Efficient synthesis of n-butyl-p-hydroxybenzoate preservative with toluene-4-sulfonic acid as catalyst

n-Butyl-p-hydroxybenzoate was synthesized from p-hydroxybenzoic acid and n-butanol with toluene-4-sulfonic acid as catalyst and n-butanol as water entrainer. Effects of molar ratio of p-hydroxybenzoic acid to n-butanol,reaction temperature and reaction time,etc. on the yield of the product were studied.The result showed that the suitable reaction conditions were as follows: based on 0. 02 mole p-hydroxybenzoic acid,n-butanol /p-hydroxybenzoic acid molar ratio of 4 ∶ 1,toluene-4-sulfonic acid /p-hydroxybenzoic acid mass ratio of 0. 12 ∶ 1,reaction temperature 140 ℃,for 3 h reaction time give the highest yield of n-butyl-p-hydroxybenzoate above 99%.