阅读说明：本技术 一种马来酸二乙酯催化加氢合成乙醛酸乙酯的方法 (Method for synthesizing ethyl glyoxylate by catalytic hydrogenation of diethyl maleate ) 是由 范立耸 牟通 赵晶 付松 李俊平 于 2020-08-17 设计创作，主要内容包括：本发明公开了一种催化加氢合成乙醛酸乙酯的方法,以马来酸二乙酯为原料,经臭氧氧化后,再由石墨烯负载的钯钼催化作用下,加氢得到乙醛酸乙酯。本发明催化剂具有很高的活性,可重复利用,并可用于连续的固定床或间歇的釜式反应器。(The invention discloses a method for synthesizing ethyl glyoxylate through catalytic hydrogenation. The catalyst of the present invention has high activity, may be reused and may be used in continuous fixed bed reactor or intermittent kettle reactor.)

1. A method for synthesizing ethyl glyoxylate is characterized by comprising the following steps: and (3) carrying out ozone oxidation on diethyl maleate to obtain an intermediate solution, and carrying out hydrogenation under the action of a graphene-loaded palladium-molybdenum catalyst to obtain ethyl glyoxylate.

2. The method according to claim 1, wherein the graphene-supported palladium-molybdenum catalyst comprises 0.1-15 wt%, preferably 0.5-5 wt% of the raw material graphite oxide of graphene, and the molar ratio of palladium element to molybdenum element is 1:0.1-0.5, preferably 1: 0.2-0.3.

3. The method according to claim 1 or 2, wherein the graphene supported palladium-molybdenum catalyst is prepared by a method comprising:

1) placing the graphite oxide in deionized water for ultrasonic dispersion,

2) then adding palladium salt and molybdenum salt, wherein the mass of palladium element contained in the palladium salt is 0.1-15 wt% of the mass of graphite oxide, and the molar ratio of the palladium element in the palladium salt to the molybdenum element in the molybdenum salt is 1: 0.1-0.5;

and (3) adjusting the pH value to 5-6.5 by using sodium hydroxide, adding excessive sodium borohydride relative to graphite oxide to react, washing and drying to obtain the catalyst.

4. The method according to claim 3, wherein the palladium salt is selected from one or more of palladium nitrate, palladium acetate, palladium chloride and chloropalladic acid, and the molybdenum salt is selected from one or more of molybdenum pentachloride, molybdenum acetate and ammonium molybdate.

5. The method according to any one of claims 1 to 4, wherein the ozone oxidation reaction uses ethyl acetate as a solvent, and the mass ratio of ethyl acetate to diethyl maleate is 5-15: 1, preferably 8-10: 1; the reaction temperature is 20-25 ℃.

6. The process according to any one of claims 1 to 5, wherein the hydrogenation reaction is carried out continuously or in batch.

7. The method as claimed in any one of claims 1 to 6, wherein the hydrogenation reaction is a continuous reaction, the catalyst is loaded on a fixed bed reactor, the catalyst is pretreated for 2 to 4 hours at 50 to 100 ℃ under a hydrogen atmosphere, and then the intermediate solution is added to react while keeping hydrogen introduced.

8. Process according to claim 7, characterized in that the reaction temperature is 10-35 ℃, preferably 20-25 ℃, the pressure is 0.5-7.0MPa, preferably 3-5MPa, the molar ratio of hydrogen to the initial diethyl maleate is 2-20, preferably 8-12, and the liquid hourly space velocity of the intermediate solution is 0.5-2.0h^-1。

9. The method according to any one of claims 1 to 6, wherein the hydrogenation reaction is a batch reaction, and the intermediate solution is charged into a high-pressure reactor, the catalyst is added, and N is used₂And (4) replacing the reaction kettle, and then adding hydrogen for reaction.

10. The process according to claim 9, characterized in that the reaction temperature is 10-35 ℃, preferably 20-25 ℃, the pressure is 0.5-7MPa, preferably 4-6MPa, the reaction time is 2-8h, and the catalyst is used in an amount of 2-10%, preferably 3-5% by mass of the intermediate solution.

The technical field is as follows:

the invention relates to a method for preparing ethyl glyoxylate through catalytic hydrogenation, in particular to a method for preparing ethyl glyoxylate through selective catalytic hydrogenation by using diethyl maleate as a starting material and using palladium-molybdenum loaded by graphene as a catalyst after ozone oxidation.

Background art:

ethyl glyoxylate is an important intermediate raw material of industrial products such as spices, medicines, dyes, plastics and the like, and plays a great role in producing vanillin, ethyl vanillin, allantoin, p-hydroxyphenylglycine and p-hydroxyphenylacetamide.

The synthesis process of ethyl glyoxylate is more, but the problems of low raw material purity, more treatment steps and more waste liquid exist generally. Compared with the prior art, the process of the hydrogenation reduction method after the diethyl maleate is oxidized by the ozone is cleaner, and meets the current requirements of environmental protection. The key technology of the method lies in the development of a catalyst in the hydrogenation process. The catalysts used are, for example, palladium on activated carbon and palladium on alumina, as are known from the literature "studies on the synthesis of ethyl and n-butyl glyoxylate by ozonation". However, the existing catalyst has poor stability, and palladium is easy to agglomerate; the yield and purity of the product are not high enough.

The invention content is as follows:

in order to solve the problems of poor catalyst stability, low product yield and the like in the existing process for preparing ethyl glyoxylate by hydrogenating and reducing diethyl maleate after ozone oxidation, a novel catalyst is provided, and the catalyst is applied to the process, so that the stability of the catalyst can be obviously improved, and the product yield can be improved.

The technical scheme adopted by the invention is as follows:

the research shows that the existing palladium/activated carbon and palladium/alumina have local overheating phenomenon during the use process, which causes adverse effect on the yield and purity of the product. Based on the above, the invention provides a graphene-loaded palladium-molybdenum catalyst, wherein graphene is used as a material with excellent heat conductivity, and the graphene is used as a carrier to uniformly absorb and release reaction heat; the large specific surface area of the graphene can enable the active component palladium to be better dispersed on the carrier, and reduce the generation of palladium agglomeration, so that the catalyst with high dispersion, high activity and high stability is obtained. In addition, molybdenum is introduced into the catalyst of the system for the first time, and the metal and palladium have a synergistic effect, so that the reaction activity can be further improved.

The graphene-supported palladium-molybdenum catalyst provided by the invention has the advantages that the content of palladium element accounts for 0.1-15 wt%, preferably 0.5-5 wt% of the raw material graphite oxide of graphene, and the molar ratio of the palladium element to the molybdenum element is 1:0.1-0.5, preferably 1: 0.2-0.3.

The preparation method of the graphene supported palladium-molybdenum catalyst comprises the following steps:

1) placing graphite oxide in deionized water, ultrasonic dispersing for 1-2h,

2) then adding palladium salt and molybdenum salt, wherein the palladium salt can be one or more of palladium nitrate, palladium acetate, palladium chloride and chloropalladic acid, the molybdenum salt can be one or more of molybdenum pentachloride, molybdenum acetate and ammonium molybdate, the mass of palladium element in the palladium salt is 0.1-15 wt% of the mass of graphite oxide, and the molar ratio of the palladium element in the palladium salt to the molybdenum element in the molybdenum salt is 1: 0.1-0.5;

dropwise adding a sodium hydroxide solution to adjust the pH value to 5-6.5, stirring for 0.5-4h, adding excessive sodium borohydride relative to graphite oxide, reacting for 6-12h at normal temperature, washing with an ethanol water solution, and drying the obtained sample in a freeze dryer for 10-15h at (-15-10 ℃ C., 1-10 Pa) to obtain the catalyst.

The invention also relates to application of the catalyst in catalyzing diethyl maleate to prepare ethyl glyoxylate. For example:

firstly, dissolving a certain amount of diethyl maleate in an ethyl acetate solvent, wherein the mass ratio of ethyl acetate to diethyl maleate is (5-15): 1, preferably 8-10:1, introducing an ozone/oxygen mixed gas (ozone accounts for 5-12 wt%, preferably 8 wt%) until diethyl maleate is completely oxidized to obtain an intermediate solution, and carrying out the reaction at 20-25 ℃ and normal pressure;

and then carrying out catalytic hydrogenation on the intermediate solution under the action of the graphene-loaded palladium-molybdenum catalyst to obtain ethyl glyoxylate. Wherein, the hydrogenation process can adopt a continuous fixed bed reaction and an intermittent kettle type reaction;

when a continuous fixed bed reaction is employed, the specific method is preferably as follows: the catalyst is filled in a fixed bed reactor, the catalyst is pretreated for 2 to 4 hours at the temperature of between 50 and 100 ℃ in a hydrogen atmosphere, and then the intermediate solution is added under the condition of keeping the introduction of hydrogen. The reaction temperature is 10-35 deg.C, preferably 20-25 deg.C, the pressure is 0.5-7.0MPa, preferably 3-5MPa, the molar ratio of hydrogen to initial diethyl maleate is 2-20, preferably 8-12, and the liquid hourly space velocity of the intermediate solution is 0.5-2.0h^-1。

When a batch reaction is employed, the specific method is preferably as follows: loading the intermediate solution into a high-pressure reactor, adding the catalyst of the invention, and using N₂Adding hydrogen after the replacement reaction kettle, and reacting for 2-8h under the conditions that the temperature is 10-35 ℃, preferably 20-25 ℃ and the pressure is 0.5-7MPa, preferably 4-6MPa, wherein the dosage of the catalyst is 2-10 percent, preferably 3-5 percent of the mass of the intermediate solution.

After the reaction is finished, the catalyst in the batch reaction can be recovered by filtration; and separating and purifying the product by a rectification mode.

The invention has the beneficial effects that:

the catalyst of the invention has high activity and stability and can be recycled. Compared with the traditional catalyst, the catalyst has higher product yield which can reach more than 97 percent. In addition, the catalyst can be used in both continuous fixed bed reactors and batch tank reactions.

The specific implementation mode is as follows:

in order to better understand the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples.