Preparation of Citrullus colocynthis biodiesel via dual-step catalyzed process using functionalized imidazolium and pyrazolium ionic liquids for esterification step

In this research, dual step catalyzed process was implemented to prepare biodiesel from crude Citrullus colocynthis oil (CCO). Two ionic liquids (ILs) were synthesized and evaluated as pre-catalyst for the FFA-esterification first step. A 1-methyl-3-(4-sulfobutyl)-imidazolium hydrogensulfate (MSBIMHSO4) showed a higher FFA conversion than the pyrazolium IL of 1-methyl-2-(4-sulfobutyl)-pyrazolium hydrogensulfate (MSBPHSO4). A 96.7% FFA conversion was achieved at the optimal conditions of 3.8 wt% of MSBIMHSO4, molar ratio of 12:1 methanol:CCO, 130 degrees C, and 600 rpm agitation rate for 2 h. In the second step, KOH-transesterification reaction of the esterified CCO was performed at 60 degrees C, 6:1 mole ratio of methanol:oil, and 600 rpm in a reaction system containing 1.0 wt% of catalyst for 50 min. The final yield in 98.8% revealed that the process proposed for novel CCO in this study led to a tolerable biodiesel, meeting the ASTM requirements for its utilization as a fuel. Furthermore, this new dual step catalyzed process could solve the old homogeneous-catalyzed processes drawbacks. (C) 2013 Elsevier B.V. All rights reserved.