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

Abstract

The present application discloses a catalyst for producing methanol from biomass synthesis gas and a preparation method thereof, which relates to the technical field of methanol preparation, comprising: S1, preparing a salt solution A, a salt solution B, and an alkaline solution C; S2, performing a first precipitation reaction; S3, forming a highly dispersed suspension slurry D; S4, performing a second precipitation reaction; S5, after aging, filtering and washing the precipitate, and drying the filter cake obtained by filtration; S6, low-temperature decomposing the dried product, and adding graphite to form a catalyst; the present application makes the salt solution B more stable by first performing precipitation and aging on the salt solution B, making the salt solution B more stable, and forming a wrapping around the salt solution B, so that the salt solution B is more stably loaded on the carrier, thereby making the catalyst more stable.

Description

Technical Field

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

[0002] Methanol, a fundamental organic raw material in C1 chemistry, is primarily used to produce methyl tert-butyl ether (MTBE), dimethyl ether, formaldehyde, methyl formate, acetic acid and its derivatives, fumarate (DMF), gasoline, and other products. It can also be used as a potential automotive alcohol ether fuel and fuel cell fuel. With the widespread application of methanol gasoline, technological advances and industrial breakthroughs in methanol protein and methanol-to-olefins, and the continued development of downstream products such as dimethyl ether, acetic acid, methyl formate, and dimethyl carbonate, the demand for methanol is increasing, presenting a promising future for its application. Producing methanol using synthesis gas (syngas) as a raw material through liquid or gas-phase catalytic reactions is currently a major industrial method. Synthesis gas can be obtained by biomass gasification, which involves converting biomass materials such as wood, straw, hemp palm, and fruit shells into gas under continuous heating. The gas produced during biomass gasification is primarily composed of CO, H2, CH4, CO2, and N2, making the use of biomass as a raw material both economically and environmentally beneficial. Copper-based catalysts are commonly used in methanol production, with copper being considered the primary active component. However, copper alone has very poor activity, and the introduction of other components can significantly 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, Chinese patent application number CN202011110409.0, a method for preparing a high-stability methanol synthesis catalyst. The method adopts an improved two-step precipitation method, specifically comprising: co-precipitating a mixed salt solution of zinc nitrate and aluminum nitrate with an alkaline solution and performing an aging reaction; 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 the highly dispersed suspension slurry with an alkaline solution and performing an aging reaction; and then filtering, washing, drying, roasting and tableting to obtain a methanol synthesis catalyst. The invention is scientifically designed, simple in method and easy to operate. 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 relatively 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 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 form precipitate I, and continuing aging for a certain period of time after the addition is completed;

[0012] S3. After aging is completed, 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., adding the suspension slurry D and the alkaline solution C simultaneously to the reaction tank containing deionized water under stirring, reacting to form 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 uniformly, and shaping the mixture to obtain a methanol synthesis catalyst; the low temperature decomposition temperature is 300-400° C., and the time is 2-6 hours; the amount of the graphite is 1-3 wt% of the mass of the mixture;

[0016] Furthermore, the precipitation reaction temperature in 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 the reaction tank containing deionized water, and then adding the alkaline solution C dropwise to react until no precipitate is generated.

[0020] Furthermore, in step S2, when performing the first precipitation reaction, a portion of the alkaline solution C is poured into a reaction tank containing deionized water under stirring, and then a portion 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. The precipitate is then 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 then 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.

[0021] Furthermore, the portion of the alkaline solution C and the portion 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 performed 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 and the part of the salt solution B is (1-2):1;

[0024] The high extension ratio is that the ratio of the alkaline solution C to the salt solution B is 1:(2-4) in amount.

