Synergic effects of a protic ionic liquid on P123 mixed micelles for inducing hierarchical porous materials

This research reports a bimodal templating method to synthesize hierarchical porous silicas (HPS) by using P123 and a protic ionic liquid in aqueous systems. The influence of the pH, the hydrothermal temperature, and the synthesis route on the synthesis of HPS was systematically investigated. The structures of all the composites were characterized by using N2 gas sorption, scanning electron microscope (SEM) and transmission electron microscopy (TEM). The results showed that HPS with different structures were obtained under the different conditions. Among the obtained silica materials, HPS with two kinds of mesoporous channels could be clearly identified from the TEM images when the pH was 2. While, at pH = 3, it could be found that a particular structure like the mesocellular foams was obtained. Silica spheres were synthesized when the pH was 9, indicating that the different interaction between P123 and PIL under different pH values can promote the condensation of hydrolyzed silica species from TEOS into silica materials in different ways, resulting in different morphologies and internal structures. Moreover, the formation mechanism of the hierarchical porous silica which is based on the interaction between PIL and P123 is tentatively elucidated. 12-Tungstophosphoric acid (HPW) catalysts incorporated into these HPS were prepared by impregnation, and their catalytic activities for alkylation of o-xylene with styrene were investigated. Alkylation results exhibited that both of the catalysts showed a high catalytic performance in terms of propane conversion and selectivity to propene. This approach provides a new pathway for the facile synthesis of HPS materials which may be a type of promising candidate for various applications.