Solid acid catalysts (especially solid superacid catalysts) used in esterification have the advantages of good selectivity, fast reaction speed, high yield, easy separation, convenient operation, stable catalyst, reusable, no corrosion of equipment, no pollution, etc. , is a catalyst with good development prospects. Using citric acid and n-butanol as raw materials, TBC was synthesized under the catalysis of rare earth superacid. The experimental results show that the performance of the catalyst obtained with La content of 0.07mol/L is the best, and the optimal catalytic synthesis conditions of TBC are: reaction temperature 175°C, alkyd-acid molar ratio 4.0:1, catalyst dosage 2.0% of citric acid mass, reaction The time is 180 minutes, and the esterification rate can reach 98.27%. The catalyst can be recycled 5 times without significant loss of activity.
The esterification of citric acid and n-butanol to TBC was catalyzed by solid acid catalyst supported on activated carbon. The optimal reaction conditions are: catalyst dosage 5% (mole fraction), acid-alcohol molar ratio 4.5:1, reaction temperature 140°C, reaction time 3.0h, and the esterification rate can reach over 98%. The catalyst can still maintain a high catalytic activity after being used for 5 times, and the catalyst can be regenerated by adding NaH.sO by spraying. The supported MoO solid superacid catalyst was prepared by slurry impregnation method, and it was used to catalyze the synthesis of TBC from citric acid monohydrate and n-butanol. The results show that with MoO/activated carbon as the catalyst, the catalyst dosage is 8% (w/w), the molar ratio of acid to alcohol is 1:4, the reaction temperature is 140cC, and the reaction time is 3.0h, the esterification rate can reach more than 99%. In addition, the catalyst can be recycled more than 5 times, and the esterification rate remains at a high level.
Ionic liquids have the characteristics of low vapor pressure, low melting point, wide liquid range, easy operation, good solubility and high stability, and have good application prospects as catalysts. Using homopiperidine as the main raw material, tertiary ammonium p-toluenesulfonate ionic liquid 1-(propionyl)homopiperidine p-toluenesulfonate [HMILS]OTs and bis-(1-homopiperidine Pyridyl)butylene bis-p-toluenesulfonate HMIBL[OTs], and used to catalyze the esterification of citric acid and n-butanol. The results showed that: under the conditions of (n-butanol):n(citric acid):n(HMIBL[OTs],)=5:1:0.07, reaction temperature 120°C, reaction time 3.5h, HMIBL[OTs] had the best effect on lemon The conversion rate of acid and the selectivity of Tributyl Citrate are 98.2% and 98.6% respectively. The synthesized ionic liquid catalyst can be recovered after use, and the catalytic activity does not decrease significantly after repeated use for 8 times. Using N-methylimidazolium bisulfate ionic liquid as catalyst, the synthesis reaction of TBC was carried out. The best reaction conditions obtained are: the ratio of butanol to citric acid is 6:1, toluene is the water carrier, the reaction temperature is 110℃, and the reaction time is 7h. The esterification rate of citric acid under this condition is greater than 97%. The catalyst can be reused more than 10 times.
