Preparation method of catalyst for synthesizing methanol

Abstract

The present invention discloses a preparation method of a methanol synthesis catalyst, comprising: (1) reacting a solution containing Zn, Cu, and an auxiliary agent with a sodium metaaluminate solution in parallel to form a gel to obtain a slurry; (2) subjecting the slurry obtained in step (1) to a three-stage decreasing pH value aging process n times continuously, adding 1 / n Al-containing solution at the end of each first-stage pH value aging process, subjecting the obtained material after aging to solid-liquid separation, and subjecting the solid phase to a solid-phase drying and tableting process to obtain a molded product; (3) soaking the molded product in an organic acid solution of a carboxylic acid polymer and / or an organic phosphonic acid compound, and then subjecting the molded product to a desalting treatment, washing, drying, and calcining to obtain a methanol synthesis catalyst. The catalyst prepared by the method of the present invention has a large pore volume and pore size, and the pore distribution is mainly concentrated in the macropores. The active metal copper and the auxiliary zinc have good dispersion performance and a good synergistic effect, thereby improving the activity, selectivity, thermal stability, and service life of the methanol synthesis catalyst.

Description

Technical Field

[0001] The present invention relates to a method for preparing a methanol synthesis catalyst, and in particular to a method for preparing a methanol synthesis catalyst with high activity, high selectivity and good heat resistance. Background Art

[0002] Methanol is becoming increasingly important in the national economy. As a basic chemical raw material and new energy source, it is increasingly valued and widely used in organic synthesis, dyes, fuels, medicines, coatings and defense industries. Therefore, in order to further promote the development of the methanol industry, its production technology and catalyst performance need to be further improved.

[0003] Currently, methanol synthesis is widely achieved worldwide using medium- and low-pressure vapor phase processes, using catalysts primarily composed of mixed oxides of copper, zinc, and aluminum. CuO, ZnO, and Al2O3 play different roles in methanol synthesis catalysts. CuO is the primary active component, while ZnO and Al2O3 serve as additives. The addition of ZnO allows the catalyst to form a Cu / Zn synergistic complex, significantly enhancing its activity and selectivity. Al2O3 not only serves as a scaffold but also disperses the active components within the catalyst. The activity of Cu / ZnO / Al2O3 catalysts is closely related to the distribution and morphology of their surface components, which in turn are closely linked to the catalyst's specific surface area and pore size distribution. Catalytic theory posits that the methanol synthesis reaction from H2 and CO occurs at a series of active centers, typically located at the reduced Cu-CuO interface. Different catalyst preparation methods result in varying copper dispersions and differing synergistic effects between the metallic active copper centers and the additives, leading to significant variations in catalyst performance. The pore size distribution within the catalyst plays a crucial role in the Cu-ZnO synergistic effect and Cu dispersion. How to increase the specific surface area and pore volume of the catalyst, optimize the pore distribution, and thus improve the dispersion of the active components of the catalyst and the Cu-ZnO synergistic effect, so that the catalyst has both excellent activity and good selectivity has become the research focus of copper-based catalysts.

[0004] When copper-zinc catalysts are prepared by the co-precipitation method, although relatively low-priced sodium-containing raw materials are used, which greatly reduces the cost of catalyst preparation, the introduction of a large amount of sodium ions makes it difficult to remove the sodium ions in the catalyst. A large amount of water is needed to wash the precipitate to remove the alkali metal ions in the precipitate, thereby generating a large amount of salt-containing wastewater. As the country's requirements for sewage treatment become increasingly stringent, this type of wastewater faces the problems of large treatment volume and high treatment energy consumption. In addition, when the sodium ion content is high, washing can only remove the sodium ions on the surface of the catalyst, and a large amount of sodium ions still remain in the precipitated material. The residual sodium ions lead to poor adhesion of the material. The sodium ions that are not removed are not conducive to the formation of the catalyst pore structure, resulting in a smaller pore volume and pore size of the catalyst and fewer macropores.

[0005] CN101502803A discloses a method for preparing a catalyst for the selective hydrogenation of dimethyl maleate to produce 1,4-butanediol, using a two-step process with the addition of metal additives such as Mn, Mg, and Cr. CN1660490A discloses a method for preparing a methanol synthesis catalyst using a co-precipitation method, adding a small amount of surfactant OP. CN101733109A discloses a method for preparing a copper-based methanol synthesis catalyst, adding an organic additive (one or more of ethylene glycol, diethylamine, glycerol, magnesium stearate, and activated carbon) during the precipitation process. All of these methods enhance the dispersibility of CuO on the catalyst surface by adding reagents during the precipitation process. However, the addition of additives fails to increase the specific surface area or pore volume, nor does it optimize the pore distribution, resulting in limited improvement in the dispersion of the main active component, CuO, in the catalyst.

[0006] CN103801302A discloses a method for preparing a copper-zinc catalyst. The method involves introducing CO₂ gas into a zinc-containing soluble salt solution A to generate a zinc compound precipitate. CO₂ gas is introduced into a sodium aluminate solution to generate an aluminum-containing precipitate, which is then aged under stirring. Basic copper carbonate is added during aging, and the catalyst is washed, filtered, dried, calcined, and pressed into tablets to obtain a copper-containing catalyst. This method increases the surface area of the catalyst, but the catalyst has fewer macropores, and the resulting precipitated material has poor cohesiveness and is not easily pressed into tablets.

