Indium-loaded ZnCo2O4 spinel composite catalyst as well as preparation method and application thereof

Abstract

The invention discloses an indium-loaded ZnCo2O4 spinel composite catalyst as well as a preparation method and application thereof, and relates to the technical field of hydrogenation catalysts. The indium-loaded ZnCo2O4 spinel composite catalyst comprises a ZnCo2O4 spinel carrier and an active component In, wherein the active component In is loaded on the ZnCo2O4 spinel carrier; in / (Zn + Co + In) is equal to 1-40% by mole percent. The indium-loaded ZnCo2O4 spinel composite catalyst is uniform in active component distribution and high in active site density, can improve the methanol selectivity and ensure the CO2 conversion rate in the process of catalyzing CO2 hydrogenation to synthesize methanol, and has the characteristics of good heat resistance, sintering resistance and strong stability. When the catalyst is used for catalyzing CO2 hydrogenation to synthesize methanol under the reaction condition of 270 DEG C, the CO2 conversion rate reaches 14.99%, and the methanol selectivity reaches 90%.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogenation catalysts, and more specifically, to an indium-loaded ZnCo2O4 spinel composite catalyst and a preparation method and application thereof. Background Art

[0002] CO2 is not only a greenhouse gas, but also an important source of carbon. Carbon dioxide in the atmosphere can be collected through carbon capture, carbon sequestration, carbon storage and other methods, and directly applied to environmental protection processing, chemical production, supercritical applications and other fields. By combining with renewable hydrogen energy, CO2 can be converted into energy chemicals such as CO, methane, methanol, etc. through photocatalysis, electrocatalysis and thermal catalysis, realizing the resource utilization of CO2. The energy efficiency of photocatalysis is low and the cost of electrocatalysis is high. In contrast, thermal catalysis has the advantages of cleanliness, high efficiency and high economy, and has a high prospect for industrial application.

[0003] Thermal catalytic hydrogenation of carbon dioxide to methanol has high economic value. This reaction is a reaction in which one CO2 molecule and three H2 molecules generate one methanol molecule and one water molecule at 200-300 degrees Celsius and high pressure. There are multiple side reactions at the same time. The reaction formula is as follows:

[0004] CO2+3H2→CH3OH+H2O ΔH° 298K =-49.7 kJ / mol; ΔG° 298K =3.8kJ / mol CO2+4H2→CH4+2H2O ΔH° 298K =-165.0 kJ / mol; ΔG° 298K =-113.5kJ / mol CO2+H2→CO+H2O ΔH° 298K =41.2 kJ / mol; ΔG° 298K =28.6 kJ / mol

[0005] At the same time, the reverse water gas reaction (RWGS) is an endothermic reaction, which will compete with the methanol synthesis reaction under high temperature conditions. Therefore, the reaction energy barrier and the occurrence of side reactions limit the efficiency of thermal catalytic carbon dioxide hydrogenation to methanol. Moreover, during the reaction process, H2 and CO2 need to be adsorbed and activated. Therefore, the design and synthesis of thermal catalysts with high activity, high stability and high selectivity is the key issue in realizing the synthesis of methanol from carbon dioxide hydrogenation.

[0006] Existing methanol catalysts mainly include copper-based, precious metal, Zn-Zr solid solution and In2O3-based catalysts. Copper-based catalysts have high activity but low selectivity; precious metal catalysts have high methanol selectivity and strong ability to decompose hydrogen, but low CO2 conversion rate; Zn-Zr solid solution catalysts have high stability, but also have the problem of low CO2 conversion rate. In the methanol synthesis reaction, indium oxide can form oxygen vacancies through reduction, optimize the adsorption of CO2, promote the hydrogenation reaction of CO2, and reduce the reaction energy barrier, showing excellent catalytic performance.

