PRODUCTION OF ETHANOL FROM CARBON DIOXIDE AND HYDROGEN

Abstract

Processes for producing alcohols are described. The processes involve contacting a reactant feed that includes a first alcohol with a metal oxalate salt and a Cu-based catalyst under conditions sufficient to produce a product composition that includes a second alcohol. The second alcohol has a higher carbon number than the first alcohol.

Claims

1. A process for producing an alcohol, the process comprising contacting a metal oxalate salt with a first alcohol in the presence of a copper (Cu)-based catalyst under conditions sufficient to produce a composition comprising a second alcohol having an increased carbon number relative to the first alcohol.

2. The process of claim 1, wherein the first alcohol is methanol and the second alcohol is ethanol.

3. The process of claim 1, wherein contacting is performed in a carbon dioxide (CO.sub.2) and hydrogen (H.sub.2) atmosphere.

4. The process of claim 1, wherein the Cu-based catalyst comprises nickel (Ni).

5. The process of claim 4, wherein the Cu-based catalyst is a supported Cu-Ni material.

6. The process of claim 1, wherein the metal oxalate salt to first alcohol molar ratio is 1 to 5.

7. The process of claim 1, wherein the reaction conditions comprise a temperature of 200 C. to 250 C.

8. The process of claim 1, wherein the metal oxalate salt comprises cesium (Cs).

9. The process of claim 8, wherein the metal oxalate salt is cesium oxalate (Cs.sub.2C.sub.2O.sub.4).

10. The process of claim 9, wherein the cesium oxalate is obtained by contacting CO.sub.2 and H.sub.2 with cesium carbonate (Cs.sub.2CO.sub.3) under reaction conditions sufficient to form the Cs.sub.2C.sub.2O.sub.4.

11. The process of claim 9, wherein the reaction conditions comprise a temperature of 250 C. to 400 C.

12. The process of claim 9, a CO.sub.2 pressure of 1 MPa to 5 MPa and a H.sub.2 pressure of 0.05 to 0.5 MPa.

13. The process of claim 8, wherein the mole ratio of CO.sub.2 and H.sub.2 to Cs.sub.2CO.sub.3 is 100:1 to 300:1.

14. The process of claim 1, further comprising the step of contacting a Cu-based catalyst precursor with gaseous hydrogen (H.sub.2) under conditions sufficient to reduce the Cu-based catalyst precursor and form the Cu-based catalyst prior to contacting the Cu-based catalyst with the first alcohol.

15. The process of claim 14, wherein the conditions comprise a temperature of 250 C. to 280 C.

16. The process of claim 1, wherein the composition further comprises a diol.

17. The process of claim 16, wherein the diol is ethylene glycol.

18. The process of claim 16, wherein a mole ratio of second alcohol to diol is 10:1 to 20:1.

19. The process of claim 1, wherein the selectivity to the second alcohol is at least 10%.

20. The process of claim 1, wherein a molar ratio of the first alcohol to the Cu in the Cu-based catalyst is 200:1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Advantages of the present invention may become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings.

[0025] FIG. 1 is a schematic of a system to perform the process of the present invention to produce a higher carbon number alcohol (e.g., ethanol) from a lower number alcohol (e.g., methanol) and a metal oxalate salt (e.g., cesium oxalate).

[0026] FIG. 2 is a schematic of a process and system to produce metal oxalates.

[0027] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings. The drawings may not be to scale.

DETAILED DESCRIPTION OF THE INVENTION

[0028] A discovery has been made that provides an elegant solution to the problem of production of ethanol from alternative feed stocks. The discovery is premised on contacting a metal oxalate, Cu-based catalyst, and a first alcohol to produce a second alcohol (e.g., ethanol). The reaction mixture, which includes a first alcohol (e.g., methanol) and carbon dioxide (CO.sub.2) can be contacted with a metal oxalate salt (e.g., cesium oxalate) under reaction conditions sufficient to produce an alcohol (e.g., ethanol) containing composition as shown in overall general reaction equation (1).

##STR00001##

where M is metal cation and R.sup.1 and R.sup.2 are aliphatic or aromatic groups and R.sup.2 is at least one carbon number higher than R.sup.1. In some instances, the cesium salt is cesium oxalate, R.sup.1OH is methanol and R.sup.2OH is ethanol. These and other non-limiting aspects of the present invention are discussed in further detail in the following sections with reference to the Figures.

A. System and Processes to Prepare Alcohols

[0029] Referring to FIG. 1, a method and system to prepare alcohols (e.g., ethanol) is described. In system 100, a known amount of Cu-based catalyst (e.g., Cu-Ni) 102 can be positioned in reaction unit 104. The Cu-based catalyst can be activated by heating the catalyst under a hydrogen atmosphere. For example, a H.sub.2-containing stream can enter reaction unit 104 via gaseous inlet 106 until the reaction unit is pressurized of 0.2 to 1 MPa, or 0.3 to 0.8 MPa, or at least any one of, equal to any one of, or between any two of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1 MPa. Pressurized reaction unit 104 can be heated to a temperature of 250 C. to 300 C., or at least any one of, equal to any one of, or between any two of 250 C., 255 C., 260 C., 265 C., 270 C., 275 C., 280 C., 285 C., 290 C., 295 C., and 300 C. until the catalyst is reduced (e.g., for 1 to 24 hours, 2 to 10 hours, 3 to 8 hours or any range or value there between. After reducing the catalyst, the heating can be stopped and the reaction unit 204 and the catalyst can be cooled to ambient temperature (e.g., 20 C. to 40 C.).

[0030] The desired alcohol (e.g., methanol) and metal oxalate (e.g., cesium oxalate) be added to reaction unit 104. The molar ratio of the metal oxalate salt to first alcohol can be 1 to 5, or 1, 2, 3, 4, and 5 or any range or value there between. In a preferred embodiment, the molar ratio is 3. The oxalate salt can be made as described throughout the Specification and/or be purchased from a commercial source. The desired alcohol (e.g., methanol) can be added to reaction unit 104 via liquid inlet 108 to form a composition that includes a metal oxalate salt (e.g., cesium oxalate), an alcohol. CO.sub.2 and H.sub.2 can be added through gaseous inlet 106. The reactor can be pressurized with CO.sub.2 and H.sub.2 to a pressure ranging from 2 MPa to 5 MPa, 3 MPa to 4 MPa, and all ranges and pressures there between (e.g., 2.1 MPa, 2.2 MPa, 2.3 MPa, 2.4 MPa, 2.5 MPa, 2.6 MPa, 2.7 MPa, 2.8 MPa, 2.9 MPa, 3 MPa, 3.1 MPa, 3.2 MPa, 3.3 MPa, 3.4 MPa, 3.5 MPa, 3.6 MPa, 3.7 MPa, 3.8 MPa, 3.9 MPa, 4.0 MPa, 4.1 MPa, 4.2 MPa, 4.3 MPa, 4.4 MPa, 4.5 MPa, 4.6 MPa, 4.7 MPa, 4.8 MPa, or 4.9 MPa). In some embodiments, CO.sub.2 and H.sub.2 are added separately. CO.sub.2 and/or H.sub.2 can be provided to reaction unit 102 at a pressure ranging from 1 MPa to 4 MPa and all ranges and pressures there between (e.g., 1.1 MPa, 1.2 MPa, 1.3 MPa, 1.4 MPa, 1.5 MPa, 1.6 MPa, 1.7 MPa, 1.8 MPa, 1.9 MPa, 2 MPa, 2.1 MPa, 2.2 MPa, 2.3 MPa, 2.4 MPa, 2.5 MPa, 2.6 MPa, 2.7 MPa, 2.8 MPa, 2.9 MPa, 3.0 MPa, 3.1 MPa, 3.2 MPa, 3.3 MPa, 3.4 MPa, 3.5 MPa, 3.6 MPa, 3.7 MPa, 3.8 MPa, 3.9 MPa, or 4 MPa). Preferably, the CO.sub.2 pressure is about 2.5 MPa to 3.5 MPa.

[0031] After the addition of the alcohol, H.sub.2, and CO.sub.2 to the reduced catalyst, reaction unit 104 can be heated to a reaction temperature sufficient to promote the metal oxalate salt to react with the alcohol under the CO.sub.2/H.sub.2 atmosphere to produce a second alcohol (e.g., ethanol) containing composition having an increased carbon number from the first alcohol (e.g., (methanol). The reaction temperature can be 115 C. to 200 C., 130 C. to 180 C., or at least, equal to, or between any two of 115 C., 120 C., 125 C., 130 C., 135 C., 140 C., 145 C., 150 C., 155 C., 160 C., 165 C., 170 C., 175 C., 180 C., 185 C., 190 C., 195 C. and 200 C. Preferably, the reaction temperature is about 130 C. Reaction unit 104, and, thus the reaction mixture, can be heated for a time sufficient to react all or substantially all of the metal oxalate salt (e.g., cesium oxalate). By way of example, the reaction time range can be at least 1 hour, 1 hours to 18 hours, 10 hour to 14 hours, 1 to 6 hours or 1 to 2 hours, and all ranges and times there between (e.g., 2 hours, 5 hours, 8 hours, 10 hours, 15 hours, or 17 hours). Preferably, the reaction time is 1 to 18 hours, or 15 hours. The upper limit on temperature, pressure, and/or time can be determined by the reactor used. The reaction temperature can be varied depending on the type of Cu-based catalyst used.

[0032] Reaction unit 104 can be cooled and depressurized to a temperature and pressure sufficient (e.g., below 50 C. at 0.101 MPa) to allow removal of the product composition containing the desired alcohol (e.g., ethanol) via product outlet 110. The product composition can be collected for further use. In some instances, the product composition can include diols (e.g., ethylene glycol) in addition to the desired alcohol.

B. Products

[0033] The process of the present invention can produce a product stream that includes a composition containing an alcohol, preferably ethanol, that can be suitable as an intermediate or as feed material in a subsequent synthesis reactions to form a chemical product or a plurality of chemical products (e.g., such as in pharmaceutical products, for the production of oxalic acid and ethylene glycol, or as a solvent or plasticizer). In some instances, the composition includes ethylene glycol. The product composition includes at least 10 wt. %, at least 20 wt. %, at least 30 wt. %, at least 40 wt. %, at least 50 wt. %, at least 60 wt. %, at least 70 wt. %, at least 80 wt. %, at least 90 wt. % or 100 wt. % alcohol with the balance being by-products such as the reactant alcohol (e.g., methanol) and/or a metal bicarbonate (e.g., cesium bicarbonate). A molar ratio of alcohol to diol can be 10:1 to 20:1, or at least any one of, equal to any one of, or between any two of 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, and 20:1. The product composition can be purified using known organic purification methods (e.g., extraction, crystallization, distillation, washing, etc.) depending on the phase of the production composition (e.g., liquid or dispersion). In a preferred embodiment, the ethanol can be distilled from the product mixture. Alcohols that can be produced by this method include ethanol, propanol, butanol, pentanol, etc.

C. Materials

1. Cesium Salts and Cesium Oxalate

[0034] Cesium salts (e.g., carbonate (Cs.sub.2CO.sub.3)) may be purchased in various grades from commercial sources. Preferably, the cesium salt (Cs.sub.2CO.sub.3) is highly pure and substantially devoid of water. A non-limited commercial source of the cesium salts for use in the present invention includes SigmaMillipore (USA). In some embodiments, Cs.sub.2CO.sub.3 is mixed with an inert material. Non-limiting examples of inert materials include alumina (acidic, basic or neutral), silica, zirconia, ceria, zeolites, lanthanum oxides, or mixtures thereof. In preferred embodiments, the Cs.sub.2CO.sub.3 is mixed with alumina or silica using solid-solid mixing. Providing the Cs.sub.2CO.sub.3 as a Cs.sub.2CO.sub.3/inert material mixture can inhibit the cesium oxalate from forming a melt that requires further processing (e.g., grinding, powdering, etc.) prior to reaction with alcohol to form the disubstituted oxalate of the present invention.

