Processes for fischer-tropsch conversion of carbon dioxide to condensable hydrocarbons

Abstract

The present disclosure related generally to a process for preparing hydrocarbons. The process includes providing a first feed stream comprising carbon dioxide and hydrogen in a first reaction zone, contacting the first feed stream with an iron-based FT catalyst material under conditions sufficient to form a first product stream comprising C5+ hydrocarbons, water, carbon dioxide and hydrogen; in a first separation zone, separating at least part of the water of the first product stream to provide a first separated water-rich product stream and a first separated water-poor product stream comprising carbon dioxide and hydrogen; providing a second feed stream comprising at least a portion of the carbon dioxide and in second reaction zone, contacting the second feed stream with an iron-based FT catalyst material under conditions sufficient to form an second product stream comprising C5+ hydrocarbons, water, carbon dioxide and hydrogen. Additional cycles of conversion and separation of water can subsequently be performed.

Description

PROCESSES FOR FISCHER-TROPSCH CONVERSION OF CARBON DIOXIDE TO CONDENSABLE HYDROCARBONSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority U.S. provisional application number 63 / 616,379, filed December 29, 2023 and European Patent application number 24166566.0, filed March 26, 2024, each of which is incorporated by reference herein in its entirety.1 _ Field

[0002] The present disclosure relates generally to processes for the Fischer-Tropsch synthesis of hydrocarbons from carbon dioxide.2. _ Technical Background

[0003] The conversion of synthesis gas (i.e. , a mixture of carbon monoxide and hydrogen, also known as syngas) into hydrocarbons by the Fischer-Tropsch process has been known for decades, but has historically lagged in performance compared to other hydrocarbon synthesis techniques. The growing importance of alternative energy sources has resulted in renewed interest in the Fischer-Tropsch (FT) process as it allows a direct and environmentally-acceptable route to high-quality fuels and feedstock chemicals.

[0004] FT processes are known for producing linear hydrocarbons, as well as oxygenates, that can be useful in fuels and can also serve as valuable feedstock chemicals. The hydrocarbon fuel derived from FT processes is typically better able to meet increasingly stringent environmental regulations compared to conventional refinery-produced fuels, as FT-derived fuels typically have lower contents of sulfur, nitrogen, and aromatic compounds, which contribute to the emission of potent pollutants such as SO2, NOX, and particulates. Alcohols, olefins and other oxygenates obtained may also be used as reagents in other processes, such as in the synthesis of lubricants.

[0005] Currently, cobalt-based catalysts are the primary type of catalysts used in FT processes; they generally yield linear paraffins as primary products. Iron-based catalyst materials are also known, and can be lower in cost compared to cobalt-based catalyst materials. Iron-catalysed FT typically produces as part of the hydrocarbon product a significant amount of long-chain oxygenates and long-chain a-olefins, which in many cases are desirable products. However, in contrast to cobalt, iron-based catalysts generally exhibit high water gas shift (WGS) activity. The water gas shift reaction competes with the Fischer-Tropsch process by converting CO and H2O to CO2 and hydrogen, as shown below:C02conversion on the iron-based FT catalyst can convert CO2to CO for conversion through to hydrocarbons, but this is limited by the WGS equilibrium i.e., in-situ formed CO and H2O can react back to a certain extent to CO2 and H2, limiting the CO2 conversion to a low level. Accordingly, higher water gas shift activity can lead to high CO2 yields and lower selectivity of the conversion of feedstock carbon to C5+ hydrocarbons, which are the generally-desired FT products. As such, the main challenge in iron-based FT process are to obtain good CO2 conversion towards C5+ hydrocarbons while minimizing the undesirable effects of the high water-gas shift activity of iron-based catalysts.

[0006] As such, there is a need to provide improved iron-based FT processes.SUMMARY

[0007] In one aspect, the present disclosure provides a process for preparing hydrocarbons. The process includes providing a first feed stream comprising carbon dioxide and hydrogen; in a first reaction zone, contacting the first feed stream with an iron-based FT catalyst material under conditions sufficient to form a first product stream comprising C5+ hydrocarbons, water, carbon dioxide and hydrogen; in a first separation zone, separating at least part of the water of the first product stream to provide a first separated water-rich product steam and a first separated water-poor product stream comprising carbon dioxide and hydrogen; providing a second feed stream comprising at least a portion of the carbon dioxide and at least a portion of the hydrogen of the first separated water-poor product stream; and performing n times, in which n is 0 or an integer that is 1 or more, in n sequentially- arranged pairs of zones each comprising a separation zone and a reaction zone, the following set of operations n times, with each iteration sequentially taking an integer value of x from 1 to n when n is not zero: in the (x+1)th reaction zone, contacting the (x+1)th feed stream with an ironbased FT catalyst material under conditions sufficient to form an (x+1)th product stream comprising C5+ hydrocarbons, water, carbon dioxide and hydrogen; in the (x+1)th separation zone, separating at least part of the water of the (x+1)th product stream to provide an (x+1)th separated water-rich product steam and an (x+1)th separated water-poor product stream comprising carbon dioxide and hydrogen; andproviding an (x+2)th feed stream comprising at least a portion of the carbon dioxide and at least a portion of the hydrogen of the (x+1)th separated water-poor product stream; and in an (n+2)th reaction zone, contacting the (n+2)th feed stream with an iron-based FT catalyst material under conditions sufficient to form an (n+2)th product stream comprising C5+ hydrocarbons, water, carbon dioxide and hydrogen.

[0008] In particular embodiments as described herein, in the first reaction zone and subsequent reaction zones (e.g., (x+1)th and (n+2)th reaction zones), the contacting of the feed steams with an iron-based FT catalyst material is conducting in the substantial absence of a reverse water-gas shift catalyst material.

[0009] In particular embodiments as described herein, the process as described herein has a single-pass CO2 conversion of at least 70%.BRIEF DESCRIPTION OF FIGURES

[0010] The accompanying drawings are included to provide a further understanding of the methods of the disclosure, and are incorporated in and constitute a part of this specification. The drawings are not necessarily to scale, and sizes of various elements may be distorted for clarity. The drawings illustrate one or more embodiment(s) of the disclosure and together with the description serve to explain the principles and operation of the disclosure.

[0011] FIG. 1 is a schematic of a process for performing a Fischer-Tropsch process as described herein.

[0012] FIG. 2 is a schematic of a process for performing a Fischer-Tropsch process as described herein.

[0013] FIG. 3 is a schematic of a process for performing a Fischer-Tropsch process as described herein.

[0014] FIG. 4 is a schematic of a process for performing a Fischer-Tropsch process as described herein.

[0015] FIG. 5 is a schematic of a process for performing a Fischer-Tropsch process as described herein.

[0016] FIG. 6 is a schematic of a process for performing a Fischer-Tropsch process as described herein.

[0017] FIG. 7 is a graph of the single-pass CO2 conversion of the Fischer-Tropsch process as described herein.DETAILED DESCRIPTION

[0018] The present disclosure is concerned with iron-based FT processes for converting CO2 to hydrocarbons. One of the challenges associated with using CO2 in the feed stream of FT processes is to activate the CO2at reasonable temperatures to form CO for conversion into hydrocarbons. Here, the present inventors note that there is further H2O produced during the Fischer-Tropsch reaction, shown below:CO + 2 H2-> [-CH2-] + H2OThe present inventors have noted that this water formed by the Fischer-Tropsch reaction can be especially problematic, in that it can push the water-gas shift equilibrium toward formation of CO2 from CO, which is undesirable from the standpoint of conversion to desirable products. Further, the higher degree of Fischer-Tropsch conversion, the more water will be present, and the worse this problem will be.

[0019] Here, the present inventors provide a process that increases CO2 conversion by using multiple iron-based FT stages with carbon dioxide and hydrogen being passed between the stages. The processes use inter-stage separations to remove water between stages, so as to maintain generally lower water concentrations as the process progresses, thus reducing the degree of water-gas shift of CO to CO2. In doing so, the present inventors have found that this scheme allows for an incremental increase of CO2 conversion with each interstage separation zone, and overall converts more of the feed carbon dioxide to desired hydrocarbon products.

[0020] Accordingly, in one aspect, the present disclosure provides a process for preparing hydrocarbons from carbon dioxide. The process includes providing a first feed stream comprising carbon dioxide and hydrogen in a first reaction zone, contacting the first feed stream with an iron-based FT catalyst material under conditions sufficient to form a first product stream comprising C5+ hydrocarbons, water, carbon dioxide and hydrogen; in a first separation zone, separating at least part of the water of the first product stream to provide a first separated water-rich product steam and a first separated water-poor product stream comprising carbon dioxide and hydrogen; providing a second feed stream comprising at least a portion of the carbon dioxide and at least a portion of the hydrogen of the first separated water-poor product stream; and performing n times, in which n is 0 or an integer that is 1 or more, in n sequentially-arranged pairs of zones each comprising a separation zone and a reaction zone, the following set of operations n times, with each iteration sequentially taking an integer value of x from 1 to n when n is not zero: in the (x+1)th reaction zone, contacting the (x+1)th feed stream with an iron-based FT catalyst material under conditions sufficient to form an (x+1)th product stream comprising C5+ hydrocarbons,water, carbon dioxide and hydrogen; in the (x+1)th separation zone, separating at least part of the water of the (x+1)th product stream to provide an (x+1)th separated water-rich product steam and an (x+1)th separated water-poor product stream comprising carbon dioxide and hydrogen; and providing an (x+2)th feed stream comprising at least a portion of the carbon dioxide and at least a portion of the hydrogen of the (x+1)th separated water-poor product stream; and in an (n+2)th reaction zone, contacting the (n+2)th feed stream with an ironbased FT catalyst material under conditions sufficient to form an (n+2)th product stream comprising C5+ hydrocarbons, water, carbon dioxide and hydrogen.

[0021] As described above, the present inventors have found that to increase overall CO2 conversion, having n sequentially arranged pairs of zones each comprising a separation zone and a reaction zone, as described herein, can be advantageous. For example, in some embodiments as described herein, n is 0. A schematic of the process when n is 0 is shown in FIG. 1. In the process 100 of FIG. 1 , a first feed stream 111a comprising carbon dioxide and hydrogen is provided to a first reaction zone 110a and contacted with an ironbased FT catalyst material 113a under conditions sufficient to form a first product stream 112a comprising C5+ hydrocarbons, water, carbon dioxide, and hydrogen. A first separation zone, 116, separates at least part of the water of the first product stream 112a to provide a first separated water-rich product stream 117 and a first separated water-poor product stream 118 comprising carbon dioxide and hydrogen. In the process 100 of FIG. 1, a second feed stream 111b comprises at least a portion of the carbon dioxide and at least a portion of the hydrogen of the first separated water-poor product stream 118, and in an (n+2)th reaction zone (e.g., a second reaction zone) 110b, the (n+2)th feed stream 111b is contacted with an iron-based FT catalyst material 113b under conditions sufficient to form an (n+2)th product stream 112b comprising C5+ hydrocarbons, water, carbon dioxide, and hydrogen.

[0022] In various other embodiments, n is greater than 0. For example, in some embodiments, n is an integer that is 1 or more. In some embodiments as described herein, n is in the range of 1-10, e.g., in the range of 1-7, or 1-5, or 1-3. In some embodiments as described herein, n is in the range of 2-10, e.g., in the range of 2-7, or 2-5, or 2-4. In some embodiments as described herein, n is in the range of 3-10, e.g., in the range of 3-7, or 3-5.

[0023] In some embodiments as described herein, n is 1. A schematic of the process when n is 1 is shown in FIG. 2. In the process 200 of FIG. 2, a first feed stream 211a comprising carbon dioxide and hydrogen is provided to a first reaction zone 210a and contacted with an iron-based FT catalyst material 213a under conditions sufficient to form a first product stream 212a comprising C5+ hydrocarbons, water, carbon dioxide, andhydrogen. A first separation zone, 216a, separates at least part of the water of the first product stream 212a to provide a first separated water-rich product stream 217a and a first separated water-poor product stream 218a comprising carbon dioxide and hydrogen. If the water-rich product stream is separated by condensation (e.g., a so-called “knockout”), then it will typically include the desired hydrocarbon product and condense as a two phase mixture of an aqueous phase and a hydrocarbon phase; this can be separated in a subsequent process step as described below. In the process 200 of FIG. 2, a second feed stream 211b comprises at least a portion of the carbon dioxide and at least a portion of the hydrogen of the first separated water-poor product stream 218, and in an (x+1)th reaction zone (e.g., a second reaction zone) 210b, the (x+1)th feed stream 211b is contacted with an iron-based FT catalyst material 213b under conditions sufficient to form an (x+2)th product stream 212b comprising C5+ hydrocarbons, water, carbon dioxide, and hydrogen. A (x+1)th separation zone, 216b, separates at least part of the water of the (x+1)th product stream 212b to provide a (x+1)th separated water-rich product stream 217b and a (x+1)th separated waterpoor product stream 218b comprising carbon dioxide and hydrogen. In the process 200 of FIG. 2, a (n+2)th (e.g., a third) feed stream 211c comprises at least a portion of the carbon dioxide and at least a portion of the hydrogen of the (x+1)th separated water-poor product stream 218b, and in an (n+2)th reaction zone (e.g., a third reaction zone) 210c, the (n+2)th feed stream 211c is contacted with an iron-based FT catalyst material 213c under conditions sufficient to form an (n+2)th product stream 212c comprising C5+ hydrocarbons, water, carbon dioxide, and hydrogen.

[0024] As used herein, a “feed stream” is used to mean the total material input to a process step, regardless of whether provided in a single physical stream or multiple physical streams, and whether through a single inlet or multiple inlets. Similarly, a “product stream” is used to mean the total material output from a process step, regardless of whether provided in a single physical stream or multiple physical streams, and whether through a single reactor outlet or multiple reactor outlets. For example, hydrogen and carbon dioxide of the first feed stream can be provided to the iron-based FT catalyst material in a single physical stream (e.g., in a single pipe to reactor 110), or in multiple physical streams (e.g., separate inlets for carbon dioxide and H2, or one inlet for fresh carbon dioxide and H2 and another for recycled carbon dioxide and / or H2). Similarly, a “product stream” is used to mean the total material output from a process step, regardless of whether provided in a single physical stream or multiple physical streams, and whether through a single outlet or multiple outlets. Additionally, as used herein, feed stream(s) refers to the first, second, (x+2)th, and (n+2)th feed streams unless otherwise noted. Similarly, product stream(s) refers to the first, second, (x+1)th, and (n+2)th product streams unless otherwise noted. Reaction zone(s) refers to thefirst, (x+1)th, and (n+2)th reaction zones and separation zone(s) refers to the first and (x+1)th separation zones unless otherwise noted.

[0025] As described above, the feed streams (e.g., first, second, (x+1)th, and (n+2)th feed streams) contains both H2 and CO2 (e.g., provided to a reaction zone in a single physical stream or multiple physical streams). In various embodiments as otherwise described herein, the molar ratio of H2 to CO2 in at least one of the feed streams (e.g., in each feed stream) as described herein is at least 0.1 :1 , e.g., at least 0.5:1. In some embodiments, the molar ratio of H2 to CO2 in at least one of the feed streams (e.g., in each feed stream) as described herein is at least 0.9:1 , e.g., at least 1 :1 or at least 1.5:1. In some embodiments, the molar ratio of H2 to CO2 in at least one of the feed streams (e.g., in each feed stream) as described herein is no more than 20:1 , e.g., no more than 15:1 or no more than10:1. For example, in some embodiments, the molar ratio of H2 to CO2 in at least one of the feed streams (e.g., in each feed stream) as described herein is in the range of 1-10, e.g., 2-10 or 2-5. In some embodiments as described herein, the molar ratio of H2 to CO2 in at least one of the feed streams (e.g., in each feed stream) is in the range of 1.5-4.5, e.g., 2- 4.5, or 2.5-4.5, or 1.5-4, or 2-4, or 2.5-4, or 1.5-3.5, or 2-3.5, or 2.5-3.5, or 1.5-3, or 2-3. The person of ordinary skill in the art will provide a desired ratio of H2:CO2 in the feed stream(s), based on the disclosure herein, that provides a desirable conversion and selectivity; excess H2 can, if consistent with a desirable conversion and selectivity, be provided to flow through the system and provide a product stream with a desirable ratio of H2 to CO for a (x+1)th process.

[0026] Other gases may also be included in the feed stream(s). For example, in some embodiments, at least one of the feed streams (e.g., each feed stream) further comprises CO. The person of ordinary skill in the art will provide a desired ratio of hydrogen to carbon monoxide and carbon dioxide (i.e. , oxides of carbon), based on the disclosure herein, that provides a desirable conversion and selectivity. As discussed above, iron-based FT catalyst material are known to be highly active for the WGS / rWGS reaction. The present inventors hypothesize that including CO in the feed stream(s) can provide a compromise between the rWGS reaction and the FT reaction to provide the desired hydrocarbons. For example, in some embodiments as described herein, the feed stream(s) has a ratio of hydrogen to oxides of carbon in the range of 1 :1 to 6:1 , e.g., 1.5:1 to 3:1.

[0027] In some embodiments of the disclosure as otherwise described herein, at least one of the feed streams (e.g., each feed stream) further comprises one or more inert gases. For example, in some embodiments, at least one of the feed streams (e.g., each feed stream) further comprises nitrogen and / or methane. For example, it can be desirable toperform the iron FT reaction step in the presence of a significant amount of inerts (i.e., components that are not H2 or CO2). For example, in various embodiments, at least one of the feed streams (e.g., each feed stream) includes up to 80 mol% of one or more inerts, e.g., in the range of 3-80 mol%, or 5-80 mol%, or 10-80 mol%, or 15-80 mol%, or 30-80 mol% of one or more inerts. In various embodiments, at least one of the feed streams (e.g., each feed stream) includes up to 70 mol% inerts, up to 60 mol% inerts, or up to 50 mol% inerts, e.g., 3-70 mol%, or 5-70 mol%, or 10-70 mol%, or 15-70 mol%, or 30-70 mol%, or 3-60 mol%, or 5-60 mol%, or 10-60 mol%, or 15-60 mol%, or 30-60 mol%, or 3-50 mol%, or 5-50 mol%, or 10-50 mol%, or 15-50 mol%, or 30-50 mol% inerts. In various embodiments, at least one of the feed streams (e.g., each feed stream) includes up to 80% of one or more inerts selected from methane and nitrogen, e.g., up to 70 mol%, up to 60 mol%, or up to 50 mol%, or 15-70 mol%, or 30-70 mol%, or 15-60 mol%, or 30-60 mol%, or 15-50 mol%, or 30- 50 mol%.

[0028] It can be desirable to reduce the amount of water present in the feed stream(s) to control the WGS / rWGS activity of the iron-based catalyst material. Accordingly, in various embodiments as otherwise described herein, at least one of the feed streams (e.g., each feed stream) has a water content of no more than 10 mol%, e.g., or no more than 2 mol%, or no more than 0.5 mol%. Maintaining a low amount of water can have additional benefits, such as improving catalyst material stability.

[0029] As described above, the process described herein provides high CO2 conversion. As used herein, a “conversion” is a molar fraction of a relevant component feed that is reacted (be it to desirable products or undesirable species). In various embodiments of the present disclosure as described herein, at least one reaction zone (e.g., each reaction zone) has a CO2 conversion of at least 5%, e.g., at least 10%, or at least 20%. For example, in some embodiments, at least one reaction zone (e.g., each reaction zone) has a CO2 conversion of at least 30%, e.g., at least 40%, or at least 50%, or at least 60%. In various embodiments of the present disclosure as described herein, at least one reaction zone (e.g., each reaction zone) has a CO2 conversion of no more than 90%, e.g., no more than 80%, or no more than 70%. For example, in some embodiments, at least one reaction zone (e.g., each reaction zone) has a CO2 conversion of no more than 65%, e.g., no more than 60%. For example, in various embodiments as otherwise described herein, the CO2 conversion if at least one reaction zone (e.g., each reaction zone) is in the range of 10-90%, e.g., 10-80%, or 10-70%, or 10-60%, or 10-65%, or 20-90%, or 20-80%, or 20-70%, or 20-60%, or 20- 65%, or 30-90%, or 30-80%, or 30-70%, or 30-60%, or 30-65%, or 40-90%, or 40-80%, or 40-70%, or 40-60%, or 40-65%. The person of ordinary skill in the art will, based on the disclosure herein, operate at a degree of conversion that provides a desirable product. Insome embodiments as described herein, the process has a single-pass conversion of CO2 of at least 70%. As used here-in, single-pass conversion is the conversion across all of the reaction zones in 1 cycle. For example, when n is 1 , there are three reaction zones, and the single-pass conversion would be the conversion over these three zone. In various embodiments as described herein, the process has a single-pass conversion of CO2 of at least 75%, at least 80%, at least 85%, or at least 90%.

[0030] The process as described herein includes contacting an iron-based FT catalyst material with the feed stream(s) to perform an FT reaction. Notably, the present inventors have determined that the iron FT catalyst materials, under the conditions described herein, can provide desirably high C5+ selectivities. The Fischer-Tropsch process is typically used to make C5+ hydrocarbons, for example, unsubstituted C5+ hydrocarbons (e.g., alkanes and alkenes) and / or oxygenated C5+ hydrocarbons (e.g., C5+ alcohols, aldehydes, ketones, carboxylic acids). For example, in various embodiments as described herein, the contacting of the feed stream(s) with the iron-based FT catalyst material in at least one reaction zone (e.g., each reaction zone) is conducted with a C5+ selectivity (i.e. , for all C5+ species) of at least 40%, e.g., at least 50%, or at least 60%. For example, in some embodiments, the selectivity for C5+ alkanes is at least 40%, e.g., at least 50%, or at least 60% in at least one reaction zone (e.g., each reaction zone). In some embodiments, the contacting of the ironbased FT catalyst material with the feed stream(s) in at least one reaction zone (e.g., each reaction zone) is performed with a C2-4 selectivity of no more than 30%, e.g., no more than 25%, or no more than 20%. In some embodiments, the contacting of the iron-based FT catalyst material with the feed stream(s) in at least one reaction zone (e.g., each reaction zone) is performed with a methane selectivity of no more than 20%, e.g., no more than 15%, or no more than 10%, or no more than 5%. In some embodiments, the contacting of the iron-based FT catalyst material with the feed stream(s) in at least one reaction zone (e.g., each reaction zone) is performed with a C2-8 oxygenate selectivity of no more than 30%, e.g., no more than 25%, or no more than 20%. In some embodiments, the contacting of the ironbased FT catalyst material with the feed stream(s) in at least one reaction zone (e.g., each reaction zone) is performed with a C2-8 oxygenate selectivity of no more than 15%, e.g., no more than 10%, or no more than 5%.

[0031] In some embodiments as described herein, the iron-based FT catalyst materials under the conditions described herein may have some selectivity for CO. For example, in some embodiments as described herein, the contacting of the feed stream(s) with the iron-based FT catalyst material in at least one reaction zone (e.g., each reaction zone) is conducted with an overall CO selectivity of at least 10%. For example, in some embodiments as described in, the contacting in at least one reaction zone (e.g., eachreaction zone) is conducted with an overall CO selectivity of at least 15% or at least 20%. In some embodiments as disclosure as described herein, the contacting of the feed stream(s) with the iron-based FT catalyst material in at least one reaction zone (e.g., each reaction zone) is conducted with an overall CO selectivity of no more than 50%, e.g., no more than 40%, or no more than 30%.

[0032] One of the main challenges of using CO2 in the feed stream of the FT process is to activate the CO2 at economical and energy efficient conditions. Conventional rWGS reactions used to active CO2 often require high temperatures and pressures, leading to a more energy intensive and expensive process. Advantageously, the iron FT processes described herein can be performed at temperatures that are lower than temperatures used in many conventional reverse water-gas shift processes. As such, in some embodiments, contacting of at least one feed stream (e.g., each feed stream) with the iron-based FT catalyst material in the reaction zone is conducted at a temperature in the in the range of 200-500°C. For example, in various embodiments, the contacting is conducted at an iron FT temperature in the range of 200-450 °C, e.g., 200-400 °C, or 200-350 °C, or 225-500 °C, or 225-450 °C, or 225-400 °C, of 225-350 °C, or 250-500 °C, or 250-450 °C, or 250-400 °C, or 250-350 °C, or 260-500 °C, or 260-450 °C, or 260-400 °C, or 260-350 °C, or 300-500 °C, or 300-450 °C, or 300-400 °C, or 300-350 °C. The present inventors have noted that operation at these temperatures can provide for lower energy demand, as well as for facile integration with a subsequent process steps. In some embodiments as described herein, in subsequent reaction zones (e.g., each (x+1)th reaction zone), the contacting of the feed streams with the iron-based FT catalyst materials is conducted at the same temperature. In some embodiments as described herein, in subsequent reaction zones (e.g., each (x+1)th reaction zone), the contacting of the feed streams with the iron-based FT catalyst materials is conducted at different temperatures. For example, in some embodiments as described herein, in subsequent reaction zones (e.g., each (x+1)th reaction zone), the contacting of the feed streams with the iron-based FT catalyst materials is conducted at increasing temperatures. That is, in a first reaction zone, the contacting occurs at a temperature less than the contacting temperature of the (x+1)th reaction zone, and in the (x+1)th reaction zone, the contacting occurs at a temperature less than the contacting temperature of the (n+2)th reaction zone.

[0033] Additionally, the iron FT processes described herein can be performed at a variety of pressures, as would be appreciated by the person of ordinary skill in the art. In some embodiments of the present disclosure, the contacting the feed stream(s) with an ironbased FT catalyst material in at least one reaction zone (e.g., each reaction zone) is conducted at a pressure of at least 1 barg, e.g., at least 5 barg, or at least 10 barg. In someembodiments as described herein, the contacting the feed stream(s) with an iron-based FT catalyst material in at least one reaction zone (e.g., each reaction zone) is conducted at a pressure of at least 20 barg, e.g., at least 30 barg, or at least 35 barg. In some embodiments as described herein, the pressure in the first reaction zone is at least 20 barg, e.g., at least 30 barg, or at least 35 barg. In various embodiments of the present disclosure, the contacting is conducted at an iron FT pressure in the range of 1 to 100 barg. For example, the contacting is conducted at an iron FT pressure in the range of 1 to 80 barg, or 1 to 70 barg, or 1 to 60 barg, 5 to 100 barg, 5 to 80 barg, 5 to 70 barg, 5 to 60 bag, or 10 to 100 barg, 10 to 80 barg, or 10 to 70 barg, 10 to 60 barg. In some embodiments as described herein, in subsequent reaction zones (e.g., each (x+1)th reaction zone), the contacting of the feed streams with the iron-based FT catalyst materials is conducted at the same pressure. In some embodiments as described herein, in subsequent reaction zones (e.g., each (x+1)th reaction zone), the contacting of the feed streams with the iron-based FT catalyst materials is conducted at different pressures.

[0034] The iron FT processes described herein can be performed at a variety of GHSV (gas hourly space velocity), as would be appreciated by the person of ordinary skill in the art. As such, the GHSV for performing the iron FT process in at least one reaction zone (e.g., each reaction zone) is not particularly limited. For example, in some embodiments of the present disclosure, the contacting the feed stream(s) with an iron FT-based catalyst material is conducted at an iron FT GHSV in the range of 200 to 10,000 IT1. In various embodiments, the contacting is conducted at an iron FT GHSV in the range of 200 to 9000 IT1, or 200 to 8000 IT1, or 200 to 7000 IT1, or 200 to 6000 IT1, or 200 to 5000 h-1. In various embodiments, the contacting is conducted at an iron FT GHSV in the range of 250 to 9000 IT1, or 250 to 8000 IT1, or 250 to 7000 IT1, or 250 to 6000 IT1, or 250 to 5000 h-1. In various embodiments, the contacting is conducted at an iron FT GHSV in the range of 300 to 9000 h-1, or 300 to 8000 IT1, or 300 to 7000 IT1, or 300 to 3000 IT1, or 300 to 5000 IT1. In some embodiments as described herein, the GHSV value in the first reaction zone is in the range of 250-10000 h-1 (e.g., in the range of 250 to 8000 IT1, or 250 to 7000 IT1, or 250 to 6000 IT1, or 250 to 5000 tr1). Of course, the person of ordinary skill in the art will appreciate that other space velocities may be appropriate for particular processes. The present inventors note that the CO selectivity and C5+ selectivity of the iron FT process can depend in part on the GHSV at which the process is performed, with higher CO selectivities and lower C5+ selectivities typically resulting from higher GHSV values. The person of ordinary skill in the art would be able to determine a desired CO selectivity and C5+ productivity for a given iron FT process and select an appropriate GHSV for the iron FT process, appreciating that the full range of space velocities described above may not be available for a given iron FTprocess.

[0035] Amounts of various atomic species as described herein are determined using inductively coupled plasma mass spectrometry (“ICP”). As the person of ordinary skill in the art will appreciate, ICP can detect most elements, but is blind to hydrogen, nitrogen and oxygen. Accordingly, amounts quantified “on an elemental basis” are determined by ICP with respect to amounts of ICP-measurable elements, i.e., excluding hydrogen, oxygen and nitrogen. Moreover, it can be convenient to quantify as-carbided catalysts without considering carbon in the quantification. Accordingly, amounts quantified “on an elemental basis exclusive of carbon” are determined by ICP excluding hydrogen, oxygen, nitrogen and carbon.

[0036] As described above, iron-based FT catalyst materials often have both rWGS and FT activity, and as such, the iron-based FT catalyst material is not particularly limited. For example, in some embodiments as described herein, the iron-based FT catalyst material includes at least 10 wt% iron (e.g., at least 15 wt%, at least 20 wt%, or at least 25 wt% iron), on an elemental basis exclusive of carbon. In various embodiments as described herein, the iron-based FT catalyst material includes at least 20 wt%, at least 35 wt%, or at least 40 wt% iron, on an elemental basis exclusive of carbon.

[0037] In various embodiments as otherwise described herein, the FT catalyst is an alkali-promoted iron FT catalyst. The present inventors note that alkali can provide increased water-gas shift activity - as the carbon dioxide:carbon monoxide ratio is maintained at a high value, water-gas shift activity in the FT reactor can further convert CO2 to CO and through to desirable products. In various embodiments as described herein, the FT catalyst comprises in the range of 0.2-5 wt% alkali metal, on an elemental basis exclusive of carbon. For example, in various embodiments, the FT catalyst comprises in the range of 0.2-3 wt%, or 0.2-2 wt%, or 0.3-5 wt%, or 0.3-3 wt%, or 0.3-2 wt%, or 0.4-5 wt%, or 0.4-3 wt%, or 0.4-2 wt% alkali metal, on an elemental basis exclusive of carbon. In some embodiments as described herein, the FT catalyst comprises in the range of 0.5-5 wt% alkali metal, e.g., 0.5-3 wt%, or 0.5-2 wt%, or 0.7-5 wt%, or 0.7-3 wt%, or 0.7-2 wt%, on an elemental basis exclusive of carbon. In various embodiments, the FT catalyst material comprises in the range of 1-5 wt% alkali metal, on an elemental basis. For example, in various embodiments, the FT catalyst comprises 1-3 wt%, or 1-2 wt%, or 1.3-5 wt%, or 1.3-3 wt%, or 1.3-2 wt% alkali metal, on an elemental basis exclusive of carbon. In some embodiments described herein, the FT catalyst comprises 1.5-5 wt% alkali metal, on an elemental basis exclusive of carbon. For example, in some embodiments the FT catalyst comprises 1.5-3 wt%, or 1.5-2.5 wt%, or 1.5-5 wt%, or 1.5-3 wt%, or 1.5-2.5 wt% alkalimetal, on an elemental basis exclusive of carbon.

[0038] In some embodiments, the alkali metal present in the FT catalyst is one or more of sodium, potassium, rubidium and cesium. In some embodiments as described herein, the alkali metal is one or more of sodium and potassium. For example, in some embodiments as described herein, the alkali metal is sodium. In particularly desirable embodiments, the alkali metal is potassium.

[0039] The particulars of the FT catalyst will depend on the intended use in operation. For example, if it is desired to suppress water-gas shift activity in the FT stage, a relatively low amount of alkali can be used in the FT catalyst, and relatively low FT reaction temperatures can be used; this can be desirable when the rWGS stage provides a high degree of conversion to carbon monoxide. If, however, the rWGS stage provides a lower degree of conversion to carbon monoxide, then it may be desirable to use an increased amount of alkali in the FT catalyst to favor reverse water-gas shift of CO2 to CO in the FT stage. Higher FT reaction temperatures can assist with this -- but at higher temperatures, C5+ selectivity from CO conversion may suffer. In many cases, it may be desirable to balance these effects, selecting an intermediate reaction temperature (e.g., 250-300 °C) and an intermediate alkali promoter level to provide for good C5+ selectivity while still converting some amount of CO2 via reverse water-gas shift in the FT stage (e.g., up to 20% conversion, or up to 10% conversion).

[0040] The iron-based FT catalyst materials suitable for use in the process as described herein can be a variety of forms and are not particularly limited. For example, the iron-based FT catalyst material may be a supported or unsupported catalyst material. While the form of the catalyst material is not particularly limited, in various desirable embodiments, the iron-based FT catalyst material is a supported catalyst material, wherein the support comprises at least one of titanium oxide, zirconium oxide, cerium oxide, aluminum oxide, silicon oxide and zinc oxide. For example, in various embodiments, the support comprises at least one or aluminum oxide and silicon oxide.

[0041] The person of ordinary skill in the art will appreciate that the iron-based FT catalyst materials of the disclosure can be provided in many forms, depending especially on the particular form of the reactor system in which they are to be used, e.g., in a fixed bed or as a fluidized bed. The supports of the iron-based FT catalyst materials can be provided themselves as discrete bodies of material, e.g., as porous particles, pellets or shaped extrudates, with the metals provided thereon to provide the iron FT catalyst material. However, in other embodiments, an iron FT catalyst material of the disclosure can itself be formed as a layer on an underlying substrate. The underlying substrate is not particularlylimited. It can be formed of, e.g., a metal or metal oxide, and can itself be provided in a number of forms, such as particles, pellets, shaped extrudates, or monoliths. The person of ordinary skill in the art will select an appropriate iron-based FT catalyst material for the particular reactor system.

[0042] In some embodiments as described herein, the iron-based FT catalyst materials in subsequent reaction zones (e.g., each (x+1)th reaction zone) are the same as in the first reaction zone. In some embodiments as described herein, the iron-based FT catalyst materials in subsequent reaction zones (e.g., each (x+1)th reaction zone), are different than the first reaction zone, e.g., each iron-based FT catalyst material used in the reaction zones are different.

[0043] As described above, the particulars of the iron-FT catalyst used in the first and subsequent reaction zones will depend on the intended use of each zone. Importantly, the present inventor have found that by using iron-FT catalyst that can have both reverse water-gas shift and Fischer-Tropsch activity, other catalyst need not be present in the reaction zones. Accordingly, in some embodiments as described herein, in the first reaction zone, contacting the first feed stream with an iron-based FT catalyst material is conducted in the substantial absence of a reverse water-gas shift catalyst material. For example, in the first reaction zone, the reverse water-gas shift catalyst material is present in an amount of no more than 10 wt% (e.g., no more than 5 wt%, or no more than 2 wt%) of the total catalyst material in the first reaction zone. In some embodiments as described herein, in the first reaction zone, the reverse water-gas shift catalyst material is present in an amount of no more than 1 wt% (e.g., no more than 0.5 wt%, or no more than 0.2 wt%) of the total catalyst material in the first reaction zone. In some embodiments, in the first reaction zone, contacting the first feed stream with an iron-based FT catalyst material is conducted in the absence of a reverse water-gas shift catalyst material.

[0044] Similarly, in subsequent reaction zones (e,g,, each (x+1)th reaction zone), contacting the (x+1)th feed stream with an iron-based FT catalyst material is conducted in the substantial absence of a reverse water-gas shift catalyst material. For example, in various embodiments, in the (x+1)th reaction zone, the reverse water-gas shift catalyst material is present in an amount of no more than 10 wt% (e.g., no more than 5 wt%, or no more than 2 wt%) of the total catalyst material in the (x+1)th reaction zone. In some embodiments as described herein, in the (x+1)th reaction zone, the reverse water-gas shift catalyst material is present in an amount of no more than 1 wt% (e.g., no more than 0.5 wt%, or no more than 0.2 wt%) of the total catalyst material in the (x+1)th reaction zone. In some embodiments, in the (x+1)th reaction zone, contacting the (x+1)th feed stream with an iron-based FT catalyst material is conducted in the absence of a reverse water-gas shift catalyst material.

[0045] In various embodiments as described herein, in the (n+2)th reaction zone, contacting the (n+2)th feed stream with an iron-based FT catalyst material is conducted in the substantial absence of a reverse water-gas shift catalyst material. For example, in various embodiments, in the (n+2)th reaction zone, the reverse water-gas shift catalyst material is present in an amount of no more than 10 wt% (e.g., no more than 5 wt%, or no more than 2 wt%) of the total catalyst material in the (n+2)th reaction zone. In some embodiments as described herein, in the (n+2)th reaction zone, the reverse water-gas shift catalyst material is present in an amount of no more than 1 wt% (e.g., no more than 0.5 wt%, or no more than 0.2 wt%) of the total catalyst material in the (n+2)th reaction zone. In some embodiments, in the (n+2)th reaction zone, contacting the (x n+2)th feed stream with an iron-based FT catalyst material is conducted in the absence of a reverse water-gas shift catalyst material.

[0046] As would be understood by the person of skill in the art, a reverse water-gas shift catalyst material as described herein is a non-iron-based catalyst material.

[0047] Conventionally, iron-containing catalyst materials are prepared for use as active catalyst materials by treating them in situ with a reducing gas such as hydrogen, under conditions sufficient to convert a substantial amount of the iron oxides of the calcined catalyst material to metallic iron. Then, when exposed to Fischer-Tropsch reaction conditions, a substantial part of this iron is converted to carbide. It is thus not conventionally necessary to provide a separate carbiding treatment; rather, the carbiding is a natural result of reaction conditions. Accordingly, in various embodiments, the iron-based FT catalyst material is activated by contact with H2 and oxides of carbon (e.g., CO and CO2).

[0048] However, a dedicated activation step may be conducted in any convenient manner. For example, in various embodiments, the activation includes a reduction step, in which the catalyst material is treated with a reducing gas stream (e.g., containing hydrogen) for a time and at a temperature sufficient to provide at least 50 atom% of the catalyst material in metallic form. Without intending to be bound by theory, the inventors understand this step to reduce oxidic iron species to metallic iron species, so that they can be more easily carbided in a subsequent treatment with a carbiding gas. Upon treatment with the reducing gas stream, a portion of the iron components present in the FT catalyst material as described herein react to metallic iron (Fe°).

[0049] In various embodiments, the treatment with the reducing gas stream is performed in the substantial absence of carbon monoxide. For example, in variousembodiments, the reducing gas stream comprises no more than 1 vol% carbon monoxide, e.g., no more than 0.5 vol%, or no more than 0.1 vol%, or no more than 0.05 vol%, or no more than 0.01 vol% carbon monoxide. In some embodiments as described herein, the reducing gas stream further comprises an inert gas. For example, in some embodiments, the inert gas is nitrogen. In some embodiments as described herein, the hydrogen and inert gas are present in the reducing gas stream in a ratio of at least 1:1.

[0050] In various embodiments, treating the iron-based FT catalyst material with the reducing gas stream is conducted at a temperature in the range of 350-650 °C. For example, in various embodiments as described herein, treating the iron-based FT catalyst material with the reducing gas stream is conducted at a temperature in the range of 350-600 °C, or 350-550 °C, or 350-500 °C. In various embodiments as described herein, treating the iron FT catalyst material with the reducing gas stream is conducted at a temperature in the range of 375-650 °C, or 375-600 °C, or 375-550 °C, or 375-500 °C. In various embodiments as described herein, treating the iron FT catalyst material with the reducing gas stream is conducted at a temperature in the range of 400-650 °C, or 400-600 °C, or 400-550 °C, or 400-500 °C.

[0051] As described above, treating the catalyst material with the reducing gas stream is conducted for a time sufficient to provide at least 50 atom% of the iron of the catalyst material in metallic form. In various embodiments, treating the catalyst material with the reducing gas stream is conducted for at least 12 hours, e.g., at least 14 hours. For example, in various embodiments as described herein, treating the catalyst material with the reducing gas stream is conducted for a time in the range of 12 to 30 hours, e.g., in the range of 12 to 24 hours, or 14 to 30 hours, or 14 to 24 hours.

[0052] The person of ordinary skill in the art will be able to determine appropriate reducing conditions to provide a catalyst material with at least 50 atom% iron in reduced form. In various embodiments, the treatment with the reducing gas stream is performed to provide a catalyst material in which at least 60 atom% of the iron is in reduced form, e.g., at least 70 atom%. In various embodiments, the treatment with the reducing gas stream is performed to provide a catalyst material in which at least 80 atom% of the iron is in reduced form, e.g., at least 85 atom%. The proportion of iron in reduced form is measured by XRD.

[0053] The activation can include treating the catalyst material with a carbiding gas stream comprising carbon monoxide, at a temperature of at least 180 °C for a time sufficient to provide at least 50 atom% of the iron of the catalyst material in carbided form. This can be performed, e.g., after a treatment with a reducing gas as described above.

[0054] It can be desirable to have a substantial fraction of the iron of the carbidedFischer-Tropsch catalyst material in carbide form, as it is carbide forms that are of highest catalytic activity. For example, in various embodiments of the carbided Fischer-Tropsch catalyst materials of the disclosure, at least 50 atom% of the iron is in a carbide form, e.g., at least 55 atom%, or at least 60 atom%. In various embodiments of the carbided Fischer- Tropsch catalyst materials of the disclosure, in the range of 50-95 atom% of the iron is in a carbide form, e.g., in the range of 50-90%, or 50-85%, or 50-80%. In various embodiments of the carbided Fischer-Tropsch catalyst materials of the disclosure, in the range of 55-95 atom% of the iron is in a carbide form, e.g., in the range of 55-90%, or 55-85%, or 55-80%. In various embodiments of the carbided Fischer-Tropsch catalyst materials of the disclosure, in the range of 60-95 atom% of the iron is in a carbide form, e.g., in the range of 60-90%, or 60-85%, or 60-80%. The amount of iron that is in the form of carbide is determined by Mbssbauer spectroscopy, and as such is expressed as an atomic fraction of iron in the form of carbide of the total iron species visible to Mbssbauer spectroscopy.

[0055] The present inventors note that, while oxidic iron is not a highly active catalyst for Fischer-Tropsch synthesis, it can catalyze water-gas shift reactions. In cases where the feed to the FT synthesis includes a high proportion of CO2, the present inventors have determined that water-gas shift activity can be highly desirable to convert that CO2 to CO for use in the Fischer-Tropsch synthesis. Accordingly, the present inventors have determined that some oxidic iron in the carbided Fischer-Tropsch catalyst material can be beneficial. Accordingly, in various embodiments of the carbided Fischer-Tropsch catalyst materials of the disclosure, at least 5 atom% of the iron is in an oxide phase, e.g., at least 10 atom%, or at least 15 atom%, or at least 20 atom%. However, the present inventors also note that oxidic iron forms are generally not active catalysts for Fischer-Tropsch synthesis. Accordingly, in various embodiments, it can be desirable to limit the amount of oxidic iron in the carbided Fischer-Tropsch catalyst material. In various embodiments of the carbided Fischer-Tropsch catalyst materials of the disclosure, in the range of 5-50 atom% of the iron is in an oxide phase, e.g., 5-45 atom%, or 5-40 atom%. In various embodiments of the carbided Fischer-Tropsch catalyst materials of the disclosure, in the range of 10-50 atom% of the iron is in an oxide phase, e.g., 10-45 atom%, or 10-40 atom%. In various embodiments of the carbided Fischer-Tropsch catalyst materials of the disclosure, in the range of 15-50 atom% of the iron is in an oxide phase, e.g., 15-45 atom%, or 15-40 atom%. In various embodiments of the carbided Fischer-Tropsch catalyst materials of the disclosure, in the range of 20-50 atom% of the iron is in an oxide phase, e.g., 20-45 atom%, or 20-40 atom%. The amount of iron that is in the form of oxide is determined by Mbssbauer spectroscopy, and as such is expressed as an atomic fraction of iron in the form of oxide of the total iron species visible to Mbssbauer spectroscopy. The person of ordinary skill in theart can, based on the disclosure herein, select carbiding conditions to provide a desired degree of oxidic iron in the carbided Fischer-Tropsch catalyst materials of the disclosure.

[0056] In various embodiments, at least 30 atom% of the oxidic iron of the carbided Fischer-Tropsch catalyst material is in the form of FesC . The present inventors note that this partially-reduced oxide has especially good activity as a reverse water-gas shift catalyst. In various embodiments, at least 40 atom% of the oxidic iron of the carbided Fischer- Tropsch catalyst material is in the form of FesC , e.g., at least 50 atom%. In various embodiments, at least 60 atom% of the oxidic iron of the carbided Fischer-Tropsch catalyst material is in the form of FesC , e.g., at least 70 atom%. The person of ordinary skill in the art can select carbiding conditions, particularly with respect to conditions under which the material is reduced, to provide a desired amount of Fe3O4. The amount of oxidic iron present as of FesC is determined using Mdssbauer spectroscopy.

[0057] In various embodiments of the present disclosure as otherwise described herein, the reducing gas / carbiding gas comprises at least a portion of H2 and CO (if present) from feed stream(s). For example, in some embodiments, the process further comprises separating at least a portion of H2 and at least a portion of CO of the feed stream(s) and contacting it with the iron-based Fischer-Tropsch catalyst material to activate the iron-based Fischer-Tropsch catalyst material. In the process 100 shown schematically in FIG. 1 , at least a portion of H2 and CO stream 125a is separated from the iron FT feed stream 111a and contacted with the iron FT catalyst material 113a to activate it. Additionally, at least a portion of H2 and CO stream 125b is separated from the iron FT feed stream 111b and contacted with the iron FT catalyst material 113b to activate it. However, separate carbiding processes are not necessary, as the iron FT catalyst material can be carbided under the iron FT reaction conditions, especially when treated first with a reducing gas as described above.

[0058] The first product stream comprises C5+ hydrocarbons, water, carbon dioxide and hydrogen. As described above, the process includes separating at least part of the water of the first product stream to provide a first separated water-rich product stream and a first separated water-poor product stream comprising carbon dioxide and hydrogen, and providing a second feed stream comprising at least a portion of the carbon dioxide and at least a portion of the hydrogen of the first separated water-poor product stream. For example, when n is 0, as shown in FIG. 1 , the process 100 includes separating at least part of the water of the first product stream to provide a first separated water-rich product stream 117 and a first separated water-poor product stream 118 comprising carbon dioxide and hydrogen, and providing a second feed stream 111b comprising at least a portion of the carbon dioxide and at least a portion of the hydrogen of the first separated water-poorproduct stream 118.

[0059] In embodiments when n is an integer that is 1 or more, the process includes in the (x+1)th separation zone, separating at least part of the water of the (x+1)th product stream to provide an (x+1)th separated water-rich product steam and an (x+1)th separated water-poor product stream comprising carbon dioxide and hydrogen; and providing an (x+2)th feed stream comprising at least a portion of the carbon dioxide and at least a portion of the hydrogen of the (x+1)th separated water-poor product stream. An example of such a process is shown schematically in FIG. 2. In FIG. 2, the first product stream 212a is separated in a first separation zone 216a to provide a first separated water-rich product stream 217a and a first separated water-poor product stream lean 218a, wherein at least a portion of (e.g., all of) the first separated water-poor product stream 218a provided to a second feed stream 211b. Similarly, the second product stream 216b is separated in a second separation zone 216b to provide a second separated water-rich product stream 217b and a second separated water-poor product stream 218b, wherein at least a portion of (e.g., all of) the second separated water-poor product stream 218b provided to a third feed stream 211c.

[0060] The separation of the product stream(s) as described herein can be accomplished at a variety of efficiencies. For example, in some embodiments as described herein, in one or more of the separations (e.g., each of the separations), the respective separation is performed such that at least 60% of water of the respective product stream is provided in the respective water-rich product stream. For example, example, in various embodiments as described herein, the respective separation is performed such that at least 70%, or at least 80%, or at least 90% or the water of the respective product stream is provided in the water-rich product stream. By separating the product steam(s), the amount of water carried to the next feed stream(s) in the process described herein is greatly reduced and helps to control the WGS / rWGS equilibrium. Accordingly, in various embodiments as otherwise described herein, the portion of the product stream that is included in the next (e.g., (x+2)th or (n+2)th) feed stream has a water content of no more than 10 mol%, e.g., or no more than 2 mol%, or no more than 0.5 mol%. This is particularly important for the subsequent feed stream (e.g., the (x+2)th or (n+2)th, as providing a feed stream with low amounts of water also improves the stability of the catalyst material.

[0061] As described above, the product stream(s) also include C5+ hydrocarbons. As would be understood by the person of ordinary skill in the art, the C5+ hydrocarbons and any water present in the product stream(s) would be considered condensates, and as such can be separated in the same separation zone. In some embodiments of the process asdescribed herein, these condensates can be separated from at least one of the product streams (e.g., each of the product streams). For example, in some embodiments as described herein, in one or more of the separations (e.g., each of the separations), the respective separation is performed such that at least 60% of C5+ hydrocarbons of the respective product stream is provided in the respective water-rich product stream. For example, in various embodiments as described herein, the respective separation is performed such that at least 70%, or at least 80%, or at least 90% or the C5+ hydrocarbons of the respective product stream is provided in the water-rich product stream.

[0062] In some embodiments as described herein, the process further comprises recovering C5+ hydrocarbons from the respective water-rich stream(s). An example of such a process is shown in FIG.3. In the process 300 for FIG.3, the first product stream 312a is separated in a first separation zone 316a to provide the first separated water-rich product stream 317a. The first separated water-rich product stream 317a is provided to a first hydrocarbon recovery zone 350a to provide a first C5+ hydrocarbon stream 352a.Additionally, the second product stream 312b is separated in a second separation zone 316b to provide the second separated water-rich product stream 317b. The second separated water-rich product stream 317b is provided to a second hydrocarbon recovery zone 350b to provide a second C5+ hydrocarbon stream 352b. While FIG. 3 shows separate hydrocarbon separation zone for each water-rich product stream, one hydrocarbon recovery zone may be used for separating each of the water-rich product streams.

[0063] The person of ordinary skill in the art will appreciate that a variety of processes can be used to remove water from the product stream(s). For example, the product stream(s) can be contacted with a water scavenger to remove water therefrom. For example, a molecular sieve guard bed can be used to remove water from the product stream(s); water can be recovered from the molecular sieves of the guard bed, e.g., by heating and vacuum.

[0064] In other embodiments, one or more of (e.g., each of) the separations are performed by cooling to condense water and optionally C5+ hydrocarbons, e.g., in a knockout vessel. For example, in various embodiments as described herein, each of the separations performed by cooling are performed in a respective cooling loop comprising a heat exchanger; a condenser and a product separation vessel, wherein the respective product stream is conducted through the heat exchanger; conducted through the condenser where water and optionally C5+ hydrocarbons are condensed; and conducted to the product separation vessel, from which the respective water-rich product stream is separated from the respective water-poor product stream, which is conducted through the heat exchanger toexchange heat with the respective product stream, then used to provide at least a portion of the carbon dioxide and at least a portion of the hydrogen of the next respective feed stream. The person of ordinary skill in the art can select knockout conditions to not only knock out a substantial portion of the water, but also a desired range of hydrocarbons.

[0065] An example of such a process is shown in FIG. 4. In the separation zone 416 of FIG. 4, the separation is performed in a respective cooling loop comprising a heat exchanger 430; a condenser 440 and a product separation vessel 460, wherein the respective product stream 412 is conducted through the heat exchanger 430; conducted through the condenser 440 where water 419a and optionally C5+ hydrocarbons 419b are condensed; and conducted to the product separation vessel 460, from which the respective water-rich product stream 417 is separated from the respective water-poor product stream 418, which is conducted through the heat exchanger 430 to exchange heat with the respective product stream 412, then used to provide at least a portion of the carbon dioxide and at least a portion of the hydrogen of the next respective feed stream. However, when each of the separations are performed by cooling, in some cases, the product streams are cooled enough so that it is desirably reheated for introduction to the next process step.

[0066] The person of ordinary skill in the art would appreciate that, based on the processes as described herein, the product stream(s) may include H2, CO, and CO2 and other components in various amounts. Components of the product stream(s) may be separated and used for various purposes in the process described herein.

[0067] For example, in various embodiments of the present disclosure as described herein, the process further comprises separating the product stream(s) to recycle at least a portion (e.g., at least 5 mol%, at least 10 mol%, or at least 25 mol%) of one or more components of the product stream(s) to the feed stream(s). For example, when the product stream(s) includes CO2, the process can include recycling at least a portion (e.g., at least 5 mol%, at least 10 mol%, or at least 25 mol%) of the CO2 of the product stream(s) to the feed stream(s). The product stream(s) may also include H2; in some embodiments, the process further includes recycling at least a portion of H2 of the product stream(s) (e.g., at least 5 mol%, at least 10 mol%, or at least 25 mol%) to the feed stream(s).

[0068] Such recycling is shown in the process 200 of FIG. 2. Here, the process 200 includes separating from the product stream(s) 212a, 212b, 212c at least a portion of CO2 (stream 215a, 215b, 215c) to recycle to the feed stream(s) 211a, 211b, 211c. Similarly, the process 200 includes separating from the product stream(s) 212a, 212b, 212b at least a portion of H2 (stream 214a, 214b, 214c) to recycle to the feed stream(s) 211a, 211b, 211c. While streams 215a / b / c is depicted as entering reactors 210a / b / c through a different inletthan the rest of the feed stream(s) 211a / b / c, it is considered to be part of the feed stream(s), as it is part of the material input to the process step.

[0069] As noted above, the second and subsequent feed stream includes H2. Notably, the first product stream will often include H2, e.g., unreacted from the preceding water-poor feed stream. In various embodiments, the second and subsequent feed stream includes at least a portion of the H2 of the preceding water-poor product stream. For example, in various embodiments as otherwise described herein, at least 25% of the H2, e.g., at least 50% of the H2, at least 75% of the H2, or at least 90% of the H2 of the preceding water-poor product stream is included in the second and subsequent feed stream. Of course, some of the H2 of the product stream(s) can be used for other purposes, e.g., catalyst material activation as described herein.

[0070] In some embodiments, substantially all of the H2 of the second and subsequent feed stream comes from the first and previous product stream. In fact, the person of ordinary skill in the art can provide more H2 than necessary for the iron-based FT reaction in the first feed stream, to provide excess H2 in the first product stream that can then provide a desired amount of H2 to the second and subsequent feed stream for the Fischer-Tropsch process steps. However, in other embodiments, H2 can be provided to the second and subsequent feed stream from other sources. For example, in various embodiments, one or more of (e.g., each of) the second and subsequent feed stream includes hydrogen provided from a source other than the preceding water-poor product stream. In FIG. 3, a stream of H2 326a from some other source is included in the second feed stream 311 b. The person of ordinary skill in the art will appreciate that H2 can be provided from a variety of sources, e.g., gasification, reforming, or H2O electrolysis. Moreover, as described in more detail below, H2 can be recycled to the feed stream(s).

[0071] As described above, the second and subsequent feed streams also include at least a portion of the carbon dioxide of the previous water-poor product stream. For example, in various embodiments, at least 10% of the CO2 of the water-poor product stream, e.g., at least 25% of the CO2, at least 50% of the CO2, at least 75% of the CO2, or at least 90% of the CO2 of the water-poor product stream is included in the second and subsequent feed stream. Accordingly, in various embodiments as otherwise described herein, the portion of the water-poor product stream that is included in the second and subsequent feed stream has a CO2 content in the range of 10-95 mol% CO2, e.g., 10-90 mol%, or 10-85 mol%, or 10-80 mol%, or 10-75 mol%, or 10-70 mol%, or 20-95 mol%, or 20-90 mol%, or 20- 85 mol%, or 20-80 mol%, or 20-75 mol%, or 20-70 mol%, or 30-95 mol%, or 30-90 mol%, or 30-85 mol%, or 30-80 mol%, or 30-75 mol%, or 30-70 mol% CO2. However, in otherembodiments, CO2 can be provided to the second and subsequent feed stream from other sources. For example, in various embodiments, one or more of (e.g., each of) the second and subsequent feed stream includes carbon dioxide provided from a source other than the preceding water-poor product stream. In FIG. 3, a stream of CO2 326b from some other source is included in the second feed stream 311 b. The person of ordinary skill in the art will appreciate that CO2 can be provided from a variety of sources. Moreover, as described in more detail below, CO2 can be recycled to the feed stream(s).

[0072] It can additionally or alternatively be desirable to include inerts, such as nitrogen and methane, to the second and subsequent feed stream. In various embodiments, the second and subsequent feed streams includes at least a portion of the inerts of the preceding water-poor product stream. For example, in various embodiments as otherwise described herein, at least 25% of the inerts, e.g., at least 50% of the inerts, at least 75% of the inerts, or at least 90% of the inerts of the preceding water-poor product stream is included in the second and subsequent feed stream.

[0073] In other embodiments, one or more inerts (e.g., nitrogen and / or methane) are provided to the second and subsequent feed stream from a source other than the preceding water-poor product stream. For example, in various embodiments, the second and subsequent FT feed stream includes up to 80 mol% of one or more inerts, e.g., in the range of 3-80 mol%, or 5-80 mol%, or 10-80 mol%, or 15-80 mol%, or 30-80 mol% of one or more inerts. In various embodiments, the second and subsequent feed stream includes up to 70 mol% inerts, up to 60 mol% inerts, or up to 50 mol% inerts, e.g., 3-70 mol%, or 5-70 mol%, or 10-70 mol%, or 15-70 mol%, or 30-70 mol%, or 3-60 mol%, or 5-60 mol%, or 10-60 mol%, or 15-60 mol%, or 30-60 mol%, or 3-50 mol%, or 5-50 mol%, or 10-50 mol%, or 15-50 mol%, or 30-50 mol% inerts. In FIG. 3, a stream of inert(s) 326c from some other source is included in the water-poor stream 311 b. The person of ordinary skill in the art will appreciate that inerts can be provided from a variety of sources. Moreover, as described in more detail below, inerts can be recycled to the feed stream(s) from the product stream(s).

[0074] As described above, the water-poor product stream(s) comprise carbon dioxide and hydrogen. In some embodiments as described herein, the water-poor product stream(s) may further include C1-C4 hydrocarbons. As such, in some embodiments as described herein, one or more of (e.g., each of) the second and subsequent feed streams include C1-C4 hydrocarbons from a preceding water-poor product stream. In some embodiments as described herein, the C1-C4 hydrocarbons from the preceding water-poor product stream are at least 50 mol% olefins, e.g., at least 60 wt% olefins, or at least 70 wt% olefins.

[0075] The C1-C4 hydrocarbons, e.g., light hydrocarbons, while often not a desired portion of a Fischer-Tropsch product to be used as a fuel or a lubricant, can themselves be useful for a number of purposes. Accordingly, in various embodiments, the process further includes separating at least a portion of C1-C4 hydrocarbons of the water-poor product stream(s) to provide a light hydrocarbon stream. In some embodiments of the process as described herein, the process further includes separation at least a portion of the C1-C4 of the (n+2)th product stream to provide a light hydrocarbon stream. For example, in the process 300 of FIG. 3, at least a portion of the C1-C4 hydrocarbon is separated from the water-poor product streams 318a, 318b, and the (n+2)th product stream 312c to provide a light hydrocarbon stream 336. The light hydrocarbon stream can, for example, be recycled to the feed streams. In the process 300 of FIG. 3, light hydrocarbons can be provided as part of the recycle stream 336, which becomes part of the feed streams 311a, 311 b, and / or 311c.

[0076] As with the product stream, the components of the water-poor product stream, e.g., hydrogen, carbon monoxide, and carbon dioxide may be used in other feeds of the process as described herein. As such, in some embodiments as described herein, at least a portion of hydrogen, carbon monoxide and carbon dioxide of the water-poor product stream(s) is included in the first feed stream and / or a second and subsequent feed stream. For example, in the process of FIG. 3, at least a portion of H2 of the water-poor product stream 318a and 318b (e.g., at least 25%, or at least 50%) can be recycled to the feed streams 311a and / or 311b via recycle stream 336. In some embodiments as described herein, at least a portion of the hydrogen, carbon monoxide and carbon dioxide of the (n+2)th product stream(s) is included in the first feed stream and / or a second and subsequent feed streams. For example, in the process of FIG. 3, at least a portion of H2 of the (n+2)th product stream 312c (e.g., at least 25%, or at least 50%) can be recycled to the feed streams 311a, 311b, and / or 311c via recycle stream 336.

[0077] In some cases, e.g., when H2 is provided to the second and subsequent feed streams from an H2 source other than the first product stream, H2 from the (n+2)th product stream can make up most of the H2 of the first feed stream, e.g., at least 90%, at least 95%, or at least 98% of the H2 of the first feed stream. This is shown, e.g., in FIG. 5. Here, the primary H2 input to the process is through stream 540, which becomes part of the second feed stream 511 b. H2 of the (n+2)th product stream is included in recycle stream 536, which becomes part of first feed stream 511a.

[0078] Similarly, it can be desirable to recycle CO of the water-poor product stream(s), for example, to the first feed stream and / or the second and subsequent feedstreams. For example, in the process of FIG. 3, at least a portion of carbon monoxide of the water-poor product stream 318a and 318b (e.g., at least 25%, or at least 50%) can be recycled to the feed streams 311a and 311b via recycle stream 336. In some embodiments as described herein, at least a portion of the carbon monoxide of the (n+2)th product stream is included in the first feed stream and / or a second and subsequent feed streams. For example, in the process of FIG. 3, at least a portion of carbon monoxide of the (n+2)th product stream 312c (e.g., at least 25%, or at least 50%) can be recycled to the feed streams 311a, 311b, and / or 311 c via recycle stream 336.

[0079] As with hydrogen and carbon monoxide, it can be desirable to recycle carbon dioxide of the water-poor product stream(s), for example, to the first feed stream and / or the second and subsequent feed streams. Since CO2 is the primary carbon source for the processes described herein, it can be especially desirable to recycle CO2 to the first feed stream. Accordingly, in various embodiments, the process includes recycling at least a portion (e.g., at least 50%, at least 75%, or at least 90%) of CO2 of the (n+2)th product stream to the first feed stream. For example, in the process of FIG. 3, at least a portion of CO2 of the (n+2)th product stream 312c (e.g., at least 50%, at least 75%, or at least 90%) can be recycled to the first feed stream 311a via recycle stream 336. For example, it can be desirable to recycle carbon dioxide from the water-poor product stream, for example, to the first feed stream and / or second and subsequent feed streams. For example, in the process of FIG. 3, at least a portion of carbon dioxide of the water-poor product stream 318a and 318b (e.g., at least 25%, or at least 50%) can be recycled to the iron FT feed stream 311a and / or 311b via recycle stream 336. In some cases, e.g., when CO2 is provided to the second and subsequent FT feed stream from a CO2 source other than the preceding waterpoor product stream, CO2 from the (n+2)th product stream can make up most of the CO2 of the first feed stream, e.g., at least 90%, at least 95%, or at least 98% of the CO2 of the first feed stream. This is shown, e.g., in FIG. 6. Here, the primary CO2 input to the process is through stream 640, which becomes part of the second feed stream 611b. CO2 of the (n+2)th product stream is included in recycle stream 636, which becomes part of first feed stream 611a.

[0080] Moreover, when one or more inerts are used in the process steps, it can be desirable to recycle these. For example, in various embodiments, the process includes recycling at least a portion of inerts of the water-poor product stream(s) to the first feed stream and / or second and subsequent feed streams. For example, in the process of FIG. 3, at least a portion of inerts of the water-poor product streams 318a and 318b (e.g., at least 25%, or at least 50%) can be recycled to the iron FT feed stream 311a and / or 311b via recycle stream 336. In various embodiments, a purge stream can be incorporated with therecycle stream to prevent uncontrolled accumulation of inerts in the recycle stream (not shown here). In some embodiments as described herein, at least a portion of the inerts of the (n+2)th product stream is included in the first feed stream and / or a second and subsequent feed streams. For example, in the process of FIG. 3, at least a portion of inerts of the (n+2)th product stream 312c (e.g., at least 25%, or at least 50%) can be recycled to the feed streams 311a, 311b, and / or 311c via recycle stream 336.

[0081] As described above, the (n+2)th product stream may also include light hydrocarbons that may be recycled to the first and / or second and subsequent feed streams. There are other uses for the light hydrocarbon stream. For example, in some embodiments, the process further comprises at least partially oxidizing at least a portion of the C1-C4 hydrocarbons of the (n+2)th product stream in a partial oxidation reaction zone to provide a partial oxidation (pOX) stream comprising carbon monoxide e.g., a CO- and / or CO2- containing partial oxidation (pOX) stream, and including at least a portion of the pOX stream in the feed streams. An example of such a process is shown schematically in FIG. 6, in which the process 600, the first feed stream 611a, the first product stream 612a, the iron FT catalyst material 613a and 613b, the second feed stream 611b, the second product stream 612b, the separation zone 616, the water-rich product stream 617, and the water-poor product stream 618 can be as otherwise described herein. Here, the process includes oxidizing at least a portion of the light hydrocarbon stream 638 in a partial oxidation reaction zone 692 to provide a CO- and / or CO2 containing pOX stream, and including at least a portion of the pOX stream 694 stream in the first feed stream 611a.

[0082] Similarly, in some embodiments as described herein, the process further includes oxidizing at least a portion of C1-C4 hydrocarbons of the (n+2)th product stream in an oxidation reaction zone to provide a oxidation (OX) product stream comprising carbon dioxide, and including at least a portion of the carbon dioxide of the oxidation product stream to the first feed stream. An example of such a process is shown in FIG. 6, where the process 600 includes oxidizing at least a portion of the light hydrocarbon stream 638 in an oxidation reaction zone 692 to provide a CO2 containing OX stream, and including at least a portion of the OX stream 694 stream in the first feed stream 611a.

[0083] Moreover, the light hydrocarbon stream can be burned to provide heat energy, which can be used to heat various process streams, or to generate electricity. Accordingly, in various embodiments, the process includes burning at least a portion of the light hydrocarbon stream to provide energy, e.g., heat energy or electrical energy. For example, in the process 500 of FIG. 5, a portion of light hydrocarbon stream 538 is burned in a power generation zone (here, in an electrical generator 570), to generate electricity stream572. In various embodiments, the heat energy may be used to provide the needed heat duty for the process. For example, in the process 500 of FIG. 5, a portion of the light hydrocarbon stream 538 is burned in a power generation zone (here, in a heat generator 580), to generate heat stream 582. The heat stream 582 is conducted to a heat exchange zone 590 to heat the first feed stream 511a.

[0084] The present inventors have noted that it can be desirable to provide for heat exchange with a relatively hot first feed stream to cool the first product stream to provide heat elsewhere to the integrated process. For example, in various embodiments of the processes as otherwise described herein, the process further comprises exchanging heat between at least a portion of the first product stream and at least a portion of the first feed stream, thereby cooling at least a portion of the first product stream and heating at least a portion of the first feed stream. An example of such a process is shown schematically in FIG. 5. In FIG. 5, the process 500, first reactor 510a, first feed stream 511a, first product stream 512a, iron FT catalyst material 513a and 513b, second reactor 510b, second feed stream 511b, second product stream 512b, separation zone 516, the water-rich product stream 517, and the water-poor product stream 518 are generally as described above. Here, the process 500 includes exchanging heat between at least a portion of the first product stream 512a and a least a portion of the first feed stream 511a in a first heat exchange zone 530, thereby cooling at least a portion of the first product stream 512a and heating at least a portion of the first feed stream 511a. The person of ordinary skill in the art will appreciate that a wide variety of heat exchangers can be used for this purpose.

[0085] Of course, any excess heat in the first product stream can be additionally or alternatively used for other purposes. For example, in various embodiments the process further comprises exchanging heat between at least a portion of the first product stream and a steam generation zone, thereby cooling at least a portion of the first product stream and providing heat to the steam generation zone. This is shown in FIG. 5. Here, after heat exchange with the first feed stream 511a, the first product stream 512a is conducted to steam generation zone 532, to cool the first product stream 512a and provide heat to the steam generation zone 532. Steam can be generated from the heat provided, and electricity can be generated from the steam. For example, in the embodiment of FIG. 5, electricity stream 564 is provided by the generation of electricity using steam generated in the steam generation zone 532. Of course, as would be understood to the person of ordinary skill in the art, the steam generated in the steam generation zone may be used in other processes. In various embodiments, the steam may be used to heat the first feed stream. For example, in the embodiment of FIG. 5, the steam stream 566 generated in the steam generation zone 532 is conducted to the heat exchange zone 590 to heat the first feed stream 511a.

[0086] As with the first product stream, heat can be exchanged from the (n+2)th product stream to provide heat to, for example, feed streams or a steam generation zone. For example, in various embodiments, the process further comprises exchanging heat between at least a portion of the (n+2)th product stream and at least a portion of the first feed stream, thereby cooling at least a portion of the (n+2)th product stream and heating at least a portion of the first feed stream. In process 600 of FIG. 6, heat is exchanged between at least a portion of the (n+2)th product stream 612b and first feed stream 611a in a heat exchange zone 630, thereby cooling the (n+2)th product stream 612n and heating the first feed stream 611a. The person of ordinary skill in the art will appreciate that a wide variety of heat exchangers can be used for this purpose.

[0087] Of course, any excess heat in the (n+2)th product stream can be additionally or alternatively used for other purposes. For example, in various embodiments the process further comprises exchanging heat between at least a portion of the (n+2)th product stream and a steam generation zone, thereby cooling at least a portion of the (n+2)th product stream and providing heat to the steam generation zone. This is shown in FIG. 6. Here, after heat exchange with the first feed stream 611a, the (n+2)th product stream 612b is conducted to steam generation zone 632, to cool the (n+2)th product stream 612b and provide heat to the steam generation zone 632. Steam can be generated from the heat provided, and electricity can be generated from the steam (not shown here).

[0088] As noted above, the process described herein provides product streams that includes C5+ hydrocarbons (e.g., unsubstituted hydrocarbons like alkanes and alkenes, and / or oxygenated hydrocarbons such as alcohols). Accordingly, in various embodiments, one or more products are provided from at least a portion of C5+ hydrocarbons of the product streams. The C5+ hydrocarbons can be used as the basis of a variety of fuels, e.g., gasoline, diesel, aviation fuel. Other products, like waxes and lubricants, can also be made. And alkenes and oxygenates can be used as feedstocks in a variety of other processes.

[0089] The person of ordinary skill in the art will use conventional post-processing techniques to convert the C5+ hydrocarbon-containing product to desirable products such as desirable fuels. For example, in various embodiments, the process further includes hydroprocessing at least a portion of C5+ hydrocarbons of the product streams. As the person of ordinary skill in the art will appreciate, hydroprocessing is a treatment of the hydrocarbon stream with hydrogen in the presence of a suitable catalyst material. A wide variety of hydroprocessing techniques are known and the person of ordinary skill in the art will apply them here. For example, in the process 500 and 600 of FIGs. 5, and 6, respectively, (n+2)th product streams 512b and 612b are hydroprocessed inhydroprocessing reactors 550 and 650, to provide hydroprocessed product streams 552 and 652.

[0090] The processes described herein can be operated in a wide variety of reactor systems. In some embodiments, the first reaction zone (i.e. , in which the iron FT process step is performed) comprises a first FT reactor in which an iron-based FT catalyst material is disposed, and the (x+1)th reaction zones (i.e., in which the (x+1)th iron FT process step is performed) comprises a (x+1)th reactor in which an iron-based FT catalyst material is disposed. Examples of such processes are shown schematically in FIGS. 1 , 2, 3, 5, and 6. In these examples, the process (100, 200, 300, 500, 600) is performed in a reactor system that includes first reactor (110a, 210a, 310a, 510a, 610a) in which the iron FT catalyst material (113a, 213a, 313a, 513a, 613a) is disposed, and an (x+1)th reactor (110b, 210b, 210c, 310b, 310c, 510b, and 610b) in which the iron FT catalyst material (113b, 213b, 213c, 313b, 313c, 513b, 613b) is disposed, to provide a (n+2)th product stream(112b, 212c, 312c, 512b, and 612b). The reactors used for the integrated process of the present disclosure as described herein are not particularly limited, and the person of ordinary skill in the art will be able to select an appropriate reactor. In various embodiments, the process is performed in a reactor system comprising one or more iron FT catalyst containers in which the iron FT catalyst is disposed. These can be provided in the same reactor.

[0091] As described above, CO2 and H2 are substantial inputs to the process as described herein. Advantageously, the present inventors have recognized that each of these can come from renewable or otherwise environmentally responsible sources.

[0092] CO2 can be captured from the environment generally or more directly from processes that form CO2 (especially in difficult-to-abate sectors). This can make the eventual hydrocarbon product substantially carbon-neutral or of lower carbon intensity. Accordingly, in some embodiments of the disclosure as described herein, at least a part of the CO2 of the first feed stream, the second feed stream, and / or subsequent feed streams is from a renewable source. In some embodiments, at least part (e.g., at least 25%, at least 50%, or at least 75%) of the CO2 of the first feed stream, the second feed stream, and / or the subsequent feed streams is from direct air capture. In some embodiments, at least part (e.g., at least 25%, at least 50%, or at least 75%) of the CO2 of the first feed stream, the second feed stream, and / or the subsequent feed streams is from a manufacturing plant such as a bioethanol plant (e.g., CO2 produced fermentation), a steel plant, or a cement plant. Accordingly, the processes of the disclosure as described herein can be not only carbon neutral, but in some cases a net consumer of carbon dioxide. These benefits in particular make the integrated processes highly attractive for decarbonizing transportation fuels, forboth automotive and aviation sectors.

[0093] Similarly, H2 can be provided from environmentally-responsible sources. In some embodiments, at least a part of the H2 of the first feed stream, the second feed stream, and / or the subsequent feed streams is from a renewable source. For example, in various embodiments, at least part (e.g., at least 25%, at least 50%, or at least 75%) of the H2 of the first feed stream, the second feed stream, and / or the subsequent feed streams can be so- called “green” hydrogen, e.g., produced from the electrolysis of water operated using renewable electricity (such as wind, solar, or hydro-electric power). In some embodiments, at least part (e.g., at least 25%, at least 50%, or at least 75%) of the H2 of the first feed stream, the second feed stream, and / or the subsequent feed streams may be from a so- called “blue” source, e.g., from a natural gas reforming process with carbon capture. Of course, other sources of H2 can be used in part or in full. For example, in some embodiments, at least part (e.g., at least 25%, at least 50%, or at least 75%) of the H2 of the first feed stream, the second feed stream, and / or the subsequent feed streams is grey hydrogen, black hydrogen, brown hydrogen, pink hydrogen, turquoise hydrogen, yellow hydrogen, and / or white hydrogen.

[0094] The present inventors have noted that electrolysis of water is a desirable way to provide hydrogen to the claimed processes. Accordingly, in some embodiments, the process includes providing at least a portion of H2 to the first feed stream, the second feed stream, and / or the subsequent feed stream by electrolysis of water. In some embodiments, the electrolysis of water is performed using at least partially electricity from a renewable source, e.g., to provide so-called “green hydrogen.” However, the present inventors have noted that electricity can be generated as part of the claimed process, e.g., using heat exchange from the first or (n+2)th product stream, or by burning light hydrocarbons as described above. In some embodiments, the electrolysis of water is performed using at least partially electricity generated according to the processes as described herein. For example, in the process 500 of FIG. 5, the water-rich product stream 517 separated from the first product stream is electrolyzed in electrolyzer 560, using electricity 564 generated from steam made in the steam generation zone 532 by heat exchange from the first product stream. H2 generated in the electrolysis is provided via stream 565 to the first feed stream. In some embodiments, at least a portion of O2 generated in the electrolysis 563 is provided to a partial oxidation reaction zone or oxidation reaction zone as described herein.EXAMPLES

[0095] The Examples that follow are illustrative of specific embodiments of the process of the disclosure, and various uses thereof. They are set forth for explanatorypurposes only, and are not to be taken as limiting the scope of the disclosure.

[0096] Example 1. Overall single-pass CO2 conversion

[0097] An exemplary trajectory for the increase in overall per-pass conversion with added number of reactor stages is shown in FIG. 7. An economic maximum reactor count is suspected to be less than 4 but requires detailed assessment on a case-by-case scenario, taking into account amongst others the added cost of each added stage and the reduction in recycle demand. As one can appreciate, the improvement in CO2 conversion in combination with improved selectivity to C5+ hydrocarbons (via olefin insertion) in subsequent stages is highly beneficial in increasing the yield towards C5+ hydrocarbons per pass.

