A method for preparing a copper-zinc catalyst

Abstract

The application discloses a preparation method of a copper-zinc catalyst, which comprises the following steps: (1) dropping an alkaline precipitator into a solution containing Cu and Zn to perform a gelation reaction, during the reaction process, when the pH value reaches a starting value, the pH value is adjusted by n times until a terminal value, 1 / n volume of an Al-containing solution is added during each adjustment process, and the gelation is ended after a constant time after each adjustment; (2) the Cu-Zn-Al-containing slurry obtained in the step (1) is aged for m times of three-stage decreasing pH values, 1 / m volume of a sodium metaaluminate solution is added in the first stage each time, and the material obtained after the aging is subjected to solid-liquid separation, and the solid phase is dried and tablet-pressed to form the copper-zinc catalyst. The catalyst prepared by the method has the advantages that the copper particle size is small, the active component copper oxide has a large density in the catalyst surface phase, the active metal copper and the additive zinc have good dispersion performance, the Cu-ZnO has a good synergistic effect, and the activity, selectivity and thermal stability of the catalyst are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of synthesizing methanol, and particularly relates to a preparation method of a copper-zinc catalyst in a methanol synthesis reaction. BACKGROUND

[0002] The three components of CuO, ZnO and Al2O3 in the methanol synthesis catalyst have different functions. CuO is the main active component, and ZnO and Al2O3 are the additives. Al2O3 not only plays a skeleton role in the catalyst, but also can disperse the active components in the catalyst, and determines the distribution and morphology of the catalyst surface components. The dispersion degree, particle size of Cu obtained on the methanol synthesis catalyst, and the synergistic effect between the metal active center Cu and the oxide carrier have a great influence on the activity, methanol selectivity and stability of the Cu-based catalyst. The higher the copper dispersion degree is, the more the number of metal atoms exposed on the surface is, and the less the sintering of the active center is caused, so that the high activity of the catalyst is maintained. When the Cu particle size is small, the Cu particles have a large number of open sites and edge defect sites, which can strongly bind the key reaction intermediates, and increase the methanol yield. The selectivity of methanol is optimal when the Cu particle size is in the range of 7-10 nm. Meanwhile, the particle sizes of Cu and the carrier are controlled to be similar, so as to increase the face contact between Cu and the carrier, and enhance the interaction between them.

[0003] CN101502803A discloses a preparation method of a catalyst for preparing 1,4-butanediol by selective hydrogenation of dimethyl maleate. The additive metals of Mn, Mg and Cr are added on the basis of the two-step method. CN1660490A discloses a preparation method of a methanol synthesis catalyst. A small amount of surfactant OP is added in the preparation process by the coprecipitation method. CN101733109A discloses a preparation method of a copper-based methanol synthesis catalyst. An organic additive (one or more of ethylene glycol, diethylamine, glycerol, magnesium stearate and activated carbon) is added in the precipitation process. The above methods all add reagents in the precipitation process to improve the dispersion of CuO in the catalyst surface, but the addition of the additive does not increase the specific surface area and pore volume, and the dispersion of the main active component CuO in the catalyst is also limited.

[0004] CN103372440A discloses a preparation method of a methanol synthesis catalyst. CN107774263A discloses a preparation method of a methanol synthesis catalyst. Both of the two methods use the gas in the calcination to impact the pores of the catalyst, so as to change the pore volume and specific surface area of the catalyst. Although the active metal copper content in the catalyst surface prepared by the two methods is high, the dispersion of copper and zinc in the catalyst surface is reduced under the action of water vapor pressure and the impact of water molecules, and the particle size of copper is also large.

[0005] CN201811114240.9 discloses a copper-zinc catalyst and a preparation method thereof, which is prepared by a two-step precipitation method. The catalyst contains an organic phosphonic acid compound and / or a carboxylic acid polymer and an organic carboxylic acid. CN202011292868.5 discloses a preparation method of a high-activity and high-selectivity methanol synthesis catalyst. The method combines a two-step precipitation method and a multi-step impregnation method. The precipitate is soaked in a zinc nitrate solution, which is conducive to forming more active sites. Impregnating magnesium can neutralize the surface acidity of the catalyst, thereby improving the selectivity of the catalyst. The catalyst prepared by the above two methods has a small specific surface area and pore volume and a large Cu particle size, which affects the activity metal dispersion and the selectivity of the catalyst. SUMMARY

[0006] In view of the deficiencies in the prior art, the present application provides a preparation method of a copper-zinc catalyst. The catalyst prepared by the method has a small copper particle size, a large density of active component copper oxide in the catalyst surface, and good dispersion performance of active metal copper and additive zinc. Cu-ZnO has a good synergistic effect, which improves the activity, selectivity and thermal stability of the catalyst.

[0007] The preparation method of the copper-zinc catalyst of the present application comprises the following contents:

[0008] (1) The basic precipitator is added dropwise into a solution containing Cu and Zn to perform a gelation reaction. During the reaction process, when the pH value reaches the starting value, the pH value is adjusted n times until the end point value. In each adjustment process, 1 / n volume of an Al-containing solution is added. After each adjustment, a constant time is maintained. After the gelation is completed, a slurry containing Cu, Zn and Al is obtained. n is an integer between 2 and 8.

[0009] (2) The Cu, Zn and Al-containing slurry obtained in step (1) is subjected to m times of three-stage decreasing pH value aging. In each first stage, 1 / m volume of sodium metaaluminate solution is added. After aging, the obtained material is subjected to solid-liquid separation. The solid phase is dried, tabletized and formed. After washing, drying and calcination, a copper-zinc catalyst is obtained. m is an integer between 2 and 8.

[0010] In the method of the present application, the concentration of soluble copper salt in the Cu and Zn-containing solution in step (1) is 0.5-6.5 mol / L, preferably 0.8-6.3 mol / L, and the concentration of soluble zinc salt is 0.5-6.5 mol / L, preferably 0.8-6.3 mol / L. 2+ 2+ ​The concentration of the soluble copper salt is 0.3-4.5 mol / L, preferably 0.6-4.0 mol / L; the soluble zinc salt is a nitrate and / or acetate containing zinc; the Al-containing solution has a concentration of 5-90 g / L of Al2O3, preferably 10-85 g / L; and the Al-containing solution is divided into 2-8 parts by volume, preferably equal parts.

[0011] In the method, the basic precipitant in step (1) is selected from one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, potassium carbonate or potassium bicarbonate aqueous solution, preferably sodium carbonate solution and sodium hydroxide aqueous solution; and the concentration of the basic precipitant aqueous solution is prepared according to requirements, generally 5wt%-25wt%.

[0012] In the method, the gelation reaction conditions in step (1) are as follows: the reaction temperature is 30-90℃, preferably 40-85℃; and the reaction time is 0.5-6.0 hours, preferably 0.6-5.5 hours.

[0013] In the method, the initial pH value in step (1) is 4.0-6.0, preferably 4.2-5.8; and the final pH value is 8.0-10.5, preferably 8.2-10.3.

[0014] In the method, the pH value is kept constant for 0.1-0.5 hours after each time of pH value increase in step (1); and the increase amplitude of each time of pH value increase is equal to or less than that of the previous time of pH value increase.

[0015] In the method, the concentration of Al2O3 in the sodium meta-aluminate solution in step (2) is 5-70 g / L, preferably 7-65 g / L; and the sodium meta-aluminate solution is divided into m parts by volume, preferably equal parts.

[0016] In the method, the three-stage decreasing pH value aging process in step (2) is as follows: the aging temperature of each stage is 60-98℃, preferably 65-92℃; in the first stage, 1 / n of the sodium meta-aluminate solution is added dropwise to the reaction slurry to adjust the pH value to 11.5-13.5, and the aging time is 0.05-0.5 hours; in the second stage, the pH value is adjusted to 8.0-10.0, and the aging time is 0.05-0.5 hours; in the third stage, the pH value is adjusted to 4.0-6.5, and the aging time is 0.05-0.5 hours; and before the next three-stage decreasing pH value aging, the pH value is adjusted back to 11.5-13.5.

[0017] In the aging process, in addition to using sodium metaaluminate solution in the first stage of pH value adjustment, the acids and bases used for adjusting the pH value can be inorganic salts, inorganic acids and inorganic bases containing no aluminum element, the inorganic acid can be hydrochloric acid and acetic acid, and the inorganic base can be one or more of sodium carbonate, sodium bicarbonate, ammonia and sodium hydroxide; the concentration and amount of the acid and base solution can be adjusted according to the actual preparation needs.

[0018] In the method, in step (2), the Al added by the sodium metaaluminate solution accounts for 5% to 55%, preferably 6% to 50%, of the total Al in the obtained copper-zinc catalyst in terms of Al2O3.

[0019] In the method, the solid-liquid separation in step (2) is generally achieved by filtration, centrifugation or the like.

[0020] In the method, in the forming process in step (2), a conventional forming aid can be added as needed, the forming aid being a substance conducive to extrusion forming, such as one or more of carbon black, graphite powder and the like, and the amount of the forming aid accounting for 1wt% to 10wt% of the total material dry basis.

[0021] In the method, the washing, drying and calcination in step (2) can be achieved by using conventional conditions in the field, the washing being achieved by using deionized water until neutral, the drying being achieved at 50 to 150 DEG C, preferably 60 to 120 DEG C, for 0.5 to 24.0 hours, preferably 1 to 16 hours, and the calcination being achieved at 300 to 360 DEG C for 1 to 16 hours, preferably 2 to 10 hours.

[0022] The copper-zinc catalyst prepared by the method is in the form of cylindrical (solid) particles, the particle size of the catalyst particles being 2 to 12 mm, and the length being 1 to 8 mm.

[0023] The copper-zinc catalyst prepared by the method includes the following components based on the weight of the catalyst: CuO 25% to 72%, preferably 25% to 68%, ZnO 10% to 40%, preferably 12% to 35%, and Al2O3 10% to 38%, preferably 12% to 35%.

[0024] The copper-zinc catalyst prepared by the method includes the following components: active metal components Cu and Zn, and alumina; the ratio of the weight content of the surface phase active metal component CuO to the weight content of the bulk phase active metal component CuO is 2.5:1 to 7.5:1, preferably 2.8:1 to 7.0:1, and the ratio of the weight content of the surface phase active metal component ZnO to the weight content of the bulk phase active metal component ZnO is 1.8:1 to 6.5:1, preferably 2.1 to 6.0:1.

[0025] The specific surface area of the metallic copper in the catalyst after reduction is 50-150 m 2 / g, preferably 60-145 m 2 / g. The dispersion of the metallic copper in the catalyst surface is 26%-58%, preferably 30%-55%; the average particle size of the metallic copper is 7-10 nm; the particle size distribution of the metallic copper particles is as follows: the number of particles with a particle size less than 7 nm accounts for 3%-12% of the total number of particles, the number of particles with a particle size of 7 nm-10 nm accounts for 65%-89% of the total number of particles, and the number of particles with a particle size greater than 10 nm accounts for 5%-18% of the total number of particles

[0026] The copper-zinc catalyst has the following properties: the specific surface area is 120-550 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 2%-13% of the total pore volume, the pore volume of pores of 10-15 nm accounts for 30%-50% of the total pore volume, and the pore volume of pores above 15 nm accounts for 40%-68% of the total pore volume, preferably the pore size distribution is as follows: the pore volume of pores below 10 nm accounts for 3%-11% of the total pore volume, the pore volume of pores of 10-15 nm accounts for 33%-48% of the total pore volume, and the pore volume of pores above 15 nm accounts for 43%-65% of the total pore volume.

[0027] The copper-zinc catalyst prepared by the method is applied to a methanol synthesis reaction, and the general process conditions are as follows: the reaction temperature is 210-320 DEG C, preferably 230-290 DEG C; the pressure is 2.0-10 MPa, preferably 2.0-8.0 MPa; the volume space velocity is 2000-15000 h -1 , preferably 4000-12000 h -1 .

[0028] Compared with the prior art, the method has the following advantages:

[0029] (1) In the process of forming a composite oxide of copper, zinc and aluminum, the pH value is increased during the gel formation, and the aluminum-containing solution is added in several times, thereby improving the supporting effect of Al2O3 in the composite oxide, effectively improving the dispersion of the metallic copper, and ensuring that a good synergistic effect is generated between Cu-ZnO;

[0030] (2) In the aging process, the pH value is swung and the sodium metaaluminate solution is added in several times, the amorphous oxide in the oxide particles is dissolved by swinging the pH value, the size of the oxide particles is modified by adding the sodium metaaluminate solution, the growth of the oxide particles is controlled through m times of swinging the pH value, the oxide particles are more uniform and have a small particle size, and more active metals are exposed on the surface.

[0031] The copper-zinc catalyst prepared by the method has good dispersion of active metal, high density of copper oxide in the surface phase of the catalyst, small particle size of copper particles, and good pore distribution, which further improves the dispersion of the active component in the surface phase of the catalyst and promotes the synergistic effect of Cu-ZnO, and the catalyst has the advantages of high activity, high selectivity and heat resistance in the synthesis of methanol. DETAILED DESCRIPTION

[0032] The scheme and effects of the present application are further illustrated by the following examples. In the present application, the specific surface area and pore volume and pore distribution are measured by low-temperature liquid nitrogen adsorption method, the specific surface area (S Cu ) of the metal Cu of the reduced catalyst and the dispersion (D Cu ) in the surface phase of the catalyst are measured by N2O chemical reaction adsorption method.

[0033] In the present application, the average particle size and particle size distribution of the metal copper are measured by TEM transmission electron microscope (JSM-2100, Japan) by measuring 50-120 metal copper particles.

[0034] The content of the active metal in the surface phase of the catalyst is measured by X-ray photoelectron spectroscopy (XPS), and the content of the active metal in the bulk phase of the catalyst is measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). wt% is mass fraction. Example 1

[0035] Cu(NO3)2·3H2O and Zn(NO3)2·6H2O are dissolved in deionized water to prepare a Cu and Zn containing solution. The Cu 2+ concentration is 3.8 mol / L, and the Zn 2+The concentration of the AlCl3-6H2O was 3.2 mol / L. The AlCl3-6H2O was dissolved in deionized water to form an aluminum-containing solution, the weight concentration of Al in the Al-containing solution was 30.8 g / L as Al2O3, and the aluminum-containing solution was equally divided into 5 parts by volume. The sodium meta-aluminate solution contained 30% of the total Al in the obtained copper-zinc catalyst as Al2O3, and was equally divided into 5 parts by volume. The Cu- and Zn-containing solution was added to the reaction tank, the sodium carbonate solution was added dropwise into the reaction tank, the pH value was controlled to be 4.8, the final pH value at the end was adjusted to be 8.8 by 5 times of pH value increase, the pH value was increased by 0.8 each time, the adjusted reaction slurry pH value was kept constant for 10 minutes, and each time the pH value was increased by adding the precipitant, one part of the aluminum-containing solution was added at the same time, the gelation temperature was 60°C, a slurry containing copper, zinc and aluminum was obtained, the obtained slurry was aged, the aging temperature was 80°C, one part of the sodium meta-aluminate solution was added first during the aging, the pH value was controlled to be 13.0, the aging time was 0.15 hours, then the aging pH value was controlled to be 8.7, the aging time was 0.15 hours, then the pH value was controlled to be 5.0, the aging time was 0.15 hours, the above operation process was repeated 5 times, and the aging was ended. The aged slurry was filtered, the filter cake was dried at 90°C for 10 hours, an appropriate amount of graphite and water were added for rolling and pressing, and the catalyst was formed by tabletting. The dried formed material was calcined at 360°C for 3 hours to obtain the catalyst A. The composition, pore distribution and main properties are shown in Table 1. Example 2