[0035] Cesium oxalate can be purchased or prepared as described herein. Cesium oxalate production can be produced in the context of the present invention by contacting a mixture of inert material and a cesium salt (e.g., Cs.sub.2CO.sub.3 and/or CsHCO.sub.3) with an oxygen source and a carbon source under reaction conditions sufficient to form a composition that includes Cs.sub.2C.sub.2O.sub.4. The composition can also include cesium formate (HCO.sub.2Cs) or cesium bicarbonate (CsHCO.sub.3). Formation of a cesium oxalate in the presence of an inert material can inhibit the cesium oxalate from forming a melt that requires further processing (e.g., grinding, powdering, etc.) prior to reaction with other reagents to form various products (e.g., ethanol) especially when the cesium oxalate is generated in situ. The inert material can be any material that does not promote reactions between the gaseous carbon source and the gaseous oxygen source. In some embodiments, the inert material can include at least one metal oxide, charcoal, or a mixture thereof. Non-limiting examples of metal oxides include alumina (acidic, basic, gamma, or neutral), ceria, silica, zirconia, lanthanum oxides, zeolites, or mixtures thereof. In one non-limiting embodiment, alumina and/or silica is used as the inert material. In one particular embodiment, gamma alumina is used as the inert material. In another embodiment, alumina and/or silica is combined with charcoal, and the mixture is used as the inert material. The mass ratio of charcoal to metal oxide can be 0.1:10 to 10:0.1, or 0.2:8, 1:5, 1:1, 2:1, or 3:0.2, preferably 1:1. A mass ratio of inert material to the cesium salt can be 0.1:10 to 10:0.1, or 0.2:8, 0.5:5, 1:1, 2:1, 5:0.2, or 8:0.5. In one non-limiting embodiment, the mass ratio of inert material to the cesium salt can be 1:1, or 0.5:1. In some embodiments, the inert material (e.g., gamma alumina) is added to the cesium carbonate or bicarbonate in the presence of water and mixed under agitation to form a dispersion, slurry, mull, or wet powder of inert material and cesium salt. The water can be removed under vacuum and the resulting powder dried under vacuum at a temperature of 250to 325 C. for 10 minutes to 5 hours, or 15 minutes to 2 hours.

[0036] Conventionally, cesium oxalate is generated by the reaction of cesium carbonate with carbon monoxide and carbon dioxide as shown in reaction equation (2).

Cs.sub.2CO.sub.3+CO+CO.sub.2.fwdarw.Cs.sub.2(C.sub.2O.sub.4) (2).

[0037] In one alternative process, the cesium oxalate can be generated by the reaction of cesium carbonate with carbon dioxide and H.sub.2 as shown in reaction equation (3) as described in more detail below.

Cs.sub.2CO.sub.3+H.sub.2+CO.sub.2.fwdarw.Cs.sub.2(C.sub.2O.sub.4) (3).

In some embodiments, the carbon dioxide and H.sub.2 are added in a sequential manner as shown in reaction equation (4). The sequential addition of carbon dioxide then hydrogen can inhibit or substantially inhibit the formation of cesium formate (HCO.sub.2Cs). Limiting the formation of cesium formate limits the formation of alkyl formate in subsequent reactions with alcohols. In some instances, cesium formate is not formed in the production of cesium oxalate.

##STR00002##

[0038] In yet another alternative process, the cesium oxalate can be generated by the reaction of cesium carbonate with carbon monoxide and O.sub.2 as shown in reaction equation (5) as described in more detail below.

Cs.sub.2CO.sub.3+O.sub.2+CO .fwdarw.Cs.sub.2(C.sub.2O.sub.4) (5).

While the above reactions show Cs.sub.2CO.sub.3, the reactions are the same when an inert material is used. With respect to reaction equation (5), and without wishing to be bound by theory, it is believed that the use of molecular oxygen can require lower heat requirements when compared to other processes as the reaction between CO and O.sub.2 is exothermic (free energy change of 61.4 kcal/mol as determined through density functional theory (DFT)). In another embodiment, the oxalate salt (e.g., cesium oxalate) can be produced from oxalic acid and a metal hydroxide (e.g., cesium hydroxide). By way of example, oxalic acid can be mixed with water or another solvent until dissolved. Two molar equivalents of cesium hydroxide can be added to the acidic solution of oxalic acid until full neutralization is achieved (e.g., pH of 6.8 to 7.2). Either the amount of the acid or the base can be in slight excess to ensure completion of neutralization. After the completion of the neutralization, the reaction solution can be concentrated (e.g., vacuum distilled, evaporated) to remove the solvent (e.g., water), and a product can be collected that includes cesium oxalate. In some embodiments, the solution can be concentrated to remove a majority of the solvent (e.g., about 90 to 95 vol. % of the water) and the solution can be cooled to promote crystallization of the cesium oxalate from the solvent. The cesium oxalate can then be isolated (e.g., filtered, centrifuged) and washed thoroughly with ethanol.

[0039] Referring to FIG. 2, a method and system to prepare oxalate salts is described. In system 200, a cesium salt precursor (e.g., cesium carbonate (Cs.sub.2CO.sub.3)) and optional inert material can be provided to a reactor unit 202 via solids inlet 204. CO, CO.sub.2, O.sub.2, or H.sub.2, or any combination thereof can be provided to reactor 202 via gas inlets 206 and 208. By way of example, CO.sub.2 can be provided to reactor 202 via gas inlet 208 and CO or H.sub.2, can be provided to the reactor via gas inlet 206. CO can be provided to reactor 202 via gas inlet 206 and O.sub.2 can be provided to the reactor via gas inlet 208. In embodiments when carbon monoxide is used, the CO can be provided to reactor 202 at a pressure ranging from 1 MPa to 3 MPa and all ranges and pressures there between (e.g., 1.1 MPa, 1.2 MPa, 1.3 MPa, 1.4 MPa, 1.5 MPa, 1.6 MPa, 1.7 MPa, 1.8 MPa, 1.9 MPa, 2 MPa, 2.1 MPa, 2.2 MPa, 2.3 MPa, 2.4 MPa, 2.5 MPa, 2.6 MPa, 2.7 MPa, 2.8 MPa, or 2.9 MPa). Preferably, the CO pressure is about 2 MPa. In other embodiments when H.sub.2 is used, the H.sub.2 can be provided to reactor 202 at a pressure ranging from 0.05 MPa to 0.5 MPa, 0.05 to 0.4 MPa, 0.05 to 0.3 MPa, 0.05 to 0.2 MPa, or 0.05 to 0.1 and all ranges and pressures there between (e.g., 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa, 0.1 MPa, 0.11 MPa, 0.12 MPa, 0.13 MPa, 0.14 MPa, 0.15 MPa, 0.16 MPa, 0.17 MPa, 0.18 MPa, 0.19 MPa, 0.20 MPa, 0.21 MPa, 0.22 MPa, 0.23 MPa, 0.24 MPa, 0.25 MPa, 0.26 MPa, 0.27 MPa, 0.28 MPa, 0.29 MPa, 0.30 MPa, 0.31 MPa, 0.32 MPa, 0.33 MPa, 0.34 MPa, 0.35 MPa, 0.36 MPa, 0.37 MPa, 0.38 MPa, 0.39 MPa, 0.40 MPa, 0.41 MPa, 0.42 MPa, 0.43 MPa, 0.44 MPa, 0.45 MPa, 0.46 MPa, 0.47 MPa, 0.48 MPa, 0.49 MPa, or 0.50 MPa). Preferably, the H.sub.2 pressure is about 0.1 MPa. In other embodiments when O.sub.2 is used, the O.sub.2 can be provided to reactor 202 at a pressure ranging from 0.05 MPa to 4 MPa, 0.1 to 1.5 MPa, or about 0.1 MPa. CO.sub.2 can be provided to reactor 202 at a pressure ranging from 1 MPa to 4 MPa and all ranges and pressures there between (e.g., 1 MPa, 1.1 MPa, 1.2 MPa, 1.3 MPa, 1.4 MPa, 1.5 MPa, 1.6 MPa, 1.7 MPa, 1.8 MPa, 1.9 MPa, 2 MPa, 2.1 MPa, 2.2 MPa, 2.3 MPa, 2.4 MPa, 2.5 MPa, 2.6 MPa, 2.7 MPa, 2.8 MPa, 2.9 MPa, 3.0 MPa, 3.1 MPa, 3.2 MPa, 3.3 MPa, 3.4 MPa, 3.5 MPa, 3.6 MPa, 3.7 MPa, 3.8 MPa, 