Preparation of biodiesel in subcritical methanol catalyzed by acidic dication ionic liquid

Abstract

The acidic dication ionic liquid C3MS was prepared and then was applied in the preparation of biodiesel from soybean oil or waste cooking oil in subcritical methanol. The effects of the reaction temperature and reaction time on the biodiesel yield were investigated and the chemical components of products were analyzed with GC‐MS. The results showed that the catalyst had exhibited a highly effective catalytic activity and strong stability. The yield of biodiesel from soybean oil under optimum conditions was up to 98% and it could be maintained at 93.7% even if the catalyst had been reused for seven times. Under the same condition, the yields of biodiesel from four kinds of waste cooking oil were more than 92%, and the highest yield could reach up to 97.2%. The results of GC‐MS showed that the main components of products were methyl ester of palmitic acid, oleic acid, linoleic acid, stearic acid and ricinoleic acid, and the total content of fatty acid methyl esters (FAME) was more than 99% (except from LRO). In addition, the content of water, free fatty acid and the degree of unsaturation would slightly lower the yield of biodiesel. In a word, the dication ionic liquids could be regarded as a potential catalyst for the biodiesel preparation. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 571–576, 2017