[0036] Cu(NO3)2-3H2O and Zn(NO3)2-6H2O were dissolved in deionized water to form a Cu and Zn containing solution. AlCl3-6H2O was dissolved in deionized water to form an aluminum containing solution, which was divided into six equal parts by volume. The sodium metaaluminate solution contained 33% of the total Al in the copper zinc catalyst as Al2O3, and was divided into six equal parts by volume. The Cu and Zn containing solution was added to a reactor vessel, and the sodium carbonate solution was added dropwise to the reactor vessel to control the pH at 4.5. The final pH at the end of the process was adjusted to 9.0 by six pH increases of 0.9 each, and the adjusted slurry pH was held constant for 15 minutes. At the same time as each pH increase, one part of the aluminum containing solution was added. The temperature of the gelation was 52°C, and a copper, zinc, and aluminum containing slurry was obtained. The slurry was aged at 85°C. The pH was first adjusted to 12.8 by adding one part of the sodium metaaluminate solution, and the pH was held constant for 0.1 hours. The pH was then adjusted to 9.0 for 0.15 hours, and then to 5.2 for 0.10 hours. The process was repeated six times, and the aging was completed. The aged slurry was filtered, and the filter cake was dried at 90°C for 12 hours. The dried material was tabletted by adding graphite and water. The tablets were calcined at 340°C for 4 hours to form catalyst B. The composition, pore distribution, and major properties are shown in Table 1. Example 3

[0037] Cu(NO3)2-3H2O and Zn(NO3)2-6H2O were dissolved in deionized water to form a Cu and Zn containing solution. AlCl3-6H2O was dissolved in deionized water to form an aluminum containing solution, which was divided into 5 equal parts by volume. The sodium metaaluminate solution contained 28% of the total Al in the copper zinc catalyst as Al2O3, and was divided into 4 equal parts by volume. The Cu and Zn containing solution was added to a reactor vessel, and the sodium carbonate solution was added dropwise to the reactor vessel to control the pH at 5.1. The final pH at the end of the process was adjusted to 8.6 by 5 pH increases of 0.7 each, and the adjusted slurry pH was held constant for 12 minutes. At the same time as each pH increase, one part of the aluminum containing solution was added. The temperature of the gelation was 65°C, and a copper, zinc, and aluminum containing slurry was obtained. The slurry was aged at a temperature of 82°C. The pH was first adjusted to 13.3 by adding one part of the sodium metaaluminate solution, and the pH was held constant for 0.15 hours. The pH was then adjusted to 9.4 for 0.15 hours, and then to 5.6 for 0.15 hours. The process was repeated 4 times, and the aging was completed. The aged slurry was filtered, and the filter cake was dried at 100°C for 10 hours. The dried material was tabletted by adding an appropriate amount of graphite and water. The tabletted material was calcined at 360°C for 3 hours to form catalyst C. The composition, pore distribution, and main properties are shown in Table 1. Example 4

[0038] Cu(NO3)2-3H2O and Zn(NO3)2-6H2O were dissolved in deionized water to prepare a Cu and Zn containing solution. AlCl3-6H2O was dissolved in deionized water to prepare an aluminum containing solution, which was divided into 5 equal parts by volume. The sodium metaaluminate solution contained 38% of the total Al in the copper zinc catalyst as Al2O3 and was divided into 6 equal parts by volume. The Cu and Zn containing solution was added to the reactor, and the sodium carbonate solution was added dropwise to the reactor to control the pH at 5.2. The final pH was adjusted to 9.2 at the end of the reaction by increasing the pH in 5 steps of 0.8 each. The adjusted slurry pH was held constant for 14 minutes. At the same time as each pH increase, one part of the aluminum containing solution was added. The gelation temperature was 68°C, and a copper, zinc, and aluminum containing slurry was obtained. The slurry was aged at 76°C. The pH was controlled at 12.6 for 0.2 hours, then at 9.8 for 0.15 hours, then at 5.8 for 0.10 hours. The process was repeated 6 times, and the aging was completed. The aged slurry was filtered, and the filter cake was dried at 80°C for 12 hours. The dried material was tabletted by adding graphite and water and pressing. The tabletted material was calcined at 350°C for 4 hours to obtain catalyst D. The composition, pore distribution, and main properties are shown in Table 1.

[0039] Comparative Example 1

[0040] Reference agent E was prepared as in Example 1. The Cu, Zn, and Al containing solution and the precipitant were prepared and the reaction was carried out at a fixed pH. The reaction was carried out as follows:

[0041] Cu(NO3)2-3H2O, AlCl3-6H2O, and Zn(NO3)2-6H2O were dissolved in deionized water to prepare a Cu, Zn, and Al containing solution. The Cu 2+ concentration was 3.8 mol / L, and the Zn 2+The concentration of the sodium aluminate solution is 3.2 mol / L, and the weight concentration of Al as Al2O3 is 30.8 g / L. The Al in the sodium aluminate solution accounts for 30% of the total Al in the copper-zinc catalyst obtained as Al2O3. The Al-containing solution is equally divided into 5 portions by volume. The Cu- and Zn-containing solution is added into the reaction tank, and the sodium carbonate solution is added dropwise into the reaction tank. The gelation temperature is 60°C, the gelation time is 1 hour, the reaction pH value is 7.6, and the copper-zinc-aluminum-containing slurry is obtained. The obtained slurry is aged. The aging temperature is 80°C. The pH value is controlled at 13.0 when the first portion of the sodium aluminate solution is added. The aging time is 0.15 hour. The pH value is controlled at 8.7 after the aging time of 0.15 hour. The pH value is controlled at 5.0 after the aging time of 0.15 hour. The above operation process is repeated 5 times, and the aging is ended. The aged slurry is filtered. The filter cake is dried at 90°C for 10 hours. An appropriate amount of graphite and water are added for rolling and pressing, and the tablet is formed. The dried formed product is calcined at 360°C for 3 hours, and the catalyst E is obtained. The composition, pore distribution and main properties are shown in Table 1.

[0042] Comparative Example 2

[0043] The reference agent F is prepared according to Example 1, except that the total sodium aluminate solution is added at one time during the aging process, and a fixed value is used for the aging pH value. The specific preparation process is as follows:

[0044] Cu(NO3)2·3H2O and Zn(NO3)2·6H2O are dissolved in deionized water to prepare a Cu- and Zn-containing solution. AlCl3·6H2O is dissolved in deionized water to prepare an Al-containing solution. The weight concentration of Al as Al2O3 in the Al-containing solution is 30.8 g / L. The Al-containing solution is equally divided into 5 portions by volume. The Al in the sodium aluminate solution accounts for 30% of the total Al in the copper-zinc catalyst obtained as Al2O3. The Cu- and Zn-containing solution is added into the reaction tank, and the sodium carbonate solution is added dropwise into the reaction tank. The pH value is controlled at 4.8. The final pH value is adjusted to 8.8 by 5 times of pH value increase. The pH value is increased by 0.8 each time. The adjusted reaction slurry pH value is constant for 10 minutes. When the pH value is increased each time, one portion of the Al-containing solution is added. The gelation temperature is 60°C, and the copper-zinc-aluminum-containing slurry is obtained. The obtained slurry is aged. The aging temperature is 80°C. The total sodium aluminate solution is added during the aging process. The aging temperature is 80°C. The pH value is 7.6. The aging time is 2.5 hours, and the aging is ended. The aged slurry is filtered. The filter cake is dried at 90°C for 10 hours. An appropriate amount of graphite and water are added for rolling and pressing, and the tablet is formed. The dried formed product is calcined at 360°C for 3 hours, and the catalyst F is obtained. The composition, pore distribution and main properties are shown in Table 1. Example 5

[0045] The methanol synthesis catalyst was crushed to 16-40 mesh, and reduced with a hydrogen-nitrogen mixture (H2 / N2=3 / 97 (volume ratio)) for 16-25 hours before use, at a maximum reduction temperature of 235°C. The activity of the catalyst was evaluated in a micro fixed bed reactor. The catalyst was loaded in an amount of 5 ml, the feed gas composition was CO / H2 / CO2 / N2=13 / 70 / 6 / 11 (volume ratio), the reaction pressure was 5.0 MPa, the space velocity was 10000 h -1 -1, the reaction temperature was 242°C, and the conversion of CO and CO2 was determined as the initial activity of the catalyst. Then the catalyst was heat treated in a synthesis gas atmosphere at 445°C for 5 hours, and then reduced to 250°C to determine the conversion of CO and CO2 as the activity after heat treatment, i.e. the heat resistance. The products were analyzed by gas chromatography, and the time-space yield of methanol g·ml -1 ·h -1 was determined, i.e. the grams of methanol produced per hour per milliliter of catalyst, and the results are shown in Table 5.

