Catalyst for catalyzing coupling of methane and carbon dioxide to prepare acetic acid as well as preparation method and application of catalyst

Abstract

The invention discloses a catalyst for catalyzing coupling of methane and carbon dioxide to prepare acetic acid as well as a preparation method and application of the catalyst. The catalyst comprises an indium oxide carrier and zinc oxide loaded on the indium oxide carrier, based on 100% of the mass of the catalyst, the indium oxide carrier accounts for 96-99 wt%, and the zinc oxide accounts for 1-4 wt%. According to the invention, a'zinc-indium 'double-activity catalyst is designed based on a catalyst design theory, the molecular inertness of methane and carbon dioxide is overcome respectively, and the conversion rate of acetic acid and the selectivity of acetic acid are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalyst preparation, in particular to a catalyst for catalyzing the coupling of methane and carbon dioxide to produce acetic acid, and a preparation method and application thereof. BACKGROUND

[0002] The research on the coupling of CH4 and CO2 is still an emerging field. With the help of CH4, the conversion of CO2 into high-energy-density fuels or high-value-added chemicals can reduce human dependence on traditional fossil fuels, while reducing the harmful effects of these two greenhouse gases.

[0003] It is difficult to prepare acetic acid directly from the reaction of CH4 and CO2 from a thermodynamic point of view (△G0=16.98 kcal / mol), and the reaction between the two has the disadvantages of low conversion of reactants, poor selectivity of products, and harsh reaction conditions. The stability of partially dehydrogenated CH4 and the activation of CO2 are two important parts of improving C-C coupling efficiency. Therefore, it is very difficult to design a catalytic system; the main challenge is to design a reasonable catalyst that can activate the C-H bond of stable CH4 molecules and convert CH4 and CO2 into C2 oxygen-containing compounds through a high-efficiency C-C coupling process on the catalyst. SUMMARY

[0004] The purpose of the present application is to provide a catalyst for catalyzing the coupling of methane and carbon dioxide to produce acetic acid, and a preparation method and application thereof.

[0005] The present application is based on the theory of catalyst design, and a "zinc-indium" dual-activity catalyst is designed to overcome the molecular inertness of methane and carbon dioxide. Among them, indium oxide provides a large number of oxygen vacancies for efficient adsorption and activation of carbon dioxide to overcome its chemical inertness. Further, zinc oxide is deposited and dispersed on the surface of the carrier, which provides a Zn-O acid-base pair for dissociative adsorption of methane molecules to achieve the activation thereof. On the other hand, the interaction between indium oxide and zinc oxide forms a large number of interface sites, which provides a reaction site for the subsequent C-C coupling reaction between the activated methane and carbon dioxide to generate acetic acid.

[0006] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0007] The present application provides a catalyst for catalyzing the coupling of methane and carbon dioxide to produce acetic acid, wherein the catalyst comprises: an indium oxide carrier, and zinc oxide loaded on the indium oxide carrier.

[0008] The indium oxide carrier accounts for 96wt%-99wt%, and the zinc oxide accounts for 1wt%-4wt%, based on 100% of the mass of the catalyst.

[0009] Another aspect of the present application provides a preparation method of the above catalyst, wherein the preparation method comprises:

[0010] The ZnO is prepared by deposition-precipitation method using Zn(NO3)2·6H2O and NaOH as the precursor and the precipitator respectively, and is loaded on the In2O3 carrier to obtain the catalyst.

[0011] In a preferred embodiment, the preparation method specifically comprises:

[0012] The In2O3 powder is dispersed in deionized water with the pH value adjusted to 7.5-10 by NaOH to form a suspension;

[0013] The solution containing Zn(NO3)2·6H2O is slowly injected into the suspension under stirring to react, and the pH value of the suspension is maintained at 7.5-10 by adding NaOH solution during the process;

[0014] After the reaction is completed, the reaction system is aged, and then the solid is separated and collected, washed with water, dried and calcined to obtain the catalyst.

[0015] In this preferred embodiment, preferably, the aging time is 3-12 hours. The aging can be carried out at room temperature.

[0016] In this preferred embodiment, preferably, the drying temperature is 60-110°C, and the drying time is 8-16 hours.

[0017] In this preferred embodiment, preferably, the calcination is carried out in air atmosphere; the calcination temperature is 350-550°C, and the calcination time is 2-4 hours.

[0018] In this preferred embodiment, the concentration of the NaOH solution can be exemplarily 0.1M, and the present application is not limited thereto, and the pH value of the system can be adjusted. The solution containing Zn(NO3)2·6H2O is obtained according to the required loading amount. The solution containing Zn(NO3)2·6H2O is slowly injected into the reaction system, for example, dropwise added, or slowly added drop by drop using a dropping funnel to control the flow rate, or injected using a syringe pump, and the injection rate can be, for example, 1mL / min.

[0019] According to the preparation method of the present application, preferably, the In2O3 carrier is prepared by precipitation method using In(NO3)3·xH2O and 25% NH3·H2O solution as the precursor and the precipitator respectively.

[0020] More preferably, the In2O3 carrier is obtained by the following steps:

[0021] The reaction is carried out by adding an excess of a precipitant into the precursor solution, and after the reaction is completed, the obtained white slurry is aged, and then the solid is separated and collected, washed with water, and dried and calcined to obtain the In2O3 powder.

[0022] In the preparation process of the In2O3 powder, preferably, the temperature of the aging is 60-100℃, and the time is 1-6 hours.

[0023] In the preparation process of the In2O3 powder, preferably, the temperature of the drying is 60-110℃, and the time is 8-16 hours.

[0024] In the preparation process of the In2O3 powder, preferably, the calcination is carried out in an air atmosphere; the temperature of the calcination is 300-400℃, and the time is 2-4 hours.

[0025] In still another aspect of the present application, the above catalyst is applied in the coupling of methane and carbon dioxide to prepare acetic acid.

[0026] According to the application of the present application, preferably, the coupling of methane and carbon dioxide to prepare acetic acid is carried out in a normal-pressure fixed-bed reactor or a high-pressure batch reactor.

[0027] According to the application of the present application, preferably, when carried out in the normal-pressure fixed-bed reactor, the reaction temperature is 400-500℃, the space velocity is 150-900 / h, and the feed molar ratio of methane to carbon dioxide is 0.5:1-1:1.

[0028] According to the application of the present application, preferably, when carried out in the high-pressure batch reactor, the reaction temperature is 250-275℃, the reaction pressure is 0.5-1.5 MPa, the reaction time is 2-14 h, and the feed molar ratio of methane to carbon dioxide is 1:1.

[0029] The present application is based on the theory of catalyst design, and a "zinc-indium" dual-activity catalyst is designed to overcome the molecular inertness of methane and carbon dioxide, respectively, and improve the conversion rate of acetic acid and the selectivity of acetic acid. The catalyst is successfully applied in the synthesis of acetic acid in a normal-pressure fixed-bed reactor and a high-pressure batch reactor; among them, in the application of the normal-pressure fixed-bed, the conversion rate is improved by more than ten times compared with the similar public literatures (New J. Chem., 2021, 45, 8978-8985; J. Phys. Chem. C., 2023, 127, 5841-5854), and the selectivity of the target product is maintained at more than 85%. The application of the high-pressure batch reactor further improves the conversion rate, and the selectivity of the target product is maintained at more than 99%.

[0030] The catalyst of the present application has the advantages of simple preparation method, low cost and high selectivity. The yield of acetic acid can reach 0.0156%, the selectivity of acetic acid in liquid phase product is close to 100%, and the conversion rate is higher than that of the same kind of reported literatures. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1a TEM image of the supported mass fraction 1% ZnO catalyst obtained in Example 1.