[0007] CN110935457A discloses a copper-zinc catalyst and its preparation method. The copper-zinc catalyst of the invention is prepared by a co-flow gelation reaction of a mixed solution A and a sodium metaaluminate solution, wherein the mixed solution A is an aqueous solution containing a soluble copper salt, a soluble zinc salt, and an organic additive to obtain a slurry I, which is then aged. Then, a mixed solution B and a sodium carbonate solution are co-flowed and dropwise added to the aged slurry I to undergo a gelation reaction to obtain a slurry II. The slurry is then aged, dried, and formed to obtain a catalyst. The catalyst of the invention has a high sodium content and, therefore, a small specific surface area and pore volume. CN107774263A discloses a preparation method for a synthetic methanol catalyst, wherein a sodium metaaluminate alkaline solution and a soluble salt solution containing Cu are simultaneously and concurrently added to a reactor containing clean water to perform a gelling reaction, generating slurry I, and then the sodium metaaluminate alkaline solution is added dropwise to a soluble salt solution containing Zn to perform a gelling reaction, generating slurry II, slurry I and slurry II are uniformly mixed, aged and filtered, and the resulting material is hydrothermally treated with water vapor, wherein urea is added during the hydrothermal treatment, followed by washing, filtering, drying, roasting, and tableting to obtain a catalyst. Although the active metal copper content in the catalyst surface phase prepared by this method is high, the dispersion of copper and zinc in the catalyst is reduced under the action of water vapor pressure and the impact of water molecules.

[0008] The above method changes the copper-based catalyst preparation process or adds an additive on this basis to change the dispersion of copper on the reduced catalyst and improve the activity of the catalyst, but there is no significant increase in the specific surface area and pore volume of the catalyst, and the effect of improving the dispersion of the active components is not obvious. Summary of the Invention

[0009] To address the shortcomings of the prior art, the present invention provides a method for preparing a methanol synthesis catalyst. The catalyst prepared by this method exhibits a large pore volume and pore diameter, with the pore distribution primarily concentrated in the macropores. The active metal copper and the additive zinc exhibit excellent dispersion and a synergistic effect, thereby improving the activity, selectivity, thermal stability, and service life of the methanol synthesis catalyst.

[0010] The preparation method of the methanol synthesis catalyst of the present invention comprises the following contents:

[0011] (1) A solution containing Zn, Cu, and an additive and a sodium aluminate solution are subjected to a gelling reaction to obtain a slurry;

[0012] (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;

[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. After the first stage aging, 1 / n Al-containing solution is added; 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 value is adjusted to 5.5-8.3, and the aging time is 0.05-0.5 hours. Wherein n is an integer from 2 to 8;

[0014] (3) The formed product is immersed in an organic acid solution of a carboxylic acid polymer and / or an organic phosphonic acid compound, and then subjected to desalination treatment, washing, drying and calcination to obtain a methanol synthesis catalyst.

[0015] In the method of the present invention, in the Zn and Cu solution in step (1), the concentration of soluble copper salt is Cu 2+ The concentration of soluble zinc salt is 1.0-6.0 mol / L, preferably 1.5-6.0 mol / L. 2+The weight concentration of the additive in terms of additive oxide is 0.5-6.0 mol / L, preferably 1.0-4.0 mol / L. The weight concentration of the additive is 2-70 g / L, preferably 3-60 g / 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. The additive is one or more of Ti, Zr, P, and B. The titanium source can be one or more of titanium nitrate, titanium sulfate, and titanium chloride. The zirconium source can be one or more of zirconium nitrate, zirconium chloride, and zirconium oxychloride. The phosphorus source is one or more of phosphoric acid, ammonium hydrogen phosphate, and ammonium dihydrogen phosphate. The boron source is boric acid.

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

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

[0018] Preferably, the pH value can be adjusted downward from the initial value to the final pH value by a stepwise method. The stepwise 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 step of adjustment. The number of steps of adjustment is 2 to 10 times, preferably 2 to 8 times.

[0019] More preferably, the pH is maintained constant for 0.1 to 1.2 hours after each downward adjustment. The magnitude of each downward adjustment may be the same or different, and preferably, the magnitude of each downward adjustment is equal to or less than the magnitude of the previous downward adjustment. The time taken for each downward adjustment process is the time from the start of this downward adjustment to the start of the next downward adjustment, and further, is the sum of the time used for each pH downward adjustment and the time during which the pH value remains constant. The time taken for each downward adjustment process may be the same or different, and preferably, the same time.

[0020] In the method of the present invention, in step (2), the acid and base used to adjust the pH value can be inorganic salts, inorganic acids and inorganic bases that do not contain aluminum elements, and can further be one or more of hydrochloric acid and acetic acid, sodium carbonate and sodium bicarbonate. The concentration and amount 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 amount of Al added accounts for 5% to 45%, preferably 6% to 40%, of the total Al in the resulting methanol synthesis catalyst, calculated as Al2O3. When preparing the Al-containing solution, the aluminum source is generally a soluble aluminum salt, which can be one or more of aluminum nitrate, aluminum sulfate, aluminum chloride, etc., and is divided into n equal parts by volume, where n is an integer from 2 to 8.

[0022] In the method of the present invention, the solid-liquid separation in step (2) is generally carried out by filtration, centrifugation or the like.

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

[0024] In the method of the present invention, during the molding process described in step (2), a conventional molding extrusion aid can be added as needed. The extrusion aid refers to a substance that is conducive to extrusion molding, such as one or more of carbon black, graphite powder, etc. The amount of the extrusion aid is 1wt% to 10wt% of the total material dry basis.

[0025] In the method of the present invention, the water content of the organic acid solution of the carboxylic acid polymer and / or the organic phosphonic acid compound in step (3) is adjusted according to the volume of the catalyst to be soaked, so as to achieve sufficient soaking of the catalyst. In the method of the present invention, the carboxylic acid polymer in step (3) has a molecular weight of 400 to 5000 and is selected from one or more of polyacrylic acid, polymethacrylic acid, polymaleic acid, polyaspartic acid, polyepoxysuccinic acid, acrylic acid-hydroxypropyl acrylate copolymer, and maleic acid-acrylic acid copolymer, preferably one or more of polyacrylic acid, polymethacrylic acid, polymaleic acid, polyaspartic acid, or polyepoxysuccinic acid. The organic phosphonic acid compound is selected from one or more of hydroxyethylene diphosphonic acid, polyol phosphonate, 2-hydroxyphosphonoacetic acid, and 1,2,4-tricarboxylic acid-2-phosphonobutane.

[0026] In the method of the present invention, the organic acid in step (3) is selected from carboxylic acids with a carbon number of C2 to C8, and is further selected from one or more of malic acid, citric acid, isocitric acid, tartaric acid, oxalic acid, succinic acid, salicylic acid, lactic acid, β-hydroxybutyric acid, maleic acid, glutaric acid, adipic acid, benzoic acid or malonic acid, preferably one or more of malic acid, citric acid, tartaric acid, oxalic acid, succinic acid, salicylic acid or maleic acid.

[0027] In the method of the present invention, the molar ratio of the organic phosphonic acid compound or / and carboxylic acid polymer to the organic acid in step (3) is 0.5:1 to 5:1, preferably 0.8:1 to 4:1; and the molar ratio of the total molar number of the organic phosphonic acid compound or / and carboxylic acid polymer and the organic acid in the organic auxiliary solution to the Cu in the Zn- and Cu-containing solution is 0.1 to 2.0, preferably 0.15 to 1.8.

[0028] The liquid-to-solid volume ratio of the soaking in step (3) is 1.0 to 5.0, preferably 1.0 to 4.0; the soaking time is 1.0 to 12.0 hours, preferably 1.5 to 10.0 hours.

[0029] In the method of the present invention, the desalination treatment process described in step (3) is: first curing is performed, and then washing is performed to remove salt precipitated on the surface of the molded object. The curing conditions are a temperature of 5 to 100°C, preferably a temperature of 10 to 90°C, and a time of 10 to 100 hours, preferably 24 to 90 hours.

[0030] 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, and the curing time is 5-60 hours, preferably 8-55 hours, so that the hydrated sodium ions are precipitated and vacancies are retained; in the second stage, the temperature is 10-30°C, and the time is 1-48 hours, preferably 2-42 hours, so that the vacancies are retained and shrunk, so that the pore volume of the catalyst is increased and the mechanical strength is good, and then the precipitated salt is removed by washing. The washing process can use a solvent with good solubility for sodium salts, such as water and ethanol.

[0031] In the method of the present invention, the washing, drying, and calcining in step (4) can be carried out under conventional conditions in the art. The washing is performed with deionized water until neutral. The drying conditions are as follows: drying at 50-150°C, preferably 60-120°C, for 0.5-24.0 hours, preferably 1-16 hours. The calcining conditions are as follows: calcining at 300-360°C for 1-16 hours, preferably 2-10 hours.

[0032] The methanol synthesis catalyst prepared by the method of the present invention comprises the following components, based on the weight of the catalyst: CuO is 25% to 70%, preferably 30% to 60%, ZnO is 12% to 38%, preferably 15% to 35%, Al2O3 is 10% to 40%, preferably 15% to 38%, and the auxiliary agent is an auxiliary oxide, accounting for 2% to 19%, preferably 3% to 17%.

[0033] 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 0.30-0.90 ml / g, and the pore size distribution is as follows: the pore volume of pores below 10 nm accounts for 3%-20% of the total pore volume, the pore volume of pores between 10 and 15 nm accounts for 15%-48% of the total pore volume, and the pore volume of pores above 15 nm accounts for 45%-75% of the total pore volume. The preferred pore size distribution is as follows: the pore volume of pores below 10 nm accounts for 5%-18% of the total pore volume, the pore volume of pores between 10 and 15 nm accounts for 20%-45% of the total pore volume, and the pore volume of pores above 15 nm accounts for 48%-70% of the total pore volume.

