A preparation method of a methanol synthesis catalyst

Abstract

The present invention discloses a preparation method of a methanol synthesis catalyst. The preparation method includes: (1) carrying out a co-current gelling reaction on a Zn- and Cu-containing solution and a sodium metaaluminate solution to obtain a slurry; (2) continuously carrying out n times of three-stage decreasing pH aging on the slurry obtained in step (1), adding 1 / n of an Al-containing solution each time at the end of the first-stage pH aging, subjecting the material obtained after aging to solid-liquid separation, and subjecting the solid phase to drying and tabletting processes to obtain a formed product; (3) carrying out desalting treatment, washing, drying and calcination on the formed product to obtain a methanol synthesis catalyst. The catalyst prepared by the method of the present invention has a larger pore volume and pore diameter, the pore distribution is mainly concentrated in macropores, the active metal copper and the promoter zinc have good dispersion performance and a good synergistic effect, and the activity, selectivity and thermal stability of the methanol synthesis catalyst and the service life of the catalyst are improved.

Description

Technical Field

[0001] The present invention relates to a preparation method of a methanol synthesis catalyst, and particularly to a preparation method of a methanol synthesis catalyst with high activity, high selectivity and good heat resistance. Background Art

[0002] The status of methanol in the national economy has become increasingly important. As a basic chemical raw material and new energy source, methanol has received more and more attention. It is widely used in organic synthesis, dyes, fuels, pharmaceuticals, coatings and the national defense industry. Therefore, in order to further promote the development of the methanol industry, its production technology and catalyst performance need to be further improved.

[0003] At present, medium and low pressure gas phase methods are generally used in the world to synthesize methanol, and the catalysts used are basically mixed oxides of copper, zinc and aluminum. The functions of the three components CuO, ZnO and Al2O3 in the methanol synthesis catalyst are different. CuO is the main active component, and ZnO and Al2O3 are promoters. The addition of ZnO can form a Cu / Zn synergy in the catalyst, greatly improving the activity and selectivity of the catalyst. Al2O3 not only plays a framework role in the catalyst, but also can disperse the active components in the catalyst. The activity of the Cu / ZnO / Al2O3 catalyst is closely related to the distribution and morphology of its surface components, and the distribution and morphology of the surface components are closely connected with the specific surface area and pore distribution of the catalyst. Catalysis theory believes that the reaction of H2 and CO to synthesize methanol proceeds on a series of active centers, and such active centers exist on the reduced Cu-CuO interface. Different catalyst preparation methods result in different degrees of copper dispersion, different synergistic effects between the metal active center copper and the promoter, and the performance of the obtained catalysts will vary greatly. The pore distribution in the catalyst plays a crucial role in the Cu-ZnO synergy and Cu dispersion. How to increase the specific surface area and pore volume of the catalyst, optimize the pore distribution, thereby improving the dispersion of the active components of the catalyst and the Cu-ZnO synergy, so that the catalyst has both excellent activity and good selectivity, has become the research focus of copper-based catalysts.

[0004] When the copper-zinc catalyst is prepared by the co-precipitation method, although relatively low-cost sodium-containing raw materials are used, greatly reducing the catalyst preparation cost, the introduction of a large amount of sodium ions makes it difficult to remove sodium ions in the catalyst. A large amount of water is needed to wash the precipitate to remove alkali metal ions in the precipitate, thus generating a large amount of saline wastewater. As the country's requirements for sewage treatment become more and more stringent, such wastewater faces the problems of large treatment volume and high treatment energy consumption. In addition, when the sodium ion content is high, only the sodium ions on the surface of the catalyst can be removed by washing, and a large amount of sodium ions still remain in the precipitate material. The remaining sodium ions result in poor adhesion of the material, and the sodium ions that have not been removed are not conducive to the formation of the catalyst pore structure, resulting in smaller pore volume and pore diameter of the catalyst and fewer macropores.

[0005] CN101502803A discloses a preparation method of a catalyst for the selective hydrogenation of dimethyl maleate to prepare 1,4-butanediol, and metal additives such as Mn, Mg, and Cr are added on the basis of the two-step method. CN 1660490A discloses a preparation method of a methanol synthesis catalyst, and a small amount of surfactant OP is added during the coprecipitation preparation process. CN101733109A discloses a preparation method of a copper-based methanol synthesis catalyst, and an organic additive (one or several of ethylene glycol, diethylamine, glycerol, magnesium stearate, and activated carbon) is added during the precipitation process. The above methods all add reagents during the precipitation process to improve the dispersion of CuO on the catalyst surface. However, the addition of additives not only does not increase the specific surface area and pore volume, but also does not optimize the pore distribution, and the improvement of the dispersion of the main active component CuO in the catalyst is limited.

[0006] CN103801302A discloses a preparation method of a copper-zinc-containing catalyst. In this method, CO2 gas is introduced into a soluble zinc salt solution A containing zinc to react to form a zinc-containing compound precipitate. CO2 gas is introduced into a sodium aluminate solution to form an aluminum-containing precipitate, and it is aged under stirring. Basic copper carbonate is added during aging, and then it is washed, filtered, dried, calcined, and tableted to obtain a copper-containing catalyst. This method improves the surface area of the catalyst, but there are fewer macropores, and the material obtained by precipitation has poor adhesiveness and is not easy to be tableted.

[0007] CN110935457A discloses a copper-zinc catalyst and its preparation method. The copper-zinc catalyst of this invention is obtained by carrying out a parallel-flow gelling reaction by mixing solution A and a sodium aluminate solution, where solution A is an aqueous solution containing a soluble copper salt, a soluble zinc salt, and an organic additive, to obtain slurry I, aging, and then dropwise adding solution B and a sodium carbonate solution in parallel to the aged slurry I for a gelling reaction to obtain slurry II, and then aging, drying, and forming to obtain the catalyst. The catalyst of this invention has a relatively high Na content, and therefore, has a smaller specific surface area and pore volume. CN107774263A discloses a preparation method of a methanol synthesis catalyst. A sodium aluminate alkaline solution and a soluble Cu-containing salt solution are simultaneously added in parallel into a reaction tank filled with pure water for a gelling reaction to generate slurry I, and then the sodium aluminate alkaline solution is dropwise added into a soluble Zn-containing salt solution for a gelling reaction to generate slurry II. Slurry I and slurry II are mixed evenly, aged, and filtered, and the obtained material is subjected to hydrothermal treatment with steam, where urea is added during the hydrothermal treatment, and then washed, filtered, dried, calcined, and tableted to obtain the catalyst. Although the content of the active metal copper in the surface phase of the catalyst prepared by this method is high, under the action of steam pressure and the impact of water molecules, the dispersion of copper and zinc in the catalyst is reduced.

[0008] The above method changes the dispersion of copper on the reduced catalyst by changing the preparation process of the copper-based catalyst or adding promoters on this basis, thereby improving the activity of the catalyst. However, there is no obvious increase in the specific surface area and pore volume of the catalyst, and the improvement effect on the dispersion of the active components is not obvious. SUMMARY OF THE INVENTION

[0009] Aiming at the deficiencies in the prior art, the present invention provides a preparation method for a methanol synthesis catalyst. The catalyst prepared by the method of the present invention has a larger pore volume and pore diameter, the pore distribution is mainly concentrated in macropores, the active metal copper and the promoter zinc have good dispersion performance and a good synergistic effect, which improves the activity, selectivity and thermal stability of the methanol synthesis catalyst and the service life of the catalyst.

[0010] The preparation method for the methanol synthesis catalyst of the present invention includes the following steps:

[0011] (1) A Zn- and Cu-containing solution and a sodium metaaluminate solution are flowed in parallel to form a gel reaction to obtain a slurry;

[0012] (2) The slurry obtained in step (1) is continuously aged by three-stage decreasing pH value for n times. Each time, 1 / n of the Al-containing solution is added at the end of the first-stage pH value aging. The material obtained after aging is subjected to solid-liquid separation, and the solid phase is subjected to drying and tabletting processes to obtain a formed product;

[0013] The specific process of each three-stage decreasing pH value aging is as follows: the aging temperature is 60-98°C, preferably 65-92°C; in the first stage, the pH value is 11.0-13.5, and the aging time is 0.05-0.5 hours. The 1 / n of the Al-containing solution is added at the end of the first-stage aging; in the second stage, the pH value is adjusted to 8.5-10.5, and the aging time is 0.05-0.5 hours; in the third stage, the pH is adjusted to 5.5-8.3, and the aging time is 0.05-0.5 hours; where n is an integer of 2-8;

[0014] (3) The formed product is subjected to desalting treatment, washing, drying and calcination to obtain a methanol synthesis catalyst.

[0015] In the method of the present invention, in the Zn- and Cu-containing solution in step (1), the concentration of the soluble copper salt is 1.0-6.0 mol / L in terms of Cu 2+ preferably 1.5-6.0 mol / L, and the concentration of the soluble zinc salt is 0.5-6.0 mol / L in terms of Zn 2+ preferably 1.0-4.0 mol / L. The soluble copper salt is a copper-containing nitrate and / or acetate, and the soluble zinc salt is a zinc-containing nitrate and / or acetate.

[0016] In the method of the present invention, the concentration of the sodium aluminate solution in step (1) is 10-90 g / L in terms of Al2O3, preferably 15-85 g / L.

[0017] In the method of the present invention, the gel-forming reaction conditions in step (1) are as follows: the reaction temperature is 30-90 °C, preferably 40-85 °C; the initial pH value is controlled at 10.0-14.0, preferably 10.5-13.5; the final pH value at the end is 7.0-8.5, preferably 7.2-8.3; and the gel-forming reaction time is 0.5-6.0 hours, preferably 0.6-5.0 hours.

[0018] Preferably, the pH value can be decreased in steps from the initial value to the final pH value. The method of decreasing in steps is to decrease the pH value to the required value for that time and keep the pH value of this reaction slurry constant until the start of the next decrease. The number of decreases is 2-10 times, preferably 2-8 times.

