Metal oxide-metal catalyst, preparation method and application thereof, and reverse water gas reaction method

Abstract

The invention relates to the technical field of catalysts, in particular to a metal oxide-metal catalyst, a preparation method and application thereof and a reverse water gas reaction method, the metal oxide-metal catalyst comprises a carrier and an active component loaded on the carrier; the active component comprises an oxide of molybdenum and a first metal simple substance; the first metal is selected from Ru and / or Cu; in the catalyst, the mass ratio of the molybdenum element to the first metal element is 1: (0.20-0.66); in an XRD (X-Ray Diffraction) pattern of the catalyst, at least one diffraction peak exists when 2 theta is 26.0 + / -0.15 degrees, 36.9 + / -0.15 degrees, 40.6 + / -0.15 degrees and 58.8 + / -0.15 degrees. The catalyst is used for a reverse water gas shift reaction, has good stability, does not have an inactivation sign after reacting for 100 hours, and has high activity, selectivity and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a metal oxide-metal catalyst, a preparation method and application thereof, and a reverse water gas shift reaction method. BACKGROUND

[0002] The reverse water gas shift (RWGS) reaction, i.e., the process of reacting CO2 and H2 to generate CO and H2O, is an important industrial reaction for carbon dioxide resource utilization. However, the existing RWGS reaction catalysts have the problems of insufficient activity at low temperatures and often accompanied by a methanation side reaction, resulting in a decrease in the yield of carbon monoxide. The methanation reaction is an exothermic process, which is thermodynamically favorable, and therefore has a very high equilibrium conversion rate in the low temperature range. At a relatively low reaction temperature (200-250℃), the product is mainly CH4 and H2O. When the temperature is increased to above 450℃, the proportion of CO byproduct (produced by the RWGS reaction) increases, and at the same time, the proportion of unreacted H2 also increases, accompanied by a decrease in CH4 product. The molar proportion of CO2 continues to decrease in the process of temperature increase, and this trend is the result of the competition between methanation and RWGS reaction. When the temperature is greater than 600℃, the proportion of CO in the product exceeds that of CH4.

[0003] Although increasing the reaction temperature can improve the activity and selectivity of the reverse water gas shift reaction, high temperature (>600℃) leads to high energy consumption. Different catalyst systems and preparation methods have been used in early literature and patents to improve the performance of the catalyst in the reverse water gas shift reaction, or the reaction rate and CO selectivity are improved by increasing the reaction temperature (>600℃, even as high as 1000℃). MoO3-based catalysts have been found to have the ability to catalyze the reverse water gas shift reaction, but the activity is poor. SUMMARY

[0004] In order to solve the problems of insufficient activity of the catalyst at low temperature in the RWGS reaction and the methanation side reaction in the reaction process in the prior art, the present application provides a metal oxide-metal catalyst, a preparation method and application thereof, and a reverse water gas shift reaction method. The catalyst described in the present application is used for the reverse water gas shift reaction and exhibits good catalytic activity at low temperature, while the methanation side reaction is inhibited, the cost is low, and the stability is good.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a metal oxide-metal catalyst, which comprises a carrier and an active component supported on the carrier; the active component comprises an oxide of molybdenum and a first metal element;

[0006] The first metal is selected from Ru and / or Cu;

[0007] In the catalyst, the mass ratio of molybdenum element to first metal element is 1:0.20-0.66.

[0008] The XRD pattern of the catalyst has at least one diffraction peak at 2θ of 26.0±0.15°, 36.9±0.15°, 40.6±0.15°, and 58.8±0.15°.

[0009] The second aspect of the present application provides a preparation method of a metal oxide-metal catalyst, which comprises:

[0010] contacting a solution containing a molybdenum salt and a first metal source with a carrier, drying, calcining, and reducing under an atmosphere containing a reducing gas, the first metal being selected from Ru and / or Cu;

[0011] The mass ratio of the molybdenum element to the first metal element is 1:0.20-0.66;

[0012] When the first metal is Ru, the reduction conditions include a reduction temperature of 400-600℃;

[0013] When the first metal is Cu, the reduction conditions include a reduction temperature of 300-450℃.

[0014] The third aspect of the present application provides a metal oxide-metal catalyst prepared by the preparation method of the present application.

[0015] The fourth aspect of the present application provides an application of the metal oxide-metal catalyst of the present application in a carbon dioxide reduction reaction.

[0016] The fifth aspect of the present application provides a reverse water gas shift reaction method, which comprises contacting CO2 with H2 in the presence of the catalyst of the present application.

[0017] According to the above technical solution, the metal oxide-metal catalyst of the present application has an active component comprising an oxide of molybdenum and a first metal element (Ru and / or Cu), and the oxide of molybdenum comprises MoO x (x is the molar ratio of O to Mo in the oxide of molybdenum, x<3, for example, MoO2, Mo9O 26 ).

