Catalyst for catalytic synthesis gas direct conversion to prepare ethanol and its preparation method and application

Abstract

The application discloses a catalyst for directly preparing ethanol by catalytic synthesis gas, which is composed of a carrier, an active component supported on the carrier and an auxiliary agent, wherein the active component is Mo2C, and the auxiliary agent is metal M1 and metal M2; the metal M1 is a combination of any one of Mn, La and Ce and K, and the metal M2 is Co or Ni; the carrier is a carbon carrier; the weight ratio of metal Mo to the carrier is 10-50%, and the molar ratio of any one of Mn, La and Ce, K, Mo and metal M2 is (0.05-0.1):(0.05-0.15):(0.3-0.8):1. Meanwhile, the application also discloses a preparation method of the catalyst and application of the catalyst in synthesis gas for preparing ethanol. The catalyst has a simple preparation process, and when used in synthesis gas for preparing ethanol, the selectivity of total alcohol and target product ethanol is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of ethanol preparation, and in particular relates to a catalyst for catalyzing the direct conversion of synthesis gas into ethanol, and a preparation method and application thereof. Background Art

[0002] Ethanol is an important bulk chemical raw material, high-quality liquid fuel and liquid additive, and is widely used in energy, chemical, pharmaceutical and other fields.

[0003] Ethanol is a high-quality liquid fuel. Its chemical energy is comparable to that of gasoline, and its sulfur and ash contents are low, making it less harmful to the human body. It is considered one of the best fuels for replacing and conserving gasoline. Ethanol can also be added to gasoline in any proportion. Ethanol is also a fundamental bulk chemical raw material, widely used in the chemical, food, daily chemical, and pharmaceutical industries. Ethanol-based processing routes offer a richer range of products than methanol-based routes, resulting in higher-value derivatives and greater atom economy. Ethanol can be used to produce not only bulk chemicals such as ethylbenzene, styrene, and ethylene, but also bulk chemicals and fine chemicals such as esters, ketones, and higher-carbon alcohols. It can also be used as a hydrogen source in fuel cells, offering enormous potential as a chemical platform compound.

[0004] Ethanol production methods include grain fermentation, indirect ethylene hydration, direct ethylene hydration, acetaldehyde hydrogenation, dimethyl ether carbonylation to methyl acetate hydrogenation, and direct synthesis from synthesis gas. Although fermentation is the primary ethanol production method, it is increasingly constrained by limited raw material supply. Ethylene hydration consumes large quantities of ethylene, a key chemical raw material, and is also subject to supply constraints. Acetaldehyde hydrogenation, which first produces acetaldehyde through ethylene oxidation, requires additional production steps and equipment, resulting in higher production costs. However, the carbon-based chemical route for ethanol production undoubtedly holds promising prospects.

[0005] The hydrogenation of syngas to ethanol via the methanol-dimethyl ether-methyl acetate route has been commercialized, but this technical route requires a lengthy process. Therefore, developing a direct syngas-to-ethanol conversion method is of great significance, but large-scale production has not yet been achieved, primarily due to the lack of catalysts suitable for industrial production. Therefore, developing high-performance, low-cost catalysts remains a key research priority for direct syngas-to-ethanol conversion.

[0006] Catalysts for direct syngas conversion to ethanol are generally classified into four categories: rhodium-based catalysts, modified methanol synthesis catalysts, modified Fischer-Tropsch synthesis catalysts, and molybdenum-based catalysts. Rhodium-based catalysts offer good ethanol selectivity, but the precious metal nature of Rh hinders their industrialization. Modified methanol catalysts primarily produce methanol and exhibit low selectivity for total alcohols. Modified Fischer-Tropsch synthesis catalysts exhibit a wide carbon number distribution of products and high hydrocarbon selectivity, but are susceptible to carbon deposition. Mo-based catalysts, however, have attracted considerable attention due to their excellent selectivity for low-carbon linear alcohols and sulfur tolerance.

