Catalyst for preparing methanol from biomass synthesis gas and preparation method thereof

Abstract

The invention discloses a catalyst for preparing methanol from biomass synthesis gas and a preparation method thereof, and relates to the technical field of methanol preparation, and the preparation method comprises the following steps: S1, preparing a salt solution A, a salt solution B and an alkali solution C; s2, carrying out a first-step precipitation reaction; s3, high-dispersion suspension slurry D is formed; s4, carrying out a second-step precipitation reaction; s5, after aging, filtering and washing the precipitate, and drying a filter cake obtained by filtering; s6, performing low-temperature decomposition on the dried product, and adding graphite to form a catalyst; the salt solution B is precipitated and aged firstly, so that the salt solution B is more stable, the salt solution B is more stably combined with the precipitate of the subsequent salt solution A, and the precipitate is wrapped, so that the salt solution B is more stably loaded on the carrier, and the catalyst is more stable.

Description

Technical Field

[0001] The invention relates to the technical field of methanol preparation, and in particular to a catalyst for preparing methanol from biomass synthesis gas and a preparation method thereof. Background Art

[0002] Methanol, as the basic organic raw material of C1 chemistry, is mainly used to produce methyl tert-butyl ether (MTBE), dimethyl ether, formaldehyde, methyl formate, acetic acid and its derivatives, fumarate (DMF), gasoline, etc. It can also be used as a potential automotive alcohol ether fuel and fuel cell fuel. With the promotion and application of methanol gasoline, the technological progress and industrial breakthrough of methanol protein and methanol to olefins, and the continuous development of downstream products such as dimethyl ether, acetic acid, methyl formate, dimethyl carbonate, etc., the demand for methanol is increasing, and it has a bright application prospect. Using synthesis gas as raw material, through the catalytic reaction process of liquid or gas phase, it is a main method used in industry at present. Synthesis gas can be obtained by biomass gasification, that is, biomass materials such as wood, straw, hemp palm, fruit shells, etc. are converted into gas under continuous heating conditions. The gas produced in the process of biomass gasification is mainly composed of CO, H2, CH4, CO2, N2 and other components. Using biomass as raw material has economic and environmental benefits. In the process of producing methanol, copper-based catalysts are generally used, and copper is considered to be the main active component. However, the activity of copper alone is very poor, and the introduction of other components can greatly improve the activity and stability of the catalyst. Currently, the catalysts used in the world are basically mixed oxides of copper, zinc and aluminum.

[0003] For example, the Chinese patent, application number CN202011110409.0, is a method for preparing a high-stability methanol synthesis catalyst. The method adopts an improved two-step precipitation method, which specifically includes co-precipitating and aging a mixed salt solution of zinc nitrate and aluminum nitrate with an alkaline solution, filtering and washing the aged slurry to obtain a filter cake, dispersing the obtained filter cake into a mixed salt solution of zinc nitrate, aluminum nitrate, copper nitrate and magnesium nitrate to obtain a highly dispersed suspension slurry, co-precipitating and aging the highly dispersed suspension slurry with an alkaline solution, and then filtering, washing, drying, roasting, and tableting to obtain a methanol synthesis catalyst. The invention is scientifically designed, the method is simple, and the operation is convenient. The methanol synthesis catalyst prepared by the present invention can be widely used in the production of methanol from biomass synthesis gas containing CO2, CO and H2 under low temperature and low pressure conditions. The catalyst has excellent low-temperature activity, good hydrothermal stability, and high selectivity.

[0004] However, due to the two-step precipitation method, the stability of the second-step precipitation is lower than that of the first-step precipitation during aging, so that the first-step reaction components in the catalyst are less stable when they are wrapped by the second-step reaction components on the carrier, and the effective components are easy to fall off. Summary of the invention

[0005] The embodiments of the present application provide a catalyst for producing methanol from biomass synthesis gas and a preparation method thereof, thereby solving the technical problem of carrier variability in the prior art and achieving the technical effect of improving the stability of the carrier.