[0019] More preferably, it is constant for 0.1-1.2 hours after each decrease. The amplitude of each decrease can be the same or different. Preferably, the decrease amplitude of pH each time is equal to or less than the decrease amplitude of pH in the previous decrease. The time used for each decrease process is from the start of this decrease to the start of the next decrease. Further, it is the sum of the time used for each pH value decrease and the time of constant at this pH value. The time used for each decrease process can be the same or different, preferably the same.

[0020] In the method of the present invention, in step (2), the acids and bases used to adjust the pH value can be inorganic salts, inorganic acids and inorganic bases without aluminum element. Further, they can be one or more of hydrochloric acid, acetic acid, sodium carbonate, and sodium bicarbonate. The concentration and dosage of the acid and base solutions can be adjusted according to the actual preparation needs.

[0021] In the method of the present invention, in step (2), the added Al accounts for 5%-45% of the total Al in the obtained synthetic methanol catalyst in terms of Al2O3, preferably 6%-40%. When preparing the Al-containing solution, generally the aluminum source is a soluble aluminum salt, which can be one or more of aluminum nitrate, aluminum sulfate, aluminum chloride, etc., and is equally divided into n parts by volume, where n is an integer from 2 to 8.

[0022] In the method of the present invention, in step (2), the solid-liquid separation generally adopts methods such as filtration and centrifugation.

[0023] In the method of the present invention, in step (2), the drying temperature is 50-140 °C and the drying time is 0.5-24 hours.

[0024] In the method of the present invention, during the shaping process described in step (2), conventional shaping extrusion aids can be added as needed. The extrusion aids refer to substances that are beneficial to extrusion shaping, such as one or more of carbon black, graphite powder, etc. The dosage of the extrusion aid accounts for 1wt% - 10wt% of the total dry basis of the materials.

[0025] In the method of the present invention, the desalination treatment process described in step (3): First, conduct curing, and then wash to remove the salt precipitated on the surface of the shaped product. The curing conditions are a temperature of 5 - 100°C, preferably 10 - 90°C, and a time of 10 - 100 hours, preferably 24 - 90 hours.

[0026] In the method of the present invention, the desalination treatment described in step (4) is preferably carried out as follows: In the first stage, the temperature is 60 - 90°C for curing for 5 - 60 hours, preferably 8 - 55 hours, to precipitate hydrated sodium ions and retain vacancies; in the second stage, the temperature is 10 - 30°C for 1 - 48 hours, preferably 2 - 42 hours, to promote the retention and contraction of vacancies, increase the pore volume of the catalyst and have good mechanical strength, and then wash to remove the precipitated salts. The washing process can use solvents such as water and ethanol that have good solubility for sodium salts.

[0027] In the method of the present invention, the washing, drying, and calcination described in step (4) can be carried out under conventional conditions in the art. The washing is carried out with deionized water until neutral. The drying conditions: drying at 50 - 150°C, preferably 60 - 120°C, and the drying time is 0.5 - 24.0 hours, preferably 1 - 16 hours. The calcination conditions are as follows: calcining at 300 - 360°C for 1 - 16 hours, preferably 2 - 10 hours.

[0028] The synthetic methanol catalyst prepared by the method of the present invention, based on the weight of the catalyst, includes the following components: CuO is 25% - 70%, preferably 30% - 60%, ZnO is 12% - 38%, preferably 15% - 35%, and Al2O3 is 10% - 40%, preferably 15% - 38%.

[0029] The properties of the described synthetic methanol catalyst are as follows: The specific surface area is 120 - 550m 2 / g, the pore volume is 0.30 - 0.90ml / g, and the pore size distribution is as follows: The pore volume of pores below 10nm accounts for 3% - 20% of the total pore volume, the pore volume of pores of 10 - 15nm accounts for 15% - 48% of the total pore volume, and the pore volume of pores above 15nm accounts for 45% - 75% of the total pore volume. The preferred pore size distribution is as follows: The pore volume of pores below 10nm accounts for 5% - 18% of the total pore volume, the pore volume of pores of 10 - 15nm accounts for 20% - 45% of the total pore volume, and the pore volume of pores above 15nm accounts for 48% - 70% of the total pore volume.

[0030] The specific surface area of metallic copper in the reduced catalyst is 45 to 140 m 2 / g, preferably 50 to 130 m 2 / g. The dispersion of metallic copper is 20% to 50%, preferably 25% to 45%.

[0031] The content of Na2O in the synthesized methanol catalyst prepared by the method of the present invention is less than 0.12%, preferably less than 0.10%.

[0032] The synthesized methanol catalyst prepared by the method of the present invention is applied to the synthesis of methanol reaction. The general process conditions are as follows: reaction temperature 210 to 320 °C, preferably 230 to 290 °C; pressure 2.0 to 10 MPa, preferably 2.0 to 8.0 MPa; volume space velocity 2000 to 15000 h -1 , preferably 4000 to 12000 h -1 .

