Catalyst for hydrogenation of methyl acetate as well as preparation method and application of catalyst

Abstract

The invention relates to a catalyst for hydrogenation of methyl acetate as well as a preparation method and application of the catalyst. The catalyst for hydrogenation of methyl acetate comprises a carrier, an active component and a metal oxide aid, the carrier and the active component are copper-manganese-aluminum composite oxides, and the copper-manganese-aluminum composite oxides comprise the following components in percentage by mass: 40%-60% of CuO, 5%-15% of Mn2O3 and 20%-40% of Al2O3; the mass ratio of the metal in the metal oxide auxiliary agent to the carrier and the active component is 1-8%; the metal in the metal oxide auxiliary agent is one or more of Mg, Ce, Zr and Ca, and the catalyst has the advantages of high activity, small hydrogen circulation amount, few byproducts, low production energy consumption, low separation energy consumption, long-term stability in use and long service life under the reaction conditions of low reaction temperature, high liquid hourly space velocity and low hydrogen ester molar ratio.

Description

Technical Field

[0001] This invention relates to the field of ethanol preparation technology, specifically to a catalyst for the hydrogenation of methyl acetate, its preparation method, and its application. Background Technology

[0002] Ethanol, commonly known as alcohol, can be produced in many ways. One method involves the hydrogenation of acetic acid / acetic acid esters from syngas. This involves the carbonylation of syngas with methanol to obtain acetic acid / acetic acid esters, which are then further hydrogenated to yield ethanol. While the direct hydrogenation of acetic acid to ethanol has a shorter process flow, acetic acid is corrosive to the equipment, requiring specialized materials. Furthermore, the reaction uses a precious metal catalyst, the reaction products are complex, and separation energy consumption is high, significantly increasing production costs. The indirect hydrogenation of acetic acid involves esterifying acetic acid to produce the corresponding acetate ester, which is then catalytically hydrogenated to produce ethanol. Compared to the direct hydrogenation of acetic acid to ethanol, this method has less corrosiveness of the reactants and products, requires less equipment investment, uses copper-based catalysts, achieves high product yields, has low separation energy consumption, and significantly reduces production costs. Copper-based catalysts offer many advantages, such as high reactivity, high design flexibility, and relatively low cost. Most importantly, the active component Cu exhibits high hydrogenation activity towards C=O bonds while being relatively inactive towards C=C bonds, making it widely used in ester hydrogenation research.

[0003] Patent CN105749913A discloses a supported CuOx-MOy / SiO2 catalyst for the hydrogenation of ester compounds. Under conditions of reaction temperature below 250℃, 1.0 MPa, and a hydrogen-ester molar ratio of 30, the conversion rate of methyl acetate is greater than 95%, the selectivity of ethanol is greater than 95%, and no catalyst deactivation was observed within 100 hours of reaction. Although this catalyst has a low reaction pressure, the conversion rate is relatively low at high temperatures, the selectivity of the byproduct ethyl acetate is high, and the lifespan is short. Patent CN116673037B discloses a supported CuZnAl-M / C catalyst for the hydrogenation of methyl acetate. Under conditions of 150-300℃, 0.8-4.0 MPa, and a liquid hourly space velocity (LISH) of 0.2-1.5 h⁻¹, the catalyst achieves this effect. -1 At a hydrogen-to-ester molar ratio of 2-30, the conversion rate of methyl acetate is greater than 81%, and the selectivity of ethanol is greater than 80%. However, this catalyst exhibits poor activity at low temperatures and poor stability at high temperatures, showing significant deactivation after 1000 hours of reaction. Furthermore, the support is primarily carbon nanotubes, resulting in high catalyst manufacturing costs. Patent CN115845869B discloses a metal-doped copper-zinc-aluminum catalyst that achieves a maximum conversion rate of 99.3% and a maximum selectivity of 99.2% at 180℃, 3.0 MPa, a liquid hourly space velocity of 1.5 h⁻¹, and a hydrogen-to-ester molar ratio of 80. While this catalyst achieves high conversion at low temperatures, the high hydrogen-to-ester molar ratio leads to high energy consumption in production. Therefore, there is an urgent need to develop a catalyst that addresses the problems of low methyl acetate conversion rate, high hydrogen-to-ester ratio, high energy consumption, and poor stability at low temperatures. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a catalyst for the hydrogenation of methyl acetate with high activity and long lifespan suitable for low temperature and low hydrogen-to-ethanol ratio, as well as its preparation method and application.

