A methanol synthesis catalyst and a method for its preparation

Abstract

This disclosure relates to a methanol synthesis catalyst and its preparation method. In this methanol synthesis catalyst, zero-valent copper is uniformly distributed throughout the catalyst structure, improving copper dispersion. Furthermore, the copper crystals in the catalyst are smaller than those obtained in existing technologies, which not only enhances the initial activity, activity retention rate, and methanol selectivity of the catalyst.

Description

Technical Field

[0001] This disclosure relates to the field of catalyst preparation, and more specifically, to a methanol synthesis catalyst and a method for preparing the same. Background Technology

[0002] Methanol, as an important chemical raw material, can be used to synthesize a variety of high-value fuels and chemicals. In recent years, the synthesis of methanol via CO / CO2 hydrogenation has not only increased methanol production but also enabled the resource utilization of carbon dioxide, showing promising application prospects. Cu-based catalysts are commonly used in this reaction for methanol synthesis. Recent studies have shown that both divalent copper ions and elemental copper in Cu-based catalysts are active sites for the CO / CO2 hydrogenation synthesis of methanol, and their amounts directly affect the CO / CO2 conversion and methanol production.

[0003] In existing technologies, when constructing the active sites of Cu-based catalysts, one approach is to use a reducing agent to directly act on the nitrate, achieving catalyst self-reduction during calcination; another approach is to add a reducing agent after co-precipitation to adjust the active sites. The former is not conducive to the formation of the basic carbonate precursor structure and is detrimental to the synergistic effect of copper and zinc; the latter, by choosing the reducing agent NaBH4, introduces impurities such as sodium, which are harmful to catalyst performance, and the introduction of formic acid easily causes the decomposition of the effective basic carbonate precursor. Summary of the Invention

[0004] The purpose of this disclosure is to provide a methanol synthesis catalyst and its preparation method, in order to solve the problem of poor catalyst performance caused by the use of formic acid and NaBH4 in the prior art.

[0005] To achieve the above objectives, the first aspect of this disclosure provides a methanol synthesis catalyst comprising alumina, zinc oxide, copper oxide, and elemental copper. Based on the total weight of the methanol synthesis catalyst, the content of alumina is 1.93-21.62% by weight, the content of zinc oxide is 21.57-44.13% by weight, the content of copper oxide is 37.74-67.46% by weight, and the content of elemental copper is 0.84-4.31% by weight. At least a portion of the copper element exists in the form of copper grains, the average grain size of which is 4-8 nm.

[0006] Optionally, based on the total weight of the methanol synthesis catalyst, the content of alumina is 5.30-13.84% by weight, the content of zinc oxide is 21.66-38.05% by weight, the content of copper oxide is 43.19-65.63% by weight, and the content of elemental copper is 2.47-4.32% by weight.

[0007] Optionally, the molar ratio of copper oxide to copper in the elemental copper is (5-30):1.

[0008] A second aspect of this disclosure provides a method for preparing the methanol synthesis catalyst described in the first aspect, the method comprising: S1. Aluminum source, copper source, zinc source and precipitant are subjected to co-precipitation reaction to obtain catalyst preform; S2. The catalyst preform is impregnated with a reducing solution, and then calcined and passivated in sequence. The reducing agent in the reducing solution includes copper formate and / or copper acetate; The calcination conditions include: under an inert atmosphere, a temperature of 300-400℃, and a time of 2-18h.

[0009] Optionally, the aluminum source includes one or more of Al(NO3)3, Al2(SO4)3, and AlCl3; the copper source includes one or more of Cu(NO3)2, CuSO4, and CuCl2; the zinc source includes one or more of Zn(NO3)2, ZnSO4, and ZnCl2; the precipitant includes a first precipitant and a second precipitant; the first precipitant and the second precipitant are each independently selected from carbonates and / or bicarbonates; and the reducing solution is a copper formate solution.

[0010] Optionally, the impregnation includes: dissolving the reducing agent in water to obtain the reducing solution; the reducing agent is copper formate monohydrate and / or copper formate tetrahydrate; the content of the reducing agent in the reducing solution is 1.96-16.6% by weight.

[0011] Optionally, the impregnation conditions include: a temperature of 10-45°C, a time of 8-24 h, and a molar ratio of the reducing agent to Cu in the copper source of (0.1-1):1.

