Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
  • C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
  • C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
  • C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
  • C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
  • C07C29/153—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used
  • C07C29/154—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used containing copper, silver, gold, or compounds thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/06—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of zinc, cadmium or mercury
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/72—Copper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/61—Surface area
  • B01J35/613—10-100 m2/g
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/70—Catalysts, in general, characterised by their form or physical properties characterised by their crystalline properties, e.g. semi-crystalline
  • B01J35/77—Compounds characterised by their crystallite size
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C31/00—Saturated compounds having hydroxy or O-metal groups bound to acyclic carbon atoms
  • C07C31/02—Monohydroxylic acyclic alcohols
  • C07C31/04—Methanol
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals
  • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Definitions

• the invention relates to a process for producing methanol.
• reaction 1 CO2 hydrogenation to methanol is exothermic
• RWGS reverse water-gas shift
• reaction 2 endothermic
• the invention provides a process for the production of methanol by the
• the process of the invention can achieve outstanding CO2 conversions (e.g. 90%>) and methanol selectivities (>95%>), at the stoichiometric reactant ratio of 1 :3 (C02:H 2 ), with good methanol weight time yields of, for instance 1 gMeOH gcat " 1 h "1 .
• the reactant ratio employed means that all or nearly all of the hydrogen can be consumed, which minimises the amount of H 2 that needs to be recycled.
• the outstanding C0 2 conversions and methanol selectivites achieved also lead to reduced levels of carbon monoxide product, thereby reducing or avoiding the need to recycle CO.
• the process can also advantageously be used to synthesise methanol at very high weight time yields (e.g. 4.5 gMeOH gcat " 1 h “1 ), at high space velocities, again using a stoichiometric molar ratio of C0 2 to H 2 . It is a finding of the invention that such advantages can be achieved under particular high-pressure conditions and above a threshold temperature, using a Cu/ZnO-containing catalyst with a high specific copper surface area. An unexpected effect of the invention is that process is highly productive for methanol; the use of this particular catalyst allows for increasing space velocities while maintaining high conversion and selectivity to methanol.
• the invention provides a process for producing methanol, which process comprises contacting H 2 and C0 2 with a solid catalyst, at a temperature of from 200 °C to 300 °C and at a reactant pressure of from 150 bar to 500 bar, which reactant pressure is the sum of the partial pressures of the H 2 and the C0 2 , wherein:
• the molar ratio of the H 2 to the C0 2 is x: 1.0, wherein x is from 2.5 to 3.5; and the catalyst comprises (i) a copper component which is Cu, CuO or Cu 2 0, or a mixture of two or three thereof, and (ii) ZnO.
• the catalyst has a specific copper surface area (Scu) of at least 10 m 2 /g-catalyst.
• Fig. 1 is a graph showing the effects of reaction temperature and pressure on the C0 2 conversion (XC02) and methanol selectivity (SMCOH) in the high-pressure
• FIG. 2 is a graph showing the C0 2 conversion (XC02) and methanol selectivity (SMeOH) in the high-pressure stoichiometric CO2 hydrogenation under different GHSV conditions (650-100,000 h "1 , equivalent to 0.37-49.85 NL gcat "1 h “1 ) at 280 °C (46, 92, 184, and 442 bar) and at 260 °C (331 bar) using a commercial Cu/ZnO/A 03 catalyst.
• the filled symbols correspond to the catalytic results obtained with the catalyst of 100-300 ⁇ size fraction, while the empty symbols correspond to those obtained with the catalyst of 10-20 ⁇ size fraction.
• the arrows on the right indicate the thermodynamic equilibrium values at the respective temperature and pressure.
• Fig. 3 is a graph showing (top) methanol weight time yield (WTYMeOH) in high- pressure stoichiometric CO2 hydrogenation at different GHSV conditions (650-100,000 h "1 , equivalent to 0.37-49.85 NL gcat "1 h “1 ) at 280 °C (46 bar, 92 bar, 184 bar, and 442 bar) and at 260 °C (331 bar) using a commercial Cu/ZnO/Ab03 catalyst.
• WTYMeOH methanol weight time yield
• the filled symbols correspond to the catalytic results obtained with the catalyst of 100-300 ⁇ size fraction, while the empty symbols correspond to those obtained with the catalyst of 10-20 ⁇ size fraction, and (bottom) WTYMeOH at equilibrium conversion and selectivity at the different GHSVs at 280 °C (46 bar, 92 bar, 184 bar, and 442 bar) and at 260 °C (331 bar).
• Fig. 5 is a graph showing the theoretical methanol selectivity (SMeOH) at
• the invention relates to a process for producing methanol.
• the process comprises contacting H2 and CO2 with a solid catalyst, at a temperature of from 200 °C to 300 °C and at a reactant pressure of from 150 bar to 500 bar.
• the molar ratio of the H2 to the CO2 is x: 1.0, wherein x is from 2.5 to 3.5.
• the catalyst comprises (i) a copper component which is Cu, CuO or CU2O, or a mixture of two or three thereof, and (ii) ZnO.
• the catalyst has a specific copper surface area (Scu) of at least 10 m 2 /g-catalyst.
• reactant pressure means the sum of the partial pressures of the reactants.
• the reactants are H2 and CO2, and therefore the reactant pressure (of from 150 bar to 500 bar) employed in the present invention refers to the sum of the partial pressures of the H2 and CO2.
• the reactants H2 and CO2, and any other components present in addition may be pre-mixed, i.e. mixed together before the mixture is brought into contact with the catalyst, to form a reactant feed that is then contacted with the catalyst.
• the reactants can be fed into a reactor separately, in a plurality of different feeds, so that the reactant gases (and any other components present) are mixed together in situ in the presence of the solid catalyst.
• one or more further components may be also present in the reactant feed or feeds that are contacted with the catalyst, in addition to the reactants H 2 and C0 2 .
• the one or more further components are typically gases.
• a non- oxidising gas or an inert gas may additionally be present.
• An inert gas component could for example be present as a carrier gas.
• Nitrogen, or a noble gas may for instance be present.
• a noble gas is present. Often, when a noble gas is present, the noble gas is argon.
• the one or more further components present in the reactant feed or feeds may additionally or alternatively include, for example, H 2 0, which may be present in the form of water vapour or steam. Also, the one or more further components present in the reactant feed or feeds that are brought into contact with the catalyst, may or may not include CO.
• the reactant feed or feeds do not comprise CO, i.e. CO may be absent from the reactant feed or feeds that are brought into contact with the catalyst.
• the reactant feed or feeds do comprise CO.
• the process may comprise recycling of unreacted components (i.e. re-feeding) and such unreacted components may include CO.
