CN117800819A

CN117800819A - A method for preparing acetoin by selective dehydrogenation of 2,3-butanediol catalyzed by a copper-based catalyst

Info

Publication number: CN117800819A
Application number: CN202311740861.9A
Authority: CN
Inventors: 张超; 张治国; 孙扬健; 董阳阳; 陈仪; 洪龙城; 申雅靓
Original assignee: Zhejiang University ZJU; Institute of Zhejiang University Quzhou
Current assignee: Zhejiang University ZJU; Institute of Zhejiang University Quzhou
Priority date: 2023-12-18
Filing date: 2023-12-18
Publication date: 2024-04-02
Anticipated expiration: 2043-12-18
Also published as: CN117800819B

Abstract

The invention discloses a method for preparing acetoin by catalyzing selective dehydrogenation of 2, 3-butanediol by a copper-based catalyst, which utilizes a copper-based hydrotalcite catalyst to catalyze 2, 3-butanediol to generate anaerobic dehydrogenation reaction in an inert gas atmosphere, so as to generate acetoin with high selectivity; the preparation method of the copper-based hydrotalcite catalyst comprises the following steps: dissolving copper salt, reducer, magnesium salt and aluminum salt in solvent, coprecipitating in the presence of precipitant, washing and drying the precipitated productCalcining to obtain a copper-based hydrotalcite catalyst; the reducing agent is N ₂ H ₄ . The invention uses the copper-based hydrotalcite catalyst with low copper load, and can catalyze 2, 3-butanediol to prepare acetoin in a high selectivity way.

Description

Method for preparing acetoin by catalyzing selective dehydrogenation of 2, 3-butanediol by copper-based catalyst

Technical Field

The invention relates to the technical field of preparation of acetoin by selective dehydrogenation of 2, 3-butanediol, in particular to a method for preparing acetoin by selective dehydrogenation of 2, 3-butanediol under the catalysis of a copper-based catalyst.

Background

Acetoin, also known as 3-hydroxy butanone (acetoin), has a milk flavour and is naturally found in grape, coffee, corn and some animal tissues. Acetoin has a variety of uses, and can be used as a flavor enhancer for coffee, nuts, chocolate, dairy products and alcoholic drinks, and can also be used as an important tobacco additive to improve tobacco quality. Meanwhile, the 3-hydroxy butanone contains active groups such as hydroxy, carbonyl and the like, and has important application in the field of pharmaceutical chemistry.

The main production methods in the industry currently include microbial fermentation and chemical synthesis. The microbial fermentation method has simple process operation and environment-friendly production process, but the acquisition of high-yield strains is still a key technical bottleneck of industrialization of the route. Patent CN111705027B discloses a method for producing acetoin by microbial fermentation, which is characterized in that constructed genetic engineering strain B.subilis 6-7 DeltaAcuB DeltaAcoB Deltarex is cultivated in a 5L fermentation tank for 96h, and 67.5 g.L can be realized ^-1 The preparation of acetoin improves the production efficiency to 0.7g.L ^-1 ·h ^-1 . However, the biological fermentation method for producing acetoin still has the problems of low yield and high production cost. Therefore, the mass production of acetoin needs to be synthesized by a chemical method, and the most widely applied method is to take thiazolium salt asThe catalyst catalyzes acetaldehyde to generate an acyloin condensation reaction to prepare acetoin. Patent application CN1562934a discloses a method for preparing acetoin, which takes acetaldehyde as a raw material and directly realizes the synthesis of acetoin under the catalysis of thiazole salt. However, due to the instability of the thiazolium salt itself, the reaction process often requires the addition of a large excess of thiazolium salt; meanwhile, the catalyst is easy to decompose, sulfur-containing impurities which have peculiar smell and are difficult to remove can be generated in the production process, and the quality of acetoin products is seriously influenced. Moreover, the condensation of acetoin into batch reaction, which cannot be carried out continuously, is troublesome to operate, and the problems greatly prevent the mass industrialized production of acetoin, so that a novel and efficient synthetic route is needed to be developed.