[0012] Optionally, the passivation conditions include: under an inert atmosphere, the temperature is 10-45℃ and the time is 2-18h; the inert atmosphere includes one or more of nitrogen, argon and helium; and the oxygen content in the inert atmosphere is less than 1% by volume.

[0013] Optionally, the molar ratio of the amounts of copper source, zinc source and aluminum source, in terms of elements, is (20-60):(20-40):(3-30).

[0014] Optionally, step S1 further includes: S11. The aluminum source is configured into an aluminum salt solution, the copper source and the zinc source are configured into a copper-zinc mixed salt solution, the first precipitant is configured into a first precipitant solution, and the second precipitant is configured into a second precipitant solution; S12. React the aluminum salt solution and the first precipitant solution at 40-90°C to obtain a first suspension with a pH of 5-10. S13. The copper-zinc mixed salt solution and the second precipitant solution are introduced into the first suspension and co-precipitated at a temperature of 30-90°C to obtain a second suspension with a pH of 6-9. S14. The second suspension is subjected to aging, filtration, washing and drying in sequence to obtain the catalyst preform.

[0015] Through the above technical solution, zero-valent copper is uniformly distributed in the structure of the methanol synthesis catalyst, which can improve the copper dispersion of the methanol synthesis catalyst. At the same time, the average particle size of the copper crystals in the methanol synthesis catalyst is smaller than that of copper crystals obtained by existing technologies, which can not only improve the initial activity, activity retention rate and methanol selectivity of the methanol synthesis catalyst.

[0016] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Detailed Implementation

[0017] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0018] The first aspect of this disclosure provides a methanol synthesis catalyst comprising aluminum oxide, zinc oxide, copper oxide, and elemental copper. Based on the total weight of the methanol synthesis catalyst, the content of alumina is 1.93-21.62% by weight, the content of zinc oxide is 21.57-44.13% by weight, the content of copper oxide is 37.74-67.46% by weight, and the content of elemental copper is 0.84-4.31% by weight. At least a portion of the copper element exists in the form of copper grains, the average grain size of which is 4-8 nm.

[0019] Through the above technical solution, zero-valent copper is uniformly distributed in the structure of the methanol synthesis catalyst, which can improve the copper dispersion of the methanol synthesis catalyst. At the same time, the average particle size of the copper crystals in the methanol synthesis catalyst is smaller than that of copper crystals obtained by existing technologies, which can not only improve the initial activity, activity retention rate and methanol selectivity of the methanol synthesis catalyst.

[0020] In a preferred embodiment, based on the total weight of the methanol synthesis catalyst, the content of alumina is 5.30-13.84% by weight, the content of zinc oxide is 21.66-38.05% by weight, the content of copper oxide is 43.19-65.63% by weight, and the content of elemental copper is 2.47-4.32% by weight.

[0021] In a preferred embodiment, the average grain size of the copper grains is 5.5-7 nm.

[0022] In a further preferred embodiment, the average grain size of the copper grains can be any one or any two of 5.7nm, 5.9nm, 6.1nm, 6.3nm, 6.5nm, 6.7nm and 6.9nm.

[0023] In this embodiment, the elemental copper described in this disclosure is zero-valent copper obtained from divalent copper in the catalyst through reduction and from the reducing agent through pyrolysis and disproportionation reactions. At least a portion of the elemental copper exists in the form of copper grains, and the average particle size of these copper grains can be detected using conventional methods in the art, such as a Bruker D8 X-ray diffraction system. Compared to catalysts obtained in the prior art, the methanol synthesis catalyst obtained in this application has smaller copper grains, which can further improve the initial activity, activity retention rate, and methanol selectivity of the alcohol synthesis catalyst.

[0024] In one embodiment, the molar ratio of copper in the copper oxide and elemental copper is (5-30):1.

[0025] In a preferred embodiment, the molar ratio of copper oxide to copper in elemental copper can be any one or any combination of 10, 12, 14, 16, 18, 20, 22, 24 and 26.5.

[0026] In this embodiment, the molar ratio of copper in the elemental copper and copper oxide is within a suitable range, which can further improve the initial activity, activity retention rate and methanol selectivity of the alcohol synthesis catalyst.

