Study On Synthesis Of Nipagin Esters

As safe preservatives with high efficiency, Nipagin esters are widely used in food and medicine fields. In this thesis, the synthesis of Nipagin esters from the esterification reaction of p-hydroxybenzoic acid by ethanol/n-butanol was investigated, where concentrated sulphuric acid and NKC9 resin were selected as catalyst respectively. The products were analyzed qualitatively with FTIR and melting points method.Effects of resin pretreatment, resin type, molar ratio of alcohol to acid, catalyst amount and reaction time on esterification yield were systemically studied. The experiment results indicated that concentrated sulphuric acid is a more active catalyst as compared with NKC9 resin in the synthesis of Nipagin esters, while a similar esterification yield and better product property can achieved by NKC9 resin catalyst.By orthogonal experiment technology, the optimal reaction conditions were obtained as follows: (1) Synthesis of Nipagin esters with NKC9 resin catalyst, the molar ratio of alcohol to p-hydroxybenzoic acid =5:1, the weight of catalyst to p-hydroxybenzoic acid =15%, the reaction time=6h. Under this condition, the yields of ethyl Nipagin ester and butyl Nipagin ester are 87.7% and 88.5%, respectively. (2) Synthesis of Nipagin esters with concentrated sulphuric acid catalyst, the molar ratio of alcohol to p-hydroxybenzoic acid =5:1(ethyl Nipagin ester) and 6:1 (butyl Nipagin ester), the weight of catalyst to p-hydroxybenzoic acid =3%, the reaction time=4h. Under this condition, the yields of ethyl Nipagin ester and butyl Nipagin ester are 85.3% and 90%, respectively.