Methanol decomposition in presence of water

Abstract

The present application discloses methods of decomposing methanol into carbon monoxide and hydrogen The method involves providing a first feed stream comprising methanol and water; contacting the first feed stream with a methanol decomposition catalyst to decompose at least a portion of the methanol to form a first product stream comprising H2 and CO; wherein the methanol decomposition catalyst comprises at least one metal supported on a support comprising ceria or a mixed oxide comprising a mixture of alumina and ceria, wherein the at least one metal is present in the range of 0.5 to 10% by weight of the methanol decomposition catalyst, based on the total weight of the methanol decomposition catalyst; and wherein the molar ratio of water to methanol in the first feed stream is between 0.05:99.95 and 40:60. Also disclosed are a process for performing an integrated Fisher-Tropsch synthesis using the products of the methanol decomposition as a feed stream.

Description

METHANOL DECOMPOSITION IN PRESENCE OF WATERFIELD OF THE INVENTIONThe present invention relates to methods for decomposing methanol into hydrogen and carbon monoxide, and to catalysts suitable for use in such methods.BACKGROUNDMethanol has great promise as a renewable feedstock for a range of industrial processes. It is a common and inexpensive commodity chemical which may be produced from numerous sources, including fermentation, biomass pyrolysis, catalytic reaction of syngas, and CO2 hydrogenation. Advantageously, it is a liquid at ambient temperatures and pressures, allowing it to be transported through low-pressure pipelines, ships, or trucks, and thus generally allows for increased transportation efficiency as a liquid.Methanol holds especially great promise as a hydrogen carrier since it holds the highest hydrogen to carbon ratio of any liquid fuel and is much easier to store and transport than hydrogen itself.One option for unlocking hydrogen from methanol is steam reforming, which produces hydrogen and carbon dioxide. Whilst carbon dioxide in itself can serve as a feedstock for other processes, a potentially more attractive route is to decompose methanol into hydrogen and carbon monoxide (i.e. syngas) through use of a suitable catalyst. The hydrogen or syngas produced from methanol decomposition has the potential to be used for a wide range of purposes, including interfacing with other industrial processes such as the Fischer-Tropsch production of hydrocarbons (as explored in the applicant’s earlier application WO 2024 / 033867).Catalysed methanol decomposition has been disclosed in the art, such as in US 4,716,859, US 6,541,142 and US 9,833,773, Usami, et al., “Catalytic methanol decomposition at low temperatures over palladium supported on metal oxides.” Appl. Cat. A 171(1): 123-130 (1998), and in Hargreaves, J.S.J. and Ormsby, G. Catalysis 2007, 20. 107-121. However, information on how to optimise such decomposition reactions to achieve high productivity and / or selectivity, and to allow the reaction to interface with other processes and applications, is relatively limited. Given the potential of methanol to serve as a key driver for the adoption and scaling of green technologies, there is a need to develop methods and materials which tailor methanol decomposition to suit specific industrial uses.US 4,780,300 discloses a process for cracking 100 moles methanol in admixture with 1 to 99 moles of water using a specified catalyst. Information about the relative selectivity to byproducts such as methane is not discussed.The present invention has been devised in light of the above considerations.SUMMARY OF THE INVENTIONThe invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.Various side-products can be generated alongside H2 and CO during methanol decomposition, including methane, CO2, dimethyl ether (CH3OCH3, typically abbreviated “DME”) and methyl formate. It is desirable to minimise the production of these side-products, since they constitute wasted carbon and hydrogen which could be used to make CO and H2. Formation of CO2 and DME can at least partially be dealt with by recycling and reprocessing these components to make further methanol which can be fed back into the decomposition process. However, recycling methane is less straightforward, and hence it is generally simpler to remove methane after its production, wasting carbon and hydrogen locked up in the starting methanol, and leading to issues around how to deal with the waste methane - a significantly more potent greenhouse gas than carbon dioxide. Thus, it is particularly beneficial to identify processes which achieve high levels of selectivity for H2 and CO production over other products at a suitable level of productivity, in particular processes which show minimal production of methane.It is especially useful to identify processes which can achieve highly selective production of CO and / or H2 under conditions which are compatible with industrial processes which utilise those compounds, such as Fischer-Tropsch. As recognised in the applicant’s earlier application WO 2024 / 033867, to fully benefit from the advantages of methanol as a commodity, it is beneficial to take the product stream from methanol decomposition and use this directly as the feedstock for a follow-on process, such as a Fischer-Tropsch process. For reasons of space and simplicity, it is particularly desirable to integrate methanol decomposition and subsequent use of its resulting products into a single reactor - that is, to carry out the methanol decomposition and follow on process in the same reactor. However, such an approach is challenging, since the optimal conditions for the follow-on process may be very different to the optimal conditions for methanol decomposition. In particular, the prior art has generally only reported methanol decomposition at relatively low pressures, whereas industrial processes such as Fischer-Tropsch processes typically operate at much higher pressures. Thus, it is particularly beneficial to identify methanol decomposition catalysts which achieve appropriate productivity and selectivity under similar pressure and temperature conditions to other industrial processes which utilise syngas, such as Fischer-Tropsch.The present inventors have now discovered that the introduction of water along with methanol can be used to increase the selectivity of methanol decomposition for carbon monoxide compared to methanol. Furthermore, they have discovered that a particularly high conversion rate can be achieved when this approach is adopted with catalysts supported on certain types of support.Thus, in a first aspect, the present invention provides a method for decomposing methanol, the method comprising:providing a first feed stream comprising methanol and water; contacting the first feed stream with a methanol decomposition catalyst to decompose at least a portion of the methanol to form a first product stream comprising H2 and CO; wherein the methanol decomposition catalyst comprises at least one metal supported on a support comprising ceria or a mixed oxide comprising a mixture of alumina and ceria, wherein the at least one metal is present in the range of 0.5 to 10% by weight of the methanol decomposition catalyst, based on the total weight of the methanol decomposition catalyst; and wherein the molar ratio of water to methanol in the first feed stream is between 0.05:99.95 and 40:60, preferably between 5.0:95.0 to 20:80.The inventors’ discovery that incorporating water in the feed stream can be used to boost the production of carbon monoxide relative to methane was unexpected.The applicant’s earlier application WO 2024 / 033867 reports that water reacts with carbon monoxide to cause formation of CO2 and H2 through the water-gas shift reaction (see paragraph