[0018] The metal oxide-metal catalyst has the advantages of high CO2 conversion rate and high CO selectivity in a wide temperature range, for example, 300-600 DEG C, and can achieve high CO2 conversion rate and high CO selectivity at a lower temperature condition (for example, 350 DEG C-550 DEG C); the CO yield is more than 35% at a reaction temperature of 400 DEG C, and the CO selectivity is higher than 90%; the catalyst has good stability, and no deactivation is found after 100h of reaction. It is shown that the metal oxide-metal catalyst has high activity, selectivity and stability. The preparation method of the metal oxide-metal catalyst is simple and easy to implement. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is an XRD pattern of the precursor prepared in Example 1;

[0020] Figure 2 is an XRD pattern of the molybdenum oxide-ruthenium catalyst prepared in Example 1;

[0021] Figure 3 is an XRD pattern of the precursor prepared in Example 2;

[0022] Figure 4 is an XRD pattern of the molybdenum oxide-copper catalyst prepared in Example 2. DETAILED DESCRIPTION

[0023] The endpoints of the ranges and any values claimed herein are not to be understood as being limited to the exact values recited as implicitly disclosed by the above description. Ranges can be expressed as from one "value and / or to another value. When such ranges are recited, endpoints are included. Also, it will be understood that every range of values given throughout this specification will include every narrower range that falls within the broader range, wherein each narrow range can be defined by either a minimum or a maximum, or both, of the endpoints of the broader range. It will be further understood that every range given throughout this specification will include every narrower range that falls within the broader range, wherein the narrower ranges can be defined by either a minimum or a maximum, or both, of the endpoints of the broader range.

[0024] XRD diffraction peak explanation:

[0025] 2theta is 26.0±0.15°, 36.9±0.15°, 40.6±0.15°, 58.8±0.15°, which is a characteristic diffraction peak of MoO2;

[0026] 2theta is 43.9±0.15°, which is a characteristic diffraction peak of metal Ru;

[0027] 2theta is 35.5±0.15°, which is a characteristic diffraction peak of CuO;

[0028] 2theta is 23.7±0.15°, 26.4±0.15°, which is a characteristic diffraction peak of CuMoO4;

[0029] 2θ is 35.0±0.15°, 53.8±0.15° as characteristic diffraction peaks of RuO2;

[0030] 2θ is 43.3±0.15°, 50.4±0.15°, 74.1±0.15° as characteristic diffraction peaks of metal Cu;

[0031] 2θ is 27.3±0.15° as characteristic diffraction peak of MoO3;

[0032] 2θ is 40.6±0.15° as characteristic diffraction peak of metal Mo.

[0033] In the context of the present application, the XRD test conditions: the structure of the reduced catalyst is characterized by using D / MAX-2500 model X-ray diffractometer manufactured by Japan Science Corporation. Cu-Ka radiation (λ=0.15406nm) is adopted, the operating current is 100mA, and the voltage is 40kV. The scanning range is 2θ=20-80°, and the scanning rate is 5° / min.

[0034] The first aspect of the present application provides a metal oxide-metal catalyst, which comprises a carrier and an active component supported on the carrier; the active component comprises an oxide of molybdenum and a first metal element;

[0035] The first metal is selected from Ru and / or Cu;

[0036] In the catalyst, the mass ratio of molybdenum element to the first metal element is 1:0.20-0.66;

[0037] In the XRD pattern of the catalyst, there is at least one diffraction peak at 2θ of 26.0±0.15°, 36.9±0.15°, 40.6±0.15°, 58.8±0.15°. The metal oxide-metal catalyst of the present application, the active component comprises an oxide of molybdenum and a first metal element (Ru and / or Cu), and the oxide of molybdenum contains MoO x (x is the molar ratio of O to Mo in the oxide of molybdenum, x<3, for example MoO2, Mo9O 26 , etc.).

[0038] The metal oxide-metal catalyst of the present application is used for carbon dioxide reduction reaction, and has the advantages of high CO2 conversion rate and high CO selectivity at a wider temperature (for example 300-600℃); especially for reverse water gas shift reaction, and has the advantages of high efficiency in catalyzing reverse water gas shift reaction, high activity, selectivity and stability at a lower temperature (for example 350-550℃).

[0039] The present application first discovers that when the mass ratio of molybdenum element to the first metal element in the catalyst is 1:0.20-0.66, the reaction of CO2 and H2 mainly obtains CO product, and the selectivity of CO is >90%; when the mass ratio of molybdenum element to the first metal element in the catalyst is more than 1:0.70, the methanation reaction of CO2 hydrogenation occurs, and especially when the mass ratio of molybdenum element to the first metal element in the catalyst is more than 1:0.85, the selectivity of CH4 product is 100%.

[0040] In the present application, the mass content of molybdenum element in the metal oxide-metal catalyst can be selected in a wide range in percentage by mass, which is exemplary but does not limit the scope of the present application, according to a preferred embodiment of the present application, the content of molybdenum element is 5-30wt% of the total mass of the catalyst, for example, 5wt%, 7wt%, 12wt%, 14wt%, 18wt%, 24wt%, 28wt%; more preferably, the molybdenum element accounts for 8-20wt% of the total mass of the catalyst, and within the above range, the catalyst has more excellent performance and stability.

[0041] In the present application, the mass content of the carrier in the metal oxide-metal catalyst can be selected in a wide range in percentage by mass, which is exemplary but does not limit the scope of the present application, according to a preferred embodiment of the present application, the content of the carrier is 50-94wt% of the total mass of the catalyst, for example, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt%, 93wt%; more preferably, the mass content of the carrier in the catalyst is 68-90wt%.

[0042] According to a preferred embodiment of the present application, in the catalyst, the particle size of the first metal particles is 3-10nm, which is beneficial to improve the selectivity of CO and the stability of the catalyst.

[0043] In the context of the present application specification, the particle size of the first metal particles is calculated according to the half-peak width of the characteristic diffraction peak of the first metal in the XRD pattern according to the Scherrer formula. The method for calculating the grain size of the catalyst is as follows: the grain size of the catalyst is estimated by the Scherrer formula, and the specific formula is as follows:

[0044] D=(K·λ) / (B·cosθ)

[0045] (K-Scherrer constant; λ-X-ray wavelength, 0.15406nm; B-half-height width of diffraction peak; θ-Bragg diffraction angle).

[0046] In the present invention, the presence of the first metal only in a single substance form is beneficial to improving the catalytic activity and stability of the catalyst. According to a preferred embodiment of the present invention, in the XRD spectrum of the catalyst, there is no diffraction peak at 2θ of 35.5±0.15°, 23.7±0.15° or 35.0±0.15°.

[0047] In the catalyst of the present invention, the molybdenum oxide does not contain MoO3, which is beneficial to improving the catalytic activity of the catalyst. According to a preferred embodiment of the present invention, in the XRD spectrum of the catalyst, there is no diffraction peak at 2θ of 27.3±0.15° (MoO3).

[0048] In the present invention, the types of carriers can be selected from a wide range, which is for exemplary purposes only, but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the carrier is an inert carrier, selected from one or more of carbon carriers and SiO2 carriers, preferably one or more of activated carbon, amorphous SiO2, SBA-15 molecular sieve and MCM-41 molecular sieve. In the embodiments of the present invention, amorphous SiO2 is used as an example to illustrate the advantages of the present invention, but the scope of the present invention is not limited to this.

[0049] A second aspect of the present invention provides a method for preparing a metal oxide-metal catalyst, the method comprising:

[0050] contacting a solution containing a molybdenum salt and a first metal source with a support, drying, calcining, and reducing in an atmosphere containing a reducing gas, wherein the first metal is selected from Ru and / or Cu;

[0051] The mass ratio of molybdenum element to the first metal element is 1:0.20-0.66;

[0052] The first metal is Ru, and the reduction conditions include: a reduction temperature of 400-600° C.;

[0053] The first metal is Cu, and the reduction conditions include: a reduction temperature of 300-450°C. The inventors have found that when the first metal is Ru, the first metal molybdate is reduced at 400-600°C to reduce the first metal to a single substance and partially reduce Mo oxide to obtain MoO x ,MoO x For example, MoO2, Mo9O 26 Etc. However, if MoO2 needs to be reduced to metallic element Mo, a higher temperature (for example, not less than 750°C) is required.

[0054] In the present invention, the reduction is carried out in an atmosphere containing a reducing gas. There is no particular limitation on the type and amount of the reducing gas. For example, the reduction can be carried out in an atmosphere containing hydrogen, preferably in a hydrogen atmosphere.

[0055] In the present application, when the temperature is higher than 600℃, MoO3 starts to be reduced to Mo element, and when the temperature reaches 800℃, MoO3 is basically reduced to Mo element. When the first metal is Ru, the reduction conditions include that the reduction temperature is 400-600℃, the first metal is reduced to element, and Mo oxide is partially reduced to MoO x For example, 420℃, 450℃, 480℃, 520℃, 550℃, 580℃; preferably 450-550℃; the reduction time is generally flexibly adjusted according to the temperature, etc., and the reduction time is generally 1-5h.

[0056] In the present application, when the first element is Cu, Mo and Cu exist in the form of CuMoO4 after calcination, and CuMoO4 is reduced to Cu and MoO x The temperature is in the range of 300-450℃, for example, 320℃, 350℃, 380℃, preferably 300-400℃; the reduction time is generally flexibly adjusted according to the temperature, etc., and the reduction time is generally 1-5h.

[0057] In the present application, the drying conditions are not particularly limited, and the conventional drying conditions in the art can be used, which are exemplary but do not limit the scope of the present application. According to one embodiment of the present application, the drying conditions include that the drying temperature is 100-120℃; the drying time can be determined according to actual needs, and preferably, the drying time is 8-16h.

