Abstract

Nanomaterials have been widely used in catalysis, separation technology and chemical sensing. In particular, materials with strong surface acidity and high thermal stability are essential in many catalytic applications. However, mesoporous materials reported such as Mobil crystalline (alumino-) silicate MCM-41 and alumino-phosphate based materials lacked such basic properties: this thus limited their applications in petroleum industry. In this work, novel silica nanoboxes H-dealX and deal-CaA with high thermal and chemical stability were developed by secondary synthesis from alumina-rich zeolites. The whole procedure consisted of controlled dealumination of alumina-rich zeolites, ion exchange (optional) and temperature-programmed calcination (TPC) treatments. The optimum conditions for controlled dealumination of alumina-rich zeolites [type 13X (NaX) and 5A (CaA)] using ammonium hexafluorosilicate (AHFS) were determined. It has been found that the richer the silica content in the parent zeolite, the smaller the average pore size produced and the narrower the pore size distribution obtained. The absence of micropores in the dealuminated solids is also a key point for having high thermal stability.