Preparation method for and use of molybdenum-sulfide-based catalyst

Abstract

The present invention belongs to the fields of chemistry and chemical engineering, and relates to a preparation method for and the use of a molybdenum-sulfide-based catalyst. The preparation method comprises: mixing a molybdenum source and a sulfur source until uniform, and roasting same under the protection of an inert atmosphere or a reducing atmosphere, so as to obtain a thin-layer two-dimensional molybdenum-sulfide-based catalyst. The thin-layer two-dimensional molybdenum-sulfide-based catalyst can be synthesized by using the method comprising successively subjecting catalyst precursors to "solid-solid" mixing and then to roasting provided by the present invention, and a thin-layer structure is beneficial to the exposure of more active surfaces, thereby allowing the catalyst to have a high activity for the preparation of methanol by means of carbon dioxide hydrogenation; and the high-temperature roasting performed in an inert atmosphere or a reducing atmosphere can accelerate the decomposition of the molybdenum source, the sulfur source and auxiliaries, thereby promoting the generation of the thin-layer two-dimensional molybdenum-sulfide-based catalyst.

Description

Preparation method and application of molybdenum sulfide-based catalyst Technical Field

[0001] The invention relates to a preparation method and application of a molybdenum sulfide-based catalyst, and belongs to the field of chemistry and chemical engineering. Background Art

[0002] Carbon dioxide (CO2) is the end product of the combustion of carbon-containing compounds. Its excessive emissions exacerbate the greenhouse effect and place tremendous pressure on the ecological environment. The efficient conversion and utilization of CO2 is a key approach to alleviating the energy crisis and the greenhouse effect, and it remains a research hotspot and challenge in the energy and chemical industry. Methanol is not only a clean fuel with extremely high energy density, but can also be converted into olefins and other high-value chemicals. In recent years, the process of producing methanol by reacting "green hydrogen" produced from renewable energy with CO2 has attracted increasing attention, and methanol is expected to become a major product in the resource utilization of CO2.

[0003] In the past few decades, a large number of high-efficiency catalysts for CO2 hydrogenation to methanol have been reported, mainly including Cu-based catalysts, In2O3-based catalysts, solid solution catalysts, and metal alloy catalysts. Recently, the application of MoS2-based catalysts in the field of CO2 catalytic conversion, especially CO2 hydrogenation to methanol, has received widespread attention. In 2021, Deng Dehui's team from the Dalian Institute of Chemical Physics and Wang Ye's team from Xiamen University collaborated for the first time to report the use of sulfur vacancy-rich few-layer MoS2 catalysts for low-temperature, high-efficiency, and long-life catalytic CO2 hydrogenation to methanol, opening up a new path for low-energy consumption and high-efficiency CO2 conversion and utilization.

[0004] Currently reported molybdenum sulfide-based catalysts for CO2 hydrogenation to methanol are mostly prepared using the solvothermal method. The molybdenum sulfide-based catalysts prepared by this method are of high purity, but the process has obvious limitations. First, the solvothermal method for preparing molybdenum sulfide-based catalysts requires high temperature and high pressure conditions, which are harsh, difficult to operate, and dangerous. It also requires high sealing requirements for the reactor and requires professional technical and equipment support. Second, the solvothermal method for preparing molybdenum sulfide produces harmful gases such as hydrogen sulfide that cannot be treated in a timely manner. When discharged into the air, it will cause great harm to the human body and the environment. At the same time, the resulting product needs to be washed, centrifuged, dried, and other post-processing, which increases the difficulty and time cost of the operation. In addition, the solvothermal method for preparing molybdenum sulfide-based catalysts requires a large amount of solvent, as well as expensive equipment and facilities, resulting in high costs. These shortcomings limit the large-scale preparation of molybdenum sulfide-based catalysts and hinder the pace of CO2 resource utilization. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method and application of a molybdenum sulfide-based catalyst, which is prepared by a "solid-solid" mixed calcination method. The method has the advantages of low reaction pressure, no need for solvents, no need for post-treatment, timely treatment of harmful gases generated in the process, and easy large-scale preparation. It significantly improves the safety, economy, environmental protection and simplicity of the preparation process of the molybdenum sulfide-based catalyst, and is expected to greatly promote the industrial application of molybdenum sulfide-based catalysts in the field of CO2 hydrogenation.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] On one hand, the present invention provides a method for preparing a molybdenum sulfide-based catalyst. A molybdenum source and a sulfur source are mixed to obtain a catalyst precursor. The catalyst precursor is calcined under the protection of an inert atmosphere or a reducing atmosphere to obtain a thin-layer two-dimensional molybdenum sulfide-based catalyst.

[0008] The number of layers of the thin-layer two-dimensional molybdenum sulfide-based catalyst of the present invention is 1 to 7 layers, and most of them are 3 to 5 layers.

[0009] Furthermore, in the above technical solution, the molybdenum source includes one or more of molybdenum trioxide, molybdenum dioxide, ammonium tetrathiomolybdate, ammonium molybdate, sodium molybdate, potassium molybdate, phosphomolybdic acid, sodium phosphomolybdate, potassium phosphomolybdate, molybdenum chloride, and molybdenum acetylacetonate; the sulfur source includes one or more of sulfur, sodium sulfide, potassium sulfide, thiourea, ammonium tetrathiomolybdate, thioacetamide, cysteine, methionine, and thiol.

[0010] Furthermore, in the above technical solution, the inert atmosphere includes one or more of argon, nitrogen, helium, and neon; and the reducing atmosphere includes one or more of hydrogen, carbon monoxide, and a mixture thereof with an inert gas.

[0011] Furthermore, in the above technical solution, the roasting temperature is 200-900° C., and the roasting time is 0.5-6 hours.

[0012] Furthermore, in the above technical solution, the molar ratio of molybdenum atoms in the molybdenum source to sulfur atoms in the sulfur source is 1:1.5 to 1:500.

[0013] Furthermore, in the above technical solution, the catalyst precursor also includes an auxiliary agent, and the auxiliary agent includes one or more of oxides, hydroxides, sulfides, phosphides, nitrides, chlorides, sulfates, nitrates, carbonates, and bicarbonates of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, zirconium, niobium, molybdenum, ruthenium, cadmium, indium, tin, and tungsten; the mass of the auxiliary agent accounts for 2% to 50% of the total mass of the catalyst.

[0014] Another aspect of the present invention provides an application of the molybdenum sulfide-based catalyst prepared by the above preparation method in a carbon dioxide hydrogenation reaction, wherein the reaction is carried out in one or more of a fixed bed reactor, a fluidized bed reactor, a moving bed reactor, a slurry bed reactor, and a tank reactor.

[0015] Furthermore, in the above technical solution, the catalyst is pretreated with H2-containing pretreated gas at 200-600°C for 1-6 hours before being used in the carbon dioxide hydrogenation reaction.

[0016] The beneficial effects of the present invention are:

[0017] (1) The present invention provides a method for synthesizing a thin-layer two-dimensional molybdenum sulfide-based catalyst by calcining a catalyst precursor using a solid-solid mixing process. The thin-layer structure facilitates the exposure of more active surface areas, resulting in high activity for the hydrogenation of carbon dioxide to methanol. High-temperature calcination under an inert or reducing atmosphere accelerates the decomposition of the molybdenum source, sulfur source, and additive, promoting the formation of a thin-layer two-dimensional molybdenum sulfide-based catalyst.

[0018] (2) The solid-solid mixed calcination method provided by the present invention for synthesizing thin-layer two-dimensional molybdenum sulfide-based catalysts requires only thorough solid-solid mixing of the catalyst precursors and then calcination at normal pressure under an inert or reducing atmosphere. This method is highly safe and requires no consumables. During the calcination process, the flowing atmosphere promptly removes the precursor pyrolysis products and by-products, maintaining a highly pure product without the need for any post-processing. This reduces operational difficulty while significantly reducing both raw material and time costs.

[0019] (3) Electron microscopy analysis showed that the number of layers of the synthesized thin-layer two-dimensional molybdenum sulfide-based catalysts ranged from 1 to 7, with most having 3 to 5 layers. The catalysts had a small number of layers and a high degree of dispersion. After hydrogen reduction pretreatment, a large amount of active surface was exposed, giving them high activity in the hydrogenation of carbon dioxide to methanol.

