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

Mesoporous oil palm ash zeolite (OPAZ) was synthesized and impregnated with various lithium ion loadings (5-15 wt%). 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 343 K, 90 min, DMC/glycerol molar ratio of 2, and 2 wt% 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 10 wt% Li loaded OPAZ. Hence, 10 wt% Li-OPAZ was reused in five successive cycles of experiment with sustained appreciable catalytic activity toward glycerol conversion and GC yield.