[0034] The specific surface area of the metallic copper in the catalyst after reduction is 45 to 140 m 2 / g, preferably 50 to 130 m 2 The dispersion degree of metallic copper is 20% to 50%, preferably 25% to 45%.

[0035] The Na2O content in the methanol synthesis catalyst prepared by the method of the present invention is less than 0.12%, preferably less than 0.10%.

[0036] The methanol synthesis catalyst prepared by the method of the present invention is used in the methanol synthesis reaction. The general process conditions are: reaction temperature 210-320°C, preferably 230-290°C; pressure 2.0-10MPa, preferably 2.0-8.0MPa; volume space velocity 2000-15000 h -1 , preferably 4000~12000 h -1 .

[0037] Compared with the existing technology, the active metal of the catalyst prepared by the method of the present invention is more dispersed, there is a good synergistic effect between Cu-ZnO, the catalyst pore distribution is concentrated (mainly concentrated above 15nm), and it has the characteristics of high activity, high selectivity and heat resistance.

[0038] 1. The catalyst preparation method of the present invention is simple, convenient, and low-investment, and effectively reduces the amount of salt-containing wastewater generated during the catalyst preparation process. The inventor first retains the sodium salt in the material during the molding process, and then desalts the molded material to remove the precipitated sodium salt. In this process, due to the placeholder effect of the sodium salt during the molding process, the vacancies after sodium removal are more conducive to the formation of the catalyst pore structure, the pore distribution moves toward the macropore direction, the pore volume and pore diameter of the catalyst increase, and the diffusion performance of the catalyst is improved, solving the problem of poor dispersion of active metals in the methanol synthesis catalyst used in the prior art, fewer macropores in the catalyst, and difficulty in molding. After the molded object is soaked in a special organic acid solution, the sodium salt in the molded object is easier to remove, the formation of the catalyst pore structure is easier, and the pores are more unobstructed.

[0039] 2. In the method of the present invention, when the composite oxide of copper, zinc and aluminum is formed, a pH value decreasing gelling method is adopted, which can reduce the CuO grain size, increase the specific surface area of metallic copper, and produce a good synergistic effect between Cu and ZnO. At the same time, the addition of auxiliary components can effectively improve the dispersion of metallic copper and further enhance the interaction between Cu and ZnO.

[0040] 3. In the method for preparing a synthetic methanol catalyst of the present invention, an Al-containing solution is added in portions during the pH swing during aging, thereby further enhancing the supporting effect of the Al2O3 skeleton, making the pores unobstructed, facilitating the smooth passage of macromolecular reactants, promoting the dispersion of active metals, and strengthening the mutual promotion effect between active metals, which is beneficial to improving the catalyst activity, methanol selectivity and thermal stability. At the same time, the sodium ion content on the surface of the phase is increased, which is more conducive to desalination treatment. DETAILED DESCRIPTION

[0041] The following examples further illustrate the scheme and effects of the present invention. In the present invention, the specific surface area, pore volume and pore distribution are measured by low temperature liquid nitrogen adsorption method. The specific surface area (S Cu ) and dispersion (D Cu ) was determined using the N2O chemical reaction adsorption method. v% is the volume fraction, and wt% is the mass fraction.

[0042] Example 1

[0043] Dissolve copper nitrate, zinc nitrate and zirconium oxychloride in deionized water to prepare mixed solution A. 2+ The concentration is 3.8 mol / L, Zn 2+The concentration is 3.2 mol / L, and the weight concentration of Zr calculated as ZrO2 is 16 g / 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 resulting methanol synthesis catalyst calculated as Al2O3. The solution is then divided into four equal parts by volume. Deionized water was added to the reaction tank, and the sodium aluminate solution and mixed solution A were added to the reaction tank in parallel. The gelling temperature was 60°C, and the pH value was initially controlled at 13.1. The pH value was adjusted downward seven times to a final pH value of 7.5 at the end. The pH value was lowered by 0.8 each time. After each adjustment to the adjusted value, the adjusted pH value of the reaction slurry was kept constant for 8 minutes. After the reaction, a slurry containing copper, zinc, aluminum, and zirconium was obtained. The obtained slurry was aged at 76°C. The pH value was first controlled to 13.0 during aging. After aging for 0.3 hours, 1 equal portion of aluminum chloride solution was added and the aging pH value was controlled to 9.5. After aging for 0.2 hours, the pH value was then controlled to 7.6. After aging for 0.2 hours, the above operation process was repeated four times to terminate the aging. The aged slurry was filtered, the filter cake was dried at 90°C for 10 hours, and an appropriate amount of graphite and water were added for rolling and tableting. Polyacrylic acid (molecular weight 3000) and citric acid were mixed and deionized water was added to prepare an organic acid solution. The molar ratio of the sum of the moles of polyacrylic acid and citric acid to the Cu in the solution containing Zn, Cu, and Zr was 0.8, and the molar ratio of polyacrylic acid to citric acid was 1.6. The molded product was immersed in the organic acid solution at a volume ratio of 1.2 for 7 hours. After immersion, the molded product was cured at 70°C for 48 hours, then the temperature was lowered to 20°C and continued to cure for 30 hours. The molded product was washed with deionized water until neutral, 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.