[0007] Chinese patent CN 103764277 A discloses an alkali metal-modified RhMn-based catalyst, which catalyzes the conversion of synthesis gas to produce a large amount of organic oxygen-containing compounds such as acetic acid, ethanol, methyl formate, and methyl acetate, with methane being the main gaseous product. Chinese patent CN111420684A reports a potassium-promoted molybdenum selenide catalyst, which, after reduction, produces a molybdenum selenide catalyst at 340°C, 10 MPa, and 3000 h. -1 Under the conditions of V(H2):V(CO)=1, the CO conversion rate was 8.6%, and the selectivities (C mol%) for alcohols, hydrocarbons, and CO2 were 43.4, 26.3, and 30.3, respectively. The mass percentages of methanol, ethanol, propanol, and C3+ alcohols in the alcohols were 23.2, 54.6, 17.3, and 4.9, respectively. Although this catalyst exhibited excellent ethanol selectivity, the reaction pressure of 10 MPa was quite demanding. Chinese patent CN108325548A reports an alkali metal-promoted molybdenum sulfide catalyst for the synthesis of low-carbon alcohols from syngas. This catalyst exhibits excellent sulfur tolerance, but the product contains a high proportion of CO2 and a high proportion of methanol in the total alcohols, resulting in low carbon resource utilization and high carbon emissions. Synthesizing catalysts with both excellent total alcohol selectivity and ethanol selectivity remains a challenge in this field. Summary of the Invention

[0008] In view of the defects of the prior art, the present invention provides a catalyst for catalyzing the direct conversion of synthesis gas to produce ethanol, as well as its preparation method and application. When used for preparing ethanol from synthesis gas, the selectivity of total alcohol and ethanol is high.

[0009] A catalyst for catalyzing the direct conversion of synthesis gas to ethanol, comprising a support, an active ingredient supported on the support, and a promoter. The active ingredient is Mo2C, and the promoters are metal M1 and metal M2. The metal M1 is a combination of any one of Mn, La, and Ce and K, and the metal M2 is Co or Ni. The support is a carbon support. The weight ratio of the metal Mo to the support is 10-50%, and the molar ratio of any one of Mn, La, and Ce, K, metal M2, and Mo is (0.05-0.1):(0.05-0.15):(0.3-0.8):1. The catalyst is represented as M1M2Mo2C / support.

[0010] Preferably, the carrier is any one of activated carbon, carbon nanotubes, graphene, and carbon black.

[0011] The method for preparing the catalyst for catalyzing the direct conversion of synthesis gas to produce ethanol comprises the following steps:

[0012] (1) Add the carrier to a nitric acid solution, heat and reflux at 70-150°C for 3-14 hours, filter, wash with deionized water until the filtrate is neutral, dry, and grind to obtain a pretreated carrier;

[0013] (2) adding the support obtained in step (1) to an ammonium molybdate solution, stirring at room temperature until dry, and then drying and grinding to obtain a molybdenum-containing catalyst precursor;

[0014] (3) carbonizing the molybdenum-containing catalyst precursor under a carbonizing atmosphere by programmed temperature increase, then cooling the temperature to room temperature in the carbonizing atmosphere, purging with an inert gas, and introducing a passivation gas for passivation for 0.5-2 hours to obtain a catalyst precursor loaded with Mo2C;

[0015] (4) adding an ethanol solution or an aqueous solution of metal M2 to the catalyst precursor loaded with Mo2C, stirring at room temperature until dry, and then drying to obtain a catalyst precursor loaded with M2 and Mo2C;

[0016] (5) Adding an ethanol solution or an aqueous solution of metal M1 to the catalyst precursor loaded with M2 and Mo2C, stirring at room temperature until dry, then drying, calcining, tableting, and sieving through a 20-60 mesh sieve to obtain the catalyst.

[0017] Preferably, the carbonization is specifically carried out as follows: first, the temperature is raised to 300° C. at a heating rate of 5-10° C. / min, then the temperature is raised to 580-800° C. at a heating rate of 0.5-2° C. / min, and maintained for 1-3 hours.

[0018] Preferably, the carburizing atmosphere is an inert atmosphere, a hydrogen-containing atmosphere or a carbon-containing atmosphere;

[0019] The inert atmosphere is any one of nitrogen, helium or argon;

[0020] The hydrogen-containing atmosphere is 100% hydrogen, or is composed of ≥5% hydrogen by volume and the balance gas; the balance gas is any one of nitrogen, helium or argon;

[0021] The carbon-containing atmosphere is composed of 10-30% by volume of carbon-containing gas and the balance of hydrogen, and the carbon-containing gas is at least one of methane, ethane, ethylene, propane, propylene, butane, and butene.

[0022] Preferably, the passivation gas is composed of 0.1-3% by volume of oxygen and a balance gas, and the balance gas is any one of nitrogen, helium or argon.

[0023] Preferably, the concentration of the nitric acid solution is 5-10 mol / L, the ratio of the carrier to the nitric acid solution is 1 g: (10-20) mL; the concentration of molybdenum ions in the ammonium molybdate solution is 0.5-1 mol / L; the ion concentration of metal M2 in the ethanol solution or aqueous solution of metal M2 is 0.5-1 mol / L; the total ion concentration of metal M1 in the ethanol solution or aqueous solution of metal M1 is 0.1-0.5 mol / L.

[0024] Preferably, the drying in step (1) is carried out at 60-100°C for 8-12 hours; the drying in steps (2), (4) and (5) is carried out at 80-150°C for 6-10 hours; and the calcination is carried out at 300-450°C for 3-8 hours.

[0025] A method for directly converting syngas into ethanol, comprising loading a catalyst into a fixed-bed reactor, introducing a hydrogen-containing gas for reduction activation, adjusting the reaction temperature to 260-400°C, switching the introduction of syngas, and conducting the reaction at 3-6 MPa, wherein the molar ratio of H2 to CO in the syngas is 0.3-4, and the syngas space velocity is 1000-5000 h / min. -1 ; The catalyst is the catalyst according to claim 1.

[0026] Preferably, the reduction activation conditions are: reduction temperature 400-600 ° C, reduction time 5-8h, reduction pressure is normal pressure, and the space velocity of hydrogen-containing gas is 1000-5000h -1 ; The hydrogen-containing gas is 100% hydrogen, or is composed of hydrogen with a volume ratio of ≥5% and the balance gas; the balance gas is nitrogen, helium or argon.

[0027] In the present invention, the ethanol solution or aqueous solution of the metals M1 and M2 is a solution of nitrate, chloride or acetate of the corresponding metals.

[0028] Advantages of the present invention:

[0029] (1) The catalyst provided by the present invention has a simple and environmentally friendly preparation process, is a non-precious metal catalyst, has low cost, and is easy to prepare on a large scale;

[0030] (2) The catalyst provided by the present invention has high selectivity for total alcohol and target product ethanol when used for converting synthesis gas to ethanol. DETAILED DESCRIPTION

[0031] Example 1

[0032] 1. A catalyst for catalyzing the direct conversion of synthesis gas to ethanol, the catalyst comprising a carrier carbon black (CB, with a specific surface area of ​​80 m 2 / g), an active ingredient Mo2C supported on a carrier and an auxiliary agent, the auxiliary agent is a metal M1 and a metal M2, the metal M1 is La and K, and the metal M2 is Co; the weight ratio of metal Mo to the carrier is 10%, the molar ratio of La, K, Co, and Mo is 0.05:0.15:0.8:1, and the catalyst is expressed as KLaCoMo2C / CB.

[0033] 2. The preparation method of the catalyst comprises the following steps:

[0034] (1) The carrier was added to a 10 mol / L nitric acid solution at a ratio of 1 g:10 mL, heated under reflux at 150 °C for 3 h, filtered, washed with deionized water until the filtrate was neutral, dried at 60 °C for 12 h, and ground to obtain a pretreated carrier;

[0035] (2) adding the support obtained in step (1) to a 0.5 mol / L ammonium molybdate solution, stirring at room temperature until dry, then drying at 80° C. for 10 h and grinding to obtain a molybdenum-containing catalyst precursor;

[0036] (3) The molybdenum-containing catalyst precursor was first raised to 300°C at 10°C / min in a carbonizing atmosphere, then continued to be raised to 800°C at 2°C / min, and maintained at 800°C for 3 hours for carbonization, and then cooled to room temperature in the carbonizing atmosphere, purged with nitrogen, and passivated for 2 hours to obtain a catalyst precursor Mo2C / CB loaded with Mo2C; wherein the carbonizing atmosphere is 10% CH4 / 20% butane / 70% H2, and the passivating gas is 0.1% O2 / 99.9% N2, and the proportions are all volume ratios;