In addition to the microbial fermentation method and the acetaldehyde acyloin condensation method, zhang Xiaozhou in 2001, a method for preparing acetoin by using 2, 3-butanedione as a raw material under the action of a hydrogenation catalyst is disclosed, but the method has the problems of high cost and difficulty in purifying a product, and limits the mass production of the acetoin. Patent application CN109772344a discloses a method for producing acetoin by catalyzing 2, 3-butanediol dehydrogenation with a copper-based catalyst, the patent technology uses aluminosilicate as a carrier to load copper and at least one auxiliary metal, alkali metal and ketone additive, wherein the preferred amount of copper is 40-50 wt%, the yield of the obtained catalyst acetoin can reach 74%, but the addition of toxic elements such as Cr, ni and the like in the auxiliary metal has potential safety hazards. Copper-based catalysts are in the field of view of people because of the availability and low cost of copper raw materials. In a similar study of alcohol dehydrogenation reactions, patent application CN115106094A discloses a copper-based hydrotalcite-ZrO for catalyzing alcohol dehydrogenation ₂ Catalyst Cu with composite carrier structure _x -Cr _y -M _z /Mg _(6-x) Al _(2-z) -Zr _w Higher 1, 4-butanediol dehydrogenation stability is maintained at high copper levels (20-30 wt.%).

In the existing alcohol dehydrogenation reaction, the effect of the copper-based catalyst is remarkable. However, the prior art acetoin production method has room for improvement in terms of considerable scale industrial production, reduction of toxic metal addition, reduction of cost and the like.

Disclosure of Invention

Aiming at the technical problems and the defects in the art, the invention provides a method for preparing acetoin by catalyzing selective dehydrogenation of 2, 3-butanediol by using a copper-based catalyst, wherein the method can be used for preparing acetoin by catalyzing anaerobic dehydrogenation of 2, 3-butanediol with high selectivity by using a copper-based hydrotalcite catalyst with low copper load.

A method for preparing acetoin by catalyzing 2, 3-butanediol to selectively dehydrogenate by a copper-based catalyst, wherein the copper-based hydrotalcite catalyst is utilized to catalyze 2, 3-butanediol to perform anaerobic dehydrogenation reaction in an inert gas atmosphere, so that acetoin is generated with high selectivity;

the preparation method of the copper-based hydrotalcite catalyst comprises the following steps: copper salt, reducing agent, magnesium salt and aluminum salt are dissolved in solvent, coprecipitation is carried out under the existence of precipitant, and the precipitated product is washed, dried and calcined to obtain the copper-based hydrotalcite catalyst;

the reducing agent is N ₂ H ₄ 。

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

In one embodiment, in the preparation method of the copper-based hydrotalcite catalyst, al in the aluminum salt ³⁺ With Mg in magnesium salt ²⁺ The molar ratio of (2) is 1:3.

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

The inert gas may be one or more of nitrogen, noble gases (e.g., argon, helium, etc.), and the like that do not participate in or interfere with the oxygen-free dehydrogenation reaction.

In one embodiment, the temperature of the anaerobic dehydrogenation reaction is 220 to 280 ℃ (e.g., 250 ℃), and the pressure is 0.1 to 0.5MPa.

In one embodiment, the weight hourly space velocity of the 2, 3-butanediol in the anaerobic dehydrogenation reaction is 0.01 to 10h ^-1 For example, it may be specifically 0.1h ^-1 。

In the preparation method of the copper-based hydrotalcite catalyst, copper salt, magnesium salt and aluminum salt can be respectively and independently selected from at least one of nitrate, sulfate, chloride and acetate.

In the preparation method of the copper-based hydrotalcite catalyst, cu in copper salt ²⁺ The molar ratio to the reducing agent may be from 0.25 to 2:1, preferably 1:2.

In the preparation method of the copper-based hydrotalcite catalyst, the water content in the solvent may be 40 to 100vol%, preferably 50 to 60vol%, the ethanol content may be 0 to 20vol%, preferably 10 to 20vol%, and the ethylene glycol content may be 0 to 40vol%, preferably 20 to 40vol%. In a preferred embodiment, in the method for preparing a copper-based hydrotalcite catalyst, the solvent has a water content of 50 to 60vol%, an ethanol content of 10 to 20vol% and an ethylene glycol content of 20 to 40vol%.