[0044] Example 2

[0045] According to the method of Example 1, according to the component ratio of Catalyst B in Table 1, copper nitrate, zinc nitrate, and titanium chloride were dissolved in deionized water to form a mixed solution A, and aluminum sulfate was dissolved in deionized water to form an aluminum sulfate solution. The Al in the aluminum sulfate solution accounted for 34.2% of the total Al in the resulting methanol synthesis catalyst as Al2O3. The solution was then divided into 6 equal parts by volume. Deionized water was added to the reaction tank, and the sodium aluminate solution and the mixed solution A were added to the reaction tank in parallel. The gelling temperature was 65°C, and the pH value was initially controlled to 12.8. The pH value was lowered 6 times to adjust the final pH value to 7.4 at the end. The pH value was lowered by 0.9 each time. After each adjustment to the adjusted value, the adjusted pH value of the reaction slurry was kept constant for 15 minutes to obtain a slurry containing copper, zinc, aluminum and titanium. The obtained slurry was aged at an aging temperature of 80°C. The pH value was first controlled to 12.5 during aging. After aging for 0.2 hours, 1 equal portion of aluminum sulfate solution was added and the aging pH value was controlled to 9.8. After aging for 0.2 hours, the pH value was then controlled to 6.8 for 0.1 hours. The above operation process was repeated 6 times to terminate aging. The aged slurry was filtered, and the filter cake was dried at 90°C for 10 hours. An appropriate amount of graphite and water were added for rolling and tableting. Hydroxyethylene diphosphonic acid and oxalic acid were mixed and added to deionized water to prepare an organic acid solution. The molar ratio of the sum of the moles of hydroxyethylene diphosphonic acid and oxalic acid to the moles of Cu in the Zn, Cu, and Ti solution was 1.0, and the molar ratio of the sum of the moles of hydroxyethylene diphosphonic acid to the moles of oxalic acid was 3.0. The tablet was then immersed in this organic acid solution at a volume ratio of 1.2 to the tablet for 7.5 hours. After immersion, the tablet was removed and cured at 80°C for 45 hours. The temperature was then lowered to 20°C and continued to cure for another 35 hours. The tablet was washed with deionized water until neutral, dried at 80°C for 10 hours, and calcined at 350°C for 4 hours to obtain Catalyst B. The composition, pore distribution, and main properties are shown in Table 1.

[0046] Example 3

[0047] According to the method of Example 1, copper nitrate, zinc nitrate, and phosphoric acid were dissolved in deionized water according to the component ratio of Catalyst C in Table 1 to prepare mixed solution A. AlCl3·6H2O was dissolved in deionized water to prepare aluminum chloride solution. The Al in the aluminum chloride solution accounted for 31.8% of the total Al in the resulting methanol synthesis catalyst, calculated as Al2O3. The solution was then divided into five equal portions by volume. Deionized water was added to the reaction tank, and the sodium aluminate solution and the mixed solution A were added to the reaction tank in parallel. The gelling temperature was 55°C, and the pH value was initially controlled to 12.3. The pH value was lowered 5 times to adjust the final pH value to 7.3 at the end. The pH value was lowered by 1.0 each time. After each adjustment to the adjusted value, the adjusted pH value of the reaction slurry was kept constant for 13 minutes to obtain a slurry containing copper, zinc, aluminum and phosphorus. The obtained slurry was aged at an aging temperature of 83°C. The pH value was first controlled to 12.1 during aging. After aging for 0.2 hours, 1 equal portion of aluminum chloride solution was added and the aging pH value was controlled to 9.8. After aging for 0.1 hour, the pH value was then controlled to 7.3 for 0.15 hours. The above operation process was repeated 5 times to terminate aging. The aged slurry was filtered, and the filter cake was dried at 100°C for 8 hours. An appropriate amount of graphite and water were added for rolling and tableting. Hydroxyethylene diphosphonic acid, polymaleic acid (molecular weight 450), and tartaric acid were mixed and deionized water was added to prepare an organic acid solution. The molar ratio of the sum of the moles of hydroxyethylene diphosphonic acid, polymaleic acid (molecular weight 450), and tartaric acid to the Cu in the solution containing Zn, Cu, and P was 1.2, and the molar ratio of the sum of the moles of hydroxyethylene diphosphonic acid and polymaleic acid (molecular weight 450) to the tartaric acid was 2.4. The pellet was then immersed in the organic acid solution at a volume ratio of 1.1 to the pellet for 8 hours. After immersion, the pellet was removed and cured at 20°C for 75 hours. The pellet was then washed with deionized water until neutral. The filter cake was dried at 90°C for 10 hours and calcined at 340°C for 5 hours to obtain Catalyst C. The composition, pore distribution, and main properties are shown in Table 1.

