阅读说明：本技术 一种离子液体催化马来酸酐制备马来酸酯的方法 (Method for preparing maleic acid ester by catalyzing maleic anhydride with ionic liquid ) 是由 刘瑞霞 刘玉梅 张瑞锐 陈圣新 张婷 张锁江 于 2019-11-13 设计创作，主要内容包括：本发明公开了一种离子液体催化马来酸酐制备马来酸酯的方法,其特征在于,包括如下步骤：将离子液体与马来酸酐和脂肪醇混合,加热至80～140℃,反应0.5～4h,获得马来酸酯,所述离子液体用量为马来酸酐的0.1％～10％mol,脂肪醇和马来酸酐的摩尔比为2～12。制备出以完全酯化的马来酸酯为主要产物的高附加值化学品。本发明工艺简单,条件温和,环境友好,双酯化程度高,离子液体活性高且不易失活,可实现循环使用。(The invention discloses a method for preparing maleic acid ester by catalyzing maleic anhydride with ionic liquid, which is characterized by comprising the following steps: mixing ionic liquid with maleic anhydride and fatty alcohol, heating to 80-140 ℃, and reacting for 0.5-4 h to obtain maleic ester, wherein the dosage of the ionic liquid is 0.1-10 mol% of the maleic anhydride, and the molar ratio of the fatty alcohol to the maleic anhydride is 2-12. High value-added chemicals are prepared with fully esterified maleic acid esters as the main product. The method has the advantages of simple process, mild condition, environmental friendliness, high double esterification degree, high activity of the ionic liquid, difficult inactivation and realization of recycling.)

1. The method for preparing maleic ester by catalyzing maleic anhydride with ionic liquid is characterized by comprising the following steps: mixing an ionic liquid with maleic anhydride and fatty alcohol, heating to 80-140 ℃, and reacting for 0.5-4 h to obtain maleic ester, wherein the dosage of the ionic liquid is 0.1-10 mol% of the maleic anhydride, the molar ratio of the fatty alcohol to the maleic anhydride is 2-12, and the structural formula of the ionic liquid is any one of (1) - (5):

n is an integer of 0 to 8; x is any one of Cl, Br and I.

2. The method for preparing maleic ester by catalyzing maleic anhydride with ionic liquid according to claim 1, wherein the heating is microwave heating.

3. The method for preparing maleic ester by catalyzing maleic anhydride with ionic liquid according to claim 1, wherein the aliphatic alcohol is at least one of methanol, ethanol, n-butanol, isobutanol, n-octanol, isooctanol, n-nonanol, and 1, 4-dibutanol.

4. The method for preparing maleic ester by catalyzing maleic anhydride with ionic liquid as claimed in claim 1, wherein the structural formula of the ionic liquid is (1) or (2),

n is an integer of 0 to 8.

5. The method for preparing maleic ester by catalyzing maleic anhydride with ionic liquid according to claim 1 or 4, wherein n is 3 or 4.

6. The method for preparing maleic ester by catalyzing maleic anhydride with ionic liquid according to claim 1 or 3, wherein the aliphatic alcohol is at least one of methanol, ethanol and butanol.

7. The method for preparing maleic ester by catalyzing maleic anhydride with ionic liquid as claimed in claim 1, wherein the amount of the ionic liquid is 0.5-2 mol% of the maleic anhydride.

8. The method for preparing maleic ester by catalyzing maleic anhydride with ionic liquid according to claim 1, wherein the molar ratio of the fatty alcohol to the maleic anhydride is 3-6.

9. The method for preparing maleic ester by catalyzing maleic anhydride with ionic liquid according to claim 1, wherein the heating is performed to 110-130 ℃.

10. The method for preparing maleic ester by catalyzing maleic anhydride with ionic liquid according to claim 1, wherein the reaction time is 45 min-1.5 h.

Technical Field

The invention relates to the technical field of chemical product preparation, in particular to a method for preparing maleic acid ester by catalyzing maleic anhydride with ionic liquid.

Background

Maleic anhydride is a commonly used important basic organic chemical raw material. Is the third largest anhydride feedstock second only to acetic anhydride and phthalic anhydride in the world. The maleic anhydride has wide source, can be prepared by benzene oxidation method, butylene oxidation method, butane oxidation method, phthalic anhydride byproduct method and other methods which take fossil raw materials as the basis, and can also be obtained by fermentation and catalytic conversion of biomass raw materials (such as cellulose). Maleic anhydride is used as a platform compound, and can be used for producing various chemical products with high added values, such as 1, 4-butanediol, tetrahydrofuran, gamma-butyrolactone, maleic acid ester and the like. Therefore, the research on the conversion of maleic anhydride has received extensive attention from both academic and industrial fields.

As an organic synthesis intermediate, maleic esters undergo addition reactions mainly at double bonds. Such as with butadiene, cyclopentadiene, etc., by addition of active hydrogen-containing compounds such as hydrogen, nitriles, thiols, amines, etc., such as by addition of sodium bisulfite, to produce the well-known surfactant dialkyl succinate sulfonates. The other ammonia or amines are added to the maleic acid ester and aminolyzed to cause amidation (imidization), that is, act as an acylating agent. Diethyl maleate has wide application, is also used as an intermediate for producing pesticides and medicines such as high-efficiency insecticide malasone and the like, and can also be used for producing high molecular compounds; dimethyl maleate, dibutyl ester and dioctyl ester are excellent plasticizers of PVC; and can be copolymerized with monomers such as vinyl chloride, vinyl acetate and the like, and can be used as a coating, an adhesive, a impregnant for papermaking, fabrics and the like, a dispersing agent, a lubricating agent and the like; diisooctyl maleate and dinonyl maleate are good pour point depressants for petroleum.

The esterification of maleic anhydride is mainly carried out in two steps, wherein the first step is a mono-esterification reaction, such as equation (1), the reaction in the step is easy to carry out, and the reaction can be converted at room temperature without any catalyst; the second step is a double esterification reaction, as in equation (2), which is a reversible reaction and requires an acid catalyst for further conversion.

In the traditional production method of the maleate, sulfuric acid is mainly used as a catalyst, and although the sulfuric acid has high catalytic activity and low price, the defects of more side reactions, easy isomerization of products into fumarate, serious corrosion of equipment, complex subsequent treatment and the like exist; in patent nos. CN106631784A and CN206204188U, strong acidic ion exchange resins are used as solid catalysts, and although these catalysts have little corrosion to equipment, the regeneration process of ion exchange resins is complicated, secondary pollution is easy to occur, complete regeneration is difficult, and the reusability of the resins is low.

Disclosure of Invention

The invention aims to provide a method for preparing maleic acid ester by catalyzing maleic anhydride with an ionic liquid so as to realize an efficient and energy-saving process for efficiently catalyzing and synthesizing maleic acid ester.

The invention provides a method for preparing maleic ester by catalyzing maleic anhydride with ionic liquid, which comprises the following steps: mixing an ionic liquid with maleic anhydride and fatty alcohol, heating to 80-140 ℃, and reacting for 0.5-4 h to obtain maleic ester, wherein the dosage of the ionic liquid is 0.1-10 mol% of the maleic anhydride, the molar ratio of the fatty alcohol to the maleic anhydride is 2-12, and the structural formula of the ionic liquid is any one of (1) - (5):

n is an integer of 0 to 8; x is any one of Cl, Br and I.

Compared with the prior art, the invention has the beneficial effects that: the maleic anhydride ester is prepared by ionic liquid catalysis, so that the problems of corrosion of traditional liquid acid equipment, complex subsequent treatment and difficult regeneration of solid ion exchange resin are effectively solved. Under the catalysis of the ionic liquid, the maleic anhydride keeps better conversion rate and double esterification selectivity, the conversion rate of the maleic anhydride is 90-99%, and the yield of the maleic ester reaches 80-95%. In addition, the method can separate the product from the ionic liquid only by simply distilling the product under reduced pressure, thereby realizing the regeneration of the ionic liquid.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The embodiment of the invention provides a method for preparing maleic ester by catalyzing maleic anhydride with ionic liquid, which comprises the following steps: mixing an ionic liquid with maleic anhydride and fatty alcohol, heating to 80-140 ℃, and reacting for 0.5-4 h to obtain maleic ester, wherein the dosage of the ionic liquid is 0.1-10 mol% of the maleic anhydride, the molar ratio of the fatty alcohol to the maleic anhydride is 2-12, and the structural formula of the ionic liquid is any one of (1) - (5):

n is an integer of 0 to 8; x is any one of Cl, Br and I.

