Well-dispersed sulfated mesoporous WO3/SiO2 hybrid colloidal spheres: High-efficiency catalysts for the synthesis of fatty acid alkyl esters

An effective method in obtaining well-dispersed mesoporous WO3/SiO2 colloidal spheres (WMWCSs) with a specific surface area of 1370 m(2) g (-1), pore volume of 0.84 cm(3) g (-1), and pore size of 2.44 nm was developed. This method allows easy control over the morphology, size and dispersity of the hybrid spheres by the variation of synthetic conditions. The formation mechanism on the as-prepared WMWCSs was proposed as well. Treated with sulfuric acid, the resulted WO3/SiO2 colloidal spheres exhibited excellent catalytic activity in the synthesis of biodiesel via the esterification of long-chain free fatty acids (FFAs). A 96.9% conversion of oleic acid was realized under optimized conditions, 3 wt% of catalyst and 6 h of reaction time, while the catalyst suffered no obvious loss in activity for five consecutive runs. (C) 2015 Elsevier Ltd. All rights reserved.