Synthesis and Characterization of Chromium Incorporated Mesoporous Silica Material (Cr-SBA-16) - Applicatons in selective Oxidation

Abstract

The aim of this work is the synthesis and characterization of chromium containing ordered mesoporous silica materials with three-dimensional interconnected pore system and their evaluation in the selective oxidation of benzyl alcohol. The prepared Cr-SBA-16 (x) materials were synthesised successfully using different Si /Cr ratio. Herein, we used one-pot hydrothermal method at low acidic medium and 45˚ C. The main goal in the catalyst synthesis part is to obtain highly ordered mesoporous materials with excellent chromium dispersion. In this context, chromium incorporated SBA-16 with three different Si/Cr ratio of 7, 14 and 28 were successfully synthesized. These materials have been characterized using low-angle X-ray Powder Diffraction (XRD).X-ray photoelectron spectroscopy (XPS) and UV-Vis spectroscopy (DRS) were also used to determine the coordination and environment of the chromium species present onto surface and bulk of the prepared materials. The textural properties of the prepared materials were also studied using N2 adsorption-desorption at 77 K technique. All the catalyst exhibits the type-IV isotherms with a H2 hysteresis loop which is characteristic of the SBA-16 materials with 3D cage-like pore structures. The selective oxidation of benzyl alcohol onto Cr-SBA-16 catalyst obeys to first-order kinetic model. We demonstrated that the adsorption of benzyl alcohol and hydrogen peroxide onto Cr-SBA-16 is non-competitive and mainly occurs on different active sites. Finally, the activity of the reaction depends on chromium environment, herein, high activity is obtained for tetrahedral chromium species.