. In an exemplary embodiment, the LPG synthesis reaction conditions contained in at least one LPG synthesis reactor, and more specifically the catalyst beds within the reactors, can include an LPG synthesis reaction temperature ranging from about 204°C (400°F) to about 454°C (850°F), or from about 316°C (600°F) to about 399°C (750°F). As mentioned above, these temperatures can be understood to refer to the average (or weighted average) catalyst bed temperatures, or according to some embodiments, may be the maximum or peak catalyst bed temperatures. Suitable LPG synthesis reaction pressures for use in the at least one LPG synthesis reactor can include gauge pressures from about 690 kPa (100 psig) to about 6.9 MPa (1000 psig), such as from about 1.38 MPa (200 psig) to about 2.76 MPa (400 psig) or from about 3.4 MPa (500 psig) to about 5.2 MPa (750 psig). LPG synthesis catalyst system

[0067] In the LPG synthesis reactor(s), the LPG synthesis feedstock, representing all or a portion of the synthesis gas intermediate, optionally after one or more of the intermediate operations described above, can be contacted with a suitable LPG synthesis catalyst (e.g., a bed of LPG synthesis catalyst particles disposed in the LPG synthesis reactor) under LPG synthesis reaction conditions, which can include the temperatures and / or pressures described above. A representative LPG synthesis catalyst can be considered a "catalyst system" since it can include at least two components having different catalytic activities: (i) separate compositions of a methanol synthesis catalyst and a dehydration catalyst (e.g., each composition is present in the form of separate particles), or (ii) a composition of a bifunctional catalyst (e.g., the catalyst is present in the form of separate particles) with a methanol synthesis functional component and a dehydration functional component. In addition to such separate compositions of catalyst or a single composition of a bifunctional catalyst, a representative LPG synthesis catalyst system can include additional components, such as, for example, silica or sand particles, that act to absorb heat and / or change the distribution of solids. Such additional components may be present in a given catalyst system in amounts of, for example, at least 10% by weight, at least 20% by weight, or at least 40% by weight.

[0068] A representative methanol synthesis catalyst or a methanol synthesis functional component of a bifunctional catalyst may contain one or more methanol synthesis active metals selected from the group consisting of copper (Cu), zinc (Zn), aluminum (Al), platinum (Pt), palladium (Pd) and chromium (Cr). These metals may be in their elemental or compound form. For example, in the case of Cu, Pt, and Pd, these metals are preferably in elemental form, and in the case of Zn, Al, and Cr, they are preferably in ZnO, Al2O3, and Cr2O3, respectively. In some preferred embodiments of the present invention, in the case of a methanol synthesis catalyst or in the case of a methanol synthesis functional component containing this metal, all or a part of Cu may be in the form of its oxide, CuO. A particularly representative methanol synthesis catalyst is an oxide of copper and zinc on an alumina catalyst, containing or mainly composed of Cu / ZnO / Al2O3. This "CZA" methanol synthesis catalyst may be the methanol synthesis functional component of a bifunctional catalyst.

[0069] For methanol synthesis catalysts or methanol synthesis functional components comprising one or more of Cu, Zn, Al, Pt, Pd and Cr, these metal(s) may be present independently in the respective methanol synthesis catalyst or bifunctional catalyst in an amount of generally about 0.5% to about 45% by weight, generally about 1% to about 20% by weight, and generally about 1% to about 10% by weight, based on the weight of the entire catalyst, regardless of their specific form(s). In some embodiments, metallic Cu may be present in the methanol synthesis catalyst or bifunctional catalyst in an amount of about 1% to about 25% by weight, for example about 1% to about 15% by weight, based on the total weight of the catalyst. In the methanol synthesis catalyst or bifunctional catalyst, metallic Zn may be present alone or in combination with such amount of Cu in an amount of about 1% to about 20% by weight, for example about 1% to about 10% by weight, based on the total weight of the catalyst. In the methanol synthesis catalyst or bifunctional catalyst, the metal Al, alone or in combination with such amounts of Cu and / or Zn, may be present in an amount of about 1 wt.% to about 30 wt.%, such as about 5 wt.% to about 20 wt.%, based on the total weight of the catalyst. Any one or more of the metals Pt, Pd and / or Cr, alone or in combination with such amounts of Cu, Zn and / or Al, may be present in the methanol synthesis catalyst or bifunctional catalyst in an amount or combination of about 1 wt.% to about 10 wt.%, such as about 1 wt.% to about 5 wt.%, based on the total weight of the catalyst.

[0070] In the case of the methanol synthesis catalyst or the methanol synthesis functional component of the bifunctional catalyst, the methanol synthesis active metals Cu, Zn, Pt, Pd and / or Cr may be supported on a solid support, especially when they are elements. Representative solid supports include one or more metal oxides selected from the group consisting of aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, strontium oxide, etc. The expression "on a solid support" is intended to encompass methanol synthesis catalyst solid supports and bifunctional catalyst solid supports in which the methanol synthesis active metal(s) are supported on the support surface and / or within the porous internal structure.

[0071] In the case of a methanol synthesis catalyst or a methanol synthesis functional component of a dual-function catalyst, the methanol synthesis active metal(s) or any form of such metal (e.g., their respective oxide forms), and any solid support can constitute all or substantially all of the catalyst or component. For example, the methanol synthesis active metal(s) or any form of such metal, and any solid support may be present in a combined amount representing at least about 90%, at least about 95%, or at least about 99% of the total weight of the methanol synthesis catalyst or methanol synthesis functional component.

[0072] Representative dehydration catalysts or the dehydration functional component of the bifunctional catalyst may include zeolites (zeolitic molecular sieves) or non-zeolitic molecular sieves. Particular zeolites may have one or more structure types selected from the group consisting of FAU, fer, mel, mtw, MWW, mor, BEA, ltl, MFI, lta, emt, eri, maz, mei, and ton, preferably selected from FAU, fer, MWW, MOR, BEA, ltl, and MFI. The structures of zeolites having these and other structure types are described in Meier, WM et al., Atlas of Zeolite Structure Types, 4th Edition, Elsevier: Boston (1996), and further references are provided. Specific examples include zeolite Y (FAU structure), zeolite X (FAU structure), MCM-22 (MWW structure), zeolite beta (BEA structure) and ZSM-5 (MFI structure), with zeolite beta and ZSM-5 being illustrative.

[0073] Non-zeolitic molecular sieves include ELAPO molecular sieves which have an empirical chemical composition on an anhydrous basis represented by the formula: [ka] where EL is an element selected from the group consisting of silicon, magnesium, zinc, iron, cobalt, nickel, manganese, chromium and mixtures thereof, x is the mole fraction of EL and is typically at least 0.005, y is the mole fraction of aluminum and is at least 0.01, z is the mole fraction of phosphorus and is at least 0.01, and x+y+z=1. When EL is a mixture of metals, x represents the total mole fraction of the metals present. The preparation of various ELAPO molecular sieves is known, and examples of synthesis methods and their final products are described in U.S. Pat. No. 5,191,141 (ELAPO), U.S. Pat. No. 4,554,143 (FeAPO), U.S. Pat. No. 4,440,871 (SAPO), U.S. Pat. No. 4,853,197 (MAPO, MnAPO, ZnAPO, CoAPO), U.S. Pat. No. 4,793,984 (CAPO), U.S. Pat. No. 4,752,651, and U.S. Pat. No. 4,310,440. Preferred ELAPO molecular sieves are SAPO and ALPO molecular sieves. In general, ELAPO molecular sieves are synthesized by hydrothermal crystallization from a reaction mixture containing reactive sources of EL, aluminum, phosphorus, and a templating agent. The reactive source of EL is a metal salt of the EL element as defined above, such as its chloride or nitrate. When EL is silicon, the preferred source is fumed silica, colloidal silica or precipitated silica. The preferred reactive sources of aluminum and phosphorus are pseudoboehmite alumina and phosphoric acid. As templating agents, amines and quaternary ammonium compounds are preferred. A particularly preferred template agent is tetraethylammonium hydroxide (TEAOH).

[0074] Particularly preferred dehydration catalysts or dehydration functional components include ELAPO molecular sieves, in which the molecular sieves are referred to as SAPO (silica aluminophosphate) molecular sieves. In addition to those described in the above U.S. Pat. No. 4,440,871 and U.S. Pat. No. 5,191,141, usable SAPO molecular sieves are described in U.S. Pat. No. 5,126,308. In the specific crystal structure described in U.S. Pat. No. 4,440,871, SAPO-34, i.e., structure type 34, represents a preferred component of the LPG synthesis catalyst system. The SAPO-34 structure is characterized by its ability to adsorb xenon but not isobutane, and indicates that its pore size is about 4.2. Due to its acidity, SAPO-34 can catalyze the conversion of methanol intermediates to olefins such as propylene. Thus, a representative dehydration catalyst or dehydration functional component of a dual-functional catalyst may comprise SAPO-34 or other SAPO molecular sieves, such as SAPO-17, which is also disclosed in U.S. Pat. No. 4,440,871, and has a structure characterized by adsorbing oxygen, hexane and water, but not isobutane, and exhibits a pore size indicating hexane of greater than about 4.3 and less than about 5.0. Due to its acidity, SAPO-34 can catalyze the conversion of methanol intermediates to olefins such as propylene. Without being limited by theory, it is believed that the characteristic hydrogen partial pressures used in the LPG synthesis stage can not only promote the hydrogenation of these olefins, but also prevent coking and stabilize the dehydration catalyst / functional component.

[0075] With regard to the stability of the catalysts of the present invention (reforming / RWGS catalysts, methanol synthesis catalysts, dehydration catalysts, bifunctional catalysts), it is believed that the by-production of formaldehyde may be detrimental due to the tendency to form coke precursors such as polycyclic aromatic hydrocarbons. In this regard, another aspect of the present invention relates to the use of yttrium in any of these catalysts, or as a separate component or catalyst composition. Without being limited to a particular theory regarding the advantages obtained by the use of yttrium, it is believed that this metal has beneficial activity in decomposing formaldehyde that may be generated / accumulated in one or two reaction stages of the process. Thus, in some embodiments, any of the catalyst compositions described herein may include or further include yttrium in elemental or compound form, such as yttrium in the form of yttrium (yttrium oxide). For example, as discussed above, yttrium oxide is useful as the metal oxide component of the solid support for reforming / RWGS catalysts. For any of the catalysts described herein, yttrium (e.g., yttrium oxide or other form) may be present in an amount of about 0.01 wt% to about 10 wt%, such as about 0.05 wt% to about 5 wt%, or about 0.1 wt% to about 1 wt%. Alternatively, yttrium (e.g., yttrium oxide or other form) can be present as a separate composition to provide a multi-composition reforming / RWGS catalyst system or LPG synthesis catalyst system, where yttrium is present in that amount relative to the total weight of the catalyst system having two or more separate compositions.

[0076] Representative methanol synthesis catalysts or bifunctional catalysts may have metal(s) other than Cu, Zn, Al, Pt, Pd, and / or Cr present in small amounts. For example, any of such other metal(s) may be present independently at less than about 1 wt.%, less than about 0.1 wt.%, or less than about 0.05 wt.%, based on the total weight of the catalyst. Alternatively, any two or more such other metals may be present in a combined amount of less than about 2 wt.%, less than about 0.5 wt.%, or less than about 0.1 wt.%, based on the total weight of the catalyst. According to certain embodiments, in particular in the case of (i) a methanol synthesis catalyst comprising a solid support or (ii) a bifunctional catalyst comprising a zeolite or a non-zeolitic molecular sieve as the dehydration functional component, such metals other than Cu, Zn, Al, Pt, Pd and / or Cr present in the above amounts are more particularly: (i) metals other than Cu, Zn, Al, Pt, Pd, Cr and Si; Cu, Zn, Al, Pt, Pd, Cr, Si, Ti, Zr, Mg, Ca, and and Sr; metals other than Cu, Zn, Al, Pt, Pd, Cr, Si, Ti, Zr, Mg, Ca, Sr, and Y; or (ii) metals other than Cu, Zn, Al, Pt, Pd, Cr, Si, and P; metals other than Cu, Zn, Al, Pt, Pd, Cr, Si, P, Mg, Zn, Fe, Co, Ni, and Mn, or metals other than Cu, Zn, Al, Pt, Pd, Cr, Si, P, Mg, Zn, Fe, Co, Ni, Mn, and Y.

[0077] In the case of the dehydration catalyst or the dehydration functional component of the bifunctional catalyst, the zeolite or non-zeolitic molecular sieve can constitute all or substantially all of the catalyst or component. For example, the zeolite or non-zeolitic molecular sieve may be present in an amount corresponding to at least about 90%, at least about 95%, or at least about 99% of the total weight of the dehydration catalyst or the dehydration functional component. In the case of the bifunctional catalyst, the combined amount of (i) the methanol synthesis active metal(s) or any form of such metal (e.g., their respective oxide forms) and any solid support, and (ii) the zeolite or non-zeolitic molecular sieve can constitute all or substantially all of the bifunctional catalyst. For example, (i) and (ii) may be present in a combined amount corresponding to at least about 90%, at least about 95%, or at least about 99% of the total weight of the bifunctional catalyst.

[0078] Thus, a particular embodiment for carrying out LPG synthesis includes using a single catalyst composition, i.e., a bifunctional catalyst consisting of a methanol synthesis functional component and a dehydration functional component corresponding to a methanol synthesis catalyst and a dehydration catalyst, respectively. The functional components of the bifunctional catalyst may be present in equal or substantially equal proportions by weight when combined into a single catalyst composition. For example, (i) the methanol synthesis functional component and (ii) the dehydration functional component may be present in the bifunctional catalyst in a weight ratio (i):(ii) of about 1:1. Generally, however, this weight ratio may vary, for example, the weight ratio of (i):(ii) may be from about 10:1 to about 1:10, such as from about 5:1 to about 1:5, about 3:1 to about 1:3. Thus, a representative bifunctional catalyst may include (i) a methanol synthesis functional component comprising one or more of the methanol synthesis active metals as described above and, optionally, a solid support as described above, and (ii) a dehydration functional component comprising a zeolite or non-zeolitic molecular sieve as described above. From the above description, including the weight ratios in which (i) and (ii) above may be combined, it is understood that one or more of the methanol synthesis active metals may be present in the bifunctional catalyst as a whole in a lesser amount or total amount than the amount present in the methanol synthesis catalyst as described above. Similarly, the zeolite or non-zeolitic molecular sieve may be present in the bifunctional catalyst as a whole in a lesser amount than the amount present in the dehydration catalyst. For example, the bifunctional catalyst may contain lower amounts of the methanol synthesis active metals as a whole, such as typically about 0.2% to about 30% by weight, typically about 0.5% to about 15% by weight, and typically about 1% to about 5% by weight, based on the weight of the bifunctional catalyst. Similarly, the bifunctional catalyst may contain zeolite or non-zeolitic molecular sieve as a whole in an amount of about 5% to about 90% by weight, about 10% to about 80% by weight, or about 35% to about 75% by weight, based on the weight of the bifunctional catalyst.

[0079] The LPG synthesis catalysts and LPG synthesis reaction conditions described herein are generally suitable for achieving H2, H2 conversion or CO conversion of at least about 20% (e.g., about 20% to about 99%, or about 20% to about 95%), at least about 30% (e.g., about 30% to about 99%, or about 30% to about 95%), or at least about 50% (e.g., about 50% to about 95%, or about 75% to about 95%). Whether these LPG synthesis conversion levels are based on H2 conversion or CO conversion may depend on which reactant in the LPG synthesis feedstock or in the synthesis gas intermediate is stoichiometrically limiting, given the LPG synthesis reaction chemistry. These LPG synthesis conversion levels may correspond to the "per pass" conversion levels obtained in a single pass of the LPG synthesis feedstock through the LPG synthesis stage or through the reactor of that stage. For the conversion of CH4 in the first reaction stage, these conversion levels may be calculated in a similar manner as described above. Preferably, these LPG synthesis conversion levels are based on CO conversion, more specifically on the conversion of CO in the synthesis gas intermediate or LPG synthesis feedstock (e.g. obtained after the intermediate operations described above). However, these LPG synthesis conversion levels may also be based on H2 and / or CO input to the first reaction stage, i.e. present in the gaseous feed mixture or present in the fresh make-up feedstock. Another important energy parameter for the LPG synthesis stage is the carbon selectivity to LPG hydrocarbons, which refers to the proportion of carbon in the LPG hydrocarbons, i.e. propane and / or butane (including butane isomers, isomers and n-butane), input to the LPG synthesis stage and present in the LPG synthesis effluent (e.g. present in CO and CO2). In representative embodiments, the carbon selectivity to LPG hydrocarbons is at least about 20% (e.g., about 20% to about 90%, or about 20% to about 75%), at least about 30% (e.g., about 30% to about 90%, or about 30% to about 75%), at least about 40% (e.g., about 40% to about 90%, or about 40% to about 75%), or even at least about 50% (e.g., about 50% to about 90%, or about 50% to about 75%).Carbon selectivity to propane may be at least about 10% (e.g., about 10% to about 60%, or about 10% to about 50%), at least about 15% (e.g., about 15% to about 60%, or about 15% to about 50%), or at least about 20% (e.g., about 20% to about 60%, or about 20% to about 50%). Carbon selectivity to butanes (isobutane and n-butane) can be at least about 5% (e.g., about 5% to about 45%, or about 5% to about 35%), at least about 10% (e.g., about 10% to about 45%, or about 10% to about 35%), or at least about 15% (e.g., about 15% to about 45%, or about 15% to about 35%). Preferably, these carbon selectivity levels are based on the total carbon (e.g., as CO, CO2) present in the synthesis gas intermediate or LPG synthesis feedstock (e.g., obtained after the intermediate operations described above). However, these carbon selectivity levels may optionally be based on the total carbon input to the first reaction stage (e.g., as CO, CO2, CH4), i.e., the carbons present in the gaseous feed mixture or in the fresh make-up feed.