[0058] In the present application, the calcination conditions are not particularly limited, and the exemplary conditions are described, but the present application is not limited thereto. According to one preferred embodiment of the present application, the calcination conditions include that the calcination temperature is 380-450℃, for example, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃; the calcination time can be determined according to actual needs, and preferably, the calcination time is 3-5h. In the present application, 400℃ calcination for 4h is used as an exemplary description of the advantages of the present application, but the present application is not limited thereto.

[0059] In the present application, the type of molybdenum salt can be selected in a wide range, and exemplary descriptions are provided, but the present application is not limited thereto. According to one preferred embodiment of the present application, the molybdenum salt is selected from one or more of ammonium molybdate, sodium molybdate, molybdic acid, molybdenum sulfate, molybdenum oxide and molybdenum complex. In the present application, ammonium molybdate is used as an exemplary description of the advantages of the present application, but the present application is not limited thereto.

[0060] In the present application, the type of first metal source can be selected in a wide range, and exemplary descriptions are provided, but the present application is not limited thereto. According to one preferred embodiment of the present application, the first metal source is selected from one or more of nitrate, chloride, acetate, phosphate, citrate and sulfate of the first metal element.

[0061] In the present application, the conditions of the contacting are not particularly limited, and can be determined by routine techniques in the art, and exemplary, but not limiting the scope of the present application, for example, the solution of the molybdenum-containing salt and the first metal source can be contacted with the carrier by impregnation, preferably, equal volume impregnation; the impregnation time is not particularly limited, as long as the active components are loaded on the carrier, and is generally 10-16 h.

[0062] In the present application, the solution of the molybdenum-containing salt and the first metal source contains polyhydric alcohol, and the amount of the polyhydric alcohol can be selected in a wide range, according to one preferred embodiment of the present application, the mass ratio of the metal elements to the polyhydric alcohol is 1:10-20, for example, can be 1:11, 1:13, 1:15, 1:17, 1:19, and in the present application, the mass ratio of the metal elements to the polyhydric alcohol is 1:15 as an exemplary illustration of the advantages of the present application, but the present application is not limited thereto. In the present application, the catalyst prepared by adding polyhydric alcohol to the solution of the molybdenum-containing salt and the first metal source is used for the reverse water gas shift reaction, which can improve the CO2 conversion rate and the CO selectivity.

[0063] In the present application, the polyhydric alcohol refers to C2-C6 dihydric alcohol or C3-C6 trihydric alcohol; according to one preferred embodiment of the present application, the polyhydric alcohol is selected from one or more of ethylene glycol, glycerol, hexanediol, 1,3-propanediol and 1,2-propanediol, and preferably is glycerol.

[0064] In the present application, the solution is used for impregnation, and the molybdenum-containing salt, the first metal source and optionally the polyhydric alcohol can be dissolved, and the type of the solvent is not particularly limited, and generally, the solvent is water.

[0065] The third aspect of the present application provides a metal oxide-metal catalyst prepared by the preparation method of the present application.

[0066] The fourth aspect of the present application provides an application of the metal oxide-metal catalyst of the present application in the carbon dioxide reduction reaction.

[0067] The fifth aspect of the present application provides a reverse water gas shift reaction method, which comprises: contacting CO2 with H2 in the presence of the catalyst of the present application. By using the metal oxide-metal catalyst of the present application, H2 and CO2 are simultaneously activated in the reverse water gas shift reaction, the CO selectivity is high, and the catalyst stability is good.

[0068] According to one preferred embodiment of the present application, the gas space velocity is 10-300 L·g -1 ·h -1 , for example, can be 10 L·g -1 ·h-1 , 20 L·g -1 ·h -1 , 40 L·g -1 ·h -1 , 80 L·g -1 ·h -1 , 100 L·g -1 ·h -1 , 150 L·g -1 ·h -1 , 200 L·g -1 ·h -1 , 250 L·g -1 ·h -1 , 300 L·g -1 ·h -1 , preferably 10-50 L·g -1 ·h -1 , and more preferably 15-30 L·g -1 ·h -1 . The present application is not limited to this.

[0069] In the present application, the contact conditions in the reverse water gas shift reaction are not particularly limited, and the conditions in the art can be used. According to an embodiment of the present application, the contact conditions include: the temperature is 300-600 ℃, for example, 300 ℃, 340 ℃, 370 ℃, 400 ℃, 440 ℃, 480 ℃, 520 ℃, 550 ℃, 580 ℃, preferably 400-550 ℃; the pressure is 0.1-2 MPa, for example, 0.1 MPa, 0.3 MPa, 0.8 MPa, 1.2 MPa, 1.5 MPa, 2 MPa, and the present application is not limited to this.

[0070] In the present application, the feed amount of CO2 and H2 can be selected in a wide range. According to a preferred embodiment of the present application, the volume ratio of CO2 to H2 is 1:1-4, and the present application is not limited to this.

[0071] In order to further understand the present application, the preferred embodiments of the present application are described below in conjunction with the examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present application, and are not a limitation on the claims of the present application.