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

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

[0027] Specifically, the maximum 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 alkaline solution C, which is (1-2):1;

[0028] The maximum "antenna" speed refers to the ratio of the droplet speed of the salt solution B to the droplet speed of the alkaline solution C when the reaction is added dropwise, which is 1:(2-4);

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

[0030] A catalyst for producing methanol from biomass synthesis gas is prepared by the above-mentioned method for preparing the catalyst for producing 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 this application have at least the following technical effects or advantages:

[0033] A base structure is formed through the reaction of salt solution B and alkaline solution C. This structure is then further adjusted and optimized by the addition of salt solution A in the second precipitation, resulting in a catalyst with a more complex, multi-level structure, thereby improving catalytic activity. Furthermore, because salt solution B is first precipitated and aged, it is more stable, combining more stably with the subsequent precipitate of salt solution A, forming a wrap around it, and allowing it to be more stably loaded on the carrier. The second precipitation of the first precipitate with mixed salt A provides a rougher surface, which facilitates a more detailed and uniform dispersion of the active components.

[0034] Secondly, the gradual addition of alkali solution forms a more uniform precipitate, avoiding drastic changes in local pH values, thereby allowing the precipitation reaction to proceed under more uniform conditions. The gradual addition of alkali solution makes the reaction conditions milder and more controllable, promoting the formation of finer and more dispersed precipitate particles. The porosity and specific surface area of the precipitate are also affected. The more delicate precipitation process forms a carrier with higher porosity and specific surface area. The carrier produced under milder reaction conditions has better chemical stability because its internal structure is more uniform.

[0035] Third, larger particles are first obtained by dripping alkali solution into the raw materials. When the salt solution is gradually dripped into a large amount of alkali solution, the alkali concentration is relatively high, and the dripped salt solution will quickly react with the alkali to easily form larger particles, resulting in a denser precipitate with fewer voids and extremely high stability. Then, on the basis of the larger particle precipitation core, the reaction is continued by dripping alkali solution into the raw materials to extend "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 dripping salt 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 precipitate 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 those skilled in the art to which this invention pertains; the terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention; the term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0038] Example 1

[0039] The preparation method of the catalyst for producing methanol from biomass synthesis gas in this 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., adding salt solution B and alkaline solution C simultaneously to a reaction tank containing deionized water under stirring, reacting to form precipitate I, 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 is completed, 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., adding the suspension slurry D and the alkaline solution C simultaneously to the reaction tank containing deionized water under stirring, reacting to form 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. 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 low temperature decomposition temperature is 300-400° C., and the time is 2-6 hours; the amount of the graphite is 1-3 wt% of the mass of the mixture.

[0049] The precipitation reaction temperature in 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 base structure is formed through the reaction of salt solution B and alkaline solution C. Then, in the second precipitation, the addition of salt solution A further adjusts and optimizes this structure, forming a catalyst with a more complex, multi-level structure, thereby improving catalytic activity. Furthermore, because salt solution B is precipitated and aged first, it is more stable, combining more stably with the subsequent precipitate of salt solution A, forming a wrap around it, and making it more stably loaded on the carrier. The second precipitation of the first precipitate with mixed salt A can provide a more "rough" surface, which is conducive to a more detailed 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 creates a more uniform metal distribution, thereby increasing the number and distribution of active sites in the catalyst. In addition, the two-step precipitation allows for more effective control of the ratio and interaction of the metal components, 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] Example 2

[0057] The above embodiment improves the stability of the catalyst by first precipitating the mixture with more components and then mixing and precipitating with other components. In order to improve its catalytic ability, the raw materials are added dropwise into the alkali solution instead of adding them simultaneously with the alkali solution, which is a further improvement on the basis of Example 1.

[0058] During the first precipitation reaction in step S2, salt solution B is poured into a reaction tank containing deionized water under stirring, and then alkaline solution C is added dropwise to react until no more precipitate is generated. After the addition of alkaline solution C is completed, 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] The gradual addition of alkali solution forms a more uniform precipitate, avoiding drastic local pH changes, allowing the precipitation reaction to proceed under more uniform conditions. The gradual addition of alkali solution results in milder and more controllable reaction conditions, leading to the formation of finer and more dispersed precipitate particles. The porosity and specific surface area of the precipitate are also affected. A more detailed precipitation process results in a carrier with higher porosity and specific surface area. Carriers produced under milder reaction conditions have better chemical stability due to their more uniform internal structure.

[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 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 the erosion of 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] Example 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 material is dripped into the alkali solution, the precipitate is mixed with the unreacted raw material, and then the alkali solution is dripped, which is further improved on the basis of Example 2.

