Synthesis And Process Optimization Of Dodecyl Nipagin Ester

Nipagin ester(also called as paraben or p-hydroxybenzoate esters), a wide-spectrum, high-effective and safe food preservative, is recognized as main food preservatives internationally, which is widely used in food industries, cosmetics industries and pharmaceutical industries. Currently, with the demand of Nipagin esters in increasing at home and abroad, the research on preparation of Nipagin esters have become a hot topic. Ethyl paraben, propyl paraben and butyl paraben has been domestically widely used as food preservative, whereas parabens with longer alcohol group represented as dodecyl nipagin ester have not been manuafactured and industrialied. The research showed that the more of the number of carbon atoms of alcohol in nipagin ester, the stronger of the antibacterial effect, and the smaller of the toxicity. It can be seen that the studies of the synthesis of dodecyl nipagin ester is necessary.This paper mainly studied on the catalytic synthesis of dodecyl nipagin ester. The dodecyl nipagin ester was synthesized using p-hydroxy benzoic acid and dodecyl alcohol as reactant, with the catalyst of concentrated sulfuric acid, vitamin C, aminosulfonic acid and ionic liquids([Hmim]+BF4-). The structure of the title product was confirmed by IR spectrum, Elemental analysis. The effect of variety of catalyst, molar ratio of alcohol to acid, reaction time, reaction temperature, the dosage of catalyst and the reuse of catalyst on esterification yield had been investigated. Furthermore, the yield of product is optimized by orthogonal experimental method and response surface methodology,and the feasibility of the optimum conditions was verified by repeating test and amplification experiments. With the catalyst of concentrated sulfuric acid, molar ratio of alcohol to acid was 1:1.2, reaction temperature was 110℃, reaction time was 8h and the dosage of catalyst was 30% of the amout of acid, the yield of product was more than 84.6%. With the catalyst of vitamin C, molar ratio of alcohol to acid was 1:1.2, reaction temperature was 100℃, reaction time was 6h and the dosage of catalyst was 15% of the amout of acid, the yield of product was more than 92.3%. With the catalyst of aminosulfonic acid, molar ratio of alcohol to acid was 1:1.2, reaction temperature was 100℃, reaction time was 6h and the dosage of catalyst was 10% of the amout of acid, the yield of product was more than 94.9%. With the catalyst of ionic liquids([Hmim]+BF4-), molar ratio of alcohol to acid was 1:1.1, reaction temperature was 80℃, reaction time was 4h and the amount of ionic liquid equaling 8(wt.) times of reacting p-hydroxy benzoic acid, the yield was about 95.3%.In the repeating test of vitamin C, aminosulfonic acid and ionic liquids([Hmim]+BF4-), the catalyst can be recovered many times without treatment, and the reduction of catalytic activity was less. The experiments showed that the reason to the reduce of catalyst activity was the mechanical losses in the recycling process, the increased of catalytic activity with the new catalyst system was considerably if adding of amount of catalyst is appropriate. This is a good solution to shortcomings which were the product was separated difficulty, the post-processing was complex, amount of catalyst was large and environmental pollution in a traditional process. This paper has an important guiding significance for the application of catalyst in esterification reaction.