[0037] (4) adding a 0.5 mol / L aqueous solution of cobalt nitrate to the Mo2C-loaded catalyst precursor, stirring at room temperature until dry, and then drying at 150°C for 6 h to obtain a catalyst precursor CoMo2C / CB loaded with Co and Mo2C;

[0038] (5) An aqueous solution of potassium chloride and lanthanum chloride is added to the catalyst precursor loaded with Co and Mo2C, stirred at room temperature until dry, then dried at 150°C for 6 hours, calcined at 450°C for 3 hours, pressed into tablets, and sieved through a 20-40 mesh sieve to obtain the catalyst KLaCoMo2C / CB; wherein the total concentration of K and La in the aqueous solution of potassium chloride and lanthanum chloride is 0.5 mol / L.

[0039] 3. A method for directly converting syngas into ethanol: The catalyst is loaded into a fixed-bed reactor, and hydrogen-containing gas is introduced for reduction activation at 400°C and atmospheric pressure for 8 hours. The reaction temperature is then raised to 260°C, and syngas is introduced at a pressure of 3 MPa for reaction. The molar ratio of H2 to CO in the syngas is 4, and the syngas space velocity is 5000 h / min. -1 The hydrogen-containing gas is composed of 80% hydrogen by volume and the balance argon, and its space velocity is 5000h -1 After 2 h of reaction, the products were analyzed by gas chromatography. The results are shown in Table 1.

[0040] Example 2

[0041] 1. A catalyst for catalyzing the direct conversion of synthesis gas to ethanol, the catalyst comprising a support graphene (graphene, with a specific surface area of ​​685 m 2 / g), an active ingredient Mo2C supported on a carrier and an auxiliary agent, the auxiliary agent is a metal M1 and a metal M2, the metal M1 is Mn and K, and the metal M2 is Ni; the weight ratio of metal Mo to the carrier is 40%, the molar ratio of Mn, K, Ni, and Mo is 0.1:0.1:0.45:1, and the catalyst is expressed as KMnNiMo2C / Graphene.

[0042] 2. The preparation method of the catalyst comprises the following steps:

[0043] (1) Add the carrier graphene to 8 mol / L nitric acid solution at a ratio of 1 g: 20 mL, heat and reflux at 120 ° C for 9 h, filter, wash with deionized water until the filtrate is neutral, dry at 100 ° C for 8 h, and grind to obtain a pretreated carrier;

[0044] (2) adding the support obtained in step (1) to a 0.8 mol / L ammonium molybdate solution, stirring at room temperature until dry, then drying at 150° C. for 6 h, and grinding to obtain a molybdenum-containing catalyst precursor;

[0045] (3) The molybdenum-containing catalyst precursor was first raised to 300°C at 5°C / min in a carbonizing atmosphere, then continued to be raised to 700°C at 1.5°C / min, and maintained at 700°C for 1 hour for carbonization, and then cooled to room temperature in the carbonizing atmosphere, purged with helium, and passivated for 1 hour to obtain a Mo2C-loaded catalyst precursor Mo2C / Graphene; wherein the carbonizing atmosphere is 5% H2 / 95% Ar, and the passivating gas is 1% O2 / 99% He, and the proportions are all volume ratios;

[0046] (4) Adding 0.75 mol / L nickel chloride aqueous solution to the Mo2C-loaded catalyst precursor, stirring at room temperature until dry, and then drying at 80°C for 10 h to obtain NiMo2C / Graphene, a catalyst precursor loaded with Ni and Mo2C;

[0047] (5) Adding an ethanol solution of potassium acetate and manganese acetate to the catalyst precursor loaded with Ni and Mo2C, stirring at room temperature until dry, then drying at 80°C for 10 h, calcining at 300°C for 3 h, pressing into tablets, and sieving through a 40-60 mesh sieve to obtain the catalyst KMnNiMo2C / CB; wherein the total concentration of K and Mn in the ethanol solution of potassium acetate and manganese acetate is 0.1 mol / L.