[0072] In the present application, three parameters are mainly required for catalyst performance test, i.e. raw material conversion rate, product selectivity and product yield, and the specific calculation methods are as follows:

[0073] Conversion rate formula of CO2: X CO2 (%) = (CO 2in 2 out) / CO 2out 2 in 2in

[0074] CO selectivity formula: S CO (%) = CO out 2 out / (CO 2in 2 in - CO 2out 2 out)

[0075] CH4 selectivity formula: S CH4 (%) = CH 4out 4 out / (CO 2in 2 in - CO 2out 2 out) = 100% - S CO

[0076] Wherein, CO 2in 2 in and CO 2out 2 out are the CO2 volume flow rates at the inlet and the outlet respectively, CH 4out 4 out and CO out 2 out are the CH4 flow rate and CO flow rate at the outlet respectively, all in mL·min -1 -1, the reaction gas after water removal by condensing device enters the chromatographic analysis of its components, CO2 and CO are separated by Porapok-Q column, CH4 component is separated by 5A molecular sieve, and each component concentration is analyzed by TCD detector. Finally, the tail gas enters the soap film flowmeter to measure the total flow, and the total flow multiplied by each gas component concentration obtains the outlet gas flow value, i.e. CH 4out 4 out and CO out 2 out.

[0077] Example 1

[0078] (1) According to the mass ratio of metal molybdenum, metal ruthenium and carrier is 1:0.3:11.2, ammonium molybdate and ruthenium chloride are dissolved in water, and the amorphous SiO2 carrier is impregnated with the same volume; 110℃ drying for 12h, 400℃ calcination for 4h to obtain the precursor;

[0079] (2) The precursor is reduced at 450℃ for 2h under H2 atmosphere to obtain a metal oxide-metal catalyst.

[0080] The XRD pattern of the precursor is shown in Figure 1 , there is a diffraction peak at 2θ of 27.3°; it is shown that Mo exists in the form of MoO3; there are diffraction peaks at 2θ of 35.0° and 54.0°, which shows that Ru exists in the form of RuO2.

[0081] The XRD pattern of the catalyst is shown in Figure 2As shown in the XRD pattern of the catalyst, diffraction peaks exist at 2θ of 26.1° and 36.8°; it is indicated that the molybdenum oxide is partially reduced to MoO2; a diffraction peak exists at 2θ of 43.9°, indicating that the ruthenium oxide is reduced to metal element; the particle size of the metal ruthenium is 3.2 nm calculated according to the Scherrer formula.

[0082] Catalyst evaluation: under the condition of 500 ℃, 0.1 MPa, and space velocity of 15 L·g -1 ·h -1 The reverse water gas shift reaction was carried out under the condition that the feeding amount ratio of H2 to CO2 was 4:1. The evaluation results of the catalyst after the reaction of the catalyst for 100 h showed that the CO2 conversion rate was 42.8%, and the CO selectivity was 99.2%.

[0083] Example 2

[0084] (1) According to the mass ratio of metal molybdenum, metal copper, and carrier of 1:0.65:10.85, ammonium molybdate and copper nitrate were dissolved in water, and the same volume of the amorphous SiO2 carrier was impregnated; 110 ℃ drying for 12 h, and 420 ℃ calcination for 4 h to obtain a precursor;

[0085] (2) The precursor was reduced at 400 ℃ for 2 h under H2 atmosphere to obtain a metal oxide-metal catalyst.

[0086] The XRD pattern of the precursor is shown in Figure 3 The diffraction peaks exist at 2θ of 23.7° and 26.4°; it is indicated that Mo and Cu exist in the form of CuMoO4.

[0087] The XRD pattern of the catalyst is shown in Figure 4 As shown in the XRD pattern of the catalyst, diffraction peaks exist at 2θ of 26.1°, 40.5°, and 58.8°; it is indicated that the molybdenum oxide is partially reduced to MoO2; diffraction peaks exist at 2θ of 43.3°, 50.4°, and 74.1°, indicating that the copper oxide is reduced to metal copper, and the particle size of the metal copper is 8.5 nm calculated according to the Scherrer formula.

[0088] Catalyst evaluation: under the condition of 400 ℃, 0.1 MPa, and space velocity of 15 L·g -1 ·h -1 The reverse water gas shift reaction was carried out under the condition that the feeding amount ratio of H2 to CO2 was 4:1. The evaluation results of the catalyst after the reaction of the catalyst for 100 h showed that the CO2 conversion rate was 42.8%, and the CO selectivity was 99.2%.

[0089] Example 3

[0090] (1) According to the mass ratio of metal molybdenum, metal ruthenium and carrier 1:0.2:6.2, ammonium molybdate and ruthenium chloride are dissolved in water, and the amorphous SiO2 carrier is impregnated in the same volume; dried at 100 ℃ for 14 h and calcined at 380 ℃ for 5 h to obtain a precursor;

[0091] (2) The precursor is reduced at 550 ℃ for 2 h under H2 atmosphere to obtain a metal oxide-metal catalyst.

[0092] The XRD pattern of the catalyst is similar to that of Example 1, and the metal elemental particle size of ruthenium is calculated to be 3.5 nm according to the Scherrer formula.

[0093] Catalyst evaluation: The reverse water gas shift reaction is carried out at 550 ℃, 0.1 MPa, and a space velocity of 15 L·g -1 ·h -1 The feed ratio of H2 to CO2 is 4:1. The catalyst is evaluated after 100 h of reaction, and the results show that the CO2 conversion rate is 45.8%, and the CO selectivity is 99.8%.

[0094] Example 4

[0095] (1) According to the mass ratio of metal molybdenum, metal ruthenium and carrier 1:0.6:4, ammonium molybdate and ruthenium chloride are dissolved in water, and the amorphous SiO2 carrier is impregnated in the same volume; dried at 120 ℃ for 10 h and calcined at 430 ℃ for 3 h to obtain a precursor;

[0096] (2) The precursor is reduced at 550 ℃ for 2 h under H2 atmosphere to obtain a metal oxide-metal catalyst.

[0097] The XRD pattern of the catalyst is similar to that of Example 1, and the metal elemental particle size of ruthenium is calculated to be 6.5 nm according to the Scherrer formula.

[0098] Catalyst evaluation: The reverse water gas shift reaction is carried out at 450 ℃, 0.1 MPa, and a space velocity of 15 L·g -1 ·h -1 The feed ratio of H2 to CO2 is 4:1. The catalyst is evaluated after 100 h of reaction, and the results show that the CO2 conversion rate is 48.4%, and the CO selectivity is 96.1%.

[0099] Example 5

[0100] (1) According to the mass ratio of metal molybdenum, metal ruthenium and carrier 1:0.3:3.2, ammonium molybdate and ruthenium chloride are dissolved in water, and the amorphous SiO2 carrier is impregnated in the same volume; dried at 110 ℃ for 12 h and calcined at 400 ℃ for 4 h to obtain a precursor;

[0101] (2) The precursor is reduced under H2 atmosphere at 450℃ for 2h to obtain the metal oxide-metal catalyst.

[0102] The XRD pattern of the catalyst is similar to that of Example 1, and the metal elemental particle size of ruthenium is calculated to be 4.5nm according to the Scherrer formula.

[0103] Catalyst evaluation: The reverse water gas shift reaction is carried out at 500℃, 0.1MPa, and a space velocity of 15L·g -1 ·h -1 The feed ratio of H2 to CO2 is 4:1. The catalyst is evaluated after being reacted for 100h, and the results show that the CO2 conversion rate is 39.2%, and the CO selectivity is 98.5%.

[0104] Example 6

[0105] The catalyst is prepared according to the method of Example 1, except that the solution containing the molybdenum salt and the first metal source contains a polyol, specifically:

[0106] (1) According to the mass ratio of molybdenum metal, ruthenium metal, glycerol, and carrier of 1:0.3:19.5:11.2, ammonium molybdate, ruthenium chloride, and glycerol are dissolved in water, and the same volume of amorphous SiO2 carrier is impregnated; dried at 110℃ for 12h, and calcined at 400℃ for 4h to obtain the precursor;

[0107] (2) The precursor is reduced under H2 atmosphere at 450℃ for 2h to obtain the metal oxide-metal catalyst.

[0108] The XRD pattern of the catalyst is similar to that of Example 1, and the metal elemental particle size of ruthenium is calculated to be 3.0nm according to the Scherrer formula.

[0109] Catalyst evaluation: The reverse water gas shift reaction is carried out at 500℃, 0.1MPa, and a space velocity of 15L·g -1 ·h -1 The feed ratio of H2 to CO2 is 4:1. The catalyst is evaluated after being reacted for 100h, and the results show that the CO2 conversion rate is 39.2%, and the CO selectivity is 98.5%.

[0110] Example 7

[0111] The catalyst is prepared according to the method of Example 1, except that the catalyst evaluation temperature is 350℃; specifically:

[0112] (1) According to the mass ratio of molybdenum metal, ruthenium metal, and carrier of 1:0.3:11.2, ammonium molybdate and ruthenium chloride are dissolved in water, and the same volume of amorphous SiO2 carrier is impregnated; dried at 110℃ for 12h, and calcined at 400℃ for 4h to obtain the precursor;

[0113] (2) The precursor was reduced under H2 atmosphere at 450℃ for 2h to obtain the metal oxide-metal catalyst.

[0114] Catalyst evaluation: The catalyst was evaluated under the condition of 350℃, 0.1 MPa, space velocity of 15 L·g -1 ·h -1 , and the ratio of H2 to CO2 was 4:1. The results of the catalyst evaluation after 100h of reaction showed that the CO2 conversion rate was 30.8%, and the CO selectivity was 92.5%.

