WO2018015824A1

WO2018015824A1 - Process for high-pressure hydrogenation of carbon dioxide to syngas in the presence of a copper/zinc/zirconium mixed metal oxide catalyst

Info

Publication number: WO2018015824A1
Application number: PCT/IB2017/053716
Authority: WO
Inventors: Aghaddin Mamedov; Clark Rea; Shahid Shaikh
Original assignee: SABIC Global Technologies BV
Current assignee: SABIC Global Technologies BV
Priority date: 2016-07-18
Filing date: 2017-06-21
Publication date: 2018-01-25
Anticipated expiration: 2019-01-18

Abstract

Processes and catalysts for the hydrogenation of carbon dioxide (CO₂) to produce a synthesis gas containing composition are disclosed. The process can include contacting a CuZnZr mixed metal oxide catalyst with hydrogen (H₂) and CO₂at a temperature of at least 600 °C and a pressure greater than atmospheric pressure to produce the syngas containing composition.

Description

PROCESS FOR HIGH-PRESSURE HYDROGENATION OF CARBON DIOXIDE TO SYNGAS IN THE PRESENCE OF A COPPER/ZINC/ZIRCONIUM MIXED METAL

OXIDE CATALYST

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 62/363,393, filed July 18, 2016, which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION A. Field of the Invention

[0002] The invention generally concerns a process for hydrogenation of carbon dioxide (C0₂) to produce a synthesis gas (syngas) containing composition that includes hydrogen (H₂) and carbon monoxide (CO). In particular, the process includes contacting a CuZnZr mixed metal oxide catalyst under conditions suitable to produce the syngas composition. B. Description of Related Art

[0003] Syngas (which includes carbon monoxide and hydrogen gases) is oftentimes used to produce chemicals such as methanol, tert-butyl methyl ether, ammonia, fertilizers, 2-ethyl hexanol, formaldehyde, acetic acid, and 1,4-butanediol. Syngas can be produced by common methods such as methane steam reforming technology as shown in reaction equation (1), partial oxidation of methane as shown in reaction (2), or dry reforming of methane as shown in reaction (3):

CH₄ + H₂0 - CO + 3H₂ AH₂₉8K = 206 kJ (1)

CH₄ + 0₂ CO + 2H₂ ΔΗ₂₉₈κ = - 8 kcal/mol (2)

CH₄ + C0₂ 2CO + 2H₂ ΔΗ₂₉₈κ = 247 kJ (3) While the reactions in equations (1) and (2) do not utilize carbon dioxide, equation (3) does. Commercialization attempts of the dry reforming of methane to produce syngas have suffered due to high-energy consumption, catalyst deactivation, and applicability of the syngas composition produced. Equation (4) illustrates the catalyst deactivation event due to carbonization. CH₄ + 2C0₂ C + 2CO + 2H₂0 (4)

[0004] Other attempts to convert carbon dioxide into carbon monoxide include the catalytic reduction of carbon dioxide using hydrogen as shown in equation (5).

C0₂+ H₂ ¾ CO + H₂0 ΔΗ= 10 kcal/mol (5)

This process, which is also known as a reverse water gas shift reaction, is mildly endothermic and generally takes place at temperatures of at least about 450 °C, with C0₂ conversion of 50% at temperatures between 560 °C to 580 °C. Furthermore, some methane can be formed as a by-product due to the methanation reaction as shown in equations (6) and (7).

CO + 3 H₂ ¾ CH₄ + H₂0 (6)

C0₂ + 4 H₂ ¾ CH₄ + 2 H₂0 (7)

[0005] Various catalysts have been used for the catalysis of the hydrogenation of carbon dioxide reaction. By way of example, U.S. Patent No. 7,435,759 to Jung et al. describes a ZnO supported on or co-precipitated with A1₂0₃ or Zr0₂, which after calcination is then impregnated with copper, which produces a copper impregnated catalyst for catalyzing the reverse shift water gas reaction at atmospheric pressure. This catalyst suffers from catalyst deactivation at high reactant flow rates in the presence of high amounts of C0₂ (H₂:C0₂ ratio of 1 :3).

[0006] Despite the foregoing, hydrogenation of carbon dioxide processes still suffer from production of the by-product methane, processing inefficiencies, and catalyst deactivation.

SUMMARY OF THE INVENTION

[0007] A discovery has been made that provides an alternate process for the production of syngas from hydrogen and carbon dioxide while producing less than 5 mol.% of methane as a by-product. The discovery is premised on the use of a CuZnZr mixed metal oxide catalyst {i.e., CuO-ZnO-Zr0₂) at temperatures of at least 600 °C and a pressure greater than atmospheric pressure. Such a process has a C0₂ conversion of at least 50% and can produce syngas compositions suitable as an intermediate or as feed material in a subsequent synthesis (e.g., methanol production, olefin synthesis, aromatics production, hydroformylation of olefins, carbonylation of methanol, and carbonylation of olefins) to form a chemical product or a plurality of chemical products. In preferred instances, the syngas composition is applicable for methanol synthesis.

[0008] In a particular aspect of the invention, a process for hydrogenation of carbon dioxide (C0₂) to produce a syngas containing composition that includes hydrogen (H₂) and carbon monoxide (CO) is described. The process can include contacting a CuZnZr mixed metal oxide catalyst with a reactant feed that includes H₂ and C0₂ at a reaction temperature of at least 600 °C or 610 °C to 650 °C, or 615 °C to 630 °C and a pressure greater than atmospheric pressure (e.g., 0.5 MPa to 6 MPa, or 1 MPa to 3 MPa) to produce a product stream comprising the syngas containing composition that includes H₂ and CO. [0009] In another particular aspect of the present invention, the process can include contacting a CuZnZr mixed metal oxide catalyst with a reactant feed that includes H₂ and C0₂ at a reaction temperature of at least 600 °C or 610 °C to 650 °C, or 615 °C to 630 °C, a pressure of at least 1 MPa, and a combined gas flow rate of H₂ and CO of at least 54 mL/min to produce a product stream that includes the syngas containing composition that includes H₂ and CO. In some instances, the combined flow rate is at least 60 mL/min to 120 mL/min, preferably, 100 mL/min to 110 mL/min. In some embodiments, the gas hourly space velocity of the combined flow rate is about 300 to 1000 h^"1.

[0010] In still another aspect of the invention, the process can include contacting a CuZnZr mixed metal oxide catalyst with a reactant feed that includes H₂ and C0₂ at a temperature of at least 600 °C or 610 °C to 650 °C, or 615 °C to 630 °C, a pressure of 1 MPa to 3 MPa, a H₂ gas flow rate of 70 to 100 mL/min, and a C0₂ gas flow rate of 15 to 30 mL/min, to produce a product stream that includes the syngas containing composition that includes H₂ and CO. In some instances, the H₂ gas flow rate can be 80 to 90 mL/min and the C0₂ gas flow rate can be 20 to 30 mL/min. [0011] In the processes of the present invention, the CuZnZr mixed metal oxide catalyst can include 50 wt. % to 60 wt. % CuO, 20 wt. % to 30 wt. % of ZnO and 15 wt. % to 25 wt. % of Zr0₂. In a preferred aspect of the invention, the catalyst includes about 55.19 wt. % CuO, 24.9 wt. % ZnO, and 19.9 wt. % Zr0₂. Without wising to be bound by theory, it is believe that since the CuO phase is co-precipitated with the ZnO and Zr0₂ phases, the active copper is inhibited from leaching from the catalyst as the co-precipitation produces small particles of copper and zinc embedded in the high interface area of the zirconia particles with a common interface area. In contrast, impregnation techniques produce large particles of pure copper and zinc and crystallized large particles of zirconia with little common interface area. The mixed oxides can be in the form of crystal phases forming separate phases of Zr0₂, ZnO and CuO/Cu. All phases can be separate phases of oxides in the solid material forming solid solution of mixed oxides in the crystal lattice of the solid solution. The catalyst can have a surface area of 103 m²/g. In some aspects of the processes of the present invention, the molar ratio of the reactant H₂ and C0₂ can be least 3 : 1, preferably 4: 1. In some instances, the produced syngas has a stoichiometric number of from 0.1 to 3.0 and, preferably, can have a methane content of less than 5 mol.%. In still other instances, the produced syngas can have a H₂ to CO molar ratio of 1 : 1 to 5: 1, or 3 : 1 to 4.6: 1.