[0020] (4) The thin two-dimensional structure can reduce catalyst aggregation and deactivation. Therefore, the thin two-dimensional molybdenum sulfide-based catalyst provided by the present invention can be used as a catalyst for the hydrogenation of carbon dioxide to methanol, thereby avoiding catalyst sintering during the reaction process and improving catalyst stability.

[0021] (5) The preparation process of the molybdenum sulfide-based catalyst provided by the present invention is simple and controllable, and can be easily prepared on a large scale.

[0022] In summary, the thin-layer two-dimensional molybdenum sulfide-based catalyst provided by the present invention can achieve high activity and selectivity, and has good stability; the catalyst preparation method is safe and efficient, easy to prepare on a large scale, and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is an electron microscope image of catalysts Cat1, Cat2, and Cat3, a is Cat1, b is Cat2, and c is Cat3;

[0024] Figure 2 is a statistical diagram of the number of molybdenum sulfide layers of catalysts Cat1, Cat2, and Cat3, where a is Cat1, b is Cat2, and c is Cat3. DETAILED DESCRIPTION

[0025] The following examples illustrate the preparation method of the thin-layer two-dimensional molybdenum sulfide-based catalyst provided by the present invention and its reaction performance in the carbon dioxide hydrogenation to methanol reaction, but the present invention is not limited thereto.

[0026] Example 1

[0027] (1) Ammonium molybdate powder (Sinopharm Group, National Medicine Code: 10002318, CAS No.: 12054-85-2), thiourea powder (Sinopharm Group, National Medicine Code: 10022318, CAS No.: 62-56-6), and cadmium nitrate powder (Shanghai Aladdin Biochemical Technology Co., Ltd., Product No.: C102676, CAS No.: 10022-68-1) were fully mixed in a mass ratio of 4:8:1 to obtain a catalyst precursor;

[0028] (2) The catalyst precursor was transferred to an atmosphere calcining furnace and introduced into an argon atmosphere. The heating rate was set to 10°C / min, raised to 500°C and maintained for 2 hours. After the reaction was completed, the calcining furnace was cooled to room temperature, and the product was taken out to obtain Cat1.

[0029] Example 2

[0030] (1) Ammonium molybdate powder, thiourea powder, and zinc nitrate powder (Tianjin Damao Chemical Reagent Factory, No. 1704, CAS No. 10196-18-6) were fully mixed in a mass ratio of 2:4:1 to obtain a catalyst precursor;

[0031] (2) The catalyst precursor was transferred to an atmosphere calcining furnace and introduced into an argon atmosphere. The heating rate was set to 10°C / min, raised to 500°C and maintained for 2 hours. After the reaction was completed, the calcining furnace was cooled to room temperature, and the product was taken out to obtain Cat2.

[0032] Example 3

[0033] (1) Ammonium molybdate powder, thiourea powder, and indium nitrate powder (Shanghai Aladdin Biochemical Technology Co., Ltd., catalog number: I105870, CAS number: 207398-97-8) were fully mixed in a mass ratio of 2:4:1 to obtain a catalyst precursor;

[0034] (2) The catalyst precursor was transferred to an atmosphere calcining furnace and introduced into an argon atmosphere. The heating rate was set to 10°C / min, raised to 500°C and maintained for 2 hours. After the reaction was completed, the calcining furnace was cooled to room temperature, and the product was taken out to obtain Cat3.

[0035] Figure 1 is an electron microscope image of catalysts Cat1, Cat2, and Cat3. It can be seen that Cat1, Cat2, and Cat3 have high dispersion. Figure 2 is a statistical diagram of the number of molybdenum sulfide layers of catalysts Cat1, Cat2, and Cat3. At least 100 groups of molybdenum sulfide were counted for each catalyst. The layer statistics show that the number of molybdenum sulfide layers is between 1 and 7 layers, with most being 3 to 5 layers, which is a relatively small number of layers.