[0027] A second aspect of this disclosure provides a method for preparing the methanol synthesis catalyst described in the first aspect, the method comprising: S1. Aluminum source, copper source, zinc source and precipitant are subjected to co-precipitation reaction to obtain catalyst preform; S2. The catalyst preform is impregnated with a reducing solution, and then calcined and passivated in sequence. The reducing agent in the reducing solution includes copper formate and / or copper acetate; The calcination conditions include: under an inert atmosphere, a temperature of 300-400℃, and a time of 2-18h.

[0028] Through the above technical solution, this disclosure impregnates the reducing agent into the precipitated catalyst preform, ensuring that the copper element in the reducing agent is uniformly distributed in the precursor structure, thereby improving the copper dispersion of the methanol synthesis catalyst. The impregnated catalyst preform is then calcined in an inert atmosphere, causing the reducing agent to decompose and produce reducing gas and monovalent copper oxide. On one hand, the reducing gas effectively reacts with the copper oxide in the catalyst preform, partially reducing it to form Cu / Cu. 2+ Multiple active sites; on the other hand, monovalent copper oxides can undergo disproportionation reactions to form Cu / Cu 2+ Multiple active sites; finally, the calcined catalyst preform is passivated to protect the formed Cu / Cu 2+ With multiple active sites, it plays a role in the synthesis reaction of methanol, improving the activity and selectivity of copper-based catalysts.

[0029] In one embodiment, step S1 further includes: S11. The aluminum source is configured into an aluminum salt solution, the copper source and the zinc source are configured into a copper-zinc mixed salt solution, the first precipitant is configured into a first precipitant solution, and the second precipitant is configured into a second precipitant solution; S12. React the aluminum salt solution and the first precipitant solution at 40-90°C to obtain a first suspension with a pH of 5-10. S13. The copper-zinc mixed salt solution and the second precipitant solution are introduced into the first suspension and co-precipitated at a temperature of 30-90°C to obtain a second suspension with a pH of 6-9. S14. The second suspension is subjected to aging, filtration, washing and drying in sequence to obtain the catalyst preform.

[0030] In one embodiment, the aluminum source described in this disclosure includes one or more of Al(NO3)3, Al2(SO4)3, and AlCl3.

[0031] In one embodiment, the copper source described in this disclosure includes one or more of Cu(NO3)2, CuSO4, and CuCl2.

[0032] In one embodiment, the zinc source described in this disclosure includes one or more of Zn(NO3)2, ZnSO4, and ZnCl2.

[0033] In one embodiment, the precipitant of this disclosure includes a first precipitant and a second precipitant; the first precipitant and the second precipitant are each independently selected from carbonates and / or bicarbonates.

[0034] In a preferred embodiment, the first precipitant and the second precipitant described herein are each independently selected from one or more of sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate.

[0035] In one embodiment, the concentrations of the aluminum salt solution, copper-zinc mixed salt solution, first precipitant solution, and second precipitant solution in step S11 can be flexibly adjusted according to actual production conditions. For example, the concentrations of the aluminum salt solution, copper-zinc mixed salt solution, first precipitant solution, and second precipitant solution described in this disclosure are each independently 1~3 mol / L.

[0036] In one embodiment, step S12 further includes adding the aluminum salt solution and the first precipitant solution dropwise into a water bath flask and stirring, with the water bath temperature being 40-90°C, and controlling the dropping rate of the first precipitant solution during the entire stirring process so that the pH of the first suspension is 5-10.

[0037] In a preferred embodiment, the water bath temperature in step S12 is 60-80°C, and the pH of the first suspension is 6-9.

[0038] In one embodiment, step S13 further includes adding a copper-zinc mixed salt solution and a second precipitant solution dropwise at a uniform rate to the first suspension obtained in step S12 at a temperature of 30-90°C. During the entire dropwise addition process, the mixture is continuously stirred and the dropwise rate of the second precipitant solution is controlled so that the pH of the second suspension is 6-9.

[0039] In a preferred embodiment, the temperature in step S13 is 60-75°C, and the pH of the second suspension is 6.2-8.

[0040] In a further preferred embodiment, during the entire dripping process described in step S13, the pH of the second suspension is controlled to be 6.5-7.5.

[0041] In one embodiment, the aging conditions described in step S14 include: a temperature of 70-90°C and a time of 1-24 hours.

[0042] In one embodiment, the filtration and washing described in step S14 are conventional choices in the art, and this application does not make any special requirements.

[0043] In one embodiment, the drying conditions in step S14 include: a temperature of 90-120°C and a time of 6-18 hours.

[0044] In one embodiment, in steps S12 and S13, the molar ratio of the amounts of copper source, zinc source and aluminum source, in terms of elements, is (20-60):(20-40):(3-30).

[0045] In a preferred embodiment, the molar ratio of the amounts of copper source, zinc source and aluminum source, in terms of elements, is (35-50):(25-35):(8-20).

[0046] In this embodiment, the term "elemental" as used in this disclosure refers to copper source as copper element, zinc source as zinc element, and aluminum source as aluminum element. When appropriate amounts of copper, zinc, and aluminum sources are used for co-precipitation, the formation of copper-zinc-aluminum co-precipitates can be reduced or suppressed, and the formation of copper-zinc co-precipitates can be promoted, thereby further improving the performance of the methanol synthesis catalyst.

[0047] In one embodiment, step S2 further includes dissolving the reducing agent in water to obtain the reducing solution.

[0048] In a preferred embodiment, the reducing solution is a copper formate solution.

[0049] In a further preferred embodiment, the reducing agent in the copper formate solution is preferably copper formate monohydrate (Cu(CH3COO)2·H2O) and / or copper formate tetrahydrate (Cu(CH3COO)2·4H2O).

[0050] In this embodiment, copper formate impregnated in the precipitated catalyst preform undergoes thermal decomposition under calcination conditions, decomposing into cuprous oxide and carbon monoxide. The carbon monoxide reacts effectively with the copper oxide in the catalyst preform, reducing some of the divalent copper to elemental copper, forming Cu / Cu. 2+ Multiple active sites; cuprous oxide can undergo a disproportionation reaction during calcination to form Cu / Cu 2+ Multiple active sites; among which, the thermal decomposition reaction is The disproportionation reaction is Cu₂O + 2CO → Cu + Cu 2+ + H2O.

[0051] In one embodiment, the reducing agent content in the reducing solution is 1.96~16.6% by weight.

[0052] In a preferred embodiment, the content of reducing agent in the reducing solution can be any one or any two of 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, and 16 wt%.

[0053] In one embodiment, the molar ratio of the reducing agent to Cu in the copper source is (0.1-1):1.

[0054] In a preferred embodiment, the molar ratio of the reducing agent to Cu in the copper source is (0.2-0.5):1.

[0055] In one embodiment, the amount of reducing solution and catalyst preform added for impregnation as described in this disclosure can be flexibly set according to actual production needs, as long as the catalyst preform is completely submerged in the reducing solution.

[0056] In this embodiment, the use of a suitable reducing agent and a suitable amount of reducing agent can further enhance the impregnation effect, making the copper element in the reducing agent more evenly distributed in the catalyst preform structure, improving the copper dispersion of the methanol synthesis catalyst, and thus further improving the activity and selectivity of the copper-based catalyst.

[0057] In one embodiment, in order to further improve the leaching effect, before performing step S2, the catalyst preform is first ground into powder, and the particle size of the powder is 60-100 mesh.

[0058] In one embodiment, the impregnation further includes mixing and stirring the reducing solution with the powder obtained after grinding, and stirring periodically.

[0059] In one embodiment, the impregnation conditions include: a temperature of 10-45°C, preferably 25-40°C; and a time of 8-24 hours, preferably 10-20 hours.

[0060] In one embodiment, the impregnated powder is dried, and the drying conditions include a temperature of 90-120°C and a time of 6-18 hours.

[0061] In one embodiment, the inert atmosphere for calcination in step S2 includes at least one of nitrogen, argon, and helium.

[0062] In a preferred embodiment, the calcination conditions include a temperature of 300-400°C and a time of 330-350 hours.

[0063] In one embodiment, the passivation conditions include: under an inert atmosphere, a temperature of 10-45°C, preferably 25-40°C, and a time of 2-18 hours, preferably 4-12 hours.

[0064] In one embodiment, the inert atmosphere in the passivation conditions includes at least one of nitrogen, argon, and helium, preferably nitrogen, and the oxygen content in the nitrogen is less than 1% by volume.

[0065] In a preferred embodiment, the inert atmosphere used for roasting and passivation in step S2 can be the same or different.

