CN116393141B - Catalyst and method for preparing ethanol and methanol by methyl acetate hydrogenation - Google Patents

Abstract

The invention discloses a catalyst and a method for preparing ethanol and methanol by methyl acetate hydrogenation, wherein the catalyst is a composite oxide catalyst prepared by adopting a precipitation and hydrothermal two-step method, cu is taken as a main active component, any one or more of Zn, mn, zr, ce and Mg are taken as auxiliary agents, alumina is taken as a carrier, and the mass of the catalyst is 100 percent, wherein the mass of Cu is 20-50 percent, the mass of Mg is 5-15 percent, and the mass of the rest auxiliary agents is 3-8 percent. Compared with the traditional coprecipitation and impregnation methods, the catalyst prepared by the two-step method has a hydrotalcite-like layered porous structure, so that Cu active components can be effectively dispersed, and interaction between an auxiliary agent and Cu in the catalyst is improved. The catalyst is used for continuously catalyzing methyl acetate hydrogenation to prepare ethanol and methanol, and improves the selectivity of ethanol and the stability of the catalyst.

Description

A catalyst and method for hydrogenating methyl acetate to produce ethanol and methanol

Technical Field

The invention belongs to the technical field of ester hydrogenation, and particularly relates to a hydrotalcite-like layered porous copper-based composite catalyst and a method for preparing ethanol and methanol by hydrogenating methyl acetate using the catalyst.

Background Art

Ethanol, commonly known as alcohol (C ₂ H ₅ OH), is a colorless, transparent liquid that is easy to burn and volatilize, has a special aroma, and is widely used in food, medicine, chemicals, printing and dyeing, national defense and other social aspects. Ethanol has strong permeability, solubility and bactericidal power, and can be used to prepare various organic solvents such as food preservatives, disinfectants and extractants. As an important organic chemical raw material, ethanol can also be used to produce chemicals such as acetaldehyde, ether, butadiene, and ethyl chloride. In addition, ethanol has a low calorific value, high latent heat of vaporization, good anti-explosion performance, and high oxygen content. It can be used to produce ethanol gasoline as automobile fuel and is considered to be the "green energy" of the 21st century. Methanol, as the simplest saturated monohydric alcohol, ranks among the top five traded chemicals in the world. It is widely used in industrial fields such as transportation, agriculture and national defense, and is used to synthesize bulk chemicals such as formaldehyde, acetic acid, methyl chloride, methylamine, pesticides, and medicines, as well as fine chemicals such as pesticides and medicines. At the same time, methanol has high thermal efficiency and good anti-explosion properties when burned. After deep processing, it can be added to gasoline as a clean fuel. It is of great significance to achieving energy diversification, improving energy structure, and ensuring energy security.

At present, ethanol is mainly obtained by biomass fermentation and chemical synthesis, while most methanol is indirectly obtained by catalytic synthesis of synthesis gas using fossil energy as raw materials. These processes not only have long routes, high energy consumption, but also low selectivity. Patent CN101665408A discloses a method for preparing methanol and ethanol simultaneously by chemical reaction of dead leaves, gasifying the dead leaves, and then adjusting the carbon-hydrogen ratio in the gasification product to reach a carbon-hydrogen ratio suitable for synthesizing methanol and ethanol. However, the gasification of dead leaves will produce a large amount of toxic gases such as carbon monoxide, and the yield is low. After esterification of acetic acid, hydrogenation on a copper-based catalyst can produce equimolar ethanol and methanol, which not only has a high yield, but also has low cost and requirements for equipment. It is one of the most attractive ethanol production routes in recent years. In addition, my country's vinylon industry produces more than one million tons of methyl acetate as a byproduct every year, which will further accelerate the rapid development of methyl acetate hydrogenation technology for preparing ethanol. The copper-based catalysts currently used in industry generally have low dispersion of active components, easy sintering, and weak resistance to impurity interference, resulting in reduced activity and poor stability of the catalyst.

