Facile, low-cost, and scalable fabrication of particle size and pore structure tuneable monodisperse mesoporous silica nanospheres as supports for advanced solid acid catalysts

Abstract

Monodisperse mesoporous silica nanospheres (MSN) have been emerging as one of the new frontiers in materials science and nanotechnology because of their potential medical and biological applications as well as heterogeneous catalysis. Although the synthesis of MSN with various morphologies and sphere size has been reported, the synthesis of MSN with monodisperse control below 200 nm by a facile, scalable and low-cost method with high tetraethylorthosilicate (TEOS) concentration still remains a challenge. Herein, this goal was achieved by a templating hydrothermal technique using cetyltrimethylammonium bromide (CTAB) as the templating surfactant and low-cost urea as mineralizing agent. The mesoporous feature and diameter of nanosphere of MSN can be efficiently adjusted. The high volume efficiency by using high TEOS concentration as Si sources and the low production cost by using urea as mineralizing agent for synthesizing MSN allow this novel technique to have great potential for industrial production. Furthermore, the advanced solid acid catalysts with superior catalytic activity and stability were prepared by supporting phosphotungstic acid (PTA) on MSN, ascribed to the high PTA dispersity and facilitated mass transfer by the short mesoporous channels in comparison with traditional mesoporous silica like MCM-41. This work presents an alternative method for overcoming low stability issue, a bottleneck problem for the industrial application of solid acid catalysts.