In the preparation method of the copper-based hydrotalcite catalyst, the precipitant can be sodium carbonate and sodium hydroxide.

In one embodiment, in the preparation method of the copper-based hydrotalcite catalyst, the pH of the system is controlled to be 8-12, preferably within the range of 10+/-0.1, in the coprecipitation process.

In the preparation method of the copper-based hydrotalcite catalyst, the temperature of the coprecipitation may be-20 to +60 ℃, for example, may be room temperature.

In the method for preparing the copper-based hydrotalcite catalyst, the calcination temperature may be 300 to 600 ℃, preferably 380 to 420 ℃, and more preferably 400 ℃.

In the preparation method of the copper-based hydrotalcite catalyst, the temperature rising rate of the calcination may be 0.5 to 20 ℃/min, for example, may be 5 ℃/min.

The copper-based hydrotalcite catalyst of the invention has the following characteristics:

1) The magnalium hydrotalcite layered structure provides conditions for the high dispersion of Cu, and greatly reduces the input amount of Cu precursor.

2) Copper salt and N ₂ H ₄ Mixing the reducer in solvent, and coprecipitating with aluminum salt and magnesium salt to obtain Cu with higher content ⁰ 、Cu ⁺ And more stable Cu ^0/+ /Cu ²⁺ Copper of specific ratioHydrotalcite-based catalysts.

3) Copper and hydrotalcite have stronger interaction between metal carriers, so that stronger catalytic stability in preparation of acetoin by high-efficiency selective dehydrogenation of 2, 3-butanediol is realized.

Compared with the prior art, the invention has the beneficial effects that: the catalyst is stable and is not easy to run off in the process of preparing acetoin by selectively dehydrogenating 2, 3-butanediol. The method has simple operation and good economic benefit. The catalyst is green and efficient, is used for selective anaerobic dehydrogenation of 2, 3-butanediol, is beneficial to realizing large-scale production, and has good industrial application prospect.

1. The hydrotalcite adopted by the invention has a layered structure, can provide a high-dispersion adhesion environment for copper, increases the dispersion degree of the load metal, improves the catalytic stability, reduces the content of the load metal and reduces the cost.

2. The preparation method of the copper-based hydrotalcite catalyst adopted by the invention comprises the step of reducing agent N ₂ H ₄ The addition of (2) increases and stabilizes Cu in the catalyst ⁰ 、Cu ⁺ Is contained in the composition.

3. According to the copper-based hydrotalcite catalyst adopted by the invention, in one implementation method, 2, 3-butanediol is catalyzed to be selectively dehydrogenated to prepare acetoin, so that the catalyst has high 2, 3-butanediol conversion rate and acetoin selectivity.

4. The fixed bed or trickle bed reactor used in the invention can realize continuous production and is suitable for industrialized mass production.

Drawings

FIG. 1 is an X-ray diffraction (XRD) spectrum of the copper-based hydrotalcite catalyst of example 1 and the magnesium-aluminum hydrotalcite catalyst of example 2.

FIG. 2 is a copper-based hydrotalcite catalyst CuMgAl-LDO-N of example 1 ₂ H ₄ And H of copper-based hydrotalcite catalyst CuMgAl-LDO in example 3 ₂ Temperature programming reduction spectrogram.

FIG. 3 is a graph showing the results of the stability of acetoin productivity of copper-based hydrotalcite catalyst 100h of example 7.

Detailed Description

The invention will be further elucidated with reference to the drawings and to specific embodiments. It is to be understood that these examples are illustrative of the present invention and are not intended to limit the scope of the present invention.