In particular, the heating is microwave heating. The aliphatic alcohol is at least one of methanol, ethanol, n-butanol, isobutanol, n-octanol, isooctanol, n-nonanol and 1, 4-dibutanol. Preferably, the aliphatic alcohol is at least one of methanol, ethanol and butanol.

Preferably, the dosage of the ionic liquid is 0.5 to 2 mol percent of the maleic anhydride. The molar ratio of the fatty alcohol to the maleic anhydride is 3-6.

More preferably, the temperature is heated to 110-130 ℃ and the reaction lasts for 45 min-1.5 h.

Specifically, the sulfonic acid functionalized ionic liquid in the ionic liquids (1) and (2) is prepared through two steps: a. dissolving methylimidazole or pyridine in ethanol, putting the ethanol into an oil bath kettle at 70 ℃ for preheating, dropwise adding sultone under magnetic stirring, wherein sultone is slightly excessive, and continuously stirring for 8 hours after dropwise adding is finished to obtain an intermediate product (sulfonic acid functionalized inner salt). After the reaction is finished, washing the intermediate product with diethyl ether for 3-5 times to remove unreacted raw materials, and then putting the intermediate product into a vacuum drying oven to dry for 12 hours at 80 ℃. b. And adding the intermediate product into a round-bottom flask, dissolving the intermediate product with a proper amount of deionized water, preheating the intermediate product at 70 ℃, then dropwise adding concentrated sulfuric acid into the flask, continuously stirring the mixture for 10 hours, washing the mixture for 3-5 times with acetone to remove unreacted inner salt, and performing vacuum drying at 80 ℃ for 12 hours to obtain the sulfonic acid functionalized hydrogen sulfate acidic ionic liquid. The ionic liquids (3) and (5) are prepared by one-step reaction: adding methylimidazole into a round-bottom flask, dissolving with a proper amount of deionized water, preheating at 70 ℃, then dropwise adding halogen acid (such as hydrochloric acid) or concentrated sulfuric acid into the flask, carrying out neutralization reaction, continuing stirring for 10 hours, washing for 3-5 times with acetone to remove unreacted raw materials, and carrying out vacuum drying for 12 hours at 80 ℃ to obtain the acidic ionic liquid with cation and proton. The ionic liquid (4) can be prepared by a two-step method: a. taking 3-4 g of 1-R-group-3-methylimidazole halide salt (such as 1-ethyl-3-methylimidazole chloride salt) into a flask, dissolving the flask with deionized water, and replacing chloride ions with hydroxide ions by using anion exchange resin to obtain an aqueous solution containing an intermediate product; and (3) titrating the concentration of the intermediate product in the aqueous solution by using potassium hydrogen phthalate as a titrant and phenolphthalein as an indicator. b. And (3) taking an appropriate amount of the aqueous solution obtained in the step a, slowly dropwise adding concentrated sulfuric acid with an equimolar amount into the solution, continuously stirring for 10 hours, removing the solvent by rotary evaporation, and performing vacuum drying at 80 ℃ for 12 hours to obtain the acidic ionic liquid with the anion of the bisulfate radical.

Preferably, the ionic liquid has the structures (1) and (2),

n is an integer of 0 to 8.

When the catalysts are ionic liquids (1) and (2), cations in the sulfoacid methyl imidazole hydrogen sulfate ionic liquid in (1) and the sulfoacid pyridine hydrogen sulfate ionic liquid in (2) are both acidified by sulfonic acid groups, and meanwhile, anions are also hydrogen sulfate with stronger acidity, so that the ionic liquid is stronger in acidity and more beneficial to reaction. The esterification of maleic anhydride to obtain dimethyl maleate needs two steps of esterification, the ring opening reaction in the first step is easy, the maleic anhydride and methanol are mixed and placed for a period of time to partially open the ring, but in the second step of esterification, the esterification can be further carried out only by catalysis of a catalyst. The strong acid catalyst is beneficial to reducing the activation energy of the second esterification reaction and accelerating the reaction rate. When the value of n is taken, n is preferably 3 or 4, because propyl sultone and butyl sultone are more susceptible to ring opening and have higher ring tension than six-membered or more-membered lactones.