[0012] In the context of the present invention 20 embodiments are now described. Embodiment 1 is a process for hydrogenating carbon dioxide (C0₂) to produce a syngas containing composition comprising hydrogen (H₂) and carbon monoxide (CO). The process includes contacting a CuZnZr mixed metal oxide catalyst with H₂ and C0₂ at a temperature of at least 600 °C and a pressure greater than atmospheric pressure to produce the syngas containing composition comprising H₂ and CO. Embodiment 2 is the process of Embodiment 1, wherein temperature is 610 °C to 650 °C, and preferably, the temperature is 615 °C to 630 °C. Embodiment 3 is the process of Embodiments 1 or 2, wherein the pressure is at least 1 MPa. Embodiment 4 is the process of any one of Embodiments 1 to 3 wherein the pressure is from 1 MPa to 3 MPa. Embodiment 5 is the process of any one of Embodiments 1 to 4, wherein the combined gas flow rate of H₂ and C0₂ is at least 54 mL/min, and preferably 60 mL/min to 120 mL/min or more preferably, 100 mL/min to 110 mL/min. Embodiment 6 the process of any one of Embodiments 1 to 5, wherein the H₂ gas flow rate is 70 to 100 mL/min and the C0₂ gas flow rate is 15 to 30 mL/min. Embodiment 7 is the process of any one of Embodiments 1 to 6, wherein the pressure is at least 1 MPa and the combined gas flow rate of H₂ and C0₂ is at least 54 mL/min. Embodiment 8 is the process of any one of Embodiments 1 to 7, wherein the pressure is 1 MPa to 3 MPa, the H₂ gas flow rate is 70 to 100 mL/min, and the C0₂ gas flow rate is 15 to 30 mL/min. Embodiment 9 is the process of any one of Embodiments 1 to 8, wherein the CuZnZr mixed metal oxide catalyst includes 50 wt. % to 60 wt. % CuO, 20 wt. % to 30 wt. % of ZnO, and 15 wt. % to 25 wt. % of Zr0₂, and preferably about 55.19 wt. % CuO, 24.9 wt. % ZnO, and 19.9 wt. % Zr0₂. Embodiment 10 is the process of any one of Embodiments 1 to 9, wherein the methane content in the produced syngas containing composition is 5 mol. % or less, or is from 2 mol. % to 5 mol. %. Embodiment 11 the process of any one of Embodiments 1 to 10, wherein the produced syngas containing composition is used to produce methanol. Embodiment 12 is the process of any one of Embodiments 1 to 10, wherein the produced syngas containing composition is used to produce an olefin; preferably the olefin is a C₂ to C₄ olefin or a mixture thereof. Embodiment 13 is the process of any one of Embodiments 1 to 12, wherein the CuZnZr mixed metal oxide catalyst is contacted with H₂ and C0₂ at a H₂:C0₂ volume ratio of at least 3 : 1, and preferably 4: 1. Embodiment 14 is the process of any one of Embodiments 1 to 13, wherein the produced syngas containing composition has a H₂ to CO molar ratio of 1 : 1 to 5: 1. Embodiment 15 is the process of any one of Embodiments 1 to 14 wherein the produced syngas containing composition has a H₂ to CO molar ratio of about 4: 1. Embodiment 16 is the process of any one of Embodiments 1 to 15 wherein the combined gas flow rate of H₂ and C0₂ is at least 60 mL/min to 120 mL/min. Embodiment 17 is the process of Embodiments 1 to 16 wherein the combined gas flow rate of H₂ and C0₂ is at least 100 mL/min to 110 mL/min. Embodiment 18 is the process of Embodiment 12, wherein the produced syngas containing composition is used to produce a C₂ to C₄ olefin or a mixture thereof. Embodiment 19 is the process of any one of Embodiments 1 to 18, wherein the methane content in the produced syngas containing composition is 2 mol. % to 5 mol. %. Embodiment 20 is the process of any one of Embodiments 1 to 19 wherein the CuZnZr mixed metal oxide catalyst is contacted with H₂ and C0₂ at a H₂:C0₂ volume ratio of at least 4: 1. [0013] The following includes definitions of various terms and phrases used throughout this specification.

[0014] The terms "about" or "approximately" are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment the terms are defined to be within 10%, preferably, within 5%, more preferably, within 1%, and most preferably, within 0.5%.

[0015] The terms "wt.%", "vol.%" or "mol.%" refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume, or the total moles of material that includes the component. In a non-limiting example, 10 moles of component in 100 moles of the material is 10 mol.% of component.

[0016] The term "substantially" and its variations are defined to include ranges within 10%, within 5%, within 1%, or within 0.5%. [0017] The terms "inhibiting" or "reducing" or "preventing" or "avoiding" or any variation of these terms, when used in the claims and/or the specification includes any measurable decrease or complete inhibition to achieve a desired result.

[0018] The term "effective," as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result.

[0019] The use of the words "a" or "an" when used in conjunction with the term "comprising" in the claims or the specification may mean "one," but it is also consistent with the meaning of "one or more," "at least one," and "one or more than one."

[0020] The words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "includes" and "include") or "containing" (and any form of containing, such as "contains" and "contain") are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0021] The process of the present invention can "comprise," "consist essentially of," or "consist of particular ingredients, components, compositions, etc. disclosed throughout the specification. With respect to the transitional phase "consisting essentially of," in one non- limiting aspect, a basic and novel characteristic of the process of the present invention is the ability to hydrogenate carbon dioxide to produce syngas.

[0022] Other objects, features and advantages of the present invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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. [0024] FIG. 1 is an illustration of a process of the present invention to produce syngas using a combined C0₂ and H₂ containing reactant feed gas and the CuZnZr mixed metal oxide catalyst of the present invention.

[0025] FIG. 2 is an illustration of a process of the present invention to produce syngas using a H₂ reactant feed gas source, a C0₂ reactant feed gas source, and the CuZnZr mixed metal oxide catalyst of the present invention.

[0026] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and may herein be described in detail. The drawings may not be to scale.

DETAILED DESCRIPTION OF THE INVENTION

[0027] A discovery has been made that addresses the aforementioned problems and inefficiencies associated with the production of syngas from hydrogenation of carbon dioxide. The discovery is premised on the use of a CuZnZr mixed metal oxide catalyst in the hydrogenation of carbon dioxide reaction, which results in relatively high carbon dioxide conversions with minimal (e.g., less than 5 mol. %) or no production of alkane byproducts (e.g., methane). Furthermore, these results can be achieved at processing conditions having a temperature of at least 600 °C and greater than atmospheric pressure.

[0028] 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. Process to Produce Syngas [0029] Conditions sufficient to produce syngas from the hydrogenation of C0₂ reaction include temperature, time, flow rate of feed gases, and pressure. The temperature range for the hydrogenation reaction can range from at least 600 °C, 600 °C to 650 °C, 615 °C to 630 °C, or about 620 °C and all ranges and values there between including 600 °C, 605 °C, 610 °C, 615 °C, 620 °C, 625 °C, 630 °C, 635 °C, 640 °C, 645 °C, or 650 °C. The average pressure for the hydrogenation reaction can range from above atmospheric pressure, at least 1 MPa, 1 MPa to about 6 MPa, preferably 1 MPa to 3 MPa and all pressures there between (e.g., 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa). The upper limit on pressure can be determined by the reactor used. The conditions for the hydrogenation of C0₂ to syngas can be varied based on the type of the reactor used. The combined flow rate for the for the reactants (e.g., H₂ and C0₂) in the hydrogenation reaction can range from at least 54 mL/min, 60 mL/min to 120 mL/min, from about 100 mL/min to about 1 10 mL/ min or all ranges and values there between (e.g., at least 54 mL/min, 55 mL/min, 56 mL/min, 57 mL/min, 58 mL/min, 59 mL/min, 60 mL/min, 61 mL/min, 62 mL/min, 63 mL/min, 64 mL/min, 65 mL/min, 66 mL/min, 67 mL/min, 68 mL/min, 69 mL/min, 70 mL/min, 71 mL/min, 72 mL/min, 73 mL/min, 74 mL/min, 75 mL/min, 76 mL/min, 77 mL/min, 78 mL/min, 79 mL/min, 80 mL/min, 81 mL/min, 82 mL/min, 83 mL/min, 84 mL/min, 85 mL/min, 86 mL/min, 87 mL/min, 88 mL/min, 89 mL/min, 90 mL/min, 91 mL/min, 92 mL/min, 93 mL/min, 94 mL/min, 95 mL/min, 96 mL/min, 97 mL/min 98 mL/min, 99 mL/min, 100 mL/min, 101 mL/min, 102 mL/min, 103 mL/min, 104 mL/min, 105 mL/min, 106 mL/min, 107 mL/min 108 mL/min, 109 mL/min, 1 10 mL/min, 1 1 1 mL/min, 1 12 mL/min, 1 13 mL/min, 1 14 mL/min, 1 15 mL/min, 1 16 mL/min, 1 17 mL/min, 1 18 mL/min, 1 19 mL/min, or 120 mL/min). In some instances, the H₂ flow rate can range from 70 mL/min to 100 mL/min, 75 to 95 mL/min, 80 to 90 mL/min, or all ranges and values there between (e.g., 70 mL/min, 71 mL/min, 72 mL/min, 73 mL/min, 74 mL/min, 75 mL/min, 76 mL/min, 77 mL/min, 78 mL/min, 79 mL/min, 80 mL/min, 81 mL/min, 82 mL/min, 83 mL/min, 84 mL/min, 85 mL/min, 86 mL/min, 87 mL/min, 88 mL/min, 89 mL/min, 90 mL/min, 91 mL/min, 92 mL/min, 93 mL/min, 94 mL/min, 95 mL/min, 96 mL/min, 97 mL/min, 98 mL/min, 99 mL/min, or 100 mL/min). The C0₂ gas flow rate can be 15 mL/min to 30 mL/min, 20 to 30 mL/min or any range or value there between (e.g., 15 mL/min, 16 mL/min, 17 mL/min, 18 mL/min, 19 mL/min, 20 mL/min, 21 mL/min, 22 mL/min, 23 mL/min, 24 mL/min, 25 mL/min, 26 mL/min, 27 mL/min, 28 mL/min, 29 mL/min, or 30 mL/min). In a particular instance, the H₂ gas flow rate is 80 to 90 mL/min, preferably about 85 mL/min and the C0₂ gas flow rate is 20 to 30 mL/min, preferably about 21 mL/min. [0030] In another aspect, the reaction can be carried out over the CuZnZr mixed metal oxide catalyst of the current invention having particular syngas selectivity and conversion results. Therefore, in one aspect, the reaction can be performed with a C0₂ conversion of at least 50 mol.%, at least 60 mol.%, at least 70 mol.%, at least 80 mol.%, or at least 99 mol.%. The method can further include collecting or storing the produced syngas along with using the produced syngas as a feed source, solvent, or a commercial product. Prior to use, the catalyst can be subjected to reducing conditions to convert the copper oxide and the other metals in the catalyst to a lower valance state (e.g., Cu⁺² to Cu⁺¹ and Cu° species, Zn⁺² to Zn°, etc.). A non-limiting example of reducing conditions includes flowing a gaseous stream that includes a hydrogen gas or a hydrogen gas containing mixture (e.g., a H₂ and argon gas mixture) at a temperature of 250 °C to 280 °C for a sufficient period of time (e.g., 1, 2, or 3 hours).

[0031] Referring to FIG. 1, a system 100 is illustrated, which can be used to convert a reactant gas stream of carbon dioxide (C0₂) and hydrogen (H₂) into syngas using the CuZnZr mixed metal oxide catalyst of the present invention. The system 100 can include a combined reactant gas source 102, a reactor 104, and a collection device 106. The combined reactant gas source 102 can be configured to be in fluid communication with the reactor 104 via an inlet 108 on the reactor. The combined reactant gas source 102 can be configured such that it regulates the amount of reactant feed (e.g., C0₂ and H₂) entering the reactor 104. As shown, the combined reactant gas source 102 is one unit feeding into one inlet 108. By comparison, FIG. 2 depicts a system 200 for the process of the present invention having two feed inlets. As shown in FIG. 2, a hydrogen gas reactant feed source 202 and a carbon dioxide reactant gas feed source 204 are in fluid communication with reactor 104 via hydrogen gas inlet 206 and carbon dioxide gas inlet 208, respectively. It should be understood that the number of inlets and/or separate feed sources can be adjusted to reactor sizes and/or configurations. The reactor 104 can include a reaction zone 1 10 having the CuZnZr mixed metal oxide catalyst 1 12 of the present invention. The reactor can include various automated and/or manual controllers, valves, heat exchangers, gauges, etc., for the operation of the reactor. The reactor can have insulation and/or heat exchangers to heat or cool the reactor as desired. The amounts of the reactant feed and the mixed metal oxide catalyst 1 12 used can be modified as desired to achieve a given amount of product produced by the systems 100 or 200. In a preferred aspects, a continuous flow reactor can be used. Non-limiting examples of continuous flow reactors include fixed-bed reactors, fluidized reactors, bubbling bed reactors, slurry reactors, rotating kiln reactors, moving bed reactors or any combinations thereof when two or more reactors are used. In some embodiments, the reactant gas is preheated prior to being fed to the reactor. In some embodiments, reaction zone 1 10 is a multi-zone reactor with different stages of heating in each zone. The reactor 104 can include an outlet 1 14 configured to be in fluid communication with the reaction zone 1 10 and configured to remove a first product stream comprising syngas from the reaction zone. Reaction zone 1 10 can further include the reactant feed and the first product stream. The products produced can include hydrogen and carbon monoxide. The product stream can also include unreacted carbon dioxide, water, and less than 5 mol.% of alkanes (e.g., methane). In some aspects, the catalyst can be included in the product stream. The collection device 106 can be in fluid communication with the reactor 104 via the product outlet 1 14. Reactant gas inlets 108, 204, and 208, and the outlet 1 14 can be opened and closed as desired. The collection device 106 can be configured to store, further process, or transfer desired reaction products (e.g., syngas) for other uses. In a non-limiting example, collection device 106 can be a separation unit or a series of separation units that are capable of separating the gaseous components from each other (e.g., separate carbon dioxide or water from the stream). Water can be removed from the product stream with any suitable method known in the art (e.g., condensation, liquid/gas separation, etc.). [0032] Any unreacted reactant gas can be recycled and included in the reactant feed to maximize the overall conversion of C0₂ to syngas, which increases the efficiency and commercial value of the C0₂ to syngas conversion process of the present invention. The resulting syngas can be sold, stored or used in other processing units as a feed source. Still further, the systems 100 or 200 can also include a heating/cooling source (not shown). The heating/cooling source can be configured to heat or cool the reaction zone 1 10 to a temperature sufficient (e.g., at least 600 °C or 600 °C to 650 °C) to convert C0₂ in the reactant feed to syngas via hydrogenation. Non-limiting examples of a heating/cooling source can be a temperature controlled furnace or an external, electrical heating block, heating coils, or a heat exchanger. B. Catalyst and Preparation Thereof

[0033] The CuZnZr mixed metal oxide catalyst of the present invention can include 50 wt. % to 60 wt. % CuO, 20 wt. % to 30 wt. % of ZnO and 10 wt. % to 25 wt. % of Zr0₂ or any value or range there between. For example, and with respect to CuO, the catalyst can include 50 wt. %, 51 wt. %, 52 wt. %, 53 wt. %, 54 wt. %, 55 wt. %, 56 wt. %, 57 wt. %, 58 wt. %, 59 wt. %, 60 wt. % CuO. With respect to ZnO, the catalyst can include 20 wt. %, 21 wt. %, 22 wt. %, 23 wt. %, 24 wt. %, 25 wt. %, 26 wt. %, 27 wt. %, 28 wt. %, 29 wt. %, or 30 wt. % ZnO. With respect to Zr0₂, the catalyst can include 10 wt. %, 1 1 wt. %, 12 wt. %, 13 wt. %, 14 wt. %, 15 wt. %, 16 wt. %, 17 wt. %, 18 wt. %, 19 wt. %, 20 wt. %, 21 wt. %, 22 wt. %, 23 wt. %, 24 wt. %, or 25 wt. % of Zr0₂. In a particular embodiment, the catalyst includes about 55.19% CuO, 24.9% ZnO, and 19.9% Zr0₂. The weight percentage of the elements can be 40 to 45 wt.% Cu, 15 to 25 wt.% Zn, and 10 to 15 wt.% Zr, or about 44 wt.% Cu, about 20 wt.% Zn and about 13.7 wt.% Zr. The weight ratio of Cu:Zn:Zr can range from 2.5 : 1 :0.5 to 3.0: 1 : 1 or 2.2: 1 :0.68. The catalyst can have a surface area from 100 m²/g to 1 10 m²/g, or 100 to 105 m²/g, or 103 m²/g. Such a catalyst can be hard and have mechanical stability (e.g., the catalyst does not break apart during use).

[0034] Suitable sources for the metals for use in the preparation of the catalysts of this invention include, without limitation, nitrates, halides, organic acid, inorganic acid, hydroxides, carbonates, oxyhalides, sulfates and other groups which may exchange with oxygen under high temperatures so that the metal compounds become metal oxides.