[0080] The pass-by (or pass-by) yield of LPG hydrocarbons provides a further important measure of the stage energy of the LPG synthesis. This pass-by yield is the product of the pass-by CO conversion and the carbon selectivity to LPG hydrocarbons. In a representative process, the pass-by yield of LPG hydrocarbons (or LPG hydrocarbon yield) is at least about 15% (e.g., about 15% to about 85%, or about 15% to about 70%), at least about 25% (e.g., about 25% to about 85%, or about 25% to about 70%), at least about 35% (e.g., about 35% to about 85%, or about 35% to about 70%), or at least about 45% (e.g., about 45% to about 85%, or about 45% to about 70%). In some preferred embodiments, the pass-by yield of LPG hydrocarbons in the LPG synthesis stage is at least about 50%.

[0081] The desired H2 conversion and / or CO conversion in the LPG synthesis reactor(s), as well as other desired performance parameters, can be achieved by adjusting the LPG synthesis reaction conditions described above (e.g., LPG synthesis reaction temperature and / or LPG synthesis reaction pressure) and / or adjusting the weight hourly space velocity (WHSV). The LPG synthesis reaction conditions are, as described above, typically about 0.01 h 2 O 3 based on the combined weight of the methanol synthesis catalyst and the dehydration catalyst. -1 About 10 hours from -1 , typically about 0.05 hours -1 About 5 hours from -1 , generally about 0.1 hours -1 From about 1.5 hours -1 or weight hourly space velocity (WHSV), based on the weight of the bifunctional catalyst as described above. Conversion levels (e.g., CO conversion) can be increased, for example, by increasing the pressure and decreasing the WHSV, which have the effect of increasing the reactant concentration and reactor residence time, respectively.

[0082] Thus, embodiments of the present invention relate to a process for producing an LPG product from a synthesis gas containing H2 and CO, such as a synthesis gas intermediate or an LPG synthetic feedstock obtained after one or more intermediate operations on this intermediate. More specifically, any synthesis gas source can be used as an LPG synthetic feedstock in a representative LPG synthesis process, including an LPG synthetic feedstock having an H2:CO molar ratio representative of the synthesis gas intermediate described above. The synthesis gas intermediate or LPG synthetic feedstock can typically be produced by reforming and / or RWGS reactions, as described above. However, with respect to an LPG synthesis process that does not require a specific synthesis gas source, representative embodiments are directed to a process (e.g., an LPG synthesis stage) that does not necessarily require a certain upstream conversion step (e.g., a reforming process described herein). A representative process includes contacting any of the source synthesis gases described herein, more specifically any of the specific synthesis gas intermediates or LPG synthesis feedstocks described herein, with an LPG synthesis catalyst system as described herein, such as a mixture of (i) the methanol synthesis catalyst described above and (ii) a dehydration catalyst, which may, for example, comprise or substantially comprise (i) one or more methanol synthesis active metals selected from the group consisting of Cu, Zn, Al, Pt, Pd and / or Cr and optionally a solid support, as described above, and (ii) a zeolite or non-zeolitic molecular sieve as described above. The process includes converting H2 and CO, and optionally CO2, in the synthesis gas to hydrocarbons including propane and / or butane, which are provided in the LPG product. Another specific embodiment relates to a process for producing an LPG product comprising propane and / or butane, comprising: (a) contacting a gaseous feed mixture (e.g., in the case of a recycle operation, a gaseous feed mixture comprising a H2 / CO2-enriched fraction and a recycle portion of fresh make-up feed) with a reforming / RWGS catalyst in a reforming or RWGS stage to produce a synthesis gas intermediate comprising a H2 / CO mixture. The gaseous feed mixture can, for example, comprise CH4, CO2 and H2 in a combined amount of at least 30 mol %.The process may also include (b) in an LPG synthesis step, contacting at least a portion of the synthesis gas intermediate with an LPG catalyst system described herein to produce an LPG synthesis effluent.

[0083] Thus, an LPG product comprising propane and / or butane can be obtained after the step of converting the synthesis gas intermediate by LPG synthesis. The LPG product can correspond to the LPG synthesis effluent of the LPG synthesis reactor (e.g., the LPG product can be obtained without further processing of the LPG synthesis effluent), or the LPG product can be separated (e.g., fractionated) from the LPG synthesis effluent, for example as part of a propane and / or butane-enriched LPG synthesis effluent separated using techniques known to those skilled in the art. In either case, the LPG synthesis effluent can be obtained directly from the LPG synthesis stage (e.g., the LPG synthesis reactor of this stage). Thus, in a preferred embodiment, the process described herein comprises a step of separating the LPG product from the LPG synthesis effluent after the two reaction stages. In addition to this LPG product, the process can also comprise separating one or more other fractions from the LPG synthesis effluent, such as fractions depleted in the LPG hydrocarbons with respect to the LPG product. For example, such other fraction(s) may comprise H2 / CO2-enriched fractions, i.e., for example, H2 and CO-enriched fractions, for the LPG synthesis effluent and LPG product. For the LPG synthesis effluent and LPG product, such other fraction(s) may alternatively or in combination, i.e., water-enriched fractions. Both such H2 / CO2-enriched fractions and water-enriched fractions represent fractions that can be advantageously reused in the process after separation from the LPG synthesis effluent, as described in more detail below. The H2 / CO2-enriched fraction and the water-enriched fraction represent, respectively, gas (vapor) and liquid fractions separated from the LPG synthesis effluent, e.g., low boiling (more volatile) and high boiling (less volatile) fractions, respectively, compared to the LPG product.

[0084] According to certain embodiments, the LPG product (e.g., after separation) can include propane and butane in a combined amount of at least about 60 mol % (e.g., about 60 mol % to about 100 mol %), at least about 80 mol % (e.g., about 80 mol % to about 100 mol %), or at least about 90 mol % (e.g., about 90 mol % to about 99 mol %). Along with these combined amounts, or alternatively, the LPG product can include propane and / or butane in a standalone amount of at least about 25 mol % (e.g., about 25 mol % to about 85 mol %), at least about 40 mol % (e.g., about 40 mol % to about 80 mol %), or at least about 50 mol % (e.g., about 50 mol % to about 75 mol %). The balance of the LPG product can include all or substantially all of the pentane, or a combination of ethane and pentane. According to other specific embodiments, at least about 40% (e.g., from about 40% to about 95%), at least about 55% (e.g., from about 55% to about 95%), or at least about 70% (e.g., from about 70% to about 95%) of the gaseous feed mixture (e.g., the carbon content of the CH4 and / or CO2 present in the mixture), or the carbon content of the freshly made-up feed, forms the propane and / or butane of the LPG product. These percentages are expressed in weight % or mole % formulas. Once-through recycling operation / embodiment

[0085] The process for producing the LPG product described herein can be carried out (configured) by DC operation to input a gaseous feed mixture and take out the LPG product (optionally after separation from the LPG synthesis effluent, as described above) without recovering any part of the material obtained in the first or second reaction stage. In the case of a one-pass operation, the "gaseous feed mixture" and the "fresh make-up feed" are usually equivalent, and the conversion levels and product yields obtained from this process represent the conversion levels and product yields of one pass through the reforming and / or RWGS and LPG synthesis stages. As described above, some aspects of the present invention relate to LPG production processes or fresh make-up feed methods that allow for efficient management / conversion of the CO2 present in the gaseous mixture, which can be improved by a recycle operation. In particular, the recycle of CO2 (e.g., present in the H2 / CO2-rich fraction separable from the LPG synthesis effluent) back to the first stage (e.g., the reforming stage, e.g. the reforming / RWGS stage) and / or back to the second LPG synthesis stage for further reaction can promote its complete or substantially complete overall conversion. For example, in representative embodiments using a recycle operation as described herein, the total conversion of CO2 present in the fresh make-up feedstock (e.g., having the composition described above for the "gaseous feed mixture") can be at least about 90%, at least about 95%, or at least about 99%, with deviations from full or 100% conversion being due to losses of CO2 during purging from the gas recycle circuit used to control the accumulation of unwanted impurities in the circuit. That is, according to some embodiments, the CO2 introduced into the process in the gaseous feed mixture or fresh make-up feedstock can be recycled until it is substantially extinct. In the case of the aforementioned fractions that can be separated and / or recovered from the LPG synthesis effluent, the H2 / CO2-rich fraction and / or the water-rich fraction can be recycled, for example, to the first stage (e.g., the reforming stage, e.g., the reforming / RWGS stage) and / or the second LPG synthesis stage to obtain the important advantages described herein. In some cases, only the H2 / CO2-rich fraction or the recycled portion thereof is recycled.For example, a recycled portion of the H2 / CO2 enriched fraction can be recycled to the second stage, or a portion of the recycled portion can be recycled to the first and second stages.

[0086] An exemplary embodiment of a process 1 for producing an LPG product and utilizing recycle is shown in FIG. 1. As shown, a gaseous feed mixture 6 is fed to a reforming stage or RWGS stage 100, which may include one or more reforming / RWGS reactors for contacting the gaseous feed mixture 6 with a reforming / RWGS catalyst under reforming / RWGS conditions as described herein. The reactions occurring in the reforming stage or RWGS stage 100 produce a synthesis gas intermediate 8 that may undergo any one or more intermediate operations as described herein. For example, water, such as in the form of condensed liquid water 9, may be separated from the synthesis gas intermediate 8 to provide an LPG synthesis feed 10. Optionally, or in combination with removal of the condensed liquid water 9, a portion of the H2 / CO2 enriched fraction 14 of the LPG synthesis effluent 12 may be added to the synthesis gas intermediate 8 to provide an LPG synthesis feed 10. Adding a second portion 4b of this fraction has the effect of modifying the composition of the LPG synthetic feed 10, as shown in the figure, for example with respect to the synthesis gas intermediate 8, and more specifically with respect to the H2:CO ratio of the LPG synthetic feed. Whether or not any intermediate operations are performed, the LPG synthetic feed 10 (or the synthesis gas intermediate 8) or a part thereof is fed to an LPG synthesis stage 200, which may comprise one or more LPG synthesis reactors for contacting the LPG synthetic feed 10 (or the synthesis gas intermediate 8) with an LPG synthesis catalyst system under LPG synthesis conditions as described herein. The reactions occurring in the LPG synthesis stage 200 produce an LPG synthetic effluent 12 which may be obtained directly from the LPG synthesis stage 200. If necessary, after further intermediate operations such as cooling via a cooler 250, all or a part of the LPG synthetic effluent 12 may be fed to a separation stage 300 for separating the various fractions as described above. According to the particular embodiment shown in the figure, in addition to the LPG product 16 containing the LPG hydrocarbons described herein, the separated fractions may include (e.g., one or more other fractions) or may consist of an H2 / CO2 enriched fraction 14 and a water enriched fraction 18.The LPG product 16 is rich in propane and butane (based on the combined amounts of isobutane and n-butane) relative to the other fractions 14, 18 separated from the LPG synthesis effluent 12, and in preferred embodiments has the amounts of propane and / or butane as described above.

[0087] To improve overall CO2 conversion and management, at least a portion of the H2 / CO2 enriched fraction 14 can be recycled to upstream operations or stages, including the reforming or RWGS stage 100, and / or the LPG synthesis stage 200 of the process. Typically, for example, the recycled portion 4 containing the H2 / CO2 enriched fraction can be obtained after removing a purge 20 that limits the accumulation of unwanted impurities in the gas recycle circuit, especially non-condensable impurities, such as N2 and other impurities that may be present in the fresh make-up feed 2. Separation of the purge 20 provides a recycled portion 4 of the H2 / CO2 enriched fraction 14, which can be advantageously used to improve the performance of the overall process in various ways using a recycle gas compressor 350. For example, the recycled portion 4 can be recycled to either or both stages 100, 200 to increase the overall CO2 conversion of the process (e.g., beyond "per pass" or one-through CO2 conversion based on either stage operating alone or both operating together). Alternatively or in combination, the CO2 present in the H2 / CO2 enriched fraction 14 or in the recycle portion 4 thereof, when introduced into one or two stages 100, 200, in particular the LPG synthesis stage 200, can advantageously suppress or reduce the net yield of CO2 in this stage (e.g. due to the water-gas shift reaction). According to the specific embodiment shown in the figure, a first portion 4a of the recycle portion 4 can be recycled to the reforming or RWGS stage 100 (e.g. by combining with the feedstock 2) and / or a second portion 4b can be recycled to the LPG synthesis stage 200 (e.g. by combining with the synthesis gas intermediate 8 or the LPG synthesis feedstock 10). When recycling the H2 / CO2 enriched fraction 14 or any portion(s) thereof to a stage(s) of the process, the selection of a given recycle configuration can depend at least in part on the above considerations regarding increasing the total CO2 conversion rate of the process and / or suppressing the CO2 yield in a given stage. Upon reading this disclosure, one of ordinary skill in the art will understand the applicability of these and other considerations to a given process within the scope of the present invention.As is apparent from the above description, for purposes of this disclosure, the recycle portion 4 and any portions 4a, 4b to which it may be sent to a different location constitute "part of the H2 / CO2 enriched portion 14." Thus, for example, the gaseous feed mixture 6 may be fed to the reforming or RWGS stage 100 as a combination of fresh make-up feed 2 and a portion of the H2 / CO2 enriched fraction 14 (e.g., all of the recycle portion 4, or portion 4a of that portion), and optionally combined with a water-enriched fraction 18 that may be recycled using the recycle liquid pump 450.

[0088] According to certain embodiments, the fresh make-up feedstock 2 may include or be primarily composed of biogas, in such embodiments, the gaseous feedstock mixture 6 may include biogas present therein as a portion of the fresh make-up feedstock. Working Example

[0089] The following examples are provided as representative of the present invention and should not be construed as limiting the scope of the invention, as other equivalent embodiments are obvious in light of this disclosure and the appended claims.

[0090] An LPG synthesis catalyst system consisting of 1 gram of methanol synthesis catalyst (Cu / ZnO / Al2O3), 3 grams of beta zeolite and 1 gram of sand was tested for its activity in converting to 2:1 H2:CO molar ratio syngas. In separate tests in Examples 1-3, typical flow rates (ml / min) of syngas were used at 165, 110 and 55 ml / min, respectively, in combination with other LPG synthesis conditions of 2.1 MPa (300 psig) gauge pressure and 350 C (662 F) catalyst bed temperature. Table 1 below summarizes the carbon monoxide conversion and carbon selectivity of various components in the LPG synthesis effluent. [Table 1]

[0091] These results reveal that the exemplary LPG synthesis catalyst system is active under the above conditions for converting synthesis gas to LPG hydrocarbons (propane and isomers, n-butane isomers) with favorable CO conversions in the range of about 83-92% and carbon selectivities in the range of about 40-48%. Although the methanol synthesis and dehydration reaction mechanisms are believed to account for the production of these and other hydrocarbons, it is clear that methanol intermediates are present in the LPG synthesis effluent in trace or undetectable amounts. These results also show the effect of slowing down the rate of synthesis gas used as a representative LPG synthesis feedstock. In particular, slowing down the feed rate has the effect of increasing CO conversion, at least in part, due to increased reactor residence time (reduced WHSV). As one of ordinary skill in the art with knowledge of this disclosure will appreciate, the feed rate and other LPG synthesis conditions can be varied to achieve other ranges of conversion levels.

[0092] As a baseline experiment for comparison, the experiment with the normal synthesis gas flow rate of 165 ml / min described in Example 1 above was used. Specifically, the 2:1 H2:CO molar ratio synthesis gas used as the LPG synthesis feedstock in this experiment, i.e., the baseline feedstock, had an H2 / CO composition of about 67 mol% / 33 mol%, and the composition was changed accordingly in subsequent experiments to evaluate the performance difference with other LPG synthesis feedstocks. The compositions of these feedstocks are as follows: (A) (i) 50 mol% 2:1 H2:CO molar ratio syngas, and (ii) 50 mol% CO2-combined with Feed A to have an approximate H2 / CO2 / CO composition of 33.5 mol% / 50 mol% / 16.5 mol% (Example 4). (B) a 3:1 H2:CO molar ratio synthesis gas feedstock B (Example 5) with an approximate H2 / CO composition of 75 mol% / 25 mol%; (C) (i) syngas of 2:1 H2:CO molar ratio and (ii) LPG synthesis feed combined with a H2 / CO2 rich fraction of the LPG synthesis effluent and representing Feed C which is the LPG synthesis feed obtained from the recycle operation described herein, having an approximate H2 / CO2 / CO composition of 64 mol% / 20.5 mol% / 15.5 mol% (Example 6).