[0005] The technical solution adopted by the present invention to solve the above problems is as follows: On one hand, the present invention provides a catalyst for the hydrogenation of methyl acetate, the catalyst comprising a support, an active component, and a metal oxide auxiliary; the support and the active component are copper-manganese-aluminum composite oxides, which, by mass percentage, comprise 40%~60% CuO, 5%~15% Mn2O3, and 20%~40% Al2O3; the mass ratio of the metal in the metal oxide auxiliary to the support and the active component is 1-8%; the metal in the metal oxide auxiliary is one or more of Mg, Ce, Zr, and Ca.

[0006] Among them, copper-manganese-aluminum composite oxides serve as both a carrier and an active component.

[0007] The catalyst for the hydrogenation of methyl acetate of the present invention is suitable for use at a low reaction temperature of 160-180°C, a reaction pressure of 3.0-5.0 MPa, and a liquid hourly space velocity of 1.5 h⁻¹ for high methyl acetate solutions. -1 The catalyst exhibits high catalytic activity under conditions of a low hydrogen-ester molar ratio of 10-15, with a methyl acetate conversion rate ≥99%, ethanol selectivity ≥99.5%, low hydrogen circulation, few byproducts, low production energy consumption, and low separation energy consumption. It maintains high stability even after 3024 hours of use at a reaction temperature of 180℃. The methyl acetate hydrogenation catalyst of this invention will not cause environmental pollution and is a green and environmentally friendly catalyst.

[0008] On the other hand, the present invention provides a method for preparing the above-mentioned catalyst for hydrogenation of methyl acetate, the preparation method comprising the following steps: (a) Prepare a mixed aqueous solution of copper source, manganese source and aluminum source, denoted as solution 1; (b) Prepare an aqueous solution of the precipitant, denoted as solution 2; (c) Under stirring conditions, solutions 1 and 2 were added dropwise to a precipitation tank in parallel flow to carry out a co-precipitation reaction. After precipitation, the mixture was aged to obtain the reaction mixture. (d) The reaction mixture is subjected to vacuum filtration and thoroughly washed with deionized water during the filtration process to obtain a slurry, which is then dried to obtain the precursor; (e) The precursor is ground into powder, the powder is mixed with graphite and extruded into particles, and then calcined to obtain the carrier and active component; the amount of graphite added is 1-5% of the powder mass; (f) Prepare the precursor solution of the metal oxide additive by impregnation, adding the precursor solution of the metal oxide additive dropwise onto the support and active component, and then dehydrating, drying and calcining in a water bath to obtain the catalyst.

[0009] The graphite added in step (e) has good lubricating properties, which can effectively reduce mold wear and improve extrusion molding efficiency. The amount of graphite added is set to ensure that the graphite is completely burned off during the subsequent calcination process. The purpose of water bath stirring and dehydration in step (f) is to evaporate most of the moisture in the sample and prevent sample clumping caused by direct drying in the oven.

[0010] In the above preparation method of the present invention, the carrier and active component are prepared by co-precipitation method, and the metal oxide additive is adsorbed into the carrier and active component by impregnation method, which is a simple preparation method.

[0011] Further, in step (a), the mixed aqueous solution is obtained by dissolving copper nitrate trihydrate, manganese nitrate tetrahydrate or manganese nitrate solution, and aluminum nitrate nonahydrate in deionized water at room temperature.

[0012] The manganese nitrate solution has a mass concentration of 50%, but is not limited to this.

[0013] Further, in step (b), the precipitant is at least one of sodium hydroxide and sodium carbonate.

[0014] Further, in step (c), the precipitation temperature of the coprecipitation reaction is 20-40℃, the precipitation time is 30-120 min, the final pH value of the reaction system is controlled to be 7.0-8.0, and the aging time is 1-6 h.

[0015] Further, in step (d), the filtrate is washed with deionized water until the conductivity of the filtrate is 100-1000 μS / cm during the filtration process; the drying is carried out at 100-120℃ for 8-12 hours.

[0016] Further, in step (e), the particles are cylindrical particles with a diameter of φ3×3mm, and the calcination is carried out in an air atmosphere at 400-600℃ for 2-6 hours.

[0017] Further, in step (f), the precursor of the metal oxide auxiliary is one of nitrate, acetate, and sulfate.

[0018] Further, in step (f), the water bath stirring dehydration is carried out by heating and stirring in a water bath at 60-100℃ for 4-10 hours, the drying is carried out by drying at 120℃ for 8-12 hours, and the calcination is carried out by calcination at 400-600℃ for 2-6 hours.

[0019] In another aspect, the present invention provides the application of the above-mentioned catalyst for the hydrogenation of methyl acetate in the hydrogenation of methyl acetate to ethanol.