[0020] ), and thus it was expected that increasing water content would serve to decrease selectivity for carbon monoxide - the opposite of the effect actually observed in the experiments reported herein.US 4,176,859 A indicates adding water during methanol decomposition can boost the proportion of hydrogen produced, but indicates that this results in the production of carbon dioxide (see column 3, lines 9 to 26 and column 4, lines 36 to 45) consistent with the chemical reaction schemes at column 1 , lines 54 to 65. Since the document is particularly concerned with efficiently generating hydrogen for use in combustion engines or fuel cells (see column 1 , lines 20 to 44 and column 2, lines 45 to 57), it teaches that the carbon dioxide should be separated from the hydrogen. Example 8 of that document reports decomposition of methanol containing 2.2 vol% H2O, but the water content is not varied to show its effect on the product stream. There is no suggestion that adding water would or could boost the production of carbon monoxide.Preferably, the at least one metal of the methanol decomposition catalyst comprises platinum. As demonstrated in the examples of this application, methanol decomposition catalysts comprising platinum supported on a ceria or alumina support show a particularly useful enhancement in carbon monoxide production relative to methane at increasing water amounts.Preferably the support is ceria. The examples of the application show particularly beneficial behaviour when ceria is used as a support, especially for ceria-supported platinum.Optionally, the first feed stream comprises at least 5 mol% methanol.Preferably, the method achieves a methanol conversion of at least 30%, more preferably at least 50%, most preferably at least 90%.Preferably, the method provides a carbon product selectivity for methane of less than 5%, more preferably less than 3%.Optionally, contacting the first feed stream with the methanol decomposition catalyst is carried out at a pressure of at least 20 barg. The inventors have surprisingly discovered that good methanol conversion and carbon monoxide productivity and selectivity can be achieved even at elevated pressures. Advantageously, this allows the methanol decomposition to be carried out under conditions comparable to those used in Fischer-Tropsch syntheses (which generally favour higher pressure and lower temperatures), facilitating the integration of the methanol decomposition reaction with a follow-on Fischer-Tropsch step, as described in more detail below.Optionally, contacting the first feed stream with the methanol decomposition catalyst occurs at a temperature of at least 150°C, or at least 250°C, or at least 350°C. Again, such temperatures are comparable to those favoured in Fischer-Tropsch syntheses, facilitating the integration of the methanol decomposition reaction with a follow-on Fischer-Tropsch step.In view of the compatibility of reaction conditions with Fischer-Tropsch synthesis, a further aspect of the present invention provides a process for performing an integrated Fisher-Tropsch synthesis, the process comprising: providing a first feed stream comprising methanol and water contacting the first feed stream with a methanol decomposition catalyst to decompose at least a portion of the methanol to form a first product stream comprising H2 and CO as described in relation to the first aspect of the invention; optionally providing a second feed stream comprising H2 and at least a portion of the CO of the first product stream; and contacting the first product stream or, optionally, the second feed stream, with a Fischer- Tropsch catalyst to perform a Fischer-Tropsch synthesis to provide a second product stream comprising C5+ hydrocarbons.In view of the advantages found by introducing water, a further aspect of the present invention provides use of water to reduce methane production during methanol decomposition by a methanol decomposition catalyst. The methanol decomposition here may be carried out by a method comprising: providing a first feed stream comprising methanol and water; contacting the first feed stream with a methanol decomposition catalyst to decompose at least a portion of the methanol to form a first product stream comprising H2 and CO; wherein the methanol decomposition catalyst comprises at least one metal supported on a support comprising ceria, alumina, or a mixed oxide comprising a mixture of alumina and ceria, wherein the at least one metal is present in the range of 0.5 to 10% by weight of themethanol decomposition catalyst, based on the total weight of the methanol decomposition catalyst; and wherein the molar ratio of water to methanol in the first feed stream is between 0.05:99.95 and 40:60, preferably between 5.0:95.0 to 20:80. Optionally, the methanol decomposition is carried out by a process according to the first aspect.In another aspect, the present invention provides use of water to increase the productivity of carbon monoxide relative to methane during methanol decomposition by a methanol decomposition catalyst. The methanol decomposition here may be carried out by a method comprising: providing a first feed stream comprising methanol and water; contacting the first feed stream with a methanol decomposition catalyst to decompose at least a portion of the methanol to form a first product stream comprising H2 and CO; wherein the methanol decomposition catalyst comprises at least one metal supported on a support comprising ceria, alumina, or a mixed oxide comprising a mixture of alumina and ceria, wherein the at least one metal is present in the range of 0.5 to 10% by weight of the methanol decomposition catalyst, based on the total weight of the methanol decomposition catalyst; and wherein the molar ratio of water to methanol in the first feed stream is between 0.05:99.95 and 40:60, preferably between 5.0:95.0 to 20:80. Optionally, the methanol decomposition is carried out by a process according to the first aspect.As used herein, a “feed stream” is used to mean the total material input to a process step, e.g., methanol decomposition reaction, regardless of whether provided in a single physical stream or multiple physical streams, and whether through a single inlet or multiple inlets. Similarly, a “product stream” is used to mean the total material output from a process step, regardless of whether provided in a single physical stream or multiple physical streams, and whether through a single reactor outlet or multiple reactor outlets.BRIEF DESCRIPTION OF THE FIGURESEmbodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:FIGURE 1 shows a schematic of a process according to an example embodiment of the invention.FIGURE 2 shows a schematic of an integrated methanol decomposition and Fischer-Tropsch reaction carried out in the same reactor, according to an example embodiment of the invention.FIGURE 3 is a plot showing the effect of increasing water content on methanol conversion efficiency for a range of catalysts.FIGURE 4 is a plot showing the effect of increasing water content on CO productivity for a range of catalysts.FIGURE 5 is a plot showing the effect of increasing water content on methane productivity for a range of catalysts.FIGURE 6 is a plot showing the effect of increasing water content on the amount of CO produced relative to methane.FIGURE 7 is a plot showing the effect of increasing water content on CO selectivity for a range of catalysts.FIGURE 8 is a plot showing the effect of increasing water content on methane selectivity for a range of catalysts.DETAILED DESCRIPTION OF THE INVENTIONAspects 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.Catalyst formatCatalytic materialThe methanol decomposition catalyst may include one or more transition metals selected from Groups 6-12of the periodic table. In particular embodiments, the methanol decomposition catalyst may comprise one or more of Cr, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ir, or Pt, or mixtures thereof. Optionally, the one or more transition metals are selected from Groups 7-11, preferably Groups 7, 10 or 11 ; more preferably from Groups 10 or 11, most preferably from Group 10.Optionally, the methanol decomposition catalyst comprises a further element, such as one or more of Sc, Y, Ti, Zr, Ce, B, Al, Ga, In, Si, Ge, Sn, or Sb.Preferably, the methanol decomposition catalyst includes Pt or Cu. Most preferably, the methanol decomposition catalyst includes Pt, since the present inventors have discovered particularly high methanol conversion and CO productivity for Pt catalysts.Optionally, the methanol decomposition catalyst is an alloy, such as an intermetallic alloy.SupportThe methanol decomposition catalyst is a supported catalyst.The support material may be in the form of a powder, granulate, shaped particle, such as a preformed sphere or microsphere, or extrudate.Optionally, the support may comprise or be a refractory oxide. Optionally, the support is a refractory oxide.In the methods described herein, the support may comprise ceria or a mixed oxide of ceria and alumina. In the uses described herein, the support may comprise ceria, alumina, or a mixed oxide of ceria and alumina, preferably ceria or a mixed oxide of ceria and alumina. Optionally for the methods and uses described herein, the support comprises or is ceria.Optionally for the methods and uses described herein, the support comprises a majority (e.g. greater than 50 wt%, greater than 60 wt%, greater than 75 wt%, greater than 90 wt% or greater than 95 wt%, based on 100 wt% of the support) of ceria, or of a mixed oxide of ceria and alumina. Optionally for the methods and uses described herein, the support comprises a majority (e.g. greater than 50 wt%, greater than 60 wt%, greater than 75 wt%, greater than 90 wt% or greater than 95 wt%%, based on 100 wt% of the support) of ceria.Preferably for the methods and uses described herein, the support consists essentially of ceria or a mixed oxide of ceria and alumina. Preferably for the methods and uses described herein, the support consists essentially of ceria. Optionally for the uses described herein, the support consists essentially of alumina. Preferably for the methods and uses described herein, the support consists of ceria (without the presence of other support materials). Optionally for the uses described herein, the support consists of alumina (without the presence of other support materials).The one or more metals supported on the support may constitute at least 1 wt.%, at least 2 wt.%, at least 2.5 wt.%, at least 3 wt.%, at least 3.5 wt.%, at least 4 wt.%, at least 4.5 wt.% or at least 5 wt.% of the weight of the methanol decomposition catalyst. The upper limit for the amount of the one or more metals may be, for example, up to 9 wt.%, up to 8 wt.%, up to 7 wt.%, up to 6 wt.% or up to 5 wt.% of the methanol decomposition catalyst.Catalyst formationThe methanol decomposition catalyst may be formed by standard methods known in the art, such as impregnation or co-precipitation.For example, the methanol decomposition catalyst may be formed by: (i) contacting a support material with an impregnating solution containing one or more catalyst-precursor compounds to form an impregnated support material; and (ii) drying and calcining the impregnated support material to form the methanol decomposition catalyst.Reference herein to "impregnation" or "impregnating" is intended to refer to contact of the support material with a solution, or solutions, of catalyst-precursor compound(s), before drying in order to achieve precipitation of the catalyst-precursor compound(s). Impregnation with a fully dissolved solution, or solutions, of the catalyst-precursor compound(s) ensures good dispersion of the catalyst-precursor compound(s) on the support material and is thus preferred. This is in contrast, for instance, to the use of partially dissolved catalyst-precursor compound(s) in 'solid solutions' or suspensions, where the level of dispersion of the catalyst-precursorcompound(s) across the surface, and in the pores, of the support material can fluctuate depending on the nature of the precipitation on the support material. Furthermore, use of a fully dissolved solution, or solutions, of catalyst-precursor compound(s) also has less of an impact upon the resulting morphology and bulk crush strength of an extrudate formed thereafter compared with solid solutions. Nevertheless, benefits of the present invention can also be realised in the case where a solid solution, or solutions, of a partially undissolved catalystprecursor compound is used.Impregnation of the support material may be achieved by any suitable method of which the skilled person is aware, for instance by vacuum impregnation, incipient wetness, or immersion in excess liquid. The incipient wetness technique is so-called because it requires that the volume of impregnating solution be predetermined so as to provide the minimum volume of solution necessary to just wet the entire surface of the support, with no excess liquid. The excess solution technique as the name implies, requires an excess of the impregnating solution, the solvent being thereafter removed, usually by evaporation. Where a powder or granulate of support material is impregnated, the powder or granulate may be admixed with the impregnating solution by any suitable means of which the skilled person is aware, such as by adding the powder or granulate to a container of the impregnating solution and stirring.The support material may be in the form of a powder, granulate, shaped particle, such as a preformed sphere or microsphere, or extrudate. Reference herein to a powder or granulate of a support material is understood to refer to free flowing particles of a support material or particles of support material that have undergone granulation and / or sieving to be a particular shape (e.g. spherical) and size range. Reference herein to an "extrudate" is intended to mean a support material that has undergone an extrusion step and therefore may be shaped. In the context of the present invention, the powder or granulate is in a form which is suitable for impregnation with a solution of the catalyst-precursor compound(s), and subsequent extrusion or forming into other shaped particles.Suitable catalyst-precursor compounds are those which contain the metal of interest and are thermally decomposable to an oxide of the metal following calcination and which are preferably completely soluble in the impregnating solution. The catalyst-precursor compounds may be, for example, a nitrate, acetate, acetylacetonate, chloride or sulphate of the metal of interest.The solvent of the impregnating solution(s) may be either an aqueous solvent or a nonaqueous, organic solvent. Suitable non-aqueous organic solvents include, for example, alcohols (e.g. methanol, ethanol and / or propanol), ketones (e.g. acetone), liquid paraffinic hydrocarbons and ethers. Alternatively, aqueous organic solvents, for example an aqueous alcoholic solvent, may be employed. Preferably, the solvent of the impregnating solution(s) is an aqueous solvent.When more than one catalyst-precursor compound is used, the impregnation of the support material with the catalyst-precursor compounds may occur in a single step, without anyintermediate drying or calcination steps to separate the loading of the different components. As the skilled person will appreciate, the different catalyst-precursor compounds may be applied to the support material successively or simultaneously in separate impregnation solutions or suspensions, or preferably an impregnation solution or suspension comprising all of the catalyst-precursor compounds is used.The concentration of the one or more catalyst-precursor compounds in the impregnating solution(s) is not particularly limited, although preferably the catalyst-precursor compound(s) is / are fully dissolved. When a powder or granulate of support material is impregnated and immediately followed by an extrusion step, the amount of the impregnating solution(s) is preferably suitable for forming an extrudable paste.Impregnation of the support material is usually followed by drying of the impregnating solution in order to effect precipitation of the catalyst-precursor compound(s) on to the support material and preferably also to remove bound solvent of the impregnating solution (e.g. water). Drying therefore does not, for instance, lead to full decomposition of the catalyst-precursor compound(s) or otherwise lead to a change in oxidation state of such compounds. As will be appreciated, in embodiments where an extrusion is performed, complete drying and removal of solvent (e.g. bound solvent) of the impregnating solution may occur after forming of a shaped particle, for example by extrusion. Drying is suitably conducted at temperatures from 50 °C to 150 °C, preferably 75 °C to 125 °C. Suitable drying times are, for example, from 5 minutes to 72 hours. Drying may suitably be conducted in a drying oven or in a box furnace, for example, under the flow of an inert gas at elevated temperature.Next, the impregnated support material is subjected to a calcination step. As will be understood, calcination is required for converting the catalyst-precursor compound which has been impregnated on the support material into an oxide. Thus, calcination leads to thermal decomposition of the catalyst-precursor compound(s), and not merely removal of bound solvent of an impregnating solution, as for instance in the case of drying. Calcination may be performed by any method known to those of skill in the art, for instance in a fluidized bed, rotary kiln, box furnace or ashing kiln at a temperature of at least 250 °C, preferably from 275 °C to 500 °C.Finally, the methanol decomposition catalyst may be activated prior to / during use, for example, by reduction (reductive activation). The person of skill in the art can identify suitable conditions for activating the catalyst. The methanol decomposition catalyst may be activated using hydrogen gas as a reducing agent. The hydrogen gas may be mixed with other gases, such as an inert carrier gas. Examples of such inert carrier gases include nitrogen, carbon dioxide, argon, or helium.Processing conditionsThe contacting of the feed stream comprising methanol with the metal decomposition catalyst occurs at a temperature and pressure suitable to effect efficient methanol decomposition.The temperature may be, for example, 200-500°C, such as 200-450°C, or 200-400°C, or 200- 350°C, or 200-300°C, or 250-500°C, or 250-450°C, or 250-400°C, or 250-300°C, or 300-500°C, or 300-450°C, or 300-400°C.The pressure may be, for example, in the range of 0 to 50 barg (barg referring to pressure in bars above ambient or atmospheric pressure), such as between 10-40 barg.The gas hourly space velocity (GHSV) for continuous operation may be in the range 50 to 200,000 IT1, such as 10,000 to 200,000 h’1, 50,000 to 200,000 h’1, or 100,000 to 200,000 h’1.Feed streamThe methanol is provided as part of a feed stream. In instances where the products of methanol decomposition are themselves used as the feed stream for a further process, the feed stream provided to the methanol decomposition catalyst may be referred to as the “first feed stream”.Preferably the feed stream comprises at least 5 mol% methanol (the mol% being calculated as a percentage of the whole feed stream). For example, in particular embodiments, the feed stream comprises at least 7.5 mol% methanol, e.g., at least 10 mol% methanol, or at least 15 mol% methanol, or at least 20 mol% methanol, or at least 25 mol% methanol.The feed stream incorporates water. The water may be present in the methanol delivered to the feed stream; for example, the water content of the liquid methanol may be adjusted by addition of water or by dehydration. The lower limit for the molar ratio of water to methanol (water: methanol) in the feed stream may is 0.05:99.95, such as 0.1:99.9, 1.0:99.0, 2.0:98.0, 3.0:97.0, 4.0:96.0; 5.0:95.0, or 6.0:94.0. The upper limit for the molar ratio of water to methanol is 40:60, such as 30:70, or 20:80. Suitable ranges for the molar ratio may be, for example, 1:99 to 30:70; 1:99 to 20:80; 1:99 to 10:90; or 2:98 to 10:90. Optionally, the range may be, for example, 5.0:95.0 to 40:60; 5.0:95.0 to 30:70; 5.0:95.0 to 20:80; or 5.0:95.0 to 10:90.The total amount of water in the feed stream may be, for example, at least 0.005 mol%, at least 0.01 mol%, at least 0.05 mol%, or at least 0.1 mol% (the mol% being calculated as a percentage of the whole feed stream). The upper limit may be, for example, 10 mol%, 5 mol%, 4 mol%, 3 mol%, 2 mol% or 1 mol%.Optionally, the feed stream may also comprise one or more additional gases, which may be inert or reactive. In such embodiments, the feed stream may further comprise one or more of H2, CO, CO2, and N2 (including gases recycled from the product stream of the reaction, as discussed in more detail below).Preferably, the feed stream may comprise an inert carrier gas, wherein the inert carrier gas includes one or more of CO2 and N2, preferably N2. Such a gas may serve as a diluent.Additionally, or alternatively, H2 and / or CO may be added to the