Biodiesel byproduct glycerol upgrading to glycerol carbonate over lithium–oil palm ash zeolite

Abstract

Mesoporous oil palm ash zeolite (OPAZ) was synthesized and impregnated with various lithium ion loadings (5–15wt%). The synthesized Li–OPAZ catalyst was used to upgrade biodiesel byproduct glycerol to glycerol carbonate (GC) via transesterification pathway. Results indicated that Li–OPAZ sustained the transesterification reaction to appreciably high glycerol conversion (100%) and GC yield (98.1%) under the optimal reaction conditions of 343K, 90min, DMC/glycerol molar ratio of 2, and 2wt% catalyst loading. The crystallinity and framework of zeolite was preserved after lithium incorporation with a slight decrease in pore volume and surface area. However, basicity increased with increased lithium impregnation, explaining the observed high catalytic activity of the theoretical 10wt% Li loaded OPAZ. Hence, 10wt% Li–OPAZ was reused in five successive cycles of experiment with sustained appreciable catalytic activity toward glycerol conversion and GC yield.