Highly active Ti-rich ordered mesoporous titanium silicate synthesizedunder strong acidic condition

Titanium-rich highly ordered mesoporous silica has been synthesized by using unconventional Ti source TiCl4 under strongly acidic pH condition in the presence of a cationic surfactant as supramolecular structure directing agent (SDA). The most Ti-rich sample for these mesoporous titanium silicates with two-dimensional hexagonal ordered structure was observed with Si/Ti=7.6Si/Ti=7.6 in the product. XRD, N2 sorption, 29Si MAS NMR, UV–vis diffuse reflectance, FT–IR spectroscopic tools, TEM and SEM image analyses were employed to characterize these materials. BET surface area and mesopore volume for all the samples were high. Strong UV–vis absorption band at 222 nm and FT–IR stretching vibration band of Si–O–Ti at 956cm-1 were observed in these Ti-rich samples indicating the presence of titanium in isolated tetrahedral environment and strongly bound inside the mesoporous framework. These Ti-rich ordered mesoporous titanium silicate samples showed excellent catalytic activity in the epoxidation of styrene (sample 2 having Si/Ti=7.6Si/Ti=7.6 showed 86% conversion with ca. 85% selectivity for styrene oxide) using dilute aqueous H2O2 as oxidant.