• the molar ratio of C02:CO in the feed is high, for instance greater than 10: 1, more preferably greater than 100:1, and even more preferably greater than 1000: 1 , or greater than 10000:1. This is because the invention is concerned with the production of methanol from CO2 and H2, not from CO and H2.
• the total pressure (which may alternatively be referred to as the "reaction pressure") will of course be higher than the sum of the partial pressures of the H2 and the CO2 reactant gases.
• the reaction pressure will be higher than the reactant pressure in such cases, the reactant pressure always being the sum of the partial pressures of only the H2 and the CO2.
• reaction pressure the total pressure
• reaction pressure of 50 bar would correspond to a reactant pressure of 46 bar
• reaction pressure of 200 bar would correspond to a reactant pressure of 184 bar
• reaction pressure of 360 bar would correspond to a reactant pressure of 331 bar
• a reaction pressure of 480 bar would correspond to a reactant pressure of 442 bar, if the feed composition consisted of C0 2 , 3 ⁇ 4 and Ar in a molar ratio of 23 : 69 : 8.
• the volume ratio of (a) the H 2 and CO2 combined, to (b) the other components, (a):(b), may be equal to or greater than 9: 1.
• the other component or components usually a gas or gases
• the other gases may for instance make up equal to or less than 8 % by volume of the reactant feed or feeds, or for instance equal to or less than 5 % by volume, or equal to or less than 2 % by volume.
• the other gases may for instance make up equal to or less than 1 % by volume of the reactant feed or feeds, for instance equal to or less than 0.5 % by volume, or equal to or less than 0.1 % by volume.
• the reactant feed or feeds that are contacted with the catalyst may consist essentially of the H 2 and CO2 reactants.
• the reactant feed or feeds that are contacted with the catalyst may consist of the H2 and CO2 reactants.
• the reactant feed or feeds comprise (and more typically consist essentially of, or consist of) the H 2 and CO2 reactants, and equal to or less than 10 % by volume of an inert gas. More typically the proportion of the inert gas is equal to or less than 8 % by volume, for instance equal to or less than 5 % by volume, or equal to or less than 2 % by volume of an inert gas.
• the inert gas may for instance make up equal to or less than 1 % by volume of the reactant feed or feeds, for instance equal to or less than 0.5 % by volume, or equal to or less than 0.1 % by volume.
• the inert gas may be as further defined above, for instance it may be nitrogen or a noble gase. Often, the inert gas is argon.
• the molar ratio of the H 2 to the CO2 is x: 1.0, wherein x is from
• x may for instance be from 2.6 to 3.4, or, say, from 2.7 to 3.3.
• x may be from 2.8 to 3.2, or, for instance, from 2.9 to 3.1.
• x is 3.0.
• x may be from 2.5 to 3.3, for instance from 2.6 to 3.2 or, for example, from 2.7 to 3.1.
• x may be from 2.8 to 3.1. Again, however, it is preferred that x is from 2.9 to 3.1, for instance about 3.0.
• the step of contacting the H 2 and C0 2 with the solid catalyst comprises passing the H 2 and CO2 over the catalyst.
• the step of contacting the H 2 and CO2 with the solid catalyst typically comprises passing the H 2 and CO2, and the one or more other components that are present in the reactant feed or feeds, over the catalyst.
• passing the H 2 and CO2 over the catalyst comprises passing the H 2 and CO2 through a reactor comprising said catalyst.
• passing the H 2 and CO2 over the catalyst comprises passing the H 2 and CO2 through a reactor comprising a fixed bed of the catalyst.
• the process of the invention can however be operated as a batch process.
• Operating the process of the invention as a batch process has the advantage that the contact time between the reactant gases and the catalyst is comparatively very high, leading to very high CO2 conversion and very high methanol selectivity.
• the process may be a batch process.
• a continuous process is preferred.
• the process of the invention when operated as a continuous process, can still afford outstanding CO2 conversions (e.g. 90%) and methanol selectivities (>95%), and at the same time also render good methanol yields of, for instance 1 gMeOH gcat "1 h "1 .
• very high methanol yields of, for example, 4.5 gMeOH gcat "1 h "1 can be achieved, and in some cases even higher yields, for instance 15.3 gMeOH gcat "1 h "1 .
• methanol selectivity and “selectivity to methanol formation”, expressed as a percentage, refer to the molar amount of methanol produced with respect to the total molar amount of all the carbon-containing products obtained by the reaction.
• carbon dioxide conversion and “CO2 conversion” have the same meaning, and are used interchangeably. They refer to the molar amount of carbon dioxide (CO2) transformed into another chemical compound relative to the initial molar amount of carbon dioxide. In the specific case of a continuous process, they refer to the "carbon dioxide per-pass conversion", i.e. the molar amount of carbon dioxide transformed into another chemical compound relative to the initial molar amount of carbon dioxide, after one pass through the reactor. Alternatively, in the specific case of a batch process, they refer to the molar amount of carbon dioxide transformed into another chemical compound relative to the initial amount of carbon dioxide, at the end of the reaction. In the context of the invention, the conversion is expressed as a percentage and it can be calculated by dividing the number of moles of carbon containing products formed during the process by the number of moles of carbon dioxide initially present.
• contacting the H 2 and C0 2 with the solid catalyst typically comprises passing the H 2 and CO2 (plus any other component that is present in the reactant feed or feeds, which may be as further defined above, and may, for instance, be argon) over the catalyst at a space velocity of at least 500 h "1 .
• the step of contacting the H 2 and CO2 with the solid catalyst typically comprises passing the H 2 and CO2, and the one or more other components that are present in the reactant feed or feeds, over the catalyst at a space velocity of at least 500 h "1 .
• space velocity refers to the quotient of the entering volumetric flow rate of the reactant feed divided by the volume of the reactor which is occupied by the catalyst (including the catalyst volume), and indicates the reactor volumes of feed that can be treated in a unit time.
• uo represents the volumetric flow rate of the reactant feed entering the reactor (e.g. expressed in m 3 per second or m 3 per hour)
• V represents the volume of the reactor itself (e.g. expressed in m 3 ) which is occupied by the catalyst (including the catalyst volume).
• Special values for this measurement exist for liquids and gases, and for systems that use solid catalysts.
• GHSV gas hourly space velocity
• the space velocity referred to herein is the gas hourly space velocity.
• contacting the H 2 and CO2 with the solid catalyst comprises passing the H 2 and CO2 over the catalyst at a gas hourly space velocity of at least 500 h "1 .
• another component is present in the reactant feed or feeds, such as one or more further components as further defined above, e.g. argon, then the step of contacting the H 2 and C0 2 with the solid catalyst typically comprises passing the H 2 and CO2, and the one or more other components that are present in the reactant feed or feeds, over the catalyst at a gas hourly space velocity of at least 500 h "1 .
