A method for preparing a highly selective copper-based methanol synthesis catalyst

Abstract

This invention relates to a method for preparing a highly selective copper-based methanol synthesis catalyst. The method involves a two-step co-precipitation process to obtain a precursor and a support, followed by mixing the precursor and alumina support into a slurry to obtain a catalyst slurry. The slurry is then dried to obtain a raw catalyst meal. The raw meal is then rolled, granulated, impregnated with additives in equal volumes, dried, calcined, and sheeted to finally obtain the methanol synthesis catalyst. This invention has the advantages of simple preparation method, high activity and selectivity, and easy operation, making it suitable for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of chemical catalyst technology, specifically relating to a method for preparing a highly selective copper-based methanol synthesis catalyst. Background Technology

[0002] Methanol, as an important basic chemical product, can be used to produce acetic acid, MTBE, formaldehyde, dimethyl ether, and low-carbon olefins. However, ethanol impurities in industrial methanol can significantly affect the quality of some chemical products or intermediates (such as acetic acid, formaldehyde, resins, methyl formate, and specialty adhesives) during production. For example, in the process of producing acetic acid by methanol carbonylation, excessive ethanol in the methanol feedstock can lead to the appearance of byproducts. Furthermore, ethanol and methanol have similar physicochemical properties, and the later-stage distillation of crude methanol requires significant energy consumption to meet specifications; the higher the ethanol content, the greater the energy consumption. Therefore, achieving high-quality and high-quantity industrial-scale methanol production has become a major challenge in this research field.

[0003] Catalysts are the core of syngas-to-methanol technology. Excellent catalysts can not only efficiently catalyze methanol production and reduce production costs, but also significantly suppress byproduct formation, saving on methanol post-processing costs. Common methanol synthesis catalysts include copper-based catalysts and noble metal catalysts. Copper-based catalysts, in particular, have good catalytic performance, are inexpensive, and easy to prepare, making them widely used in syngas hydrogenation to methanol. Initially, pure CuO was used as a catalyst, but its activity and stability were unsatisfactory. Researchers subsequently added ZnO to effectively prevent Cu particle sintering and to provide a synergistic effect, improving selectivity and long-term stability for methanol. However, Cu-ZnO binary catalysts suffer from serious problems such as poor thermal stability, extreme sensitivity to toxic and harmful substances, and short lifespan. Based on binary catalysts, researchers have added metal oxide promoters such as Al2O3, MgO, and ZrO2 to form ternary catalysts to address the problems associated with binary catalysts. ZrO2 is a metal oxide that simultaneously possesses acidic, basic, oxidizing, and reducing properties. It is also a P-type semiconductor, which means that it easily generates holes and can interact strongly with the active components, thus facilitating the dispersion of the active components.

[0004] In recent years, methanol producers both domestically and internationally have increasingly stringent requirements for catalysts, particularly regarding the content of fusel oils in crude methanol. With larger-scale plants and higher operating pressures and reaction temperatures, the impurity content in crude methanol products also increases. Therefore, reducing the impurity content of crude methanol products and improving catalyst selectivity has become a crucial issue. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a highly selective copper-based methanol synthesis catalyst. The methanol synthesis catalyst prepared using this method exhibits higher selectivity and lower crude methanol impurity content compared to catalysts prepared by conventional methods.

[0006] The main steps of this invention are as follows: the parent material is obtained by co-precipitation, mixed with a carrier and pulped, then washed, dried, granulated and then additives are added, and finally dried, calcined and shaped to obtain the methanol synthesis catalyst. Detailed Implementation

[0007] The following examples are used to further explain the content of the present invention and are not intended to limit the present invention.