CN102327774A discloses a catalyst for preparing ethanol by hydrogenating acetate, wherein active metal copper accounts for 30-60%, auxiliary metal accounts for 5-40%, and carrier accounts for 20-50%; wherein the auxiliary metal is one or any combination of two or more of Mg, Zn, Mn, Ni, Sn, Ag, Pd and lanthanide elements, and the carrier is silicon dioxide or aluminum oxide. In the implementation case, at a reaction pressure of 3MPa, a temperature of 210°C, and a liquid space velocity of 1.2g/gcat·h, the conversion rate is 85% and the selectivity is 79%.

CN111151261A discloses a methyl acetate hydrogenation catalyst and its use. The catalyst comprises one or two of Cu, Zn, Mn and La oxides and silicon dioxide. The catalyst adopts a co-precipitation-ammonia evaporation preparation method. Although the active components are evenly dispersed and various properties are good, the preparation process is time-consuming and is continuously accompanied by the release of a large amount of irritating gas ammonia.

CN106518619A invention discloses a method for preparing ethanol from acetate, wherein in the Cu-M/SiO2 catalyst, Cu is an active component, CuO accounts for 10-85wt% of the total catalyst; M is one or more of Mn, Zn, Fe, Co, and Ni, accounting for 0.1-20wt%; _SiO2 accounts for 10-89.9wt%. The catalyst of the present invention needs to be in hydrogen containing CO (synthesis gas) to significantly increase the activity of methyl acetate hydrogenation reaction and significantly improve the yield of the reaction product.

Summary of the invention

In view of the problems existing in the above-mentioned prior art, one of the objects of the present invention is to provide a layered highly dispersed copper-based composite catalyst, and at the same time to provide a method for catalyzing the hydrogenation of methyl acetate to prepare ethanol and methanol under relatively mild conditions using the catalyst.

In order to achieve the above-mentioned purpose, the copper-based composite catalyst adopted by the present invention is a hydrotalcite-like porous layered structure, which uses Cu as an active component, any one or more of Zn, Mn, Zr, Ce and Mg as additives, and alumina as a carrier; based on the mass of the catalyst as 100%, the mass of the active component is 20% to 50%, the mass of Mg is 5% to 15%, and the mass of the remaining additives is 3% to 10%. Preferably, the mass fraction of the active component is 40% to 45%, the mass of Mg is 8% to 10%, and the mass of the remaining additives is 5% to 7%.

The copper-based composite catalyst of the present invention is prepared by the following method:

(1) Dissolving copper nitrate, a soluble salt of an auxiliary agent and an alumina source in deionized water to prepare a salt solution with a total metal ion concentration of 0.04 to 2 mol/L; adding the salt solution dropwise to a 1 to 3 mol/L aqueous solution of a precipitant at 50 to 80° C. and stirring vigorously to obtain a uniform solution, wherein the end point pH value of the obtained solution is 6 to 10; the precipitant is a mixed alkali of any one of ammonium carbonate, sodium carbonate, and urea and sodium hydroxide in a molar ratio of 1:2 to 4.

(2) adding a template to the uniform solution of step (1), and stirring at 50-80° C. for 1-5 hours; the template is any one of hexadecyltrimethylammonium bromide, polyethylene glycol, and poloxamer P123.

(3) transferring the mixture obtained after stirring in step (2) to a closed high-pressure reactor, subjecting it to a hydrothermal treatment at 80-120° C. for 20-30 hours; centrifugation and filtration, washing the obtained solid with deionized water or ethanol, and then drying it at 80-150° C. for 10-18 hours, and then calcining it in a muffle furnace at 300-600° C. for 4-8 hours to obtain a catalyst.

In the above step (1), the alumina source is any one or more of aluminum nitrate, aluminum sol, and aluminum isopropoxide, and the soluble salt of the auxiliary agent is a mixture of any one of manganese nitrate, zirconium borate, zinc nitrate, cerium nitrate, and magnesium nitrate.

In the above step (2), the ratio of the template to the total molar amount of metal ions in step (1) is 0.01 to 0.08:1.