[0033] Compared with the prior art, the active metal of the catalyst prepared by the method of the present invention is more dispersed, and there is a good synergistic effect between Cu-ZnO. The pore distribution of the catalyst is concentrated (mainly concentrated above 15 nm), and it has the characteristics of high activity, high selectivity and heat resistance.

[0034] 1. The catalyst preparation method of the present invention is simple, convenient and has low investment, effectively reducing the amount of salt-containing wastewater generated in the catalyst preparation process. The inventor first retains the sodium salt in the material during the forming process, and then performs desalting treatment on the formed material to remove the precipitated sodium salt. In this process, due to the occupation effect of the sodium salt during the forming process, the vacancy after sodium removal is more conducive to the formation of the pore structure of the catalyst, the pore distribution moves towards the macropore direction, the pore volume and pore diameter of the catalyst increase, improving the diffusion performance of the catalyst, and solving the problems of poor dispersion of the active metal of the synthesized methanol catalyst in the prior art, fewer macropores in the catalyst and difficulty in forming.

[0035] 2. In the method of the present invention, when the composite oxides of copper, zinc and aluminum are formed, the method of decreasing the pH value to form a gel is adopted, which can reduce the grain size of CuO, increase the specific surface area of metallic copper, and produce a good synergistic effect between Cu-ZnO.

[0036] 3. In the method for preparing the synthesized methanol catalyst of the present invention, a solution containing Al is added in portions during the pH swing process during aging, further improving the support effect of the Al2O3 skeleton, making the pores unobstructed, facilitating the smooth passage of macromolecular reactants, promoting the dispersion of the active metal, and strengthening the promotion effect between the active metals, which is beneficial to the improvement of the catalyst activity, methanol selectivity and thermal stability. At the same time, the content of sodium ions on the surface of the phase is increased, which is more conducive to desalting treatment. Specific embodiments

[0037] The solutions and effects of the present invention are further illustrated by the following examples. In the present invention, the specific surface area, pore volume and pore distribution are measured by the low-temperature liquid nitrogen adsorption method. After reduction, the specific surface area (S Cu ) and dispersion degree (D Cu ) of the catalyst metal Cu are measured by the N2O chemical reaction adsorption method. v% is the volume fraction, and wt% is the mass fraction.

[0038] Example 1

[0039] Cu(NO3)2·3H2O and Zn(NO3)2·6H2O are dissolved in deionized water to prepare a mixed solution A. The concentration of Cu 2+ is 3.8 mol / L, and the concentration of Zn 2+ is 3.2 mol / L. AlCl3·6H2O is dissolved in deionized water to prepare an aluminum chloride solution. The Al in the aluminum chloride solution accounts for 26.2% of the total Al in the obtained methanol synthesis catalyst in terms of Al2O3, and it is equally divided into 4 parts by volume. Deionized water is added into the reaction tank, and the sodium aluminate solution and the mixed solution A are added into the reaction tank in a co-current manner. The gelling temperature is 60 °C, and the initial pH value is controlled at 13.1. By lowering the pH value 7 times, the final pH value at the end is adjusted to 7.5, and the pH value lowered each time is 0.8. After each lowering to the adjusted value, the pH value of the reaction slurry is controlled to be constant for 8 minutes. After the reaction ends, a slurry containing copper, zinc and aluminum is obtained. The obtained slurry is aged at an aging temperature of 76 °C. The pH value during aging is first controlled at 13.0. After the aging time of 0.3 hours, 1 equal part of the aluminum chloride solution is added, and then the aging pH value is controlled at 9.5. After the aging time of 0.2 hours, the pH value is then controlled at 7.6, and the aging time is 0.2 hours. The above operation process is repeated 4 times to end the aging. The aged slurry is filtered, and the filter cake is dried at 90 °C for 10 hours, and an appropriate amount of graphite and water are added for rolling and tablet molding. After the molded material is cured at a temperature of 70 °C for 50 hours, the temperature is lowered to 20 °C and curing continues for 30 hours. The molded material is washed with deionized water until it is neutral. After washing, the molded product is dried at 100 °C for 8 hours and calcined at 360 °C for 3 hours to obtain catalyst A. The composition, pore distribution and main properties are shown in Table 1.

[0040] Example 2

[0041] According to the method of Example 1, in accordance with the component content ratio of Catalyst B in Table 1, dissolve Cu(NO3)2·3H2O and Zn(NO3)2·6H2O in deionized water to prepare a mixed solution A, and dissolve aluminum sulfate in deionized water to prepare an aluminum sulfate solution. The Al in the aluminum sulfate solution accounts for 29.2% of the total Al in the resulting methanol synthesis catalyst calculated as Al2O3, and divide it into 5 equal parts by volume. Add deionized water into the reaction tank, and add the sodium metaaluminate solution and the mixed solution A into the reaction tank in a co-current manner. The gelation temperature is 55 °C, and the initial pH value is controlled at 12.0. By adjusting the pH value 6 times, the final pH value at the end is adjusted to 7.8, and the pH value adjusted each time is 0.7. After each adjustment to the adjusted value, keep the pH value of the adjusted reaction slurry constant for 12 minutes to obtain a slurry containing copper, zinc, and aluminum. Age the obtained slurry. The aging temperature is 80 °C. First, control the pH value during aging at 12.8. After 0.2 hours of aging time, add 1 equal part of the aluminum sulfate solution, then control the aging pH value at 9.3. After 0.3 hours of aging time, then control the pH value at 6.8, and the aging time is 0.3 hours. Repeat the above operation process 5 times to end the aging. Filter the aged slurry, dry the filter cake at 90 °C for 10 hours, add appropriate amount of graphite and water for rolling, and press into tablets. After the formed product is cured at a temperature of 85 °C for 45 hours, the temperature is reduced to 25 °C and continue to cure for 28 hours. Wash the formed product with deionized water until it is neutral. After washing, dry the formed product at 80 °C for 12 hours and calcine it at 350 °C for 4 hours to obtain Catalyst B. The composition, pore distribution and main properties are shown in Table 1.

[0042] Example 3

[0043] According to the method of Example 1, with the component content ratio of Catalyst C in Table 1, dissolve Cu(NO3)2·3H2O and Zn(NO3)2·6H2O in deionized water to prepare a mixed solution A. Dissolve AlCl3·6H2O in deionized water to prepare an aluminum chloride solution. The Al in the aluminum chloride solution accounts for 21.8% of the total Al in the resulting methanol synthesis catalyst calculated as Al2O3, and divide it into 4 equal parts by volume. Add deionized water into the reaction tank, and add the sodium aluminate solution and the mixed solution A into the reaction tank in a co-current manner. The gelation temperature is 50 °C, and the initial pH value is controlled at 12.8. By adjusting the pH value 5 times, the final pH value at the end is adjusted to 7.8, and the pH value adjusted each time is 1.0. After each adjustment to the adjusted value, keep the pH value of the adjusted reaction slurry constant for 10 minutes to obtain a slurry containing copper, zinc, and aluminum. Age the obtained slurry. The aging temperature is 83 °C. First, control the pH value during aging at 12.5. After 0.2 hours of aging time, add 1 equal part of the aluminum chloride solution, then control the aging pH value at 9.8. After 0.1 hours of aging time, then control the pH value at 7.0, and the aging time is 0.2 hours. Repeat the above operation process 4 times to end the aging. Filter the aged slurry, dry the filter cake at 90 °C for 8 hours, add appropriate amount of graphite and water for rolling, press into tablets. Keep the formed product at 20 °C for 70 hours for curing, wash the formed product with deionized water until it is neutral, dry the filter cake at 100 °C for 10 hours, and calcine at 340 °C for 4 hours to obtain Catalyst C. The composition, pore distribution, and main properties are shown in Table 1.

[0044] Example 4

[0045] According to the method of Example 1, according to the component content ratio of Catalyst D in Table 1, dissolve Cu(NO3)2·3H2O and Zn(NO3)2·6H2O in deionized water to prepare a mixed solution A. Dissolve AlCl3·6H2O in deionized water to prepare an aluminum chloride solution. The Al in the aluminum chloride solution accounts for 32% of the total Al in the obtained methanol synthesis catalyst calculated as Al2O3, and divide it into 6 equal parts by volume. Add deionized water to the reaction tank, and add the sodium aluminate solution and the mixed solution A into the reaction tank in parallel. The gelling temperature is 65°C, the initial pH value is controlled at 12.2, and by adjusting the pH value 4 times, the final pH value at the end is adjusted to 7.4. The pH value adjusted each time is 1.2. After each adjustment to the adjusted value, keep the pH value of the reaction slurry constant for 10 minutes to obtain a slurry containing copper, zinc, and aluminum. Age the obtained slurry. The aging temperature is 78°C. First, control the pH value during aging at 13.3. After 0.15 hours of aging time, add 1 equal part of the aluminum chloride solution, and then control the aging pH value at 9.0. After 0.1 hours of aging time, then control the pH value at 7.2, and the aging time is 0.2 hours. Repeat the above operation process 6 times to end the aging. Filter the aged slurry, dry the filter cake at 90°C for 8 hours, add appropriate amount of graphite and water for rolling, and press into tablets. Let the formed product cure at 35°C for 80 hours, wash it with deionized water until neutral, dry the formed product at 80°C for 14 hours, and calcine it at 350°C for 4 hours to obtain Catalyst D. The composition, pore distribution, and main properties are shown in Table 1.

[0046] Comparative Example 1

[0047] According to the component content ratio of Catalyst A in Table 1, dissolve Cu(NO3)2·3H2O and Zn(NO3)2·6H2O in deionized water to prepare a mixed solution. Add deionized water to the reaction tank, and add the sodium aluminate solution and the mixed solution into the reaction tank in parallel. The gelling temperature is 60°C, the gelling time is 1 hour, and the reaction pH value is 7.5 to obtain a reaction slurry. Age the slurry under stirring conditions. The aging pH value is 7.6, the aging temperature is 76°C, and the aging time is 2.8 hours. Filter the aged slurry, dry the filter cake at 90°C for 10 hours, add appropriate amount of graphite and water for rolling, and press into tablets. Wash the formed material with deionized water until neutral. After washing, dry the formed product at 100°C for 8 hours, and calcine it at 360°C for 3 hours to obtain Catalyst E. The composition, pore distribution, and main properties are shown in Table 1.

[0048] Comparative Example 2

[0049] According to the method disclosed in CN107774263A, prepare a reference agent F with the same catalyst composition as that in Example 1. The specific process is as follows:

[0050] According to the catalyst composition of Example 1, dissolve Cu(NO3)2·3H2O in deionized water to prepare solution A. Dissolve Zn(NO3)2·6H2O in deionized water to prepare mixed solution B. Add deionized water into the reaction tank, and add the sodium aluminate solution and mixed solution A into the reaction tank in a co-current manner. The gelling temperature is 60 °C, the gelling pH value is 7.5, and the gelling time is 1.0 hour to obtain copper- and aluminum-containing precipitate slurry I. Add the sodium aluminate solution to solution B under stirring, keep the gelling temperature at 60 °C, control the pH value at 7.5 at the end, and control the gelling time at 1 hour to generate zinc- and aluminum-containing precipitate slurry II. Mix the above two precipitate-containing slurries. Start aging under stirring, with a pH of 7.6 and a temperature of 76 °C for 2.8 hours during aging. After aging, filter the material, and perform hydrothermal treatment on the filter cake under water vapor containing urea. The hydrothermal treatment conditions are as follows: the molar ratio of urea to the total amount of active metal atoms is 7:1, the temperature is 230 °C, the pressure is 6.0 MPa, and the treatment time is 4 hours. Dry the filter cake at 90 °C for 10 hours, add an appropriate amount of graphite and water for rolling, and press into tablets. Wash the formed material with deionized water until it is neutral. After washing, dry the formed product at 100 °C for 8 hours and calcine it at 360 °C for 3 hours to obtain catalyst F. The composition, pore distribution, and main properties are shown in Table 1.

[0051] Comparative Example 3

[0052] According to the method of Example 1, prepare catalyst G according to the component content ratio of catalyst A in Table 1, and the formed tablets are not subjected to desalting treatment.

[0053] Dissolve Cu(NO3)2·3H2O and Zn(NO3)2·6H2O in deionized water to prepare mixed solution ACu 2+ with a concentration of 3.8 mol / L, Zn 2+The concentration is 3.2 mol / L. AlCl3·6H2O is dissolved in deionized water to prepare an aluminum chloride solution. The Al in the aluminum chloride solution accounts for 26.2% of the total Al in the obtained methanol synthesis catalyst calculated as Al2O3, and it is divided into 4 equal parts by volume. Deionized water is added into the reaction tank, and the sodium aluminate solution and the mixed solution A are added into the reaction tank in a co-current manner. The gelling temperature is 60 °C, the initial pH value is controlled at 13.1, and through 7 times of adjusting the pH value downward, the final pH value at the end is adjusted to 7.5, and the pH value adjusted downward each time is 0.8. After each adjustment to the adjusted value, the pH value of the reaction slurry is controlled to be constant for 8 minutes. After the reaction ends, a slurry containing copper, zinc, and aluminum is obtained. The obtained slurry is aged. The aging temperature is 76 °C. The pH value during aging is first controlled at 13.0. After 0.3 hours of aging time, after adding 1 equal part of the aluminum chloride solution, the aging pH value is controlled at 9.5. After 0.2 hours of aging time, then the pH value is controlled at 7.6, and the aging time is 0.2 hours. The above operation process is repeated 4 times to end the aging. The aged slurry is filtered, the filter cake is dried at 90 °C for 10 hours, appropriate amount of graphite and water are added for rolling, tableted, the formed material is washed with deionized water until neutral, and the formed product obtained after washing is dried at 100 °C for 8 hours and calcined at 360 °C for 3 hours to obtain catalyst G. The composition, pore distribution and main properties are shown in Table 1.

[0054] Comparative Example 4

[0055] According to the gelling reaction conditions of Example 1, the aging conditions are conventional conditions, and a reference agent H with the same catalyst composition as that of Example 1 of the present invention is prepared.

[0056] Cu(NO3)2·3H2O and Zn(NO3)2·6H2O are dissolved in deionized water to prepare a mixed solution. The concentration of Cu 2+ is 3.8 mol / L, and the concentration of Zn 2+The concentration is 3.2 mol / L. Deionized water is added into the reaction tank, and the sodium aluminate solution (containing 58 g / L of Al2O3) and the mixed solution A are fed into the reaction tank in parallel. The gelation temperature is 60 °C, and the initial pH value is controlled at 13.1. By adjusting the pH value 7 times, the final pH value at the end is adjusted to 7.5, and the pH value adjusted each time is 0.8. After each adjustment to the adjusted value, the adjusted pH value of the reaction slurry is controlled constantly for 8 minutes. After the reaction is completed, a slurry containing copper, zinc, and aluminum is obtained. The obtained slurry is aged at an aging temperature of 76 °C and a pH value of 7.8 for 2 hours, and then the aging is ended. The aged slurry is filtered, and the filter cake is dried at 90 °C for 10 hours, and then appropriate amount of graphite and water are added for rolling and tablet forming. After the formed material is cured at a temperature of 70 °C for 50 hours, the temperature is reduced to 20 °C and curing continues for 30 hours. The formed material is washed with deionized water until it is neutral, and the washed formed material is dried at 100 °C for 8 hours and calcined at 360 °C for 3 hours to obtain the catalyst H. The composition, pore distribution and main properties are shown in Table 1.

[0057] Comparative Example 5

[0058] According to the method disclosed in CN110935457A, a reference agent I with the same catalyst composition as that in Example 1 is prepared, and the specific process is as follows:

[0059] Cu(NO3)2·3H2O and Zn(NO3)2·6H2O are dissolved in deionized water, and 116 grams of hydroxyethylidene diphosphonic acid is added and mixed evenly to prepare a mixed solution A. The concentration of Cu 2+ is 2.8 mol / L, and the concentration of Zn 2+ is 2.5 mol / L. Cu(NO3)2·3H2O and AlCl3·6H2O are dissolved in deionized water to prepare a mixed solution B. The concentration of Cu 2+ is 1.8 mol / L, and the concentration of Al 3+The concentration is 2.0 mol / L. Deionized water is added into the reaction tank, and the sodium aluminate solution and the mixed solution A are fed into the reaction tank in parallel. The gelling temperature is 60 °C, the gelling pH value is 7.5, and the gelling time is 0.9 hours to obtain Slurry I. Slurry I is aged under stirring, with a stirring speed of 190 rpm, an aging temperature of 75 °C, a pH value of 7.2, and an aging time of 0.7 hours. After aging, the mixed solution B and the sodium carbonate solution are fed into the aged Slurry I in parallel. The molar ratio of the amount of sodium carbonate to the total amount of copper and zinc is 2.0, the gelling temperature is 62 °C, the pH value is 9.2, and the gelling time is 2.0 hours to obtain Slurry II. Slurry II is aged under stirring conditions, with a stirring speed of 400 rpm, an aging temperature of 75 °C, a pH value of 8.5, and an aging time of 3.0 hours. The aged Slurry II is filtered, and the filter cake is washed 3 times with deionized water. The filter cake is dried at 100 °C for 10 hours and calcined at 360 °C for 3 hours. An appropriate amount of graphite and water are added to the calcined material and pressed into tablets to obtain Catalyst I. The composition, pore distribution, and main properties are shown in Table 1.

[0060] Example 5

[0061] The methanol synthesis catalyst is crushed into 16 - 40 mesh, and before use, it is reduced with a hydrogen-nitrogen mixed gas with a low concentration of hydrogen (H2 / N2 = 3 / 97 (volume ratio)) for 16 - 25 h, and the maximum reduction temperature is 235 °C. The activity evaluation of the catalyst is carried out on a micro fixed-bed reaction device. The catalyst loading is 5 ml, the raw material gas composition is CO / H2 / CO2 / N2 = 13 / 70 / 6 / 11 (volume ratio), the reaction pressure is 5.0 MPa, and the space velocity is 10000 h -1 , the reaction temperature is 245 °C, and the conversions of CO and CO2 are measured as the initial activity of the catalyst. Then the catalyst is heat-treated at 445 °C for 5 h in a synthesis atmosphere and then cooled to 250 °C to measure the conversions of CO and CO2 as the activity after heat treatment, that is, the heat resistance. The products are analyzed by a gas chromatograph, and the space-time yield of methanol production is g·mL -1 ·h -1 That is, the grams of methanol produced per milliliter of catalyst per hour, and the results are shown in Table 3.

[0062] As can be seen from Table 1 and Table 2, the metals in the catalyst of the present invention are well dispersed, thereby improving the synergistic effect between Cu and ZnO in the catalyst. The pore structure distribution shifts towards the direction of large pores, mainly concentrated above 15 nm. Within this pore distribution range, the catalyst has high activity and selectivity. From the test results, the methanol synthesis catalyst of the present invention has high activity, heat resistance, and excellent selectivity.