[0115] Comparative Example 1

[0116] (1) According to the mass ratio of metal molybdenum, metal ruthenium, and carrier of 1:0.3:11.2, ammonium molybdate and ruthenium chloride were dissolved in water, and the same volume of amorphous SiO2 carrier was impregnated; dried at 110℃ for 12h, and calcined at 400℃ for 4h to obtain a precursor;

[0117] (2) The precursor was reduced under H2 atmosphere at 350℃ for 2h to obtain the metal oxide-metal catalyst.

[0118] In the XRD pattern of the catalyst, diffraction peaks existed at 2θ of 26.0°, 37.0°, and 40.6°; indicating that the molybdenum oxide was partially reduced to MoO2; diffraction peaks existed at 2θ of 35.1° and 44°, indicating that the ruthenium oxide was partially reduced to ruthenium single element, and partially reduced to RuO2, and the particle size of the ruthenium single element was 6.2nm.

[0119] Catalyst evaluation: The catalyst was evaluated under the condition of 350℃, 0.1 MPa, space velocity of 15 L·g -1 ·h -1 , and the ratio of H2 to CO2 was 4:1. The results of the catalyst evaluation after 100h of reaction showed that the CO2 conversion rate was 30.8%, and the CO selectivity was 92.5%.

[0120] The catalyst in Comparative Example 1 was reduced at a lower temperature, and the reverse water gas shift reaction occurred at a lower reaction temperature. The ruthenium oxide could not be completely reduced to metal single element, and still maintained the form of ruthenium oxide. The results of Comparative Example 1 and Example 7 proved that the presence of the first metal in the form of metal single element in the catalyst significantly improved the performance of the catalyst.

[0121] Comparative Example 2

[0122] (1) According to the mass ratio of metal molybdenum, metal ruthenium, and carrier of 1:0.73:10.7, ammonium molybdate and ruthenium chloride were dissolved in water, and the same volume of amorphous SiO2 carrier was impregnated; dried at 110℃ for 12h, and calcined at 400℃ for 4h to obtain a precursor;

[0123] (2) H2 atmosphere, the precursor is reduced at 450℃ for 2h to obtain metal oxide-metal catalyst.

[0124] The XRD pattern of the catalyst is similar to that of Example 1, and the metal elemental particle size of ruthenium is calculated to be 8.2 nm according to the Scherrer formula.

[0125] Catalyst evaluation: under the conditions of 500℃, 0.1 MPa, space velocity 15 L·g -1 ·h -1 , the ratio of H2 and CO2 feed amount is 4:1, the reverse water gas shift reaction is carried out. The evaluation results of the catalyst after 100h reaction show that the CO2 conversion rate is 54.1%; the CO selectivity is 88.9%, and the CH4 selectivity is 11.1%. The above results prove that when the mass ratio of molybdenum element to the first metal in the catalyst exceeds 1:0.7, although the catalyst maintains good CO2 conversion rate and CO yield, but accompanied by the occurrence of methanation reaction.

[0126] Comparative Example 3

[0127] (1) According to the mass ratio of metal molybdenum, metal ruthenium and carrier is 1:0.3:11.2, ammonium molybdate and ruthenium chloride are dissolved in water, and the same volume of amorphous SiO2 carrier is impregnated; 110℃ drying for 12h, 400℃ calcination for 4h to obtain the precursor;

[0128] (2) H2 atmosphere, the precursor is reduced at 800℃ for 2h to obtain metal oxide-metal catalyst.

[0129] In the XRD pattern of the catalyst, there are diffraction peaks at 2θ of 40.6°, 43.9°, and there are no diffraction peaks at 26.0±0.15°, 36.9±0.15°, 40.6±0.15°, 58.8±0.15°; It shows that the bimetallic catalyst of Mo and Ru is obtained after reduction at 800℃, and the metal elemental particle size of ruthenium is calculated to be 14.2 nm according to the Scherrer formula.

[0130] Catalyst evaluation: under the conditions of 500℃, 0.1 MPa, space velocity 15 L·g -1 ·h -1 , the ratio of H2 and CO2 feed amount is 4:1, the reverse water gas shift reaction is carried out. The evaluation results of the catalyst after 100h reaction show that the CO2 conversion rate is 57.3%; the CO selectivity is 45.2%, and the CH4 selectivity is 54.8%.

[0131] Comparative Example 4

[0132] (1) According to the mass ratio of metal ruthenium to carrier of 1.3:11.2, the ruthenium chloride was dissolved in water and impregnated with amorphous SiO2 carrier in equal volume; the precursor was obtained by drying at 110℃ for 12h and calcining at 400℃ for 4h;

[0133] (2) The precursor was reduced at 450℃ for 2h under H2 atmosphere to obtain a metal oxide-metal catalyst.

[0134] In the XRD pattern of the catalyst, there was a diffraction peak at 2θ of 43.9°, indicating that the ruthenium oxide was reduced to metal element, and the metal element particle size of ruthenium was calculated to be 16nm according to the Scherrer formula.