[0048] Example 4

[0049] According to the method of Example 1, copper nitrate, zinc nitrate, and boric acid were dissolved in deionized water to prepare a mixed solution A according to the component ratio of Catalyst D in Table 1. AlCl3·6H2O was dissolved in deionized water to prepare an aluminum chloride solution. The Al in the aluminum chloride solution accounted for 32% of the total Al in the resulting methanol synthesis catalyst, calculated as Al2O3. The solution was then divided into 7 equal parts by volume. Deionized water was added to the reaction tank, and the sodium aluminate solution and the mixed solution A were added to the reaction tank in parallel. The gelling temperature was 52°C, and the pH value was initially controlled at 12.9. The pH value was adjusted down 7 times to a final pH value of 7.3 at the end. The pH value was lowered by 0.8 each time. After each adjustment to the adjusted value, the pH value of the adjusted reaction slurry was kept constant for 16 minutes to obtain a slurry containing copper, zinc, aluminum and boron. The obtained slurry was aged at an aging temperature of 78°C. The pH value was first controlled to 13.3 during aging. After aging for 0.15 hour, 1 equal portion of aluminum chloride solution was added and the aging pH value was controlled to 9.7. After aging for 0.2 hour, the pH value was then controlled to 7.3 for 0.15 hour. The above operation process was repeated 7 times to terminate the aging. The aged slurry was filtered, and the filter cake was dried at 90°C for 8 hours. An appropriate amount of graphite and water were added for rolling and tableting. Polyacrylic acid and salicylic acid were mixed, and purified water was added to prepare an organic additive solution. The molar ratio of the sum of the moles of polyacrylic acid and salicylic acid to the molar ratio of Cu in the solution containing Zn, Cu, and B was 1.1, and the molar ratio of polyacrylic acid to salicylic acid was 3.4. The resulting product was then immersed in the organic acid solution at a volume ratio of 1.2 to the product for 7.5 hours. After immersion, the product was removed and cured at 35°C for 80 hours, then washed with deionized water until neutral, dried at 80°C for 13 hours, and calcined at 350°C for 4 hours to obtain Catalyst D. The composition, pore size distribution, and main properties are shown in Table 1.

[0050] Comparative Example 1

[0051] According to the component ratios of Catalyst A listed in Table 1, Cu(NO₃)₂·3H₂O and Zn(NO₃)₂·6H₂O were dissolved in deionized water to form a mixed solution. Deionized water was added to a reaction tank, and sodium metaaluminate solution (and the mixed solution) were added concurrently thereto. The gelation temperature was 60°C, the gelation time was 1 hour, and the reaction pH was 7.5 to obtain a reaction slurry. The slurry was aged under stirring at a pH of 7.6, an aging temperature of 76°C, and an aging time of 2.8 hours. The aged slurry was filtered, and the filter cake was dried at 90°C for 10 hours. An appropriate amount of graphite and water were added for rolling, and tablets were formed. The formed material was washed with deionized water until neutral, dried at 100°C for 8 hours, and calcined at 360°C for 3 hours to obtain Catalyst E. The composition, pore distribution, and main properties are shown in Table 1.

[0052] Comparative Example 2

[0053] According to the method disclosed in CN107774263A, a reference agent F having the same catalyst composition as that of Example 1 was prepared. The specific process is as follows:

[0054] According to the catalyst composition of Example 1, Cu(NO₃)₂·3H₂O was dissolved in deionized water to form Solution A. Zn(NO₃)₂·6H₂O was dissolved in deionized water to form Mixed Solution B. Deionized water was added to a reaction tank, and a sodium metaaluminate solution (containing 38 g / L of Al₂O₃) and Mixed Solution A were added concurrently to the reaction tank. The gelation temperature was 60°C, the pH was 7.5, and the gelation time was 1.0 hour, yielding a copper- and aluminum-containing precipitate slurry I. The sodium metaaluminate solution (containing 38 g / L of Al₂O₃) was added to Solution B with stirring, the gelation temperature maintained at 60°C, the pH controlled at 7.5, and the gelation time controlled at 1 hour, yielding a zinc- and aluminum-containing precipitate slurry II. The two precipitate-containing slurries were mixed. Aging was initiated with stirring, at a pH of 7.6 and a temperature of 76°C for 2.8 hours. After aging, the material was filtered, and the filter cake was hydrothermally treated in the presence of urea-containing water vapor. The hydrothermal treatment conditions were: a molar ratio of urea to the total amount of active metal atoms of 7:1, a temperature of 230°C, a pressure of 6.0 MPa, and a treatment time of 4 hours. The filter cake was dried at 90°C for 10 hours, rolled with appropriate amounts of graphite and water, and pressed into tablets. The formed material was washed with deionized water until neutral, dried at 100°C for 8 hours, and calcined at 360°C for 3 hours to obtain Catalyst F. The composition, pore distribution, and main properties are shown in Table 1.

[0055] Comparative Example 3

[0056] Catalyst G was prepared according to the method of Example 1 and the component proportions of Catalyst A in Table 1. The formed tablets were not subjected to desalination treatment.