Example 1

9.615g of magnesium nitrate hexahydrate and 4.689g of aluminum nitrate nonahydrate are weighed into 50mL of a mixed solvent consisting of 60vol% water, 20vol% ethanol and 20vol% ethylene glycol, stirred until dissolved, and then 0.712g of copper nitrate hexahydrate and 190mL of N are added ₂ H ₄ A reducing agent. 2.65g of anhydrous sodium carbonate was weighed into 50mL of water to prepare a 0.5M sodium carbonate solution. 4g of sodium hydroxide was weighed and dissolved in 25mL of water to prepare a 2M sodium hydroxide solution. Magnesium nitrate, aluminum nitrate and copper nitrate and N ₂ H ₄ The mixed solution of the reducing agent is slowly dripped into the sodium carbonate solution, and the pH value of the reaction system is kept to be 10+/-0.1 when the sodium hydroxide solution is used for controlling the dripping. The reaction solution was stirred for 16h and filtered, the filter cake was washed with water until the eluate was nearly neutral, and then dried in vacuo at 60 ℃ for 12h. Finally, heating to 400 ℃ at 5 ℃ per minute and roasting for 6 hours to obtain the copper-based hydrotalcite catalyst CuMgAl-LDO-N with the Cu content of 7wt% ₂ H ₄ 。

Example 2

9.615g of magnesium nitrate hexahydrate and 4.689g of aluminum nitrate nonahydrate were weighed into 50mL of a mixed solvent composed of 60vol% water, 20vol% ethanol and 20vol% ethylene glycol, and stirred until dissolved. 2.65g of anhydrous sodium carbonate was weighed into 50mL of water to prepare a 0.5M sodium carbonate solution. 4g of sodium hydroxide was weighed and dissolved in 25mL of water to prepare a 2M sodium hydroxide solution. The mixed solution of magnesium nitrate and aluminum nitrate is slowly dripped into the sodium carbonate solution, and the pH value of the reaction system is kept to be 10+/-0.1 when the sodium hydroxide solution is used for controlling the dripping. The reaction solution was stirred for 16h and filtered, the filter cake was washed with water until the eluate was nearly neutral, and then dried in vacuo at 60 ℃ for 12h. Finally, heating to 400 ℃ at 5 ℃/min and roasting for 6 hours to obtain the MgAl-LDO catalyst.

Example 3

The difference from example 1 is only that N is not added ₂ H ₄ The reducing agent and the rest are the same, and the copper-based hydrotalcite catalyst CuMgAl-LDO is obtained.

Experiment one

Weigh example 1 and the test separately0.5g of the catalyst of example 3 was diluted with 1.5g of quartz sand each, and a fixed bed reactor was used. Nitrogen is used as carrier gas, the reaction pressure is 0.1MPa, the reaction temperature is 250 ℃, and the weight hourly space velocity of 2, 3-butanediol is 0.1h ^-1 The conversion rate of 2, 3-butanediol and the selectivity of acetoin are obtained.

0.5g of the catalyst of example 3 was weighed, and 1.5g of quartz sand was added for dilution, and a fixed bed reactor was used. Before the reaction, 10vol% H was introduced ₂ Nitrogen is used as carrier gas, the mixture is reduced for 2 hours at 300 ℃, and the temperature is reduced to room temperature. Further adjusting experimental conditions, taking nitrogen as carrier gas, wherein the reaction pressure is 0.1MPa, the reaction temperature is 250 ℃, and the weight hourly space velocity of 2, 3-butanediol is 0.1h ^-1 The conversion rate of 2, 3-butanediol and the selectivity of acetoin are obtained.

XRD characterization was performed on the catalysts of example 1 and example 2, with reference to fig. 1. The catalysts of example 1 and example 3 were subjected to temperature programmed reduction experiments, and the results are shown in fig. 2. XPS characterization was performed on samples before and after the catalytic selective anaerobic dehydrogenation of 2, 3-butanediol in examples 1 and 3, and the results are shown in Table 1.

TABLE 1

Analysis of results: as shown in figure 1, XRD detection shows that the addition of a small amount of copper (7 wt%) does not damage the structure of hydrotalcite material, and the uniformly 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 FIG. 2, and compared with example 1, example 3 shows H ₂ Shoulder peaks appear in the reduction peaks, which indicate that Cu on the surface is diverse in species or nonuniform in particles. As a result of XPS characterization of the catalysts of example 1 and example 3 before and after the reaction, it was found that the addition of the reducing agent stabilized Cu as an active component on the copper-based catalyst ⁰ And Cu ⁺ The catalyst system and the reactant molecules have a more stable electron transfer circulation capability.