[0046] As can be seen from Tables 1-4, the catalyst of the present application has a high density of active component copper oxide in the surface phase and good dispersion of the metal, and a small particle size of the copper, thereby improving the synergistic effect between the Cu and ZnO of the catalyst, and the particle size of the copper is mainly concentrated in the range of 7-10 nm, and the catalyst has high activity and selectivity. As can be seen from the test results in Table 5, the methanol synthesis catalyst of the present application has high activity, heat resistance and excellent selectivity.

[0047] Table 1 Catalyst composition and properties

[0048] Catalyst No. A B C D E F CuO, wt% 55 48 52 58 55 55 ZnO, wt% 23 25 23 22 23 23 Al203, wt% 22 27 25 20 22 15 Specific surface area / m 2 ·g -1 ]]> 258 249 263 269 197 201 Pore volume / cm 3 ·g -1 ]]> 0.481 0.473 0.492 0.499 0.382 0.395 Pore distribution, % < 10 nm 6.94 8.68 5.88 5.32 20.56 19.45 10 nm - 15 nm 39.65 38.82 40.05 40.31 35.23 35.90 > 15 nm 53.41 52.50 54.07 54.37 44.21 44.65

[0049] Table 2 Average particle size and particle size distribution of the copper metal obtained in each example

[0050] Catalyst No. A B C D E F Metallic copper particle average particle size, nm 8.6 8.4 8.8 9.0 16.6 20.7 Metallic copper particle size distribution, % Particle size < 7 nm 8.92 9.23 8.60 8.37 23.41 20.38 Particle size 7 nm - 10 nm 78.32 78.92 77.84 77.41 34.31 28.87 Particle size > 10 nm 12.76 11.85 13.56 14.22 42.28 50.75

[0051] Table 3 Dispersion of the copper metal in the surface phase of the catalyst and specific surface area of the copper in the catalyst

[0052] Catalyst S Cu / m 2 ·g -1 ]]> D Cu ,% A 90.1 41.1 B 89.3 40.2 C 92.2 42.6 D 93.4 43.9 E 53.5 23.9 F 55.3 20.1

[0053] S Cu is the specific surface area of the copper, D Cu is the dispersion of the copper

[0054] Table 4 Weight ratio of the active metal oxides in the surface phase of the catalyst to the active metal oxides in the bulk phase of the catalyst

[0055] Catalyst No. A B C D E F Table phase I Cu Bulk phase I Cu ]]> 5.23 5.35 5.51 5.42 2.62 2.44 Table phase I Zn Bulk phase I Zn ]]> 3.88 3.95 4.06 4.21 1.85 1.71

[0056] Table 5 Test results of the activity evaluation and heat resistance of the catalyst

[0057] Catalyst Initial activity, % Initial activity, % Activity after heat resistance, % Activity after heat resistance, % Methanol space time yield, (g mL -1 ·h -1 )]]> Methanol selectivity, % CO CO2 CO CO2 A 97.89 89.92 90.77 81.88 5.76 98.74 B 97.82 89.87 90.61 81.71 5.68 98.68 C 97.96 89.95 90.75 81.91 5.89 98.82 D 98.05 89.99 90.81 81.98 5.95 98.88 E 89.19 84.87 84.57 76.22 3.08 89.34 F 88.67 84.01 83.85 75.54 2.88 88.10

Claims

1. A method for preparing a copper-zinc catalyst, characterized in that... The following are included: (1) Adding an alkaline precipitant to a solution containing Cu and Zn to carry out a gelation reaction. During the reaction, when the pH value reaches the initial value, the pH value is increased n times until the endpoint value is reached. During each increase, 1 / n volume of Al-containing solution is added. After each increase, the pH value is kept constant for a period of time. After the gelation is completed, a slurry containing Cu, Zn, and Al is obtained. Where n is an integer between 2 and 8. The initial pH value of step (1) is 4.0 to 6.0, and the endpoint value is 8.0 to 10.