[0057] Dissolve copper nitrate, zinc nitrate and zirconium oxychloride in deionized water to prepare a solution containing Zn and Cu. 2+ The concentration is 3.8 mol / L, Zn 2+The concentration is 3.2 mol / L, and the weight concentration of Zr calculated as ZrO2 is 16 g / 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 resulting methanol synthesis catalyst calculated as Al2O3. The solution is then divided into four equal parts by volume. Deionized water was added to the reaction tank, and the sodium aluminate solution and mixed solution A were added to the reaction tank in parallel. The gelling temperature was 60°C, and the pH value was initially controlled at 13.1. The pH value was adjusted downward seven times to a final pH value of 7.5 at the end. The pH value was lowered by 0.8 each time. After each adjustment to the adjusted value, the adjusted pH value of the reaction slurry was kept constant for 8 minutes. After the reaction, a slurry containing copper, zinc, aluminum, and zirconium was obtained. The obtained slurry was aged at 76°C. The pH value was first controlled to 13.0 during aging. After aging for 0.3 hours, 1 equal portion of aluminum chloride solution was added and the aging pH value was controlled to 9.5. After aging for 0.2 hours, the pH value was then controlled to 7.6. After aging for 0.2 hours, the above operation process was repeated four times to terminate the aging. The aged slurry was filtered, the filter cake was dried at 90°C for 10 hours, and an appropriate amount of graphite and water were added for rolling and tableting. The molded material was washed with deionized water until neutral, 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.

[0058] Comparative Example 4

[0059] According to the gelling reaction conditions of Example 1 and conventional aging conditions, a reference agent H having the same catalyst composition as that of Example 1 of the present invention was prepared.

[0060] Dissolve Cu(NO3)2·3H2O, Zn(NO3)2·6H2O and zirconium oxychloride in deionized water to prepare a mixed solution. 2+ The concentration is 3.2 mol / L, Zn 2+The concentration is 2.7 mol / L, and the weight concentration of Zr calculated as ZrO2 is 16 g / L. Deionized water is added to the reaction tank, and the sodium aluminate solution (containing 58 g / L of Al2O3) and the mixed solution A are added to the reaction tank in parallel. The gelling temperature is 60°C, and the initial pH value is controlled at 13.1. The pH value is adjusted downward seven times to a final pH value of 7.5 at the end. The pH value is lowered by 0.8 each time. After each adjustment to the adjusted value, the adjusted pH value of the reaction slurry is controlled constant for 8 minutes. After the reaction is completed, a slurry containing copper, zinc, aluminum, and zirconium is obtained. The obtained slurry is aged at an aging temperature of 76°C and a pH value of 7.8 during aging. After aging for 2 hours, the aging is terminated. The aged slurry was filtered, and the filter cake was dried at 90°C for 10 hours. An appropriate amount of graphite and water were added for rolling and tableting. The tablets were then cured at 70°C for 50 hours, then the temperature was lowered to 20°C and continued to cure for 30 hours. The tablets were washed with deionized water until neutral, dried at 100°C for 8 hours, and calcined at 360°C for 3 hours to obtain Catalyst H. The composition, pore distribution, and main properties are shown in Table 1.

[0061] Comparative Example 5

[0062] According to the method disclosed in CN110935457A, a reference agent I having the same catalyst composition as that of Example 1 was prepared. The specific process is as follows:

[0063] Dissolve Cu(NO3)2·3H2O and Zn(NO3)2·6H2O in deionized water, add 116 g of hydroxyethylene diphosphonic acid and mix well to prepare mixed solution A. 2+ The concentration is 2.8 mol / L, Zn 2+ The concentration is 2.5mol / L. Dissolve Cu(NO3)2·3H2O and AlCl3·6H2O in deionized water to prepare mixed solution B. 2+ The concentration is 1.8 mol / L, Al 3+The concentration was 2.0 mol / L. Deionized water was added to the reaction tank, and the sodium metaaluminate solution and mixed solution A were added concurrently to the reaction tank. The gelation temperature was 60°C, the gelation pH was 7.5, and the gelation time was 0.9 hour to obtain slurry I. Slurry I was aged under stirring at a stirring speed of 190 rpm, an aging temperature of 75°C, a pH of 7.2, and an aging time of 0.7 hour. After aging, mixed solution B and sodium carbonate solution were added concurrently to the aged slurry I. The molar ratio of sodium carbonate to the total amount of copper and zinc was 2.0. The gelation temperature was 62°C, the pH was 9.2, and the gelation time was 2.0 hours. This yielded slurry II. Slurry II was then aged with stirring at 400 rpm, 75°C, a pH of 8.5, and 3.0 hours. The aged slurry II was filtered, and the filter cake was washed three times with deionized water. The filter cake was dried at 100°C for 10 hours and calcined at 360°C for 3 hours. An appropriate amount of graphite and water were added to the calcined material and pressed into sheets to yield catalyst I. The composition, pore distribution, and main properties are shown in Table 1.

[0064] Example 5

[0065] The methanol synthesis catalyst was crushed into 16-40 mesh and reduced with a low-concentration hydrogen (H2 / N2 = 3 / 97 (volume ratio)) nitrogen-hydrogen mixture for 16-25 hours before use, with a maximum reduction temperature of 235°C. The catalyst activity was evaluated in a micro-fixed-bed reactor. The catalyst loading was 5 ml, the feed gas composition was CO / H2 / CO2 / N2 = 13 / 70 / 6 / 11 (volume ratio), the reaction pressure was 5.0 MPa, and the space velocity was 10,000 h-1. -1 The reaction temperature was 245°C, and the conversion rates of CO and CO2 were measured as the initial activity of the catalyst. The catalyst was then heat-treated at 445°C for 5 hours in a synthetic atmosphere, then lowered to 250°C to measure the conversion rates of CO and CO2 as the activity after heat treatment, i.e., heat resistance. The product was analyzed by gas chromatography, and the space-time yield of methanol produced was g·mL. -1 ·h -1 That is, the number of grams of methanol produced per milliliter of catalyst per hour. The results are shown in Table 3.

[0066] As can be seen from Tables 1 and 2, the metals in the catalyst of the present invention are well dispersed, thereby improving the synergistic effect between the Cu-ZnO catalysts. The pore structure distribution moves toward the macropore direction, mainly concentrated above 15 nm. Within this pore distribution range, the catalyst has high activity and selectivity. From the test results, it can be seen that the methanol synthesis catalyst of the present invention has high activity, heat resistance and excellent selectivity.

[0067] Table 1 Catalyst composition and properties

[0068]

[0069] Table 1 Catalyst composition and properties

[0070]

[0071] Table 2 Dispersion and specific surface area of metallic copper

[0072]

[0073] S Cu is the specific surface area of copper, D Cu is the dispersion of copper

[0074] Table 3 Catalyst activity evaluation and heat resistance test results

[0075]

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, Cu and an additive with a sodium aluminate solution to form a gel to obtain a slurry; (2) subjecting the slurry obtained in step (1) to a three-stage decreasing pH aging process n times, adding 1 / n Al-containing solution at the end of the first-stage pH aging process each time, subjecting the obtained material after aging to solid-liquid separation, and subjecting the solid phase to drying and tableting to obtain a formed object; The specific details of each three-stage decreasing pH aging process are as follows: the aging temperature is 60-98°C; the first stage, the pH value is 11.0-13.5, the aging time is 0.05-0.5 hours, and 1 / n Al-containing solution is added after the first stage aging is completed; the second stage, the pH value is adjusted to 8.5-10.5, and the aging time is 0.05-0.5 hours; the third stage, the pH is adjusted to 5.5-8.3, and the aging time is 0.05-0.5 hours; wherein n is an integer from 2 to 8; (3) the molded product is immersed in an organic acid solution of a carboxylic acid polymer and / or an organic phosphonic acid compound, and then desalted, washed, dried and calcined to obtain a methanol synthesis catalyst; the desalting 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; the second stage temperature is 10-30°C, the time is 1-48 hours, and then washed to remove the precipitated salt; the auxiliary agent is one or more of Ti, Zr, P, and B.

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 weight concentration of the additive as additive oxide is 2~70g / L.

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 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; when preparing the Al-containing solution, the aluminum source is a soluble aluminum salt selected from one or more of aluminum nitrate, aluminum sulfate, and aluminum chloride, which is divided into n equal parts by volume, where n is an integer of 2 to 8.

7. The method according to claim 1, wherein: The carboxylic acid polymer in step (3) has a molecular weight of 400 to 5000 and is selected from one or more of polyacrylic acid, polymethacrylic acid, polymaleic acid, polyaspartic acid, polyepoxysuccinic acid, acrylic acid-hydroxypropyl acrylate copolymer and maleic acid-acrylic acid copolymer; the organic phosphonic acid compound is selected from one or more of hydroxyethylidene diphosphonic acid, polyol phosphonate, 2-hydroxyphosphonoacetic acid and 1,2,4-tricarboxylic acid-2-phosphonobutane; the organic acid is selected from carboxylic acids with a carbon number of C2 to C8 and is selected from one or more of malic acid, citric acid, isocitric acid, tartaric acid, oxalic acid, succinic acid, salicylic acid, lactic acid, β-hydroxybutyric acid, maleic acid, glutaric acid, adipic acid, benzoic acid or malonic acid.

8. The method according to claim 1, wherein: The molar ratio of the organic phosphonic acid compound and / or carboxylic acid polymer to the organic acid in step (3) is 0.5:1 to 5:1; the molar ratio of the total moles of the organic phosphonic acid compound and / or carboxylic acid polymer and the organic acid to the Cu in the Zn and Cu solution is 0.1 to 2.

0.

9. The method according to claim 1, wherein: The liquid-to-solid volume ratio of the soaking in step (3) is 1.0 to 5.0, and the soaking time is 1.0 to 12.0 hours.

10. A methanol synthesis catalyst prepared according to any one of claims 1 to 9, characterized in that: Based on the weight of the catalyst, the catalyst comprises the following components: CuO is 25% to 70%, ZnO is 12% to 38%, Al2O3 is 10% to 40%, and the additive is an additive oxide is 2% to 19%, and the additive is one or more of Ti, Zr, P, and B; 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.

11. A methanol synthesis catalyst prepared according to any one of claims 1 to 9, 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%.

12. A methanol synthesis catalyst prepared according to any one of claims 1 to 9, characterized in that: The Na2O content in the catalyst is less than 0.12%.

13. Use of a methanol synthesis catalyst prepared according to any one of claims 1 to 9 in a methanol synthesis reaction, wherein the process conditions are: reaction temperature 210-320°C, pressure 2.0-10 MPa, and volume space velocity 2000-15000 h-1 -1 .

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