[0093] Thus, compared to the baseline feed, Feed A, Feed B and Feed C are comparative LPG synthesis feeds with (i) CO2 loading, (ii) H2 loading, and (iii) H2 and CO2 loading, as obtained from the recycle operation described herein. The conversion of these LPG synthesis feeds to LPG hydrocarbons and other components was evaluated at LPG synthesis conditions of 2.1 MPa (300 psi) gauge pressure and 350°C (662°F) catalyst bed temperature. These conditions were maintained in the presence of an exemplary LPG synthesis catalyst system of 1 g of methanol synthesis catalyst (Cu / ZnO / Al2O3), 3 g of beta zeolite, and 1 g of sand, and the LPG synthesis reaction was carried out. Table 2 below summarizes the carbon monoxide conversion and carbon selectivity of various components in the LPG synthesis effluent. [Table 2]

[0094] From the above results, it is clear that the addition of CO2 alone to obtain Feedstock A (Example 4) significantly reduces the rate of the LPG synthesis reaction and significantly reduces the CO conversion rate compared to the baseline feedstock. This effect is believed to be due to the dilution of the CO reactant and the resulting reduction in its concentration or partial pressure in the reaction mixture, as well as the inhibition of the LPG synthesis reaction by CO2. Therefore, if the LPG synthesis feedstock means a significant addition of CO2 to the synthesis gas, a significant increase in catalyst or a significant decrease in feed rate (throughput) may be required to determine the baseline CO conversion level obtained from a synthesis gas containing only pure H2- and CO. At the low CO conversion levels observed with Feedstock A compared to the baseline feedstock, the production of methane and ethane was also significantly increased, but an increase in selectivity to LPG hydrocarbons was observed. Regarding the addition of H2 alone to the baseline feedstock, according to the results obtained with Feedstock B (Example 5), the use of a synthesis gas with a 3:1 H2:CO molar ratio as the LPG synthesis feedstock did not result in a decrease in the reaction rate, since the CO conversion rate was comparable to the baseline feedstock. The addition of H2 alone cannot reduce the production of CO2 from the water-gas shift reaction. To some extent, the increase in H2 concentration may drive reactions that produce CO and HO, and the additional H2 may also be effective in replacing some of the CO, with the overall effect being that this additional H2 essentially acts as an inert gas.

[0095] However, surprisingly, the combined addition of CO2 and H2 to obtain Feed C (Example 6) compared to the baseline feed resulted in near 70% selectivity to LPG hydrocarbons and little or no CO2 production from the LPG synthesis reactor, despite poor conversion of CO. Despite the increase in selectivity to all C1-C4 hydrocarbons, the ratio of CH4 and ethane to LPG hydrocarbons remained substantially unchanged, i.e., no disproportionate increase was observed in these undesirable C1 and C2 hydrocarbons. Thus, these results suggest an unexpected increase in LPG hydrocarbon yields by the addition of H2 and CO2 to a synthesis gas that contains primarily H2 and CO (e.g., H2:CO molar ratios representing synthesis gas produced by dry reforming and / or steam reforming are in the range of, e.g., about 1.0 to about 3.0, about 1.0 to about 2.0, or about 2.0 to about 3.0). Such synthesis gas could be represented, for example, as a synthesis gas intermediate or a portion thereof, which can be extracted directly from the reactor used in the first stage (e.g., a reforming / RWGS stage, or a reforming stage such as a RWGS stage), or a product obtained from the first stage. Importantly, a convenient source of H2 and CO2 for this addition can be obtained according to certain embodiments as a H2 / CO2-rich fraction, which can be separated from the LPG synthesis effluent and advantageously recycled to achieve the important benefits described herein. In particular, the H2 / CO2-rich fraction could be recycled to the second LPG synthesis stage and / or optionally to any position upstream of the stage, for example as shown in the embodiment of method 1 shown in the figure and described above. In an exemplary embodiment, the H2 / CO2-rich fraction can be recycled by combining it with (i) the fresh make-up feed input to the first stage, (ii) the synthesis gas intermediate or a portion thereof input to the second stage, or some combination of (i) and (ii).

[0096] Since it was observed that the addition of H2 and CO2 reduces the CO conversion to some extent, measures were considered to compensate for this offset. From a reaction kinetics perspective, these measures include (a) increasing the residence time of the reactants by decreasing the yield of the second stage LPG synthesis step (and / or increasing the reactor size / catalyst weight) and / or (b) increasing the pressure of this stage to increase the reactant concentration. With regard to the second baseline case for evaluating these measures, an important consideration is the improvement of the selectivity to LPG hydrocarbons, which is obtained from feedstock C as a result of the combined addition of H2 and CO2, which can be achieved, for example, by operating the process with a recycle stream, as in the embodiments described herein. If high conversion is maintained, this increase in selectivity can lead to higher yields of LPG hydrocarbons, which are highly favorable in terms of the economics of the process. To better evaluate these possibilities, two further experiments were conducted using LPG synthesis feedstock corresponding to feedstock C (Example 6), but (a) the normal flow rate of the feedstock was reduced by 97 mL / min and the catalyst weight was increased by 6 g (Example 7), and (b) the LPG synthesis reaction pressure was further increased by 3.8 MPa (550 psi) (Example 8). The catalyst bed temperature was maintained at 350°C (662°F) and the catalyst composition was unchanged, since the catalyst contained 25 wt% methanol synthesis catalyst (Cu / ZnO / Al2O3) and 75 wt% zeolite beta. The carbon monoxide conversion and carbon selectivity of various components in the LPG synthesis wastewater are summarized in Table 3 below. [Table 3]

[0097] A comparison of Examples 6 and 7 shows that the CO conversion can be increased by increasing the residence time of the reactants (reducing the yield or weight hourly space velocity), but not necessarily with a corresponding increase in LPG yield. Conversely, depending on other LPG synthesis conditions, including the specific feed composition, an increase in CO conversion may appear primarily as an increase in CO2 yield. However, the important thing is that the results of Example 8 show that an increase in LPG synthesis reaction pressure allows the process to operate at a per-pass LPG yield of more than 50%, due to the increase in conversion caused by the decrease in carbon selectivity to CO2 and the increase in carbon selectivity to LPG hydrocarbons.