[0048] 3. A method for catalytically converting synthesis gas to ethanol: the catalyst is loaded into a fixed-bed reactor and introduced with hydrogen for reduction activation at 500°C and atmospheric pressure for 6 hours, wherein the hydrogen space velocity is 1000 h / min. -1 Then adjust the reaction temperature to 400℃, switch to introduce synthesis gas and increase the pressure to 6MPa for reaction, wherein the molar ratio of H2 and CO in the synthesis gas is 0.3, and the synthesis gas space velocity is 1000h -1 After 2 h of reaction, the products were analyzed by gas chromatography. The results are shown in Table 1.

[0049] Example 3

[0050] 1. A catalyst for catalyzing the direct conversion of synthesis gas to ethanol, the catalyst comprising carbon nanotubes (CNTs, with a specific surface area of ​​240 m 2 / g), an active ingredient Mo2C supported on a carrier and an auxiliary agent, the auxiliary agent is a metal M1 and a metal M2, the metal M1 is Ce and K, and the metal M2 is Co; the weight ratio of metal Mo to the carrier is 50%, the molar ratio of Ce, K, Co, and Mo is 0.08:0.05:0.3:1, and the catalyst is expressed as KCeCoMo2C / CNTs.

[0051] 2. The preparation method of the catalyst comprises the following steps:

[0052] (1) Add the carrier carbon nanotubes to a 10 mol / L nitric acid solution at a ratio of 1 g:15 mL, heat and reflux at 100 ° C for 12 h, filter, wash with deionized water until the filtrate is neutral, dry at 80 ° C for 10 h, and grind to obtain a pretreated carrier;

[0053] (2) adding the support obtained in step (1) to a 1.0 mol / L ammonium molybdate solution, stirring at room temperature until dry, then drying at 120° C. for 8 h, and grinding to obtain a molybdenum-containing catalyst precursor;

[0054] (3) The molybdenum-containing catalyst precursor was first raised to 300°C at 8°C / min in a carbonizing atmosphere, then continued to be raised to 580°C at 0.5°C / min, and maintained at 580°C for 3 hours for carbonization, and then cooled to room temperature in the carbonizing atmosphere, purged with argon, and passivated for 1 hour to obtain a Mo2C-loaded catalyst precursor Mo2C / CNTs; wherein the carbonizing atmosphere is 10% propane / 90% H2, and the passivating gas is 3% O2 / 97% Ar, and the proportions are all volume ratios;

[0055] (4) Adding 1.0 mol / L cobalt acetate ethanol solution to the Mo2C-loaded catalyst precursor, stirring at room temperature until dry, and then drying at 80°C for 10 h to obtain a catalyst precursor CoMo2C / CNTs loaded with Co and Mo2C;

[0056] (5) An aqueous solution of potassium nitrate and cerium nitrate is added to the catalyst precursor loaded with Co and Mo2C, stirred at room temperature until dry, then dried at 100°C for 8 hours, calcined at 400°C for 5 hours, pressed into tablets, and sieved through a 40-60 mesh sieve to obtain the catalyst KCeCoMo2C / CNTs; wherein the total concentration of K and Ce in the aqueous solution of potassium nitrate and cerium nitrate is 0.3 mol / L.

[0057] 3. A method for catalytically converting synthesis gas to ethanol: The catalyst is loaded into a fixed-bed reactor and introduced with hydrogen-containing gas for reduction activation at 600°C and atmospheric pressure for 5 hours. The hydrogen-containing gas is composed of 5% hydrogen by volume and the remainder nitrogen, and the space velocity is 4000 h / min. -1 Then adjust the reaction temperature to 310℃, switch to introduce synthesis gas and increase the pressure to 5MPa for reaction, wherein the molar ratio of H2 and CO in the synthesis gas is 2, and the synthesis gas space velocity is 3600h -1 After 2 h of reaction, the products were analyzed by gas chromatography. The results are shown in Table 1.

[0058] Example 4

[0059] 1. A catalyst for catalyzing the direct conversion of synthesis gas to ethanol, the catalyst comprising activated carbon (AC, with a specific surface area of ​​1080 m 2 / g), an active ingredient Mo2C supported on a carrier and an auxiliary agent, the auxiliary agent is a metal M1 and a metal M2, the metal M1 is Mn and K, and the metal M2 is Ni; the weight ratio of metal Mo to the carrier is 30%, the molar ratio of Mn, K, Ni, and Mo is 0.06:0.12:0.6:1, and the catalyst is expressed as KMnNiMo2C / AC.

