Synthesis of dimethyl carbonate from ethylene carbonate and methanol using immobilized ionic liquid on amorphous silica

Ionic liquid immobilized on mesoporous amorphous silica was prepared from the coupling of 1-(triethoxysilylpropyl)-3-n-alkyl-imidazolium halides with tetraethyl orthosilicate (TEOS) through template-free condensation under strong acidic conditions. The immobilized 1-n-butyl-3-methyl imidazolium bromide ionic liquid on amorphous silica (BMImBr-AS) was characterized by EA, N2 adsorption, FT-IR, 13C NMR and 29Si NMR. The immobilized amount of IL was 1.27 mmol/g-SiO2 and surface area was 652 m2/g with bimodal distribution of pores. The average pore diameter was 3.3 and 24.6 nm, respectively. The silica-supported ionic liquids were proved to be an effective heterogeneous catalyst for the synthesis of dimethyl carbonate (DMC) from transesterification of ethylene carbonate (EC) with methanol. High temperature, high carbon dioxide pressure, and longer reaction time were favorable for the reactivity of BMImBr-AS. The catalyst can be reused for the reaction up to three consecutive runs with a slight decrease of its catalytic activity.