This paper reports the catalytic behavior toward benzene oxidation in the presence of ozone of manganese oxides supported on a high Si/Al ratio zeolite (SiO2/Al2O3 = 180). The catalysts were characterized by N2 adsorption, X-ray absorption fine structure (XAFS), and temperature-programmed reduction (TPR). By a conventional impregnation technique, the manganese oxides were highly dispersed in the zeolite Y in the 3+ oxidation state, and they were the active sites for benzene oxidation by ozone. Steady-state activities were obtained at 313-373 K under both dry and humid conditions. Under both of those conditions, a strong correlation was observed among the amounts of ozone consumed, benzene oxidized, and COx formed. Water vapor in the reaction gas enhanced benzene oxidation by promoting by-product compound oxidation by the catalyst, and water vapor thus slightly improved CO2 selectivity. Fourier-transformed infrared (FTIR) and temperature-programmed oxidation (TPO) studies demonstrated that benzene was oxidized on the catalysts to oxygen-containing by-products such as weakly bound formic acid and strongly bound carboxylates. Although formic acid was steadily formed during the reaction, it was readily oxidized to CO 2 and CO by the ozone feed. The ratio of ozone decomposition to benzene oxidation was approximately 9-10 and was almost independent of reaction temperature and humidity, indicating that ozone was efficiently consumed through benzene oxidation under the reaction conditions.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry