A method for preparing acetoin by selective dehydrogenation of 2,3-butanediol catalyzed by a copper-based catalyst

Abstract

The present invention discloses a method for preparing acetoin by selectively dehydrogenating 2,3-butanediol using a copper-based catalyst. The method utilizes a copper-based hydrotalcite catalyst to catalyze the oxygen-free dehydrogenation of 2,3-butanediol in an inert gas atmosphere, thereby highly selectively producing acetoin. The method for preparing the copper-based hydrotalcite catalyst comprises dissolving a copper salt, a reducing agent, a magnesium salt, and an aluminum salt in a solvent, co-precipitating the resultant in the presence of a precipitant, and washing, drying, and calcining the precipitated product to obtain the copper-based hydrotalcite catalyst; the reducing agent is N2H4. The present invention utilizes a low-copper-loaded copper-based hydrotalcite catalyst to catalyze the oxygen-free dehydrogenation of 2,3-butanediol to produce acetoin with high selectivity.

Description

Technical Field

[0001] The invention relates to the technical field of preparing acetoin by selective dehydrogenation of 2,3-butanediol, and particularly to a method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst. Background Art

[0002] Acetoin, also known as 3-hydroxybutanone (acetoin), has a milky aroma and is naturally found in grapes, coffee, corn, and certain animal tissues. Acetoin has a variety of uses, including as a flavor enhancer for coffee, nuts, chocolate, dairy products, and alcoholic beverages. It is also an important tobacco additive to improve tobacco quality. Because 3-hydroxybutanone contains both hydroxyl and carbonyl groups, it also has important applications in pharmaceutical chemistry.

[0003] Currently, the main industrial production methods include microbial fermentation and chemical synthesis. Microbial fermentation offers simple operation and an environmentally friendly production process, but obtaining high-yield strains remains a key technical bottleneck for industrialization. Patent CN111705027B discloses a method for producing acetoin via microbial fermentation. This patented technology utilizes a genetically engineered strain, B. subtilis 6-7ΔacuBΔacoBΔrex, in a 5L fermenter for 96 hours, achieving a yield of 67.5 g / L. -1 Preparation of acetoin, production efficiency increased to 0.7g·L -1 ·h -1 . However, the production of acetoin by biological fermentation still has the problems of low yield and high production cost. Therefore, the large-scale production of acetoin needs to rely on chemical synthesis, and the most widely used method is to use thiazolium salt as a catalyst to catalyze the acetaldehyde to produce acetoin condensation reaction. Patent application CN1562934A discloses a method for preparing acetoin, which uses acetaldehyde as a raw material and directly realizes the synthesis of acetoin under the catalysis of thiazolium salt. However, due to the instability of thiazolium salt itself, the reaction process often requires the addition of a large excess of thiazolium salt; at the same time, the catalyst is easy to decompose, and sulfur-containing impurities with peculiar smell and difficult to remove will be produced during the production process, seriously affecting the quality of acetoin products. Moreover, the acetaldehyde acetoin condensation is a batch reaction, which cannot be produced continuously and is cumbersome to operate. These problems have greatly hindered the large-scale industrial production of acetoin, and there is an urgent need to develop a novel and efficient synthesis route.

[0004] In addition to microbial fermentation and acetaldehyde acetoin condensation methods, Zhang Xiaozhou disclosed in 2001 a method for producing acetoin using 2,3-butanedione as a raw material in the presence of a hydrogenation catalyst. However, this method was plagued by high costs and difficulty in product purification, limiting the large-scale production of acetoin. Patent application CN109772344A discloses a method for producing acetoin by dehydrogenating 2,3-butanediol using a copper-based catalyst. This patented technology utilizes an aluminosilicate as a carrier, loaded with copper and at least one auxiliary metal, an alkali metal, and a ketone additive. The preferred copper content is 40-50 wt.%. The resulting catalyst can achieve an acetoin yield of 74%. However, the addition of toxic elements such as Cr and Ni to the auxiliary metals poses a safety hazard. Due to the readily available and low-cost copper raw material, copper-based catalysts have come into the spotlight. In similar research on alcohol dehydrogenation reactions, patent application CN115106094A discloses a copper-based hydrotalcite-ZrO2 composite support catalyst Cu for catalytic alcohol dehydrogenation. x -Cr y -M z / Mg (6-x) Al (2-z) -Zr w , maintaining a high dehydrogenation stability of 1,4-butanediol at high copper content (20-30wt.%).

[0005] Copper-based catalysts are effective in existing alcohol dehydrogenation reactions. However, existing methods for producing acetoin still have room for improvement in terms of large-scale industrial production, reduced toxic metal addition, and lower costs. Summary of the Invention

[0006] In response to the above technical problems and the shortcomings in the art, the present invention provides a method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst. The method uses a copper-based hydrotalcite catalyst with a low copper loading to catalyze the anaerobic dehydrogenation of 2,3-butanediol to prepare acetoin with high selectivity.

[0007] A method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst, wherein a copper-based hydrotalcite catalyst is used to catalyze the oxygen-free dehydrogenation of 2,3-butanediol in an inert gas atmosphere to produce acetoin with high selectivity.

[0008] The preparation method of the copper-based hydrotalcite catalyst comprises: dissolving a copper salt, a reducing agent, a magnesium salt, and an aluminum salt in a solvent, performing co-precipitation in the presence of a precipitant, and washing, drying, and calcining the precipitated product to obtain the copper-based hydrotalcite catalyst;

[0009] The reducing agent is N2H4.

[0010] The copper content in the copper-based hydrotalcite catalyst may be 1 wt% to 50 wt%, and further may be 6 wt% to 15 wt%.

[0011] In one embodiment, in the preparation method of the copper-based hydrotalcite catalyst, the Al in the aluminum salt 3+ With Mg in magnesium salts 2+ The molar ratio is 1:3.

[0012] The method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst can adopt a fixed bed reactor or a trickle bed reactor.

[0013] The inert gas may be one or more gases such as nitrogen, rare gases (such as argon, helium, etc.) that will not participate in or affect the oxygen-free dehydrogenation reaction.

[0014] In one embodiment, the temperature of the oxygen-free dehydrogenation reaction is 220-280° C. (eg, 250° C.) and the pressure is 0.1-0.5 MPa.

[0015] In one embodiment, the weight hourly space velocity of 2,3-butanediol in the anaerobic dehydrogenation reaction is 0.01 to 10 h -1 , for example, it can be 0.1h -1 .

[0016] In the preparation method of the copper-based hydrotalcite catalyst, the copper salt, the magnesium salt, and the aluminum salt can be independently selected from at least one of nitrates, sulfates, chlorides, and acetates.

[0017] In the preparation method of the copper-based hydrotalcite catalyst, the Cu 2+ The molar ratio of the reducing agent can be 0.25 to 2:1, preferably 1:2.

[0018] In the method for preparing the copper-based hydrotalcite catalyst, the proportion of water in the solvent may be 40-100 vol%, preferably 50-60 vol%, the proportion of ethanol may be 0-20 vol%, preferably 10-20 vol%, and the proportion of ethylene glycol may be 0-40 vol%, preferably 20-40 vol%. In a preferred embodiment, in the method for preparing the copper-based hydrotalcite catalyst, the proportion of water in the solvent is 50-60 vol%, the proportion of ethanol is 10-20 vol%, and the proportion of ethylene glycol is 20-40 vol%.

[0019] In the method for preparing the copper-based hydrotalcite catalyst, the precipitant may be sodium carbonate and sodium hydroxide.

[0020] In one embodiment, in the method for preparing the copper-based hydrotalcite catalyst, during the co-precipitation process, the pH of the system is controlled within the range of 8 to 12, preferably within the range of 10±0.1.

[0021] In the method for preparing the copper-based hydrotalcite catalyst, the co-precipitation temperature may be -20 to +60° C., for example, room temperature.

[0022] In the method for preparing the copper-based hydrotalcite catalyst, the calcination temperature may be 300-600°C, preferably 380-420°C, and more preferably 400°C.

[0023] In the preparation method of the copper-based hydrotalcite catalyst, the heating rate of the calcination may be 0.5 to 20° C. / min, for example, 5° C. / min.

[0024] The copper-based hydrotalcite catalyst of the present invention has the following characteristics:

[0025] 1) The layered structure of magnesium-aluminum hydrotalcite provides conditions for the high dispersion of Cu, greatly reducing the input of Cu precursor.

