CN110841710A

CN110841710A - Preparation method of alkoxy aluminum catalyst and application of alkoxy aluminum catalyst in ester synthesis

Info

Publication number: CN110841710A
Application number: CN201910977647.2A
Authority: CN
Inventors: 张波; 李亚斌; 李云辉; 杨志波; 李越; 苗淳
Original assignee: Bo Huayongli Chemical Inc Tianjin
Current assignee: Bo Huayongli Chemical Inc Tianjin
Priority date: 2019-10-15
Filing date: 2019-10-15
Publication date: 2020-02-28

Abstract

The invention discloses a preparation method of an alkoxy aluminum catalyst and application of the alkoxy aluminum catalyst in ester synthesis. Adding aluminum isopropoxide and fatty alcohol into a reactor, heating and refluxing, fractionating to evaporate the isopropanol and the fatty alcohol remaining in the reaction, and cooling to obtain the corresponding solid alkoxy aluminum catalyst. The catalyst has high-efficiency catalytic activity in catalyzing disproportionation and condensation of aldehyde to prepare ester, wherein the conversion rate of aldehyde can reach more than 95%, and the selectivity of ester can reach more than 92%. The catalyst has a simple preparation route, and the preparation process does not need a catalyst, so that the introduction of impurities is avoided; no hydrogen is generated, so that potential safety hazards are avoided; in addition, the catalyst is a solid heterogeneous catalyst, can ensure the high-efficiency catalytic activity of the catalyst, and can be separated from a reaction system by adopting a mild mode such as filtration or centrifugation and can be repeatedly used.

Description

Preparation method of alkoxy aluminum catalyst and application of alkoxy aluminum catalyst in ester synthesis

Technical Field

The invention relates to the field of chemical industry, in particular to a preparation method of an alkoxy aluminum catalyst and application of the alkoxy aluminum catalyst in ester synthesis.

Background

The ester is an important chemical raw material and is widely applied to industries such as edible essence, daily chemical spices, coating solvent, automobile paint, medicines and the like.

Currently, as a method for synthesizing esters, there are an esterification method using an alcohol and a carboxylic acid as raw materials, a disproportionation method using an alcohol as a raw material, and a condensation method using an aldehyde as a raw material. The esterification method is mature in process and is a commonly adopted method in industrial production, but the method needs acid or alkali as a catalyst, and has the disadvantages of serious equipment corrosion, large pollution, complex post-treatment process, high production cost and high energy consumption. The disproportionation method is characterized in that alcohol is used as a raw material, ester is synthesized by a dehydrogenation one-step method, the route is short, the problem of equipment corrosion does not exist, the reaction needs to be carried out at high temperature and high pressure, the conditions are harsh, the conversion rate of the alcohol and the yield of the ester are not high, and no industrial application report exists. The method for preparing the ester by the aldehyde condensation one-step method has the advantages of concise route, high atom economy, mild reaction conditions, high conversion rate and selectivity, greenness, safety, no equipment corrosion problem and low equipment investment and operation cost, realizes industrial application, and is a future development trend of ester synthesis.

The catalyst used in the condensation method mainly comprises a transition metal complex catalyst and an aluminum alkoxide catalyst. In the field of transition metal complex catalysts, ruthenium and ytterbium complexes are mostly reported, and the catalysts have the advantages of high efficiency, mild reaction conditions, short reaction time and the like, but have complex preparation process, high price, high requirement on raw materials and difficult separation. The alkoxy aluminum catalyst has the advantages of easy obtainment of raw materials, low price and wide application prospect besides the reservation of the advantages.

The traditional preparation method of the alkoxy aluminum is to take aluminum chloride and iodine as catalysts and prepare the alkoxy aluminum through the reaction of aluminum powder and alcohol. Impurities can be introduced by adding aluminum chloride and iodine, hydrogen is generated in the reaction process, and potential safety hazards can be brought. The prepared alkoxy aluminum catalyst needs to be added with metal chloride as an auxiliary agent and needs to be dissolved in an organic solvent to prepare a solution with a certain concentration for use, so that the separation difficulty is increased, the reuse is difficult, and the phase change increases the application cost.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a preparation method of an aluminum alkoxide catalyst. The preparation method is simple and convenient to operate, safe and environment-friendly, the prepared catalyst does not need a solvent or an additive in the reaction process of catalyzing disproportionation and condensation of aldehyde to prepare esters, the catalyst and a reaction product are easy to separate, and the catalyst can be repeatedly used. Under the action of the catalyst, the conversion rate of aldehyde can reach more than 95%, and the selectivity of ester can reach more than 92%.

The technical scheme of the invention is as follows:

a preparation method of an aluminum alkoxide catalyst comprises the following steps:

adding aluminum isopropoxide and fatty alcohol into a reactor, heating and refluxing, distilling the isopropanol and the fatty alcohol remained in the reaction in a fractionation mode, and cooling to obtain the corresponding solid alkoxy aluminum catalyst.

Preferred conditions are as follows:

the fatty alcohol is one of isobutanol, n-butanol and isoamylol.

The molar ratio of the aluminum isopropoxide to the fatty alcohol is 1: 3-6.

The heating reflux temperature is 70-110 ℃.

The heating reflux time is 1-6 h.

The alkoxy aluminum catalyst prepared by the method is applied to ester synthesis.

The ester is isobutyl isobutyrate, butyl butyrate or isoamyl isovalerate.

The dosage of the catalyst in the ester synthesis is 0.5-30% of the mass of the reaction substrate; the reaction temperature is-10-70 ℃; the reaction time is 1-24 h.

Preferably, the dosage of the catalyst in the ester synthesis is 5-10% of the mass of the reaction substrate; the reaction temperature is 10-20 ℃; the reaction time is 2-4 h.

The invention has the beneficial effects that: compared with the traditional preparation method of the alkoxy aluminum catalyst, the method takes the aluminum isopropoxide as the raw material, adopts the alcohol generation method to prepare the corresponding alkoxy aluminum catalyst, does not need the catalyst in the preparation process, and avoids the introduction of impurities; no hydrogen is generated, and potential safety hazards are avoided. The catalyst prepared by the invention is a solid heterogeneous catalyst, can be directly used without solvent dissolution in the reaction process, and has higher concentration of the active components of the catalyst actually participating in the reaction system under the same material proportion, so that the extremely high catalytic activity can be ensured without adding an auxiliary agent. The solvent and the auxiliary agent are avoided, so that the cost is saved, and the difficulty of product separation is reduced. In addition, the catalyst can be separated from the reaction system in a relatively mild way (such as filtration or centrifugation) while ensuring high-efficiency catalytic activity, and can be repeatedly used.

Drawings

FIG. 1: example 4 reaction effect diagram;

FIG. 2: example 5 reaction effect diagram;

FIG. 3: example 6 reaction effect diagram;

FIG. 4: example 7 reaction effect diagram;

FIG. 5: example 8 reaction effect diagram;

FIG. 6: example 9 reaction effect diagram.

Detailed Description

The process provided by the present invention is described in detail below with reference to examples, but the present invention is not limited thereto in any way.

Example 1 preparation of an isobutoxy aluminum catalyst:

aluminum isopropoxide and isobutanol are mixed according to a molar ratio of 1:3, adding the mixture into a reactor, heating and refluxing for 1h at 90 ℃, distilling out isopropanol and residual isobutanol in a fractionation mode, and cooling to obtain the solid isobutoxy aluminum catalyst.

Example 2 preparation of a butoxyaluminum catalyst:

aluminum isopropoxide and n-butanol are mixed according to a molar ratio of 1: 4.5, heating and refluxing for 3.5h at 70 ℃, distilling off isopropanol and residual n-butanol in a fractional distillation mode, and cooling to obtain the solid butoxy aluminum catalyst.

Example 3 preparation of an isopentyloxy-aluminum catalyst:

aluminum isopropoxide and isoamyl alcohol are mixed according to a molar ratio of 1: 6, adding the mixture into a reactor, heating and refluxing for 6 hours at 110 ℃, then distilling out isopropanol and isoamylol remained in the reaction in a fractionation mode, and cooling to obtain the solid isopentyloxy aluminum catalyst.

Example 4:

100g of isobutyraldehyde and 0.5g of isobutoxy aluminum catalyst are added into a reactor, and stirred and reacted for 24 hours at 30 ℃. After the reaction was completed, the catalyst was separated by centrifugation, and the composition of each component was analyzed by gas chromatography on the supernatant, and the conversion of isobutyraldehyde was calculated to be 96.34%, and the selectivity of isobutyl isobutyrate was calculated to be 92.67%. The separated catalyst can be reused for many times, and the reaction effect is shown in figure 1.

