Integrated process for co-production of higher hydrocarbons and methanol from co2

Abstract

The present disclosure relates generally to a process for preparing hydrocarbons and methanol. The process includes providing a FT feed stream comprising carbon dioxide and hydrogen; in a FT reaction zone, contacting the FT feed stream with a FT catalyst under conditions sufficient to form a first product stream comprising C5+ hydrocarbons, and carbon monoxide; providing a methanol synthesis feed stream comprising carbon monoxide and hydrogen, the methanol synthesis feed stream comprising at least a portion of the carbon monoxide from the first product stream; and in a methanol synthesis zone, contacting the methanol synthesis feed stream with a methanol synthesis catalyst under conditions sufficient to form a second product stream comprising methanol. The disclosure is especially concerned with implementing the above multi-stage process in a way which is adapted to the relatively low output of carbon monoxide in the first product stream, so as to require no (or minimal) use of a separate extraneous carbon monoxide source. [FIG 1]

Description

[0001] INTEGRATED PROCESS FOR CO-PRODUCTION OF HIGHER HYDROCARBONS AND METHANOL FROM CO2

[0002] FIELD OF THE INVENTION

[0003] The present disclosure relates generally to processes for the conversion of carbon dioxide into useful products, in particular methods based around Fischer-Tropsch synthesis of hydrocarbons.

[0004] BACKGROUND

[0005] The conversion of synthesis gas (i.e., a mixture of carbon monoxide and hydrogen, also known as syngas) into hydrocarbons by the Fischer-Tropsch (FT) 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 FT process as it allows a direct route to high-quality fuels and feedstock chemicals.

[0006] 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. Olefins and alcohols and other oxygenates obtained may also be used as reagents in other processes, such as in the synthesis of lubricants.

[0007] Alongside development of conventional FT processes based on conversion of carbon monoxide and hydrogen, there is growing interest around FT processes in which a mixture of carbon dioxide and hydrogen are used as the feedstock - often referred to as “modified” FT processes. In such processes, a catalyst (typically an iron-based catalyst) is used to convert carbon dioxide to carbon monoxide through the so-called “reverse water-gas shift” (rWGS) reaction

[0008] (CO2 + CO + H2O), with the same catalyst then converting the carbon monoxide to hydrocarbons and oxygenates through a FT reaction. This modified FT approach holds great promise since carbon dioxide is far more readily accessible as a feedstock than carbon monoxide. However, it has been relatively challenging to achieve efficient conversion of CO2 towards C5+ hydrocarbons.

[0009] Thus, there remains a need to identify more efficient routes to products starting from CO2 as a feedstock. SUMMARY OF THE INVENTION

[0010] The present inventors have identified that the product stream from modified FT processes can include reasonable amounts of unreacted carbon monoxide, produced by rWGS. Whilst it is possible to recycle this carbon monoxide back to the modified FT reactor for further production of hydrocarbons, the catalysts used in the modified FT process also have a propensity to convert the carbon monoxide back to carbon dioxide and hydrogen by a competing water-gas shift (WGS) reaction. Furthermore, the inventors have discovered that the presence of carbon monoxide in the feedstock of a modified FT process can lead to preferential conversion of carbon monoxide to higher hydrocarbons over the conversion of carbon dioxide, potentially significantly reducing the productivity of conversion of carbon dioxide.

[0011] In view of this, the present inventors have identified that it can be advantageous to take residual carbon monoxide from the product stream of modified FT processes and feed this to a different reaction zone, which favours the production of methanol. Thus, at its broadest the present invention provides a process for preparing hydrocarbons and methanol, comprising:

[0012] providing an FT feed stream comprising carbon dioxide and hydrogen ;

[0013] in an FT reaction zone, contacting the FT feed stream with an FT catalyst under conditions sufficient to form a first product stream comprising C5+ hydrocarbons and carbon monoxide;

[0014] providing a methanol synthesis feed stream comprising carbon monoxide and hydrogen, the methanol synthesis feed stream comprising at least a portion of the carbon monoxide from the first product stream (and typically residual carbon dioxide from the FT feed stream); and

[0015] in a methanol synthesis zone, contacting the methanol synthesis feed stream with a methanol synthesis catalyst under conditions sufficient to form a second product stream comprising methanol.

[0016] As described above, the present proposals may involve a modified FT process, and a modified FT process herein is one in which CO2 and CO are employed in the FT feed stream. The processes herein may thus make use of a rWGS reaction, which occurs in the FT reaction zone herein, and CO may thereby be produced as a by-product alongside the (target) C5+ hydrocarbon products. Since the CO2 is consumed during the rWGS to form CO in such process, it follows that in the FT reaction zone the proportion of CO may become increased relative to CO2. Using CO2 in the modified FT feed stream means that the first product stream may comprise gases having a greater proportion of CO relative to CO2, than the corresponding relative amount of CO to CO2 in the FT feed stream. Accordingly, in some examples the CO2 of the feed stream of the modified FT process may not be used or intended as an inert gas.

[0017] Synthesis of methanol can occur through hydrogenation of both CO and CO2 according to the following equations:

[0018] 2H2+ CO CH3OH CO2+ 3H2^^ CH3OH + H2O

[0019] In addition, under the conditions used for methanol synthesis, rWGS of CO2can also occur, thereby creating additional CO for use in methanol synthesis.

[0020] Advantageously, by carrying out a multi-stage reaction with the output from the FT reaction zone being used (at least in part) as the feedstock for the methanol synthesis zone, conditions can be chosen to optimise the overall selectivity for desired products. In particular, conditions and catalysts in the different reaction zones can be independently tuned to optimise the selectivity / productivity of the overall reaction.

[0021] In instances where the product of the methanol synthesis step is recycled back to the FT reaction zone, depletion / removal of the carbon monoxide through its use in methanol synthesis avoids the complication of conversion of carbon monoxide acting in competition to conversion of carbon dioxide, in a way which would occur if the product of the FT reaction zone were recycled directly back to the FT reaction zone.

[0022] Whilst the approach of the present invention has the advantage of making more efficient use of the carbon monoxide of the first product stream compared to simply recycling the carbon monoxide back to the FT reaction zone, the inventors have discovered that a particular challenge with using the first product stream to create the methanol synthesis feed stream is that the molar amount of hydrogen relative to carbon monoxide in the first product stream is typically significantly higher than the ideal ratio of 2:1. Specifically, in modified FT processes the amount of residual carbon monoxide in the product stream is typically modest, resulting in the methanol synthesis feed stream being relatively “lean” in terms of carbon monoxide.

[0023] Whilst this can be compensated for by the addition of further extraneous carbon monoxide to the methanol synthesis feed stream, this requires the provision of an additional source of carbon monoxide, which obviates the advantages which comes from using carbon dioxide and hydrogen as the primary feedstocks for the process. Thus, the inventors have identified a number of ways to address this challenge, and the present invention is especially concerned with implementing the above multi-stage process in a way which is adapted to the relatively low output of carbon monoxide in the first product stream, so as to require no (or minimal) use of a separate extraneous carbon monoxide source. In particular, the inventors have identified that the low output of carbon monoxide in the first product stream can be compensated for by:

[0024] (a) adjusting the conditions of the FT reaction zone to control the ratio of hydrogen to carbon monoxide output in the first product stream; and / or

[0025] (b) adjusting the ratio of hydrogen to carbon monoxide in the methanol synthesis zone, e.g.

[0026] through adapting the methanol synthesis feed stream; and / or

[0027] (c) adjusting the conditions of the methanol synthesis zone to cope with a relatively high proportion of hydrogen relative to carbon monoxide. The inventors have identified several implementations for carrying out (a)-(c), which can be used separately or in any combination to boost the overall selectivity and / or productivity of the multi-stage reaction.

[0028] In a particularly preferred first implementation, the present invention provides a process for preparing hydrocarbons, comprising:

[0029] providing a FT feed stream comprising carbon dioxide and hydrogen;

[0030] in a FT reaction zone, contacting the FT feed stream with a FT catalyst under conditions sufficient to form a first product stream comprising C5+ hydrocarbons and carbon monoxide;

[0031] providing a methanol synthesis feed stream comprising carbon monoxide and hydrogen (and typically carbon dioxide), the methanol synthesis feed stream comprising at least a portion of the carbon monoxide from the first product stream (and typically residual carbon dioxide from the FT feed stream which is present in the first product stream); and in a methanol synthesis zone, contacting the methanol synthesis feed stream with a methanol synthesis catalyst under conditions sufficient to form a second product stream comprising methanol (at least from conversion of the carbon monoxide to methanol and, where carbon dioxide is present in the methanol synthesis feed stream, ideally through conversion of the carbon dioxide to methanol);

[0032] wherein the methanol synthesis feed stream has a molar ratio of hydrogen to carbon monoxide in the range of 1:2 to 10:1, preferably 1:2 to 8:1, more preferably 1:1 to 5:1. Advantageously, keeping the hydrogen to carbon monoxide ratio in the methanol synthesis feed stream within these ranges ensures that the productivity and selectivity for production of methanol in the methanol synthesis zone is at a good level. The present inventors have identified a number of ways to help to achieve a molar ratio of hydrogen to carbon monoxide within the above ranges in the methanol synthesis feed stream, which can be implemented separately or together.

[0033] In a first proposal, the FT reaction zone is operated under conditions to bring the ratio of hydrogen to carbon monoxide in the first product stream closer towards the ratio of 2:1. This can be achieved, for example, by flowing the FT feed stream through the FT reaction zone at a relatively high volumetric flow rate, having a relatively low hydrogemcarbon dioxide molar ratio, and operating the reaction at a temperature intermediate between those typically used for FT and those typically used for rWGS.

[0034] For example, the FT reaction zone may operate under at least one of the following conditions:

[0035] • a ratio of hydrogen to carbon dioxide of less than 4:1 , preferably less than 3:1 , more preferably less than 2:1 , e.g. between 0.5:1 to 4:1, 0.5:1 to 3:1, or 0.5:1 to 2:1 ;

[0036] • a temperature of greater than 250°C; a pressure of 10 to 100 barg (e.g. 10 to 80 barg or 10 to 40 barg); and / or a GHSV of greater than 2,000 tr1.

[0037] Whilst certain implementations may rely entirely on adjustment of the FT feed stream and reaction conditions in the FT reaction zone to generate a suitable ratio of hydrogen and carbon monoxide for providing to the methanol synthesis zone, in generally preferred implementations, the multi-stage process is carried out such that the molar ratio of hydrogen to carbon monoxide in the methanol synthesis feed stream is adjusted to be lower than the molar ratio of hydrogen to carbon monoxide in the first product stream.

[0038] For example, the molar ratio of hydrogen to carbon monoxide in the methanol synthesis zone may be adjusted by selectively reacting / removing hydrogen from the first product stream.

[0039] As an example of such an approach, in a second proposal, the molar ratio of hydrogen to carbon monoxide in the methanol synthesis feed stream is adjusted by selectively removing hydrogen from the first product stream so as to produce a modified product stream having a decreased molar ratio of hydrogen to carbon monoxide, and using this modified product stream to form the methanol synthesis feed stream.

[0040] Selective removal of hydrogen may be achieved by separation methods. In other words, the method may involve subjecting the first product stream to a separation method to selectively remove hydrogen. This method can separate the first product stream into a hydrogen rich (or pure) stream and a hydrogen depleted stream, wherein the hydrogen depleted stream is used to form the methanol synthesis feed stream. Advantageously, the hydrogen rich (or pure) stream can be recycled to the FT reaction zone.

[0041] Separation of hydrogen from the first product stream may be carried out by any suitable method. For example, separation may be achieved using a hydrogen selective membrane, e.g. a hydrogen permeable membrane. Alternatively, separation may be achieved using swing adsorption, e.g. pressure swing adsorption.

[0042] Additionally, or alternatively, the molar ratio of hydrogen to carbon monoxide is adjusted by selectively reacting hydrogen from the first product stream. This may be achieved without the need for separation.

[0043] For example, hydrogen from the first product stream can be consumed through a hydrogenation reaction with a suitable reactant (other than carbon monoxide or carbon dioxide), without affecting the level of carbon monoxide, to reduce the molar ratio of hydrogen to carbon monoxide in the methanol synthesis zone. Examples of suitable reactants include, for example, light olefins, such as C2-C4 olefins.

[0044] Selective reaction of hydrogen from the first product stream may occur prior to introduction of the methanol synthesis feed stream to the methanol synthesis zone - e.g., in a separate hydrogenation zone / unit / reactor. Preferably, however, reaction of hydrogen occurs within the methanol synthesis zone, since this avoids the need for a separate zone / unit / reactor. Typically, reaction of hydrogen from the first product stream will be a catalysed reaction, e.g. a catalysed hydrogenation reaction. In instances where the reaction of hydrogen occurs within the methanol synthesis zone, the methanol synthesis catalyst may also serve as the hydrogenation catalyst for the additional reactant.

[0045] The reactant for reacting with hydrogen may be added to the first product stream or obtained from the first product stream. Preferably, the reactant for reacting with hydrogen is obtained from (e.g. a component of) the first product stream.

[0046] Preferably, the reactant is a C2-C4 olefin from the first product stream. With this in mind, it is preferred that unsaturated C2-C4 hydrocarbons constitute a relatively high proportion of the total C1-C4 hydrocarbons in the first product stream. For example, unsaturated hydrocarbons may account for at least 10 mol%, preferably at least 20 mol%, more preferably at least 30 mol%, e.g. at least 40 mol% of the total C1-C4 hydrocarbons in the first product stream, and said unsaturated hydrocarbons are included in the methanol synthesis feed stream.

[0047] Additionally or alternatively, C2-C4 olefins may be added to the methanol synthesis feed stream from an alternative (e.g. extraneous) source, such as from a steam cracker, a fluid catalytic cracker (FCC), or from an alcohol dehydration stream.

[0048] The molar ratio of hydrogen to C2-C4 olefins used in the hydrogenation reaction may be in the range of 2: 1 to 30: 1 , for example 2: 1 to 20: 1 , such as 5: 1 to 30: 1 or 5: 1 to 20: 1. For example, in instances where hydrogenation occurs in the methanol synthesis zone, the molar ratio of hydrogen to C2-C4 olefins in the methanol synthesis feed stream may be in the range of 2:1 to 30: 1 , for example 2: 1 to 20: 1.

[0049] In a fourth proposal, the molar ratio of hydrogen to carbon monoxide in the methanol synthesis feed stream is adjusted by selectively reacting a component of the first product stream to form additional carbon monoxide. Preferably, the molar ratio of hydrogen to carbon monoxide in the methanol synthesis feed stream is adjusted by converting C1-C4 hydrocarbons of the first product stream to produce carbon monoxide, and including this carbon monoxide in the methanol synthesis feed stream.

[0050] Conversion of the C1-C4 hydrocarbons may be carried out, for example, by reforming.

[0051] Reforming may be, for example, partial oxidation, steam reforming or dry CO2 reforming. The equations for these reactions are:

[0052] Partial Oxidation CnHm+ (n / 2)O2nCO + (m / 2)H2Steam Reforming

[0053]

[0054] Dry CO2 reforming

[0055]

[0056] From these formulae it can be seen that the ratio of carbon monoxide to hydrogen produced by the conversion increases with the number of carbon atoms in the hydrocarbon, and that higher levels can be produced by partial oxidation or dry CO2 reforming. In one embodiment, the reforming is partial oxidation. In one embodiment, the reforming is steam reforming. In one embodiment, the reforming is CO2 reforming.

[0057] Additionally or alternatively, the molar ratio of hydrogen to carbon monoxide in the methanol synthesis feed stream is adjusted compared to the first product stream by adding carbon monoxide to the methanol synthesis feed stream from an external source.

[0058] As well as adjusting conditions and components upstream of the methanol synthesis zone to optimise the molar ratio of hydrogen to carbon monoxide, the present invention also envisages operating the methanol synthesis zone under conditions compatible with the methanol synthesis feed stream being relatively lean in carbon monoxide. In particular, a fifth proposal involves operating the methanol synthesis zone at a temperature of between 150 to 400°C. Suitable temperature ranges are, for example, 200 to 400°C, optionally 250 to 400°C, such as 250-350°C. The pressure may be, for example, in the range of 10-200 barg.

[0059] Optionally, the pressure is chosen to aid process integration of the FT and methanol synthesis steps. For example, the pressure of the FT step may be within 20%, e.g. within 10% of the pressure of the methanol synthesis step - differently stated, the pressure of the FT step may be within 50 barg, within 40 barg or within 20 barg of the methanol synthesis step, or may be carried out at the same pressure. As an example, both the FT step and the methanol synthesis step may be carried out at a pressure of 10-200 barg, e.g. 50-200 barg. Advantageously, carrying out the FT step and methanol synthesis step at the same or similar pressure can allow the same compressor to be used to achieve the desired pressure in both steps.

[0060] The skilled reader will understand that all of the proposals above can be combined in order to boost productivity and / or selectivity of the overall reaction.

[0061] The various proposals above also constitute separate aspects of the invention.

[0062] For example, in a second implementation the present invention provides a process for preparing hydrocarbons, comprising:

[0063] providing a FT feed stream comprising carbon dioxide and hydrogen;

[0064] in a FT reaction zone, contacting the FT feed stream with a FT catalyst under conditions sufficient to form a first product stream comprising C5+ hydrocarbons and carbon monoxide;

[0065] providing a methanol synthesis feed stream comprising carbon monoxide and hydrogen, the methanol synthesis feed stream comprising at least a portion of the carbon monoxide of the first product stream (and typically unreacted carbon dioxide from the first product stream); and

[0066] in a methanol synthesis zone, contacting the methanol synthesis feed stream with a methanol synthesis catalyst at a temperature of between 150 to 400°C to form a second product stream comprising methanol. In a third implementation the present invention provides a process for preparing hydrocarbons, comprising:

[0067] providing a FT feed stream comprising carbon dioxide and hydrogen;

[0068] in a FT reaction zone, contacting the FT feed stream with a FT catalyst under conditions sufficient to form a first product stream comprising C5+ hydrocarbons and carbon monoxide;

[0069] providing a methanol synthesis feed stream comprising carbon monoxide and hydrogen, the methanol synthesis feed stream comprising at least a portion of the carbon monoxide of the first product stream; and

[0070] in a methanol synthesis zone, contacting the methanol synthesis feed stream with a methanol synthesis catalyst under conditions sufficient to form a second product stream comprising methanol;

[0071] wherein the FT reaction zone operates under at least one of the following conditions:

[0072] • a molar ratio of hydrogen to carbon dioxide of less than 4:1 , preferably less than 3:1, more preferably less than 2:1;

[0073] • a temperature of greater than 250°C;

[0074] • a pressure of 10 to 100 barg (e.g. 10 to 80 barg or 10 to 40 barg); and • a GHSV of greater than 2,000 tr1.

[0075] In a fourth implementation the present invention provides a process for preparing hydrocarbons, comprising:

[0076] providing a FT feed stream comprising carbon dioxide and hydrogen;

[0077] in a FT reaction zone, contacting the FT feed stream with a FT catalyst under conditions sufficient to form a first product stream comprising C5+ hydrocarbons and carbon monoxide;

[0078] selectively removing hydrogen from the first product stream so as to decrease the ratio of hydrogen to carbon monoxide to form a modified FT product stream;

[0079] providing a methanol synthesis feed stream comprising carbon monoxide and hydrogen, the methanol synthesis feed stream comprising at least a portion of the modified FT product stream; and

[0080] in a methanol synthesis zone, contacting the methanol synthesis feed stream with a methanol synthesis catalyst under conditions sufficient to form a second product stream comprising methanol.

[0081] In a fifth implementation the present invention provides a process for preparing hydrocarbons, comprising: providing a FT feed stream comprising carbon dioxide and hydrogen;

[0082] in a FT reaction zone, contacting the FT feed stream with a FT catalyst under conditions sufficient to form a first product stream comprising C5+ hydrocarbons, C1-C4 hydrocarbons, and carbon monoxide;

[0083] reforming at least a portion of the C1-C4 hydrocarbons of the first product stream to form carbon monoxide;

[0084] providing a methanol synthesis feed stream comprising carbon monoxide and hydrogen, the methanol synthesis feed stream comprising at least a portion of the carbon monoxide of the first product stream and carbon monoxide obtained through said reforming of C1-C4 hydrocarbons; and

[0085] in a methanol synthesis zone, contacting the methanol synthesis feed stream with a methanol synthesis catalyst under conditions sufficient to form a second product stream comprising methanol.

[0086] In a sixth implementation the present invention provides process for preparing hydrocarbons, comprising

[0087] providing a FT feed stream comprising carbon dioxide and hydrogen;

[0088] in a FT reaction zone, contacting the FT feed stream with a FT catalyst under conditions sufficient to form a first product stream comprising C5+ hydrocarbons and carbon monoxide;

[0089] providing a methanol synthesis feed stream comprising carbon monoxide and hydrogen, the methanol synthesis feed stream comprising at least a portion of the carbon monoxide of the first product stream; and

[0090] in a methanol synthesis zone, contacting the methanol synthesis feed stream with a methanol synthesis catalyst under conditions sufficient to form a second product stream comprising methanol;

[0091] wherein providing the methanol synthesis feed stream comprises adding C2-C4 olefins alongside at least a portion of the first product stream.

[0092] Given the aims of the present application set out above, the multi-stage reaction may be carried out without adding additional components subsequent to introduction of the FT feed stream. In particular, whilst carbon monoxide may be fed into the reaction as part of the FT feed stream, the multi-stage reaction may be carried out without addition of carbon monoxide from an extraneous source subsequent to introduction of the FT feed stream.

[0093] Optionally, at least 60%, preferably at least 70%, more preferably at least 80%, more preferably at least 90%, most preferably all of the methanol synthesis feed stream is derived solely from the first product stream (i.e. without the addition of further components) and / or components recycled from the methanol synthesis stage or subsequent stages. Preferably, the first product stream is separated to provide a C5+ hydrocarbon rich stream and a C5+ hydrocarbon poor stream, wherein at least a portion (e.g. at least 20%, at least 30%, at least 40%, at least 50, at least 75%, at least 80%, at least 90%, optionally all) of the C5+ hydrocarbon poor stream is provided to (i.e. used to form) the methanol synthesis feed stream. Preferably, the first product stream is separated to provide a water rich stream and a water poor stream, wherein at least a portion (e.g. at least 20%, at least 30%, at least 40%, at least 50, at least 75%, at least 80%, at least 90%, optionally all) of the water poor stream is provided to (i.e. used to form) the methanol synthesis feed stream.

[0094] Preferably, the first product stream is separated in a condensate separation zone to provide a product stream enriched in water and C5+ hydrocarbons, and a condensate-poor product stream lean in water and C5+ hydrocarbons, wherein at least a portion of (e.g., all of) the condensatepoor product stream is provided to the methanol synthesis feed stream.

[0095] Preferably, separation of C5+ hydrocarbons and / or water occurs upstream of any hydrogen separation of the first product stream. This approach can increase efficiency of the hydrogen separation process.

[0096] For the avoidance of doubt, the FT reaction zone is separate to the methanol synthesis zone. The methanol synthesis zone is downstream of the FT reaction zone.

[0097] Suitably, the FT reaction zone is provided in a first reactor and the methanol synthesis zone is provided in a second reactor. Advantageously, this arrangement simplifies interventions between the FT reaction zone and methanol synthesis zone to adjust the ratio of hydrogen to carbon monoxide.

[0098] Suitably the FT catalyst is a catalyst suitable for carrying out modified FT reaction - that is, a catalyst having both activity for FT and activity for the rWGS reaction. The FT catalyst may comprise iron. Advantageously, iron-based catalysts are well-suited for use in the FT reaction zone due to their activity for both rWGS and FT (required for the modified FT process).

[0099] Preferably, the FT catalyst comprises at least 20 wt% iron.

[0100] The methanol synthesis catalyst is not particularly limited, and the skilled reader will be familiar with suitable options. The methanol synthesis catalyst is a catalyst suitable for conversion of carbon monoxide to methanol, ideally with a high mol% selectivity (e.g. more than 40%, more than 50% or more than 60%) for conversion of carbon monoxide to methanol. Preferably, the methanol synthesis catalyst is suitable for conversion of both carbon monoxide and carbon dioxide, ideally with a high mol% selectivity (e.g. more than 40%, more than 50% or more than 60%) for conversion of carbon monoxide and carbon dioxide to methanol. The methanol synthesis catalyst may comprise, for example, copper, optionally in conjunction with one or more co-catalysts and / or promoters. For example, the methanol synthesis catalyst may include copper, preferably copper and zinc, optionally alongside at least one of magnesium, zirconia or alumina. For example, the methanol synthesis catalyst may be a copper oxide-zinc oxide catalyst, optionally including zirconia or alumina. Such catalysts are available commercially for methanol synthesis, for example, T-2130 available from Slid Chemie (having the composition: 33 wt% CuO and 66 wt% ZnO). Alternatively or additionally, the methanol synthesis catalyst may comprise molybdenum, for example, it may be a molybdenum sulphide-based catalyst, such as a cobalt molybdenum sulphide catalyst. Advantageously, such catalysts can achieve conversion of both carbon monoxide and carbon dioxide at high methanol selectivities.

[0101] Suitably, the FT catalyst is different from the methanol synthesis catalyst.

[0102] In particularly preferred embodiments, the FT catalyst is an iron-based catalyst and the methanol synthesis catalyst is a copper-based catalyst.

[0103] Optionally, the FT reaction zone includes only a single catalyst type. In other words, the FT catalyst may be a single catalyst type. Differently stated, the FT catalyst may not comprise a mixture of catalyst, for example may not be a co-mingled mixture of two or more catalysts. Optionally, the methanol synthesis zone includes only a single type of catalyst. In other words, the methanol synthesis catalyst may be a single catalyst type. Differently stated, the methanol synthesis catalyst may not comprise a mixture of catalyst, for example may not be a co-mingled mixtures of two or more catalysts.

[0104] For the avoidance of doubt, the FT catalyst has both rWGS and FT activity. The FT activity means that C2+ hydrocarbons account for a substantial portion of the first product stream, and in particular that C5+ hydrocarbons account for a substantial portion of the first product stream. For example, the contacting of the FT feed stream with the FT catalyst in the FT reaction zone may be conducted with a C5+ selectivity (I. e. , for all C5+ species) of at least 40%, e.g., at least 50%, or at least 60%.

[0105] The first product stream preferably comprises at least 5 mol%, at least 10 mol%, at least 20 mol% or at least 30 mol% of C5+ hydrocarbons.

[0106] Preferably, the FT step is performed with high selectivity for C5+ hydrocarbons over other carbon products (i.e. with minimal formation of side-products including methane) - that is with high carbon product selectivity for C5+ hydrocarbons. When referring to “carbon product selectivity” of the decomposition process for a particular component, we mean the space time yield (STY) of the component as a percentage of the STY for all carbon-containing products from the FT step. In this disclosure, STY is reported as the grammes of product produced per kilogramme of catalyst per hour (space time yield weight, or STYW), although those skilled in the art will recognise that the carbon product selectivity is a percentage which is independent of the particular units used for the STY.

[0107] Preferably, the FT step is performed with a carbon product selectivity of at least 40% for C5+ hydrocarbons (for all C5+ species), e.g., at least 50%, at least 60% or at least 70% for C5+ hydrocarbons.

[0108] The second product stream preferably comprises at least 20 mol% methanol, preferably at least 30 mol% methanol, more preferably at least 40 mol% methanol. Preferably, the methanol synthesis step is performed with high selectivity for methanol over other carbon products (i.e. with minimal formation of side-products including methane) - that is with high carbon product selectivity for methanol. When referring to “carbon product selectivity” of the decomposition process for a particular component, we mean the space time yield (STY) of the component as a percentage of the STY for all carbon-containing products from the methanol synthesis step. In this disclosure, STY is reported as the grammes of product produced per kilogramme of catalyst per hour (space time yield weight, or STYW), although those skilled in the art will recognise that the carbon product selectivity is a percentage which is independent of the particular units used for the STY.

[0109] Preferably, the methanol synthesis step is performed with a carbon product selectivity of at least 20% for methanol, e.g., at least 30%, at least 40%, at least 50%, at least 60% or at least 70% for methanol.

[0110] In contrast to the FT step, the level of C5+ hydrocarbons produced in the methanol synthesis step may be relatively low. For example, the second product stream may comprise no more than 10 mol% C5+ hydrocarbons, optionally no more than 5 mol% C5+ hydrocarbons, optionally less than 1 mol% C5+ hydrocarbons.

[0111] The method may involve generating a recyclate stream from the first product stream between the FT reaction zone and methanol synthesis zone, wherein the recyclate stream is recycled back to the FT reaction zone. Such a recyclate stream may be referred to as an “FT zone recyclate stream”. Preferably, however, this FT zone recyclate stream does not contain carbon monoxide, or contains carbon monoxide at only a minimal level (e.g. less than 3 mol%, less than 2 mol% or less than 1 mol% of the FT zone recyclate stream), due to the carbon monoxide being fed onwards to the methanol synthesis zone. Optionally, there is no FT zone recyclate stream.

[0112] Optionally, the method may involve generating a recyclate stream from the second product stream, after the methanol synthesis zone. This recyclate stream may be referred to as a “methanol synthesis zone recyclate stream”. The methanol synthesis zone recyclate stream may be delivered to the FT reaction zone, for example through combination with the FT feed stream. Alternatively or additionally, the methanol synthesis zone recyclate stream may be delivered to the methanol synthesis zone, for example through combination with the methanol synthesis feed stream. Preferably, however, this methanol synthesis zone recyclate stream does not contain carbon monoxide, or contains carbon monoxide at only a minimal level (e.g. less than 3 mol%, less than 2 mol% or less than 1 mol% of the FT zone recyclate stream), due to the carbon monoxide being converted to products in the methanol synthesis zone.

[0113] In order to obtain particularly advantageous conversions of CO2 and CO and form an especially desirable first product stream, the inventors contemplate controlling conditions such as, but not limited to, (i) molar ratio of hydrogen to carbon dioxide in the FT feed stream, (ii) FT catalyst composition to provide desired functionality, and / or (iii) temperature of operation of the FT synthesis. Specifically identified are (I) a molar ratio of hydrogen to carbon dioxide in the FT feed stream of no more than 20:1 and / or (ii) a FT catalyst comprising iron; and / or (iii) temperature of the FT reaction zone in the range of 200-500°C. Each of these may be further limited by the options and preferences set out later. Explicitly mentioned is a combination of (I) and (ii), and (j) in combination with (ii) and (iii). Also contemplated is a combination of (ii) and (iii).

[0114] The invention includes the combination of the aspects, implementations, proposals and preferred features described except where such a combination is clearly impermissible or expressly avoided.

[0115] BRIEF DESCRIPTION OF THE FIGURES

[0116] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

[0117] FIG. 1 is a schematic view of an embodiment of a process for performing a process as described herein, with the FT reaction zone being provided in a first reactor, and the methanol synthesis zone being provided in a downstream second reactor.

[0118] FIG. 2 is a schematic view of an embodiment of a process for performing a process as described herein, similar to that depicted in FIG. 1, showing catalyst activation streams and separation of products from the FT reaction zone.

[0119] FIG. 3 is a schematic view of an alternative embodiment of a process for performing a process as described herein, where the FT reaction zone and methanol synthesis zone are carried out in the same reactor, with the methanol synthesis zone being downstream from the FT reaction zone, and additionally showing options for heat exchange between components of the system. FIG. 4 is a schematic view of an embodiment of a process for performing a process as described herein, similar to FIG. 1 and 2, but showing further details of the heat exchange system.

[0120] FIG. 5 is a schematic view of an embodiment of a process for performing a process as described herein, similar to FIG. 1 and 2, and showing further details of heat exchange and processing of the product streams.

[0121] FIG. 6 is a schematic view of an embodiment of a process for performing a process as described herein, similar to FIG. 1 and 2, and showing the incorporation of a partial oxidation unit downstream of the second reactor.

[0122] FIG. 7 is a schematic view of an embodiment of a process for performing a process as described herein, in which the first product stream is fed through a hydrogen separation membrane, thereby creating a methanol synthesis feed stream having a reduced molar ratio of hydrogemcarbon monoxide. FIG. 8 is a schematic view of an embodiment of a process for performing a process as described herein, showing combination of a light olefin stream into the methanol synthesis feed stream to adjust the hydrogemcarbon monoxide molar ratio within the second reactor.

[0123] FIG. 9 is a schematic view of an embodiment of a process for performing a process as described herein, in which the first product stream is fed through a partial oxidation unit, thereby creating a methanol synthesis feed stream having a reduced molar ratio of hydrogemcarbon monoxide.

[0124] FIG. 10 is a schematic view of an embodiment of a process for performing a process as described herein, incorporating both a partial oxidation unit and hydrogen separation membrane.

[0125] FIGs. 11 and 12 are plots showing the effect of the ratio of hydrogen :carbon dioxide in the feed stream of an iron-catalysed modified FT process on the molar ratio of hydrogemcarbon monoxide in the product stream.

[0126] FIG. 13 is a plot showing the effect of reactor temperature on the molar ratio of hydrogemcarbon monoxide in the product stream of an iron-catalysed modified FT process. FIG. 14 is a plot showing the effect of reactor pressure on the molar ratio of hydrogemcarbon monoxide in the product stream of an iron-catalysed modified FT process.

[0127] FIG. 15 is a plot showing the effect of GHSV on the molar ratio of hydrogen :carbon monoxide in the product stream of an iron-catalysed modified FT process.

[0128] DETAILED DESCRIPTION OF THE INVENTION

[0129] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

[0130] The present disclosure is concerned with processes for converting CO2 to hydrocarbons and methanol.

[0131] The present inventors have noted that the overall conversion of CO2 to hydrocarbons in modified FT processes can be 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 lower level. This is exacerbated by the fact that there is H2O produced by the Fischer-Tropsch reaction, shown below:

[0132] CO + 2 H2-> [-CH2-] + H2O

[0133] This water can push the water-gas shift equilibrium toward CO2, i.e., in the “forward” direction, thus limiting the amount of CO available for conversion to products. Accordingly, while the high water-gas shift activity of FT catalysts can be helpful to convert CO2 to CO for use in Fischer-Tropsch synthesis, the latter reaction makes water, which can cause CO to shift back to CO2. This can provide for an overall limit on the conversion of feedstock carbon to C5+ hydrocarbons, which are the generally-desired FT products.

[0134] Thus, the present inventors note that one of the challenges associated with using CO2 in the feed stream of modified-FT processes is to ameliorate the problem of lower-than-desired overall conversion of CO2 into C5+ products. Here, the present inventors have determined that the reverse water-gas shift / water-gas shift activity of FT catalysts can be used to provide better C5+ conversion in FT processes. To do so, the present inventors have determined that the combination of a first FT stage with a closely-coupled downstream second methanol synthesis stage can provide increased overall CO2 conversion into useful products. This scheme allows the first FT stage to be operated in manner that provides a good compromise between CO2 conversion and C5+ selectivity without regarding co-produced CO as an undesired by-product. This is because the closely-coupled second methanol synthesis stage can provide high conversion of CO from the first FT stage.

[0135] Moreover, the inventors have recognised that the molar amount of carbon monoxide exiting the first FT stage can be significantly lower than the molar amount of hydrogen, meaning that the second methanol synthesis stage operates far away from the optimal ratio of ~2:1 hydrogemcarbon monoxide. Thus, the present disclosure is especially concerned with implementations of the multi-stage process which maximise productivity and selectivity of the process as a whole, in particular through adjusting conditions to bring the ratio of hydrogemcarbon monoxide in the methanol synthesis stage closer to the optimal value of 2:1. As noted in the summary of the invention section above, and described in more detail below, the present invention encompasses various proposals for achieving this, based on:

[0136] (a) adjusting the conditions of the FT reaction zone to control the ratio of hydrogen to carbon monoxide output in the first product stream; and / or

[0137] (b) adjusting the ratio of hydrogen to carbon monoxide in the methanol synthesis zone, e.g.

[0138] through adjusting the methanol synthesis feed stream; and / or

[0139] (c) adjusting the conditions of the methanol synthesis zone to cope with a relatively high proportion of hydrogen relative to carbon monoxide.

[0140] An example of a multi-stage process according to the invention is shown schematically in FIG.

[0141] 1. In FIG. 1, the process 100 includes providing a FT feed stream 111 comprising carbon dioxide and hydrogen, here, to a FT reaction zone, e.g., a reactor 110. A FT catalyst 113 is contacted with the FT feed stream 111 under conditions sufficient to form a first product stream 112 comprising C5+ hydrocarbons and carbon monoxide. The process of this aspect of the disclosure also provides a methanol synthesis feed stream comprising carbon monoxide (at least a portion of which is from the first product stream) and contacts the methanol synthesis feed stream with a methanol synthesis catalyst to form a second product stream. In the process 100 of FIG. 1, at least a portion of carbon monoxide of the first product stream 112 is included in methanol synthesis feed stream 121, which is contacted with the methanol synthesis catalyst 123, here, in a methanol synthesis zone (e.g., a reactor 120). This provides a second product stream 122, which includes methanol.

[0142] 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.

[0143] 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 FT feed stream can be provided to the FT catalyst 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 H2and another for recycled carbon dioxide and / or H2).

[0144] As used herein, the term “hydrocarbons” is used as a term to describe FT synthesis products. It includes not only alkanes and olefins, but also the oxygenated hydrocarbons (e.g., alcohols) that are often present to some extent in FT product streams.

[0145] FT feed stream

[0146] As described above, the FT feed stream contains both H2and CO2(e.g., provided to a reaction zone in a single physical stream or multiple physical streams).

[0147] The molar ratio of H2to CO2in the FT feed stream may be at least 0.1:1, e.g., at least 0.5:1. For example, the molar ratio of H2to CO2in the FT feed stream may be at least 0.9:1, e.g., at least 1:1 or at least 1.5:1. Preferably, the molar ratio of H2to CO2in the FT feed stream is no more than 20:1, e.g., no more than 15:1 or no more than 10:1. For example, the molar ratio of H2to CO2in the FT feed stream may be in the range of 1:1 to 6:1, e.g., in the range of 1.5:1 to 3:1. Preferably, the molar ratio of hydrogen to carbon dioxide is less than 4:1 , preferably less than 3:1, more preferably less than 2:1 , e.g. between 0.5:1 to 4:1 , 0.5:1 to 3:1 , or 0.5:1 to 2:1. The person of ordinary skill in the art will provide a desired ratio of H2:CO2in the FT feed stream, based on the disclosure herein, that provides a desirable conversion and selectivity; excess H2can, if consistent with a desirable conversion and selectivity, be provided to flow through the system and provide a first product stream with a desirable ratio of H2to CO for the methanol synthesis process.

[0148] Other gases may also be included in the FT feed stream. For example, in some embodiments, the FT feed stream further comprises CO. According to certain processes, the process used to generate hydrogen and carbon dioxide may result in the product of other gases which are included in the FT feed stream - for example, syngas derived from biomass gasification directly produces a mixture of H2, CO and CO2which can be used to form the FT feed stream.

[0149] Furthermore, in instances where the FT feed stream includes a recyclate stream, for example a recyclate from the methanol synthesis stage, this can lead to the introduction of additional gas components, include residual CO from the methanol synthesis. 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. The present inventors hypothesize that including CO in the FT feed stream can provide a compromise between the rWGS reaction and the FT reaction to provide the desired hydrocarbons.

[0150] The amounts of various feed components can be selected to provide a desirable balance of CO2 conversion and C5+ selectivity. The present inventors note that while hydrogen is necessary for the reverse water-gas shift reaction that forms CO for Fischer-Tropsch synthesis, higher ratios of hydrogen to oxides of carbon can provide for relatively shorter chain hydrocarbons, thus decreasing selectivity for the highly desirable C5+ hydrocarbons.

[0151] Accordingly, the FT feed stream may have 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. For example, the FT feed stream may have a ratio of hydrogen to oxides of carbon in the range of 1 :1 to 3:1. Moreover, proportions in the feed stream of H2, CO and CO2may be selected such that the molar ratio H2 / (2CO + 3CO2) is in excess of 0.5; the present inventors have found that this can help to ensure a positive conversion of CO2. The molar ratio CO2 / (CO+CO2) is desirably at least 0.33, e.g., at least 0.4, or at least 0.45, or at least 0.5; this, too, can help to ensure positive conversion of CO.

[0152] The FT feed stream may further comprise one or more inert gases. For example, the FT feed stream may further comprise nitrogen and / or methane. For example, it can be desirable to perform the FT process step in the presence of a significant amount of inerts (i.e., components that are not H2or CO2). For example, the FT feed stream may include 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. The FT feed stream may include 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. Optionally, the FT 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%.

[0153] It can be desirable to reduce the amount of water present in the FT feed stream to control the WGS / rWGS activity of the FT catalyst. Accordingly, the FT feed stream may have 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 stability.

[0154] First product stream

[0155] The process described herein provides high CO2conversion. As used herein, a “conversion” is a molar fraction of a relevant component feed that is converted to products (be it to desirable products or undesirable species). Preferably, the FT reaction zone has a CO2 conversion of at least 5%, e.g., at least 10%, or at least 20%. Optionally, the FT reaction zone has a CO2 conversion of no more than 60%, e.g., no more than 55%, or no more than 50%. For example, the FT reaction zone may have a CO2 conversion of no more than 45%, e.g., no more than 40%. The CO2 conversion may be in the range of 5-60%, e.g., 5-55%, or 5-50%, or 5-45%, or 5-40%, or 10-60%, or 10-55%, or 10-50%, or 10-45%, or 10-40%, or 15-60%, or 15-55%, or 15-50%, or 15-45%, or 15-40%, or 20-60%, or 20-55%, or 20-50%, or 20-45%, or 20-40%. 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 distribution. Notably, under conditions where there is significant selectivity for CO, e.g., under lower H2 / CO2 ratios, lower temperature ranges and higher GHSV values, CO2 conversion is generally modest. This is acceptable, as CO will be substantially reacted in the subsequent methanol synthesis stage, and CO2 can pass through the subsequent methanol synthesis stage and be recycled to be converted in a subsequent pass.

[0156] The process as described herein includes contacting a FT catalyst with the FT feed stream to perform an FT reaction. Notably, the present inventors have determined that the FT catalyst, under the conditions described herein, can provide desirably high C5+ selectivity. As used herein, selectivity is the molar fraction of converted material that is converted to a particular product. In other words, unless stated otherwise “selectivity” corresponds to the molar amount of a particular component as a fraction of the total amount of product output by a particular reaction (i.e. as a proportion of the first product stream or second product stream). The skilled reader will be familiar with calculating these amounts, and how to subtract the contribution from any components which are not the product of a reaction taking place in the reaction zone (for example, if a component is added to a feed stream then the contribution from this is subtracted from the amount detected in the product stream). The Fischer-Tropsch process is typically used to make C5+ hydrocarbons, for example, unsubstituted C5+ hydrocarbons (e.g., alkanes and alkenes) and oxygenated C5+ hydrocarbons (e.g., C5+ alcohols, aldehydes, ketones, carboxylic acids).

[0157] Preferably, the contacting of the FT feed stream with the FT catalyst in the FT 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, the selectivity for C5+ alkanes may be at least 40%, e.g., at least 50%, or at least 60%. Optionally, the contacting of the FT catalyst with the FT feed stream to provide the first product stream is performed with a C2-4 selectivity of no more than 30%, e.g., no more than 25%, or no more than 20%. Optionally, the contacting of the FT catalyst with the FT feed stream to provide the first product stream 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%. Optionally, the contacting of the FT catalyst with the FT feed stream to provide the first product stream is performed with a C2-8 oxygenate selectivity of no more than 30%, e.g., no more than 25%, or no more than 20%. Optionally, the contacting of the FT catalyst with the FT feed stream to provide the first product stream is performed with a C2-8 oxygenate selectivity of no more than 15%, e.g., no more than 10%, or no more than 5%.

[0158] In conventional modified FT processes, CO production due to rWGS activity of the catalyst is considered an unwanted by-product. Here, however, the present inventors have found that any CO produced can be provided to the methanol synthesis zone for further processing. Thus, the FT catalyst under the conditions described herein has selectivity for CO, i.e. , significant amounts of CO can be output in the first product stream. For example, the contacting of the FT feed stream with the FT catalyst in the FT reaction zone may be conducted with an overall CO selectivity of at least 10%. For example, the contacting in the FT reaction zone is conducted with an overall CO selectivity of at least 15% or at least 20%. Optionally, the contacting of the FT feed stream with the FT catalyst in the FT reaction zone is conducted with an overall CO selectivity of no more than 80%, e.g., no more than 60%, or no more than 50%, or no more than 40%. For example, the contacting of the FT feed stream with the FT catalyst in the FT reaction zone may be conducted with an overall CO selectivity in the range of 10-80%, e.g., 15-80%, or 20-80%, or 10-60%, or 15-60%, or 20-60%, or 10-50%, or 15-50%, or 20-50%, or 10-40%, or 15-40%, or 20-40%.

[0159] Temperature of the FT reaction zone

[0160] Contacting of the FT feed stream with the FT catalyst in the FT reaction zone may be conducted at a temperature in the range of 200-500°C. For example, the contacting may be conducted at a temperature in the range of 200-450 °C, e.g., 200-400 °C, or 200-350 °C, or 200-300 °C, or 225-500 °C, or 225-450 °C, or 225-400 °C, of 225-350 °C, or 225-300 °C, or 250-500 °C, or 250-450 °C, or 250-400 °C, or 250-350 °C, or 250-300 °C, or 260-500 °C, or 260-450 °C, or 260-400 °C, or 260-350 °C. In particular, the contacting may be conducted at a temperature in the range of 180-280 °C, e.g., 180-260 °C, or 180-240 °C, or 180-220 °C, or 200-280 °C, or 200-260 °C, or 200-240 °C, or 220-280 °C, or 220-260 °C.

[0161] One of the main challenges of using CO2 in the feed stream of the FT process is to convert the CO2 to CO at economical and energy-efficient conditions. Conventional rWGS reactions used to activate CO2 often require high temperatures, leading to a more energy-intensive and expensive process. For example, temperatures in excess of 500°C are typical for rWGS reactors to ensure efficient conversion of CO2 to CO. In contrast, typical temperatures for FT conversion of CO and hydrogen are in the range of 200-350°C.

[0162] The FT processes described herein can be performed at temperatures that are lower than temperatures used in many conventional reverse water-gas shift processes. In particular, the present inventors have found that operating the FT stage at temperatures intermediate between those conventionally used for rWGS and FT can help to ensure suitable productivity and selectivity of C5+ hydrocarbons whilst also ensuring that the first product stream has a suitable ratio of hydrogen :carbon monoxide to permit efficient production of methanol in the methanol synthesis stage. More specifically, the present inventors have found that the multi-stage process of the present invention operates particularly efficiently when the temperature of the FT reaction zone is greater than 250°C, preferably greater than 300°C. The upper limit for the temperature may be, for example 350°C, 400°C or 500°C. Particularly good results are observed in the range of 250°C to 500°C, in particular 300°C to 500°C, especially 300°C to 400°C, most particularly 300-350°C. The present inventors have discovered, in particular, that the ratio of hydrogemcarbon monoxide output in the first product stream is particularly sensitive to the temperature of the FT reaction zone, and that the temperature preferred temperature ranges are particularly effective at minimising the ratio of hydrogen to carbon monoxide, whilst also allowing operation with lower energy demand, as well as for facile integration with a subsequent methanol synthesis process step. At lower temperatures, relatively longer chain hydrocarbon products can be formed. While there may be lower conversion of CO2 at lower temperatures, unreacted CO2 can be recycled, and the lower conversion can be acceptable in view of the desirability of longer-chain hydrocarbon products.

[0163] Pressures in the FT reaction zone

[0164] Additionally, the FT stage described herein can be performed at a variety of pressures, as would be appreciated by the person of ordinary skill in the art.

[0165] For example, the contacting of the FT feed stream with a FT catalyst is conducted at a pressure of at least 1 barg, e.g., at least 5 barg, or at least 10 barg. As is understood by the person skilled in the art, “barg” corresponds to the pressure of the system in bar relative to the atmospheric / ambient pressure outside of the system.

[0166] The contacting may be conducted at a pressure in the range of, for example, 1 to 100 barg. For example, the contacting is conducted at a 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.

[0167] The present inventors have identified that the use of a multi-stage process in the present invention means that the preferred pressure conditions for the FT reaction zone differ somewhat compared to the conditions which would be used for the FT reaction zone if it were used in a single stage process. In particular, the present inventors have discovered that using comparatively lower pressures leads to a ratio of hydrogemcarbon monoxide in the first product stream which is closer to the optimal ratio for methanol synthesis in the methanol synthesis zone, whilst ensuring suitable production of C5+ hydrocarbons in the first product stream. For this reason, the pressure is preferably 5 to 60 barg, more preferably 5 to 50 barg, more preferably still 10 to 40 barg, even more preferably still 10 to 30 barg.

[0168] GHSV in the FT reaction zone

[0169] The FT stage 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 FT stage in the FT reaction zone is not particularly limited. For example, the contacting of the FT feed stream with the FT catalyst may be conducted at a first catalyst FT GHSV up to 100,000 h-1, e.g., up to 75,000 IT1, or up to 50,000 h-1, with suitable ranges being 1,000 to 100,000 IT1, or 1,000 to 75,000 h-1, or 1,000 to 50,000 IT1, or 2,000 to 100,000 h1, or 2,000 to 75,000 h1, or 2,000 to 50,000 h1, or 5,000 to 100,000 h1, or 5,000 to 75,000 IT1, or 5,000 to 50,000 IT1. The contacting may be conducted at a first catalyst FT GHSV up to 4,000 IT1, e.g., up to 4,000 IT1, or up to 20,000 IT1, with suitable ranges being for example 1,000 to 40,000 IT1, or 1 ,000 to 30,000 IT1, or 1 ,000 to 20,000 IT1, or 2,000 to 40,000 h1, or 2,000 to 40,000 h1, or 2,000 to 30,000 h1, or 5,000 to 40,000 h1, or 5,000 to 30,000 h1, or 5,000 to 30,000 h1, or 10,000 to 40,000 h1, or 10,000 to 30,000 h1, or 10,000 to 20,000 h1.

[0170] The present inventors note that the CO selectivity and C5+ selectivity of the FT stage 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. For this reason, the present invention generally prefers GHSV values for the first FT stage of greater than 2,000 h-1, such as greater than 5,000 IT1.

[0171] Combined conditions in the FT reaction zone

[0172] As noted above, the present inventors have identified that the use of a multi-stage process in the present invention means that the preferred conditions for the FT reaction zone differ somewhat compared to the conditions which would be used for the FT reaction zone if it were used in a single stage process. They have identified that particularly good performance is achieved when one or more of the following conditions are satisfied:

[0173] i. a temperature of greater than 250°C;

[0174] ii. a pressure of 10 to 100 barg (e.g. 10 to 80 barg, or 10 to 40 barg);

[0175] ill. a GHSV of greater than 2,000 h-1; and

[0176] iv. a molar ratio of hydrogen to carbon dioxide of less than 4:1 , preferably less than 3:1, more preferably less than 2:1.

[0177] Preferably, both (I) and (ii) are satisfied, preferably all of (i), (ii) and (iii); (i), (ii) or (iv); and most preferably all of (i)-(iv) are satisfied.

[0178] Preferably, both (I) and (iv) are satisfied.

[0179] Preferably, both (ii) and (iv) are satisfied.

[0180] The skilled reader recognizes that the general options and preferred values for the temperature, pressure, GHSV and molar ratio of hydrogen to carbon dioxide apply in respect of the combined values above.

[0181] FT catalyst

[0182] Preferably, the FT catalyst includes at least 10 wt% iron (e.g., at least 15 wt%, at least 20 wt%, or at least 25 wt%), on an elemental basis. Preferably, the FT catalyst includes at least 30 wt% iron, e.g., at least 35 wt%, or at least 40 wt% iron, on an elemental basis. Advantageously, ironbased catalysts have both rWGS and FT activity.

[0183] Optionally, the FT catalyst is an alkali-promoted FT catalyst, preferably an alkali-promoted ironbased FT catalyst. For example, in some embodiments as described herein, the FT catalyst includes at least 1 wt% (e.g., at least 2 wt%, or at least 3 wt%) alkali metal, on an elemental basis. In some embodiments as described herein, the alkali metal is one or more of sodium, potassium, rubidium, and cesium.

[0184] Optionally, the FT catalyst is an iron-based catalyst further comprising copper, most preferably an alkali-promoted iron-based catalyst comprising copper.

[0185] The FT catalysts suitable for use in the process as described herein can be a variety of forms and are not particularly limited. For example, the FT catalyst may be a supported or unsupported catalyst.

[0186] Preferably, the FT catalyst is a supported catalyst, 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. Again, preferably the supported catalyst is an iron-based catalyst further comprising copper, most preferably an alkali-promoted iron-based catalyst comprising copper, with the support most preferably being aluminum oxide and / or silicon oxide

[0187] The person of ordinary skill in the art will appreciate that the FT catalysts 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 FT catalysts 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 FT catalyst.

[0188] However, the FT catalyst can itself be formed as a layer on an underlying substrate. The underlying substrate is not particularly limited. 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 FT catalyst for the particular reactor system.

[0189] Conventionally, catalyst materials such as iron-based catalysts are prepared for use as active catalysts by treating them in situ with a reducing gas such as hydrogen, under conditions sufficient to convert a substantial amount of the metal oxides of the calcined catalyst material to metal (e.g. iron oxide to metallic iron). Then, when exposed to Fischer-Tropsch reaction conditions, a substantial part of this metal 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 FT catalyst is activated by contact with H2and oxides of carbon (e.g., CO and CO2).

[0190] The carbiding can be performed in any convenient manner. For example, in various embodiments, the carbiding 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 in metallic form. Without intending to be bound by theory, the inventors understand this step to reduce oxidic metal species to metallic species, so that they can be more easily carbided in a subsequent treatment with a carbiding gas. Upon treatment of the iron-based catalyst with the reducing gas stream, a portion of the iron components present in the FT catalyst as described herein react to form metallic iron (Fe°). Optionally, the treatment with the reducing gas stream is performed in the substantial absence of carbon monoxide. For example, the reducing gas stream may comprise 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. The reducing gas stream may further comprise an inert gas, such as nitrogen. The hydrogen and inert gas may be present in the reducing gas stream in a ratio of at least 1:1.

[0191] Suitably, treating the FT catalyst material with the reducing gas stream is conducted at a temperature in the range of 250-650 °C. For example, treating the FT catalyst material with the reducing gas stream may be conducted at a temperature in the range of 250-600 °C, or 250-550 °C, or 250-500 °C, or at a temperature in the range of 300-650 °C, e.g., 300-600 °C, or 300-550 °C, or 300-500 °C, or 350-650 °C, e.g., 350-600 °C, or 350-550 °C, or 350-500 °C.

[0192] 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 metal of the catalyst material in metallic form (e.g. 50 atom% iron in metallic form). Treating the catalyst material with the reducing gas stream may be conducted for at least 12 hours, e.g., at least 14 hours. For example, treating the catalyst material with the reducing gas stream may be 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.

[0193] 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. The treatment with the reducing gas stream may be performed to provide a catalyst material in which at least 60 atom% of the metal (e.g. iron) is in reduced form, e.g., at least 70 atom%, at least 80 atom%, or at least 85 atom%. The proportion of metal in reduced form is measured by XRD.

[0194] The carbiding 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 metal of the catalyst material in carbided form. This can be performed, e.g., after a treatment with a reducing gas as described above.

[0195] Optionally, the reducing gas / carbiding gas comprises at least a portion of H2and CO (if present) from the FT feed stream. For example, the process may further comprise separating at least a portion of H2and at least a portion of CO of the FT feed stream and contacting it with the FT catalyst to activate the FT catalyst. In the process 200 shown schematically in FIG. 2, at least a portion of H2and CO stream 225A is separated from the FT feed stream 211 and contacted with the FT catalyst 213 to activate it. However, separate carbiding processes are not necessary, as the FT catalyst material can be carbided under the reaction conditions of the FT reaction zone, especially when treated first with a reducing gas as described above.

[0196] It can be desirable to have a substantial fraction of the metal of the carbided FT catalyst material in carbide form, as it is carbide forms that are of highest catalytic activity. For example, in the carbided FT catalyst materials, at least 50 atom% of the metal (e.g. iron) is in a carbide form, e.g., at least 55 atom%, or at least 60 atom. Optionally, 50-95 atom% of the metal (e.g. iron) is in a carbide form, e.g., in the range of 50-90%, or 50-85%, or 50-80%. The carbided FT catalyst materials have 55-95 atom% of the metal in a carbide form, e.g., in the range of 55-90%, or 55-85%, or 55-80%; for example, in the range of 60-95 atom% of the metal (e.g. iron) is in a carbide form, e.g., in the range of 60-90%, or 60-85%, or 60-80%. The amount of metal that is in the form of carbide is determined by Mbssbauer spectroscopy, and as such is expressed as an atomic fraction of metal in the form of carbide of the total metal species visible to Mbssbauer spectroscopy.

[0197] 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, the iron-based carbided Fischer-Tropsch catalyst materials of the disclosure may have at least 5 atom% of the iron 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, it can be desirable to limit the amount of oxidic iron in the carbided Fischer-Tropsch catalyst material. For example, in the carbided Fischer-Tropsch catalyst materials of the disclosure, in the range of 5-50 atom% of the iron may be in an oxide phase, e.g., 5-45 atom%, or 5-40 atom%; e.g. in the range of 10-50 atom% of the iron may be in an oxide phase, e.g., 10-45 atom%, or 10-40 atom%; e.g. in the range of 15-50 atom% of the iron is in an oxide phase, e.g., 15-45 atom%, or 15-40 atom%, e.g. 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 the art 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.

[0198] Optionally, at least 30 atom% of the oxidic iron of the carbided Fischer-Tropsch catalyst material is in the form of FesO4. The present inventors note that this partially-reduced oxide has especially good activity as a reverse water-gas shift catalyst. Preferably, at least 40 atom% of the oxidic iron of the carbided FT catalyst material is in the form of FesO4, e.g., at least 50 atom%. Optionally, at least 60 atom% of the oxidic iron of the carbided FT 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 Mossbauer spectroscopy.

[0199] Methanol synthesis feed stream

[0200] One of the advantages of using a FT catalyst with rWGS activity is that CO produced can not only undergo Fischer-Tropsch synthesis in the FT stage, it can also be passed to the downstream methanol synthesis zone.

[0201] As described above, the methanol synthesis feed stream comprises at least a portion of the carbon monoxide of the first product stream. For example, the methanol synthesis feed stream may comprise at least 50%, at least 60%, at least 70%, or at least 80%, of the carbon monoxide of the first product stream. Preferably, the methanol synthesis feed stream comprises substantially all of the carbon monoxide of the first product stream.

[0202] However, CO can be provided to the methanol synthesis feed stream from other sources. For example, CO may be provided to the second feed stream from a CO source other than the first product stream. In FIG. 4, a stream of CO 426a from some other source is included in the methanol synthesis feed stream 421. The person of ordinary skill in the art will appreciate that CO can be provided from a variety of sources, e.g., gasification, reforming, or electrochemical CO2 reduction. Preferably, any additional CO fed to the system is a biogenic source of CO. For example, the CO may be derived from biomass pyrolysis, which produces a hydrogen-deficient and CO-rich gas mixture which can be used to form the methanol synthesis feed stream, without needing to separate hydrogen from the mixture in advance. Moreover, as described in more detail below, CO can be recycled to the methanol synthesis feed stream from the second product stream. Optionally, CO fed to the methanol synthesis feed stream is derived only from the multi-stage reaction (e.g. from the first product stream or as a recyclate from the second product stream), instead of from an external source.

[0203] The first product stream comprises C5+ hydrocarbons and carbon monoxide. The first product stream may further comprise water. At least a portion of the first product stream (e.g., C5+ hydrocarbons, CO, and water) is provided to the methanol synthesis feed stream. For example, at least 50 mol%, e.g., at least 60 mol%, at least 70 mol%, or at least 80 mol%, or the first product stream may be provided to the methanol synthesis feed stream. Optionally, substantially all of the first product stream is provided to the methanol synthesis feed stream. As described above, the first product stream further comprises water. Optionally, at least a portion of the water present in the first product stream is provided to the methanol synthesis feed stream. For example, at least 50%, at least 60%, at least 70%, or at least 80% or the water present in the first product stream may be provided to the methanol synthesis feed stream. Optionally, substantially all of the water present in the first product stream is provided to the methanol synthesis feed stream. Alternatively, the process comprises separating the first product stream to provide a water-rich first product stream and a water-poor first product stream, wherein at least a portion (e.g., all of) the water-poor first product stream is provided to the methanol synthesis feed stream. An example of such a process is shown schematically in FIG. 2. In FIG. 2, the process 200 includes process for preparing hydrocarbons by providing a FT feed stream 211 comprising carbon dioxide and hydrogen, here, to a FT reaction zone, e.g., a reactor 210. A FT catalyst 213, as described herein, is contacted with the FT feed stream 211 under conditions sufficient to form a first product stream 212 comprising C5+ hydrocarbons and carbon monoxide. The first product stream 212 is then separated in a water separation zone 216 to provide a water rich first product stream 217A and a water- poor first product stream 217B, wherein at least a portion of (e.g., all of) the water-poor first product stream 217B is provided to the methanol synthesis feed stream 221. The person of ordinary skill in the art will appreciate that a variety of processes can be used to remove water from the first product stream. For example, the first product stream 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 first product stream; water can be recovered from the molecular sieves of the guard bed, e.g., by heating and vacuum. Alternatively, a knockout vessel can be used. However, use of a knockout vessel can in some cases cool the first product stream enough so that it is desirably reheated for introduction to the methanol synthesis process step. In FIG. 2, the process 200, FT reactor 210, FT feed stream 211, first product stream 212, FT catalyst 213, methanol synthesis reactor 220, methanol synthesis feed stream 221 , second product stream 222 and methanol synthesis catalyst 223 are generally as described herein.

[0204] Optionally, the portion of the first product stream that is included in the methanol synthesis feed stream has a water content of no more than 10 mol%, e.g., of no more than 2 mol%, of no more than 0.5 mol%.

[0205] As described above, the first product stream also includes C5+ hydrocarbons. As would be understood by the person of ordinary skill in the art, the C5+ hydrocarbons and any water present in the first product stream can be conveniently condensed. These substances can be separated from the first product stream via condensation. For example, the process may further comprise separating the first product stream to provide a condensate-rich first product stream enriched in water and C5+ hydrocarbons and a condensate-poor first product stream lean in water and C5+ hydrocarbons, wherein at least a portion of (e.g., all of) the condensate-poor first product stream is provided to the methanol synthesis feed stream. An example of such a process is shown schematically in FIG. 4. In FIG. 4, the process 400 includes a process for preparing hydrocarbons by providing a FT feed stream 411 comprising carbon dioxide and hydrogen, here, to a FT reaction zone, e.g., a reactor 410. A FT catalyst 413, as described herein, is contacted with the FT feed stream 411 under conditions sufficient to form a first product stream 412 comprising C5+ hydrocarbons and carbon monoxide. The first product stream 412 is then separated in a condensate separation zone 416 to provide a first product stream enriched in water and C5+ hydrocarbons 417A and a condensate-poor first product stream lean in water and C5+ hydrocarbons 417B, wherein at least a portion of (e.g., all of) the condensate-poor first product stream 417B is provided to the methanol synthesis feed stream 421.

[0206] The person of ordinary skill in the art would appreciate that, based on the processes as described herein, the first product stream may include H2, CO, and CO2and other components in various amounts. Components of the first product stream may be separated and used for various purposes in the integrated process.

[0207] For example, the process may further comprise separating the first product stream to recycle at least a portion (e.g., at least 5 mol%, at least 10 mol%, at least 25 mol%, at least 50 mol%, at least 75 mol%, or at least 90 mol%) of one or more components of the first product stream to the FT feed stream. For example, when the first product stream includes CO2, the process can include recycling at least a portion (e.g., at least 5 mol%, at least 10 mol%, at least 25 mol%, at least 50 mol%, at least 75 mol%, or at least 90 mol%) of the CO2 of the first product stream to the FT feed stream. The first product stream may also include H2; optionally, the process further includes recycling at least a portion of H2of the first product stream (e.g., at least 5 mol%, at least 10 mol%, at least 25 mol%, at least 50 mol%, at least 75 mol%, or at least 90 mol%) to the FT feed stream.

[0208] Such recycling is shown in the process 200 of FIG. 2. Here, the process 200 includes separating from the first product stream 212 at least a portion of CO2(stream 215) to recycle to the FT feed stream 211. Similarly, the process 200 includes separating from the first product stream 212 at least a portion of H2(stream 214) to recycle to the FT feed stream 211. While stream 215 is depicted as entering reactor 210 through a different inlet than the rest of the FT feed stream 211, it is considered to be part of the FT feed stream, as it is part of the material input to the process step.

[0209] Ratio of hydrogen to carbon monoxide in the methanol synthesis feed stream

[0210] The methanol synthesis feed stream includes both hydrogen and carbon monoxide, with at least a portion of the carbon monoxide derived from the first product stream.

[0211] Preferably, the hydrogen in the methanol synthesis feed stream is derived from the first product stream. For example, at least 25% of the H2of the first product stream, e.g., at least 50% of the H2, at least 75% of the H2, or at least 90% of the H2of the first product stream may be included in the methanol synthesis feed stream. Of course, some of the H2of the first product stream can be used for other purposes, e.g., catalyst activation as described herein. Optionally, substantially all of the H2of the methanol synthesis feed stream comes from the first product stream.

[0212] Optionally, more H2than necessary is provided for the FT reaction in the FT feed stream, to provide excess H2in the first product stream that can then provide a desired amount of H2to the methanol synthesis feed stream for the downstream methanol synthesis process step. In other embodiments, H2can be provided to the methanol synthesis feed stream from other sources. For example, H2may be provided to the methanol synthesis feed stream from a H2source other than the first product stream. In FIG. 4, a stream of H2426b from some other source is included in the methanol synthesis feed stream 421. The person of ordinary skill in the art will appreciate that H2can be provided from a variety of sources, e.g., gasification, reforming, or H2O electrolysis. Moreover, as described in more detail below, H2can be recycled to the downstream methanol synthesis feed stream from the second product stream.

[0213] Although it is desirable to carry forward a substantial portion, or all, of the hydrogen from the first product stream, the amount of hydrogen in the first product stream arising from unreacted hydrogen of the first product stream is generally present in a significantly higher molar amount than carbon monoxide and carbon dioxide. The present inventors have recognized that it is particularly advantageous to carry out the multi-stage reaction such that the ratio of hydrogen to carbon monoxide in the methanol synthesis zone is reduced compared to the hydrogen to carbon monoxide molar ratio in the first product stream.

[0214] The present inventors have recognized that it is especially advantageous for the methanol synthesis feed stream to have a molar ratio of hydrogen to carbon monoxide in the range of 0.5: 1 to 20: 1 , such as 0.5:1 to 10: 1 , preferably 0.5:1 to 8: 1 , more preferably 0.5:1 to 6: 1 , more preferably 1:1 to 5:1, e.g. in the range of 1:1 to 2.5:1. For example, the methanol synthesis feed stream may have a H2:CO ratio in the range of 0.5:1 to 6:1, 1:1 to 3:1, 1.4:1 to 3:1, or 1.4:1 to 2:1.

[0215] One option for arriving at a suitable ratio of hydrogen to carbon monoxide is to co-feed a Fldeficient syngas stream (e.g., H2:CO is in the range of 0.5:1 to 1.5:1) to the methanol synthesis feed stream such that the methanol synthesis feed stream ends up with a desirable H2:CO ratio (e.g., in the range of 1.5:1 to 3:1, or 1.5:1 to 2.5:1). This process is shown in process 400 of FIG. 4, wherein CO feed stream 426A and H2feed stream 426B can supply a H2-deficient syngas stream to methanol synthesis feed stream 421 to adjust the ratio of H2:CO.

[0216] However, as discussed above, to realise the maximum potential of using carbon dioxide and hydrogen as feedstocks, it is preferable to adjust the ratio of hydrogen to carbon monoxide without requiring the supplementation of the first product stream with an extraneous source of carbon monoxide. As discussed above, one method for achieving these ratios without the addition of extraneous CO is to control the conditions of the FT reaction. Additionally or alternatively, it is possible to achieve these ratios through adjustment of or addition to the first product stream when forming the methanol synthesis feed stream.

[0217] In some instances, the methanol synthesis catalyst shows activity for converting both carbon monoxide and carbon dioxide to methanol. The ideal hydrogen:CO2ratio for conversion of carbon dioxide is around 3:1. Thus, it is also preferable for the methanol synthesis feed stream to have a molar ratio of hydrogen to carbon dioxide in the range of 0.5:1 to 20: 1 , such as 0.5: 1 to 10:1, preferably 0.5:1 to 8:1, more preferably 0.5:1 to 6:1, more preferably 1:1 to 5:1, e.g. in the range of 1 : 1 to 2.5: 1. For example, the methanol synthesis feed stream may have a H2:CO2 ratio in the range of 0.5:1 to 6:1, 1:1 to 3:1, 1.4:1 to 3:1, or 2.4:1 to 3:1.

[0218] It is noted that where the methanol synthesis catalyst shows activity for converting both carbon monoxide and carbon dioxide to methanol, then reducing the level of hydrogen may shift the molar ratio of hydrogemcarbon dioxide below the ideal ratio of ~3:1. However, the present invention is particularly concerned with implementations which make efficient use of carbon dioxide as the feedstock for the FT reaction and seek to efficiently use the unreacted carbon monoxide from the first product stream, such that any recycle stream which is returned to the FT reaction zone from the second product stream has a high proportion of CO2 relative to CO. Thus, the present invention advantageously seeks to adjust the amount of hydrogen to levels better suited to the conversion of carbon monoxide than carbon dioxide.

[0219]

[0220] The molar ratio of hydrogen to carbon monoxide in the methanol synthesis feed stream may be adjusted by selectively removing hydrogen from the first product stream so as to produce a modified product stream having a decreased molar ratio of hydrogen to carbon monoxide, and using this modified product stream to form the methanol synthesis feed stream.

[0221] Selective removal of hydrogen may be achieved by separation methods. In other words, the method may involve subjecting the first product stream to a separation method to selectively remove hydrogen. This method can separate the first product stream into a hydrogen rich (or pure) stream and a hydrogen depleted stream, wherein the hydrogen depleted stream is used to form the methanol synthesis feed stream. Advantageously, the hydrogen rich (or pure) stream can be recycled to the FT reaction zone.

[0222] Separation of hydrogen from the first product stream may be carried out by any suitable method.

[0223] Optionally, separation of hydrogen is achieved using a hydrogen selective membrane, e.g. a hydrogen permeable membrane. This approach may be referred to as hydrogen skimming. Suitably, the hydrogen selective membrane is a hollow-fibre membrane, such as a PRISM® Hydrogen Membrane available from Air Products, Trexlertown, US; a HISELECT® membrane available from Linde GmbH, Pullack, Germany or an ALaS membrane availability from Air Liquide, Paris, France.

[0224] Optionally, separation is achieved by adsorption, for example through Pressure Swing Adsorption (“PSA”), Temperature Swing Adsorption (“TSA”) or the like. In a PSA unit, the vapours of the first product stream are fed at elevated temperature and pressure to a fixed bed of adsorbent, e.g. containing selective molecular sieves. Due to its low molecular weight and lack of polarity, hydrogen adsorbs more weakly to the adsorbent than the other components of the first product stream, creating a hydrogen-enriched stream. This hydrogen-enriched stream can then exit the PSA unit, and is preferably recycled to the FT feed stream. The pressure in the PSA unit is then reduced and the remaining components of the first product stream are desorbed to form a hydrogen-depleted stream, which is used to form the methanol synthesis feed stream.

[0225] In implementing such approaches, the method preferably involves providing a hydrogen separation zone between the FT reaction zone and methanol synthesis zone. The hydrogen separation zone may be a separate unit to carry out such separation. For example, a unit (e.g. cartridge) containing a hydrogen separation membrane may be positioned between the FT reaction zone and methanol synthesis zone. Alternatively, an adsorption unit, such as a PSA, unit may be positioned between the FT reaction zone and methanol synthesis zone.

[0226] Figure 7 depicts a multi-stage reactor system 700 of the invention in which hydrogen levels are adjusted in the first product stream using a hydrogen separation unit 740. In this system, a FT feed stream 711 containing carbon dioxide and hydrogen is fed to FT reactor 710 containing a catalyst bed 713, formed from an iron-based FT catalyst. A first product stream 712 exits the FT reactor 710, the product stream including the reaction products of rWGS and FT, together with unreacted components such as hydrogen and carbon dioxide. The ratio of hydrogen to carbon monoxide is above 2:1 - for the purposes of this illustration we will hypothesise a molar ratio of 10:1. The first product stream 712 is fed to a condenser 716A and subsequently to a gas-liquid separation unit 716B, which results in a water- and C5+ hydrocarbon-enriched stream 717A which is collected in vessel 716C, and a water- and C5+-depleted stream 717B. This stream 7171B is fed to hydrogen separation unit 740, which is a hydrogen permeable membrane (but could equally be a pressure swing adsorption unit). The hydrogen separating unit 740 outputs a hydrogen-enriched stream 741 and a hydrogen-depleted stream 721. The hydrogen-enriched stream 741 is recycled to FT feed stream 711. The hydrogen-depleted stream 721 has a ratio of hydrogemcarbon monoxide lower than first product stream 712 - for example, in the hypothetical situation above where the ratio is 10:1 for first product stream 712, the hydrogen-depleted stream 721 may have a molar ratio of 3:1. This hydrogen-depleted stream 721 is used as the feed stream for methanol synthesis reactor 720, comprising a catalyst bed 723, in this case formed by a copper oxide-zinc oxide catalyst. The product stream 722 from the reactor is then subjected to separation in an analogous way to the first product stream, using a condenser 726A, and a gas-liquid separation unit 726B which delivers water and methanol to a collection vessel 726C, and delivers a recyclate stream 732 back to the FT feed stream 711 via a recycle compressor / circulator 734. A purge line 733 can be operated in instances where it is desirable to pause or stop delivery of the recyclate stream 732.

[0227] The molar ratio of hydrogen to carbon monoxide may also be adjusted by selectively reacting hydrogen from the first product stream. This may be carried out in addition to, or instead of, the separation techniques above.

[0228] For example, hydrogen from the first product stream can be consumed through a hydrogenation reaction with a suitable reactant, without affecting the level of carbon monoxide, to reduce the molar ratio of hydrogen to carbon monoxide in the methanol synthesis zone. Examples of suitable reactants include, for example, compounds containing an unsaturated moiety, in particular unsaturated hydrocarbons. The reactant may be, for example, an olefin (in particular light olefins such as C2-C4 olefins) or an aromatic compound. Preferably the reactant is an olefin, especially a C2-C4 olefin, or a mixture of such olefins.

[0229] Selective reaction of hydrogen from the first product stream may occur prior to introduction of the methanol synthesis feed stream to the methanol synthesis zone - e.g., in a separate hydrogen reaction zone / unit / reactor. Preferably, however, reaction of hydrogen occurs within the methanol synthesis zone, since this avoids the need for a separate zone / unit / reactor.

[0230] Typically, reaction of hydrogen from the first product stream will be a catalysed reaction, e.g. a catalysed hydrogenation reaction. In instances where the reaction of hydrogen occurs within the methanol synthesis zone, the methanol synthesis catalyst may also serve as the hydrogenation catalyst for the additional reactant.

[0231] The reactant for reacting with hydrogen may be added to the first product stream or obtained from the first product stream. Preferably, the reactant for reacting with hydrogen is part of or obtained from the first product stream.

[0232] Preferably, the reactant is a C2-C4 olefin from the first product stream. With this in mind, it is preferred that unsaturated C2-C4 hydrocarbons constitute a relatively high proportion of the total C1-C4 hydrocarbons in the first product stream. For example, unsaturated hydrocarbons may account for at least 10 mol%, preferably at least 20 mol%, more preferably at least 30 mol%, e.g. at least 40 mol% of the total C1-C4 hydrocarbons in the first product stream, and said unsaturated hydrocarbons are included in the methanol synthesis feed stream.

[0233] Additionally or alternatively, C2-C4 olefins may be added to the methanol synthesis feed stream from an alternative source, such as from a steam cracker, a fluid catalytic cracker (FCC), or from an alcohol dehydration stream.

[0234] The C2-C4 olefin may comprise or consist of ethylene.

[0235] The molar ratio of hydrogen to C2-C4 olefins used in the hydrogenation reaction may be in the range of 2: 1 to 30: 1 , for example 2: 1 to 20: 1 , such as 5: 1 to 30: 1 or 5: 1 to 20: 1. For example, in instances where hydrogenation occurs in the methanol synthesis zone, the molar ratio of hydrogen to C2-C4 olefins in the methanol synthesis feed stream may be in the range of 2:1 to 30: 1 , for example 2: 1 to 20: 1.

[0236] Figure 8 depicts a multi-stage reactor system 800 of the invention in which C2-4 olefins are added to the output of the FT reactor in order to deplete hydrogen levels in the methanol synthesis reactor. In this system, a first feed stream 811 containing carbon dioxide and hydrogen is fed to a FT reactor 810 containing a catalyst bed 813, formed from an iron-based FT catalyst. A first product stream 812 exits the FT reactor 810, the product stream including the reaction products of rWGS and FT, together with unreacted components such as hydrogen and carbon dioxide. The ratio of hydrogen to carbon monoxide is above 2:1 - for the purposes of this illustration we will hypothesise a molar ratio of 10:1. The first product stream 812 is fed to a condenser 816A and subsequently to a gas-liquid separation unit 816B, which results in a water- and C5+ hydrocarbon-enriched stream 817A which is collected in vessel 816C, and a water- and C5+-depleted stream 817B. This stream 8171 B is combined with olefin stream 818 (in this case a stream of ethylene provided from a steam cracker, not shown) to form a methanol synthesis feed stream 821. The methanol synthesis feed stream 821 is fed to methanol synthesis reactor 820, comprising a catalyst bed 823, in this case formed by a copper oxide-zinc oxide catalyst. The copper oxide-zinc oxide catalyst also serves as a catalyst for hydrogenation of the ethylene, so as to deplete the level of hydrogen within the reactor, and thereby reduce the ratio of hydrogen: carbon monoxide within the reactor to 3:1 , away from the initial ratio of 10:1 for first product stream 812. The product stream 822 from the reactor is then subjected to separation in an analogous way to the first product stream, using a condenser 826A, and a gas-liquid separation unit 826B which delivers water and methanol to a collection vessel 826C, and delivers a recyclate stream 832 back to the first feed stream 811 via a recycle compressor / circulator 834. A purge line 833 can be operated in instances where it is desirable to pause or stop delivery of the recyclate stream 832.

[0237] Although the implementation shown in Figure 8 depicts the methanol synthesis reactor 820 with a single catalyst bed 823, the design or conditions of the system can be adjusted so as to promote hydrogenation of the olefins in a first (upstream) zone and to promote methanol synthesis in a second (downstream zone). For example, the methanol synthesis reactor 820 may have a change / gradient of conditions from upstream to downstream so as to favour hydrogenation of the olefin in an upstream zone and methanol synthesis in a downstream zone. This may be, for example, a temperature gradient, a switch or gradient of catalyst composition (e.g. varying level of mixing of different catalysts through the reactor bed), a pressure change or flow rate change (e.g. by varying reactor internal diameter). Alternatively, the single methanol synthesis reactor 820 can be replaced with a multi-stage reactor, e.g. comprising a hydrogenation reactor and a downstream methanol synthesis reactor. Although this discussion of the methanol synthesis reactor is described in relation to the embodiment shown in Figure 8, the skilled reader will appreciate that these features are general options which can be used across all of the embodiments described herein (e.g. regardless of catalyst type).

[0238] The system may incorporate a feedback loop, to dynamically adjust the system in response to a measured parameter, in particular in response to the hydrogemcarbon monoxide molar ratio detected in the first product stream. For example, the feedback loop may cause alteration of the amount of hydrogen removed from the first product stream, e.g. by adjusting conditions in a hydrogen membrane unit or PSA unit. In addition, or alternatively, the feedback loop may be used to adjust the flow rate of reactant which is to be subjected to hydrogenation, e.g. adjust the amount of C2-C4 olefin added to the methanol synthesis feed stream. Producing additional carbon monoxide from components of the first product stream and / or second product stream

[0239] The molar ratio of hydrogen to carbon monoxide in the methanol synthesis feed stream can be reduced relative to the ratio of hydrogen to carbon monoxide in the first product stream through supplementing carbon monoxide from the first product stream with additional carbon monoxide. Whilst such addition can be carried out using an extraneous source of carbon monoxide, it is preferred that a portion (e.g., at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, or at least 90%), preferably a substantial portion, optionally all of any carbon monoxide used to supplement the carbon monoxide content of the first product stream is derived from the multi-stage process itself. In particular, any carbon monoxide used to supplement the carbon monoxide content of the first product stream may be derived from additional components of the first product stream and / or from the second product stream.

[0240] To achieve this, it is preferred that the molar ratio of hydrogen to carbon monoxide in the methanol synthesis feed stream be adjusted by selectively reacting a component of the first product stream and / or second product stream to form additional carbon monoxide.

[0241] Preferably, the molar ratio of hydrogen to carbon monoxide in the methanol synthesis feed stream is adjusted by converting C1-C4 hydrocarbons of the first product stream to produce carbon monoxide, and including this carbon monoxide in the methanol synthesis feed stream. Conversion of the C1-C4 hydrocarbons may be carried out, for example, by reforming.

[0242] Reforming may be, for example, partial oxidation, steam reforming or dry CO2 reforming. The equations for these reactions are:

[0243]

[0244] From these formulae it can be seen that the ratio of carbon monoxide to hydrogen produced by the conversion increases with the number of carbon atoms in the hydrocarbon, and that higher levels can be produced by partial oxidation or dry CO2 reforming.

[0245] Figure 9 depicts a multi-stage reactor system 900 of the invention in which C1-C4 alkanes and C1-C4 alkenes output from the FT reactor are subjected to oxidation in order to generate further carbon monoxide, which is used to adjust the molar ratio of hydrogemcarbon monoxide. In this system, an FT feed stream 911 containing carbon dioxide and hydrogen is fed to a FT reactor 910 containing a catalyst bed 913, formed from an iron-based FT catalyst. A first product stream 912 exits the FT reactor 910, the product stream including the reaction products of rWGS and FT, together with unreacted components such as hydrogen and carbon dioxide. The ratio of hydrogen to carbon monoxide is above 2:1 - for the purposes of this illustration we will hypothesise a molar ratio of 10:1. The first product stream 912 is fed to a condenser 916A and subsequently to a gas-liquid separation unit 916B, which results in a water- and C5+ hydrocarbon-enriched stream 917A which is collected in vessel 916C, and a water- and C5+-depleted stream 917B. This stream 917B (which contains C1-C4 alkanes, C1-C4 alkenes, as well as oxygenates thereof, and contains CO, CO2 and hydrogen) is combined with oxygen stream 951 and fed to a partial oxidation unit 950. The partial oxidation unit 950 converts hydrocarbons from stream 917B into CO, CO2, hydrogen and water, and outputs these as pOx stream 952. Water is removed from pOx stream 952 using condenser 956A and gas-liquid separator 956B, to create a water-lean stream 921. The water-lean stream 921 has a molar ratio of hydrogemcarbon monoxide which is lower than that for product stream 912 - in this case, a molar ratio of 3:1. This water-lean stream 921 is used as the feed stream for methanol synthesis reactor 920, comprising a catalyst bed 923, in this case formed by a copper oxidezinc oxide catalyst. The product stream 922 from the reactor is then subjected to separation in an analogous way to the first product stream, using a condenser 926A, and a gas-liquid separation unit 926B which delivers water and methanol to a collection vessel 926C, and delivers a recyclate stream 932 back to the FT feed stream 911 via a recycle compressor / circulator 934. A purge line 933 can be operated in instances where it is desirable to pause or stop delivery of the recyclate stream 932.

[0246] Combination of approaches

[0247] Although the implementations shown in Figures 7-9 depict only a single intervention to adjust the hydrogemcarbon monoxide molar ratio of the first product stream, the skilled reader understands that each of these approaches can be used in combination. This may be required, for example, where the molar ratio of the first product stream is significantly above the molar ratio of 2:1 , and it is beneficial (e.g. for reasons of cost or space) to stepdown the ratio in multiple stages, through multiple methodologies. Alternatively or additionally, such an approach may be beneficial in terms of increasing lifetime or reducing energy consumption of the components of the reactor. Furthermore, certain steps can be applied multiple times - e.g. multiple separation steps using a hydrogen separation membrane may be utilised.

[0248] An example of such a combination is shown in Figure 10. In this case, FT feed stream 1011 is fed to a first reactor 1010 including catalyst bed 1013 - an iron-based catalyst in this instance. First product stream 1012 exiting the reactor then passes through a separator 1016 to remove a water- and C5+-enriched product stream 1017A, with the remainder of the product stream being fed to oxidation unit 1050, together with oxygen stream 1051. The output of oxidation unit 1050 is then fed to separator 1056, to remove a water-enriched stream 1057A, with the remainder of the stream then passing to hydrogen separation unit 1040 - in this case a hydrogen separation membrane unit. A hydrogen-enriched stream 1041 is returned to FT feed stream 1011, with a hydrogen-depleted stream 1021 passing to methanol synthesis reactor 1020 having a catalyst bed 1023 of a copper oxide-zinc oxide catalyst. The product stream 1022 is then separated to remove water and methanol, with the remainder of the product stream recycled to FT feed stream as recyclate stream 1032.

[0249] Further components of the methanol synthesis feed stream

[0250] It can be desirable to perform the methanol synthesis process step in the presence of CO2, in particular where the methanol synthesis catalyst has activity for converting CO2 to methanol. CO2 can come from the FT process, e.g., via the first product stream. Accordingly, the methanol synthesis feed stream includes at least a portion of CO2 of the first product stream. For example, at least 10% of the CO2 of the first 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 first product stream is included in the methanol synthesis feed stream. Accordingly, in various embodiments as otherwise described herein, the portion of the first product stream that is included in the methanol synthesis 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. Of course, alternatively, the methanol synthesis feed stream may not include any substantial amount of CO2 of the first product stream. While it can be desirable generally to recycle CO2 to the FT feed stream for use in the FT reaction, as described in more detail below, unreacted CO2 can be recycled from the second product stream to the FT feed stream.

[0251] It can additionally or alternatively be desirable to include further inert content to the methanol synthesis feed stream, such as nitrogen and methane. For example, one or more additional inerts (e.g., nitrogen and / or methane) may be provided to the methanol synthesis feed stream from a source other than the first product stream. For example, the methanol synthesis feed stream may include up to 80 mol% of one or more inerts (which for the purposes of calculation herein includes CO2), 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. Optionally, the methanol synthesis 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. Optionally, the methanol synthesis feed stream includes up to 80% of one or more inerts selected from CO2, 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%. Optionally, the methanol synthesis feed stream includes up to 80 mol% of CO2, 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%. In FIG. 4, a stream of inert(s) 426c from some other source is included in the methanol synthesis feed stream 421. 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 methanol synthesis feed stream from the second product stream.

[0252] It can be desirable to reduce the amount of water that is conducted to the methanol synthesis step. Accordingly, the portion of the first product stream that is included in the methanol synthesis feed stream may have 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 stability.

[0253] Preferably, the contacting of the methanol synthesis feed stream with the methanol synthesis catalyst in the methanol synthesis zone is conducted such that the overall multi-stage process has a methanol selectivity from CO2 input (i.e. , from CO2 input to the FT stage) of at least 5%, or at least 10%, e.g., at least 20%, or at least 30% (taking into account the products from both the first product stream and second product stream). Optionally, the contacting the methanol synthesis feed stream with the methanol synthesis catalyst in the methanol synthesis zone is conducted with a methanol selectivity of at least 75%, e.g., at least 80%, or at least 85%.

[0254] The second product stream preferably comprises at least 20 mol% methanol, preferably at least 30 mol% methanol, more preferably at least 40 mol% methanol.

[0255] Preferably, the methanol synthesis step is performed with high selectivity for methanol over other carbon products (i.e. with minimal formation of side-products including methane) - that is with high carbon product selectivity for methanol. When referring to “carbon product selectivity” of the decomposition process for a particular component, we mean the space time yield (STY) of the component as a percentage of the STY for all carbon-containing products from the methanol synthesis step. In this disclosure, STY is reported as the grammes of product produced per kilogramme of catalyst per hour (space time yield weight, or STYW), although those skilled in the art will recognise that the carbon product selectivity is a percentage which is independent of the particular units used for the STY.

[0256] Preferably, the methanol synthesis step is performed with a carbon product selectivity of at least 20% for methanol, e.g., at least 30%, at least 40%, at least 50%, at least 60% or at least 70% for methanol.

[0257] In contrast to the FT step, the level of C5+ hydrocarbons produced in the methanol synthesis step may be relatively low. For example, the second product stream may comprise no more than 10 mol% C5+ hydrocarbons, optionally no more than 5 mol% C5+ hydrocarbons, optionally less than 1 mol% C5+ hydrocarbons.

[0258] Conditions of the methanol synthesis zone

[0259] As described above, the process includes contacting a methanol synthesis feed stream with a methanol synthesis catalyst. The person of ordinary skill in the art will select appropriate reaction conditions (e.g., temperature and pressure) in conjunction with the particular feed and catalyst used to provide desired methanol production.

[0260] In some embodiments of the disclosure as described herein, the temperature of the methanol synthesis zone may be in the range of 150-400 °C. For example, the temperature may be in the range of 180-400 °C, or 180-350 °C, or 200-350°C, or 220-350°C, or 250-350 The present inventors note that the methanol synthesis feed stream may be lean in CO (I. e. , H2:CO is greater than 2:1), especially if the preceding FT process has low CO selectivity. In such situations, it can be advantageous to adjust the operating temperature of the methanol synthesis process to maximize the methanol selectivity of the process. For example, the temperature of the methanol synthesis zone may be in the range of 250-350 °C.

[0261] Notably, the FT temperature and the methanol synthesis temperature can be relatively close to one another. The present inventors have noted that the FT catalysts and processes described herein can provide suitable activity of CO2even at relatively low temperatures. Accordingly, the first product stream can be provided with a temperature that is suitable for, or at least close to suitable for, the methanol synthesis reaction step. This can desirably provide for increased process integration. For example, in various embodiments, the FT temperature is within 100 °C of the methanol synthesis zone temperature, e.g., within 50 °C of the methanol synthesis zone temperature, or within 25 °C of the methanol synthesis zone temperature.

[0262] The contacting the methanol synthesis feed stream with the downstream methanol synthesis catalyst may be conducted at a pressure of at least 1 barg, e.g., at least 5 barg, at least 10 barg, at least 20 barg, at least 50 barg or at least 100 barg. The upper limit on the pressure may be, for example, 200 barg. Optionally, the contacting is conducted at a pressure in the range of 1-200 barg, such as 1-150 barg. For example, the pressure may be in the range of IQ-200 barg, 20-200 barg, or 50-200 barg, or 10-180 barg, or 20-180 barg, or 50-180 barg or IQ-150 barg, or 20-150 barg, or 50-150 barg.

[0263] The methanol synthesis processes described herein can be performed at a variety of GHSV (gas hourly space velocity) values, as would be appreciated by the person of ordinary skill in the art. As such, the GHSV for contacting the methanol synthesis feed stream with the downstream methanol synthesis catalyst is not particularly limited. For example, the contacting may be conducted at a GHSV in the range of 1 ,000 to 2,000,000 h’1, such as in the range of 1 ,000 to 1,200,000 h1, or 1,000 to 500,000 h1, or 1,000 to 100,000 h1, or 5,000 to 1,200,000 h1, or 5,000 to 500,000 h1, or 5,000 to 100,000 h1, or 10,000 to 1,200,000 h1, or 10,000 to 500,000 tr1, or 10,000 to 100,000 h-1. Optionally, the contacting is conducted at a GHSV in the range of 1,000 to 50,000 h1, or 2,000 to 50,000 h1, or 5,000 to 50,000 h1, or 10,000 to 50,000, or 1,000 to 40,000 h1, or 2,000 to 40,000 h1, or 5,000 to 40,000 h1, or 10,000 to 40,000 h1, or 1 ,000 to 30,000 h1, or 2,000 to 30,000 h1, or 5,000 to 30,000 h1, or 10,000 to 30,000 h1. The person of ordinary skill in the art will appreciate that the full range of space velocities described above may not be available for a given methanol synthesis process.

[0264] Methanol

[0265]

[0266] The processes as described herein include contacting a methanol synthesis catalyst with the methanol synthesis feed stream as described herein.

[0267] The methanol synthesis catalyst is a catalyst suitable for conversion of carbon monoxide to methanol, ideally with a high mol% selectivity (e.g. more than 40%, more than 50% or more than 60%) for conversion of carbon monoxide to methanol. Preferably, the methanol synthesis catalyst is suitable for conversion of both carbon monoxide and carbon dioxide, ideally with a high mol% selectivity (e.g. more than 40%, more than 50% or more than 60%) for conversion of carbon monoxide and carbon dioxide to methanol. The FT catalyst is different from the methanol synthesis catalyst.

[0268] The methanol synthesis catalyst may comprise, for example, a transition metal, such as copper, zinc, molybdenum, tungsten, rhenium, platinum, palladium or zirconium , optionally alongside one or more co-catalysts.

[0269] The methanol synthesis catalyst may comprise, for example, copper. The catalyst may include, for example, at least 10 wt% copper, at least 20 wt% copper, or at least 30 wt% copper (as a percentage of the total weight of the methanol decomposition catalyst). The copper-based catalyst may include one or more co-catalysts or promoters. The amount of co-catalyst may be, for example, at least 40 wt%, at least 50 wt% or at least 60% (as a percentage of the total weight of the methanol decomposition catalyst). The co-catalyst preferably comprises or consists of zinc, magnesium or aluminium, preferably zinc.

[0270] For example, the methanol synthesis catalyst may include copper and zinc, optionally copper, zinc and one or both of magnesium and alumina. For example, the methanol synthesis catalyst may be a copper oxide-zinc oxide catalyst provided on a suitable support, such as alumina or chromia. Such catalysts are available commercially for methanol synthesis, for example, T-2130 available from Slid Chemie (having the composition: 33 wt% CuO and 66 wt% ZnO) or Katalko 51 available from Johnson Matthey (having the composition 64% CuO, 24% ZnO, 10% AI2O3and 2% MgO).

[0271] Alternatively or additionally, the methanol synthesis catalyst may comprise molybdenum, for example, it may be a molybdenum sulphide-based catalyst. Advantageously, such catalysts can achieve conversion of both carbon monoxide and carbon dioxide at high methanol selectivities.

[0272] Molybdenum sulphide based catalysts are preferred; these can be modified by a promoter. Promoter(s) can be added as salts during the catalyst preparation, and are preferably potassium ions (e.g. derived from a salt of potassium, such as potassium carbonate or acetate). The preferred loadings of potassium ions per molybdenum is comprised between 0.7 and 1.5, most preferably between 1.0 and 1.4.

[0273] The molybdenum sulphide based catalysts may contain cobalt, the cobalt to molybdenum molar ratio being preferably comprised between 0.5 and 3.0, more preferably between 0.5 and 1.0 and most preferably between 0.5 and 0.9.

[0274] The methanol synthesis catalysts suitable for use in the process as described herein can be a variety of forms and are not particularly limited. For example, the methanol synthesis catalyst may be a supported or unsupported catalyst. While the form of the catalyst is not particularly limited, the methanol synthesis catalyst may be a supported catalyst, wherein the support comprises at least one of titanium oxide, zirconium oxide, cerium oxide, aluminum oxide, silicon oxide and zinc oxide. For example, the support may comprise at least one or titanium oxide, aluminum oxide, and silicon oxide. Optionally, the support is a titanium dioxide support.

[0275] The person of ordinary skill in the art will appreciate that the methanol synthesis catalysts 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 methanol synthesis catalysts 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 methanol synthesis catalyst. Alternatively, the methanol synthesis catalyst of the disclosure can itself be formed as a layer on an underlying substrate. The underlying substrate is not particularly limited. 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 a methanol synthesis catalyst for the particular reactor system.

[0276] Methanol synthesis catalysts are typically activated before use, to provide the catalyst in metal(O) form. Such activation can be performed prior to contacting the methanol synthesis catalyst with the methanol synthesis feed stream.

[0277] For example, the methanol synthesis catalyst may be activated by contact with a reducing gas. For example, hydrogen can be an especially suitable gas for activating the methanol synthesis catalyst, e.g., when the activation is a reduction to metal(O) species. The reducing gas may comprise at least a portion of hydrogen from the first product stream. For example, the process may further comprise separating at least a portion of hydrogen of the first product stream and contacting it with the methanol synthesis catalyst to activate the catalyst. In the process 200 shown schematically in FIG. 2, at least a portion of hydrogen stream 225B is separated from the first product stream 212 and contacted with the methanol synthesis catalyst 223 to activate it. In other embodiments, H2present in the methanol synthesis feed stream can be used to activate the catalyst. This process is shown schematically in FIG. 4, where at least a portion of hydrogen stream 425 is separated from the methanol synthesis feed stream 421 and contacted with the methanol synthesis catalyst 423 to activate it. As would be understood by the person of ordinary skill in the art, activation temperatures can vary depending on the catalyst used. As such, the person of ordinary skill in the art would be able to select an appropriate temperature for activating the catalyst, e.g., in the range of 200-400 °C.

[0278] Second product stream

[0279] Additional components may be in present in the second product stream. For example, the second product stream may include water. Also present can be one or more light hydrocarbons (i.e. , C1-C4) as a side product. CO and / or H2can be present, e.g., unreacted from the methanol synthesis feed stream. CO2or other inerts as described herein can also be present. Such components of the second product stream can be separated and / or recycled in various manners.

[0280] As described above, the product stream also comprises light hydrocarbons, i.e., C1-C4 hydrocarbons and the product stream may be further separated to provide a light hydrocarbon product stream. Light hydrocarbons, while often not a desired portion of a methanol synthesis process, can themselves be useful for a number of purposes. Accordingly, the process may further include separating at least a portion of C1-C4 hydrocarbons from the 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 from the product stream 336 are separated to provide a light hydrocarbon stream 338. The light hydrocarbon stream can, for example, be recycled to the FT feed stream or the methanol synthesis feed stream. In the process 300 of FIG. 3, light hydrocarbons can be provided as part of the recycle stream 336, which becomes part of the FT feed stream 311. In the process 400 of FIG. 4, light hydrocarbons are recycled via recycle stream 436 to methanol synthesis feed stream 421.

[0281] The other components of the product stream, e.g., hydrogen, carbon monoxide, and carbon dioxide may be used in other feeds of the process as described herein. As such, at least a portion of hydrogen, carbon monoxide and carbon dioxide of the product stream may be included in the FT feed stream and / or the methanol synthesis feed stream. For example, it can be desirable to recycle hydrogen from the product stream, for example, to the FT feed stream. For example, in the process of FIG. 3, at least a portion of H2of the light product stream (e.g., at least 25%, at least 50%, or at least 75%) can be recycled to the FT feed stream 311 via recycle stream 336. Optionally, the process includes recycling at least a portion of H2of the product stream to the methanol synthesis feed stream. For example, in the process of FIG. 4, at least a portion of H2of the product stream (e.g., at least 25%, at least 50%, or at least 75%) can be recycled to the methanol synthesis feed stream 421 via recycle stream 436. As an example, at least 25%, e.g., at least 50% of H2of the product stream is recycled to the FT feed stream or the methanol synthesis feed stream. Optionally, at least 75%, e.g., at least 90% of H2of the product stream is recycled to the FT feed stream or the methanol synthesis feed stream.

[0282] In some cases, e.g., when H2is provided to the methanol synthesis feed stream from an H2source other than the first product stream, H2from the product stream can make up most of the H2of the FT feed stream, e.g., at least 90%, at least 95%, or at least 98% of the H2of the FT feed stream. This is shown, e.g., in FIG. 5. Here, the primary H2input to the process is through stream 540, which becomes part of the methanol synthesis feed stream 521. H2of the product stream is included in recycle stream 536, which becomes part of FT feed stream 511.

[0283] Similarly, it can be desirable to recycle CO of the product stream, for example, to the FT feed stream and / or the methanol synthesis feed stream. For example, it can be desirable to recycle carbon monoxide from the product stream, for example, to the FT feed stream. For example, in the process of FIG. 3, at least a portion of carbon monoxide of the product stream (e.g., at least 25%, at least 50%, or at least 75%) can be recycled to the FT feed stream 311 via recycle stream 336. Optionally, the process includes recycling at least a portion of carbon monoxide of the product stream to the methanol synthesis feed stream. For example, in the process of FIG.

[0284] 4, at least a portion of carbon monoxide of the product stream (e.g., at least 25%, at least 50%, or at least 75%) can be recycled to the methanol synthesis feed stream 421 via recycle stream 436. As an example, at least 25%, e.g., at least 50% of carbon monoxide of the product stream is recycled to the FT feed stream or the methanol synthesis feed stream. Optionally, at least 75%, e.g., at least 90% of carbon monoxide of the product stream is recycled to the FT feed stream or the methanol synthesis feed stream.

[0285] As with hydrogen and carbon monoxide, it can be desirable to recycle carbon dioxide of the product stream, for example, to the FT feed stream and / or the methanol synthesis feed stream. Since CO2is the primary carbon source for the FT step, it can be especially desirable to recycle CO2to the FT feed stream. Accordingly, the process may include recycling at least a portion (e.g., at least 50%, at least 75%, or at least 90%) of CO2of the second product stream to the FT feed stream. For example, in the process of FIG. 3, at least a portion of CO2of the second product stream (e.g., at least 50%, at least 75%, or at least 90%) can be recycled to the FT feed stream 311 via recycle stream 336. For example, it can be desirable to recycle carbon dioxide from the product stream, for example, to the FT feed stream. For example, in the process of FIG. 3, at least a portion of carbon dioxide of the product stream (e.g., at least 25%, at least 50%, or at least 75%) can be recycled to the FT feed stream 311 via recycle stream 336.

[0286] Optionally, the process includes recycling at least a portion of carbon dioxide of the product stream to the methanol synthesis feed stream. For example, in the process of FIG. 4, at least a portion of carbon dioxide of the product stream (e.g., at least 25%, at least 50%, or at least 75%) can be recycled to the methanol synthesis feed stream 421 via recycle stream 436.

[0287] Optionally, at least 25%, e.g., at least 50% of carbon dioxide of the product stream is recycled to the FT feed stream or the methanol synthesis feed stream. Optionally, at least 75%, e.g., at least 90% of carbon dioxide of the product stream is recycled to the FT feed stream or the methanol synthesis feed stream. In some cases, e.g., when CO2is provided to the methanol synthesis feed stream from a CO2source other than the first product stream, CO2from the second product stream can make up most of the CO2of the FT feed stream, e.g., at least 90%, at least 95%, or at least 98% of the CO2of the FT 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 methanol synthesis feed stream 621. CO2 of the second product stream is included in recycle stream 636, which becomes part of FT feed stream 611.

[0288] In many cases, hydrogen, carbon monoxide, and carbon dioxide, of the product stream will be recycled.

[0289] Moreover, when one or more inerts are used in the process steps, it can be desirable to recycle these. For example, the process may include recycling at least a portion of inerts of the second product stream to the FT feed stream and / or the methanol synthesis feed stream. Optionally, the process includes recycling at least a portion of inerts of the second product stream to the FT feed stream. For example, in the process of FIG. 3, at least a portion of inerts of the second product stream (e.g., at least 25%, at least 50%, or at least 75%) can be recycled to the FT feed stream 311 via recycle stream 336. Optionally, the process includes recycling at least a portion of inerts of the second product stream to the methanol synthesis feed stream. For example, in the process of FIG. 4, at least a portion of inerts of the second product stream (e.g., at least 25%, at least 50%, or at least 75%) can be recycled to the methanol synthesis feed stream 421 via recycle stream 436. Optionally, at least 25%, e.g., at least 50% of inerts of the second product stream is recycled to the FT feed stream or the methanol synthesis feed stream. For example, at least 75%, e.g., at least 90% of inerts of the second product stream may be recycled to the FT feed stream or the methanol synthesis feed stream. Optionally, a purge stream can be incorporated with the recycle stream to prevent uncontrolled accumulation of inerts in the recycle stream (not shown here).

[0290] As would be understood by the person of skill in the art, the second product stream will also include water. Optionally, the process further comprises separating at least a portion of water from the second product stream. This is shown schematically in FIG. 3. In the embodiment of FIG. 3, the FT catalyst 313 and the methanol synthesis catalyst 323 are provided in separate beds in the same reactor. Thus, the FT reaction zone 310 is a volume of the reactor 305 that includes the bed 314 containing the FT catalyst 313, and the methanol synthesis zone 320 is a volume of the reactor 305 that includes the bed 324 containing the methanol synthesis catalyst 323. FT feed stream 311 is contacted with the FT catalyst 313 to provide first product stream 312, which is passed directly as the methanol synthesis feed stream 321 to the methanol synthesis catalyst 323 to provide second product stream 322. Here, the process also optionally includes separating at least a portion of water (e.g., at least 50%, at least 75%, or at least 90%) from the second product stream 322 to provide water-containing stream 334.

[0291] The carbon dioxide of the product stream can also be used as a source of carbon monoxide for the process described herein. For example, the process may further include reacting at least a portion of the carbon dioxide of the product stream in a CO generating zone to convert carbon dioxide to carbon monoxide, and including a least a portion of the carbon monoxide from the CO generating zone in the FT feed stream and / or the methanol synthesis feed stream. The conversion method of carbon dioxide to carbon monoxide is not particularly limited. For example, a reverse water-gas shift or a conversion by a solid oxide electrochemical cell can be used. For example, in the process 500 of FIG. 5, at least a portion of the carbon dioxide of the product stream 536 is provided to a CO generating zone 562 to convert carbon dioxide to carbon monoxide, and at least a portion of the carbon monoxide from the CO generating zone 554 is provided to the FT feed stream 511 and / or the methanol synthesis feed stream 521. In FIG. 5, the process 500, FT reactor 510, FT feed stream 511, second product stream 512, FT catalyst 513, methanol synthesis reactor 520, methanol synthesis feed stream 521, second product stream 522 and methanol synthesis catalyst 523 are generally as described above. As described above, the product stream may also include light hydrocarbons that may be recycled to the first and / or methanol synthesis feed stream. There are other uses for the light hydrocarbon stream. For example, the process may further comprise at least partially oxidizing at least a portion of the C1-C4 hydrocarbons of the 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 methanol synthesis feed stream. An example of such a process is shown schematically in FIG. 6, in which the process 600, the FT feed stream 611 , the first product stream 612, the FT catalyst 613, the methanol synthesis feed stream 621, the second product stream 622 and the methanol synthesis catalyst 623 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 694a stream in the methanol synthesis feed stream 621.

[0292] Similarly, the process may further include oxidizing at least a portion of C1-C4 hydrocarbons of the light product stream in an oxidation reaction zone to provide an oxidation (OX) product stream comprising carbon dioxide, and including at least a portion of the carbon dioxide of the oxidation product stream to the FT feed stream. An example of such a process is shown in FIG.

[0293] 6, where the process 600 includes oxidizing at least a portion of the light hydrocarbon stream 638 in a partial oxidation reaction zone 692 to provide a CO2 containing OX stream, and including at least a portion of the OX stream 694b stream in the FT feed stream 611.

[0294] 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.

[0295] 5, a portion of light hydrocarbon stream 538 is burned in a power generation zone (here, in an electrical generator 570), to generate electricity stream 572. Optionally, the heat energy may be used to provide the needed heat duty for the FT 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 FT feed stream 511. The present inventors have noted that it can be desirable to provide for heat exchange with a relatively hot FT feed stream to cool the first product stream to a temperature more appropriate for the methanol synthesis step and to provide heat elsewhere to the integrated process. For example, the process may further comprise exchanging heat between at least a portion of the first product stream and at least a portion of the FT feed stream, thereby cooling at least a portion of the first product stream and heating at least a portion of the FT feed stream. An example of such a process is shown schematically in FIG. 4. In FIG. 4, the process 400, FT reactor 410, FT feed stream 411, first product stream 412, FT catalyst 413, methanol synthesis reactor 420, methanol synthesis feed stream 421 , second product stream 422 and methanol synthesis catalyst 423 are generally as described above. Here, the process 400 includes exchanging heat between at least a portion of the first product stream 412 and a least a portion of the first feed stream 411 In a first heat exchange zone 430, thereby cooling at least a portion of the first product stream 412 and heating at least a portion of the first feed stream 411. The person of ordinary skill in the art will appreciate that a wide variety of heat exchangers can be used for this purpose.