Example 4

The difference from example 1 was only that 0.712g of copper nitrate trihydrate was changed to 0.403g of copper chloride, and the rest was the same, to obtain a copper-based hydrotalcite catalyst.

Example 5

The difference from example 1 was only that 0.712g of copper nitrate trihydrate was changed to 0.471g of copper sulfate, and the rest was the same, to obtain a copper-based hydrotalcite catalyst.

Experiment two

The catalyst of example 4 and example 5 showed catalytic conversion and acetoin selectivity in the oxygen-free dehydrogenation of 2, 3-butanediol, in accordance with the reaction conditions in experiment one. The results are shown in Table 2.

TABLE 2

Examples

Copper precursor

Feeding material

Pressure of

Temperature (temperature)

Weight hourly space velocity

Conversion rate

Selectivity of

4

Copper sulfate

0.471g

0.1MPa

250℃

0.1h ^-1

83％

87％

5

Copper chloride

0.403g

0.1MPa

250℃

0.1h ^-1

81％

86％

Analysis of results: comparative example 1, example 4 and example 5 were different in the type of precursor and the other raw materials and the preparation process were the same. From the results, different precursors can influence the performance of the copper-based hydrotalcite catalyst in the reaction of preparing acetoin by oxygen-free dehydrogenation of 2, 3-butanediol, and nitrate is taken as a preferable precursor.

Examples 6 to 8

The difference from example 1 was only that the copper nitrate trihydrate was changed from 0.712g to 0.145g, 1.425g, 4.274g in this order, and the remainder was the same, to obtain a copper-based hydrotalcite catalyst having a Cu content of 1.5wt%, 14wt%, 42 wt%.

Experiment three

The reaction conditions were identical to those in experiment one, and the catalysts of examples 6 to 8 were obtained with respect to the catalytic conversion and acetoin selectivity in the anaerobic dehydrogenation of 2, 3-butanediol. The results are shown in Table 3.

TABLE 3 Table 3

Examples

Precursor body

Feeding material

Pressure of

Temperature (temperature)

Weight hourly space velocity

Conversion rate

Selectivity of

6

Copper nitrate trihydrate

0.145g

0.1MPa

250℃

0.1h ^-1

21％

99％

7

Copper nitrate trihydrate

1.425g

0.1MPa

250℃

0.1h ^-1

97％

73％

8

Copper nitrate trihydrate

4.274g

0.1MPa

250℃

0.1h ^-1

98％

52％

Analysis of results: in examples 6 to 8, the precursor amounts were different, and the other preparation processes were the same. In combination with the performance of example 1 in experiment one, the addition of copper-containing precursor increases, the conversion of 2, 3-butanediol increases, the acetoin selectivity decreases, and the Cu content of the catalyst preferably ranges from about 7wt% to 14wt%. The reason for this is presumed to be: copper is easy to form stronger metal carrier interaction with magnesium oxide and aluminum oxide, when the feeding amount is changed, the particle size and dispersity of copper/copper oxide on the surface/interlayer of hydrotalcite are changed, and the interaction is regulated, so that the anaerobic dehydrogenation reaction rate of 2, 3-butanediol and the acetoin selectivity are influenced. The stability of the catalyst of example 7 in preparation of acetoin (experimental conditions and experiment one) is shown in fig. 3, and the yield of acetoin is stabilized to be 70% or more in the test of 100 h.

Examples 9 to 11

The difference from example 1 is only that the flow rate was changed from 190mL N ₂ H ₄ The reducing agent is changed into 380mL, 95mL and 47.5mL in sequence, and the rest are the same, so that the copper-based hydrotalcite catalyst is obtained.

Experiment four

The reaction conditions were identical to those in experiment one, and the catalysts of examples 9 to 11 were obtained with respect to the catalytic conversion and acetoin selectivity in the anaerobic dehydrogenation of 2, 3-butanediol. The results are shown in Table 4.

TABLE 4 Table 4

Examples	Molar ratio of copper to reducing agent	Pressure of	Temperature (temperature)	Conversion rate	Selectivity of
						9	1:4	0.1MPa	250℃	79％	80％
10	1:1	0.1MPa	250℃	87％	84％
						11	2:1	0.1MPa	250℃	83％	84％

Analysis of results: in combination with the performance of example 1 in experiment one, from the results, the addition amount of the reducing agent has a large influence on the performance of the catalyst in catalyzing the 2, 3-butanediol conversion rate and acetoin selectivity, and the preferred molar ratio of Cu to the reducing agent is confirmed to be 1:2.

