Synthesis and performance evaluation of silica-supported copper chromite catalyst for glycerol dehydration to acetol

Abstract

Sol-gel technique was used to prepare silica-supported copper chromite catalyst from acid hydrolysis of sodium silicate. The catalyst was characterized by BET surface area, FESEM, XRD, H2-TPR and pyridine adsorption by FTIR. The catalyst was activated in a hydrogen atmosphere based on H2-TPR result. The surface acidity of the catalyst was evaluated by NH3-TPD and pyridine adsorption. XRD result of reduced catalyst showed the presence of Cu0, Cu1+ and Cr2O3 in the catalyst. Glycerol dehydration was carried out at different temperature (180 °C to 240 °C) from aqueous glycerol solution with the reduced catalyst in a batch reactor. The glycerol conversion was reached 100% with maximum acetol selectivity of 70% for highest Copper chromite loaded (40 wt%) on silica at 220 °C in atmospheric pressure. The distilled liquid product was analyzed by high-performance liquid chromatography. Oxidized catalyst and spent catalyst showed lower glycerol conversion with low acetol selectivity than the reduced form of the catalyst. This is due to the cuprous ion in the reduced form of the catalyst, which acts as Lewis acid sites in glycerol dehydration. Glycerol dehydration to acetol with reduced form of silica-supported copper chromite catalyst is reported. The reduced form of copper chromite (cuprous oxide) on silica surface acts as a lewis acid in glycerol dehydration. Cuprous oxide coordinates with terminal hydroxyl group of glycerol and forms low energy six-membered transition state in the dehydration reactions.