Synthesis of hybrid SBA-15 functionalized with molybdophosphoric acid as efficient catalyst for glycerol esterification to fuel additives

Abstract

Fibrous mesoporous hybrid silica (SBAH-15) with mesopore diameter of 70Å was synthesized using pluronic P123 (EO20PO70EO20) as surfactant, with Brij S100 as nonionic co-surfactant. Series of catalysts with different molybdophosphoric acid (MPA) loading (5–25%) were synthesized by the thermal decomposition of MPA species in the lattice of SBAH-15. Catalysts calcined at 560°C undergone a thermal decomposition of MPA resulted in the formation of β-MoO3 active species. The effectiveness of the hybrid support was evaluated by comparison with analogous catalyst prepared by incorporating MPA into the framework of classical SBA-15. The catalytic performance of the prepared acid catalysts was examined during glycerol esterification with acetic acid. Mono-, di- and triacetyl glycerol (MAG, DAG and TAG, respectively) were the esterification reaction products. SBAH-15(15) catalyst, with 15wt.% MPA loading, exhibited an excellent activity during this reaction, indicated by the complete glycerol conversion (after 1h) with a corresponding combined selectivity of 86% toward both DAG and TAG. The best reaction conditions are: reaction temperature of 110°C, glycerol to acetic acid molar ratio of 1:6 and reaction time of 3h. The SBAH-15(15) catalyst demonstrated good stability in activity upon recycling for four times.