3.9 MPa, or 4 MPa). Preferably, the CO.sub.2 pressure is about 2.5 MPa to 3.5 MPa. The upper limit on pressure can be determined by the type and size of reactor used. Although not shown, in some embodiments, CO.sub.2CO, O.sub.2, or H.sub.2, and can be provided to reactor unit 202 via the same inlet. In certain embodiments, mixtures of CO.sub.2, CO, O.sub.2, and H.sub.2 are used. By way of example, CO.sub.2 can be used with CO, CO.sub.2 can be used with H.sub.2, CO, or CO and H.sub.2, and CO can be used with O.sub.2. Reactor 202 can be pressurized either through the addition of the gases and/or with an inert gas. The average pressure of reactor unit 202 can range from 2.0 to 4 MPa (e.g., 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9 MPa) after charging the CO.sub.2. Reactor 202 can be heated to a temperature sufficient to promote the reaction of cesium carbonate with the carbon dioxide and carbon monoxide or H.sub.2 to produce a product composition that includes cesium oxalate. The temperature range of the reactor 202 can be 200 C. to 400 C., 250 C. to 350 C., and all ranges and temperatures there between (e.g., 205 C., 210 C., 215 C., 220 C., 225 C., 230 C., 235 C., 240 C., 245 C., 250 C., 255 C., 260 C., 265 C., 270 C., 275 C., 280 C., 285 C., 290 C., 295 C., 300 C., 30520 C., 310 C., 315 C., 320 C., 325 C., 330 C., 335 C., 340 C., 345 C., 350 C., 355 C., 360 C., 365 C., 370 C., 375 C., 380 C., 385 C., 390 C., or 395 C.). Preferably, the reaction temperature is 290 C. to 335 C., or most preferably 300 C. to 325 C. The reactants can be heated for a time sufficient to react all or a substantially all of the cesium carbonate. By way of example, the reaction time range can be at least 1 hour, 1 to 5 hours, 1 hours to 4 hours, 1 hour to 3 hours, and all ranges and times there between (e.g., 1.25 hours, 1.5 hours, 1.75 hours, 2 hour, 2.25 hours, 2.5 hours, 2.75 hours, 3 hours, 3.25 hours, 3.5 hours, 3.75 hours, 4 hours, 4.25 hours, 4.5 hours, 4.75 hours, 5 hours). When CO is used, the reaction time can be about 2 hours. When H.sub.2 is used, the cesium carbonate can be reacted with the carbon dioxide for 1 to 3 hours, (e.g., 1, 1.5, 2, 2.5, 3 hours), and then with H.sub.2 for an additional 1 to 3 hours, (e.g., 1, 1.5, 2, 2.5, 3 hours). The metal oxalate (e.g., cesium oxalate) can be removed via solids outlet 210.