[0020] The present invention has the following beneficial effects: The catalyst for the hydrogenation of methyl acetate provided by this invention operates at a low reaction temperature of 160-180℃, a reaction pressure of 3.0-5.0 MPa, and a liquid hourly space velocity of 1.5 h⁻¹ for high methyl acetate. -1 The catalyst exhibits high catalytic activity under low hydrogen-ester molar ratio conditions of 10-15, with a methyl acetate conversion rate ≥99%, ethanol selectivity ≥99.5%, low hydrogen recycling volume, few byproducts, low production energy consumption, and low separation energy consumption. It maintains high stability even after 3024 hours of use at a reaction temperature of 180℃. This catalyst for the hydrogenation of methyl acetate does not pollute the environment and is considered a green and environmentally friendly catalyst. The preparation method of this invention is simple to operate and suitable for mass production. Attached Figure Description

[0021] Figure 1 This is a graph showing the stability test data of catalyst A prepared in Example 1 of this invention for 3024 hours after hydrogenation of methyl acetate. Detailed Implementation

[0022] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to specific examples. However, the scope of protection of this invention is not limited to the following specific embodiments. The described embodiments are merely some, not all, of the embodiments of this invention, and are not intended to limit the invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0023] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0024] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0025] This invention relates to catalysts for the hydrogenation of methyl acetate and their preparation methods, and includes Examples 1-9, as well as Comparative Example 1. Example 1

[0026] Based on the Cu:Mn:Al atomic molar ratio of 1:0.17:0.78, copper nitrate trihydrate, 50% manganese nitrate solution, and aluminum nitrate nonahydrate were weighed and placed in a beaker. Deionized water was added to the beaker and stirred until well mixed to prepare a mixed aqueous solution with a total metal content of 2 mol / L, denoted as solution 1. 200 g of sodium carbonate was weighed and placed in a beaker. Deionized water was added to the beaker and stirred until well mixed to prepare a 1 mol / L solution, denoted as solution 2. Under continuous stirring, solutions 1 and 2 were added dropwise to a precipitation tank in parallel using a peristaltic pump. The flow rate of solution 2 was adjusted to control the system during the reaction. The pH value was 7.5, the precipitation temperature was 30℃, the precipitation time was 30 min, and the mixture was aged at room temperature for 4 h to obtain the reaction mixture. The reaction mixture was filtered and washed with deionized water until the conductivity of the filtrate was 500 μS / cm. After drying at 120℃ for 10 h, the precursor was obtained and then ground into powder. The powder was mixed with 3% graphite by weight and extruded into cylindrical particles of φ3×3mm. The particles were calcined in air at 500℃ for 4 h to obtain a 60%CuO-10%Mn2O3-30%Al2O3 copper-manganese-aluminum composite oxide. Take 10g of the prepared 60%CuO-10%Mn2O3-30%Al2O3 copper-manganese-aluminum composite oxide, weigh magnesium nitrate hexahydrate with a Mg loading of 8%, and dissolve it in an equal amount of deionized water. Add the dissolved solution dropwise and evenly onto the 60%CuO-10%Mn2O3-30%Al2O3 copper-manganese-aluminum composite oxide. Then, heat and stir it in an 80℃ water bath for 8 hours, dry it at 120℃ for 10 hours, and then calcine it at 500℃ for 4 hours to obtain catalyst A.

[0027] The prepared catalyst A was loaded into a tubular reactor with an inner diameter of 10 mm. The catalyst bed was filled with ceramic balls at both ends and reduced at 250 °C under a pure hydrogen atmosphere for 12 h. Methyl acetate was used as the raw material, with a reaction temperature of 180 °C, a reaction pressure of 4.0 MPa, a hydrogen-to-ester molar ratio of 15, and a methyl acetate liquid hourly space velocity of 1.5 h⁻¹. -1 The generated liquid products were collected every 4 hours after condensation. The hydrogenation products were analyzed by gas chromatography using the corrected area normalization method, and the conversion rate of methyl acetate and the selectivity of ethanol were obtained. The results are shown in Table 1.