[0060] 2. The preparation method of the catalyst comprises the following steps:

[0061] (1) Add the carrier activated carbon to 5 mol / L nitric acid solution at a ratio of 1 g: 20 mL, heat and reflux at 70 ° C for 14 h, filter, wash with deionized water until the filtrate is neutral, dry at 120 ° C for 8 h, and grind to obtain a pretreated carrier;

[0062] (2) adding the support obtained in step (1) to a 0.6 mol / L ammonium molybdate solution, stirring at room temperature until dry, then drying at 100° C. for 7 h and grinding to obtain a molybdenum-containing catalyst precursor;

[0063] (3) The molybdenum-containing catalyst precursor was first raised to 300°C at 6°C / min in a carbonizing atmosphere, then continued to be raised to 680°C at 1°C / min, and maintained at 680°C for 1.5 hours for carbonization, and then cooled to room temperature in the carbonizing atmosphere, purged with helium, and passivated for 1 hour to obtain a catalyst precursor Mo2C / AC loaded with Mo2C; wherein the carbonizing atmosphere is N2, and the passivating gas is 1% O2 / 99% Ar, and the proportions are all volume ratios;

[0064] (4) Adding 0.6 mol / L nickel acetate aqueous solution to the Mo2C-loaded catalyst precursor, stirring at room temperature until dry, and then drying at 100°C for 7 h to obtain NiMo2C / AC, a catalyst precursor loaded with Ni and Mo2C;

[0065] (5) An aqueous solution of potassium chloride and manganese chloride is added to the catalyst precursor loaded with Ni and Mo2C, stirred at room temperature until dry, then dried at 120°C for 6 hours, calcined at 370°C for 6 hours, pressed into tablets, and sieved through a 20-40 mesh sieve to obtain the catalyst KMnNiMo2C / AC; wherein the total concentration of K and Mn in the aqueous solution of potassium chloride and manganese chloride is 0.5 mol / L.

[0066] 3. A method for catalytically converting synthesis gas to ethanol: The catalyst is loaded into a fixed-bed reactor and introduced with hydrogen-containing gas for reduction activation at 530°C and atmospheric pressure for 7 hours. The hydrogen-containing gas is composed of 40% hydrogen by volume and the remainder helium, with a space velocity of 2000 h / min. -1 Then adjust the reaction temperature to 400℃, switch to introduce synthesis gas and increase the pressure to 6MPa for reaction, wherein the molar ratio of H2 and CO in the synthesis gas is 3, and the synthesis gas space velocity is 2500h -1 After 2 h of reaction, the products were analyzed by gas chromatography. The results are shown in Table 1.

[0067] Table 1 Reaction conditions and results of direct conversion of catalytic synthesis gas to ethanol

[0068] .

Claims

1. A catalyst for catalyzing the direct conversion of synthesis gas to ethanol, characterized by: The catalyst consists of a carrier, an active ingredient supported on the carrier, and an auxiliary agent, wherein the active ingredient is Mo2C, and the auxiliary agent is metal M1 and metal M2; the metal M1 is a combination of any one of Mn, La, and Ce and K, and the metal M2 is Co or Ni; the carrier is a carbon carrier; the weight ratio of metal Mo to the carrier is 10-50%, and the molar ratio of any one of Mn, La, and Ce, K, Mo, and metal M2 is (0.05-0.1): (0.05-0.15): (0.3-0.8):

1.

2. The catalyst for catalyzing the direct conversion of synthesis gas to ethanol according to claim 1, characterized in that: The carrier is any one of activated carbon, carbon nanotubes, graphene and carbon black.