feed stream in order to tune the decomposition reaction and / or provide a desired product. In such embodiments, the feed stream further comprises H2 and / or CO. In various embodiments as otherwise described herein, one or more of H2, CO, CO2, and N2 may be present in first feed stream an amount in the range of up to 90 mol%, e.g., up to 80 mol%, up to 80 mol%, up to 60 mol%, up to 50 mol%, or up to 40 mol%, or up to 30 mol% (the mol% being calculated as a percentage of the whole feed stream).The components of the feed stream may be delivered as one or more combined feed stream(s), separate feed streams, or any combination thereof. By the term "combined feed stream" it is meant a feed stream which contains at least part of two or more of the components. By the term "separate feed stream" it is meant a feed stream which contains only one of the components.Preferably, hydrogen is delivered as part of the feed stream. The hydrogen used in the process may be derived from any suitable source. Non-limiting examples of processes which may provide a source of hydrogen that may be used in the process of the present invention include synthesis gas generation processes; the hydrolysis of water; and various other chemical processes, such as, for example, ethane crackers, styrene manufacture and catalytic reforming.Carbon monoxide used in the process may likewise be derived from any suitable source. Nonlimiting examples of processes which may provide a source of carbon monoxide that may be used in the process of the present invention include synthesis gas generation processes; the reduction of metal oxides; and various other chemical processes, such as, for example, the high temperature reaction of air or oxygen with a carbonaceous material (for example coal).The feed stream may be provided at elevated temperature. For example, the feed stream may have a temperature in the range of 200-500°C, such as 200-450°C, or 200-400°C, or 200- 350°C, or 200-300°C, or 250-500°C, or 250-450°C, or 250-400°C, or 250-300°C, or 300-500°C, or 300-450°C, or 300-400°C.Productivity and selectivityPreferably, the decomposition of methanol is performed with a conversion efficiency of methanol of at least 30%, e.g., at least 40%, or at least 50%, or at least 60%, or at least 65%, or at least 70%, or at least 75%, preferably at least 90%. By “conversion efficiency” we mean the weight percentage of methanol in the product stream as a percentage of the weight of methanol in the feed stream.Due to the consumption of methanol in the reaction, the product stream preferably includes no more than 75 mol% methanol, e.g., no more than 60 mol% methanol, no more than 50 mol%methanol, or no more than 25 mol% methanol (the mol% being calculated as a percentage of the whole product stream).Preferably, the product stream comprises at least 20 mol% total of CO and H2, e.g., at least 35 mol%, or at least 50 mol%, or at least 65 mol%. Without wishing to be bound by theory, methanol decomposition under these conditions is expected to generate two moles of H2 per mole of CO. Accordingly, in various embodiments as otherwise described herein, the first product stream has a molar ratio of hydrogen to carbon monoxide in the range of 0.5:1 to 5:1 , e.g., 1 :1 to 3:1 , or 1.5:1 to 2.5:1 , or 1.5:1 to 3.5: 1.Preferably, the product stream comprises no more than 20 mol% of methane e.g. no more than 15 mol% methane, no more than 10 mol% methane, no more than 5 mol% methane, no more than 3 mol% methane, no more than 2 mol% methane, or no more than 1 mol% methane.Preferably, the product stream comprises no more than 20 mol% of CO2, e.g. no more than 15 mol% CO2, no more than 10 mol% CO2, no more than 5 mol% CO2, no more than 3 mol% CO2, no more than 2 mol% CO2, or no more than 1 mol% CO2.Preferably, the product stream comprises no more than 20 mol% of DME, e.g. no more than 15 mol% DME, no more than 10 mol% DME, no more than 5 mol% DME, no more than 3 mol% DME, no more than 2 mol% DME, or no more than 1 mol% DME.Preferably, the product stream comprises no more than 20 mol% of methyl formate, e.g. no more than 15 mol% methyl formate, no more than 10 mol% methyl formate, no more than 5 mol% methyl formate, no more than 3 mol% methyl formate, no more than 2 mol% methyl formate, or no more than 1 mol% methyl formate.Preferably, the decomposition of methanol is performed with high selectivity for CO over other carbon products (i.e. with minimal formation of side-products including methane, CO2, DME and methyl formate) - that is with high carbon product selectivity for CO. 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 decomposition, subtracting the contribution from any components not derived from methanol decomposition (for example, if carbon monoxide is added to the feed stream then the contribution from this is subtracted from the carbon monoxide in the product stream). In this disclosure, STY is reported as the grams of product produced per kilogram 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.Preferably, the decomposition of methanol is performed with a carbon product selectivity of at least 50% for CO, e.g., at least 60%, or at least 70%, or at least 80%, or at least 90% for CO.Preferably, the decomposition of methanol is performed with a carbon product selectivity of no more than 20% for methane e.g., no more than 15%, or no more than 10%, or no more than 5%, or no more than 3%.Preferably, the decomposition of methanol is performed with a carbon product selectivity of no more than 20% for CO2, e.g., no more than 15%, or no more than 10%, or no more than 5%.Preferably, the decomposition of methanol is performed with a carbon product selectivity of no more than 20% for dimethyl ether (DME), e.g., no more than 15%, or no more than 10%, or no more than 5%.Preferably, the decomposition of methanol is performed with a carbon product selectivity of no more than 20% for methyl formate, e.g., no more than 15%, or no more than 10%, or no more than 5%.Particularly preferred are methods which are performed with a carbon product selectivity of greater than 60% for CO and less than 40% for methane, more preferably less than 70% for CO and less than 30% for methane.Reactor typeThe reaction zone of the present invention can conveniently be any reactor, multiple reactors, such as a series of reactors, or a part thereof, wherein the process of the present invention occurs.Suitable reactors which may be used in the process of the present invention include adiabatic bed, multi-tubular, fluidised bed, spinning basket and buss loop, and heat exchanger reactors. When more than one reactor is used, the reactors may be arranged either in series or in parallel. For reactors utilised in series, heat exchangers and / or intercoolers and / or additional reactant and / or recycle of intermediates can be employed in between successive reactors to control the reaction temperature. In one embodiment of the present invention, the process is performed in at least two adiabatic reactors in series.An example embodiment is shown in schematic view in FIG. 