[0026] 2) After copper salt and N2H4 reducing agent are mixed in a solvent, they are co-precipitated with aluminum salt and magnesium salt to obtain a product with a higher content of Cu 0 、Cu + and more stable Cu 0 / + / Cu 2+ than that of copper-based hydrotalcite catalyst.

[0027] 3) Copper and hydrotalcite have a strong metal-support interaction, achieving strong catalytic stability in the efficient selective dehydrogenation of 2,3-butanediol to acetoin.

[0028] Compared with the prior art, the present invention has the following advantages: the catalyst is stable and not easily lost during the selective dehydrogenation of 2,3-butanediol to acetoin. The method is simple to operate and has good economic benefits. The catalyst is environmentally friendly and efficient, and its use in the selective oxygen-free dehydrogenation of 2,3-butanediol facilitates large-scale production and has promising industrial application prospects.

[0029] 1. The hydrotalcite used in the present invention has a layered structure, which can provide a highly dispersed adhesion environment for copper, increase the dispersion of the loaded metal, improve the catalytic stability, reduce the loaded metal content, and reduce costs.

[0030] 2. The method for preparing the copper-based hydrotalcite catalyst used in the present invention increases and stabilizes the Cu in the catalyst by adding the reducing agent N2H4. 0 、Cu + content.

[0031] 3. The copper-based hydrotalcite catalyst used in the present invention, in one embodiment, catalyzes the selective dehydrogenation of 2,3-butanediol to produce acetoin, showing high 2,3-butanediol conversion and acetoin selectivity.

[0032] 4. The fixed bed or trickle bed reactor used in the present invention can be produced continuously and is suitable for industrial large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The X-ray diffraction (XRD) spectra of the copper-based hydrotalcite catalyst in Example 1 and the magnesium-aluminum hydrotalcite catalyst in Example 2 are shown.

[0034] Figure 2 These are the H2 temperature-programmed reduction spectra of the copper-based hydrotalcite catalyst CuMgAl-LDO-N2H4 in Example 1 and the copper-based hydrotalcite catalyst CuMgAl-LDO in Example 3.

[0035] Figure 3 This is a graph showing the stability of acetoin yield over 100 hours of the copper-based hydrotalcite catalyst of Example 7. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to the accompanying drawings and specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0037] Example 1

[0038] Weigh 9.615g of magnesium nitrate hexahydrate and 4.689g of aluminum nitrate nonahydrate into 50mL of a mixed solvent consisting of 60vol% water, 20vol% ethanol, and 20vol% ethylene glycol. Stir until dissolved. Then add 0.712g of copper nitrate trihydrate and 190mL of N2H4 reducing agent. Weigh 2.65g of anhydrous sodium carbonate and dissolve it in 50mL of water to prepare a 0.5M sodium carbonate solution. Weigh 4g of sodium hydroxide and dissolve it in 25mL of water to prepare a 2M sodium hydroxide solution. Slowly add the magnesium nitrate, aluminum nitrate, copper nitrate, and N2H4 reducing agent solution dropwise to the sodium carbonate solution, maintaining the pH of the reaction system at 10±0.1 during addition with sodium hydroxide solution. Stir the reaction mixture for 16 hours, then filter. Wash the filter cake with water until the eluent is nearly neutral, then dry it in a vacuum at 60°C for 12 hours. Finally, the temperature was raised to 400°C at a rate of 5°C / min and calcined for 6 hours to obtain a copper-based hydrotalcite catalyst CuMgAl-LDO-N2H4 with a Cu content of 7 wt%.

[0039] Example 2

[0040] Weigh 9.615g of magnesium nitrate hexahydrate and 4.689g of aluminum nitrate nonahydrate into 50mL of a mixed solvent consisting of 60vol% water, 20vol% ethanol, and 20vol% ethylene glycol, and stir until dissolved. Weigh 2.65g of anhydrous sodium carbonate and dissolve it in 50mL of water to prepare a 0.5M sodium carbonate solution. Weigh 4g of sodium hydroxide and dissolve it in 25mL of water to prepare a 2M sodium hydroxide solution. Slowly add the magnesium nitrate and aluminum nitrate mixed solution dropwise to the sodium carbonate solution, maintaining the pH of the reaction system at 10±0.1 during addition with sodium hydroxide solution. Stir the reaction mixture for 16 hours, then filter and wash the filter cake with water until the eluent is nearly neutral. Then, vacuum dry at 60°C for 12 hours. Finally, calcine the mixture at 400°C at a rate of 5°C / min for 6 hours to obtain the magnesium-aluminum hydrotalcite catalyst MgAl-LDO.

[0041] Example 3

[0042] The only difference from Example 1 is that the N2H4 reducing agent is not added, and the rest are the same to obtain a copper-based hydrotalcite catalyst CuMgAl-LDO.

[0043] Experiment 1

[0044] 0.5 g of the catalysts of Example 1 and Example 3 were weighed respectively, and 1.5 g of quartz sand was added to each to dilute them. A fixed bed reactor was used. Nitrogen was used as the carrier gas, the reaction pressure was 0.1 MPa, the reaction temperature was 250°C, and the weight hourly space velocity of 2,3-butanediol was 0.1 h -1 , and the conversion rate of 2,3-butanediol and the selectivity of acetoin were obtained.

[0045] Weigh 0.5g of the catalyst from Example 3, add 1.5g of quartz sand to dilute, and use a fixed bed reactor. Before the reaction, introduce 10vol% H2 with nitrogen as the carrier gas, reduce at 300℃ for 2h, and cool to room temperature. Further adjust the experimental conditions to use nitrogen as the carrier gas, reaction pressure of 0.1MPa, reaction temperature of 250℃, and 2,3-butanediol weight hourly space velocity of 0.1h -1 , and the conversion rate of 2,3-butanediol and the selectivity of acetoin were obtained.

[0046] The catalysts of Example 1 and Example 2 were characterized by XRD. Figure 1 The catalysts of Example 1 and Example 3 were subjected to temperature programmed reduction experiments. The results are shown in Figure 2 XPS characterization was performed on the samples before and after the catalytic selective anaerobic dehydrogenation of 2,3-butanediol in Example 1 and Example 3. The results are shown in Table 1.

[0047] Table 1

[0048]

[0049] Result analysis: Figure 1 As shown in Figure 2, XRD analysis shows that the addition of a small amount of copper (7 wt%) does not destroy the structure of the hydrotalcite material. The evenly dispersed copper is not easy to sinter and has good catalytic activity. The results of the temperature-programmed reduction of the samples in Example 1 and Example 3 are shown in Figure 2. Figure 2 As shown, compared with Example 1, the H2 reduction peak of Example 3 has a shoulder peak, indicating that the Cu species on its surface are diverse or the particles are not uniform. Through the XPS characterization results of the catalysts of Example 1 and Example 3 before and after the reaction, it was found that the addition of the reducing agent stabilizes the Cu as the active component on the copper-based catalyst. 0 and Cu + The content of MgCl2O3 is 1.37kJ / cm3, and the catalyst system and reactant molecules have more stable electron transfer cycle ability.

[0050] Example 4

[0051] The only difference from Example 1 is that 0.712 g of copper nitrate trihydrate is replaced with 0.403 g of copper chloride, and the rest is the same to obtain a copper-based hydrotalcite catalyst.

[0052] Example 5

[0053] The only difference from Example 1 is that 0.712 g of copper nitrate trihydrate is replaced with 0.471 g of copper sulfate, and the rest is the same to obtain a copper-based hydrotalcite catalyst.

[0054] Experiment 2

[0055] The reaction conditions were consistent with those in Experiment 1, and the catalytic conversion and acetoin selectivity of the catalysts of Examples 4 and 5 in the anaerobic dehydrogenation of 2,3-butanediol were obtained. The results are shown in Table 2.

[0056] Table 2

[0057] Example Copper precursor Feeding pressure temperature Weight Hourly Space Speed Conversion rate Selectivity 4 copper sulfate 0.471g 0.1MPa 250℃ <![CDATA[0.1h -1 ]]> 83％ 87％ 5 Copper chloride 0.403g 0.1MPa 250℃ <![CDATA[0.1h -1 ]]> 81％ 86％

[0058] Results Analysis: Comparison of Examples 1, 4, and 5, using different precursor types but identical raw materials and preparation processes, indicates that different precursors affect the performance of copper-based hydrotalcite catalysts in the anaerobic dehydrogenation of 2,3-butanediol to acetoin, with nitrate being the preferred precursor.

[0059] Examples 6 to 8

[0060] The only difference from Example 1 is that copper nitrate trihydrate is changed from 0.712 g to 0.145 g, 1.425 g, and 4.274 g in sequence, and the rest are the same, to obtain copper-based hydrotalcite catalysts with Cu contents of 1.5 wt%, 14 wt%, and 42 wt%.