[0066] In one embodiment, the passivated catalyst is sequentially compressed, crushed, and sieved to obtain methanol synthesis catalyst particles with a particle size of 60-100 mesh. In this embodiment, the compression, crushing, and sieving are all conventional choices in the art, and this application does not make any special requirements.

[0067] In one embodiment, the method for preparing a methanol synthesis catalyst includes: S11. The aluminum source is prepared into a 1-3 mol / L aluminum salt solution, the copper source and the zinc source are prepared into a 1-3 mol / L copper-zinc mixed salt solution, the first precipitant is prepared into a 1-3 mol / L first precipitant solution, and the second precipitant is prepared into a 1-3 mol / L second precipitant solution. S12. Add the aluminum salt solution and the first precipitant solution dropwise into a water bath flask and stir. The water bath temperature is 40-90℃. During the entire stirring process, control the dropping rate of the first precipitant solution so that the pH of the first suspension is 5-10. S13. Under the condition of a temperature of 30-90℃, a copper-zinc mixed salt solution and a second precipitant solution are added dropwise at a uniform rate to the first suspension obtained in step S12. During the entire dropwise addition process, the mixture is continuously stirred and the dropwise rate of the second precipitant solution is controlled so that the pH of the second suspension is 6-9. The molar ratio of the amounts of copper source, zinc source and aluminum source is (20-65):(20-40):(3-30) in terms of elements. S14. The second suspension is subjected to aging, filtration, washing and drying in sequence to obtain the catalyst preform; the aging conditions include: temperature of 70-90℃ and time of 1-24h; the drying conditions include: temperature of 90-120℃ and time of 6-18h. S2. Grind the catalyst preform into 60-100 mesh powder, mix the reducing solution with the ground powder and stir intermittently for impregnation. The impregnation conditions include: temperature of 10-45℃, time of 8-24h; the content of reducing agent in the reducing solution is 1.96~16.6% by weight; the molar ratio of reducing agent to Cu in the copper source is (0.1-1):1. The impregnated catalyst particles are then sequentially roasted, passivated, pressed, crushed, and sieved to obtain methanol synthesis catalyst particles with a particle size of 60-100 mesh.

[0068] In one embodiment, the active sites in the methanol synthesis catalyst particles were determined using a Bruker D8 X-ray diffractometer at 40 kV / 40 mA using Cu K rays (1.5406 Å).

[0069] In one embodiment, the catalyst evaluation conditions are as follows: the methanol synthesis reaction performance of the catalysts prepared in each embodiment and comparative example is evaluated using a 16-channel micro multi-tube combined reactor manufactured by HTE GmbH, Germany. This device uses a capillary splitting system to uniformly divide one stream of feed gas into 16 streams, distributing them to 16 tubular reactors. The feed gas flow rate is the same in each reaction tube, and the composition exhibits excellent consistency.

[0070] In one embodiment, the methanol synthesis reaction is carried out at a reaction pressure of 4 MPa, a reaction temperature of 230°C, a catalyst loading of 0.8 g, and a space velocity of 8000 h⁻¹. -1 The designed feed gas volume composition is as follows: CO content 13%, CO2 content 1.2%, H2 content 80%, and Ar content 5.8%. The feed gas is provided by Beijing Helium North Branch Gas Industry Co., Ltd. The catalyst particle size is 60-100 mesh, and it is filled with quartz sand of the same particle size mixed with the catalyst; among them, reaction tube No. 6 is filled with quartz sand of the same particle size for online monitoring of the feed gas composition.

[0071] In one embodiment, the initial activity test process of the catalyst is as follows: After the catalyst to be tested is reduced, the introduced feed gas reacts under the action of the catalyst. After reacting at 230°C for 48 hours, the gaseous products (including methanol) are obtained and introduced into a gas chromatograph to analyze the composition of the gaseous products. Before the gaseous products are introduced into the gas chromatograph, the temperature of the gaseous products is stabilized at 120°C by a heating belt. Then, the gaseous products are introduced into the gas chromatograph, and the gaseous product samples at the outlet of each reaction tube are sampled and analyzed for their composition by the GC analysis system. The activity test process after heat treatment of the catalyst is as follows: After the catalyst to be tested is reduced, the feed gas is introduced and reacted under the action of the catalyst. After reacting at 230℃ for 48 hours, the temperature is raised to 320℃ and the catalyst is heat-treated at this temperature for 24 hours. Then the temperature is lowered to 230℃ and the feed gas is reacted at this temperature in the presence of the heat-treated catalyst for 24 hours. The gaseous products obtained from the reaction are introduced into a gas chromatograph. The gaseous product samples at the outlet of each reaction tube are sampled in turn by the GC analysis system and their composition is analyzed, that is, the activity of the heat-treated catalyst is evaluated.

[0072] The present disclosure is further illustrated by the following examples, but the disclosure is not limited thereto. Unless otherwise stated, the chemicals used in the following examples and comparative examples have a purity of 99% by weight or higher.

[0073] Example 1 Methods for preparing methanol synthesis catalyst S1 include: S11, will Prepare a 1 mol / L aluminum salt solution, the and Prepare a 1 mol / L copper-zinc mixed salt solution, and prepare a 1 mol / L first precipitant solution and a second precipitant solution using Na2CO3; S12. Add the aluminum salt solution and the first precipitant solution dropwise into a water bath flask and stir. The water bath temperature is 70°C. During the entire stirring process, control the dropping rate of the first precipitant solution to keep the pH of the first suspension at 8. S13. Under the condition of 70°C, copper-zinc mixed salt solution and second precipitant solution are added dropwise at a uniform rate to the first suspension obtained in step S12. During the entire dropwise addition process, the mixture is continuously stirred and the dropwise rate of the second precipitant solution is controlled so that the pH of the second suspension is 7.5. S14. The second suspension is subjected to aging, filtration, washing and drying in sequence to obtain the catalyst preform; the aging conditions include: temperature of 80°C and time of 2 hours; washing until the conductivity of the filtrate is less than 100 μs / cm; the drying conditions include: temperature of 110°C and time of 12 hours. S2. Grind the catalyst preform into 100-mesh powder, mix and stir the powder with a 1.96% by weight copper formate solution, and stir intermittently for impregnation. The copper formate solution is prepared by mixing copper formate monohydrate and water. The impregnation conditions include: a temperature of 40°C and a time of 8 hours. The molar ratio of Cu in the copper source, Zn in the zinc source, Al in the aluminum source, and Cu in the copper formate solution is 4:3:1:2. The impregnated catalyst preform is sequentially calcined, passivated, pressed, crushed, and sieved to obtain methanol synthesis catalyst particles S1 with a particle size of 60-100 mesh. The calcination conditions include: under nitrogen atmosphere, at a temperature of 350°C for 4 hours. The passivation conditions include: under a 1% O2-N2 atmosphere, at a temperature of 40°C for 4 hours.

[0074] Example 2 Methods for preparing methanol synthesis catalyst S2 include: S11, will Prepare a 1 mol / L aluminum salt solution, the and Prepare a 1 mol / L copper-zinc mixed salt solution, and prepare a 1 mol / L first precipitant solution and a second precipitant solution using Na2CO3; S12. Add the aluminum salt solution and the first precipitant solution dropwise into a water bath flask and stir. The water bath temperature is 80°C. During the entire stirring process, control the dropping rate of the first precipitant solution so that the pH of the first suspension is 9. S13. Under the condition of 75°C, copper-zinc mixed salt solution and second precipitant solution are added dropwise at a uniform rate to the first suspension obtained in step S12. During the entire dropwise addition process, the mixture is continuously stirred and the dropwise rate of the second precipitant solution is controlled so that the pH of the second suspension is 7. S14. The second suspension is subjected to aging, filtration, washing and drying in sequence to obtain the catalyst preform; the aging conditions include: temperature of 90°C and time of 1 hour; washing until the conductivity of the filtrate is less than 100 μS / cm; the drying conditions include: temperature of 110°C and time of 12 hours. S2. Grind the catalyst preform into 60-mesh powder, mix and stir the powder obtained after grinding with a copper formate solution containing 16.6% by weight, and stir intermittently for impregnation. The impregnation conditions include: temperature of 25°C and time of 12 hours. The molar ratio of Cu in the copper source, Zn in the zinc source, Al in the aluminum source and Cu in the copper formate solution is 2:1.75:1:1.5. The impregnated catalyst particles were sequentially calcined, passivated, pressed, crushed, and sieved to obtain methanol synthesis catalyst particles S2 with a particle size of 60-100 mesh. The calcination conditions included: 350°C for 4 hours under an inert atmosphere; and 40°C for 4 hours under a 1% O2-N2 atmosphere.

