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 (BSVS) density was directly proportional to the copper content. The densities of strong basic sites (BSS) and BSVS were correlated with glycerol conversion. The high catalytic activity to GC was attributed to adequate surface morphology and a compromise between the amounts of BSS and BSVS. The amount of BSVS 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.