[0028] In addition, by Figure 1 It can be seen that after 3024 hours of continuous reaction, catalyst A showed excellent stability with a methyl acetate conversion rate of ≥99.0% and an ethanol selectivity of ≥99.0%. Example 2

[0029] In this embodiment, cerium nitrate hexahydrate was used instead of magnesium nitrate hexahydrate in Example 1, and the other steps were the same as in Example 1, resulting in catalyst B. The reaction process conditions were the same as in Example 1, and the results are shown in Table 1. Example 3

[0030] In this embodiment, zirconium nitrate pentahydrate was used instead of magnesium nitrate hexahydrate in Example 1, and the other steps were the same as in Example 1, resulting in catalyst C. The reaction process conditions were the same as in Example 1, and the results are shown in Table 1. Example 4

[0031] In this embodiment, sodium hydroxide was used instead of sodium carbonate in Example 1 as the precipitant, and the other steps were the same as in Example 1, yielding catalyst D. The reaction process conditions were the same as in Example 1, and the results are shown in Table 1. Example 5

[0032] In this embodiment, the Mg loading was changed to 4%, and the other steps were the same as in Example 1, resulting in catalyst E. The reaction process conditions were the same as in Example 1, and the results are shown in Table 1. Example 6

[0033] Based on the Cu:Mn:Al atomic molar ratio of 1:0.34:1.39, copper nitrate trihydrate, 50% manganese nitrate solution, and aluminum nitrate nonahydrate were weighed and placed in a beaker. Deionized water was added to the beaker and the mixture was stirred until homogeneous, preparing a mixed solution with a total metal content of 2 mol / L, denoted as solution 1. 200 g of sodium carbonate was weighed and placed in a beaker. Deionized water was added to the beaker and the mixture was stirred until homogeneous, preparing a 1 mol / L solution, denoted as solution 2. Under continuous stirring, solutions 1 and 2 were added dropwise to a precipitation tank using a peristaltic pump, with the flow rate of solution 2 adjusted to control the reaction process. The pH value was 7.5, the precipitation temperature was 30℃, the precipitation time was 30 min, and the mixture was aged at room temperature for 4 h to obtain the reaction mixture. The reaction mixture was filtered and washed with deionized water until the conductivity of the filtrate was 500 μS / cm. After drying at 120℃ for 10 h, the precursor was obtained and then ground into powder. The powder was mixed with 3% graphite by weight and extruded into cylindrical particles of φ3×3mm. The particles were calcined in air at 500℃ for 4 h to obtain a 45%CuO-15%Mn2O3-40%Al2O3 copper-manganese-aluminum composite oxide. Take 10g of the prepared 45%CuO-15%Mn2O3-40%Al2O3 copper-manganese-aluminum composite oxide, weigh magnesium nitrate hexahydrate with a Mg loading of 8%, and dissolve it in an equal amount of deionized water. Add the dissolved solution dropwise and evenly onto the 45%CuO-15%Mn2O3-40%Al2O3 copper-manganese-aluminum composite oxide. Then, heat and stir in a water bath at 80℃ for 8 hours, dry at 120℃ for 10 hours, and calcine at 500℃ for 4 hours to obtain catalyst F. The reaction process conditions are the same as in Example 1, and the results are shown in Table 1. Example 7

[0034] Catalyst A prepared in Example 1 was loaded into a tubular reactor with an inner diameter of 10 mm. The catalyst bed was filled with ceramic balls at both ends and reduced at 250°C under a pure hydrogen atmosphere for 12 h. Methyl acetate was used as the raw material, the reaction temperature was 200°C, the reaction pressure was 4.0 MPa, the hydrogen-ester molar ratio was 10, and the methyl acetate liquid hourly space velocity was 2.0 h⁻¹. -1 The generated liquid products were collected every 4 hours after condensation. The hydrogenation products were analyzed by gas chromatography using the corrected area normalization method, and the conversion rate of methyl acetate and the selectivity of ethanol were obtained. The results are shown in Table 1. Example 8

[0035] Catalyst A prepared in Example 1 was loaded into a tubular reactor with an inner diameter of 10 mm. The catalyst bed was filled with ceramic balls at both ends and reduced at 250°C under a pure hydrogen atmosphere for 12 h. Methyl acetate was used as the raw material, the reaction temperature was 250°C, the reaction pressure was 2.0 MPa, the hydrogen-to-ester molar ratio was 30, and the liquid hourly space velocity (LISH) of sec-butyl acetate was 3.0 h⁻¹. -1 The generated liquid products were collected every 4 hours after condensation. The hydrogenation products were analyzed by gas chromatography using the corrected area normalization method, and the conversion rate of methyl acetate and the selectivity of ethanol were obtained. The results are shown in Table 1. Example 9

[0036] Catalyst A prepared in Example 1 was loaded into a tubular reactor with an inner diameter of 10 mm. The catalyst bed was filled with ceramic balls at both ends and reduced at 250°C under a pure hydrogen atmosphere for 12 h. Methyl acetate was used as the raw material, the reaction temperature was 150°C, the reaction pressure was 8.0 MPa, the hydrogen-to-ester molar ratio was 30, and the liquid hourly space velocity (LISH) of methyl acetate was 0.4 h⁻¹. -1 The generated liquid products were collected every 4 hours after condensation. The hydrogenation products were analyzed by gas chromatography using the corrected area normalization method, and the conversion rate of methyl acetate and the selectivity of ethanol were obtained. The results are shown in Table 1. Comparative Example 1

[0037] A 45% CuO-15% Mn2O3-40% Al2O3 copper-manganese-aluminum composite oxide was prepared as catalyst F according to the method in Example 1, without any metal oxide additives. The reaction process conditions were the same as in Example 1, and the results are shown in Table 1.