[0061] Experiment 3

[0062] The reaction conditions were consistent with those in Experiment 1, and the catalytic conversion rates and acetoin selectivities of the catalysts of Examples 6 to 8 were obtained in the anaerobic dehydrogenation of 2,3-butanediol. The results are shown in Table 3.

[0063] Table 3

[0064] Example Precursor Feeding pressure temperature Weight Hourly Space Speed Conversion rate Selectivity 6 Copper nitrate trihydrate 0.145g 0.1MPa 250℃ <![CDATA[0.1h -1 ]]> 21％ 99％ 7 Copper nitrate trihydrate 1.425g 0.1MPa 250℃ <![CDATA[0.1h -1 ]]> 97％ 73％ 8 Copper nitrate trihydrate 4.274g 0.1MPa 250℃ <![CDATA[0.1h -1 ]]> 98％ 52％

[0065] Analysis of results: In Examples 6 to 8, the amount of precursor feed is different, and the other preparation processes are the same. Combined with the performance of Example 1 in Experiment 1, from the results, as the amount of copper-containing precursor feed increases, the conversion rate of 2,3-butanediol increases, the selectivity of acetoin decreases, and the preferred range of the catalyst Cu content is about 7wt% to 14wt%. It is speculated that the reason is that copper easily forms a strong metal carrier interaction with magnesium oxide and aluminum oxide. When the feed amount changes, the copper / copper oxide particle size and dispersion on the surface / interlayer of hydrotalcite change. This interaction is regulated, which in turn affects the 2,3-butanediol anaerobic dehydrogenation reaction rate and acetoin selectivity. Among them, the acetoin preparation stability of the catalyst in Example 7 (the experimental conditions are the same as those in Experiment 1) is as follows Figure 3 As shown in the figure, the acetoin yield was stable at more than 70% during the 100 h test.

[0066] Examples 9 to 11

[0067] The only difference from Example 1 is that the reducing agent 190 mL of N2H4 was changed to 380 mL, 95 mL, and 47.5 mL in sequence, and the rest were the same to obtain a copper-based hydrotalcite catalyst.

[0068] Experiment 4

[0069] The reaction conditions were consistent with those in Experiment 1, and the catalytic conversion rates and acetoin selectivities of the catalysts of Examples 9 to 11 in the anaerobic dehydrogenation of 2,3-butanediol were obtained. The results are shown in Table 4.

[0070] Table 4

[0071] Example Copper:reducing agent molar ratio pressure temperature Conversion rate Selectivity 9 1:4 0.1MPa 250℃ 79％ 80％ 10 1:1 0.1MPa 250℃ 87％ 84％ 11 2:1 0.1MPa 250℃ 83％ 84％

[0072] Result analysis: Combined with the performance of Example 1 in Experiment 1, the results show that the amount of reducing agent added has a significant impact on the catalyst's catalytic performance of 2,3-butanediol conversion and acetoin selectivity, confirming that the preferred molar ratio of Cu to reducing agent is 1:2.

[0073] Examples 12-13

[0074] The only difference from Example 1 is that the calcination temperature is changed from 400° C. to 200° C. and 600° C. in sequence, and the rest are the same to obtain a copper-based hydrotalcite catalyst.

[0075] Examples 14-15

[0076] The only difference from Example 1 is that the pH of the reaction system is changed from 10±0.1 to 8±0.1 and 12±0.1 in sequence, and the rest are the same to obtain a copper-based hydrotalcite catalyst.

[0077] Experiment 5

[0078] The reaction conditions were consistent with those in Experiment 1, and the catalytic conversion rates and acetoin selectivities of the catalysts of Examples 12 to 15 in the anaerobic dehydrogenation of 2,3-butanediol were obtained. The results are shown in Table 5.

