Cu-Ni synergy in physicochemical properties of the Mg-Al oxides matrix to selective glycerol carbonate production

Abstract

Cu-Ni modified Mg-Al-layered double hydroxides were synthesized by coprecipitation and calcined to generate ternary and quaternary mixed metal oxides (MMOs). The materials were physicochemically characterized. Cu-Ni-enhanced MMOs are novel as heterogeneous catalysts in the transesterification reaction between glycerol and an alkyl carbonate to synthesize a platform molecule, glycerol carbonate (GC). This reaction valorizes glycerol, a byproduct in the biodiesel industry. The physicochemical properties and catalytic activities of MMOs were investigated. The quaternary MMO with the lowest Cu-Ni loading (15 at%) showed the best GC yield (84.6 %) under mild reaction conditions. Very-strong basic sites (BS_VS) density was directly proportional to the copper content. The densities of strong basic sites (BS_S) and BS_VS were correlated with glycerol conversion. The high catalytic activity to GC was attributed to adequate surface morphology and a compromise between the amounts of BS_S and BS_VS. The amount of BS_VS should be low enough so that the selectivity to GC does not decrease. The stability of the MMO with the best catalytic behavior was investigated.