[0035] As further illustrated in the Examples, the catalyst can be made using a co- precipitation method. In a non-limiting example, a first metal salt (e.g., copper metal salt), a second metal salt (e.g., zinc metal salt), and a third metal salt (e.g., zirconium metal salt) can be completely solubilized, or substantially solubilized, in a solvent (e.g., aqueous solution). Examples of the first metal salt include nitrates, ammonium nitrates, carbonates, oxides, hydroxides, or halides of copper. Examples of the second metal salt include nitrates, ammonium nitrates, carbonates, oxides, hydroxides, or halides of zinc. Examples of the third metal salt include nitrates, ammonium nitrates, carbonates, oxides, hydroxides, halides of zirconium. In a particular embodiment, Cu(N0₃)₃, Zn(N0₃)₂, and Zr(N0₃)₃ can be solubilized in deionized water. In some embodiments, three solutions are prepared and mixed together. The metal salts can be obtained from commercial vendors, for example, Sigma-Aldrich ® (U.S.A.). Aqueous base (e.g., ammonium hydroxide or sodium hydroxide) can be added to the solution in an amount effective to precipitate a Cu/Zn/Zr metal hydroxide precursor from the solution. The pH of the solution can be 7 to 9, 7.5 to 8.5, or 8 after addition of the base. The Cu/Zn/Zr metal hydroxide precursor can be heated from 55 °C to 75 °C, 60 °C to 70 °C and all values there between including 55 °C, 56 °C, 57 °C, 58 °C, 59 °C, 60 °C, 61 °C, 62 °C, 63 °C, 64 °C, 64 °C, 65 °C, 66 °C, 67 °C , 68 °C , 69 °C, 70 °C, 71 °C, 72 °C, 73 °C, 74 °C, or 75 °C, with agitation to further the formation of the Cu/Zn/Zr metal hydroxide precursor. In some embodiments, the Cu/Zn/Zr precursor precipitate can be separated from the solution using known separation techniques (e.g., centrifugation, filtration, etc.). The separated Cu/Zn/Zr precursor precipitate can be washed with water (e.g., deionized water) to remove any excess base. Washing and filtering the Cu/Zn/Zr precursor precipitate can be repeated as necessary to remove all, or substantially all, of the base from the Cu/Zn/Zr precursor precipitate. Residual water can be removed from the Cu/Zn/Zr precursor by heating the solution (e.g., drying the solution) at a temperature from 90 °C to 1 10 °C, or 95 °C to 105 °C, or any value there between including 90 °C, 91 °C, 92 °C, 93 °C, 94 °C, 95 °C, 96 °C, 97 °C, 98 °C, 99 °C, 100 °C, 101 °C, 102 °C, 103 °C, 104 °C, 105 °C, 106 °C, 107 °C, 108 °C, 109 °C, or 1 10 °C for a time period sufficient (e.g., 3 to 24 hours, 8 to 20 hours, or 12 hours) to remove all or a majority of the water to produce a dried powdered material. In some instances, drying is performed at 105 °C for 12 hours. The dried CuZnZr material can be then be calcined within 8 hours of drying by heating the dried material to an average temperature between 350 °C and 600 °C, 400 °C to 550 °C, with 400 °C being preferred, for 3 to 12 hours or 4 to 8 hours in the presence of a flow of an oxygen source (e.g., air at 250 cc/per minute) to form the CuZnZr mixed metal oxide catalyst. Prior to use in the process of the invention, the catalyst particles can be reduced in size (e.g., crushed) to a particle size of 30-50 mesh.

C. Reactants and Products

[0036] Carbon dioxide gas and hydrogen gas can be obtained from various sources. In one non-limiting instance, the carbon dioxide 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 after recovering the carbon dioxide from a gas stream. A benefit of recycling such 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 hydrogen may be from various sources, including streams coming from other chemical processes, like water splitting (e.g., photocatalysis, electrolysis, or the like), additional syngas production, ethane cracking, methanol synthesis, or conversion of methane to aromatics. The molar H₂:C0₂ reactant gas ratio for the hydrogenation reaction can range from 2.5 : 1 to 5 : 1, from 3 : 1 to 4: 1. In one instance the reactant gas stream includes 50 to 90 vol.% H₂ and 15 to 35 vol.% C0₂, preferably 65 to 85 vol.% H₂ and 20 to 30 vol.% C0₂, or more preferably about 84 vol.% H₂ and about 21 vol.% C0₂ or about 78.7 vol.% H₂ and about 26.2 vol.% C0₂. In some embodiments, the streams are not combined. In these instances, the hydrogen and carbon dioxide can be delivered at the same H₂:C0₂ molar ratio. In some examples, the remainder of the reactant gas stream can include another gas or gases provided the gas or gases are inert, such as argon (Ar) or nitrogen (N₂), and do not negatively affect the reaction. All possible percentages of C0₂ plus H₂ plus inert gas in the current embodiments can have the described H₂:C0₂ ratios herein. Preferably, the reactant mixture is highly pure and substantially devoid of water or steam. In some embodiments, the carbon dioxide can be dried prior to use (e.g., pass through a drying media) to contain minimal amounts of water or no water at all.

[0037] The process of the present invention can produce a product stream that includes a mixture of H₂ and CO having a molar H₂:CO ratio suitable for the synthesis of various chemical products. Non-limiting examples of synthesis include methanol production, olefin synthesis, aromatics production, hydroformylation of olefins, carbonylation of methanol, and carbonylation of olefins. Non-limiting examples of products that can be produced include aliphatic oxygenates, methanol, olefin synthesis, aromatics production, carbonylation of methanol, carbonylation of olefins, or reduction of iron oxide in steel production. The molar H₂:CO ratio can be 0.90 to 1.1 or 1, which is suitable for oxo-products (e.g., C₂+ alcohols, dimethyl ether, etc.). In yet another example, the molar H₂:CO ratio can be about 1.9: 1 to 5 : 1, or 3 : 1, 3.5 : 1, 3.6: 1, 4: 1, 4.5 : 1, 4.6: 1 or 5 : 1, which is suitable for the production of methanol from syngas. In embodiments, when C0₂ is present in the product stream, the process can produce a mixture suitable for the production of methanol having at least 2 mol.% up to 20 mol.% of C0₂. The amount of alkane (e.g., methane) produced in the process of the present reaction can be less than 5 mol.%, less than 4 mol.%, 3 mol.%, 2 mol.%, 1 mol.%), or 0 mol.%> based on the total moles of components in the product stream. The product stream can include unreacted C0₂. By way of example, the product stream can include less than 20 mol%, 19 mol%, 18 mol%, 17 mol%, 16 mol%, 15 mol%, 14 mol%, 13 mol%, 12 mol%, 1 1 mol%, 10 mol%, 9 mol%, 8 mol%, 7 mol%, 5 mol%, 4 mol%, 3 mol%, 2 mol%>, 1 mol%> or 0 mol%> of C0₂ based on the total moles of components in the product stream. In a particular instance, the product stream can include about 15.8 mol%> CO, about 14 mol%> C0₂, about 3.6 mol%> CH₄, and about 66.2 mol%> H₂. In another embodiment, the product stream can include about 16.3 mol%> CO, about 13 mol%> C0₂, about 2.4 mol%> CH₄, and about 68.3 mol%> H₂. In still another embodiment, the product stream can include about 13.9 mol% CO, about 17.5 mol% C0₂, about 4.2 mol% CH₄, and about 64.4 mol% H₂. In yet another embodiment, the product stream can include about 14 mol%> CO, about 17.2 mol%> C0₂, about 4.8 mol% CH₄, and about 64 mol% H₂. EXAMPLES

[0038] 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 of CuZnZr Mixed Metal Oxide Catalyst)

[0039] Copper nitrate (35.7g, Cu(N0₃)₃.3H₂0), zinc nitrate (20.9 g, Zn(N0₃)₂.6H₂0), and zirconium nitrate (11.6 g, Zr(N0₃)₃«6H₂0) were dissolved in water (500 mL). Under stirring, using overhead motor, the solution was heated to 85 °C. Sodium carbonate (Na₂C0₃, 30 wt.% solution) was added gradually to the solution to co-precipitate the CuZnZr metal oxide precursor material. The pH of the solution was maintained at 8 and heated to a temperature of 80 to 85 °C for 2 hours. The CuZnZr metal oxide precursor material was isolated by filtration, and washed with warm (60 °C) water (3 X 500 mL) to remove excess base. The washed CuZnZr metal oxide precursor material was dried at 105 °C for 12 hours. The dried CuZnZr metal oxide precursor material was calcined at 400 °C in air flow of 250 cc/min for 8 hours to form the black CuZnZr mixed metal oxide catalyst of the present invention. Prior to use, the CuZnZr mixed metal oxide catalyst was crushed to a particle size of 20-50 mesh. The CuZnZr mixed metal oxide catalyst had a surface area of 103 m²/g.

Example 2

(General Process for Hydrogenation of Carbon Dioxide)

[0040] General Procedure. Catalyst testing was performed in a high throughput metal reactor system. The reactors are fixed bed type reactor with a 2.5 cm inner diameter and 40 cm in length. Gas flow rates were regulated using two mass flow controllers. Reactor pressure was maintained by using a back pressure regulator. The reactor temperature was maintained by an external, electrical heating block. The effluent of the reactors was connected to a gas chromatograph for online gas analysis using a molecular sieve and Hayesep D column and thermal conductivity detector (TCD). The catalyst (3 mL) was placed on top of inert material inside the reactor. Prior to the reaction test, the catalyst was reduced at 600 °C under 25 vol.% H₂ in Ar for 2 h. In all examples, C0₂ conversion was calculated by the following formula.

C0₂ conversion, % mol = (%CO + %CH₄) / (%CO + %C¾ + %C0₂) (8) which presents the reactions of equations (5) and (7) discussed above: C0₂+ H₂ ¾ CO + H₂0 (5)

C0₂ + 4 H₂ ¾ CH₄ + 2 H₂0 (7)

Therefore, equation (8) presents the sum of all carbon, products divided by the total number of carbons.