[0038] Table 1. Reaction conditions and results of hydrogenation of methyl acetate to ethanol

[0039] Note: Hydrogenation of one molecule of methyl acetate produces one molecule of ethanol and one molecule of methanol. Therefore, the methanol selectivity is almost equal to the ethanol selectivity in Table 1.

[0040] As shown in Table 1, the conversion rate and selectivity of the catalyst for hydrogenation of methyl acetate in the embodiments of the present invention are significantly higher than those in Comparative Example 1, indicating that the catalyst of the present invention has significant advantages in the catalytic hydrogenation of methyl acetate to ethanol.

[0041] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0042] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0043] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A catalyst for the hydrogenation of methyl acetate, characterized in that, The catalyst includes a support, an active component, and a metal oxide auxiliary; the support and active component are copper-manganese-aluminum composite oxides, which, by mass percentage, comprise 40%~60% CuO, 5%~15% Mn2O3, and 20%~40% Al2O3; the mass ratio of the metal in the metal oxide auxiliary to the support and active component is 1-8%; the metal in the metal oxide auxiliary is one or more of Mg, Ce, Zr, and Ca.

2. A method for preparing a catalyst for the hydrogenation of methyl acetate as described in claim 1, characterized in that, The preparation method includes the following steps: (a) Prepare a mixed aqueous solution of copper source, manganese source and aluminum source, denoted as solution 1; (b) Prepare an aqueous solution of the precipitant, denoted as solution 2; (c) Under stirring conditions, solutions 1 and 2 were added dropwise to a precipitation tank in parallel flow to carry out a co-precipitation reaction. After precipitation, the mixture was aged to obtain the reaction mixture. (d) The reaction mixture is subjected to vacuum filtration and thoroughly washed with deionized water during the filtration process to obtain a slurry, which is then dried to obtain the precursor; (e) The precursor is ground into powder, the powder is mixed with graphite and extruded into particles, and then calcined to obtain the carrier and active component; the amount of graphite added is 1-5% of the powder mass; (f) Prepare the precursor solution of the metal oxide additive by impregnation, adding the precursor solution of the metal oxide additive dropwise onto the support and active component, and then dehydrating, drying and calcining in a water bath to obtain the catalyst.

3. The preparation method according to claim 2, characterized in that, In step (a), the mixed aqueous solution is obtained by dissolving copper nitrate trihydrate, manganese nitrate tetrahydrate or manganese nitrate solution, and aluminum nitrate nonahydrate in deionized water at room temperature.

4. The preparation method according to claim 2, characterized in that, In step (b), the precipitant is at least one of sodium hydroxide and sodium carbonate.

5. The preparation method according to claim 2, characterized in that, In step (c), the precipitation temperature of the coprecipitation reaction is 20-40℃, the precipitation time is 30min-120min, the final pH value of the reaction system is controlled to be 7.0-8.0, and the aging time is 1-6h.

6. The preparation method according to claim 2, characterized in that, In step (d), the filtration process involves washing with deionized water until the conductivity of the filtrate is 100-1000 μS / cm; the drying process involves drying at 100-120℃ for 8-12 hours.

7. The preparation method according to claim 2, characterized in that, In step (e), the particles are cylindrical particles with a diameter of φ3×3mm, and the calcination is carried out in an air atmosphere at 400-600℃ for 2-6 hours.

8. The preparation method according to claim 2, characterized in that, In step (f), the precursor of the metal oxide auxiliary is one of nitrate, acetate, and sulfate.

9. The preparation method according to claim 2, characterized in that, In step (f), the water bath stirring dehydration is carried out by heating and stirring in a water bath at 60-100℃ for 4-10 hours, the drying is carried out by drying at 120℃ for 8-12 hours, and the calcination is carried out by calcination at 400-600℃ for 2-6 hours.

10. The application of the catalyst for hydrogenation of methyl acetate as described in claim 1 in the hydrogenation of methyl acetate to ethanol.

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