[0032] Figure 1b Elemental analysis image of the supported mass fraction 1% ZnO catalyst obtained in Example 1.

[0033] Figure 2a TEM image of the supported mass fraction 2% ZnO catalyst obtained in Example 2.

[0034] Figure 2b Elemental analysis image of the supported mass fraction 2% ZnO catalyst obtained in Example 2.

[0035] Figure 3 Hydrogen temperature programmed reduction image of the supported mass fraction 1%-4% ZnO catalyst in Example 5.

[0036] Figure 4 In-situ infrared detection image of the supported mass fraction 2% ZnO catalyst at 400℃ in Example 7.

[0037] Figure 5 Product identification gas chromatogram of the supported mass fraction 1% ZnO catalyst in Example 9.

[0038] Figure 6 XRD spectrum of the supported mass fraction 1% ZnO catalyst before and after reaction in Example 9.

[0039] Figure 7 Product identification gas chromatogram of the supported mass fraction 2% ZnO catalyst in Example 9.

[0040] Figure 8 XRD spectrum of the supported mass fraction 2% ZnO catalyst before and after reaction in Example 9. DETAILED DESCRIPTION

[0041] In order to more clearly illustrate the present application, the present application will be further described below in conjunction with preferred embodiments. Those skilled in the art should understand that the specific description below is illustrative rather than limiting, and should not limit the protection scope of the present application.

[0042] All numerical designations (e.g., temperatures, times, concentrations, and weights, etc., including ranges for each thereof) herein can be approximations, typically plus or minus 0.1 or 1.0, as appropriate. All numerical designations are understood to be preceded by the word "about."

[0043] In the following examples, the yield of acetic acid is calculated by the formula X = n 乙酸 / n 甲烷 x 100%. Where n 乙酸 is the molar yield of acetic acid as determined by gas chromatography external standard method, and n 甲烷 is the molar amount of methane as calculated by ideal gas state equation using initial pressure, temperature, and reactor volume.

[0044] The selectivity of acetic acid in the liquid phase products is calculated by the formula S = n 乙酸 / n 产物 x 100%. Where n 产物 is the molar amount of all liquid phase products as determined by gas chromatography external standard method, since no other products were observed in all examples of the present invention, and n 产物 is equal to n 乙酸 .

[0045] Example 1

[0046] This example provides a 1% mass fraction ZnO supported catalyst, the specific steps for preparation are as follows:

[0047] An excess of 25% NH3-H2O solution precipitant was added dropwise into the In(NO3)3-xH2O precursor solution, and then the resulting white slurry was aged at 80°C for one hour. The sample was then centrifuged and washed with deionized water several times. The resulting white solid was dried at 60°C for 12 hours, and then calcined in air at 350°C for 3 hours to obtain the In2O3 support powder.

[0048] Synthesized 1 g of In2O3 powder was dispersed in 80 mL of deionized water with a pH value of 8 adjusted by NaOH (0.1 M) at room temperature. Then, under vigorous stirring, 20 mL of solution containing 0.0458 g of Zn(NO3)2-6H2O was slowly injected (about 1 mL / min) into the resulting suspension. Throughout the preparation process, the pH value of the mixed suspension was maintained at about 8 by gradually injecting NaOH solution, and then the mixture was aged at room temperature for 3 hours. Finally, the solid was collected by centrifugation and washed with deionized water several times, followed by drying at 60°C for 12 hours and calcination in air at 450°C for 3 hours.

[0049] The TEM image of the resulting catalyst is shown in Figure 1. Figure 1aTEM image of the resulting catalyst is shown in FIG. 2; from the figure, clear catalyst particles can be seen; the elemental analysis of the resulting catalyst is shown in FIG. 3; from the figure, it can be clearly seen that the In, O, and Zn elements are uniformly distributed. Figure 1b

[0050] Example 2

[0051] This example provides a 2% mass fraction ZnO supported catalyst, the specific steps for preparation are as follows:

[0052] An excess of 25% NH3-H2O solution precipitant was dropped into the In(NO3)3-xH2O precursor solution, and then the obtained white slurry was aged at 80°C for one hour. The sample was then centrifuged and washed with deionized water multiple times. The obtained white solid was dried at 60°C for 12 hours, and then calcined in air at 350°C for 3 hours to obtain an In2O3 support powder.

[0053] The synthesized 1 g In2O3 powder was dispersed in 80 mL deionized water with a pH value of 8 adjusted by NaOH (0.1 M) at room temperature. Then, under vigorous stirring, a 20 mL solution containing 0.0916 g Zn(NO3)2-6H2O was slowly injected (about 1 mL / min) into the obtained suspension. During the entire preparation process, the pH value of the mixed suspension was maintained at about 8 by gradually injecting NaOH solution, and then the mixture was aged at room temperature for 3 hours. Finally, the solid was collected by centrifugation and washed with deionized water multiple times, followed by drying at 60°C for 12 hours and calcination in air at 450°C for 3 hours.

[0054] The TEM image of the resulting catalyst is shown in FIG. 2; from the figure, clear catalyst particles can be seen; the elemental analysis of the resulting catalyst is shown in FIG. 3; from the figure, it can be clearly seen that the In, O, and Zn elements are uniformly distributed. Figure 2a Figure 2b

[0055] Example 3

[0056] This example provides a 3% mass fraction ZnO supported catalyst, the specific steps for preparation are as follows:

[0057] An excess of 25% NH3-H2O solution precipitant was dropped into the In(NO3)3-xH2O precursor solution, and then the obtained white slurry was aged at 80°C for one hour. The sample was then centrifuged and washed with deionized water multiple times. The obtained white solid was dried at 60°C for 12 hours, and then calcined in air at 350°C for 3 hours to obtain an In2O3 support powder.

[0058] ​​​Synthesized 1 g of In2O3 powder was dispersed in 80 mL of deionized water adjusted to pH 8 with NaOH (0.1 M) at room temperature. Then, 20 mL of a solution containing 0.1374 g of Zn(NO3)2-6H2O was slowly injected (about 1 mL / min) into the resulting suspension under vigorous stirring. Throughout the preparation, the pH of the mixed suspension was kept around 8 by gradual injection of NaOH solution, and then the mixture was aged at room temperature for 3 hours. Finally, the solid was collected by centrifugation and washed several times with deionized water, followed by drying at 60 °C for 12 hours and calcination in air at 450 °C for 3 hours.

[0059] Example 4

[0060] This example provides a 4% mass fraction ZnO supported catalyst, the specific preparation steps are as follows:

[0061] An excess of 25% NH3-H2O precipitant solution was added to the In(NO3)3-xH2O precursor solution, and then the resulting white slurry was aged at 80 °C for one hour. Then the sample was centrifuged and washed several times with deionized water. The resulting white solid was dried at 60 °C for 12 hours, and then calcined in air at 350 °C for 3 hours to obtain an In2O3 support powder.

[0062] Synthesized 1 g of In2O3 powder was dispersed in 80 mL of deionized water adjusted to pH 8 with NaOH (0.1 M) at room temperature. Then, 20 mL of a solution containing 0.1374 g of Zn(NO3)2-6H2O was slowly injected (about 1 mL / min) into the resulting suspension under vigorous stirring. Throughout the preparation, the pH of the mixed suspension was kept around 8 by gradual injection of NaOH solution, and then the mixture was aged at room temperature for 3 hours. Finally, the solid was collected by centrifugation and washed several times with deionized water, followed by drying at 60 °C for 12 hours and calcination in air at 450 °C for 3 hours.