[0008] Example 1

[0009] Prepare a copper-zinc solution A (1 L containing 50 g / L Cu and 25 g / L Zn) by heating it to 70°C. Dissolve 254.4 g of alkaline precipitant Na₂CO₃ in 2 L of deionized water to prepare solution B, and heat it to 70°C. Add solution A to solution B with stirring. Control the temperature during neutralization at 65°C and the final pH value at 6.5. After the mother slurry changes color and ages, allow it to settle naturally several times until the washing water does not turn blue after 10 drops of diphenylamine sulfate are added, thus obtaining the catalyst matrix. Add 10% (by mass) of alumina carrier (based on the total copper and zinc content of the mother slurry) to the above matrix, mix and slurry, then vacuum filter and wash. Dry the filter cake obtained by vacuum filtration at 100°C for 24 hours, then crush and granulate the filter cake, and sieve it to obtain particles with a sieve mesh size of 16-25 mesh, thus obtaining the catalyst raw material. Zirconium nitrate pentahydrate (0.5% of the total copper and zinc content of the precursor) was added to the catalyst raw material via an equal-volume impregnation method. The mixture was then dried at 100°C for 24 hours, followed by calcination at 320°C for 40 minutes, and finally sheeted to form the desired product. Copper-based methanol synthesis catalyst samples.

[0010] Example 2

[0011] 1 L of copper-zinc solution A containing 60 g / L Cu and 20 g / L Zn was heated to 75°C and set aside. 252 g of alkaline precipitant NaHCO3 was dissolved in 3 L of deionized water to prepare solution B, which was also heated to 75°C and set aside. Solution A was added to solution B with stirring. The neutralization process was controlled at 70°C, with the final pH value controlled at 7.0. After the mother slurry changed color and aged, it underwent several natural sedimentation cycles until 10 drops of diphenylamine sulfate added to the washing water did not turn blue, yielding the catalyst matrix. 20% (by mass) of alumina carrier from the total copper and zinc content of the matrix was added to the above matrix. After mixing and pulping, the mixture was vacuum filtered and washed. The resulting filter cake was dried at 110°C for 16 hours, then crushed and granulated, and sieved to obtain particles with a sieve mesh size of 20-35 mesh, yielding the catalyst raw material. Zirconium nitrate pentahydrate (1.0% of the total mass of copper and zinc in the precursor) was added to the catalyst raw material via an equal-volume impregnation method. The mixture was then dried at 110°C for 16 hours, followed by calcination at 350°C for 30 minutes, and finally sheeted to form the desired product. Copper-based methanol synthesis catalyst samples.

[0012] Example 3

[0013] Prepare a copper-zinc solution A (1 L containing 80 g / L Cu and 20 g / L Zn) by heating it to 80°C. Dissolve 268.8 g of alkaline precipitant NaHCO3 in 4 L of deionized water to prepare solution B, and heat it to 80°C. Add solution A to solution B with stirring. Control the temperature during neutralization at 75°C and the final pH value at 7.5. After the mother slurry changes color and ages, allow it to settle naturally several times until the washing water does not turn blue after 10 drops of diphenylamine sulfate are added, thus obtaining the catalyst matrix. Add an alumina carrier (30% of the total mass of copper and zinc contained in the mother slurry) to the above matrix, mix and slurry, then vacuum filter and wash. Dry the filter cake obtained by vacuum filtration at 120°C for 8 hours, then crush and granulate the filter cake, and sieve it to obtain particles with a sieve mesh size of 25-40 mesh, thus obtaining the catalyst raw material. Zirconium nitrate pentahydrate (1.5% of the total copper-zinc content in the precursor) was added to the catalyst raw material via an equal-volume impregnation method. The mixture was then dried at 120°C for 8 hours, followed by calcination at 380°C for 15 minutes, and finally sheeted to form the desired product. Copper-based methanol synthesis catalyst samples.

[0014] Comparative Example 1

[0015] A copper-zinc solution A containing 1 L of Cu: 60 g / L and Zn: 20 g / L was heated to 75°C and set aside. 252 g of NaHCO3 was dissolved in 3 L of deionized water to prepare solution B, which was also heated to 75°C and set aside. Solution A was added to solution B with stirring. The neutralization process was controlled at 70°C, with the final pH value controlled at 7.0. After the mother slurry changed color and aged, it underwent several natural sedimentation cycles until 10 drops of diphenylamine sulfate added to the washing water did not turn blue, yielding the catalyst matrix. An alumina support prepared from sodium hydroxide and aluminum nitrate was added to the above matrix, with the aluminum nitrate amount being 60% of the total mass of copper and zinc in the matrix. After mixing and pulping, the mixture was vacuum filtered and washed. The resulting filter cake was dried at 105°C for 12 hours, then crushed and granulated, and sieved to obtain particles with a sieve mesh size of 20-40 mesh, yielding the catalyst raw material. The catalyst raw material was dried at 120°C for 2 hours, calcined at 350°C for 25 minutes, and finally formed into sheets. Copper-based methanol synthesis catalyst sample.