[0135] Catalyst evaluation: the reverse water gas shift reaction was carried out at 500℃, 0.1MPa, space velocity of 15L·g -1 ·h -1 The evaluation results of the catalyst after 100h reaction showed that the CO2 conversion rate was 62.4%, the CO selectivity was 23.5%, and the CH4 selectivity was 76.5%. It was speculated that the Ru metal catalyst alone would catalyze the CO2 hydrogenation to CH4, but at a higher temperature of 500℃, the methanation reaction and the RWGS reaction were in a competitive relationship, and at this time, part of CO would be produced.

[0136] The preferred embodiments of the application are described in detail above, but the application is not limited thereto. Within the technical concept of the application, various simple modifications can be made to the technical solutions of the application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the application and fall within the protection scope of the application.

Claims

1. A metal oxide-metal catalyst characterized in that, The metal oxide-metal catalyst comprises a carrier and an active component supported on the carrier; The active component comprises an oxide of molybdenum and a first metal element; The first metal is selected from Ru and / or Cu; In the catalyst, the mass ratio of molybdenum element to the first metal element is 1:0.20-0.66; In the XRD pattern of the catalyst, there is at least one diffraction peak at 2θ of 26.0±0.15°, 36.9±0.15°, 40.6±0.15°, and 58.8±0.15°.

2. The catalyst according to claim 1, wherein, The content of molybdenum element is 5-30wt% of the total mass of the catalyst, preferably 8-20wt%; and / or The content of the carrier is 50-94wt% of the total mass of the catalyst, preferably 68-90wt%.

3. The catalyst according to claim 1 or 2, wherein, In the catalyst, the particle size of the first metal element is 3-10nm.

4. The catalyst according to any one of claims 1-3, wherein, In the XRD pattern of the catalyst, there is no diffraction peak at 2θ of 35.5±0.15°, 23.7±0.15°, or 35.0±0.15°.

5. The catalyst according to any one of claims 1-4, wherein, In the XRD pattern of the catalyst, there is no diffraction peak at 2θ of 27.3±0.15°.

6. The catalyst according to any one of claims 1-5, wherein, The carrier is selected from one or more of carbon carrier and SiO2 carrier, preferably one or more of activated carbon, amorphous SiO2, SBA-15 molecular sieve, and MCM-41 molecular sieve.

7. A process for the preparation of a metal oxide-metal catalyst, characterized in that, The preparation method of the catalyst comprises: contacting a solution containing a molybdenum-containing salt and a first metal source with a carrier, drying, calcining, and reducing under an atmosphere containing a reducing gas, the first metal being selected from Ru and / or Cu; The mass ratio of molybdenum element to the first metal element is 1:0.20-0.66; When the first metal is Ru, the reduction conditions include a reduction temperature of 400-600℃; When the first metal is Cu, the reduction conditions include a reduction temperature of 300-450℃.

8. The preparation method according to claim 7, wherein, The reduction is performed under an atmosphere containing hydrogen, preferably the atmosphere containing hydrogen is hydrogen; and / or When the first metal is Ru, the reduction conditions include a reduction temperature of 450-550℃; and / or a reduction time of 1-5h; and / or When the first metal is Cu, the reduction conditions include a reduction temperature of 300-400℃; and / or a reduction time of 1-5h.

9. The preparation method according to claim 7 or 8, wherein, The drying conditions include a drying temperature of 100-120℃; a drying time of 8-16h; and / or The calcination conditions include a calcination temperature of 380-450℃; and a calcination time of 3-5h.

10. The preparation method according to any one of claims 7-9, wherein, the molybdenum salt is selected from one or more of ammonium molybdate, sodium molybdate, molybdic acid, molybdenum sulfate, molybdenum oxide and molybdenum complexes; and / or the first metal source is selected from one or more of soluble salts of the first metal, preferably selected from one or more of nitrates, chlorides, acetates, phosphates, citrates and sulfates of the first metal.

11. The preparation method of any one of claims 7-10, wherein, the solution containing the molybdenum salt and the first metal source contains a polyol, and the mass ratio of the polyol to the total mass of the metal elements of the molybdenum salt and the first metal source is 1:10-20.

12. The method of making according to claim 11, wherein, the polyol is selected from C2-C6 diols and / or C3-C6 triols; preferably, the polyol is selected from one or more of ethylene glycol, glycerol, hexanediol, 1,3-propanediol and 1,2-propanediol.

13. The metal oxide-metal catalyst prepared by the preparation method of any one of claims 7-12.

14. The use of the metal oxide-metal catalyst of any one of claims 1-6 and 13 in a carbon dioxide reduction reaction.

15. A reverse water gas shift reaction method, characterized by, The method comprises: contacting CO2 with H2 in the presence of the metal oxide-metal catalyst of any one of claims 1-6 and 13.

16. The reaction method of claim 15, wherein, Gas hourly space velocity of 10-300 L.g -1 ·h -1 , preferably 10-50 L.g -1 ·h -1 ; and / or the volume ratio of the feed of CO2 to H2 is 1:1-4; and / or the contact conditions include a temperature of 300-600°C, preferably 400-550°C; and / or the pressure is 0.1-2 MPa.

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