[0296] Of course, any excess heat in the first product stream can be additionally or alternatively used for other purposes. For example, the process may further comprise 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. 4. Here, after heat exchange with the FT feed stream 411 , the first product stream 412 is conducted to steam generation zone 432, to cool the first product stream 412 and provide heat to the steam generation zone 432. Steam can be generated from the heat provided, and electricity can be generated from the steam. For example, in the embodiment of FIG. 4, electricity stream 464 is provided by the generation of electricity using steam generated in the steam generation zone 432. 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. Optionally, the steam may be used to heat the FT feed stream. For example, in the embodiment of FIG. 4, the steam stream 466 generated in the steam generation zone 432 is conducted to the heat exchange zone 490 to heat the FT feed stream 411.

[0297] As with the first product stream, heat can be exchanged from the second product stream to provide heat to, for example, a feed stream (e.g., the first FT or methanol synthesis feed streams as described herein) or a steam generation zone. For example, in various embodiments, the process further comprises exchanging heat between at least a portion of the second product stream and at least a portion of the FT feed stream, thereby cooling at least a portion of the second product stream and heating at least a portion of the FT feed stream. In process 300 of FIG. 3, heat is exchanged between at least a portion of the second product stream 322 and FT feed stream 311 in a heat exchange zone 330, thereby cooling the second product stream 322 and heating the FT feed stream 311. Of course, heat can also be exchanged from the second product stream to the methanol synthesis feed stream. For example, the process may further comprise exchanging heat between at least a portion of the second product stream and at least a portion of the methanol synthesis feed stream, thereby cooling at least a portion of the second product stream and heating at least a portion of the methanol synthesis feed stream. In process 500 of FIG. 5, heat is exchanged between at least a portion of the second product stream 522 and methanol synthesis feed stream 521 in a heat exchange zone 530, thereby cooling the second product stream 522 and heating the methanol synthesis feed stream 521. Similarly, in process 600 of FIG. 6, heat is exchanged between at least a portion of the second product stream 622 and methanol synthesis feed stream 621 in a heat exchange zone 630, thereby cooling the second product stream 622 and heating the methanol synthesis feed stream 621. The person of ordinary skill in the art will appreciate that a wide variety of heat exchangers can be used for this purpose.

[0298] Of course, any excess heat in the second product stream can be additionally or alternatively used for other purposes. For example, the process may further comprise exchanging heat between at least a portion of the second product stream and a steam generation zone, thereby cooling at least a portion of the second product stream and providing heat to the steam generation zone. This is shown in FIG. 3. Here, after heat exchange with the FT feed stream 311 , the second product stream 322 is conducted to steam generation zone 332, to cool the second product stream 322 and provide heat to the steam generation zone 332. Steam can be generated from the heat provided, and electricity can be generated from the steam (not shown here).

[0299] As noted above, the FT process step provides a product stream that includes C5+ hydrocarbons (e.g., unsubstituted hydrocarbons like alkanes and alkenes, and / or oxygenated hydrocarbons such as alcohols). Accordingly, one or more products are provided from at least a portion of C5+ hydrocarbons of the first product stream. 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.

[0300] 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, the process may further include hydroprocessing at least a portion of C5+ hydrocarbons of the first product stream. 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. A wide variety of hydroprocessing techniques are known and the person of ordinary skill in the art will apply them here.

[0301] The processes described herein can be operated in a wide variety of reactor systems.

[0302] Suitable, the FT reaction zone (i.e., in which the FT process step is performed) comprises a FT reactor in which a FT catalyst is disposed, and the methanol synthesis zone (i.e., in which the methanol synthesis process step is performed) comprises a methanol synthesis reactor in which the methanol synthesis catalyst is disposed. Examples of such processes are shown schematically in FIGS. 1, 2, 4, 5, and 6. In these examples, the process (100, 200, 400, 500, 600) is performed in a reactor system that includes a FT reactor (110, 210, 410, 510, 610) in which the FT catalyst (113, 213, 413, 513, 613) is disposed, and a methanol synthesis reactor (120, 220, 420, 520, 620) in which the methanol synthesis catalyst (123, 223, 423, 523, 623) is disposed. 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.

[0303] But other embodiments are possible. For example, the process may be performed in a reactor system comprising FT catalyst bed in which the FT catalyst is disposed, and wherein the methanol synthesis zone comprises a methanol synthesis catalyst bed in which the methanol synthesis catalyst is disposed. Optionally, the FT reactor bed and the methanol synthesis reactor bed are disposed within the same reactor. Such a configuration is shown in FIG. 3, in which the FT catalyst 313 is disposed in a FT catalyst bed 314, and the methanol synthesis catalyst 323 is disposed in a methanol synthesis catalyst bed 324. Here, the catalyst beds 314 and 324 are in the same reactor, with process gases flowing between them. Such a configuration can be especially desirable when the temperatures used for the two zones are relatively close to one another. However, such a configuration is not particularly limited, as the person of ordinary skill in the art can implement more cooling or less heat input in the methanol synthesis section to accommodate processes where there is a relatively large difference in temperature between the FT and methanol synthesis processes.

[0304] Optionally, the process is performed in a reactor system comprising one or more FT catalyst containers in which the FT catalyst is disposed, and wherein the methanol synthesis zone comprises one or more methanol synthesis catalyst containers in which the methanol synthesis catalyst is disposed. These can be provided in the same reactor, such as described above with respect to catalyst beds.

[0305] As noted above, the FT process step using the FT catalysts described herein and the methanol synthesis process step can be performed under similar conditions.

[0306] In the embodiments particularly-described above, separate FT and methanol synthesis catalysts are used, e.g., in separate reactors, or in separate regions of the same reactor.

[0307] As described above, CO2 and H2are substantial inputs to the process as described herein. Advantageously, the present inventors have recognized that each of these can come from renewable sources.

[0308] 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 of lower carbon intensity. Accordingly, at least a part of the CO2of the FT feed stream and / or the methanol synthesis feed stream is preferably from a renewable source. Optionally, at least part (e.g., at least 25%, at least 50%, or at least 75%) of the CO2of the FT feed stream and / or the methanol synthesis feed stream is from direct air capture. For example, at least part (e.g., at least 25%, at least 50%, or at least 75%) of the CO2 of the FT feed stream and / or the methanol synthesis feed stream may be from a manufacturing plant such as a bioethanol plant (e.g., CO2 produced fermentation), a steel plant, or a cement plant. Accordingly, the rWGS-Fischer Tropsch integrated processes of the disclosure as described herein can, in some cases, be a net consumer of carbon dioxide. These benefits in particular make the integrated processes highly attractive for transportation fuels, for both automotive and aviation sectors, since the carbon monoxide produced by the rWGS activity of the FT catalyst can be readily utilized by well-established technologies to synthesize liquid hydrocarbon fuels.

[0309] In some embodiments, at least a part of the H2of the FT feed stream and / or the methanol synthesis feed stream is from a renewable source. For example, at least part (e.g., at least 25%, at least 50%, or at least 75%) of the H2of the FT feed stream and / or the methanol synthesis feed stream 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).

[0310] Optionally, at least part (e.g., at least 25%, at least 50%, or at least 75%) of the H2of the FT feed stream and / or the methanol synthesis feed stream may be from a so-called “blue” source, e.g., from a natural gas reforming process with carbon capture. Of course, other sources of H2can be used in part or in full. For example, optionally, at least part (e.g., at least 25%, at least 50%, or at least 75%) of the H2of the FT feed stream and / or the methanol synthesis feed stream is grey hydrogen, black hydrogen, brown hydrogen, pink hydrogen, turquoise hydrogen, yellow hydrogen, and / or white hydrogen.

[0311] The present inventors have noted that electrolysis of water is a desirable way to provide hydrogen to the claimed processes. Accordingly, optionally, the process includes providing at least a portion of H2to the FT feed stream and / or the methanol synthesis feed stream by electrolysis of water. Optionally, 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 second 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 400 of FIG. 4, water 418 separated from the first product stream is electrolyzed in electrolyzer 460, using electricity 464 generated from steam made in the steam generation zone 432 by heat exchange from the first product stream. H2generated in the electrolysis is provided via stream 465 to the FT feed stream. Optionally, at least a portion of O2 generated in the electrolysis 463 is provided to a partial oxidation reaction zone as described herein.

[0312] *** The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0313] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[0314] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[0315] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0316] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example + / - 10%.

[0317] EXAMPLES

[0318] Example 1 - effect of conditions on hydrogen :carbon monoxide ratio

[0319] A number of experiments were carried out to demonstrate the effect of reactor conditions on the ratio of hydrogen to carbon monoxide in the product stream of a modified FT process according to the FT step of the present invention.

[0320] Catalyst testing was performed using a 4-fold parallel fixed bed reactor unit (Manufactured by ILS) with tube internal diameter of 6.5mm and independent temperature and gas feed flow control per reactor. Catalyst was diluted with SIC for better temperature distribution along the bed and to avoid hot spots. The unit had two product knockout pots, firstly a hot pot (at 180°C collecting high boiling waxes) and a cold pot (at 12°C collecting water and light organics). GC analysis was done by analysing the 4 feed composition inlets and 4 product exits after knockout pots using an Agilent Refinery Gas Analyser. The GC had two TCD channels, one for hydrogen and the other for permanent gases (CH4, CO2, argon, nitrogen and CO). The other channel was an FID which is for light organics (C1-C5).

[0321] At the start of each test, the catalyst was reduced with H2(GHSV = 5000, 80% H2 / 20% Argon) at 400°C for ~24 Hrs. Then, the reactor was cooled to ~150°C, the gas was switched to the H2 / CO2 feed, the pressure was increased and subsequently the temperature of the reactor was increased to the desired reaction temperature. Experimental conditions and results are as summarised in Table 1.

[0322] Table 1

[0323]

[0324]

[0325] The data show that the molar ratio of hydrogemcarbon monoxide is particular sensitive to the ratio of hydrogen :carbon dioxide in the feed stream. This is especially clear from Figure 11 , which is a scatter plot for all experiments showing that the lowest molar ratio of hydrogemcarbon monoxide in the product stream is achieved at lower molar ratios of hydrogemcarbon dioxide in the feed stream. Clear bands are observed as the feed ratio moves up from 1 to 2, 2 to 2.5 and 2.5 to 3. This same trend is also evident in Figure 12, which compares experiments which differ only in terms of feed ratio, specifically, Experiments 15 and 16 (triangular data markers), and Experiments 17 and 18 (circular data markers).

[0326] The data also show that the molar ratio of hydrogemcarbon monoxide is highly sensitive to the temperature of the reactor. This is shown clearly in Figure 13, which provides a comparison of the results of experiments in the table above which differ only in terms of temperature - that is, Experiments 1 and 2 (triangular data markers), Experiments 3 and 4 (circular data markers), Experiments 5 and 6 (circular data markers) and Experiments 7-10 (diamond data markers). The data also show that increasing flow rate leads to a lower ratio of hydrogemcarbon monoxide when all other conditions are held equal, as shown in Figure 14, which compares the results of Experiments 5, 13 and 14. Likewise, increasing pressure led to a lower ratio of hydrogemcarbon monoxide when all other conditions were held equal, as shown in Figure 15, which compares the results of Experiments 2 and 15. However, the data suggest that the molar ratio of hydrogen :carbon monoxide is relatively less sensitive to pressure and flow rate changes as compared to alterations in feed ratio and temperature.

[0327] Example 2 - Partial oxidation of first product stream

[0328] The effect of partial oxidation on the first product stream was simulated, specifically the effect on the ratio of hydrogen :carbon monoxide. Partial oxidation was applied to the FT offgas and recycle purge of an FT reactor using a partial oxidation unit operating at a pressure of 40 bar and temperature of 1350°C, with the results as shown in Table 2.

[0329] Table 2

[0330]

[0331]

[0332] These data show that the output stream is enriched in both hydrogen and carbon monoxide, with the hydrogen to carbon monoxide ratio being reduced compared to the input stream.

Claims

52CLAIMS:

1. A process for preparing hydrocarbons and methanol, comprising:providing a Fischer-Tropsch (FT) feed stream comprising carbon dioxide and hydrogen wherein the molar ratio of hydrogen to carbon dioxide in the FT feed stream is no more than 20:1;in an FT reaction zone, contacting the FT feed stream with an FT catalyst comprising iron under conditions sufficient to form a first product stream comprising C5+ hydrocarbons and carbon monoxide;providing a methanol synthesis feed stream comprising carbon monoxide and hydrogen, the methanol synthesis feed stream comprising at least a portion of the carbon monoxide from the first product stream; andin a methanol synthesis zone, contacting the methanol synthesis feed stream with a methanol synthesis catalyst under conditions sufficient to form a second product stream comprising methanol.

2. The process of claim 1 , wherein the contacting the methanol synthesis feed stream with the methanol synthesis catalyst in the methanol synthesis zone is conducted with a methanol selectivity of at least 75%, e.g., at least 80%, or at least 85%.

3. The process of claim 1 or 2, wherein the methanol synthesis catalyst comprises copper, optionally in combination with zinc.

4. The process of any one of the preceding claims, wherein contacting of the FT feed stream with the FT catalyst in the FT reaction zone is conducted at a temperature in the range of 200-500°C.

54. The process of any one of the preceding claims, wherein the methanol synthesis step is performed with a carbon product selectivity of at least 20% for methanol.

5. The process of any one of the preceding claims, wherein the methanol synthesis feed stream has a molar ratio of hydrogen to carbon monoxide in the range of 1 :2 to 10:1 , preferably 1:2 to 8:1, more preferably 1:1 to 5:1.

6. The process of any one of the preceding claims, wherein the first product stream has a molar ratio of hydrogen to carbon monoxide in the range of 1:2 to 10:1, preferably 1:1 to 8:1, more preferably 1 : 1 to 5:1, more preferably still 1:1 to 3:1.

537. The process of any one of the preceding claims, wherein the FT reaction zone operates under at least one of the following conditions:o a temperature of greater than 250°C;o a pressure of 10 to 100 barg,and / or wherein the FT feed stream is delivered to the FT reaction zone under at least one of the following conditions:o a GHSV of greater than 2,000 h-1;o a ratio of hydrogen to carbon dioxide of less than 4: 1 , preferably less than 3: 1 , more preferably less than 2:1.

9. The process of any one of the preceding claims, wherein contacting the methanol synthesis feed stream with a methanol synthesis catalyst occurs at a temperature of between 150 to 400°C, preferably at a temperature of between 250 to 350°C.

10. The process of any one of the preceding claims, wherein the molar ratio of hydrogen to carbon monoxide in the methanol synthesis feed stream is adjusted to be lower than the molar ratio of hydrogen to carbon monoxide in the first product stream.

11. The process of claim 10, wherein the molar ratio of hydrogen to carbon monoxide is adjusted by selectively reacting hydrogen from the first product stream to create a modified product stream, and using this modified product stream to form the methanol synthesis feed stream, optionally wherein said selectively reacting hydrogen comprising hydrogen of the first product stream being consumed through a hydrogenation reaction with a reactant, such as a C2-C4 olefin.

12. The process of claim 10, wherein the molar ratio of hydrogen to carbon monoxide is adjusted by selectively removing hydrogen from the first product stream to create a modified product stream, and using this modified product stream to form the methanol synthesis feed stream, preferably wherein selective removal of hydrogen from the first product stream is achieved using a hydrogen selective membrane or pressure swing adsorption.

13. The process of any one of claim 10, wherein the molar ratio of hydrogen to carbon monoxide in the second feed stream is adjusted by converting C1-C4 hydrocarbons of the first product stream to produce carbon monoxide, and including this carbon monoxide in the methanol synthesis feed stream, for example, wherein conversion of the C1-C4 hydrocarbons is carried out by reforming, for example by partial oxidation, steam reforming or dry CO2 reforming.5414. The process of any one of the preceding claims, wherein the first product stream is separated to provide a water rich stream and a water poor stream, wherein at least a portion of the water poor stream is used to form the methanol synthesis feed stream.

15. The process of any one of the preceding claims, wherein additional carbon monoxide is added to the methanol synthesis feed stream from an external source.

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