A novel mesoporous silica-clay composite and its thermal and hydrothermal stabilities

A multi-mesopores composite has successfully been synthesized from natural montmorillonite and tetraethoxysilane. Two templating surfactants, cetyltrimethyl ammonium bromide and polyethylene glycol, have been employed in basic hydrothermal conditions in order to shape the pores in the composite. The N-2 adsorption/desorption isotherms, X-ray diffraction, infrared spectra and thermal analysis were used to obtain the detailed information of the porous structures. And the mechanism for the formation of this mesoporous silica-clay composite has been discussed. The results show that part of the walls of mesopores are originated from montmorillonite layers whose crystalline structure and required thickness benefit the stability of the sample. Moreover, as the infrared spectra revealed, the amorphous hydrolysate of tetraethoxysilane bonds with montmorillonite layers tightly. The resultant silica-clay has large specific surface area (472 m(2)/g) and its porous structure could resist the thermal treatment up to 900 A degrees C, which makes it a potentially host material for catalysts.