[0063] Example 5

[0064] The above-obtained 1% to 4% mass fraction ZnO supported catalysts were subjected to hydrogen temperature programmed reduction, the specific process being:

[0065] 100 mg of catalyst was pretreated in a flowing argon environment at 300 °C for one hour. After the pretreatment was completed and the temperature was lowered to room temperature, the gas was changed from argon to flowing 10% H2 / Ar (30 mL / min), and the temperature was gradually increased to 800 °C at a rate of 10 °C / min. During this process, the consumption of hydrogen was monitored online using a thermal conductivity detector (TCD).

[0066] The results obtained are as follows:Figure 3 The vertical coordinate TCD signal represents the hydrogen consumption, and the figure is used to detect the reduction degree of the catalyst at different temperatures to assist the activity test experiment at different reduction temperatures. Specifically, the reduction curve is divided into two regions: the region where the reduction temperature is lower than 400°C is due to the reduction of the oxygen species on the surface of the catalyst, which is beneficial to the generation of active oxygen vacancies on the surface of the catalyst; and the region higher than 400°C represents the bulk reduction of the catalyst, and the structure of the test catalyst is severely damaged. Therefore, in order to improve the reaction conversion rate by reduction operation, the selected reduction temperature should be less than 400°C, and all the reduction temperatures in the embodiments of the present application are 200°C.

[0067] Example 6

[0068] This embodiment provides a catalyst with a mass fraction of 2% ZnO, and the specific preparation steps are as follows:

[0069] An excess of 6% NH3·H2O solution precipitant is added dropwise into the In(NO3)3·xH2O precursor solution, and then the obtained white slurry is aged at 60°C for one hour. Then the sample is centrifuged and washed with deionized water several times. The obtained white solid is dried at 80°C for 8 hours, and then calcined in air at 300°C for 4 hours to obtain an In2O3 support powder.

[0070] Synthesized 1g of In2O3 powder is dispersed in 80mL of deionized water with a pH value of 7.5 adjusted by NaOH (0.1M) at room temperature. Then, under vigorous stirring, 20mL of a solution containing 0.0916g of Zn(NO3)2·6H2O is slowly injected (about 1mL / min) into the obtained suspension. During the entire preparation process, the pH value of the mixed suspension is maintained at about 7.5 by gradually injecting NaOH solution, and then the mixture is aged at room temperature for 6 hours. Finally, the solid is collected by centrifugation and washed with deionized water several times, followed by drying at 110°C for 8 hours and calcining in air at 350°C for 2 hours.

[0071] Example 7

[0072] The in-situ Fourier transform infrared test of the catalyst with a mass fraction of 2% ZnO obtained in Example 2 is carried out at 400°C, and the specific process is as follows:

[0073] 50mg of self-supporting catalyst sheet is placed in an in-situ cell and pretreated in a flowing argon environment at 400°C for one hour. After the pretreatment is completed, the background spectrum is recorded. Then, the gas is changed from argon to a 1:1 CH4 / CO2 mixed gas (5mL / min) flowing. During this process, the infrared spectrum of the catalyst surface at different reaction times is recorded by scanning as the gas switching time increases.

[0074] The results are as follows Figure 4 As shown, different curves correspond to different reaction times, and the ordinate absorbance characterizes the formation of intermediate species. (1556, 1505, 1451 cm⁻¹) -1 The corresponding bidentate, monodentate, and multidentate carbonates are located at 1545cm. -1 The corresponding bidentate acetate appears at the specified location. This attached figure is used to detect the formation of intermediate species on the catalyst surface at different reaction times to verify the occurrence of surface reactions. Specifically, in the initial reaction stage, due to the short gas mixing time, the reactant concentration in the in-situ tank is low, and the main species on the catalyst surface are carbonate species produced by CO2 adsorption. As reactants gradually accumulate in the in-situ tank, the peaks corresponding to carbonate species gradually decrease, and peaks corresponding to acetate species appear. This proves that a surface reaction process of carbonate to acetate occurred on the catalyst surface, and these acetates subsequently undergo hydrogenation and desorption to generate acetic acid products. This provides characterization evidence for the coupling of methane and carbon dioxide to produce acetic acid.

[0075] Example 8

[0076] This embodiment provides a 1% ZnO loading catalyst, and the specific preparation steps are as follows:

[0077] An excess of 10% NH3·H2O solution as a precipitant was added dropwise to the In(NO3)3·xH2O precursor solution, and the resulting white slurry was aged at 100°C for one hour. The sample was then centrifuged and washed repeatedly with deionized water. The resulting white solid was dried at 110°C for 16 hours and then calcined in air at 400°C for 4 hours to obtain In2O3 support powder.

[0078] 1 g of synthesized In₂O₃ powder was dispersed in 80 mL of deionized water with pH adjusted to 10 using 0.1 M NaOH at room temperature. Then, under vigorous stirring, 20 mL of a solution containing 0.0458 g of Zn(NO₃)₂·6H₂O was slowly added (approximately 1 mL / min) to the resulting suspension. Throughout the preparation process, the pH of the mixed suspension was maintained at approximately 10 by gradually adding NaOH solution. The mixture was then aged at room temperature for 12 hours. Finally, the solid was collected by centrifugation, washed repeatedly with deionized water, dried at 110 °C for 16 hours, and calcined in air at 550 °C for 4 hours.

[0079] Example 9

[0080] This embodiment provides a method for the catalytic coupling of methane and carbon dioxide to produce acetic acid, the specific steps of which are as follows:

[0081] The coupled reaction of methane and carbon dioxide to produce acetic acid is carried out in a 50 mL stainless steel high-pressure batch reactor. A typical procedure is as follows:

[0082] 50 mg of the 1% ZnO catalyst powder obtained in Example 1 was added to a high-pressure batch reactor, followed by the injection of an equal volume of a 1 MPa mixture of CO2 and CH4. The reaction was carried out at 275 °C with a stirring speed of 500 rpm for 6 hours. Afterward, the high-pressure batch reactor was cooled to room temperature, released to atmospheric pressure, and the liquid mixture was collected by water extraction followed by filtration. The product was quantified using a gas chromatograph equipped with an HP-INNOwax column and a flame ionization detector (FID). The yield of acetic acid was 0.0079%, and the selectivity for acetic acid in the liquid product was close to 100%.

[0083] Product identification gas chromatogram as shown Figure 5 As shown, the peak with a retention time of about 11 minutes is the acetic acid product peak.

[0084] The XRD patterns of the catalyst before and after the reaction are as follows: Figure 6 As shown, both the catalyst before and after the reaction are well matched with the cubic indium oxide standard card (JCPDS No. 06-0416); it can be seen that the catalyst maintains structural stability before and after the reaction.

[0085] Example 10

[0086] This embodiment provides a method for the catalytic coupling of methane and carbon dioxide to produce acetic acid, the specific steps of which are as follows:

[0087] The coupled reaction of methane and carbon dioxide to produce acetic acid is carried out in a 50 mL stainless steel high-pressure batch reactor. A typical procedure is as follows:

[0088] 50 mg of the 2% ZnO catalyst powder obtained in Example 2 was added to a high-pressure batch reactor, followed by the injection of an equal volume of a 1 MPa mixture of CO2 and CH4. The reaction was carried out at 275 °C with a stirring speed of 500 rpm for 6 hours. Afterward, the high-pressure batch reactor was cooled to room temperature, released to atmospheric pressure, and the liquid mixture was collected by water extraction followed by filtration. The product was quantified using a gas chromatograph equipped with an HP-INNOwax column and a flame ionization detector (FID). The yield of acetic acid was 0.0156%, and the selectivity for acetic acid in the liquid phase product was close to 100%. The gas chromatogram for product identification is shown below. Figure 7 As shown, the peak with a retention time of about 11 minutes is the acetic acid product peak.

[0089] The XRD patterns of the catalyst before and after the reaction are as follows: Figure 8The catalysts before and after the reaction can be well matched with the standard card of indium oxide cubic phase (JCPDS No. 06-0416); it can be seen that the catalysts before and after the reaction remain stable in structure.

[0090] Example 11

[0091] This embodiment provides a method for catalyzing the coupling of methane and carbon dioxide to produce acetic acid, and the specific steps are as follows:

[0092] The reaction of coupling methane and carbon dioxide to produce acetic acid is carried out in a 50 mL stainless steel high-pressure batch reactor. The typical procedure is as follows:

[0093] In the high-pressure batch reactor, 50 milligrams of the supported mass fraction 4% ZnO catalyst powder obtained in Example 4 is added, and then an equal volume of a 1.5 MPa CO2 and CH4 mixture is injected. The reaction is carried out at a temperature of 250°C, with a stirring speed of 500 revolutions per minute (rpm), for 14 hours. After that, the high-pressure batch reactor is cooled to room temperature, released to atmospheric pressure, and the liquid mixture is collected by water extraction and filtration. The product is quantified using a gas chromatograph equipped with an HP-INNOwax chromatographic column and a flame ionization detector (FID). The yield of acetic acid is 0.0059%, and the selectivity of acetic acid in the liquid phase product is close to 100%.

[0094] Example 12

[0095] This embodiment provides a method for catalyzing the coupling of methane and carbon dioxide to produce acetic acid, and the specific steps are as follows:

[0096] The reaction of coupling methane and carbon dioxide to produce acetic acid is carried out in a 50 mL stainless steel high-pressure batch reactor. The typical procedure is as follows:

[0097] In the high-pressure batch reactor, 50 milligrams of the supported mass fraction 3% ZnO catalyst powder obtained in Example 3 is added, and then an equal volume of a 0.5 MPa CO2 and CH4 mixture is injected. The reaction is carried out at a temperature of 250°C, with a stirring speed of 500 revolutions per minute (rpm), for 2 hours. After that, the high-pressure batch reactor is cooled to room temperature, released to atmospheric pressure, and the liquid mixture is collected by water extraction and filtration. The product is quantified using a gas chromatograph equipped with an HP-INNOwax chromatographic column and a flame ionization detector (FID). The yield of acetic acid is 0.0031%, and the selectivity of acetic acid in the liquid phase product is close to 100%.

[0098] Example 13

[0099] This embodiment provides a method for catalyzing the coupling of methane and carbon dioxide to produce acetic acid, and the specific steps are as follows:

[0100] The reaction of methane coupled with carbon dioxide to acetic acid was carried out in a fixed bed reactor at atmospheric pressure. The typical procedure was:

[0101] A fixed bed reactor was loaded with 200 mg of the catalyst powder of Example 6 supported with 2% mass fraction of ZnO, and then the sample was reduced by hydrogen at a temperature of 200°C for 1 h, and then switched to a mixture of CO2 and CH4 at a ratio of 1:1. The reaction was carried out at a temperature of 500°C, with a space velocity of 900 / h, and the liquid phase product was continuously collected by water extraction of the outlet gas stream. After 12 h of reaction, a liquid mixture was obtained by water extraction. The product was quantified using a gas chromatograph equipped with a HP-INNOWax chromatographic column and a flame ionization detector (FID). The yield of acetic acid was 0.0007%, and the selectivity of acetic acid in the liquid phase product was close to 100%.

[0102] Example 14

[0103] The present example provides a method for catalyzing the reaction of methane coupled with carbon dioxide to acetic acid, and the specific steps are as follows:

[0104] The reaction of methane coupled with carbon dioxide to acetic acid was carried out in a fixed bed reactor at atmospheric pressure. The typical procedure was:

[0105] A fixed bed reactor was loaded with 200 mg of the catalyst powder of Example 8 supported with 1% mass fraction of ZnO, and then the sample was reduced by hydrogen at a temperature of 200°C for 1 h, and then switched to a mixture of CO2 and CH4 at a ratio of 0.5:1. The reaction was carried out at a temperature of 400°C, with a space velocity of 150 / h, and the liquid phase product was continuously collected by water extraction of the outlet gas stream. After 12 h of reaction, a liquid mixture was obtained by water extraction. The product was quantified using a gas chromatograph equipped with a HP-INNOWax chromatographic column and a flame ionization detector (FID). The yield of acetic acid was 0.0003%, and the selectivity of acetic acid in the liquid phase product was close to 100%.