[0064] During the first precipitation reaction in step S2, a portion of the alkaline solution C is poured into a reaction tank containing deionized water under stirring, and then a portion of the salt solution B is added dropwise for reaction. After the addition of the salt solution B is completed, the reaction is continued for a certain period of time. The precipitate is then taken out and placed in another reaction tank containing deionized water, and the remaining salt solution B is poured into the reaction tank, 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 reaction is continued for a certain period of 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 alkali solution into the raw materials. When the salt solution is gradually dripped into a large amount of alkali solution, the alkali concentration is relatively high, and the dripped salt solution will quickly react with the alkali to easily form larger particles, resulting in a denser precipitate with fewer voids and extremely high stability. Then, on the basis of the larger particle precipitation core, the reaction is continued by dripping alkali solution into the raw materials, 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.

[0068] Example 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 ratios of alkali dropping salt and salt dropping alkali are divided into high core ratio, high extension ratio and balanced ratio;

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

[0072] The high extension ratio is that the ratio of the alkaline solution C to the salt solution B is 1:(2-4) in amount.

[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] Specifically, the maximum 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 alkaline solution C, which is (1-2):1;

[0076] The maximum "antenna" speed refers to the ratio of the droplet speed of the salt solution B to the droplet speed of the alkaline solution C when the reaction is added dropwise, which is 1:(2-4);

[0077] The average speed refers to the ratio of the dropwise addition speed when a portion of the salt solution B is added dropwise to the dropwise addition speed when a portion of 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] By controlling the ratio of salt to alkali and the dripping speed in the alkali-salt and salt-alkali stages, the size and density of the core and "tentacles" of the "coral particles" can be controlled. When the amount of alkali dripping salt accounts for a larger proportion, the "tentacles" will be larger and the dripping speed will be slower. The diffusion rate of the alkali solution in the salt solution will be slower, the concentration gradient of the reactants will be smaller, the reaction rate will be slower, the generated precipitate particles will be larger, and the specific surface area of the precipitate will be 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 volume, 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. Loading volume: 5 mL (2 mL catalyst + 3 mL inert carrier). Sample activation: Before activation and heat resistance testing, the sample was reduced using a low-concentration hydrogen (H2 / N2 = 5 / 95 (volume ratio)) hydrogen and nitrogen mixture for 10-12 hours, with a maximum reduction temperature of 220°C.

[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 5.0 MPa, and the space velocity is 10000h -1 The reaction temperature was 235-245°C, and the CO conversion rate and OH space-time yield (the amount of methanol produced per mL of catalyst per hour) before heat resistance were measured.

[0083] Activity test after heat resistance: 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 space velocity is reduced to 3000h -1 After a 10-hour post-heat treatment, the catalyst was returned to the aforementioned activity test conditions and the CO conversion and CH3OH space-time yield after heat resistance were measured. The ratio of the methanol space-time yield after the heat resistance test to the 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 heated at a pressure of 5.0 MPa and a space velocity of 10,000 h -1 , maintained at 235-245℃ for 7 days, and the stability is 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 with application number CN202011110409.0). In Example 4, the combination of a high extension ratio and a large "tentacle" speed was used as an example. The results are as follows:

[0086]

[0087] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Various modifications and variations are readily apparent to those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection 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 ratios of zinc, aluminum, copper, and magnesium in zinc nitrate, aluminum nitrate, copper nitrate, and magnesium nitrate are (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., pouring part of the alkaline solution C into a reaction tank containing deionized water under stirring, and then adding part of the salt solution B dropwise for reaction, and continuing aging after the addition of the salt solution B is completed, and then taking out the precipitate and placing it in another reaction tank containing deionized water, and pouring the remaining salt solution B, and then titrating the salt solution B with the alkaline solution C until no more precipitate is generated, and continuing aging after the addition of the alkaline solution C is completed; S3. After aging is completed, 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., adding the suspension slurry D and the alkaline solution C simultaneously to the reaction tank containing deionized water under stirring, reacting to form 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 low temperature decomposition temperature is 300-400°C, and the time is 2-6 hours; the amount of graphite used 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, 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.

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

4. A catalyst for producing 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 3.

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