[0016] Sample testing

[0017] Activity testing: A micro fixed-bed continuous flow reactor was used with small-particle loading. The catalyst loading was 2 mL, with a particle size of 16-40 mesh. Catalyst reduction was performed in a low-hydrogen atmosphere (H2:N2 = 5:95) with a programmed temperature increase (20℃ / h) for 10 hours, reaching a temperature of 230℃. The reducing gas was then switched to the feed gas for activity testing. The activity testing conditions were a reaction pressure of 8.0 MPa and a space velocity of 10000 h⁻¹. -1 The temperature was 230℃, and the composition of the synthesis gas was H2:CO:CO2:N2 = 67:15:4:14 (v / v). After heat treatment at 400℃ for 5 h, the catalyst's activity was measured under the above conditions. The activity value was expressed as the space-time yield of methanol (g·ml). -1 ·h -1 The ratio of activity after heat resistance to initial activity is used to compare the thermal stability of the samples.

[0018] The activity test results are shown in Table 1. Examples 1, 2, and 3 are samples prepared by the method of the present invention, and Comparative Example 1 is a reference sample prepared by a conventional method.

[0019] Table 1. Activity test results

[0020]

[0021] The crude methanol of the above catalyst samples was analyzed by chromatography, and the results are shown in Table 2.

[0022] Table 2. Results of Impurity Content Test

[0023] catalyst Example 1 Example 2 Example 3 Comparative Example 1 Methanol selectivity, % 97.20 97.18 97.16 97.05 Total impurities in crude methanol 3310 3538 3723 4617

[0024] As shown in Table 1, the initial activity and post-heat-resistant activity of the methanol synthesis catalyst prepared by the method of the present invention are comparable to those of the methanol synthesis catalyst prepared by the conventional method. As shown in Table 2, compared with the methanol synthesis catalyst prepared by the conventional method, the total impurity content in crude methanol is significantly reduced and the methanol selectivity is improved.

[0025] The catalyst prepared by the method of the present invention is suitable for methanol production from syngas containing CO, CO2 and H2, and is especially suitable for low-temperature and low-pressure methanol synthesis plants.

Claims

1. A process for the preparation of a high selectivity copper-based catalyst for methanol synthesis, characterized in that The catalyst raw material is obtained by mixing the parent material and the support obtained by co-precipitation, washing, drying and granulation, then adding additives, and finally drying, calcining and molding to obtain the methanol synthesis catalyst.

2. The production method according to claim 1, characterized by The specific preparation steps of its parent compound are as follows: ① Dissolve copper nitrate and zinc nitrate with a Cu / Zn mass ratio of 2:1 to 4:1 in deionized water to prepare mixed solution A, and heat to 70 to 80℃ for later use; ② Dissolve the alkaline precipitant and prepare a solution B with a concentration of 0.8-1.2 mol / L. Heat the solution to 70-80℃ and set aside for use. ③ Add solution A and solution B simultaneously while stirring, with a volume ratio of 1:2 to 1:

4. Control the temperature during the neutralization process at 65 to 75°C and control the final pH value at 6.5 to 7.5 to obtain the mother slurry. ④ The mother slurry obtained in step 3) is allowed to settle naturally several times until 10 drops of diphenylamine sulfate are added to the washing water and it does not turn blue, thus obtaining the catalyst mother slurry.

3. The method of claim 1, wherein The carrier is alumina, and its amount is 10% to 30% of the total mass of copper and zinc in the parent compound.

4. The method of claim 1, wherein The granulation particle size is 0.4mm to 1.2mm.

5. The method of claim 1, wherein The additive is added by impregnating zirconium nitrate pentahydrate into the catalyst raw material using an equal volume method. The amount of additive is 0.5% to 1.5% of the total mass of copper and zinc.

6. The method of claim 1, wherein Drying temperature: 100℃~120℃, drying time: 8h~24h.

7. The method of claim 1, wherein The roasting temperature is 300℃~400℃, and the roasting time is 10min~60min.

8. The method of claim 2, wherein The alkaline precipitant is one or more of sodium carbonate or sodium bicarbonate.

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