Method 1: In a 100 mL three-necked flask equipped with a water separator, add a certain amount of maleic anhydride, n-butanol and a catalyst, and place it in a microwave reactor. Set a certain power and a certain microwave time of the microwave reactor to carry out the microwave radiation reflux reaction. After the reaction is completed, wash with distilled water and saturated sodium carbonate solution for several times respectively, dry with anhydrous magnesium sulfate, and after the treatment, the unreacted n-butanol is distilled off by vacuum distillation, and finally the ester fraction is collected to obtain colorless and transparent oily liquid dibutyl maleate. Weigh and calculate the yield according to the following formula. The experimental results show that the optimal synthesis conditions for dibutyl maleate are as follows: the ratio of maleic anhydride to n-butanol is 1:4, and the ionic liquid [HSO3-pmim]+[HSO4]- is used as the catalyst, and the dosage is 2.0g, the microwave power is 600W, the microwave time is 15min, and the yield of dibutyl maleate can reach 99.36%. Under microwave irradiation, the activity of the catalyst ionic liquid [HSO3-pmim] + [HSO4]- did not decrease significantly after repeated use for 7 times, and the yield of dibutyl maleate was still higher than 96%, indicating that the catalyst has a good reaction activity and stability.
Method 2: Add a certain amount of maleic anhydride, n-butanol, catalyst and toluene with water to a three-necked flask equipped with a magnetic stirring bar, a thermometer, a water separator and a condenser, and heat and reflux for a certain period of time. After the reaction was completed, samples were taken to measure the acid value after cooling a little. The change of acid value before and after the reaction was measured by the method of GB1668-81, and the esterification rate was calculated. The experimental results show that Zr(SO4)2/SiO2 is a good catalyst for the synthesis of dibutyl maleate. The suitable catalyst preparation conditions are: zirconium sulfate loading 57%, calcination temperature 400℃, calcination time 2h. The appropriate catalytic synthesis response conditions are as adheres to: the ratio of anhydride to alcohol is 1:2.5, the amount of catalyst is 6% of the mass of maleic anhydride, 8 mL of toluene with water is used, and the reaction time is 2.0 h. Under these conditions, the esterification rate of dibutyl maleate was 98.5%.
Method 3: a synthetic method of dibutyl maleate, the synthetic method adopted is: adding a reaction system composed of maleic anhydride, n-butanol and a catalyst, and using a circulating pump and a heat exchanger for internal circulation heating, The system is evacuated to carry out the reaction; wherein the reaction temperature is 80-130° C., and the reaction time is 3-4 hours. The process flow schematic diagram as shown in Figure 1 is operated, in the reactor, add 98kg maleic anhydride, 111kg n-butanol, 25kg hydrogen type cation exchange resin, heat up, open the condenser, after the solution is clear, open the heat exchange steam, open the bottom valve of the reaction tank, the transfer pump, open the internal circulation, open the condenser and vacuumize, separate the produced water, control the reaction temperature in the tank at 90~125 ° C, react for 4 hours, distill, neutralize, After washing with water, the product was obtained, and the product was detected, and the esterification rate was 99.3%.