[0006] The present invention provides a method for preparing a catalyst for producing methanol from biomass synthesis gas, comprising the following steps:

[0007] S1, dissolving zinc nitrate and aluminum nitrate in water to form a zinc-aluminum mixed salt solution A, dissolving zinc nitrate, aluminum nitrate, copper nitrate and magnesium nitrate in water to form a copper-zinc-magnesium-aluminum mixed salt solution B, and dissolving sodium carbonate in water to form an alkaline solution C;

[0008] The mass ratio of zinc, aluminum, copper and magnesium in zinc nitrate, aluminum nitrate, copper nitrate and magnesium nitrate is (3-5): (1-3): (10-15): (0.3-1); the concentration of sodium carbonate in the alkaline solution C is 2.5 mol / L;

[0009] The molar ratio of zinc in salt solution A to that in salt solution B is 1:6-1:2;

[0010] The molar ratio of aluminum in salt solution A to that in salt solution B is 2:1-16:1;

[0011] S2, performing the first step of precipitation reaction, i.e., adding salt solution B and alkaline solution C to a reaction tank containing deionized water under stirring, reacting to generate precipitate I, and continuing aging for a certain period of time after the addition is completed;

[0012] S3. After aging, the precipitate is filtered and washed, and the filter cake obtained by filtration is dispersed into the mixed salt solution A to form a highly dispersed suspension slurry D;

[0013] S4, performing a second step precipitation reaction, i.e., under stirring, simultaneously adding the suspension slurry D and the alkaline solution C to the reaction tank containing deionized water, reacting to generate a precipitate II, and stopping the addition of the alkaline solution C after the addition of the suspension slurry D is completed, and continuing aging for a certain period of time;

[0014] S5. After aging is completed, the precipitate is filtered and washed, and the filter cake obtained by filtration is dried;

[0015] S6, decomposing the dried product at low temperature, adding graphite to the decomposition product, mixing evenly, and shaping the mixture to obtain a methanol synthesis catalyst; the temperature of the low temperature decomposition is 300-400° C., and the time is 2-6 hours; the amount of the graphite is 1-3wt% of the mass of the mixture;

[0016] Furthermore, the precipitation reaction temperature of step S2 and step S4 is 70-80° C., the pH value is 6.0-8.0, and the aging temperature is the same as the reaction temperature.

[0017] Furthermore, the aging time of step S2 is 15-60 minutes, and the aging time of step S4 is 60-120 minutes.

[0018] Furthermore, in step S2, the salt solution B and the alkaline solution C are added dropwise simultaneously.

[0019] Furthermore, in step S2, the salt solution B and the alkaline solution C are added by pouring the salt solution B into a reaction tank containing deionized water, and then adding the alkaline solution C dropwise to react until no precipitate is generated.

[0020] Furthermore, when the first precipitation reaction is performed in step S2, part of the alkaline solution C is poured into a reaction tank containing deionized water under stirring, and then part of the salt solution B is added dropwise for reaction. After the addition of the salt solution B is completed, the aging is continued for a certain time. After that, the precipitate is taken out and placed in another reaction tank containing deionized water, and the remaining salt solution B is poured in. The alkaline solution C is titrated against the salt solution B until no more precipitate is generated. After the addition of the alkaline solution C is completed, the aging is continued for a certain time.

[0021] Furthermore, the part of the alkaline solution C and the part of the salt solution B are specifically 50% of the amount of the alkaline solution C and the salt solution B used in step S2.

[0022] Furthermore, when the first precipitation reaction is carried out in step S2, the specific ratios of alkali dropping salt and salt dropping alkali are divided into high core ratio, high extension ratio and balanced ratio.

[0023] The high core ratio is that the amount ratio of the part of the alkaline solution C to the part of the salt solution B is (1-2):1;

[0024] The high extension ratio is that the amount ratio of the part of the alkaline solution C to the part of the salt solution B is specifically 1:(2-4) used in step S2;

[0025] The equilibrium ratio is that the amount ratio of the alkaline solution C to the salt solution B is 1:(1-2) in step S2.

[0026] Furthermore, the dripping speed of alkali-salt and salt-alkali is divided into large core speed, large "tentacle" speed and average speed.

[0027] The specific large core speed refers to the ratio of the drop speed when adding a portion of the salt solution B to the drop speed when adding the alkali solution C (1-2):1;

[0028] The large "antenna" speed refers to the ratio of the drop speed when adding part of the salt solution B to the drop speed when adding the alkaline solution C is 1:(2-4);

[0029] The average speed refers to the ratio of the drop speed when a portion of the salt solution B is added dropwise to the drop speed when the alkali solution C is added dropwise, which is 1:(1-2).

[0030] A catalyst for preparing methanol from biomass synthesis gas is prepared by the above-mentioned method for preparing the catalyst for preparing methanol from biomass synthesis gas.

[0031] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0032] First, one or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0033] A basic structure is formed by the reaction of salt solution B and alkaline solution C, and then the structure is further adjusted and optimized by adding salt solution A in the second precipitation, so that a catalyst with a more complex and multi-level structure is formed, thereby improving the catalytic activity; and because salt solution B is precipitated and aged first, it is more stable, and the combination with the subsequent precipitate of salt solution A is more stable, and it forms a wrapping of the precipitate, so that it is more stably loaded on the carrier. When the first precipitate is precipitated twice with mixed salt A, it can provide a more "rough" surface, which is conducive to more delicate and uniform dispersion of active components;

[0034] Second, the gradual addition of alkali solution forms a more uniform precipitate, avoiding drastic changes in local pH values, so that the precipitation reaction proceeds under more uniform conditions; the gradual addition of alkali solution makes the reaction conditions milder and more controllable, resulting in the formation of finer and more dispersed precipitate particles; the porosity and specific surface area of ​​the precipitate are also affected; a more delicate precipitation process forms a carrier with higher porosity and specific surface area; the carrier generated by milder reaction conditions has better chemical stability because its internal structure is more uniform;

[0035] Third, the raw materials are first dripped into alkali solution to obtain larger particles. When the salt solution is gradually dripped into a large amount of alkali solution, due to the relatively high concentration of the alkali, the dripped salt solution will quickly react with the alkali and easily form larger particles, resulting in a relatively compact precipitate with fewer voids and extremely high stability. Then, on the basis of the larger particle precipitation core, the alkali solution is dripped into the raw materials to continue the reaction, extending "tentacles" with high porosity and specific surface area. The catalyst particles finally obtained are "coral particles" with a solid and stable center, a large and rough epitaxial surface area, and many voids. When combined with the second precipitation, it can not only completely wrap its precipitation, but also directly have high stability as a carrier without loading. Since the precipitation core is dense and stable, the stability of the overall precipitation is greatly improved. When loaded on the carrier, it has a large bonding surface with the carrier, and the precipitation core is not easy to fall off, which further improves the stability of the catalyst.

[0036] Fourthly, by controlling the ratio of salt and alkali in the alkali-salt and salt-alkali stages and the dripping speed, the size and density of the core and "tentacles" of the "coral particles" can be controlled. When the amount of alkali in the salt-salt stage accounts for a large proportion, the volume of the "tentacles" is larger, the dripping speed is slower, the diffusion rate of the alkali solution in the salt solution is slower, the concentration gradient of the reactants is smaller, the reaction rate is slower, the generated precipitated particles are larger, and the specific surface area of ​​the precipitate is larger, and vice versa. DETAILED DESCRIPTION

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs; the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the term "and / or" used herein includes any and all combinations of one or more related listed items.

[0038] Embodiment 1

[0039] The preparation method of the catalyst for producing methanol from biomass syngas of the present application comprises the following steps:

[0040] S1, dissolving zinc nitrate and aluminum nitrate in water to form a zinc-aluminum mixed salt solution A, dissolving zinc nitrate, aluminum nitrate, copper nitrate and magnesium nitrate in water to form a copper-zinc-magnesium-aluminum mixed salt solution B, and dissolving sodium carbonate in water to form an alkaline solution C;

[0041] The mass ratio of zinc, aluminum, copper and magnesium in zinc nitrate, aluminum nitrate, copper nitrate and magnesium nitrate is (3-5): (1-3): (10-15): (0.3-1); the concentration of sodium carbonate in the alkaline solution C is 2.5 mol / L;

[0042] The molar ratio of zinc in salt solution A to that in salt solution B is 1:6-1:2;

[0043] The molar ratio of aluminum in salt solution A to that in salt solution B is 2:1-16:1;

[0044] S2, performing the first step of precipitation reaction, i.e., under stirring, adding salt solution B and alkaline solution C to the reaction tank containing deionized water at the same time, reacting to generate precipitate I, and stopping the addition of alkaline solution C after the addition of salt solution B is completed, and continuing aging for a certain period of time;

[0045] S3. After aging, the precipitate is filtered and washed, and the filter cake obtained by filtration is dispersed into the mixed salt solution A to form a highly dispersed suspension slurry D;

[0046] S4, performing a second step precipitation reaction, i.e., under stirring, simultaneously adding the suspension slurry D and the alkaline solution C to the reaction tank containing deionized water, reacting to generate a precipitate II, and stopping the addition of the alkaline solution C after the addition of the suspension slurry D is completed, and continuing aging for a certain period of time;

[0047] S5. After aging is completed, the precipitate is filtered and washed, and the filter cake obtained by filtration is dried;

[0048] S6. Decomposing the dried product at low temperature, adding graphite to the decomposition product, mixing them evenly, and shaping the mixture to obtain a methanol synthesis catalyst; the temperature of the low temperature decomposition is 300-400° C., and the time is 2-6 hours; the amount of the graphite is 1-3wt% of the mass of the mixture.

[0049] Wherein, the precipitation reaction temperature of step S2 and step S4 is 70-80°C, the pH value is 6.0-8.0, and the aging temperature is the same as the reaction temperature;

[0050] The aging time of step S2 is 15-60 minutes, and the aging time of step S4 is 60-120 minutes.

[0051] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0052] First, a basic structure is formed by the reaction of salt solution B and alkaline solution C. Then, in the second precipitation, the salt solution A is added to further adjust and optimize the structure, so that a catalyst with a more complex and multi-level structure is formed, thereby improving the catalytic activity. In addition, since the salt solution B is precipitated and aged first, it is more stable, and the combination with the subsequent precipitate of the salt solution A is more stable, and the salt solution A is wrapped to be more stably loaded on the carrier. When the first precipitate is precipitated for the second time with the mixed salt A, a more "rough" surface can be provided, which is conducive to a more delicate and uniform dispersion of the active components.

[0053] By first precipitating a multi-component mixture, it has a more solid internal structure. During the secondary precipitation process, the solid structure can more effectively "lock" the active components, thereby enhancing the overall stability of the catalyst;

[0054] The step-by-step precipitation forms a more uniform metal distribution, thereby increasing the number and distribution of active sites of the catalyst; in addition, the two-step precipitation can more effectively control the ratio and interaction of each metal component, thereby optimizing the selectivity and activity of the catalyst;

[0055] In the second precipitation reaction, the filter cake obtained by filtration is dispersed into the mixed salt solution A to form a highly dispersed suspension slurry D, and then precipitation is performed to improve the uniformity and stability of the product, reduce particle agglomeration, and obtain more evenly distributed metal oxide particles.

[0056] Embodiment 2

[0057] The above embodiment improves the stability of the catalyst by first precipitating a mixture with more components and then mixing and precipitating with other components. In order to improve its catalytic ability, the raw materials and the alkali solution are added dropwise at the same time, and the raw materials are added dropwise into the alkali solution instead, which is a further improvement on the basis of the first embodiment.

[0058] When the first precipitation reaction is performed in the above step S2, the salt solution B is poured into the reaction tank containing deionized water under stirring, and then the alkaline solution C is added dropwise to react until no precipitate is generated, and after the alkaline solution C is added dropwise, the aging is continued for a certain period of time;

[0059] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0060] Gradually adding alkali solution forms a more uniform precipitate, avoiding drastic changes in local pH values, so that the precipitation reaction proceeds under more uniform conditions; Gradually adding alkali solution makes the reaction conditions milder and more controllable, resulting in the formation of finer and more dispersed precipitate particles; The porosity and specific surface area of ​​the precipitate are also affected; A more delicate precipitation process forms a carrier with higher porosity and specific surface area; The carrier generated by milder reaction conditions has better chemical stability because its internal structure is more uniform;

[0061] Carriers with higher porosity and specific surface area provide more active sites, thereby improving catalytic activity; at the same time, a more stable chemical structure also maintains the long-term activity of the catalyst; precipitates with a large specific surface area have more contact surfaces with the surrounding environment, increasing their chances of reaction with gases in the environment, and more contact and combination with the secondary precipitates, making the components in the catalyst more tightly combined and increasing the contact area between the catalyst and the air; precipitates with many voids have better buffering capacity and can resist corrosion from external chemicals, thereby maintaining their chemical stability; precipitates with a large specific surface area and many voids have better heat dissipation performance when heated, improving their thermal stability; precipitates with many voids may have better compression resistance to a certain extent, and the voids inside them can act as a buffer.

[0062] Embodiment 3

[0063] Example 2: The stability of the catalyst is enhanced by dripping alkali solution into salt solution B; in order to increase its service life and catalytic efficiency, part of the raw materials are dripped into the alkali solution, the precipitate is mixed with the unreacted raw materials, and then the alkali solution is dripped, which is further improved on the basis of Example 2.

[0064] When the first precipitation reaction is performed in the above step S2, part of the alkaline solution C is poured into a reaction tank containing deionized water under stirring, and then part of the salt solution B is added dropwise for reaction. After the addition of the salt solution B is completed, the aging is continued for a certain time. After that, the precipitate is taken out and placed in another reaction tank containing deionized water, the remaining salt solution B is poured in, and the alkaline solution C is added dropwise until no more precipitate is generated. After the addition of the alkaline solution C is completed, the aging is continued for a certain time.

[0065] The part of the alkaline solution C and the part of the salt solution B are specifically 50% of the amount of the alkaline solution C and the salt solution B used in step S2.

[0066] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0067] First, larger particles are obtained by dripping the raw materials into alkali solution. When the salt solution is gradually dripped into a large amount of alkali solution, due to the relatively high concentration of the alkali, the dripped salt solution will quickly react with the alkali and easily form larger particles, resulting in a relatively compact precipitate with fewer voids and extremely high stability. Then, based on the larger particle precipitation core, the alkali solution is dripped into the raw materials to continue the reaction, extending "tentacles" with high porosity and specific surface area. The catalyst particles finally obtained are "coral particles" with a solid and stable center, a large and rough epitaxial surface area, and many voids. When combined with the second precipitation, it can not only completely wrap the precipitation, but also directly have high stability as a carrier without loading. Since the precipitation core is dense and stable, the stability of the overall precipitation is greatly improved. When loaded on the carrier, it has a large bonding surface with the carrier, and the precipitation core is not easy to fall off, which further improves the stability of the catalyst.

[0068] Embodiment 4

[0069] In Example 3, the stability of the catalyst is further improved by using "coral particles". In order to enable it to cope with different reaction conditions, further improvements are made on the basis of Example 3.

[0070] When the first precipitation reaction is carried out in the above step S2, the specific ratio of alkali dropping salt and salt dropping alkali is divided into high core ratio, high extension ratio and balanced ratio;

[0071] The specific high core ratio is that the amount ratio of the part of the alkaline solution C to the part of the salt solution B is (1-2):1;

[0072] The high extension ratio is that the amount ratio of the part of the alkaline solution C to the part of the salt solution B is specifically 1:(2-4) used in step S2;

[0073] The equilibrium ratio is that the amount ratio of the alkaline solution C to the salt solution B is 1:(1-2) in step S2.

[0074] The dripping speed of alkali dripping salt and salt dripping alkali can be divided into large core speed, large "tentacle" speed and average speed.

[0075] The specific large core speed refers to the ratio of the drop speed when adding a portion of the salt solution B to the drop speed when adding the alkali solution C (1-2):1;

[0076] The large "antenna" speed refers to the ratio of the drop speed when adding part of the salt solution B to the drop speed when adding the alkaline solution C is 1:(2-4);

[0077] The average speed refers to the ratio of the drop speed when a part of the salt solution B is added dropwise to the drop speed when the alkaline solution C is added dropwise, which is 1:(1-2).