[0075] Example 3 The method for preparing methanol synthesis catalyst S3 is the same as in Example 1, except that an equal weight of copper acetate solution with a content of 1.96% by weight is used instead of copper formate solution.

[0076] Example 4 The method for preparing methanol synthesis catalyst S4 is the same as in Example 1, except that the molar ratio of the reducing agent to Cu in the copper source is 0.75:1.

[0077] Example 5 The method for preparing methanol synthesis catalyst S5 is the same as in Example 1, except that the impregnation conditions include a temperature of 60°C and a time of 8 hours.

[0078] Example 6 The method for preparing methanol synthesis catalyst S6 is the same as in Example 1, except that the passivation conditions include a temperature of 60°C and a time of 4 hours.

[0079] Example 7 The method for preparing methanol synthesis catalyst S7 is the same as in Example 1, except that the molar ratio of the copper source, zinc source and aluminum source is 65:20:15 (based on elemental composition).

[0080] Comparative Example 1 The method for preparing methanol synthesis catalyst D1 is the same as in Example 1, except that an equal weight and equal concentration of formic acid solution is used instead of copper formate solution.

[0081] Comparative Example 2 The method for preparing methanol synthesis catalyst D2 is the same as in Example 1, except that the calcination conditions include: under an inert atmosphere, the temperature is 250°C and the time is 5 hours.

[0082] Test case The methanol synthesis catalyst particles S1-S7 and D1-D2 were measured: Determination of the content of each component in the methanol synthesis catalyst particles: The actual elemental composition of the catalyst was analyzed using a Rigaku ZSX Primus IIX-Ray fluorescence spectrometer (XRF), and the content of each component was calculated. The content of each component is shown in Table 1.

[0083] Cu grain size determination: X-ray diffraction (XRD) analysis and Cu grain size determination of the catalyst sample were performed using a Bruker D8 X-ray diffraction system. The tube voltage / current was 40 kV / 40 mA, and Cu K-rays (0.15406 Å) were used at a scan rate of 2... o / min. The measurement results are shown in Table 1.

[0084] The evaluation conditions for the catalyst included: after reduction of the catalyst to be tested, the introduced feed gas reacted under the action of the catalyst. After reacting at 230℃ for 48 hours, the gaseous products (including methanol) were obtained and analyzed in a gas chromatograph. Before the gaseous products were introduced into the gas chromatograph, they were heated to stabilize the temperature at 120℃ using a heating belt. The gaseous products were then introduced into the gas chromatograph, and samples were taken from the outlet of each reaction tube in turn using the GC analysis system for analysis of their composition. The activity test process of the catalyst after heat treatment was as follows: After the catalyst to be tested was reduced, the feed gas was introduced and reacted under the action of the catalyst. After reacting at 230℃ for 48 hours, the temperature was raised to 320℃ and the catalyst was heat-treated at this temperature for 24 hours. Then the temperature was lowered to 230℃ and the feed gas was reacted at this temperature in the presence of the heat-treated catalyst for 24 hours. The gaseous products obtained from the reaction were introduced into a gas chromatograph. The gaseous product samples at the outlet of each reaction tube were sampled in turn by the GC analysis system and their composition was analyzed, that is, the activity of the heat-treated catalyst was evaluated. The test results are shown in Table 2.

[0085] Table 1. Content of each component in methanol synthesis catalyst particles

[0086] Table 2 Evaluation results of methanol synthesis catalyst particles

[0087] As shown in Table 2, a comparison of the data from Examples 1-7 and Comparative Examples 1-2 reveals that the methanol synthesis catalyst prepared using the method of this disclosure, with copper elements uniformly distributed in the precursor structure of the reducing agent, can improve the copper dispersion of the methanol synthesis catalyst, thereby enhancing the initial activity, post-heat-treated activity, activity retention rate, and methanol selectivity of the copper-based catalyst. A comparison of the data from Examples 1 and 3 shows that when the reducing solution is a copper formate solution, the initial activity, post-heat-treated activity, activity retention rate, and methanol selectivity of the copper-based catalyst can be improved. A comparison of the data from Examples 1 and 4 shows that when the molar ratio of the reducing agent to Cu in the copper source is (0.2-0.5):1, the initial activity, post-heat-treated activity, activity retention rate, and methanol selectivity of the copper-based catalyst can be improved. A comparison of the data from Examples 1 and 5 shows that when the impregnation temperature is 10-45°C, the initial activity, post-heat-treated activity, activity retention rate, and methanol selectivity of the copper-based catalyst can be improved. A comparison of the data from Examples 1 and 6 shows that when the passivation temperature is 10-45℃, the initial activity, activity after heat treatment, activity retention rate, and methanol selectivity of the copper-based catalyst can be improved. A comparison of the data from Examples 1 and 7 shows that when the molar ratio of copper, zinc, and aluminum sources (based on elemental composition) is (20-60):(20-40):(3-30), the initial activity, activity after heat treatment, activity retention rate, and methanol selectivity of the copper-based catalyst can be improved.

[0088] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0089] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0090] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A methanol synthesis catalyst characterized in that, The methanol synthesis catalyst comprises aluminum oxide, zinc oxide, copper oxide, and elemental copper; Based on the total weight of the methanol synthesis catalyst, the content of alumina is 1.93-21.62% by weight, the content of zinc oxide is 21.57-44.13% by weight, the content of copper oxide is 37.74-67.46% by weight, and the content of elemental copper is 0.84-4.31% by weight. At least a portion of the copper element exists in the form of copper grains, the average grain size of which is 4-8 nm.

2. The methanol synthesis catalyst according to claim 1, characterized in that Based on the total weight of the methanol synthesis catalyst, the content of alumina is 5.30-13.84% by weight, the content of zinc oxide is 21.66-38.05% by weight, the content of copper oxide is 43.19-65.63% by weight, and the content of elemental copper is 2.47-4.32% by weight.

3. The methanol synthesis catalyst of claim 1, wherein The molar ratio of copper oxide to copper in the copper element is (5-30):

1.

4. A process for producing the methanol synthesis catalyst according to any one of claims 1 to 3, characterized in that The method includes: S1. Aluminum source, copper source, zinc source and precipitant are subjected to co-precipitation reaction to obtain catalyst preform; S2. The catalyst preform is impregnated with a reducing solution, and then calcined and passivated in sequence. The reducing agent in the reducing solution includes copper formate and / or copper acetate; The calcination conditions include: under an inert atmosphere, a temperature of 300-400℃, and a time of 2-18h.

5. The method of claim 4, wherein, The aluminum source includes one or more of Al(NO3)3, Al2(SO4)3 and AlCl3; The copper source includes one or more of Cu(NO3)2, CuSO4 and CuCl2; The zinc source includes one or more of Zn(NO3)2, ZnSO4 and ZnCl2; The precipitant includes a first precipitant and a second precipitant; the first precipitant and the second precipitant are each independently selected from carbonates and / or bicarbonates; The reducing solution is a copper formate solution.

6. The method of claim 4, wherein, The impregnation includes: dissolving the reducing agent in water to obtain the reducing solution; The reducing agent is copper formate monohydrate and / or copper formate tetrahydrate; The reducing agent content in the reducing solution is 1.96-16.6% by weight.

7. The method of claim 4, wherein, The impregnation conditions include: a temperature of 10-45℃, a time of 8-24h, and a molar ratio of the reducing agent to Cu in the copper source of (0.1-1):

1.

8. The method of claim 4, wherein, The passivation conditions include: under an inert atmosphere, at a temperature of 10-45°C, for a time of 2-18 hours; The inert atmosphere includes one or more of nitrogen, argon, and helium; The oxygen content in the inert atmosphere is less than 1% by volume.

9. The method according to claim 4, characterized in that, The molar ratio of the amounts of copper source, zinc source and aluminum source, in terms of elements, is (20-60):(20-40):(3-30).

10. The method according to claim 5, characterized in that, Step S1 also includes: S11. The aluminum source is configured into an aluminum salt solution, the copper source and the zinc source are configured into a copper-zinc mixed salt solution, the first precipitant is configured into a first precipitant solution, and the second precipitant is configured into a second precipitant solution; S12. React the aluminum salt solution and the first precipitant solution at 40-90°C to obtain a first suspension with a pH of 5-10. S13. The copper-zinc mixed salt solution and the second precipitant solution are introduced into the first suspension and co-precipitated at a temperature of 30-90°C to obtain a second suspension with a pH of 6-9. S14. The second suspension is subjected to aging, filtration, washing and drying in sequence to obtain the catalyst preform.

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