• the solid catalyst used in the process of the invention comprises zinc oxide (ZnO) and a copper component.
• the copper component is Cu, CuO or CU2O, or a mixture of two or three thereof.
• the copper component may be CuO; a mixture of CuO and CU2O; a mixture of CuO, CU2O and Cu; CU2O; a mixture of CuO and Cu; a mixture of CU2O and Cu; or Cu.
• the species present in the copper component may depend on the extent to which the copper component has undergone reduction.
• the copper component can undergo reduction in the presence of hydrogen gas.
• some or all of any CuO in the catalyst may be reduced to CU2O, Cu or a mixture thereof, and some or all of any CU2O in the catalyst may be reduced to Cu.
• the process of the invention may further comprise a step of reducing the catalyst.
• the step of reducing the catalyst may comprise treating the catalyst with hydrogen gas.
• the treatment with hydrogen gas may be carried out at an elevated temperature, for instance at a temperature above 200 °C, and more typically above 300 °C.
• the treatment may be carried out for at least 10 minutes, for instance for at least 30 minutes, or for instance, at least one hour.
• Such a step will also result in the reduction of some or all of any CuO in the catalyst to CU2O, Cu or a mixture thereof, and/or the reduction of some or all of any CU2O in the catalyst to Cu.
• the copper component in the solid catalyst used in the process of the invention is typically CuO; a mixture of CuO and CU2O; a mixture of CuO, CU2O and Cu; a mixture of CU2O and Cu; or Cu.
• the copper component in the solid catalyst may be CU2O, or a mixture of CuO and Cu.
• the copper component comprises CuO.
• the copper component is CuO; a mixture of CuO and CU2O; a mixture of CuO and Cu; or a mixture of CuO, CU2O and Cu. It may for instance be CuO; a mixture of CuO and CU2O; or a mixture of CuO, Cu 2 O and Cu.
• the copper component of the catalyst also often comprises Cu.
• the copper component may be a mixture of CuO, Cu 2 0 and Cu; a mixture of CuO and Cu; a mixture of Cu 2 0 and Cu; or Cu.
• the copper component may for instance be a mixture of CuO, Cu 2 0 and Cu.
• the catalyst employed in the present invention preferably has a specific copper surface area (Scu) of at least 10 m 2 /g-catalyst.
• specific copper surface area means the specific copper surface area of the catalyst as determined by nitrous oxide (N 2 0) pulse chemisorption using the method reported in J.W. Evans, M.S. Wainwright, A.J. Bridgewater, D.J. Young "On the determination of copper surface area by reaction with nitrous oxide", Applied Catalysis, Volume 7, Issue 1, 15 July 1983, pages 75-83.
• J. Catal., 309 (2014) 66-70 describes, in the supplementary materials, the determination of the Scu for catalysts of various compositions using the method disclosed in Evans et al., Applied Catalysis, Vol. 7, 1, 1983, p75-83, including the determination of the Scu for the catalyst referred to as "Cu/ZnO/Al 2 03 (I)".
• samples were reduced in 5% H 2 in a He stream at 603 K, followed by cooling to 363 K under He flow. A known volume of N 2 0 was then injected as pulse by using a six port valve.
• the N 2 0 at the exit was trapped in liquid N 2 and evolved N 2 was measured on the calibrated mass spectrometer, Pffeifer Omnistar GSD 301 C. Copper metal surface areas were calculated assuming 1.46 X 10 19 copper atoms/m 2 .
• the catalyst referred to as "Cu/ZnO/Al 2 03 (I)" was found to have an Scu of only 1.7 m 2 /g ca t (A. Bansode, A. Urakawa, J. Catal., 309 (2014) 66-70).
• the catalyst employed in the present invention generally has a specific copper surface area (Scu), determined by the same method, of at least 10 m 2 /g ca t. It preferably has an even greater Scu, of, for instance, at least 12 m 2 /g ca t. It may for instance have an Scu of at least 14 m 2 /g ca t, for instance an Scu of at least 15 m 2 /g ca t, or at least 16 m 2 /g ca t. It may, for example, have an Scu of at least 17 m 2 /g ca t.
• Scu specific copper surface area
• the catalyst employed in the present invention may for instance have a specific copper surface area (Scu) of from 10 m 2 /g ca t to 40 m 2 /g ca t, or for instance from any of the other lower numerical limits recited in the preceding paragraph, namely from 12 m 2 /g ca t, 14 m 2 /gcat, 15 m 2 /gcat, 16 m 2 /g ca t or 17 m 2 /g ca t, to 40 m 2 /g ca t.
• Scu specific copper surface area
• the catalyst employed in the present invention may alternatively, for instance, have an Scu of from 10 m 2 /g ca t to 35 m 2 /gcat, for instance from 12 m 2 /g ca t to 30 m 2 /g ca t, or for example from 14 m 2 /g ca t to 25 m 2 /gcat or, for instance, from 15 m 2 /g ca t to 22 m 2 /g ca t, for example from 15 m 2 /g ca t to 20
• the catalyst employed in the present invention comprises CuO, and has an average CuO crystallite size of equal to or less than 6.0 nm.
• the catalyst employed in the process of the invention has an average CuO crystallite size of equal to or less than 5.5 nm, or, for instance, equal to or less than 5.0 nm. It usually, for instance, has an average CuO crystallite size of equal to or less than 4.5 nm, for instance, equal to or less than 4.0 nm.
• the catalyst may have an average CuO crystallite size of greater than 6.0 nm, for instance from 6.0 nm to 8.0 nm. For instance, the catalyst may have an average CuO crystallite size of equal to or less than 8.0 nm.
• the average CuO crystallite size of the catalyst may, for instance, be from 1.0 to 6.0 nm, or for instance from 2.0 to 5.5 nm, or from 2.5 to 5.0 nm, for instance from 2.5 to 4.5 nm. It may for instance be from 3.0 to 4.0 nm.
• average CuO crystallite size means the average CuO crystallite size as measured by x-ray diffraction (XRD) as described in J. Catal., 309 (2014) 66-70.
• XRD x-ray diffraction
• an XRD pattern of the catalyst is recorded and the crystallite size of CuO is estimated from the full width at half maximum (FWHM) of corresponding peaks using the Scherrer equation with the shape factor of 0.9 assuming the spherical particles (A.S. Nowick, (1956) X-ray diffraction procedures for polycrystalline and amorphous materials.
• FWHM full width at half maximum
• the amount of the copper component in the catalyst is typically at least 55 % by weight.
• the catalyst typically comprises equal to or greater than 55 % by weight of the copper component.
• the copper component may be as further defined herein. More typically, the catalyst comprises equal to or greater than 58 weight % of the copper component, for instance equal to or greater than 60 weight % of the copper component.