[0078] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0079] The size and density of the core and "tentacles" of the "coral particles" are controlled by controlling the ratio of salt to alkali and the dripping speed in the alkali-salt and salt-alkali stages. When the alkali-salt stage accounts for a large proportion, the "tentacles" are larger in volume, the dripping speed is slower, the diffusion rate of the alkali solution in the salt solution is slower, the concentration gradient of the reactants is smaller, the reaction rate is slower, the generated precipitation particles are larger, and the specific surface area of ​​the precipitation is larger, and vice versa.

[0080] For example, when using a high core ratio and a large core speed, the core of the "coral particles" is dense and large in size, and has a higher adaptability to high-pressure environments; when using a high extension ratio and a large "tentacle" speed, the "coral particles" are more fluffy and have a better catalytic effect at high temperatures; the combination of a high core ratio and a large "tentacle" speed has a better effect at high airspeeds.

[0081] Sample particle size: 20-40 mesh. Filling volume: 5mL (2mL catalyst + 3mL inert carrier). Sample activation: Before the sample is activated and heat-resistant, it is reduced with a hydrogen-nitrogen mixed gas of low concentration hydrogen (H2 / N2=5 / 95 (volume ratio)) for 10-12h, and the maximum reduction temperature is 220℃.

[0082] Activity test: The raw gas composition is: CO = 13.0-14.0%, CO2 = 4.0-5.0%, N2 = 10%, the rest is H2, the reaction pressure is 5.0MPa, and the space velocity is 10000h -1 , the reaction temperature is 235-245°C, and the CO conversion rate before heat resistance and the OH space-time yield (the amount of methanol produced per mL of catalyst per hour) are measured.

[0083] Heat-resistant activity test: After the initial activity of the sample is determined, the pressure is reduced to 0.1MPa, the reaction temperature is increased to 400℃, and the air velocity is reduced to 3000h -1 After 10 hours of post-heat treatment, the catalyst was restored to the above-mentioned activity test conditions, and the CO conversion rate and CH3OH space-time yield after heat resistance were measured. The ratio of methanol space-time yield after heat resistance test to initial methanol space-time yield was used to indicate the thermal stability of the catalyst.

[0084] Stability test: After the sample is tested for heat resistance, it is placed under a pressure of 5.0 MPa and an air velocity of 10,000 h -1 , maintained at 235-245°C for 7 days, and the stability was expressed by the ratio of the space-time yield after the stability experiment to the initial methanol space-time yield.

[0085] The above test method was used to evaluate the activity of the catalysts of Examples 1 to 4 and the comparative example (a high stability methanol synthesis catalyst of application number CN202011110409.0), wherein Example 4 takes the combination of high extension ratio and large "tentacle" speed as an example, and the results are as follows:

[0086]

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a catalyst for producing methanol from biomass synthesis gas, characterized in that: The following steps are involved: S1, dissolving zinc nitrate and aluminum nitrate in water to form a zinc-aluminum mixed salt solution A, dissolving zinc nitrate, aluminum nitrate, copper nitrate and magnesium nitrate in water to form a copper-zinc-magnesium-aluminum mixed salt solution B, and dissolving sodium carbonate in water to form an alkaline solution C; The mass ratio of zinc, aluminum, copper and magnesium in zinc nitrate, aluminum nitrate, copper nitrate and magnesium nitrate is (3-5): (1-3): (10-15): (0.3-1); the concentration of sodium carbonate in the alkaline solution C is 2.5 mol / L; The molar ratio of zinc in salt solution A to that in salt solution B is 1:6-1:2; The molar ratio of aluminum in salt solution A to that in salt solution B is 2:1-16:1; S2, performing the first step of precipitation reaction, i.e., adding salt solution B and alkaline solution C to a reaction tank containing deionized water under stirring, reacting to generate precipitate I, and continuing aging for a certain period of time after the addition is completed; S3. After aging, the precipitate is filtered and washed, and the filter cake obtained by filtration is dispersed into the mixed salt solution A to form a highly dispersed suspension slurry D; S4, performing a second step precipitation reaction, i.e., under stirring, simultaneously adding the suspension slurry D and the alkaline solution C to the reaction tank containing deionized water, reacting to generate a precipitate II, and stopping the addition of the alkaline solution C after the addition of the suspension slurry D is completed, and continuing aging for a certain period of time; S5. After aging is completed, the precipitate is filtered and washed, and the filter cake obtained by filtration is dried; S6. Decompose the dried product at low temperature, add graphite to the decomposition product, mix them evenly, and shape the mixture to obtain a methanol synthesis catalyst; the temperature of the low temperature decomposition is 300-400°C, and the time is 2-6 hours; the amount of the graphite is 1-3wt% of the mass of the mixture.

2. The method for preparing a catalyst for producing methanol from biomass synthesis gas according to claim 1, characterized in that: The precipitation reaction temperature of step S2 and step S4 is 70-80° C., the pH value is 6.0-8.0, and the aging temperature is the same as the reaction temperature.

3. The method for preparing a catalyst for producing methanol from biomass synthesis gas according to claim 1, characterized in that: The aging time of step S2 is 15-60 minutes, and the aging time of step S4 is 60-120 minutes.

4. The method for preparing a catalyst for producing methanol from biomass synthesis gas according to claim 1, characterized in that: In step S2, the salt solution B and the alkaline solution C are added dropwise simultaneously.

5. The method for preparing a catalyst for producing methanol from biomass synthesis gas according to claim 1, characterized in that: In step S2, the salt solution B and the alkaline solution C are added by pouring the salt solution B into a reaction tank containing deionized water, and then adding the alkaline solution C dropwise to react until no precipitate is generated.

6. The method for preparing a catalyst for producing methanol from biomass synthesis gas according to claim 5, characterized in that: When the first precipitation reaction is performed in step S2, part of the alkaline solution C is poured into a reaction tank containing deionized water under stirring, and then part of the salt solution B is added dropwise for reaction. After the addition of the salt solution B is completed, aging is continued for a certain time. Then, the precipitate is taken out and placed in another reaction tank containing deionized water, and the remaining salt solution B is poured in. The alkaline solution C is titrated against the salt solution B until no more precipitate is generated. After the addition of the alkaline solution C is completed, aging is continued for a certain time.

7. The method for preparing a catalyst for producing methanol from biomass synthesis gas according to claim 6, characterized in that: The part of the alkaline solution C and the part of the salt solution B are specifically 50% of the amount of the alkaline solution C and the salt solution B used in step S2.

8. The method for preparing a catalyst for producing methanol from biomass synthesis gas according to claim 6, characterized in that: When the first precipitation reaction is performed in step S2, the specific ratios of alkali dropping salt and salt dropping alkali are high core ratio, high extension ratio and balanced ratio; The high core ratio is that the amount ratio of the part of the alkaline solution C to the part of the salt solution B is (1-2):1; The high extension ratio is that the amount ratio of the part of the alkaline solution C to the part of the salt solution B is specifically 1:(2-4) used in step S2; The equilibrium ratio is that the amount ratio of the alkaline solution C to the salt solution B is 1:(1-2) in step S2.

9. The method for preparing a catalyst for producing methanol from biomass synthesis gas according to claim 6, characterized in that: The dripping speed of alkali dripping salt and salt dripping alkali can be divided into large core speed, large "tentacle" speed and average speed The specific large core speed refers to the ratio of the drop speed when adding a portion of the salt solution B to the drop speed when adding the alkali solution C (1-2):1; The large "antenna" speed refers to the ratio of the drop speed when adding part of the salt solution B to the drop speed when adding the alkaline solution C is 1:(2-4); The average speed refers to the ratio of the drop speed when a part of the salt solution B is added dropwise to the drop speed when the alkaline solution C is added dropwise, which is 1:(1-2).

10. A catalyst for preparing methanol from biomass synthesis gas, characterized in that: The catalyst is prepared by the method for preparing the catalyst for producing methanol from biomass synthesis gas according to any one of claims 1 to 9.

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