1. Here, in process 100 a crude methanol stream 102 is optionally combined with a feed of one or more further gases 104 to form a first feed stream 106 which is delivered into reactor 110. Reactor 110 includes a methanol decomposition reaction zone in which with methanol decomposition catalyst 112 is contacted with the first feed stream 106 and product stream 120 is formed. Here, product stream 120 is conducted from the methanol decomposition reaction zone, and unreacted methanol is substantially separated from the product stream 120 (e.g., at least 50%, at least 75%, at least 90% or at least 95% unreacted methanol is separated) and is recycled to the first feed stream 106 via methanol recycle 108.of the streamPreferably the method involves separating components from the product stream. In particular, the method preferably comprises separating CO and H2 from the product stream, optionally separating CO and H2 independently.Preferably, at least a portion of the product stream is recycled to the feed stream. For example, preferably at least a portion of methanol is separated from the first product stream and recycled to the feed stream.Optionally, at least a portion of the CO2 is separated from the product stream. The CO2 may be recycled to the feed stream or may be subjected to further processing. For example, the CO2 may be separated and used as the feed stream for a reverse water-gas shift (reverse WGSR) to form carbon monoxide and water.Optionally, at least a portion of the methane is separated from the product stream. The methane may be recycled to the feed stream or may be subjected to further processing. For example, the methane may be separated and used as the feed stream for a methane reforming process (such as steam reforming or autothermal reforming) to generate further hydrogen.Optionally, the CO and H2are stored for further use. Alternatively, the CO and H2may be used as a feedstock for further processing, such as the Fischer-Tropsch reaction to produce hydrocarbons (as described in the applicant’s earlier application WO 2024 / 033867).Fischer-T ropschThe present invention also provides a process for performing an integrated Fisher-Tropsch synthesis, the process comprising: providing a first feed stream comprising methanol contacting the first feed stream with a methanol decomposition catalyst to decompose at least a portion of the methanol to form a first product stream comprising H2 and CO in a method according to the first aspect of the invention; optionally providing a second feed stream comprising H2 and at least a portion of the CO of the first product stream; and contacting the first product stream or, optionally, the second feed stream, with a Fischer- Tropsch catalyst to perform a Fischer-Tropsch synthesis to provide a second product stream comprising C5+ hydrocarbons.The Fischer-Tropsch step of the method may be carried out in the manner taught in the applicant’s earlier application WO 2024 / 033867.The temperature of the Fischer-Tropsch synthesis can suitably be in the range of 200-400 °C, such as 200-300 °C, or 210-400 °C, or 210-300 °C, or 220-400 °C, or 220-300 °C. Forexample, the temperature of the Fischer-Tropsch synthesis may be in the range of 200-250 °C, such asor 200-240 °C, or 200-230 °C, or 200-220 °C, or 210-250 °C, or 210-240 °C, or 210-230 °C, or 220-250 °C, or 220-240 °C, or 230-250 °C. The pressure of the reaction may suitably be in the range from 10-50 barg, such as 20-50 barg, or 25-50 barg, or 10-40 barg, or 20-40 barg, or 25-40 barg or 10-35 barg, or 20-35 barg, or 25-35 barg. For example, the contacting of the first product stream or second feed stream with the Fischer-Tropsch catalyst may be performed at a pressure in the range of 20-40 barg.The Fischer-Tropsch catalyst may be selected by the person of ordinary skill in the art. In various embodiments as otherwise described herein, the Fischer-Tropsch catalyst comprises cobalt, iron, rhodium, ruthenium, or a combination thereof (e.g., comprises cobalt or iron). In particular embodiments, the Fischer-Tropsch catalyst comprises cobalt in an amount in the range of 2 to 30 wt.%, e.g., in the range of 5 to 25 wt.%, or in the range of 8 to 20 wt.%, calculated as Co(0), as a weight percentage of the Fischer-Tropsch catalyst. In particular embodiments, the Fischer-Tropsch catalyst comprises iron in an amount in the range of 15 to 95 wt.%, e.g., 25 to 95 wt.%, or 30 to 90 wt.%, calculated as Fe(0). In various embodiments as otherwise described herein, the Fischer-Tropsch catalyst further comprises manganese (e.g., comprises manganese in the amount of 0.1 to 15 wt.%, or 1 to 10 wt.%).In various embodiments as otherwise described herein, the Fischer-Tropsch catalyst is a supported catalyst, wherein the support comprises at least one of titanium oxide, zirconium oxide, cerium oxide, aluminum oxide, silicon oxide, magnesium oxide, and zinc oxide (e.g., comprises at least one of titanium oxide, aluminum oxide, and silicon oxide). For example, in particular embodiments, the support is a titanium dioxide support, or is an alumina support, or is a silica support. In various embodiments, the support is a shaped particle, e.g., an extrudate. The catalyst can be prepared using methods conventional in the art.Suitably, the Fischer-Tropsch catalyst may be activated prior to use. The Fischer-Tropsch catalyst may be activated by reductive activation, in the manner described above in relation to the methanol decomposition catalyst.Suitably, the methanol decomposition catalyst is different to the Fischer-Tropsch catalyst.The contacting of the first product stream / second feed stream with the Fischer-Tropsch catalyst and the contacting of the first feed stream with the methanol decomposition catalyst may be performed in the same plant. This can be, e.g., within different beds in the same reactor, or in different reactors. In such embodiments, the two processes may be integrated together to provide efficient transformation of methanol to hydrocarbons.Suitably, the first reaction zone comprises a first reactor in which the methanol decomposition catalyst is disposed, and wherein the second reaction zone comprises a second reactor in which the Fischer-Tropsch catalyst is disposed. The first reaction zone comprises a first catalyst bed in which the methanol decomposition catalyst is disposed, and the second reaction zone comprises a second catalyst bed in which the Fischer-Tropsch catalyst is disposed.Optionally, the first catalyst bed and the second catalyst bed are disposed within the same reactor, e.g., in catalyst stacks or catalyst bed sections. In such situations, the reactor may be held at a temperature and pressure to achieve efficient decomposition of methanol and efficient Fischer-Tropsch synthesis. As demonstrated in the examples below, this may be, for example, a temperature in the range of 200-400°C, in particular around 300-350°C.An example of such an arrangement is shown in Figure 2. Here, first feed stream 221 is provided to stacked bed reactor 225, which includes a methanol decomposition