Transesterification of dimethyl carbonate with glycerol by perovskite-based mixed metal oxide nanoparticles for the atom-efficient production of glycerol carbonate

Abstract

The catalytic transesterification of glycerol with dimethyl carbonate (DMC) is an attractive process for the valorization of glycerol, an abundant waste product of the biodiesel industry, by its transformation in industrially attractive glycerol carbonate (GC). Interestingly, perovskites and perovskite-based mixed metal oxides (PBMMOs) were, thus far, only marginally explored for the latter reaction. In this work, a series of PBMMOs were prepared using the non-hydrolytic sol gel (NHSG) methodology as an approach to easily afford nanosized and non-aggregated ternary oxides without calcination steps. The prepared materials were characterized via TEM and SEM microscopies, XRD analysis, XPS, BET surface area and TPD measurements showing that the as-synthesized PBMMOs displayed higher surface areas and larger number of crucial strong basic sites than their analogues produced by calcination at 1000 °C. The catalytic activity of as-synthesized or calcined PBMMOs followed a clear linear trend as a function of the materials basicity with the most basic PBMMOs (SrTiO3-200, YNbO4-200 and BaCeO3-200) performing as the most active catalysts. Selected materials on the basis of catalytic performance and low metal toxicity (SrTiO3-200, YNbO4-200) were subsequently applied to improve the atom economy of the transesterification reaction using low (1:2 or 1:1.5) DMC/glycerol ratios and even equimolar amounts of reagents. Under optimized conditions, the use of SrTiO3-200 as the catalyst allowed the quantitative and selective conversion of glycerol to GC by using 1:2 DMC/glycerol ratio and could be efficiently recycled maintaining at least 95% GC yield at the fifth catalytic run. Albeit slightly less active than SrTiO3-200, YNbO4-200 performed well when working with equimolar DMC/glycerol ratio allowing glycerol conversion and GC yield over 80%.