The method for preparing ethanol and methanol by hydrogenating methyl acetate provided by the present invention comprises: pressing the copper-based composite catalyst into 10-60 mesh particles, loading the particles into a continuous fixed bed reactor, reducing the catalyst with hydrogen, preheating methyl acetate to 150-280° C., introducing the methyl acetate into the continuous fixed bed reactor at a mass space velocity of 1-6.0 h ^-1 , and continuously introducing hydrogen, controlling the molar ratio of hydrogen to methyl acetate to be 5-25:1, and carrying out catalytic hydrogenation reaction at a temperature of 170-350° C. and a pressure of 0.5-8.0 MPa to obtain ethanol and methanol.

Further preferred conditions for reducing the catalyst with hydrogen are: pressure 0.1-5.0 MPa, hydrogen volume space velocity 3000-8000 h ^-1 , heating to 180-250° C. at a rate of 0.5-5° C./min, and reduction for 1-24 hours.

In the above method for preparing ethanol and methanol by hydrogenation of methyl acetate, methyl acetate is preferably preheated to 190-220° C., introduced into a continuous fixed bed reactor at a mass space velocity of 0.5-3.0 h ^-1 , and hydrogen is continuously introduced, the molar ratio of hydrogen to methyl acetate is controlled to be 8-15:1, and the catalytic hydrogenation reaction is carried out at a temperature of 180-230° C. and a pressure of 1.0-5.0 MPa.

The beneficial effects of the present invention are as follows:

1. The present invention adopts a two-step method of uniform precipitation and hydrothermal self-assembly to prepare a copper-based composite catalyst. Compared with the traditional co-precipitation and impregnation method, the catalyst prepared by the two-step method of the present invention not only has a high content of active components, but also has a hydrotalcite-like layered porous structure, which is conducive to the internal and external diffusion of reactants and products, can promote the dispersion of the active component Cu, improve the interaction between the additive and Cu in the catalyst, expose more catalytic active centers, and make the catalyst have high reaction activity and stability.

2. The catalyst of the present invention is used for catalyzing the reaction of preparing ethanol and methanol from methyl acetate as a raw material. The catalytic performance is excellent, the methyl acetate conversion rate can reach up to more than 97%, and the selectivity of ethanol and methanol is greater than 98%. The catalyst activity remains basically unchanged after stably operating for 2000 hours. It has the advantages of high selectivity and catalyst stability, and has broad application prospects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an XRD diagram of 43% Cu-9% Mg-6% Ce/Al ₂ O ₃ in Example 4 and commercial 50% CuZnAl catalyst in an oxidized state.

DETAILED DESCRIPTION

The present invention is further described in detail below in conjunction with the accompanying drawings and examples, but the examples do not limit the scope of protection claimed for the present invention.

Example 1

(1) According to the atomic molar ratio of Cu:Mg:Al:Mn being 8:4:6:1, Cu(NO ₃ ) ₂ ·3H ₂ O, Mg(NO ₃ ) ₂ ·6H ₂ O, Al(NO ₃₎₃ ·9H ₂ O and manganese nitrate were dissolved in deionized water to form a salt solution with a total metal ion concentration of 1.5 mol/L; NaOH and (NH ₄ ) ₂ CO ₃ in a molar ratio of 3:1 were dissolved in deionized water to form an alkaline solution with a total precipitant concentration of 1.5 mol/L. Then, 500 mL of the two solutions were respectively measured and placed in a beaker. At 50°C and under vigorous stirring, the salt solution was gradually added dropwise to the alkaline solution and maintained for 1 hour to form a uniform solution. The endpoint pH of the obtained solution was controlled between 6 and 8.

(2) According to the total molar ratio of the template to the metal ion being 0.05:1, 13.65 g of hexadecyltrimethylammonium bromide was weighed and added to the uniform solution of step (1) under stirring conditions, and stirred and aged in a 50° C. water bath for 3 hours.

(3) The mixture obtained after stirring in step (2) was transferred to a closed autoclave and subjected to hydrothermal treatment at 100°C for 24 hours. After centrifugal filtration, the obtained solid was washed with deionized water until the pH value reached 7, then dried at 120°C for 12 hours, and then calcined in a muffle furnace at 550°C for 6 hours to obtain a catalyst 43% Cu-9% Mg-5% Mn/Al ₂ O ₃ . The low-temperature N ₂ physical adsorption test results of the obtained catalyst are shown in Table 1.

The catalyst 43% Cu-9% Mg-5% Mn/ _{Al2O3 was} pressed into 10-60 mesh particles, loaded into a continuous fixed bed reactor, introduced with high-purity hydrogen, heated to 195°C at a rate of 1°C/min at a pressure of 0.5MPa and a hydrogen volume space velocity of 5000h ^-1 , and reduced for 5 hours. Then, a high-pressure constant flow pump was used to pump methyl acetate liquid preheated to 160°C into the continuous fixed bed reactor, the mass space velocity of methyl acetate was 2h ^-1 , and hydrogen was continued to be introduced, the molar ratio of hydrogen to methyl acetate was controlled to be 15:1, and catalytic hydrogenation reaction was carried out at a temperature of 180°C and a pressure of 3.0MPa to prepare ethanol and methanol. The obtained reaction product was analyzed by gas chromatography, and the conversion rate of methyl acetate and the selectivity of ethanol and methanol are shown in Table 2.

Example 2

In step (1) of this example, the manganese nitrate in Example 1 was replaced by an equal molar amount of Zr(NO ₃ ) ₄ ·5H ₂ O, and the other steps were the same as Example 1 to obtain a catalyst 42% Cu-9% Mg-7% Zr/Al ₂ O ₃ . The low temperature N ₂ physical adsorption test results of the obtained catalyst are shown in Table 1.

The catalyst 42% Cu-9% Mg-7% Zr/ _{Al2O3 was} pressed into 10-60 mesh particles, loaded into a continuous fixed bed reactor, introduced with high-purity hydrogen, heated to 195°C at a rate of 1°C/min at a pressure of 0.5MPa and a hydrogen volume space velocity of 5000h ^-1 , and reduced for 5 hours. Then, a high-pressure constant flow pump was used to pump methyl acetate liquid preheated to 170°C into the continuous fixed bed reactor, the mass space velocity of methyl acetate was 2h ^-1 , and hydrogen was continued to be introduced, the molar ratio of hydrogen to methyl acetate was controlled to be 15:1, and catalytic hydrogenation reaction was carried out at a temperature of 170°C and a pressure of 3.0MPa to prepare ethanol and methanol. The obtained reaction product was analyzed by gas chromatography, and the conversion rate of methyl acetate and the selectivity of ethanol and methanol are shown in Table 2.

Example 3

In step (1) of this example, the manganese nitrate in Example 1 was replaced by an equal molar amount of Zn(NO ₃ ) ₄ ·6H ₂ O, and the other steps were the same as Example 1 to obtain a catalyst 43% Cu-9% Mg-5% Zn/Al ₂ O ₃ . The obtained fresh catalyst was characterized by XRD, as shown in FIG1 , with a mirror size of .

The catalyst 43% Cu-9% Mg-5% Zn/ _{Al2O3 was} pressed into 10-60 mesh particles, loaded into a continuous fixed bed reactor, introduced with high-purity hydrogen, heated to 195°C at a rate of 1°C/min at a pressure of 0.5MPa and a hydrogen volume space velocity of 5000h ^-1 , and reduced for 5 hours. Then, a high-pressure constant flow pump was used to pump methyl acetate liquid preheated to 180°C into the continuous fixed bed reactor, the mass space velocity of methyl acetate was 2.0h ^-1 , and hydrogen was continued to be introduced, the molar ratio of hydrogen to methyl acetate was controlled to be 15:1, and catalytic hydrogenation reaction was carried out at a temperature of 180°C and a pressure of 3.5MPa to prepare ethanol and methanol. The obtained reaction product was analyzed by gas chromatography, and the conversion rate of methyl acetate and the selectivity of ethanol and methanol are shown in Table 2.

Example 4

In step (1) of this embodiment, according to the atomic molar ratio of Cu:Mg:Al:Ce being 8:4:6:0.5, Cu(NO ₃ ) ₂ ·3H ₂ O, Mg(NO ₃ ) ₂ ·6H ₂ O, Al(NO _{3) 3} ·9H ₂ O and Ce(NO ₃ ) ₄ ·6H ₂ O were dissolved into a salt solution with a total metal ion concentration of 1.5 mol/L using deionized water, and the other steps were the same as those in Example 1 to obtain a catalyst 43% Cu-9% Mg-6% Ce/Al ₂ O ₃ . The X-ray diffraction pattern of the oxidized catalyst is shown in FIG1 . According to the calculation of the Scherrer formula, the crystal size (9.8 nm) of the catalyst prepared by this method at the (002) crystal plane is significantly smaller than that of the commercial 50% CuZnAl catalyst (40.1 nm).

The catalyst 43% Cu-9% Mg-6% Ce/ _{Al2O3 was} pressed into 10-60 mesh particles, loaded into a continuous fixed bed reactor, introduced with high-purity hydrogen, heated to 195°C at a rate of 1°C/min at a pressure of 0.5MPa and a hydrogen volume space velocity of 5000h ^-1 , and reduced for 5 hours. Then, a high-pressure constant flow pump was used to pump methyl acetate liquid preheated to 170°C into the continuous fixed bed reactor, the mass space velocity of methyl acetate was 2.5h ^-1 , and hydrogen was continued to be introduced, the molar ratio of hydrogen to methyl acetate was controlled to be 10:1, and catalytic hydrogenation reaction was carried out at a temperature of 170°C and a pressure of 4.0MPa to prepare ethanol and methanol. The obtained reaction product was analyzed by gas chromatography, and the conversion rate of methyl acetate and the selectivity of ethanol and methanol are shown in Table 2.

Example 5

In step 2 of this example, the total molar ratio of the template to the metal ion is 0.01:1, 30 g of polyethylene glycol with a number average molecular weight of 4000 is used to replace the hexadecyltrimethylammonium bromide in Example 4, and the other steps are the same as Example ₄ to obtain a catalyst 43% Cu-9% Mg-6% Ce/ _Al2O3 .

The catalyst 43% Cu-9% Mg-6% Ce/ _Al2O3 was pressed into 10-60 mesh _particles and loaded into a continuous fixed bed reactor to catalyze the hydrogenation of methyl acetate to ethanol and methanol according to the method of Example 4. The obtained reaction product was analyzed by gas chromatography, and the methyl acetate conversion rate and the selectivity of ethanol and methanol are shown in Table 2.

Example 6

In step 2 of this example, the hexadecyltrimethylammonium bromide in Example 4 was replaced with 87 mL of 0.5 g/mL poloxamer P123 methanol solution according to the total molar ratio of the template to the metal ion being 0.01:1. The other steps were the same as those in Example 4 to obtain a catalyst 43% Cu-9% Mg-6% Ce/Al ₂ O ₃ .

The catalyst 43% Cu-9% Mg-6% Ce/ _{Al2O3 was} pressed into 10-60 mesh particles, loaded into a continuous fixed bed reactor, introduced with high-purity hydrogen, heated to 200°C at a rate of 1°C/min at a pressure of 0.5 MPa and a hydrogen volume space velocity of 5000 h ^-1 , and reduced for 5 hours. Then, a high-pressure constant flow pump was used to pump methyl acetate liquid preheated to 190°C into the continuous fixed bed reactor, the mass space velocity of methyl acetate was 2.5 h ^-1 , and hydrogen was continued to be introduced, the molar ratio of hydrogen to methyl acetate was controlled to be 10:1, and catalytic hydrogenation reaction was carried out at a temperature of 190°C and a pressure of 4.0 MPa to prepare ethanol and methanol. The obtained reaction product was analyzed by gas chromatography, and the methyl acetate conversion rate and the selectivity of ethanol and methanol are shown in Table 2.

Example 7

In step (1) of this embodiment, NaOH and Na ₂ CO ₃ in a molar ratio of 4:1 are dissolved in deionized water to form an alkaline solution with a total precipitant concentration of 1.5 mol/L. The other steps are the same as those in Example 4 to obtain a catalyst 43% Cu-9% Mg-6% Ce/Al ₂ O ₃ . The low temperature N ₂ physical adsorption test results of the obtained catalyst are shown in Table 1.

