Synthesis and applications of M-MCM-48 (M = Ti, Cc, and Cr) from silatrane precursor

Abstract

Hydrothermal synthesis of cubic MCM-48 was carried out using silatrane as a silica precursor and CTAB as a structure directing agent. The effects of synthesis parameters, viz. crystallization temperature, crystallization time, surfactant concentration, quantity of NaOH, and silica source, on the product structure were investigated. To examine the properties of the synthesized materials, various techniques were introduced, viz. X-ray diffraction (XRD), nitrogen adsorption-desorption measurement, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and surface area analysis. A high specific surface area and narrow pore size distribution were obtained. The materials showed a truncated octahedral shape and cubic la3d symmetry of pore structure. To improve the catalytic property of mesoporous silica the incorporation of metals (M =Cr, Ce and Ti) was studied, using the optimal synthesis of MCM-48 conditions. Both framework and extraframework of the metals were investigated by diffuse reflectance UV-visible spectroscopy (DR-UV). The catalytic performance of all materials was performed on the oxidation of styrene using hydrogen peroxide as an oxidant. The optimal conditions were studied as a function of reaction time, reaction temperature, ratio of oxidant/styrene, amount of catalyst, and metal content. The % conversion of styrene and the % selectivity of products depended on the nature of the metal loading. Additionally, the kinetic study of Cr-MCM-48 catalysts toward the styrene oxidation was also investigated.