2. Alcohols

[0040] Alcohols may be purchased in various grades from commercial sources. Preferably the alcohol is devoid of, or includes a minimal amount, of water. Non-limiting examples of the alcohol that can be used in the process of the current invention to form a higher carbon number alcohol can include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 3-methyl-1-butanol, 2-methyl-b 1-butanol, 2,2-dimethyl -1-propanol, 3-methyl-2-butanol, 2-methyl-2-butanol, 1-hexanol, 2-hexanol, 3-hexanol, 1-heptanol, 2-heptanol, 3-heptanol, 4-heptanol, 1-octanol, 2-octanol, 3-octanol, 4-octanol, cyclohexanol, cyclopentanol, phenol, benzyl alcohol, ethylene glycol, propylene glycol, or butylene glycol or any combination thereof. Preferably, the alcohol is methanol.

3. Gases

[0041] CO.sub.2 gas, CO gas, O.sub.2 gas, and H.sub.2 gas can be obtained from various sources. In one non-limiting instance, the CO.sub.2 can be obtained from a waste or recycle gas stream (e.g., from a plant on the same site such as from ammonia synthesis, or a reverse water gas shift reaction) and/or after recovering the carbon dioxide from a gas stream. A benefit of recycling carbon dioxide as a starting material in the process of the invention is that it can reduce the amount of carbon dioxide emitted to the atmosphere (e.g., from a chemical production site). The CO can be obtained from various sources, including streams coming from other chemical processes, like partial oxidation of carbon-containing compounds, iron smelting, photochemical process, syngas production, reforming reactions, and/or various forms of combustion. O.sub.2 can come from various sources, including streams from water-splitting reactions and/or cryogenic separation systems. The hydrogen may be from various sources, including streams coming from other chemical processes, like water splitting (e.g., photocatalysis, electrolysis, or the like), syngas production, ethane cracking, methanol synthesis, and/or conversion of methane to aromatics. In some embodiments, the gases are obtained from commercial gas suppliers. In some examples, the remainder of the reactant gas can include another gas or gases provided the gas or gases are inert, such as argon (Ar) and/or nitrogen (N.sub.2), further provided that they do not negatively affect the reaction. Preferably, the reactant mixture is highly pure and substantially devoid of water. In some embodiments, the gases can be dried prior to use (e.g., pass through a drying media) or contain a minimal amount of water or no water at all. Water can be removed from the reactant gases with any suitable method known in the art (e.g., condensation, liquid/gas separation, etc.).

4. Cu-Based Catalysts

[0042] The catalyst can be any copper-based catalyst. The Cu-based catalyst can include a second transition metal (e.g., Columns 6-12 of the Periodic Table) and an optional promoter metal from Columns 1 and 2 of the Periodic Table. Non-limiting examples of transition metals include chromium, molybdenum, tungsten, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, silver, gold, zinc, or a combination thereof. In one instance, the catalyst is a Cu-nickel (Ni) alloy. In some embodiments, the catalyst can be supported. Non-limiting examples of support material include silica, alumina, titania, magnesia, zirconia, carbon, or combinations thereof. Cu-based catalysts can be made using known synthetic methods or purchased from commercial sources. In some embodiments, a Cu-based metal precursor materials are co-precipitated over a support material. For example, a Cu precursor and a Ni precursor can be co-precipitated over a silica support using catalyst preparation methodology known in the art.

EXAMPLES

[0043] The present invention will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes only, and are not intended to limit the invention in any manner. Those of skill in the art will readily recognize a variety of noncritical parameters, which can be changed or modified to yield essentially the same results.

Example 1

(Synthesis 35 wt % Cu Ni/SiO.SUB.2.)

[0044] The 35 wt % Cu Ni/SiO.sub.2 was prepared using precipitation methodology. Solution 1 was prepared by dissolving sodium carbonate (2.21 g) in water (150 mL). Solution 2 was prepared by mixing nickel nitrate hexahydrate (0.74 g, Ni(NO.sub.3).sub.2.6H.sub.2O), copper nitrate trihydrate (Cu(NO.sub.3).sub.2.3H.sub.2O, 6.65 g) and silica gel (3.1 g) in water (100 mL). Solution 2 agitated (420 rpm) for 1 hr. Solution 1 was titrated into Solution 2 until a blue precipitate appeared. The precipitate was filtered and washed with water several times. The solid precipitate was dried overnight at 120 C. and calcined at 450 C. for 4 hrs to obtain the final catalyst material.

Example 2

(Reduction of Cu-Ni Catalyst)

[0045] A known weight (1.000 g, 6.26 mM weight of Cu) of synthesized Cu-Ni catalyst (Example 2) was weighed into 100 mL Parr autoclave. The autoclave was pressurized to 3 MPa with H.sub.2, and then heated to the reduction temperature of about 265 C. for 6 hours. After the completion of reduction, the reactor was cooled down to room temperature and depressurized to atmospheric pressure.

Example 3

(Production of Ethanol)

[0046] Methanol (25 mL) and cesium oxalate (1 g, 2.8 mM g, MilliporeSigman, USA) was added into to the reactor containing reduced Cu-catalyst of Example 2. The vessel was pressurized with 2 MPa CO.sub.2 and 2 MPa H.sub.2 at room temperature. Then the reactor was then heated to 220 C. with a continuous stirring for 15 hours. On completion of the reaction, the was depressurized to 25 C. and 0.1 MPa (atmospheric pressure). The reactor vessel was opened and a small portion of the sample product was characterized using .sup.13C & .sup.1H NMR and by GC-MS. The product mixture included 30% ethanol in 30% and 10% ethylene glycol.