[0007] In order to further improve the catalytic reaction activity, through literature research, we know that spinel-type (AB2O4) metal oxides have a precise coordination structure, in which the A position is a tetrahedral configuration and the B position is an octahedral configuration. Generally, the B position is more easily exposed and is usually a highly efficient catalytic active site. It can maintain charge balance through the deviation of the valence state of the cation and the formation of vacancies. It has strong redox reaction catalytic activity and CO2 adsorption capacity, and has been applied in biomass conversion reactions. Patent CN113976126 A applies the spinel phase structure to the catalyst for hydrogenation of carbon dioxide to methanol. The spinel phase catalysts with AB2O4, Cu / AB2O4 or Pd / AB2O4 structures are studied. The selectivity of catalytic methanol reaches 70-90%, but its CO2 conversion rate is only 8.1-13%, and the space-time yield needs to be improved. At present, the research on supported spinel phase methanol catalysts mainly focuses on Cu or Pd, and there is no report on spinel methanol catalysts supported by In. Summary of the invention

[0008] The purpose of the present invention is to overcome the defects and shortcomings of existing methanol catalysts and provide an indium-loaded ZnCo2O4 spinel composite catalyst with good heat resistance, sintering resistance and strong stability; it can catalyze the conversion of CO2 into CH3OH in the hydrogenation reaction, and has high methanol selectivity and CO2 conversion rate, and high space-time yield.

[0009] Another object of the present invention is to provide a method for preparing an indium-loaded ZnCo2O4 spinel composite catalyst.

[0010] Another object of the present invention is to provide the use of the above-mentioned indium-loaded ZnCo2O4 spinel composite catalyst in catalyzing CO2 hydrogenation to synthesize methanol.

[0011] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0012] The present invention protects an indium-loaded ZnCo2O4 spinel composite catalyst, comprising a ZnCo2O4 spinel carrier and an active component In loaded on the ZnCo2O4 spinel carrier;

[0013] In terms of mole percentage, In / (Zn+Co+In)=1-40%.

[0014] In the preparation of the indium-loaded ZnCo2O4 spinel composite catalyst of the present invention, the molar ratio of indium (In), cobalt (Co) and zinc (Zn) elements is controlled to adjust the incorporation of In into and occupation of the tetrahedral sites (Co) of the ZnCo2O4 spinel. 2+ ) and octahedral sites (Co 3+ ) site, reducing (Co 2+ ) / (Co 3+ ) ratio; more oxygen vacancies can be generated, significantly improving the selectivity for CH3OH. The active components of the composite catalyst are evenly distributed, and the active site density is high. In the process of catalyzing CO2 hydrogenation to synthesize methanol, a high CO2 conversion rate can be obtained, while ensuring high methanol selectivity, thereby improving the yield, and having the characteristics of good heat resistance, anti-sintering and strong stability.

[0015] In some embodiments, in terms of molar percentage, In / (Zn+Co+In)=4-30%, preferably 10-30%, more preferably 20-30%, and further preferably 23-27%.

[0016] It should be noted that the general formula of spinel structure is AB2O4, wherein A is a divalent cation and B is a trivalent cation. In the ZnCo2O4 spinel of the present invention, A is Zn 2+ Occupies tetrahedral sites, B is Co 3+ Occupies octahedral sites, but the molar ratio of Zn:Co may not be strictly 1:2; when the amount of zinc at the tetrahedral sites is insufficient, Co 2+ Occupies tetrahedral sites.

[0017] The molar ratio of Zn to Co in the ZnCo2O4 spinel of the present invention is a key parameter, and Zn / (Zn+Co) is 10% to 33%, so as to ensure that the Zn in the formed ZnCo2O4 spinel is all in the tetrahedral coordination site. In this way, when In is loaded, it can be ensured that In first enters the octahedral coordination site of the spinel and then enters the tetrahedral coordination site of the spinel.

[0018] Preferably, in terms of molar percentage, Zn / (Zn+Co) in the ZnCo2O4 spinel carrier is 10-20%, and more preferably, Zn / (Zn+Co) is 12-15%.

[0019] The present invention provides a method for preparing an indium-loaded ZnCo2O4 spinel composite catalyst, comprising the following steps:

[0020] S1, preparing a metal salt aqueous solution with In salt, Co salt and Zn salt, adding a precipitant to carry out precipitation reaction, filtering and drying to obtain a metal mixture;

[0021] S2, calcining the metal mixture at 400-800° C. for 2-24 h in an oxidizing gas atmosphere to obtain an indium-supported ZnCo2O4 spinel catalyst.

[0022] Optionally, the Co salt used is one or more of nitrate, acetate, halide or sulfate.

[0023] Optionally, the Zn salt used is one or more of nitrate, acetate, halide or sulfate.

[0024] Optionally, the In salt used is one or more of nitrate, acetate, halide or sulfate.

[0025] Optionally, the precipitant used is one or more of ammonia water, ammonium carbonate, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide or potassium hydroxide.

[0026] Optionally, the drying temperature is 60 to 130° C., and the drying time is 4 to 24 hours.

[0027] In some embodiments, in step S1, the total concentration of metal ions in the metal salt aqueous solution is 0.01-2 mol / L.

[0028] In some embodiments, in step S1, the precipitant is prepared into a precipitant aqueous solution and then added into the system, the dropping speed is 1-5 mL / min, and the concentration of the precipitant in the precipitant aqueous solution is 0.01-2 mol / L.

[0029] Preferably, the molar ratio of the precipitant to the metal ion is (2-3):1, preferably (2.3-2.5):1.

[0030] In some embodiments, in step S1, in molar ratio, Zn / (Zn+Co)=10-33%, In / (Zn+Co+In)=1-40%.

[0031] In some embodiments, in step S1, the precipitation reaction temperature is 50-90°C, the pH value is 6-10, and the reaction time is 1-4h. Preferably, the precipitation reaction temperature is 60-80°C, more preferably 65-75°C; preferably, the precipitation reaction pH value is 7-10; preferably, the reaction time is 1.5-3h.

[0032] Optionally, in step S2, the calcination is static calcination or flowing atmosphere calcination.

[0033] Optionally, the oxidizing gas atmosphere is air and / or oxygen.

[0034] Preferably, the calcination temperature is 450-550° C., and the calcination time is 2.5-3.5 h.

[0035] The invention protects the application of an indium-loaded ZnCo2O4 spinel composite catalyst in catalyzing CO2 hydrogenation to synthesize methanol.

[0036] In some embodiments, the reaction temperature of the catalytic CO2 hydrogenation to methanol is 230-330°C, preferably 250-290°C.

[0037] In some of the embodiments, the pressure of catalytic CO2 hydrogenation to methanol is 3 to 7 MPa.

[0038] In some embodiments, the composite catalyst has a particle size distribution range of 40 to 80 meshes.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The invention provides an indium-loaded ZnCo2O4 spinel composite catalyst. Based on the structural properties of the ZnCo2O4 spinel, the ZnCo2O4 spinel has good adsorption of CO2, thereby improving the CO2 conversion rate. Indium loaded on the ZnCo2O4 spinel can improve the methanol selectivity. The molar ratio of the In, Co and Zn elements is further controlled, so that the composite catalyst not only has a higher oxygen vacancy concentration, but also has a uniform distribution of active components and a high density of active sites, significantly improving the selectivity for methanol, improving the space-time yield, and making the composite catalyst have the characteristics of good heat resistance, sintering resistance and strong stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Transmission electron microscope (TEM) images of the composite catalysts prepared in Examples 4-6 of the present invention and Comparative Example 1; the right image is a partial enlarged image of the left image.

[0042] Figure 2 The Raman spectra of the composite catalysts prepared in Examples 1-6 and Comparative Example 1 of the present invention are shown.

[0043] Figure 3 The XRD spectra of the composite catalysts prepared in Examples 1-6 and Comparative Example 1 of the present invention are shown in FIG. Figure 3 A is the XRD spectrum of the newly prepared catalyst; Figure 3 B is the XRD spectrum of the catalyst after reduction.

[0044] Figure 4The nitrogen adsorption and desorption curves of the composite catalysts prepared in Examples 1-6 and Comparative Example 1 of the present invention are shown in FIG. Figure 4 A is the nitrogen adsorption-desorption curve; Figure 4 B is the pore size distribution diagram.

[0045] Figure 5 The catalytic activity comparison diagram of the composite catalyst prepared in Examples 1-6 of the present invention and Comparative Example 1 is shown. Figure 5 A is a comparison diagram of methanol selectivity of catalysts with different indium loadings; Figure 5 B is a comparison chart of CO2 conversion rate and methanol yield of catalysts under different indium loading amounts.

[0046] Figure 6 The XPS O1s graphs of the composite catalysts prepared in Examples 1-6 and Comparative Example 1 of the present invention are shown. DETAILED DESCRIPTION

[0047] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0048] Example 1

[0049] A method for preparing an indium-loaded ZnCo2O4 spinel composite catalyst comprises the following steps:

[0050] (1) Weigh 13.5 mmol Co(NO3)2·6H2O, 2 mmol Zn(NO3)2·6H2O, and 0.8 mmol In(NO3)2·6H2O to prepare 100 mL of a metal salt aqueous solution and place it in a 500 mL beaker; also weigh 39.2 mmol (NH4)2CO3 as a precipitant to prepare 100 mL of an ammonium carbonate aqueous solution.

[0051] (2) adding the ammonium carbonate solution dropwise to the metal salt aqueous solution at 70° C. under stirring conditions, with a dropping speed of 3 mL / min and a stirring speed of 600 r / min. After the ammonium carbonate solution is consumed, a precipitated mother liquor is obtained and aged at 70° C. for 2 h, cooled, naturally filtered, washed with deionized water for 3 times, filtered by suction, and the obtained filter cake is dried at 110° C. for 4 h to obtain a metal mixture;

[0052] (3) The metal mixture was calcined at 500° C. for 3 h in an air atmosphere to obtain a spinel catalyst, which was recorded as Co-Zn-In5%. The catalyst was pressed into tablets, crushed, and 40-80 meshes were selected for subsequent performance testing.

[0053] Example 2

[0054] A method for preparing an indium-loaded ZnCo2O4 spinel composite catalyst, which is different from Example 1 in that: the metal salt aqueous solution includes 13.5 mmol Co(NO3)2·6H2O, 2 mmol Zn(NO3)2·6H2O, and 1.7 mmol In(NO3)2·6H2O;

[0055] The precipitant is 41.1mmol (NH4)2CO3;

[0056] The obtained indium-loaded ZnCo2O4 spinel composite catalyst is recorded as Co-Zn-In10%.

[0057] Example 3

[0058] A method for preparing an indium-loaded ZnCo2O4 spinel composite catalyst, which is different from Example 1 in that: the metal salt aqueous solution includes 13.5 mmol Co(NO3)2·6H2O, 2 mmol Zn(NO3)2·6H2O, and 2.7 mmol In(NO3)2·6H2O;

[0059] The precipitant is 43.8mmol (NH4)2CO3;

[0060] The obtained indium-loaded ZnCo2O4 spinel composite catalyst is recorded as Co-Zn-In15%.

[0061] Example 4

[0062] A method for preparing an indium-loaded ZnCo2O4 spinel composite catalyst, which is different from Example 1 in that: the metal salt aqueous solution includes 13.5 mmol Co(NO3)2·6H2O, 2 mmol Zn(NO3)2·6H2O, and 3.88 mmol In(NO3)2·6H2O;

[0063] The precipitant is 46.5mmol (NH4)2CO3;

[0064] The obtained indium-loaded ZnCo2O4 spinel composite catalyst is recorded as Co-Zn-In20%.

[0065] Example 5

[0066] A method for preparing an indium-loaded ZnCo2O4 spinel composite catalyst, which is different from Example 1 in that: the metal salt aqueous solution includes 13.5 mmol Co(NO3)2·6H2O, 2 mmol Zn(NO3)2·6H2O, and 5.17 mmol In(NO3)2·6H2O;

[0067] The precipitant is 49.6mmol(NH4)2CO3;

[0068] The obtained indium-loaded ZnCo2O4 spinel composite catalyst is recorded as Co-Zn-In25%.