reaction zone 220 (here, a first bed of the stacked-bed reactor that includes the methanol decomposition catalyst 223) and a Fischer-T ropsch reaction zone 230 (here, a second bed of the stacked-bed reactor that includes the Fischer-Tropsch catalyst 233). The first feed stream 221 is contacted with the methanol decomposition catalyst 223 to provide a first product stream 222 that includes CO and H2. The first product stream is provided to the Fischer-Tropsch reaction zone as second feed stream 231, which is contacted with Fischer-Tropsch catalyst 233 to provide a second product stream 232 that includes C5+ hydrocarbons. Here, at least a portion of the C5+ hydrocarbons of the second product stream is conducted to hydroprocessing unit 260, where it is hydroprocessed to provide an end product stream 265. Here, at least a portion of H2 of the first product stream is separated and conducted to the hydrotreating unit 260 via stream 262. H2 can also be provided to the hydrotreating unit in the portion of the second product stream that is conducted to the hydrotreating unit.EXPERIMENTAL EXAMPLESCatalysts were prepared and tested according to the method of the invention.Example 1 - Pt(5) / CeC>2 catalystA catalyst having 2.5 wt.% Pt on a ceria support was produced by impregnation. 1.168 g of platinum nitrate solution (17 wt.% Pt) and 10 g of cerium dioxide (CeC>2) was added to a round bottom flask. To this 30 mL of de-ionized water was added, and the mixture stirred at 400 rpm at room temperature. After 4 hours the temperature was increased to 80 °C to evaporate water. Once the water had evaporated, the sample was dried further in an oven at 60°C for 18hours. After drying, the catalyst was ground using a pestle and mortar, and sieved to select particles having a size of 500 pm or less using a Fisherbrand™ Stainless Steel Test Sieve. The catalyst was then calcined by ramping the temperature from ambient temperature to 120°C at 10°C / min, holding at 120°C for 2 hours, ramping the temperature to 500°C at 2°C / min, holding at 500°C for a further 4 hours, and then allowing to cool to ambient temperature. Subsequent to calcining, the catalyst was sieved using a Fisherbrand™ Stainless Steel Test Sieve to select particles between 100-200 pm.The catalyst was loaded into a 16-channel parallel fixed-bed stainless steel reactor system. Each stainless steel reactor (300 mm in length; 3 mm external diameter; 2 mm internal diameter) housed a 25 mg bed of catalyst (having particle size fraction of 100 to 200 micronsdiameter) loaded on top of a 6 cm deep bed of an inert material (carborundum). The reactor volume above the catalyst was also packed with carborundum. The reactor was set-up in a down-flow configuration. Each reactor was maintained at a temperature of 60-400 °C and at a total pressure of 10 barg throughout the reactions, according to the scheme set out in Table 1 below. Different feeds were employed to determine the impact on the yield of carbon monoxide and hydrogen whilst maintaining a GHSV of 165,000 h’1. The effluent stream from each reactor was diluted with inert gas (nitrogen) and was periodically analysed by online gas chromatography to determine the yield of carbon monoxide and hydrogen product.The reactor conditions used are set out in steps 1-17 below, with steps 1-8 serving as an activation step. Monitoring of the reaction products was carried out in steps 15-17 to determine the effect of increasing temperature on catalyst performance.Example 2 - Pt(2.5) / Al2C>3 catalystA catalyst having 2.5 wt.% Pt on an alumina support was produced using the same procedure as Example 1 but using 10 g of AI2O3 instead of CeC>2. The catalyst was activated and tested using the same procedure taught in Example 1.Comparative Example 1 - T-2130As a comparative example, a commercially-available copper zinc oxide catalyst (T-2130, available from Sud Chemie) was used, having the composition: 33 wt.% CuO and 66 wt.% ZnO. This catalyst was chosen as a suitable comparative catalyst since it is the most preferred methanol decomposition catalyst type highlighted in the applicant’s earlier application WO 2024 / 033867. It is also known for use in methanol synthesis from syngas, and hence is expected to be a suitable methanol decomposition catalyst based on the principle of microscopic reversibility. The catalyst was activated and tested using the same procedure taught in Example 1.ResultsThe results of the experiments are summarised in Table 3 and shown in Figures 3-8.The platinum on ceria catalyst showed particularly high methanol conversion, as well as high productivity and selectivity for production of CO compared to other carbon-containing products, with CO selectivity of around 90% in the absence of water (see Figures 3-5, 7 and 8). As the amount of water was increased the overall methanol conversion decreased, and the productivity values decreased for all species apart from carbon dioxide. The increase in carbon dioxide production is expected, due to the increasing contribution to the reaction products of the water gas shift reaction. Surprisingly, alongside the increasing carbon dioxide productivity, the reaction products also led to an increase in the selectivity for carbon monoxide compared to methane - as shown in Figure 6. In particular, in the absence of water nearly ~38 times as much carbon monoxide was produced compared to methane, but when the methanol feed was adjusted to contain 5 mol% water this ratio jumped to ~53 times.The platinum on alumina catalyst showed relatively high methanol conversion, but with a propensity to form DME over other products. As with the data for platinum on ceria, the introduction of water led to an increase in the selectivity for carbon monoxide compared to methane.The results for T-2130 showed a significant decline in methanol conversion as water was introduced (a drop of roughly 35% as water was increased from 0 mol% to 5 mol%, as compared to a drop of only 5% for the platinum on ceria catalyst), as well as the same general shift towards the production of carbon dioxide observed for the platinum on ceria catalyst.However, unlike the platinum on ceria catalyst, the ratio of CO / CH4 showed no appreciable change.Table 3The 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.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.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.Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.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%.REFERENCESA number of publications are cited above in order to more fully describe and disclose the invention and the state of the art to which the invention pertains. Full citations for these references are provided below. The entirety of each of these references is incorporated herein. 1) WO 2024 / 0338672) US 4,716,8593) US 6,541 ,1424) US 9,833,7735) Usami, et aL, “Catalytic methanol decomposition at low temperatures over palladium supported on metal oxides.” Appl. Cat. A 171(1): 123-130 (1998)6) Hargreaves, J.S.J. and Ormsby, G. Catalysis 2007, 20. 107-121.