[0098] Additional aspects of the disclosure are provided by the following enumerated embodiments, which may be combined in any number and in any combination that is not logically or technically inconsistent.Embodiment 1. A process for preparing hydrocarbons, comprising providing a first feed stream comprising carbon dioxide and hydrogen in a first reaction zone, contacting the first feed stream with an iron-based FT catalyst material under conditions sufficient to form a first product stream comprising C5+ hydrocarbons, water, carbon dioxide and hydrogen; in a first separation zone, separating at least part of the water of the first product stream to provide a first separated water-rich product stream and a first separated water-poor product stream comprising carbon dioxide and hydrogen; providing a second feed stream comprising at least a portion of the carbon dioxide and at least a portion of the hydrogen of the first separated water-poor product stream; and performing n times, in which n is 0 or an integer that is 1 or more, in n sequentially- arranged pairs of zones each comprising a separation zone and a reaction zone, the following set of operations n times, with each iteration sequentially taking an integer value of x from 1 to n when n is not zero: in the (x+1)th reaction zone, contacting the (x+1)th feed stream with an ironbased FT catalyst material under conditions sufficient to form an (x+1)th product stream comprising C5+ hydrocarbons, water, carbon dioxide and hydrogen; in the (x+1)th separation zone, separating at least part of the water of the (x+1)th product stream to provide an (x+1)th separated water-rich product steam and an (x+1)th separated water-poor product stream comprising carbon dioxide and hydrogen; andproviding an (x+2)th feed stream comprising at least a portion of the carbon dioxide and at least a portion of the hydrogen of the (x+1)th separated water-poor product stream; and in an (n+2)th reaction zone, contacting the (n+2)th feed stream with an iron-based FT catalyst material under conditions sufficient to form an (n+2)th product stream comprising C5+ hydrocarbons, water, carbon dioxide and hydrogen.Embodiment 2. The process of embodiment 1 , wherein n is 0.Embodiment 3. The process of embodiment 1 , wherein n is in the range of 1-10, e.g.,1-7, or 1-5, or 1-3.Embodiment 4. The process of embodiment 1 , wherein n is in the range of 2-10, e.g.,2-7, or 2-5 or 2-4.Embodiment 5. The process of embodiment 1 , wherein n is in the range of 3-10, e.g.,3-7, or 3-5.Embodiment 6. The process of any of embodiments 1-5, wherein a molar ratio of hydrogen to carbon dioxide in at least one of the feed streams (e.g., in each feed stream) is in the range of 1-10, e.g., 2-10 or 2-5.Embodiment 7. The process of any of embodiments 1-5, wherein a molar ratio of hydrogen to carbon dioxide in at least one of the feed streams (e.g., in each feed stream) is in the range of 1.5-4.5, e.g., 2-4.5, or 2.5-4.5, or 1.5-4, or 2-4, or 2.5-4, or 1.5-3.5, or 2-3.5, or 2.5-3.5, or 1.5-3, or 2-3.Embodiment 8. The process of any of embodiments 1-7, wherein in at least one (e.g., each of) the reaction zones the FT catalyst material is an alkali-promoted iron-based FT catalyst material.Embodiment 9. The process of any of embodiments 1-8, wherein in the first reaction zone, contacting the first feed stream with an iron-based FT catalyst material is conducted in the substantial absence of a reverse water-gas shift catalyst material.Embodiment 10. The process of embodiment 9, wherein in the first reaction zone, the reverse water-gas shift catalyst material is present in an amount of no more than 10 wt% (e.g., no more than 5 wt%, or no more than 2 wt%) of the total catalyst material in the first reaction zone.Embodiment 11. The process of embodiment 9, wherein in the first reaction zone, the reverse water-gas shift catalyst material is present in an amount of no more than 1 wt% (e.g., no more than 0.5 wt%, or no more than 0.2 wt%) of the total catalyst material in the first reaction zone.Embodiment 12. The process of embodiment 9, wherein in the first reaction zone, contacting the first feed stream with an iron-based FT catalyst material is conducted in the absence of a reverse water-gas shift catalyst material.Embodiment 13. The process of any of embodiments 1-12, wherein in the (x+1)th reaction zone, contacting the (x+1)th feed stream with an iron-based FT catalyst material is conducted in the substantial absence of a reverse water-gas shift catalyst material.Embodiment 14. The process of embodiment 13, wherein in the (x+1)th reaction zone, the reverse water-gas shift catalyst material is present in an amount of no more than 10 wt% (e.g., no more than 5 wt%, or no more than 2 wt%) of the total catalyst material in the (x+1)th reaction zone.Embodiment 15. The process of embodiment 13, wherein in the (x+1)th reaction zone, the reverse water-gas shift catalyst material is present in an amount of no more than 1 wt% (e.g., no more than 0.5 wt%, or no more than 0.2 wt%) of the total catalyst material in the (x+1)th reaction zone.Embodiment 16. The process of embodiment 13, wherein in the (x+1)th reaction zone, contacting the (x+1)th feed stream with an iron-based FT catalyst material is conducted in the absence of a reverse water-gas shift catalyst material.Embodiment 17. The process of any of embodiments 1-16, wherein in the (n+2)th reaction zone, contacting the (n+2)th feed stream with an iron-based FT catalyst material is conducted in the substantial absence of a reverse water-gas shift catalyst material.Embodiment 18. The process of embodiment 17, wherein in the (n+2)th reaction zone, the reverse water-gas shift catalyst material is present in an amount of no more than 10 wt% (e.g., no more than 5 wt%, or no more than 2 wt%) of the total catalyst material in the (n+2)th reaction zone.Embodiment 19. The process of embodiment 17, wherein in the (n+2)th reaction zone, the reverse water-gas shift catalyst material is present in an amount of no more than 1 wt% (e.g., no more than 0.5 wt%, or no more than 0.2 wt%) of the total catalyst material in the (n+2)th reaction zone.Embodiment 20. The process of embodiment 17, wherein in the (n+2)th reaction zone, contacting the (x n+2)th feed stream with an iron-based FT catalyst material is conducted in the absence of a reverse water-gas shift catalyst material.Embodiment 21. The process of any of embodiments 1-20, wherein in at least one of (e.g., each of) the contacting of a feed stream with an iron-based FT catalyst material, the contacting is performed at a temperature in the range of 250-400 °C, e.g., 250-350 °C, or 300-400 °C, or 300-350 °C.Embodiment 22. The process of any of embodiments 1-21 , wherein in one or more of the separations (e.g., each of the separations), the respective separation is performed such that at least 60% of water of the respective product stream is provided in the respective water-rich product stream, e.g., at least 70%, or at least 80%, or at least 90%.Embodiment 23. The process of any of embodiments 1-22, wherein in one or more of the separations (e.g., each of the separations), the respective separation is performed such that at least 60% of C5+ hydrocarbons is provided in the respective water-rich product stream, e.g., at least 70%, or at least 80%, or at least 90%.Embodiment 24. The process of embodiment 23, further comprising recovering C5+ hydrocarbons from the respective water rich stream(s).Embodiment 25. The process of any of embodiments 1-24, wherein one or more of (e.g., each of) the separations are performed by cooling to condense water and optionally C5+ hydrocarbons.Embodiment 26. The process of embodiment 25, wherein each of the separations performed by cooling are performed in a respective cooling loop comprising a heat exchanger; a condenser and a product separation vessel, wherein the respective product stream is conducted through the heat exchanger; conducted through the condenser where water and optionally C5+ hydrocarbons are condensed; and conducted to the product separation vessel, from which the respective water-rich product stream is separated from the respective water-poor product stream, which is conducted through the heat exchanger to exchange heat with the respective product stream, then used to provide at least a portion of the carbon dioxide and at least a portion of the hydrogen of the next respective feed stream.Embodiment 27. The process of any of embodiments 1-26, wherein one or more of (e.g., each of) the second and subsequent feed streams includes hydrogen provided from a source other than the preceding water-poor product stream.Embodiment 28. The process of any of embodiments 1-27, wherein one or more of the second and subsequent feed streams includes C1-C4 hydrocarbons from a preceding waterpoor product stream.Embodiment 29. The process of embodiment 28, wherein the C1-C4 hydrocarbons from the preceding water-poor product stream are at least 50 mol% olefins, e.g., at least 60 wt%, or at least 70 wt%.Embodiment 30. The process of any of embodiments 1-29, wherein the GHSV value in the first reaction zone is in the range of 250-10000 IT1.Embodiment 31 . The process of any of embodiments 1-30, wherein the pressure in the first reaction zone is at least 20 barg, e.g., at least 30 barg or at least 35 barg.Embodiment 32. The process of any of embodiments 1-31 , having a single-pass conversion of CO2 of at least 70%, e.g., at least 75%, or at least 80%, or at least 85%, or at least 90%Embodiment 33. The process of any of embodiments 1-32, further comprising, in a (n+2)th separation zone, separating at least part of the C1-C4 hydrocarbons of the (n+2)th product stream, and including them in the first feed stream, optionally subjecting them to a dehydrogenation to increase olefin content.

[0099] The particulars shown herein are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of various embodiments of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for the fundamental understanding of the invention, the description taken with the drawings and / or examples making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. Thus, before the disclosed processes and devices are described, it is to be understood that the aspects described herein are not limited to specific embodiments, apparatuses, or configurations, and as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and, unless specifically defined herein, is not intended to be limiting.

[0100] The terms “a,” “an,” “the” and similar referents used in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0101] All methods described herein can be performed in any suitable order of steps unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0102] Unless the context clearly requires otherwise, throughout the description and the claims, the words ‘comprise’, ‘comprising’, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”. Words using the singular or plural number also include the plural and singular number, respectively. Additionally, the words “herein,” “above,” and “below” and words of similar import, when used in this application, shall refer to thisapplication as a whole and not to any particular portions of the application.

[0103] As will be understood by one of ordinary skill in the art, each embodiment disclosed herein can comprise, consist essentially of or consist of its particular stated element, step, ingredient or component. As used herein, the transition term “comprise” or “comprises” means includes, but is not limited to, and allows for the inclusion of unspecified elements, steps, ingredients, or components, even in major amounts. The transitional phrase “consisting of’ excludes any element, step, ingredient or component not specified. The transition phrase “consisting essentially of” limits the scope of the embodiment to the specified elements, steps, ingredients or components and to those that do not materially affect the embodiment.

[0104] Unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0105] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0106] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member may be referred to and claimed individually or in any combination with other members of the group or other elements found herein. It is anticipated that one or more members of a group may be included in, or deleted from, a group for reasons of convenience and / or patentability. When any such inclusion or deletion occurs, the specification is deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

[0107] Some embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Of course, variations on these described embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than specifically described herein. Accordingly, this invention includes all modifications andequivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

[0108] Furthermore, it is to be understood that the embodiments of the invention disclosed herein are illustrative of the principles of the present invention. Other modifications that may be employed are within the scope of the invention. Thus, by way of example, but not of limitation, alternative configurations of the present invention may be utilized in accordance with the teachings herein. Accordingly, the present invention is not limited to that precisely as shown and described.

Claims

We claim:

1. A process for preparing hydrocarbons, comprising providing a first feed stream comprising carbon dioxide and hydrogen in a first reaction zone, contacting the first feed stream with an iron-based FT catalyst material in the substantial absence of a reverse water-gas shift catalyst material under conditions sufficient to form a first product stream comprising C5+ hydrocarbons, water, carbon dioxide and hydrogen; in a first separation zone, separating at least part of the water of the first product stream to provide a first separated water-rich product stream and a first separated water-poor product stream comprising carbon dioxide and hydrogen; providing a second feed stream comprising at least a portion of the carbon dioxide and at least a portion of the hydrogen of the first separated water-poor product stream; and performing n times, in which n is 0 or an integer that is 1 or more, in n sequentially- arranged pairs of zones each comprising a separation zone and a reaction zone, the following set of operations n times, with each iteration sequentially taking an integer value of x from 1 to n when n is not zero: in the (x+1)th reaction zone, contacting the (x+1)th feed stream with an ironbased FT catalyst material in the substantial absence of a reverse water- gas shift catalyst material under conditions sufficient to form an (x+1)th product stream comprising C5+ hydrocarbons, water, carbon dioxide and hydrogen; in the (x+1)th separation zone, separating at least part of the water of the (x+1)th product stream to provide an (x+1)th separated water-rich product steam and an (x+1)th separated water-poor product stream comprising carbon dioxide and hydrogen; and providing an (x+2)th feed stream comprising at least a portion of the carbon dioxide and at least a portion of the hydrogen of the (x+1)th separated water-poor product stream; and in an (n+2)th reaction zone, contacting the (n+2)th feed stream with an iron-based FT catalyst material in the substantial absence of a reverse water-gas shift catalyst material under conditions sufficient to form an (n+2)th product stream comprising C5+ hydrocarbons, water, carbon dioxide and hydrogen;wherein the process has a single-pass CO2 conversion of at least 70%.

2. The process of claim 1 , wherein n is 0.

3. The process of claim 1 , wherein n is in the range of 1-5.

4. The process of any of claims 1-3, wherein a molar ratio of hydrogen to carbon dioxide in each feed stream is in the range of 1-10.

5. The process of any of claims 1-4, wherein in each of the reaction zones the FT catalyst material is an alkali-promoted iron-based FT catalyst material.

6. The process of any of claims 1-5, wherein in each of the contactings of a feed stream with an iron-based FT catalyst material, the contacting is performed at a temperature in the range of 250-400 °C.

7. The process of any of claims 1-6, wherein in each of the separations, the respective separation is performed such that at least 80% of water of the respective product stream is provided in the respective water-rich product stream.

8. The process of any of claims 1-7, wherein in each of the separations, the respective separation is performed such that at least 80% of C5+ hydrocarbons is provided in the respective water-rich product stream.

9. The process of claim 8, further comprising recovering C5+ hydrocarbons from the respective water rich stream(s).

10. The process of any of claims 1-9, wherein each of the separations is performed by cooling to condense water and optionally C5+ hydrocarbons.11 . The process of claim 10, wherein each of the separations performed by cooling are performed in a respective cooling loop comprising a heat exchanger; a condenser and a product separation vessel, wherein the respective product stream is conducted through the heat exchanger; conducted through the condenser where water and optionally C5+ hydrocarbons are condensed; and conducted to the product separation vessel, from which the respective water-rich product stream is separated from the respective water-poor productstream, which is conducted through the heat exchanger to exchange heat with the respective product stream, then used to provide at least a portion of the carbon dioxide and at least a portion of the hydrogen of the next respective feed stream.

12. The process of any of claims 1-11 , wherein one or more of the second and subsequent feed streams includes hydrogen provided from a source other than the preceding water-poor product stream, and / or wherein one or more of the second and subsequent feed streams includes C1-C4 hydrocarbons from a preceding water-poor product stream.

13. The process of claim 12, wherein the C1-C4 hydrocarbons from the preceding waterpoor product stream are at least 50 mol% olefins.

14. The process of any of claims 1-13, having a single-pass conversion of CO2 of at least 80%.

15. The process of any of claims 1-14, further comprising, in a (n+2)th separation zone, separating at least part of the C1-C4 hydrocarbons of the (n+2)th product stream, and including them in the first feed stream, optionally subjecting them to a dehydrogenation to increase olefin content.

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