Recent advances in bio-glycerol valorization to glycerol carbonate by heterogenous base-catalyzed transesterification

Abstract

World biomass valorization has been tremendously boosted by the production of biofuels like biodiesel and hence bio-glycerol, and the bio-glycerol produced can be modified to produce a plethora of useful derivatives. In particular, glycerol carbonate (GLC) is considered one of the most important value-added products due to its many applications in the pharmaceutical and cosmetic industries and others. In this review, we describe heterogeneous catalytic synthetic routes designed to maximize glycerol conversion (GC) and GLC selectivity. Notably, heterogeneous base-catalyzed carboxylation (transesterification) between glycerol and dimethyl carbonate has been identified as a safer and economically viable means of synthesizing GLC. Particularly, alkali and alkaline metal oxide-based hybrid base catalysts are the best candidates for GLC production. Additionally, waste-derived base catalysts are preferred to make sure the process is more cost-effective. Also, only the appropriate amount of basic active sites ends up in the carboxylation of glycerol successfully with methanol as the only side-product. Otherwise, exorbitant basic sites might lead to GLC decomposition to glycidol and reduce GLC selectivity. Later, kinetic and thermodynamic considerations along with TOFs and E-factors are also discussed to provide insight into reaction pathways. This study provides a summary of recent literature on the large-scale production of GLC and of studies on waste-derived solid catalysts, which make the process more cost-effective.In a nutshell, we highlight the environmental and cost benefits conferred by the use of bifunctional efficient heterogeneous catalysts to subsequently produce biodiesel and GLC using coupling transesterification reactions that produce and valorize glycerol simultaneously.