[0106] Obviously, the above examples of the present application are only examples for clearly illustrating the present application, and are not limitations on the embodiments of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art, and it is impossible to exhaust all embodiments here. Any obvious changes or variations derived from the technical solutions of the present application are still within the protection scope of the present application.

Claims

1. A catalyst for catalyzing carbon dioxide coupling of methane to acetic acid, wherein, The catalyst comprises: an indium oxide carrier, and zinc oxide loaded on the indium oxide carrier; The indium oxide carrier accounts for 96wt%-99wt%, and the zinc oxide accounts for 1wt%-4wt% based on 100% of the mass of the catalyst.

2. A process for the preparation of the catalyst of claim 1 wherein, The preparation method comprises: The zinc oxide is prepared by a deposition-precipitation method with Zn(NO3)2·6H2O and NaOH as a precursor and a precipitator respectively, and is loaded on the In2O3 carrier to obtain the catalyst.

3. The production method according to claim 2, wherein, The preparation method specifically comprises: The In2O3 powder is dispersed in deionized water with the pH value adjusted to 7.5-10 by NaOH to form a suspension; Under stirring, a solution containing Zn(NO3)2·6H2O is slowly injected into the suspension to react, and the pH value of the suspension is kept at 7.5-10 by adding NaOH solution during the process; After the reaction is completed, the reaction system is aged, and then the solid is separated and collected, washed with water, dried and calcined to obtain the catalyst.

4. The production method according to claim 3, wherein The aging time is 3-12 hours.

5. The production method according to claim 3, wherein The drying temperature is 60-110°C, and the time is 8-16 hours.

6. The production method according to claim 3, wherein The calcination is performed in an air atmosphere; the calcination temperature is 350-550°C, and the time is 2-4 hours.

7. The production method according to claim 2, wherein The In2O3 carrier is prepared by a precipitation method with In(NO3)3·xH2O and 6%-25% NH3·H2O solution as a precursor and a precipitator respectively.

8. The production method according to claim 7, wherein The In2O3 carrier is obtained by the following steps: Excess precipitator is added dropwise into the precursor solution to react, and then the obtained white slurry is aged, and then the solid is separated and collected, washed with water, dried and calcined to obtain In2O3 powder.

9. The production method according to claim 8, wherein The aging temperature is 60-100°C, and the time is 1-6 hours.

10. The production method according to claim 8, wherein The drying temperature is 60-110°C, and the time is 8-16 hours.

11. The production method according to claim 8, wherein The calcination is performed in an air atmosphere; the calcination temperature is 300-400°C, and the time is 2-4 hours.

12. Use of the catalyst of claim 1 in the preparation of acetic acid from methane and carbon dioxide.

13. Use according to claim 12, wherein, The preparation of acetic acid from methane and carbon dioxide is performed in a normal-pressure fixed-bed reactor or a high-pressure batch reactor.

14. Use according to claim 13, wherein, When performed in the normal-pressure fixed-bed reactor, the reaction temperature is 400-500°C, the space velocity is 150-900 / h, and the feed molar ratio of methane to carbon dioxide is 0.5:1-1:

1.

15. The use according to claim 13, wherein, When performed in the high-pressure batch reactor, the reaction temperature is 250-275°C, the reaction pressure is 0.5-1.5 MPa, the reaction time is 2-14 h, and the feed molar ratio of methane to carbon dioxide is 1:1.

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