[0079] Table 5

[0080] Example Precursor Feed molar ratio Calcination temperature pH Conversion rate Selectivity 12 Magnesium nitrate hexahydrate:Aluminum nitrate nonahydrate 3:1 200℃ 10±0.1 74％ 83％ 13 Magnesium nitrate hexahydrate:Aluminum nitrate nonahydrate 3:1 600℃ 10±0.1 90％ 71％ 14 Magnesium nitrate hexahydrate:Aluminum nitrate nonahydrate 3:1 400℃ 8±0.1 79％ 86％ 15 Magnesium nitrate hexahydrate:Aluminum nitrate nonahydrate 3:1 400℃ 12±0.1 83％ 85％

[0081] Results Analysis: In Examples 12-15, the calcination temperature and pH value were varied, while the other preparation processes remained the same. Combined with the performance of Example 1 in Experiment 1, the results indicate that different preparation conditions significantly impact the catalyst's 2,3-butanediol conversion rate and acetoin selectivity. The optimal calcination temperature is 400°C, and the optimal pH is 10±0.1.

[0082] Examples 16 to 18

[0083] The catalyst prepared in Example 1 was used, and the weight hourly space velocity of 2,3-butanediol in Experiment 1 was changed to 1h -1 , 5h -1 , 10h -1 , and the rest are the same.

[0084] Example 19

[0085] The catalyst prepared in Example 1 was used, and the reaction pressure in Experiment 1 was changed to 0.2 MPa, with the rest remaining the same.

[0086] Example 20

[0087] The catalyst prepared in Example 1 was used, and the reaction temperature in Experiment 1 was changed to 220° C., with the rest remaining the same.

[0088] Example 21

[0089] The catalyst prepared in Example 1 was used, and the reaction pressure in Experiment 1 was changed to 0.5 MPa, and the reaction temperature was changed to 280° C., with the rest remaining the same.

[0090] Experiment 6

[0091] Table 6 shows the conversion of 2,3-butanediol and the selectivity of acetoin in Examples 16 to 21.

[0092] Table 6

[0093] Example Precursor Feeding pressure temperature Weight Hourly Space Speed Conversion rate Selectivity 16 Copper nitrate trihydrate 0.712g 0.1MPa 250℃ <![CDATA[1h -1 ]]> 62％ 90％ 17 Copper nitrate trihydrate 0.712g 0.1MPa 250℃ <![CDATA[5h -1 ]]> 55％ 92％ 18 Copper nitrate trihydrate 0.712g 0.1MPa 250℃ <![CDATA[10h -1 ]]> 27％ 95％ 19 Copper nitrate trihydrate 0.712g 0.2MPa 250℃ <![CDATA[0.1h -1 ]]> 56％ 93％ 20 Copper nitrate trihydrate 0.712g 0.1MPa 220℃ <![CDATA[0.1h -1 ]]> 53％ 97％ 21 Copper nitrate trihydrate 0.712g 0.5MPa 280℃ <![CDATA[0.1h -1 ]]> 90％ 64％

[0094] Results Analysis: In Examples 1 and 16-19, increases in weight hourly space velocity and pressure were associated with decreased 2,3-butanediol conversion and increased acetoin selectivity. In Examples 1 and 20, increases in temperature were associated with increased 2,3-butanediol conversion and decreased acetoin selectivity. In Examples 1 and 21, increases in both temperature and pressure were associated with decreased selectivity, while 2,3-butanediol conversion remained unchanged. This indicates that within the experimental conditions, temperature changes have a greater impact on selectivity than pressure changes.

[0095] The performance of the copper-based hydrotalcite catalyst of the present invention in the actual 2,3-butanediol oxygen-free dehydrogenation reaction can be optimized by adjusting the reaction conditions.

[0096] Example 22

[0097] The catalyst prepared in Example 1 was used, except that the 60 vol% water, 20 vol% ethanol, and 20 vol% ethylene glycol in Experiment 1 were changed to 40 vol% water, 20 vol% ethanol, and 40 vol% ethylene glycol, with the rest remaining the same.

[0098] Example 23

[0099] The catalyst prepared in Example 1 was used, and the 60 vol% water, 20 vol% ethanol, and 20 vol% ethylene glycol in Experiment 1 were changed to 50 vol% water, 20 vol% ethanol, and 30 vol% ethylene glycol, with the rest remaining the same.

[0100] Example 24

[0101] The catalyst prepared in Example 1 was used, and the 60 vol% water, 20 vol% ethanol, and 20 vol% ethylene glycol in Experiment 1 were changed to 70 vol% water, 10 vol% ethanol, and 20 vol% ethylene glycol, with the rest remaining the same.

[0102] Experiment 7

[0103] The reaction conditions were consistent with those in Experiment 1, and the catalytic conversion rates and acetoin selectivities of the catalysts of Examples 22 to 24 were obtained in the anaerobic dehydrogenation of 2,3-butanediol. The results are shown in Table 7.

[0104] Table 7

[0105] Example Water:ethanol:ethylene glycol volume ratio pressure temperature Conversion rate Selectivity 22 2:1:2 0.1MPa 250℃ 89％ 87％ 23 5:2:3 0.1MPa 250℃ 91％ 88％ 24 7:1:2 0.1MPa 250℃ 88％ 85％

[0106] Results Analysis: In Examples 22-24, the ratios of water, ethanol, and ethylene glycol in the mixed solvent were varied, while the other preparation processes remained the same. Combined with the performance of Example 1 in Experiment 1, the results indicate that the solvent composition affects the catalyst's performance in terms of 2,3-butanediol conversion and acetoin selectivity. The preferred volumes of each component in the mixed solvent are: 50-60 vol% water, 10-20 vol% ethanol, and 20-40 vol% ethylene glycol.

[0107] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst, characterized in that: A copper-based hydrotalcite catalyst is used to catalyze the oxygen-free dehydrogenation reaction of 2,3-butanediol in an inert gas atmosphere to produce acetoin with high selectivity; the copper content of the copper-based hydrotalcite catalyst is 1wt% to 50wt%; The preparation method of the copper-based hydrotalcite catalyst comprises: dissolving a copper salt, a reducing agent, a magnesium salt, and an aluminum salt in a solvent, performing coprecipitation in the presence of a precipitant, washing, drying, and calcining the precipitated product at 300-600° C. to obtain the copper-based hydrotalcite catalyst; during the coprecipitation process, the system pH is controlled at 8-12; The reducing agent is N2H4.

2. The method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst according to claim 1, characterized in that: The copper content of the copper-based hydrotalcite catalyst is 6 wt% to 15 wt%; In the preparation method of the copper-based hydrotalcite catalyst, the Al in the aluminum salt 3+ With Mg in magnesium salts 2+ The molar ratio is 1:

3.

3. The method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst according to claim 1, characterized in that: The temperature of the oxygen-free dehydrogenation reaction is 220-280° C., and the pressure is 0.1-0.5 MPa.

4. The method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst according to claim 1, characterized in that: The weight hourly space velocity of 2,3-butanediol in the anaerobic dehydrogenation reaction is 0.01 to 10 h -1 .

5. The method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst according to claim 1, characterized in that: In the preparation method of the copper-based hydrotalcite catalyst, the copper salt, the magnesium salt, and the aluminum salt are independently selected from at least one of nitrate, sulfate, chloride, and acetate.

6. The method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst according to claim 1, characterized in that: In the preparation method of the copper-based hydrotalcite catalyst, the Cu 2+ The molar ratio of the reducing agent is 0.25 to 2:

1.

7. The method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst according to claim 6, characterized in that: In the preparation method of the copper-based hydrotalcite catalyst, the Cu 2+ The molar ratio of the reducing agent is 1:

2.

8. The method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst according to claim 1, characterized in that: In the preparation method of the copper-based hydrotalcite catalyst, the proportion of water in the solvent is 40 vol% to 100 vol%, the proportion of ethanol is 0-20 vol%, and the proportion of ethylene glycol is 0-40 vol%.

9. The method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst according to claim 8, characterized in that: In the preparation method of the copper-based hydrotalcite catalyst, the proportion of water in the solvent is 50 vol% to 60 vol%, the proportion of ethanol is 10 vol% to 20 vol%, and the proportion of ethylene glycol is 20 vol% to 40 vol%.

10. The method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst according to claim 1, characterized in that: In the preparation method of the copper-based hydrotalcite catalyst, the precipitating agents are sodium carbonate and sodium hydroxide.

11. The method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst according to claim 1, characterized in that: In the preparation method of the copper-based hydrotalcite catalyst, during the coprecipitation process, the pH of the system is controlled within the range of 10±0.

1.

12. The method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst according to claim 1, characterized in that: In the preparation method of the copper-based hydrotalcite catalyst, the calcination temperature is 380-420°C.

13. The method for preparing acetoin by selective dehydrogenation of 2,3-butanediol using a copper-based catalyst according to claim 12, characterized in that: In the preparation method of the copper-based hydrotalcite catalyst, the calcination temperature is 400°C.

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