3. The method for preparing the catalyst for catalyzing the direct conversion of synthesis gas to ethanol according to claim 1, characterized in that: The following steps are involved: (1) Add the carrier to a nitric acid solution, heat and reflux at 70-150°C for 3-14 hours, filter, wash with deionized water until the filtrate is neutral, dry, and grind to obtain a pretreated carrier; (2) adding the support obtained in step (1) to an ammonium molybdate solution, stirring at room temperature until dry, and then drying and grinding to obtain a molybdenum-containing catalyst precursor; (3) carbonizing the molybdenum-containing catalyst precursor under a carbonizing atmosphere by programmed temperature increase, then cooling the temperature to room temperature in the carbonizing atmosphere, purging with an inert gas, and introducing a passivation gas for passivation for 0.5-2 hours to obtain a catalyst precursor loaded with Mo2C; (4) adding an ethanol solution or an aqueous solution of metal M2 to the catalyst precursor loaded with Mo2C, stirring at room temperature until dry, and then drying to obtain a catalyst precursor loaded with M2 and Mo2C; (5) Adding an ethanol solution or an aqueous solution of metal M1 to the catalyst precursor loaded with M2 and Mo2C, stirring at room temperature until dry, then drying, calcining, tableting, and sieving through a 20-60 mesh sieve to obtain the catalyst.

4. The method for preparing the catalyst for catalyzing the direct conversion of synthesis gas to ethanol according to claim 3, characterized in that: The carbonization is specifically as follows: first, the temperature is raised to 300° C. at a heating rate of 5-10° C. / min, then the temperature is raised to 580-800° C. at a heating rate of 0.5-2° C. / min, and maintained for 1-3 hours.

5. The method for preparing the catalyst for catalyzing the direct conversion of synthesis gas to ethanol according to claim 4, characterized in that: The carburizing atmosphere is an inert atmosphere, a hydrogen-containing atmosphere or a carbon-containing atmosphere; The inert atmosphere is any one of nitrogen, helium or argon; The hydrogen-containing atmosphere is 100% hydrogen, or is composed of ≥5% hydrogen by volume and the balance gas; the balance gas is any one of nitrogen, helium or argon; The carbon-containing atmosphere is composed of 10-30% by volume of carbon-containing gas and the balance of hydrogen, and the carbon-containing gas is at least one of methane, ethane, ethylene, propane, propylene, butane, and butene.

6. The method for preparing a catalyst for catalytic direct conversion of synthesis gas to ethanol according to claim 3, wherein the passivation gas is composed of 0.1-3% by volume of oxygen and a balance gas, and the balance gas is any one of nitrogen, helium or argon.

7. The method for preparing the catalyst for catalyzing the direct conversion of synthesis gas to ethanol according to claim 3, characterized in that: The concentration of the nitric acid solution is 5-10 mol / L, and the ratio of the carrier to the nitric acid solution is 1 g: (10-20) mL; the concentration of molybdenum ions in the ammonium molybdate solution is 0.5-1 mol / L; the ion concentration of metal M2 in the ethanol solution or aqueous solution of metal M2 is 0.5-1 mol / L; the total ion concentration of metal M1 in the ethanol solution or aqueous solution of metal M1 is 0.1-0.5 mol / L.

8. The method for preparing the catalyst for catalyzing the direct conversion of synthesis gas to ethanol according to claim 3, characterized in that: The drying in step (1) is carried out at 60-100°C for 8-12 hours; the drying in steps (2), (4) and (5) is carried out at 80-150°C for 6-10 hours; and the calcination is carried out at 300-450°C for 3-8 hours.

9. A method for producing ethanol by catalytic direct conversion of synthesis gas, characterized in that: The catalyst is loaded into a fixed bed reactor, and hydrogen-containing gas is introduced for reduction activation. The reaction temperature is then adjusted to 260-400°C, and synthesis gas is introduced at 3-6 MPa for reaction. The molar ratio of H2 to CO in the synthesis gas is 0.3-4, and the synthesis gas space velocity is 1000-5000 h -1 ; The catalyst is the catalyst according to claim 1.

10. The method for producing ethanol by catalytic direct conversion of synthesis gas according to claim 9, characterized in that: The reduction activation conditions are: reduction temperature 400-600 ° C, reduction time 5-8h, reduction pressure is normal pressure, and the space velocity of hydrogen-containing gas is 1000-5000h -1 ; The hydrogen-containing gas is 100% hydrogen, or is composed of hydrogen with a volume ratio of ≥5% and the balance gas; the balance gas is nitrogen, helium or argon.