The catalyst 43% Cu-9% Mg-6% Ce/ _{Al2O3 was} pressed into 10-60 mesh particles, loaded into a continuous fixed bed reactor, and introduced with high-purity hydrogen. The temperature was raised to 190°C at a rate of 1°C/min at a pressure of 0.5 MPa and a hydrogen volume space velocity of 5000 h ^-1 , and reduced for 5 hours. Then, a high-pressure constant flow pump was used to pump methyl acetate liquid preheated to 200°C into the continuous fixed bed reactor, and the mass space velocity of methyl acetate was 2.5 h ^-1 . Hydrogen was continued to be introduced, and the molar ratio of hydrogen to methyl acetate was controlled to be 10:1. The catalytic hydrogenation reaction was carried out at a temperature of 190°C and a pressure of 3.0 MPa to prepare ethanol and methanol. Quantitative analysis showed that the conversion rate of methyl acetate and the selectivity of ethanol and methanol were as shown in Table 2.

Example 8

In step (1) of this example, NaOH and urea in a molar ratio of 2:1 are dissolved in deionized water to form an alkaline solution with a total precipitant concentration of 1.5 mol/L. The other steps are the same as those of Example ₄ to obtain a catalyst 43% Cu-9% Mg-6% Ce/ _Al2O3 .

The catalyst 43% Cu-9% Mg-6% Ce/ _Al2O3 was pressed into 10-60 mesh _particles and loaded into a continuous fixed bed reactor to catalyze the hydrogenation of methyl acetate to ethanol and methanol according to the method of Example 7. The obtained reaction product was analyzed by gas chromatography, and the methyl acetate conversion rate and the selectivity of ethanol and methanol are shown in Table 2.

Example 9

In step (1) of this example, Al(NO _{3) 3} ·9H ₂ O was replaced by aluminum sol, and the other steps were the same as those of Example 8, to obtain a catalyst 43% Cu-9% Mg-6% Ce/Al ₂ O ₃ .

The catalyst 43% Cu-9% Mg-6% Ce/ _{Al2O3 was} pressed into 10-60 mesh particles, loaded into a continuous fixed bed reactor, introduced with high-purity hydrogen, heated to 200°C at a rate of 1°C/min at a pressure of 0.5MPa and a hydrogen volume space velocity of 5000h ^-1 , and reduced for 5 hours. Then, methyl acetate liquid preheated to 200°C was pumped into the continuous fixed bed reactor using a high-pressure constant flow pump, the mass space velocity of methyl acetate was 2.5h ^-1 , and hydrogen was continued to be introduced, the molar ratio of hydrogen to methyl acetate was controlled to be 10:1, and catalytic hydrogenation reaction was carried out at a temperature of 200°C and a pressure of 4.0MPa to prepare ethanol and methanol. The obtained reaction product was analyzed by gas chromatography, and the conversion rate of methyl acetate and the selectivity of ethanol and methanol are shown in Table 2.

Table 1

Table 2

catalyst Methyl acetate conversion % Ethanol selectivity % Example 1 92.3 98.6 Example 2 95.5 91.1 Example 3 93.5 95.6 Example 4 97.5 91.1 Example 5 92.5 96.7 Example 6 85.4 96.7 Example 7 92.5 96.7 Example 8 91.5 98.6 Example 9 87.5 96.6

Note: One molecule of methyl acetate is hydrogenated to produce one molecule of ethanol and one molecule of methanol at the same time. Therefore, the selectivity of methanol is almost equal to the selectivity of ethanol in the table.