[0036] Example 4

[0037] (1) fully mixing ammonium molybdate powder, thiourea powder, indium nitrate powder, and zinc nitrate powder in a mass ratio of 4:8:1:1 to obtain a catalyst precursor;

[0038] (2) The catalyst precursor was transferred to an atmosphere calcining furnace and introduced into an argon atmosphere. The heating rate was set to 5°C / min, raised to 500°C and maintained for 3 hours. After the reaction was completed, the calcining furnace was cooled to room temperature, and the product was taken out to obtain Cat 4.

[0039] Example 5

[0040] (1) Ammonium molybdate powder, sulfur powder (Tianjin Komiou Chemical Reagent Co., Ltd., CAS No.: 7704-34-9), and cobalt hydroxide powder (Sinopharm Group, National Pharmaceutical No.: 20015726, CAS No.: 21041-93-0) were fully mixed in a mass ratio of 4:5:1:4 to obtain a catalyst precursor;

[0041] (2) The catalyst precursor was transferred to an atmosphere calciner and introduced into a hydrogen atmosphere. The temperature was raised to 500°C at a rate of 5°C / min and maintained for 4 hours. After the reaction was completed, the calciner was cooled to room temperature and the product was removed to obtain Cat5.

[0042] Example 6

[0043] (1) Ammonium molybdate powder, methionine powder (Shanghai Aladdin Biochemical Technology Co., Ltd., product number: F116840, CAS number: 112883-40-6), chromium sulfide powder (Shanghai Aladdin Biochemical Technology Co., Ltd., product number: C302581, CAS number: 12018-22-3), and cadmium oxide powder (Sinopharm Group, national medicine number: 10005560, CAS number: 1306-19-0) were fully mixed in a mass ratio of 4:5:1:1 to obtain a catalyst precursor;

[0044] (2) The catalyst precursor was transferred to an atmosphere calcining furnace and introduced into a helium atmosphere. The heating rate was set to 5°C / min, and the temperature was raised to 500°C and maintained for 5 hours. After the reaction was completed, the calcining furnace was cooled to room temperature, and the product was taken out to obtain Cat6.

[0045] Example 7

[0046] (1) Phosphomolybdic acid powder (Shanghai Aladdin Biochemical Technology Co., Ltd., product number: P432815, CAS number: 51429-74-4), cysteine ​​powder (Shanghai Aladdin Biochemical Technology Co., Ltd., product number: C108237, CAS number: 52-90-4), and zinc nitrate powder were fully mixed in a mass ratio of 500:1000:7 to obtain a catalyst precursor;

[0047] (2) The catalyst precursor was transferred to an atmosphere calcining furnace and introduced into an argon atmosphere. The heating rate was set to 5°C / min, raised to 500°C and maintained for 6 hours. After the reaction was completed, the calcining furnace was cooled to room temperature, and the product was taken out to obtain Cat7.

[0048] Example 8

[0049] (1) Molybdenum chloride powder (Shanghai Aladdin Biochemical Technology Co., Ltd., catalog number: M106510, CAS number: 10241-05-1), cysteine ​​powder, and ferric nitrate powder (Sinopharm Group, national medicine number: 80072718, CAS number: 7782-61-8) were fully mixed in a mass ratio of 40:80:23 to obtain a catalyst precursor;

[0050] (2) The catalyst precursor was transferred to an atmosphere calcining furnace and introduced into a nitrogen atmosphere. The heating rate was set to 5°C / min, raised to 500°C and maintained for 1 hour. After the reaction was completed, the calcining furnace was cooled to room temperature, and the product was taken out to obtain Cat8.

[0051] Comparative Example 1

[0052] Molybdenum disulfide synthesized by the solvothermal method (Nature Catalysis, 2021, 4, 242-250) was used as a comparison sample and recorded as Cat9.

[0053] Comparative Example 2

[0054] Commercial molybdenum disulfide (Xilong Scientific Co., Ltd., product number: 17300102, CAS number: 1317-33-5) was used as a comparative sample and recorded as Cat10.