Examples 12 to 13

The difference from example 1 was only that the calcination temperature was changed from 400℃to 200℃and 600℃in this order, and the remainder was the same, to obtain a copper-based hydrotalcite catalyst.

Examples 14 to 15

The difference from example 1 is only 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 is the same, thus obtaining the copper-based hydrotalcite catalyst.

Experiment five

The reaction conditions were identical to those in experiment one, and the catalysts of examples 12 to 15 were obtained with respect to the catalytic conversion and acetoin selectivity in the anaerobic dehydrogenation of 2, 3-butanediol. The results are shown in Table 5.

TABLE 5

Examples

Precursor body

Molar ratio of feed

Firing temperature

pH

Conversion rate

Selectivity of

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％

Analysis of results: in examples 12 to 15, the firing temperature and pH were changed, and the other preparation processes were the same. In combination with the performance of example 1 in experiment one, from the results, the different preparation conditions have a large influence on the performance of the catalyst in catalyzing the 2, 3-butanediol conversion and acetoin selectivity, and it is confirmed that the preferred calcination temperature is 400 ℃, and the preferred pH is 10+ -0.1.

Examples 16 to 18

The catalyst prepared in example 1 was used to change the weight hourly space velocity of 2, 3-butanediol in experiment one to 1h ^-1 、5h ^-1 、10h ^-1 The remainder were the same.

Example 19

The catalyst prepared in example 1 was used, and the reaction pressure in experiment one was changed to 0.2MPa, and the rest was the same.

Example 20

The catalyst prepared in example 1 was used, the reaction temperature in experiment one was changed to 220℃and the rest was the same.

Example 21

The catalyst prepared in example 1 was used, the reaction pressure in experiment one was changed to 0.5MPa, the reaction temperature was changed to 280℃and the rest were the same.

Experiment six

Table 6 shows the conversion of 2, 3-butanediol and the acetoin selectivity for examples 16 to 21.

TABLE 6

Examples

Precursor body

Feeding material

Pressure of

Temperature (temperature)

Weight hourly space velocity

Conversion rate

Selectivity of

16

Copper nitrate trihydrate

0.712g

0.1MPa

250℃

1h ^-1

62％

90％

17

Copper nitrate trihydrate

0.712g

0.1MPa

250℃

5h ^-1

55％

92％

18

Copper nitrate trihydrate

0.712g

0.1MPa

250℃

10h ^-1

27％

95％

19

Copper nitrate trihydrate

0.712g

0.2MPa

250℃

0.1h ^-1

56％

93％

20

Copper nitrate trihydrate

0.712g

0.1MPa

220℃

0.1h ^-1

53％

97％

21

Copper nitrate trihydrate

0.712g

0.5MPa

280℃

0.1h ^-1

90％

64％

Analysis of results: in example 1 and examples 16 to 19, an increase in weight hourly space velocity and an increase in pressure are accompanied by a decrease in 2, 3-butanediol conversion and an increase in acetoin selectivity. In examples 1 and 20, an increase in temperature was accompanied by an increase in 2, 3-butanediol conversion and a decrease in acetoin selectivity. In examples 1 and 21, the simultaneous increase in temperature and pressure was accompanied by a decrease in selectivity, with no significant change in 2, 3-butanediol conversion, indicating that the effect of temperature changes on selectivity was greater than pressure changes over the range of experimental conditions.

The performance of the copper-based hydrotalcite catalyst in the actual 2, 3-butanediol anaerobic dehydrogenation reaction can be optimized by adjusting the reaction conditions.

Example 22

Using the catalyst prepared in example 1, 60vol% water, 20vol% ethanol, 20vol% ethylene glycol in experiment one was changed to 40vol% water, 20vol% ethanol, 40vol% ethylene glycol, and the remainder were the same.

