Synthesis and application of SBA-1 mesoporous silica by atrane route via sol-gel process

Abstract

Silatrane was used as a precursor for SBA-1 synthesis at room temperature using alkyltrimethylamm onium bromides, CnTMAB (n = 14-18), as templates in dilute solutions. The influences of acidity, alkyl chain length of the surfactant and synthesis tem perature w ere studied. At high surfactant concentration and elevated reaction temperature, three-dimensionally ordered mesopores were invariably produced. The surface area of the product was as high as 1000-1500 m 2/g with an adsorption volume of 0.6 - 1.0 cm 3/g. When using a poly (amido amine) dendrimer porogen as a tem plate under mild condition, two kinds of crystal arrays were found to be produced in the silica particles. These results indicate that one molecule of silatrane constructed polysiloxane wall in the first array and oligomeric silatranes formed w all in the second array. It was referred that the intrinsic (hydrogen bonding) character of hydroxyl groups in the hydrolyzed silatrane resulted in hydrogen bonded oligomers and reinforced the hydrogen bonding interaction with dendrimer porogen as well as electrostatic interaction, giving rise to two types of tem plate arrays. The mesoporous SBA-1 was also used as a catalyst support with 6 wt% Fe and 10wt% Ti without perturbing the ordered mesoporous. The catalytic activity and selectivity of styrene epoxidation using hydrogen peroxide w ere studied, and showed that the selectivities of benzaldehye and styrene oxide reached 74 and 11%, respectively, at styrene conversion of 67% over 4% Fe in SBA-1 while those of styrene oxide and benzaldehyde reached 48 and 50%, respectively, at styrene conversion of 69% over 2% Ti in SBA-1.