• the catalyst may for instance comprise equal to or greater than 61 weight % of the copper component, equal to or greater than 62 weight % of the copper component, or equal to or greater than 63 weight % of the copper component.
• the amount of the copper component in the catalyst may for instance be from 55 % by weight to 75 % by weight.
• the catalyst may for instance comprise from 58 % by weight to 72 % by weight of the copper component, or for instance from 60 % by weight to 70 % by weight, or from 61 % by weight to 68 % by weight, of the copper component.
• the catalyst may for example comprise from 62 % by weight to 66 % by weight of the copper component, for instance from 63 % by weight to 65 % by weight of the copper component.
• the copper component may be as further defined anywhere herein.
• the catalysts may comprise from 60 % by weight to 80 % by weight of the copper component.
• the catalyst may comprise from 70 % by weight to 80 % by weight of the copper component.
• the catalyst typically comprises equal to or greater than 10 % by weight ZnO. More typically, the catalyst comprises equal to or greater than 12 weight % of ZnO, for instance equal to or greater than 15 weight % of ZnO.
• the catalyst may for instance comprise equal to or greater than 18 weight % of ZnO, equal to or greater than 20 weight % ZnO, or equal to or greater than 22 weight % of ZnO.
• the catalyst may for instance comprise from 10 % by weight to 35 % by weight of ZnO, or for instance from 12 % by weight to 32 % by weight, or from 15 % by weight to 30 % by weight, of the ZnO.
• the catalyst may for example comprise from 18 % by weight to 28 % by weight of the ZnO, for instance from 20 % by weight to 26 % by weight of the ZnO, for example from 22 % by weight to 25 % by weight.
• the catalyst may consist of the copper component and the ZnO.
• the amount of the copper component in the catalyst may be as defined above, and the balance will be ZnO.
• the amount of the ZnO may be as defined above, and the balance will be the copper component.
• the catalyst further comprises one or more other oxide components.
• the catalyst may further comprise one or more oxides selected from oxides of the following elements and from mixed oxides of two or more of the following elements: Al, Mg, Si, Ti, V, Cr, Zr, Mn, La, Ce and Th.
• the catalyst may further comprise one or more oxides of Al 3+ , Mg 2+ , Si 2+ , Si 4+ , Ti 3+ , Ti 4+ , V 2+ , V 3+ , V 4+ , V 5+ , Cr ⁇ , Cr 3+ , Cr 6+ , Zr 4+ , Mn 2+ , Mn 3+ , Mn 4+ , Mn 6+ , La 3+ , Ce 3+ , Ce 4+ and Th 4+ , including mixed oxides comprising two or more of Mg 2+ , Al 3+ , Si 2+ , Si 4+ , Ti 3+ , Ti 4+ , V 2+ , V 3+ , V 4+ , V 5+ , Cr ⁇ , Cr 3+ , Cr 6+ , Zr 4+ , Mn 2+ , Mn 3+ , Mn 4+ , Mn 6+ , La 3+ , Ce 3+ , Ce 4+ and Th 4+ .
• the catalyst may for instance further comprise one, two or more than two different compounds of formula A n X m , wherein A is a cation selected from Al 3+ , Mg 2+ , Si 2+ , Si 4+ , Ti 3+ , Ti 4+ , V 2+ , V 3+ , V 4+ , V 5+ , Cr 2+ , Cr 3 *, Cr 6+ , Zr 4+ , Mn 2+ , Mn 3+ , Mn 4+ , Mn 6+ , La 3+ , Ce 3+ , Ce 4+ and Th 4+ , X is O 2" , n is an integer of from 1 to 3, and m is an integer of from 1 to 9, provided that the sum of the positive charges for A n is equal to the sum of the negative charges for X m .
• A is a cation selected from Al 3+ , Mg 2+ , Si 2+ , Si 4+ , Ti 3+ , Ti 4+ , V 2+
• the amounts of the copper component and the ZnO in the catalyst are usually as defined above, and typically the balance is made up of the one or more other such oxide components.
• the catalyst further comprises AI2O3.
• AI2O3 it usually comprises at least 2 weight % AI2O3, more typically at least 5 weight % AI2O3, or, for instance, at least 8 weight % AI2O3.
• the catalyst typically comprises from 2 to 30 weight % AI2O3. It may, for instance comprise from 2 to 25 weight % AI2O3, or for instance from 5 to 25 weight % AI2O3, for example from 5 to 20 weight % AI2O3.
• the catalyst may for instance comprise from 5 to 15 weight % AI2O3, or for instance from 8 to 12 weight % AI2O3, for example from 9 to 11 weight % AI2O3, e.g. about 10 weight % AI2O3.
• the catalyst comprises 10.1 weight % AI2O3.
• the catalyst typically further comprises MgO.
• the catalyst further comprises both AI2O3 and MgO.
• the catalyst when it comprises MgO, it usually comprises at least 0.2 weight % MgO, more typically at least 0.5 weight % MgO, or, for instance, at least 0.8 weight % MgO. It may for example comprise at least 0.9 weight % MgO, for example at least 1 weight % MgO.
• the catalyst typically comprises from 0.2 to 5 weight %
• the catalyst may for instance comprise from 0.5 to 3 weight % MgO, for instance from 0.8 to 2 weight % MgO, or for instance from 0.9 to 1.7 weight % MgO.
• the catalyst may for example comprise from 1 to 2 weight % MgO. In one embodiment, the catalyst comprises 1.3 weight % MgO.
• the catalyst often therefore comprises at least 55 weight % of said copper component, at least 10 weight % ZnO, at least 2 weight % AI2O3, and at least 0.2 weight % MgO. Any of these numerical lower end-points may be as further defined herein.
• the catalyst may comprise at least 55 weight % of said copper component, at least 10 weight % ZnO, at least 5 weight % AI2O3, and at least 0.5 weight % MgO.
• the catalyst may for example comprise at least 55 weight % of said copper component, at least 10 weight % ZnO, from 2 to 30 weight % AI2O3, and from 0.2 to 5 weight % MgO. Any of these numerical lower or upper end-points may be as further defined herein.
• the catalyst may for instance comprise at least 55 weight % of said copper component, at least 15 weight % ZnO, from 5 to 30 weight % AI2O3, and from 0.5 to 5 weight % MgO.
• the catalyst comprises about 64 weight % CuO, about 25 weight % ZnO, about 10 weight % AI2O3 and about 1 weight % MgO.
• the catalyst may for instance comprise 63.5 weight % of said copper component, 24.7 weight % ZnO, 10.1 weight % AI2O3, and 1.3 weight % MgO.
• the catalyst comprises from 20 % by weight to 26 % by weight of ZnO and at least 63 % by weight of CuO.
• the catalyst may optionally further comprise from 8 % to 12 % by weight of AI2O3 and from 1 % to 2 % by weight of MgO.
• the catalyst comprises from 20 % by weight to 26 % by weight of ZnO and at least 74 % by weight of CuO.
• the catalyst comprises about 25 % by weight ZnO and about 75 % by weight of CuO.
• the catalyst may comprise 25.1 % by weight of ZnO and 74.9 % by weight of CuO.
• the temperature is typically from 260 °C to 280 °C.
• the catalyst employed in the process of the invention may be a commercially available methanol synthesis catalyst, for instance the Cu/ZnO/A 03 catalyst that is available from Alfa Aesar with product no.: 45776.
• the catalyst defined herein for use in the process of the invention may be synthesised using a standard co- precipitation method.
• the co-precipitation method for the preparation of heterogeneous catalysts is well known in the art. It usually comprises the following main steps:
• the precipitation step usually comprises the simultaneous precipitation of the metal salts.
• catalyst performance can be significantly influenced by changing the precipitation, aging, washing, and/or calcination conditions (Cf. K.P. de jong, "Synthesis of Solid catalyst", Wiley- VCH Verlag GmbH & Co. KGaA., 2009, Weinheim,. Chapter. 7. Co- precipitation, pp. 135-151; WO 2013/171239).
• the process comprises contacting the H 2 and the C0 2 with a solid catalyst at a temperature of from 200 °C to 300 °C.
• the temperature is from 210 °C to 295 °C, or, for instance, from 220 °C to 295 °C. Typically, it is from 225 °C to 290 °C, for instance from 230 °C to 290 °C.
• the temperature is from 250 °C to 300 °C, for instance from 250 °C to 290 °C, from 255 °C to 285 °C, or for example from 260 °C to 280 °C.
• the temperature may, for instance, be from 255 °C to 265 °C, for instance about 260 °C. In other embodiments, the temperature may be from 275 °C to 285 °C, for instance about 280 °C.
• Contacting the 3 ⁇ 4 and CO2 with the solid catalyst typically comprises passing the H 2 and CO2 (plus any other component that is present in the reactant feed or feeds, which may be as further defined above) over the catalyst at a space velocity of at least 500 h "1 .
• the space velocity is typically however at least 1,000 h "1 , for instance at least 1,500 h "1 , or for example at least 2,000 h "1 .
• the space velocity is at least 3,000 h “1 or, for instance, at least 3,500 h "1 . It may for instance be at least 4,000 h "1 , and may be at least 5,000 h "1 , or for example at least 6,000 h "1 or at least 7,000 ⁇ .
• the space velocity may alternatively, for instance, be at least 9,000 h "1 , for example at least 10,000 h "1 , or for instance at least 11,000 h "1 .
• the space velocity is at least 25,000 h "1 , more particularly at least 30,000 h "1 , or for instance at least 35,000 h "1 .
• the space velocity is at least 40,000 h "1 , for instance at least 45,000 h "1 or for instance at least 50,000 h "1 .
• the space velocity may for instance be at least 55,000 h "1 , for instance at least
• the space velocity is at least 80,000 h "1 , for instance at least 90,000 h “1 or at least 95,000 h "1 .
• the space velocity may, for instance, be at least 100,000 h "1 .
• the reactant pressure is often from 160 bar to 500 bar, and may, for instance be from 170 bar to 500 bar, for example from 180 bar to 500 bar. However, in some embodiments, the reactant pressure is from 150 bar to 250 bar, and may, for instance be from 160 bar to 220 bar, for example from 170 bar to 210 bar, or from 180 bar to 200 bar.
• the temperature is from 250 °C to 300 °C, more preferably from 250 °C to 290 °C, still more preferably from 255 °C to 285 °C, or even more preferably from 260 °C to 280 °C.
• a space velocity of at least 10,000 h "1 is employed, in which case the process typically comprises producing said methanol at a yield of at least 1.0 gMeOH gcat "1 h "1 .
• a space velocity of at least 30,000 h “1 may be employed at the temperatures and pressures in the preceding paragraph, in which case the process typically comprises producing said methanol at a yield of at least 2.0 gMeOH gcat "1 h "1 .
• a space velocity of, for instance, at least 50,000 h “1 may be employed at the temperatures and pressures in the preceding paragraph, in which case the process typically comprises producing said methanol at a yield of at least 3.0 gMeOH gcat "1 h “1 .
• a space velocity of at least 90,000 h “1 may be employed at the temperatures and pressures in the preceding paragraph, in which case the process typically comprises producing said methanol at a yield of at least 4.0 gMeOH gcat "1 h "1 .
• high methanol yields may be obtained under these conditions.
• the reactant pressure may be from 300 bar to 500 bar, or for instance from 310 bar to 500 bar.
• the reactant pressure may, for instance, be from 320 bar to 500 bar, for example from 325 bar to 500 bar, or from 330 bar to 500 bar.
• the reactant pressure is from 300 bar to 400 bar, for instance from 310 bar to 380 bar, or for example from 320 bar to 360 bar, for instance from 325 bar to 350 bar, or from 330 bar to 340 bar.
• the temperature is from 250 °C to 300 °C, more preferably from 250 °C to 290 °C, still more preferably from 255 °C to 285 °C, or even more preferably from 260 °C to 280 °C.
• a space velocity of at least 5,000 h "1 is employed, in which case the process typically comprises producing said methanol at a yield of at least 1.0 gMeOH gcat "1 h “1 .
• a space velocity of at least 20,000 h “1 may be employed at the temperatures and pressures in the preceding paragraph, in which case the process typically comprises producing said methanol at a yield of at least 2.0 gMeOH gcat "1 h "1 , preferably at a yield of at least 3.0 gMeOH gcat "1 h “1 .
• a space velocity of, for instance, at least 30,000 h "1 may be employed at the temperatures and pressures in the preceding paragraph, in which case the process typically comprises producing said methanol at a yield of at least 2.8 gMeOH gcat "1 h "1 , preferably at a yield of at least 3.0 gMeOH gcat "1 h "1 .
• a space velocity of at least 50,000 h "1 may be employed at the temperatures and pressures in the preceding paragraph, in which case the process typically comprises producing said methanol at a yield of at least 4.0 gMeOH gcat "1 h “1 , or a space velocity of at least 90,000 h “1 may be employed at the temperatures and pressures in the preceding paragraph, in which case the process typically comprises producing said methanol at a yield of at least 4.5 gMeOH gcat "1 h "1 .
• the reactant pressure may for instance be from 400 bar to 500 bar, or for instance from 410 bar to 500 bar. It may be from 420 bar to 500 bar, for example from 430 bar to 500 bar, or from 440 bar to 500 bar.