[0069] Example 6

[0070] A method for preparing an indium-loaded ZnCo2O4 spinel composite catalyst, which is different from Example 1 in that: the metal salt aqueous solution includes 13.5mmol Co(NO3)2·6H2O, 2mmol Zn(NO3)2·6H2O, and 6.65mmol In(NO3)2·6H2O;

[0071] The precipitant is 53.2mmol(NH4)2CO3;

[0072] The obtained indium-loaded ZnCo2O4 spinel composite catalyst is recorded as Co-Zn-In30%.

[0073] Comparative Example 1

[0074] A method for preparing a ZnCo2O4 spinel composite catalyst, which is different from Example 1 in that: the metal salt aqueous solution includes 13.5 mmol Co(NO3)2·6H2O and 2 mmol Zn(NO3)2·6H2O;

[0075] The precipitant is 37.5mmol (NH4)2CO3;

[0076] The obtained indium-loaded ZnCo2O4 spinel composite catalyst is recorded as Co-Zn.

[0077] Performance Testing

[0078] 1. TEM characterization

[0079] The composite catalysts prepared in Examples 4-6 and Comparative Example 1 were characterized by transmission electron microscopy (TEM). Figure 1 shown.

[0080] The results show that the composite catalyst contains the lattice structures of ZnCo2O4(311), (400), (220) and (222), proving that the composite catalyst prepared in the present invention forms a ZnCo2O4 spinel structure.

[0081] In addition, the lattice structure of In2O3(222) can be seen in the Co-Zn-In30% composite catalyst, while the lattice structure of In2O3 is not found in the sample with a molar amount of In less than 30%, indicating that when the indium loading is less than 30%, the indium enters the coordination site of the ZnCo2O4 spinel. When the indium loading reaches 30%, the coordination site of the ZnCo2O4 spinel can no longer accept indium ions, and the indium loading in the ZnCo2O4 spinel reaches saturation.

[0082] 2. Raman spectroscopy characterization

[0083] The composite catalysts prepared in Examples 1-6 and Comparative Example 1 were subjected to Raman spectroscopy analysis. The results are as follows: Figure 2 shown.

[0084] The results show that the ZnCo2O4 catalyst is mainly composed of five peaks at 181, 456, 500, 601, 647 cm -1 , these five peaks represent Co 2+ The triple degenerate peak (F 1 2g ), double degenerate peak (E g ), Co 3+ The triple degenerate peak (F 2 2g ) and the single degenerate peak (A g ). In the composite catalyst, with the increase of In loading, the five peaks of ZnCo2O4 shifted to higher wavenumbers regularly until the molar amount of In reached 30%, and the shift stopped; indicating that the loading of In2O2 did not destroy the structure of ZnCo2O4.

[0085] By analyzing F 1 2g / F 2 2g The tetrahedral sites (Co 2+ ) and octahedral sites (Co 3+ ). With the increase of In molar amount, the ratios obtained by integration and comparison of corresponding peaks are: 28, 20, 17.6, 17, 14, 13. This indicates that on the surface detectable by Raman spectroscopy, with the increase of In loading, more indium enters the tetrahedral site.

[0086] 3. XRD characterization

[0087] The composite catalysts prepared in Examples 1-6 and Comparative Example 1 were characterized by X-ray diffractometer (XRD). The obtained XRD patterns are as follows: Figure 3 shown.

[0088] The catalyst was reduced in a 10% volume fraction H2 / Ar atmosphere at 350°C for 2 hours at a flow rate of 20 mL / min to obtain the XRD pattern of the reduced catalyst. Figure 3 As shown in B.

[0089] from Figure 3 A It can be seen that the XRD peak of the ZnCo2O4 catalyst is completely consistent with (PDF#23–1390). The peak in the Co-Zn-InX% catalyst also shows (PDF#23–1390), indicating that the loading of In did not completely change or destroy the structure of ZnCo2O4. With the increase of In loading, the peak of ZnCo2O4 becomes wider and shifts to high and low angles. This may be due to the fact that indium (In 3+ ) ionic radius (approximately ) is greater than cobalt (Co 3+ ) ionic radius (approximately ), the incorporation of indium leads to lattice expansion. When the In loading is greater than 20%, the XRD characteristic peaks of In2O2 can be seen (PDF#26–0469).