[0063] Table 1 Catalyst Composition and Properties

[0064]

[0065] Continued Table 1 Catalyst Composition and Properties

[0066]

[0067] Table 2 Dispersion and Specific Surface Area of Metallic Copper

[0068]

[0069] S Cu is the specific surface area of copper, and D Cu is the dispersion of copper

[0070] Table 3 Experimental Results of Catalyst Activity Evaluation and Heat Resistance Performance

[0071]

Claims

1. A method for preparing a catalyst for synthesizing methanol, characterized in that The method comprises the following steps: (1) reacting a solution containing Zn and Cu with a sodium aluminate solution to form a slurry; (2) The slurry obtained in step (1) is continuously subjected to n times of three-stage decreasing pH aging, and 1 / n Al-containing solution is added at the end of the first stage pH aging each time. The material obtained after aging is subjected to solid-liquid separation, and the solid phase is dried and tableted to obtain a molded product; wherein each three-stage decreasing pH aging process is specifically as follows: the aging temperature is 60-98°C, the first stage, the pH value is 11.0-13.5, the aging is 0.05-0.5 hours, and the 1 / n Al-containing solution is added at the end of the first stage aging; the second stage, the pH value is adjusted to 8.5-10.5, and the aging time is 0.05-0.5 hours. ; In the third stage, the pH is adjusted to 5.5-8.3 and the aging is carried out for 0.05-0.5 hours; wherein n is an integer of 2-8; (3) the molded product is subjected to desalination treatment, washing, drying and roasting to obtain a synthetic methanol catalyst; the desalination treatment described in step (3) is carried out as follows: the first stage temperature is 60-90°C, and the curing time is 5-60 hours to precipitate hydrated sodium ions and retain vacancies; the second stage temperature is 10-30°C, and the time is 1-48 hours to promote vacancy retention and shrinkage, so that the pore volume of the catalyst is increased and the catalyst has good mechanical strength, and then the precipitated salt is washed to remove.

2. The method according to claim 1, wherein: In the Zn and Cu solution described in step (1), the concentration of soluble copper salt is Cu 2+ The concentration of soluble zinc salt is 1.0~6.0mol / L, and the concentration of soluble zinc salt is Zn 2+ The soluble copper salt is nitrate and / or acetate containing copper; the soluble zinc salt is nitrate and / or acetate containing zinc.

3. The method according to claim 1, wherein: The concentration of the sodium aluminate solution in step (1) is 10 to 90 g / L in terms of Al2O3.

4. The method according to claim 1, wherein: The gelling reaction conditions of step (1) are as follows: reaction temperature is 30-90°C, pH value is initially controlled to be 10.0-14.0, final pH value is 7.0-8.5 at the end, and gelling reaction time is 0.5-6.0 hours.

5. The method according to claim 4, characterized in that: The pH value is adjusted downward from the initial value to the final pH value in steps. The stepwise adjustment method is to adjust the pH value to the desired value at that time, and keep the pH value of the reaction slurry constant until the next adjustment begins. The number of adjustments is 2 to 10 times.

6. The method according to claim 5, characterized in that: The pH remains constant for 0.1 to 1.2 hours after each downward adjustment; the pH reduction amplitude of each downward adjustment is equal to or less than the pH reduction amplitude of the previous downward adjustment; the time taken for each downward adjustment process is from the start of this downward adjustment to the start of the next downward adjustment.

7. The method according to claim 1, wherein: The acid and alkali used to adjust the pH value are inorganic salts, inorganic acids and inorganic alkalis that do not contain aluminum elements.

8. The method according to claim 1, wherein: In step (2), the added Al accounts for 5% to 45% of the total Al in the obtained methanol synthesis catalyst calculated as Al2O3.

9. The method according to claim 1, wherein: The Al-containing solution is a soluble aluminum salt aqueous solution selected from one or more of aluminum nitrate, aluminum sulfate, and aluminum chloride.

10. The method according to claim 1, wherein: During the molding process described in step (2), an extrusion aid is added as needed. The extrusion aid is a substance that is conducive to extrusion molding. The amount of the extrusion aid accounts for 1wt% to 10wt% of the total material dry basis.

11. A methanol synthesis catalyst prepared according to the method of any one of claims 1 to 10, characterized in that: Based on the weight of the catalyst, the catalyst includes the following components: CuO is 25% to 70%, ZnO is 12% to 38%, and Al2O3 is 10% to 40%.

12. A methanol synthesis catalyst prepared according to the method of any one of claims 1 to 10, characterized in that: The properties of the methanol synthesis catalyst are as follows: the specific surface area is 120 to 550 m 2 / g, the pore volume is 0.30~0.90ml / g, and the pore size distribution is as follows: the pore volume of pores below 10nm accounts for 3%~20% of the total pore volume, the pore volume of pores between 10~15nm accounts for 15%~48% of the total pore volume, and the pore volume of pores above 15nm accounts for 45%~75% of the total pore volume.

13. A methanol synthesis catalyst prepared according to the method of any one of claims 1 to 10, characterized in that: The specific surface area of the metallic copper in the catalyst after reduction is 45 to 140 m 2 / g, the dispersion of metallic copper is 20% to 50%.

14. A methanol synthesis catalyst prepared according to the method of any one of claims 1 to 10, characterized in that: The Na2O content in the methanol synthesis catalyst is less than 0.12%.

15. Use of a methanol synthesis catalyst prepared by the method according to any one of claims 1 to 10 in a methanol synthesis reaction, characterized in that The process conditions are: reaction temperature 210-320°C, pressure 2.0-10 MPa, volume space velocity 2000-15000 h -1 .

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