• the reactant pressure may for instance be from 400 bar to 490 bar, for instance from 410 bar to 480 bar, or for example from 430 bar to 480 bar, or for example from 420 bar to 460 bar, for instance from 430 bar to 450 bar, from 435 bar to 450 bar, or from 440 bar to 450 bar.
• the temperature is from 250 °C to 300 °C, more preferably from 250 °C to 290 °C, still more preferably from 255 °C to 285 °C, or even more preferably from 260 °C to 280 °C.
• a space velocity of at least 5,000 h "1 is employed, in which case the process typically comprises producing said methanol at a yield of at least 1.0 gMeOH gcat "1 h “1 .
• a space velocity of at least 9,000 h “1 may be employed at the temperatures and pressures in the preceding paragraph, in which case the process typically comprises producing said methanol at a yield of at least 2.0 gMeOH gcat "1 h "1 , preferably at a yield of at least 3.0 gMeOH gcat "1 h “1 .
• a space velocity of, for instance, at least 20,000 h “1 may be employed at the temperatures and pressures in the preceding paragraph, in which case the process typically comprises producing said methanol at a yield of at least 3.0 gMeOH gcat "1 h “1 .
• a space velocity of at least 30,000 h “1 or at least 40,000 h “1 may be employed at the temperatures and pressures in the preceding paragraph, in which case the process typically comprises producing said methanol at a yield of at least 4.0 gMeOH gcat "1 h “1 , or for instance at a yield of at least 6.0 gMeOH gcat "1 h “1 .
• a space velocity of at least 70,000 h "1 may be employed at the temperatures and pressures in the preceding paragraph, in which case the process typically comprises producing said methanol at a yield of at least 4.5 gMeOH gcat "1 h " 1 , or for instance at a yield of at least 10.0 gMeOH gcat "1 h “1 .
• the process comprises producing said methanol at a yield of at least 1.0 gMeOH gcat "1 h “1 .
• the process may for instance comprise producing said methanol at a yield of at least 2.0 gMeOH gcat "1 h “1 , or, for instance at a yield of at least 3.0 gMeOH gcat "1 h “1 .
• the process comprises producing said methanol at a yield of at least 3.5 gMeOH gcat "1 h “1 , for instance at a yield of at least 4.0 gMeOH gcat "1 h “1 , or at a yield of at least 4.5 gMeOH gcat "1 h “1 .
• the process comprises producing said methanol at a yield of at least 6.0 gMeOH gcat "1 h “1 , for instance at a yield of at least 10.0 gMeOH gcat "1 h “1 , or at a yield of at least 15.0 gMeOH gcat "1 h “1 .
• the selectivity of the process for methanol formation is typically at least 60 %, and more typically at least 70 %.
• the selectivity of the process for methanol formation may for instance be at least 80 %, and is often at least 90 %, for instance at least 93 %, or for instance at least 95 %.
• the C0 2 conversion which is typically the conversion of CO2 per pass, is at least 40 %. Preferably, it is at least 60 %, and more preferably it is at least 70 %, or for instance at least 75 %, for example at least 80 %.
• the selectivity of the process for methanol formation is at least 80 %
• the space velocity is from 500 h “1 to 50,000 h "1
• the reactant pressure is from 320 bar to 500 bar.
• the selectivity of the process for methanol formation may for instance be at least 90 %, and the space velocity may be from 500 h "1 to 20,000 h “1 , preferably from 1,000 h “1 to 20,000 h “1 .
• the reactant pressure is from 320 bar to 450 bar.
• the selectivity of the process for methanol formation may for instance be at least 90 %, the space velocity may be from 500 h "1 to 3,000 h "1 .
• the reactant pressure is from 150 bar to 300 bar, for instance from 160 bar to 250 bar, or from 170 bar to 200 bar.
• the conversion of CO2 per pass may be at least 40 %, and the space velocity may be from 500 h “1 to 60,000 h “1 , for instance from 500 h “1 to 50,000 h “1 , or for example from 500 h “1 to 20,000 h “1 .
• the reactant pressure may be from 200 to 500 bar but is preferably from 320 to 500 bar.
• the conversion of CO2 per pass may for instance be at least 40 %, the space velocity may be from 500 h “1 to 70,000 h "1 , and the reactant pressure may be from 420 to 500 bar.
• the conversion of CO2 per pass may for instance be at least 75 %, for instance at least 80 %, the space velocity may be from 500 h "1 to 30,000 h “1 , preferably from 500 h "1 to 20,000 h “1 and the reactant pressure may be from 420 to 450 bar.
• the space velocity may be from 500 h "1 to 5,000 h "1
• the reactant pressure may be from 320 to 500 bar, for instance from 320 to 450 bar.
• the reactant pressure is from 320 to 500 bar, and preferably from 320 to 450 bar
• the space velocity is from 500 h "1 to 30,000 h "1
• the selectivity of the process for methanol formation is at least 80 %
• the conversion of C0 2 per pass is at least 40 %, and preferably at least 60%.
• the reactant pressure is from 320 to 500 bar, and preferably from 320 to 450 bar, the space velocity is from 500 h “1 to 15,000 h "1 , the selectivity of the process for methanol formation is at least 90 %, and the conversion of CO2 per pass is at least 60 %.
• the reactant pressure may for instance be from 420 to 500 bar, and is preferably from 420 to 450 bar, the space velocity may be from 500 h "1 to 15,000 h "1 , the selectivity of the process for methanol formation may be at least 90 %, and the conversion of CO2 per pass may be at least 80 %.
• the reactant pressure is from 320 to 500 bar, and preferably from 320 to 450 bar, the space velocity is at least 5,000 h "1 and the process comprises producing said methanol at a yield of at least 1.0 gMeOH gcat "1 h "1 .
• the reactant pressure may be from 320 to 500 bar, and is preferably from 320 to 450 bar
• the space velocity may be at least 10,000 h "1 , preferably at least 20,000 h "1
• the process comprises producing said methanol at a yield of at least 2.0 gMeOH gcat "1 h "1 .
• the reactant pressure may for instance be from 320 to 500 bar, and is preferably from 320 to 450 bar
• the space velocity may be at least 20,000 h "1 , preferably at least 50,000 h "1 , more preferably at least 60,000 h "1
• the process may comprise producing said methanol at a yield of at least 4.0 gMeOH gcat "1 h "1 .
• the reactant pressure may for instance be from 320 to 500 bar, and is preferably from 320 to 450 bar
• the space velocity may be at least 30,000 h "1 , preferably at least 90,000 h "1 , more preferably at least 100,000 h "1
• the process may comprise producing said methanol at a yield of at least 5.0 gMeOH gcat "1 h "1 .