[0090] from Figure 3 B shows the XRD spectrum of the catalyst after reduction; the obvious difference from the newly prepared one is that the XRD peak of ZnCo2O4 in each group of catalysts becomes weaker, and the XRD peak of CoO appears at the same time.

[0091] After catalyst reduction, Co 3+ Reduction to Co 2+ , which will cause the XRD peak of ZnCo2O4 spinel catalyst to weaken or disappear. This change is more obvious on ZnCo2O4 spinel, but it can be observed in the two sets of XRD spectra with loading of 25% and 30% that Co 2+ The peak of becomes suddenly smaller than that of the previous components, and the peak of ZnCo2O2 spinel is retained, which can further illustrate that the indium oxide that did not enter the interior of the spinel is distributed on the surface or around the ZnCo2O4 spinel in the form of mixed oxides, which plays a protective role for the ZnCo2O4 spinel during the reduction process.

[0092] 4. Nitrogen adsorption and desorption test characterization

[0093] The composite catalysts prepared in Examples 1-6 and Comparative Example 1 were subjected to nitrogen adsorption and desorption tests. The results are as follows: Figure 4 shown.

[0094] from Figure 4It can be seen that the In-loaded composite catalyst is improved in specific surface area, pore capacity and pore size compared to the ZnCo2O4 catalyst. The specific surface area of ​​the Co-Zn-In20% catalyst is the largest. When the In loading exceeds 25%, both the specific surface area and pore size begin to decrease. This change before the In2O2 loading is 20% may be due to the entry of In into the ZnCo2O4 lattice. When the In loading exceeds the limit that the ZnCo2O4 lattice can accommodate, it may exist in the form of mixed oxides.

[0095] 5. Catalytic activity test

[0096] Experimental method: The composite catalysts prepared in Examples 1-6 and Comparative Example 1 were taken as experimental samples. 0.1 g of the catalyst sample was mixed with 0.9 g of quartz sand and then loaded into a reactor.

[0097] Experimental instruments: a tubular fixed-bed reactor with an inner diameter of 9 mm, an online gas chromatograph (PANNA A60, China) equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID).

[0098] Before the test, the catalyst was pretreated (reduced) at 350° C. and 10% by volume H 2 / Ar atmosphere at a flow rate of 30 mL / min for 2 hours.

[0099] Then, carbon dioxide is hydrogenated to produce methanol. The reaction conditions are as follows: pressure P = 5.0 MPa, temperature T = 290 ° C, V (H2) / V (CO2) / V (N2) = 4:1:1, gas hourly space velocity GHSV = 10.28 l·g cat -1 ·h -1 .

[0100] The outlet flow of the reactor was maintained at 150°C and immediately analyzed by an online gas chromatograph equipped with TCD and FID. The CO2 conversion (X, %), product selectivity (S, %) and space-time yield (STY, g MeOH ·g cat -1 ·h -1 ), the test results are as follows Figure 5 And as shown in Table 2.

[0101] Among them, TCD uses an Agilent packed column of 2m×3.175mm, while FID uses a PLOT Q capillary column of 30m×0.53mm×20um. TCD is used to analyze CO2, N2 and CO, while FID is used to analyze alcohols, hydrocarbons and other carbon-containing products.

[0102] Taking N2 as the standard, the calculation formula is as follows:

[0103]

[0104] Table 1 Correction factors

[0105]

[0106] Among them, [CO2] in is the amount of CO2 at the reactor inlet, [CO2] out is the amount of CO2 at the reactor outlet, f represents the correction factor of each substance (as shown in Table 1), and A represents the peak area of ​​each substance.

[0107] Table 2

[0108]

[0109]

[0110] from Figure 5 A and Table 1 show that under the reaction conditions, the methane selectivity of the ZnCo2O4 catalyst of Comparative Example 1 is 99%. In the Co-Zn-InX% catalysts of Examples 1-6, in addition to methane, the reaction products also include CH3OH and CO. As the In loading increases, the methane selectivity decreases, while the CH3OH selectivity increases.

[0111] from Figure 5 B and Table 1 show that the CO2 conversion rate of ZnCo2O4 in Comparative Example 1 is 85%, which should be related to its unique spinel chemical structure. The CO2 conversion rate in the Co-Zn-InX% catalysts of Examples 1-6 is reduced to 13.9-19.22%, and the CO2 conversion rate reaches a maximum of 19.22% when Co-Zn-In25%, with a space-time yield of

[0112] The Co—Zn—In 25% of the embodiment was tested at 250-310° C. according to the above catalytic activity test method. The results are shown in Table 3.

[0113] Table 3

[0114]

[0115] The results show that the Co-Zn-In25% catalyst of the present invention has the highest catalytic activity at 270°C, with a methanol selectivity of 90% and a space-time yield of

[0116] 6. XPS characterization

[0117] The composite catalysts prepared in Examples 1-6 and Comparative Example 1 were subjected to XPS testing. The results are as follows: Figure 6 shown.

[0118] Figure 6 The O1s XPS spectrum shows three peaks: the adsorbed oxygen peak at 533.4 eV, the oxygen vacancy peak (O v ), and lattice oxygen (Olatt) at about 529.7 eV. (O v / O v + Olatt) as an approximate measure of the oxygen vacancy concentration.

[0119] The results show that the Co-Zn-In25% catalyst has the highest oxygen vacancy content and excellent catalytic performance. The order of oxygen vacancy concentration is: Co-Zn-In25%>Co-Zn-In30%>Co-Zn>Co-Zn-In20%>Co-Zn-In10%.

[0120] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An indium-loaded ZnCo2O4 spinel composite catalyst, characterized in that: It comprises a ZnCo2O4 spinel carrier and an active component In loaded on the ZnCo2O4 spinel carrier; In terms of mole percentage, In / (Zn+Co+In)=1-40%.

2. The indium-supported ZnCo2O4 spinel composite catalyst according to claim 1, characterized in that: In terms of mole percentage, In / (Zn+Co+In)=4-30%.

3. The indium-supported ZnCo2O4 spinel composite catalyst according to claim 1 or 2, characterized in that: In terms of mole percentage, In / (Zn+Co+In)=20-30%.

4. The indium-supported ZnCo2O4 spinel composite catalyst according to claim 1, characterized in that: In terms of molar percentage, in the ZnCo2O4 spinel carrier, Zn / (Zn+Co) is 10 to 33%.

5. A method for preparing the indium-supported ZnCo2O4 spinel composite catalyst according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, preparing a metal salt aqueous solution with In salt, Co salt and Zn salt, adding a precipitant to carry out precipitation reaction, filtering and drying to obtain a metal mixture; S2, calcining the metal mixture at 400-800° C. for 2-24 h in an oxidizing gas atmosphere to obtain an indium-supported ZnCo2O4 spinel catalyst.

6. The method for preparing the indium-supported ZnCo2O4 spinel composite catalyst according to claim 5, characterized in that: In step S1, the total concentration of metal ions in the metal salt aqueous solution is 0.01-2 mol / L.

7. The method for preparing the indium-supported ZnCo2O4 spinel composite catalyst according to claim 5, characterized in that: In step S1, the temperature of the precipitation reaction is 50-90° C., the pH value is 6-10, and the reaction time is 1-4 hours.

8. The method for preparing the indium-supported ZnCo2O4 spinel composite catalyst according to claim 5, characterized in that: In step S2, the oxidizing gas atmosphere is air and / or oxygen.

9. Use of the indium-loaded ZnCo2O4 spinel composite catalyst according to any one of claims 1 to 4 in catalyzing CO2 hydrogenation to synthesize methanol.

10. The use according to claim 9, characterized in that: The reaction temperature of the catalytic CO2 hydrogenation to methanol is 230-330°C.

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