Claims (8)

1. A method for preparing methanol and ethanol by methyl acetate hydrogenation is characterized by comprising the following steps: tabletting the catalyst into 10-60 mesh particles, filling the particles into a continuous fixed bed reactor, reducing the catalyst by hydrogen, preheating methyl acetate to 150-280 ℃, introducing the catalyst into the continuous fixed bed reactor at a mass airspeed of 0.5-10.0 h ^-1, continuously introducing hydrogen, controlling the molar ratio of the hydrogen to the methyl acetate to be 5-40:1, and carrying out catalytic hydrogenation reaction at a temperature of 170-350 ℃ and a pressure of 0.5-8.0 MPa to obtain ethanol and methanol;

The catalyst is of a hydrotalcite-like layered porous structure, any one or more of Cu and Zn, mn, zr, ce are used as active components, mg is used as an auxiliary agent, and alumina is used as a carrier; the mass of the active component is 20-50%, the mass of Mg is 5-15% and the mass of the rest auxiliary agent is 3-10% based on 100% of the mass of the catalyst; the catalyst is prepared by the following method:

(1) Dissolving copper nitrate, soluble salt of an auxiliary agent and an alumina source into deionized water to prepare a salt solution with the total concentration of metal ions of 0.04-2 mol/L; dropwise adding the salt solution into 1-3 mol/L of precipitant aqueous solution at 50-80 ℃, and vigorously stirring to obtain a uniform solution, wherein the final pH value of the obtained solution is 6-10; the precipitant is mixed alkali of any one of ammonium carbonate, sodium carbonate and urea and sodium hydroxide in a molar ratio of 1:2-4;

(2) Adding a template agent into the uniform solution in the step (1), and stirring for 1-5 hours at 50-80 ℃; the template agent is any one of cetyl trimethyl ammonium bromide, polyethylene glycol and poloxamer P123;

(3) Transferring the mixture obtained after stirring in the step (2) to a closed high-pressure reaction kettle, and carrying out hydrothermal treatment for 20-30 hours at the temperature of 80-120 ℃; centrifugal filtration, washing the obtained solid with deionized water or ethanol, drying at 80-150 ℃ for 10-18 hours, and roasting in a muffle furnace at 300-600 ℃ for 4-8 hours to obtain the catalyst.

2. The method for preparing methanol and ethanol by hydrogenating methyl acetate according to claim 1, wherein the method comprises the following steps: the mass fraction of the active components is 40-45%, the mass fraction of Mg is 8-10% and the mass fraction of the rest auxiliary agents is 5-7% based on 100% of the mass of the catalyst.

3. The method for preparing methanol and ethanol by hydrogenating methyl acetate according to claim 1, wherein the method comprises the following steps: the alumina source is any one or more of aluminum nitrate, aluminum sol and aluminum isopropoxide.

4. The method for preparing methanol and ethanol by hydrogenating methyl acetate according to claim 1, wherein the method comprises the following steps: the soluble salt of the auxiliary agent is a mixture of any one of manganese nitrate, zirconium borate, zinc nitrate and cerium nitrate and magnesium nitrate.

5. The method for preparing methanol and ethanol by hydrogenating methyl acetate according to claim 1, wherein the method comprises the following steps: in the step (2), the ratio of the template agent to the total molar amount of the metal ions in the step (1) is 0.01-0.08:1.

6. The method for preparing methanol and ethanol by hydrogenating methyl acetate according to claim 1, wherein the conditions of the hydrogen reduction catalyst are as follows: the pressure is 0.1-5.0 MPa, the hydrogen volume airspeed is 3000-12000 h ^-1, the temperature is raised to 180-250 ℃ at the speed of 0.5-5 ℃/min, and the hydrogen is reduced for 1-24 hours.

7. The method for preparing methanol and ethanol by hydrogenating methyl acetate according to claim 1, wherein the conditions of the hydrogen reduction catalyst are as follows: the pressure is 0.5-1.5 MPa, the hydrogen volume airspeed is 5000-8000 h ^-1, the temperature is raised to 190-220 ℃ at the speed of 1-3 ℃/min, and the hydrogen is reduced for 10-12 hours.

8. The method for preparing methanol and ethanol by hydrogenating methyl acetate according to claim 1, wherein the method comprises the following steps: preheating methyl acetate to 190-220 ℃, introducing the methyl acetate into a continuous fixed bed reactor at a mass airspeed of 0.5-4.0 h ^-1, continuously introducing hydrogen, controlling the molar ratio of the hydrogen to the methyl acetate to be 5-30:1, and carrying out catalytic hydrogenation reaction at a temperature of 180-240 ℃ and a pressure of 1.0-5.0 MPa.