Example 3

(Process for Hydrogenation of Carbon Dioxide)

[0041] The general procedure of Example 2 was followed with the following conditions: a pressure of 2.8 MPa, a temperature of 620 °C, a H₂ flow rate of 84 cc/min and a C0₂ flow rate of 21 cc/min. Time on stream (TOS), molar percentage of components in the product stream and % carbon dioxide conversion and results are listed in Table 1. Table 1

*Time on Stream

Example 4

(Process for Hydrogenation of Carbon Dioxide)

[0042] The general procedure of Example 2 was followed using the following conditions: a pressure of 1 MPa, a temperature of 620 °C, a H₂ flow rate of 78.7 cc/min and a C0₂ flow rate of 26.2 cc/min. Results are listed in Table 2.

Table 2

Example 5

(Process for Hydrogenation of Carbon Dioxide- Decreased Flow Rates)

[0043] The general procedure of Example 2 was followed using the following conditions: a pressure of 2.8 MPa, a temperature of 650 °C, a H₂ flow rate of 42 cc/min and a C0₂ flow rate of 12 cc/min. Results are listed in Table 3.

Table 3

[0044] From the comparison of Example 5 with Example 3 and 4, it was determined that decreasing the flow rates of reactant gas by about 50% to 53% at high pressure converted less of the carbon dioxide to carbon monoxide and produced more of the methane by-product. [0045] The process conditions for Examples 3 and 4 produced syngas with a methane content (e.g., 3.8 to 4.7 mol%) similar to the methane content of syngas produced from methane reforming. Syngas produced at the conditions of Examples 3 and 4 with the catalyst of the present invention is suitable for use as an intermediate or as feed material in a subsequent synthesis (e.g., methanol production, olefin synthesis, aromatics production, hydroformylation of olefins, carbonylation of methanol, and carbonylation of olefins) to form a chemical product or a plurality of chemical products.

Claims

1. A process for hydrogenating carbon dioxide (C0₂) to produce a syngas containing composition comprising hydrogen (H₂) and carbon monoxide (CO), the process comprising contacting a CuZnZr mixed metal oxide catalyst with H₂ and C0₂ at a temperature of at least 600 °C and a pressure greater than atmospheric pressure to produce the syngas containing composition comprising H₂ and CO.

2. The process of claim 1, wherein temperature is 610 °C to 650 °C, preferably, 615 °C to 630 °C.

3. The process of any one of claims 1 or 2, wherein the pressure is at least 1 MPa.

4. The process of any one of claims 1 or 2, wherein the combined gas flow rate of H₂ and C0₂ is at least 54 mL/min, preferably 60 mL/min to 120 mL/min, or more preferably, 100 mL/min to 110 mL/min.

5. The process of any one of claims 1 or 2, wherein the H₂ gas flow rate is 70 to 100 mL/min and the C0₂ gas flow rate is 15 to 30 mL/min.

6. The process of any one of claims 1 or 2, wherein the pressure is at least 1 MPa and the combined gas flow rate of H₂ and C0₂ is at least 54 mL/min.

7. The process of any one of claims 1 or 2, wherein the pressure is 1 MPa to 3 MPa, the H₂ gas flow rate is 70 to 100 mL/min, and the C0₂ gas flow rate is 15 to 30 mL/min.

8. The process of any one of claims 1 or 2, wherein the CuZnZr mixed metal oxide catalyst comprises 50 wt. % to 60 wt. % CuO, 20 wt. % to 30 wt. % of ZnO, and 15 wt. % to 25 wt. % of Zr0₂, preferably about 55.19 wt. % CuO, 24.9 wt. % ZnO, and 19.9 wt. % Zr0₂.

9. The process of any one of claims 1 or 2, wherein the methane content in the produced syngas containing composition is 5 mol. % or less or 2 mol. % to 5 mol. %.

10. The process of any one of claims 1 or 2, wherein the produced syngas containing composition is used to produce methanol.

11. The process of any one of claims 1 or 2, wherein the produced syngas containing composition is used to produce an olefin, preferably a C₂ to C₄ olefin or a mixture thereof.

12. The process of any one of claims 1 or 2, wherein the CuZnZr mixed metal oxide catalyst is contacted with H₂ and C0₂ at a H₂:C0₂ volume ratio of at least 3 : 1, or 4: 1.

13. The process of any one of claims 1 or 2, wherein the produced syngas containing composition has a H₂ to CO molar ratio of 1 : 1 to 5: 1, preferably about 4: 1.

14. The process of any one of claims 1 or 2, wherein the produced syngas containing composition has a H₂ to CO molar ratio of about 4: 1.

15. The process of any one of claims 1 or 2, wherein the combined gas flow rate of H₂ and C0₂ is at least 60 mL/min to 120 mL/min.

16. The process of any one of claims 1 or 2, wherein the combined gas flow rate of H₂ and C0₂ is at least 100 mL/min to 110 mL/min.

17. The process of claim 11, wherein the produced syngas containing composition is used to produce a C₂ to C₄ olefin or a mixture thereof.

18. The process of any one of claims 1 or 2, wherein the methane content in the produced syngas containing composition is 2 mol. % to 5 mol. %.

19. The process of any one of claims 1 or 2, wherein the CuZnZr mixed metal oxide

catalyst is contacted with H₂ and C0₂ at a H₂:C0₂ volume ratio of at least 4: 1.

20. The process of any one of claims 1 or 2, wherein the pressure is IMPa to 3 MPa.