Claims

CLAIMS1. A method for decomposing methanol, the method comprising: providing a first feed stream comprising methanol and water; contacting the first feed stream with a methanol decomposition catalyst to decompose at least a portion of the methanol to form a first product stream comprising H2 and CO; wherein the methanol decomposition catalyst comprises at least one metal supported on a support comprising ceria or a mixed oxide comprising a mixture of alumina and ceria, wherein the at least one metal is present in the range of 0.5 to 10% by weight of the methanol decomposition catalyst, based on the total weight of the methanol decomposition catalyst; and wherein the molar ratio of water to methanol in the first feed stream is between 0.05:99.95 and 40:60.

2. A method according to claim 1, wherein the at least one metal comprises platinum.

3. A method according to any one of the preceding claims, wherein the molar ratio of water to methanol in the first feed stream is between 5.0:95.0 to 20:80.

4. A method according to any one of the preceding claims, wherein the first feed stream comprises at least 5 mol% methanol.

5. A method according to any one of the preceding claims, wherein the contacting is carried out at a pressure of at least 20 barg.

6. A method according to any one of the preceding claims, wherein the contacting occurs at a temperature of at least 150°C, or at least 250°C, or at least 350°C.

7. A method according to any one of the preceding claims, wherein the support is or comprises ceria.

8. A method according to claim 7, wherein the support is ceria.

9. A method according to any one of the preceding claims, which provides a methanol conversion of at least 30%, optionally at least 50%.

10. A method according to claim 9, wherein the methanol conversion is at least 90%.

11. A method according to any one of the preceding claims, which provides a carbon product selectivity for methane of less than 5%.

12. A method according to claim 11 , which provides a carbon product selectivity for methane of less than 3%.

13. A process for performing an integrated Fisher-Tropsch synthesis, the process comprising: providing a first feed stream comprising methanol and water contacting the first feed stream with a methanol decomposition catalyst to decompose at least a portion of the methanol to form a first product stream comprising H2 and CO in a method according to any one of claims 1 to 12; optionally providing a second feed stream comprising H2 and at least a portion of the CO of the first product stream; and contacting the first product stream or, optionally, the second feed stream, with a Fischer- Tropsch catalyst to perform a Fischer-Tropsch synthesis to provide a second product stream comprising C5+ hydrocarbons.

14. Use of water to reduce methane production during methanol decomposition by a methanol decomposition catalyst.

15. Use according to claim 14, wherein the methanol decomposition is carried out by a method comprising: providing a first feed stream comprising methanol and water; contacting the first feed stream with a methanol decomposition catalyst to decompose at least a portion of the methanol to form a first product stream comprising H2 and CO; wherein the methanol decomposition catalyst comprises at least one metal supported on a support comprising ceria, alumina, or a mixed oxide comprising a mixture of ceria and alumina, wherein the at least one metal is present in the range of 0.5 to 10% by weight of the methanol decomposition catalyst, based on the total weight of the methanol decomposition catalyst; and wherein the molar ratio of water to methanol in the first feed stream is between 0.05:99.95 and 40:60.

Images