[0055] Application Example 1

[0056] Weigh 0.2g of Cat1-10 catalyst with a particle size of 30-60 mesh and load it into a fixed bed reactor. Then introduce a mixed gas flow of 10% H2 and 90% N2 with a volume fraction of 10%. -1 g -1 Under the conditions of , the catalyst was pretreated by heating to 300 °C for 1 h, and then the temperature was lowered to 30 °C; the atmosphere was switched to a mixed gas of CO2 and H2, where the volume ratio of H2 to CO2 was 3:1, the pressure was increased to 50 bar, and the reaction space velocity was 3000 mL h -1 g -1 The temperature was raised to 180°C for the CO2 hydrogenation to methanol reaction. The reaction products were analyzed online using a gas chromatograph, with TCD and FID detectors performing qualitative and quantitative analyses, respectively. Specific reaction performance is listed in Table 1.

[0057] Table 1 Catalyst performance evaluation results

[0058] As shown in Table 1, the molybdenum sulfide-based catalyst provided by the present invention exhibits high activity in the CO2 hydrogenation to methanol reaction, while commercial molybdenum sulfide has little catalytic activity in this reaction. Compared to a solvothermal molybdenum sulfide-based catalyst, the CO2 conversion and methanol selectivity of both catalysts are similar.

[0059] However, in terms of process, as shown in Table 2, compared with the solvent thermal method, the "solid-solid" mixed calcination method of the present invention for preparing molybdenum sulfide-based catalysts has mild reaction conditions, high safety, and low requirements for reaction equipment; the operation difficulty is low, the process is short, and the process takes less time; no other consumables are required except for the protective atmosphere, and the cost is low; the pollutants generated in the process can be treated in a timely manner, and the process has little harm to the environment and human body.

[0060] Table 2 Comparison between “solid-solid” mixed roasting method and traditional solvent thermal method

[0061] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the scope defined in the claims. Other variations or modifications may be made based on the above description. Obvious variations or modifications derived therefrom shall remain within the scope of protection of the present invention.

Claims

1. A method for preparing a molybdenum sulfide-based catalyst, characterized in that: The molybdenum source and the sulfur source are mixed to obtain a catalyst precursor, and the catalyst precursor is calcined under the protection of an inert atmosphere or a reducing atmosphere to obtain a thin-layer two-dimensional molybdenum sulfide-based catalyst.

2. The preparation method according to claim 1, characterized in that: The molybdenum source includes one or more of molybdenum trioxide, molybdenum dioxide, ammonium tetrathiomolybdate, ammonium molybdate, sodium molybdate, potassium molybdate, phosphomolybdic acid, sodium phosphomolybdate, potassium phosphomolybdate, molybdenum chloride, and molybdenum acetylacetonate; The sulfur source includes one or more of sulfur, sodium sulfide, potassium sulfide, thiourea, ammonium tetrathiomolybdate, thioacetamide, cysteine, methionine, and mercaptan.

3. The preparation method according to claim 1, characterized in that: The inert atmosphere includes one or more of argon, nitrogen, helium and neon; the reducing atmosphere includes one or more of hydrogen, carbon monoxide and a mixture thereof with an inert gas.

4. The preparation method according to claim 1, characterized in that: The calcination temperature is 200-900° C., and the calcination time is 0.5-6 hours.

5. The preparation method according to claim 1, characterized in that: The molar ratio of the molybdenum atoms in the molybdenum source to the sulfur atoms in the sulfur source is 1:1.5 to 1:

500.

6. The preparation method according to claim 1, characterized in that: The catalyst precursor further includes an additive, and the additive includes one or more of oxides, hydroxides, sulfides, phosphides, nitrides, chlorides, sulfates, nitrates, carbonates, and bicarbonates of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, zirconium, niobium, molybdenum, ruthenium, cadmium, indium, tin, and tungsten; The mass of the auxiliary agent accounts for 2% to 50% of the total mass of the catalyst.

7. Use of a molybdenum sulfide-based catalyst prepared by the preparation method according to any one of claims 1 to 6 in a carbon dioxide hydrogenation reaction, characterized in that: The reaction is carried out in one or more of a fixed bed reactor, a fluidized bed reactor, a moving bed reactor, a slurry bed reactor, and a tank reactor.

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