Production of Biodiesel from Castor Oil Using Imidazolium Based Acidic Ionic Liquid Catalyst

Abstract

The world’s population is exponentially increasing so is the energy demand. Fossil resources are depleting at a faster pace. Not only they are not enough to meet the requirements but also they are emitting harmful emissions. Green approach is to use biodiesel which is more environmental friendly. In this study, castor biodiesel was prepared by using acidic ionic liquids i.e., 1-vinyl-3-(sulfopropyl) imidazolium hydrogen sulfate [VSIM][HSO4] and modified 1-vinyl-3-ethylimidazolium bromide (VEtImBr) as catalysts. pH was measured to determine the acidity of catalysts. These catalysts were synthesized and used in the transesterification by using different reaction conditions (reaction time, oil methanol ratio, catalyst concentration, and temperature). Physicochemical parameters of oil and castor biodiesel were measured. TGA, FTIR, and GC-MS analysis were done. Modified VEtImBr showed a maximum biodiesel yield of 99.8%. Optimum conditions were 60 min reaction time, 6 wt% catalyst concentration, 1:06 oil methanol ratio, and 60 ℃ temperature. The acidity of catalysts was compatible with the inorganic acids (pH is 1.5 and 1.6 of [VSIM][HSO4] and modified VEtImBr, respectively). All physicochemical parameters were within range except iodine value and density. TGA analysis showed that modified VEtImBr is more thermally stable (up to 270 ℃) than [VSIM][HSO4] (up to 235 ℃). FTIR analysis showed characteristic peaks confirming the chemical structure. GC-MS showed that ricinoleic acid, palmitic acid, and phthalic acid are prominent in castor oil. Ricinoleic acid methyl ester, palmitic acid methyl ester, linoleic acid methyl ester and oleic acid methyl ester were the main constituents of biodiesel.