• the reactant pressure is from 320 bar to 500 bar and the space velocity is from 5,000 h “1 to 110,000 h “1 , preferably from from 5,000 h “1 to 30,000 h “1 .
• the selectivity of the process for methanol formation is at least 80 %, the conversion of CO2 per pass is at least 40 %, and the process comprises producing said methanol at a yield of at least 1.0 gMeOH gcat "1 h "1 .
• the reactant pressure is from 320 bar to 500 bar and the space velocity is from 5,000 h “1 to 110,000 h “1 , preferably from from 5,000 h “1 to 40,000 h “1 , more preferably from from 20,000 h “1 to 40,000 h “1 .
• the selectivity of the process for methanol formation is at least 85 %
• the conversion of C0 2 per pass is at least 45 %
• the process comprises producing said methanol at a yield of at least 1.5 gMeOH gcat "1 h "1 .
• the reactant pressure is from 320 bar to 500 bar and the space velocity is from 5,000 h “1 to 110,000 h “1 , preferably from from 5,000 h “1 to 40,000 h “1 , more preferably from from 20,000 h “1 to 40,000 h “1 .
• the selectivity of the process for methanol formation is at least 95 %, the conversion of
• CO2 per pass is at least 75 %, and the process comprises producing said methanol at a yield of at least 2.0 gMeOH gcat "1 h "1 .
• the reactant pressure is from 150 to 250 bar, and the space velocity is at least 50,000 h "1 and, preferably, the process comprises producing said methanol at a yield of at least 3.0 gMeOH gcat "1 h "1 .
• the reactant pressure is from 150 to 250 bar, and the space velocity is at least 30,000 h "1 and, preferably, the process comprises producing said methanol at a yield of at least 2.0 gMeOH gcat "1 h "1 .
• the present inventors have found that remarkable further improvements can be achieved by ensuring that a high proportion of the active sites of the catalyst are present in a portion of the catalyst that is accessible to the H 2 and the C0 2 reactants.
• the portion of the catalyst that is accessible to the reactants is known as the "accessible diffusion layer" of the catalyst.
• the inventors have found that, under the conditions of the process of the invention, and especially at the higher pressures when gases tend to liquefy, the reactants need to diffuse between the catalyst particles to access the catalyst active sites.
• the accessible diffusion layer of the catalyst is not large enough, part of the catalyst is not taking part in the process and this can result in lower yields (as expressed in grams of methanol produced per gram of catalyst per hour).
• the inventors have found that this situation can be improved by increasing the proportion of the active sites of the catalyst that belong to the accessible diffusion layer. There are several ways in which this may be achieved, including, but not limited to, lowering the size of the catalyst particle, engineering the catalyst, or supporting the catalyst on a catalyst support, such as on a membrane or other type of support.
• the proportion of the active sites of the catalyst that belong to the accessible diffusion layer may be expressed as a percentage, and it is preferred that, for instance, at least 70% of the active sites of the catalyst belong to the accessible diffusion layer.
• the portion of the catalyst that is accessible to said H 2 and said C0 2 comprises at least 70% of the active sites of the catalyst. More preferably, the portion of the catalyst that is accessible to said H 2 and said C0 2 comprises at least 80% of the active sites of the catalyst. Even more preferably, the portion of the catalyst that is accessible to said H 2 and said C0 2 comprises at least 90% of the active sites of the catalyst, for instance at least 95% of the active sites of the catalyst, at least 98% of the active sites of the catalyst, or for example at least 99% of the active sites of the catalyst. Most preferably, the portion of the catalyst that is accessible to said H 2 and said C0 2 comprises all, or substantially all (e.g. greater then 99.5%, or greater than 99.9%), of the active sites of the catalyst.
• particle size means the diameter of the particle if the particle is spherical or, if the particle is non-spherical, the volume-based particle size.
• the volume- based particle size is the diameter of the sphere that has the same volume as the non- spherical particle in question.
• the catalyst employed in the present invention often has a particle size of from about 80 ⁇ to about 320 ⁇ , for instance from about 100 ⁇ to about 300 ⁇ .
• the present inventors have found that remarkable further improvements can be achieved when the catalyst has an even smaller particle size than this, in order to increase the proportion of the active sites of the catalyst that belong to the accessible diffusion layer.
• Such further improvements have been observed for instance when a catalyst particle size of less than 80 ⁇ is employed, and in particular when a particle size of equal to or less than 50 ⁇ is employed, for instance a particle size of equal to or less than 30 ⁇ , or for example a particle size of equal to or less than 20 ⁇ .
• the catalyst employed in the process of the invention has a particle size of equal to or less than 50 ⁇ , for instance, a particle size of equal to or less than 30 ⁇ , such as, for example a particle size of less than or equal to 20 ⁇ .
• the particle size of the catalyst in these embodiments may for instance be from 5 ⁇ to 80 ⁇ , or for instance from 5 ⁇ to 50 ⁇ , such as, for example, from 10 ⁇ to 30 ⁇ , or for instance from 10 ⁇ to 25 ⁇ .
• the following further preferences and embodiments are particularly applicable to the use of catalysts in which a high proportion of the active sites of the catalyst are present in the portion of the catalyst that is accessible to the 3 ⁇ 4 and the C0 2 reactants (i.e. in the "accessible diffusion layer").
• the following preferences and embodiments are therefore particularly applicable to the use of catalysts which have small catalyst particle sizes, in the present invention, e.g. catalysts with a particle size of less than 80 ⁇ .
• the selectivity of the process for methanol formation is at least 80 %, preferably at least 90 %
• the space velocity is from 500 h "1 to 110,000 h “1 , and preferably from 500 h "1 to 70,000 h “1 ;
• the reactant pressure is preferably from 320 bar to 500 bar, more preferably from 320 bar to 450 bar, or from 420 to 500 bar, for instance from 420 to 450 bar.
• the conversion of CO2 per pass is at least 40 %, preferably at least 75 %; the space velocity is from 500 h "1 to 110,000 h “1 , preferably from 500 h "1 to 40,000 h “1 ; and the reactant pressure is from 320 to 500 bar, preferably from 420 to 500 bar, more preferably from 420 to 450 bar.
• the reactant pressure is from 320 to 500 bar, preferably from
• the space velocity is from 500 h "1 to 110,000 h “1 , preferably from 500 h "1 to 40,000 h “1 , the selectivity of the process for methanol formation is at least 80 %, and the conversion of CO2 per pass is at least 40 %.
• the reactant pressure may be from 320 to 500 bar, preferably from 320 to 450 bar
• the space velocity may be from 500 h "1 to 15,000 h "1
• the selectivity of the process for methanol formation may be at least 90 %
• the conversion of CO2 per pass may be at least 60 %.
• the reactant pressure may for instance be from 420 to 500 bar, preferably from 420 to 450 bar, the space velocity may be from 500 h "1 to 40,000 h “1 , preferably from 500 h "1 to 15,000 h “1 , the selectivity of the process for methanol formation is at least 90 %, and the conversion of CO2 per pass is at least 80 %.
• the reactant pressure is from 320 to 500 bar, preferably from 320 to 450 bar
• the space velocity is at least 5,000 h "1
• the process comprises producing said methanol at a yield of at least 1.5 gMeOH gcat h , more preferably at a yield of at least
• the reactant pressure may be from 320 to 500 bar, preferably from 320 to 450 bar
• the space velocity may be at least 20,000 h "1
• the process may comprise producing said methanol at a yield of at least 3.0 gMeOH gcat "1 h "1 , more preferably at a yield of at least 6.0 gMeOH gcat "1 h “1 .
• the reactant pressure may for example be from 320 to 500 bar, preferably from 320 to 450 bar, the space velocity may be at least 50,000 h "1 , preferably at least 60,000 h "1 , and the process may comprise producing said methanol at a yield of at least 4.0 gMeOH gcat "1 h "1 , and preferably at a yield of at least 10.0 gMeOH gcat "1 h "1 .
• the reactant pressure is from 320 to 500 bar, preferably from 320 to 450 bar
• the space velocity is at least 90,000 h "1 , preferably at least 100,000 h "1
• the process comprises producing said methanol at a yield of at least 5.0 gMeOH gcat "1 h "1 , and preferably at a yield of at least 15.0 gMeOH gcat "1 h “1 .
• the reactant pressure is from 320 bar to 500 bar; and the space velocity is from 5,000 h "1 to 40,000 h “1 , preferably from 20,000 h “1 to 40,000 h “1 ; and preferably: the selectivity of the process for methanol formation is at least 85 %, the conversion of C0 2 per pass is at least 45 %, and the process comprises producing said methanol at a yield of at least 1.5 gMeOH gcat "1 h "1 , and preferably at a yield of at least 3.0 gMeOH gcat "1 h "1 ; or
• the reactant pressure is from 420 bar to 500 bar; and the space velocity is from 5,000 h “1 to 40,000 h “1 , preferably from 20,000 h “1 to 40,000 h “1 ; and preferably: the selectivity of the process for methanol formation is at least 95 %, the conversion of CO2 per pass is at least 75 %, and the process comprises producing said methanol at a yield of at least 2.0 gMeOH gcat "1 h "1 , and preferably at a yield of at least
• a continuous flow, high-pressure fixed-bed reactor was used to study the hydrogenation of C0 2 to methanol.
• the reactor made of stainless steel was in a tubular shape with outer diameter of 1/8" or 1/4" with inner diameter of 0.07" or 0.12", respectively.
• the details of high-pressure fixed-bed reactor and analytical systems are described in A. Bansode, B. Tidona, P.R. von Rohr, A. Urakawa, Catal. Sci. Technol., 3 (2013) 767-778.
• a high-pressure syringe pump (Teledyne ISCO 260D) was used to dispense the premixed reactant gases to precisely control the CO2 to H 2 molar ratio.
• GHSV 650 h "1
• the 1/4" reactor tube with 1.0 g of the catalyst was used, while for higher GHSV conditions (2,000-8,000 h "1 and 10,000-100,000 h "1 ) the 1/8" reactor tube with 400 and 50 mg of the catalyst was used.
• Table 1 shows (i) the composition of the as-purchased commercial methanol synthesis catalyst (Cu/ZnO/Ab03, Alfa Aesa Product No.: 45776), (ii) the copper surface area (Scu) of the catalyst after reduction pretreatment, and (iii) the average crystallite size of the CuO in the catalyst.
• the Cu surface area (Scu) was determined by N2O pulse chemisorption (A. Bansode, A. Urakawa, J. Catal., 309 (2014) 66-70) using the method previously reported in J.W. Evans et al., Applied Catalysis, Vol. 7, 1, 1983, p 75-83.
• Table 1 Elemental composition, Cu surface area and average
• GHSV is defined by the volumetric flow rate of inlet stream at normal pressure divided by the reactor volume where the catalyst is packed (including the catalyst volume). A wide range of GHSV conditions (650-100,000 h "1 ) were examined. GHSV is also shown in catalyst-mass-normalized unit, in which the value ranges from 0.37 to 49.85 NL gcat "1 h "1 . For the GHSV calculation in both units, the total flow rate at normal pressure including Ar was used. The vaporized outlet stream were injected to GC every ca. 12 min for 3 h at each condition of temperature, pressure and GHSV and an averaged value was taken. No catalyst deactivation was detected for the duration of catalytic tests performed.
• thermodynamic calculations were performed using Aspen HYSYS V8.6 simulation tool using the Soave Redlich Kwong (SRK) equation of state (EOS) with modified binary interaction parameters for CO, CO2, 3 ⁇ 4, methanol and water being taken from the optimized values reported by van Bennekom et al. for methanol synthesis (J.G. van Bennekom, J.G.M. Winkelman, R.H. Venderbosch, S.D.G.B. Nieland, H.J. Heeres, Ind. Eng. Chem. Res., 51 (2012) 12233-12243). The calculations were performed by minimization of Gibbs free energy. Methane was not considered in all calculations.
• Figure 4 depicts the equilibrium conversion of CO2
• Figure 5 depicts the equilibrium selectivity of methanol at 46, 92, 184, 331, 442 bar and temperature range of 150 to 340 °C. Results and discussion
• thermodynamic calculations ( Figure 1, dotted lines).
• CO2 conversion varies between 25-30% with rapidly decreasing methanol selectivity from ca. 90 to 20% in the temperature window of 220-300 °C.
• C0 2 conversion varies from roughly 50% (220 °C) to 30% (300 °C) with very good to moderate methanol selectivity (96.5% at 220 °C and
• the pre-calcined coprecipitated catalyst is mainly formed by zincian malachite and aurichalcite. After calcination, the decomposition of the hydroxycarbonates took place, leaving only CuO and ZnO in the catalyst. The crystallite size of both oxides is around 7 nm as determined by XRD. After reduction (25 mL/min of 10% H 2 /90% N 2 at 300 °C for 2 h), the Cu surface area of the resulting material was 23 m 2 /g (Table 10).
• the methanol weight-time yield (WTY) was above 1.2 gMeOH gcat "1 h "1 with 52% C0 2 conversion and 84% methanol selectivity at 331 bar at 280 °C.
• the same level of WTY (above 1.2 gMeOH gcat "1 h "1 ) was also obtained at 442 bar at 300 °C with 56% C0 2 conversion and 92% methanol selectivity.

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