[0098] In general, various aspects of the present invention relate to a method for converting a low-value gaseous feed mixture into an LPG product using reforming and / or RWGS reactions, for example, a process including propane and / or butane with carbon from renewable sources such as CH4 and CO2, the main components of biogas. Additional processing in a second reaction stage includes LPG synthesis. Those skilled in the art, aware of this disclosure, will recognize that these processes can be modified in various ways to obtain these and other advantages without departing from the scope of the disclosure. Accordingly, it should be understood that features of the present disclosure can be modified and / or substituted without departing from the scope of the disclosure. The specific embodiments shown and described herein are used for illustrative purposes only and are not intended to limit the invention as set forth in the appended claims.

Claims

1. 1. A process for producing an LPG product comprising propane and / or butane, comprising: (a) In the reforming or RWGS stage, (i) CH ４ and CO ２ or (ii) H ２ and CO ２ contacting a gaseous feed mixture containing primarily H with a reforming / RWGS catalyst to form H ２ producing a synthesis gas intermediate comprising a CO / CO mixture; (b) converting said synthesis gas intermediate to said LPG product in an LPG synthesis stage.

2. The gaseous feed mixture comprises: (i) at least about 75 mol % total amount of CH ４ and CO ２ ,or (ii) at least about 75 mol % total amount of H ２ and CO ２ Including, The process of claim 1.

3. The gaseous raw material mixture contains CO, H ２ O, and O ２ containing less than about 10 mol % of one or more of the following, independently or in a combined amount: The process of claim 1.

4. the gaseous feed mixture comprises biogas; The process of claim 1.

5. The LPG product is separated from an LPG synthesis effluent obtained from an LPG synthesis reactor of the LPG synthesis stage. The process according to any one of claims 1 to 4.

6. the LPG product comprising at least about 80 mole percent combined propane and butane; The process of claim 5.

7. The gaseous feed mixture is a mixture of H separated from the LPG synthesis effluent. ２ / CO ２ including a recycled portion of the enriched fraction, The process of claim 5.

8. The conversion in step (b) is carried out via a methanol synthesis reaction mechanism. The process of claim 1.

9. The step of converting the synthesis gas intermediate to the LPG product comprises converting the synthesis gas intermediate to (i) a catalyst mixture comprising a methanol synthesis catalyst and a dehydration catalyst; or (ii) A bifunctional catalyst having a methanol synthesis functional component and a dehydration functional component. contacting the LPG synthesis catalyst system comprising The process of claim 1.

10. the methanol synthesis catalyst or the methanol synthesis functional component contains one or more methanol synthesis active metals selected from the group consisting of Cu, Zn, Al, Pt, Pd, and Cr; 10. The process of claim 9.

11. The dehydration catalyst or the dehydration functional component comprises a zeolite or a non-zeolitic molecular sieve; 10. The process of claim 9.

12. the gaseous feed mixture (i) CH ４ and CO ２ or (ii) H ２ and CO ２ at least about 70% of the feed carbon content forms propane and / or butane; The process according to any one of claims 1 to 4.

13. an LPG product comprising propane and / or butane, said LPG product having at least about 70% renewable carbon content; LPG product.

14. At least about 20% of the total carbon content of the LPG product is CO ２ The origin is, 14. The LPG product of claim 13.

15. The CO ２ is contained in biogas, 15. The LPG product of claim 14.

16. 1. A process for producing an LPG product comprising propane and / or butane, comprising: (a) in the modification or RWGS stage, a total amount of at least 30 mol % of CH ４ , CO ２ and H ２ contacting a gaseous feed mixture containing H with a reforming / RWGS catalyst to form a ２ producing a synthesis gas intermediate comprising a CO / CO mixture; (b) in an LPG synthesis stage, contacting the synthesis gas intermediate with an LPG catalyst system to produce an LPG synthesis effluent; (c) separating an LPG product from the LPG synthesis effluent; process.

17. from said LPG synthesis effluent (i) H ２ / CO ２ Enriched fraction and (ii) further comprising the step of separating one or both of the water-enriched fractions; 17. The process of claim 16.

18. (i) H ２ / CO ２ Enriched fraction and (ii) water-enriched fraction recycling one or both of the above to the reforming stage or the RWGS stage; or (i) H ２ / CO ２ further comprising recycling one or both of the (i) enriched fraction and (ii) the water-enriched fraction to the LPG synthesis stage; 18. The process of claim 17.

19. the gaseous feed mixture comprises biogas, the biogas being present in the gaseous feed mixture as a fresh make-up portion of the gaseous feed mixture; The process according to any one of claims 16 to 18.

20. the reforming / RWGS catalyst is disposed in a catalyst bed volume within an electrically heated reforming reactor; 17. The process of claim 1 or 16.

21. 1. A process for producing an LPG product comprising propane and / or butane, comprising: ２ and CO, and optionally CO ２ contacting an LPG synthesis feedstock containing the compound with an LPG synthesis catalyst system, wherein the LPG synthesis catalyst system comprises: (i) a methanol synthesis catalyst; (ii) a dehydration catalyst; H in synthesis gas ２ and at least a portion of CO, and optionally CO ２ converting at least a portion of the above to hydrocarbons including propane and / or butane, which are provided in the LPG product.

22. 22. The process of claim 21, wherein the methanol synthesis catalyst and / or the dehydration catalyst comprises yttrium in elemental or compound form.

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