Selective oxidation of benzyl alcohol to benzaldehyde with hydrogen peroxide over alkali-treated ZSM-5 zeolite catalysts

A stable, economic and high active catalyst for selective oxidation of benzyl alcohol (BzOH) was developed by treating ZSM-5 zeolite with sodium hydroxide solution. The changes resulted by alkali-treatment in crystallinity, composition, structure parameters and acidities of alkali-treated ZSM-5 zeolites were examined by XRD, ICP, N2 adsorption-desorption, scanning electron micrographs (SEM), temperature program desorption (TPD) and Fourier transform infrared spectroscopic (FT-IR). The results showed that the specific MFI structure was preserved and the intrinsic micropores were kept without obvious change, the amount of Lewis acid sites and the external surface area were evidently increased after alkali-treatment. Without any organic solvent, the catalytic performance of alkali-treated ZSM-5 zeolite was investigated in selective oxidation of BzOH with hydrogen peroxide (H2O2), and the effects of reaction temperature, reaction time, dosage of catalyst, dosage of H2O2 and SiO2/Al2O3 ratio of as-received zeolites on catalytic selective-oxidation of BzOH were investigated. The results showed that the conversion of BzOH and the selectivity to benzaldehyde (BzH) were about 53% and about 86% respectively under reflux for 4 h in water. At the same time, the catalyst was very stable and could be reused for more than six times.

An effective ZSM-5 zeolite catalyst was prepared via alkali-treatment, which exhibited high activity for selective oxidation of benzyl alcohol to benzaldehyde (BzH). The catalytic performance was improved by increasing the amount of active sites (i.e., Lewis acid sites) with alkali-treatment, which can split the bridging Si–OH–Al groups to form framework Al-Lewis sites.Figure optionsDownload high-quality image (230 K)Download as PowerPoint slide