5. After each increase in pH value in step (1), the pH value is kept constant for 0.1 to 0.5 hours. The pH increase range is equal to or less than the previous pH increase range. (2) The slurry containing Cu, Zn, and Al obtained in step (1) is subjected to m three-stage decreases. pH aging, the material obtained after aging is subjected to solid-liquid separation, the solid phase is dried and pressed into tablets to obtain the molded product, washed, dried and calcined to obtain the copper-zinc catalyst; where m is an integer between 2 and 8; the specific process of the three-stage decreasing pH aging in step (2) is as follows: the aging temperature of each stage is 60 to 98℃; the first stage, 1 / m sodium aluminate solution is added to the reaction slurry to adjust the pH value to 11.5 to 13.5, and the aging time is 0.05 to 0.5 hours; the second stage, the pH value is adjusted to 8.0 to 10.0, and the aging time is 0.05 to 0.5 hours; the third stage, the pH value is adjusted to 4.0 to 6.5, and the aging time is 0.05 to 0.5 hours; before the next three-stage decreasing pH aging, the pH value is adjusted back to 11.5 to 13.

5.

2. The method according to claim 1, characterized in that: In the Cu and Zn-containing solution described in step (1), the concentration of soluble copper salt is expressed as Cu 2+ The concentration is calculated to be 0.5–6.5 mol / L, with the soluble zinc salt concentration expressed as Zn. 2+ The concentration is calculated to be 0.3–4.5 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; the weight concentration of Al in the Al-containing solution, calculated as Al2O3, is 5–90 g / L.

3. The method according to claim 1, characterized in that: The alkaline precipitant mentioned in step (1) is selected from one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, potassium carbonate or potassium bicarbonate aqueous solution, and the concentration of the alkaline precipitant aqueous solution is 5wt%~25wt%.

4. The method according to claim 1, characterized in that: The gelation reaction conditions for step (1) are: reaction temperature of 30~90℃ and reaction time of 0.5~6.0 hours.

5. The method according to claim 1, characterized in that: The initial pH value in step (1) is 4.2~5.8, and the final pH value is 8.2~10.

3.

6. The method according to claim 1, characterized in that: The sodium aluminate solution mentioned in step (2) has an Al weight concentration of 5 to 70 g / L, calculated as Al2O3.

7. The method according to claim 1, characterized in that: In step (2), the Al added through sodium aluminate solution accounts for 5% to 55% of the total Al in the obtained copper-zinc catalyst, calculated as Al2O3.

8. A copper-zinc catalyst prepared by the method according to any one of claims 1 to 7, characterized in that: Based on the weight of the catalyst, it includes the following components: CuO 25%–72%, ZnO 10%–40%, and Al2O3 10%–38%; wherein the weight ratio of the active metal component CuO in the surface phase to the active metal component CuO in the bulk phase is 2.5:1 to 7.5:1, and the weight ratio of the active metal component ZnO in the surface phase to the active metal component ZnO in the bulk phase is 1.8:1 to 6.5:

1.

9. The catalyst according to claim 8, characterized in that: The specific surface area of ​​metallic copper in the reduced catalyst is 50–150 m². 2 / g, the dispersion of metallic copper in the catalyst surface phase is 26%~58%, and the average particle size of metallic copper is 7~10nm; the particle size distribution of metallic copper particles is as follows: particles with a diameter less than 7nm account for 3%~12% of the total number of particles, particles with a diameter of 7nm~10nm account for 65%~89% of the total number of particles, particles with a diameter greater than 10nm account for 5%~18% of the total number of particles, and the sum of the number of particles of each size accounts for 100% of the total number of particles.

10. The catalyst according to claim 8, characterized in that: The specific surface area of ​​copper-zinc catalysts is 120–550 m². 2 / g, with a pore volume of 0.30~0.90mL / g, and the pore size distribution is as follows: pores smaller than 10nm account for 2%~13% of the total pore volume, pores between 10 and 15nm account for 30%~50% of the total pore volume, and pores larger than 15nm account for 40%~68% of the total pore volume.

11. The application of a copper-zinc catalyst prepared by any one of claims 1 to 7 in the synthesis of methanol, wherein the process conditions are: reaction temperature 210–320 °C, pressure 2.0–10 MPa, and volume hourly space velocity 2000–15000 h⁻¹. -1 .