Example 23

Using the catalyst prepared in example 1, 60vol% water, 20vol% ethanol, 20vol% ethylene glycol in experiment one was changed to 50vol% water, 20vol% ethanol, 30vol% ethylene glycol, and the remainder were the same.

Example 24

Using the catalyst prepared in example 1, 60vol% water, 20vol% ethanol, 20vol% ethylene glycol in experiment one was changed to 70vol% water, 10vol% ethanol, 20vol% ethylene glycol, and the remainder were the same.

Experiment seven

The reaction conditions were identical to those in experiment one, and the catalysts of examples 22 to 24 were obtained with respect to the catalytic conversion and acetoin selectivity in the anaerobic dehydrogenation of 2, 3-butanediol. The results are shown in Table 7.

TABLE 7

Examples	Volume ratio of water to ethanol to glycol	Pressure of	Temperature (temperature)	Conversion rate	Selectivity of
						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％

Analysis of results: in examples 22 to 24, the proportions of water, ethanol and ethylene glycol in the mixed solvent were changed, and the other preparation processes were the same. In combination with the performance of example 1 in experiment one, from the results, the composition of the solvent influences the performance of the catalyst in terms of 2, 3-butanediol conversion and acetoin selectivity, confirming the volume of each component in the preferred mixed solvent: 50 to 60 volume percent of water, 10 to 20 volume percent of ethanol and 20 to 40 volume percent of glycol.

Further, it will be understood that various changes and modifications may be made by those skilled in the art after reading the foregoing description of the invention, and such equivalents are intended to fall within the scope of the claims appended hereto.

Claims

1. A method for preparing acetoin by catalyzing 2, 3-butanediol to selectively dehydrogenate by a copper-based catalyst is characterized in that the copper-based hydrotalcite catalyst is utilized to catalyze 2, 3-butanediol to perform anaerobic dehydrogenation reaction in an inert gas atmosphere, so that acetoin is generated with high selectivity;

the reducing agent is N ₂ H ₄ 。

2. The method for preparing acetoin by catalyzing selective dehydrogenation of 2, 3-butanediol by using the copper-based catalyst according to claim 1, wherein the copper content in the copper-based hydrotalcite catalyst is 1-50 wt%, and further 6-15 wt%;

in the preparation method of the copper-based hydrotalcite catalyst, al in aluminum salt ³⁺ With Mg in magnesium salt ²⁺ The molar ratio of (2) is 1:3.

3. The method for preparing acetoin by selectively dehydrogenating 2, 3-butanediol by using the copper-based catalyst according to claim 1, wherein the temperature of the anaerobic dehydrogenation reaction is 220-280 ℃ and the pressure is 0.1-0.5 MPa.

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

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

6. The method for preparing acetoin by catalyzing selective dehydrogenation of 2, 3-butanediol by using copper-based catalyst according to claim 1, wherein in the preparation method of the copper-based hydrotalcite catalyst, cu in copper salt is as follows ²⁺ Molar ratio with reducing agent of 0.25About 2:1, preferably about 1:2.

7. The method for preparing acetoin by catalyzing selective dehydrogenation of 2, 3-butanediol by using the copper-based catalyst according to claim 1, wherein the water content in the solvent is 40-100 vol%, preferably 50-60 vol%, the ethanol content is 0-20vol%, preferably 10-20 vol%, and the ethylene glycol content is 0-40vol%, preferably 20-40 vol%.

8. The method for preparing acetoin by catalyzing selective dehydrogenation of 2, 3-butanediol by using the copper-based catalyst according to claim 1, wherein the precipitant is sodium carbonate and sodium hydroxide in the preparation method of the copper-based hydrotalcite catalyst.

9. The method for preparing acetoin by catalyzing selective dehydrogenation of 2, 3-butanediol by using the copper-based catalyst according to claim 1, wherein in the preparation method of the copper-based hydrotalcite catalyst, the pH of a system is controlled to be 8-12, preferably within the range of 10+/-0.1 in the coprecipitation process.

10. The method for preparing acetoin by catalyzing selective dehydrogenation of 2, 3-butanediol by using the copper-based catalyst according to claim 1, wherein the calcining temperature is 300-600 ℃, preferably 380-420 ℃ and further preferably 400 ℃.