Example 5:

100g of n-butyraldehyde and 15.25g of an aluminum n-butoxide catalyst were charged into the reactor, and the reaction was stirred at-10 ℃ for 12.5 hours. After the reaction is finished, the catalyst is separated out in a filtering mode, the components of the filtrate are analyzed through gas chromatography, and the conversion rate of n-butyl aldehyde is 95.62% and the selectivity of butyl butyrate is 93.28% through calculation. The separated catalyst can be reused for many times, and the reaction effect is shown in figure 2.

Example 6:

100g of isovaleraldehyde and 30g of isopentyloxy aluminum catalyst are added into a reactor and stirred for reaction for 1 hour at 70 ℃. After the reaction is finished, the catalyst is separated in a centrifugal mode, the components of the supernatant are analyzed through gas chromatography, and the conversion rate of the isovaleraldehyde is 97.19% and the selectivity of the isoamyl isovalerate is 92.06% through calculation. The separated catalyst can be reused for many times, and the reaction effect is shown in figure 3.

Example 7

100g of isobutyraldehyde and 5g of isobutoxy aluminum catalyst are added into a reactor, and stirred and reacted for 4 hours at 15 ℃. After the reaction, the catalyst was separated by filtration, and the composition of each component was analyzed by gas chromatography on the supernatant, and the conversion of isobutyraldehyde was 97.38% and the selectivity of isobutyl isobutyrate was 93.35% were calculated. The separated catalyst can be reused for many times, and the reaction effect is shown in figure 4.

Example 8:

100g of n-butyraldehyde and 7.5g of an aluminum n-butoxide catalyst were charged into the reactor, and the reaction was stirred at 10 ℃ for 3 hours. After the reaction is finished, the catalyst is separated out in a centrifugal mode, the components of the filtrate are analyzed through gas chromatography, and the conversion rate of n-butyl aldehyde is 96.87% and the selectivity of butyl butyrate is 93.89%. The separated catalyst can be reused for many times, and the reaction effect is shown in figure 5.

Example 9:

100g of isovaleraldehyde and 10g of isopentyloxy aluminum catalyst are added into a reactor and stirred to react for 2 hours at the temperature of 20 ℃. After the reaction is finished, the catalyst is separated out in a filtering mode, the components of the supernatant are analyzed through gas chromatography, and the conversion rate of the isovaleraldehyde is 98.07 percent and the selectivity of the isoamyl isovalerate is 92.96 percent through calculation. The separated catalyst can be reused for many times, and the reaction effect is shown in figure 6.

While the methods and techniques of the present invention have been described in terms of preferred embodiments, it will be apparent to those of ordinary skill in the art that variations and/or modifications of the methods and techniques described herein may be made without departing from the spirit and scope of the invention. It is expressly intended that all such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and content of the invention.

Claims

1. A preparation method of an aluminum alkoxide catalyst is characterized in that aluminum isopropoxide and fatty alcohol are added into a reactor, after heating and refluxing, the isopropanol and the fatty alcohol remained in the reaction are distilled out by fractional distillation, and the solid aluminum alkoxide catalyst is obtained by cooling.

2. The method according to claim 1, wherein the aliphatic alcohol is selected from the group consisting of isobutanol, n-butanol, and isoamyl alcohol.

3. The method according to claim 1, wherein the molar ratio of aluminum isopropoxide to fatty alcohol is 1: 3-6.

4. The method according to claim 1, wherein the heating reflux temperature is 70 to 110 ℃.

5. The process according to claim 1, wherein the heating reflux time is 1 to 6 hours.

6. The use of an aluminum alkoxide catalyst prepared by the process of claim 1 in the synthesis of esters.

7. Use according to claim 6, characterized in that said ester is one of isobutyl isobutyrate, butyl butyrate or isoamyl isovalerate.

8. The use according to claim 6, characterized in that the amount of catalyst used in the ester synthesis is 0.5-30% of the mass of the reaction substrate; the reaction temperature is-10-70 ℃; the reaction time is 1-24 h.

9. The use according to claim 6, characterized in that the amount of catalyst used in the ester synthesis is 5-10% of the mass of the reaction substrate; the reaction temperature is 10-20 ℃; the reaction time is 2-4 h.