Enhanced catalytic ozonation of toluene using supported MnOx/USY via regulating the distribution of aluminum species in USY by dealumination

Abstract

Recently, the problem of VOCs pollution has become serious in many regions, especially developing countries. Herein, the distribution of aluminum species in USY was controlled by dealumination of Y zeolite under different conditions, and then the dealuminated samples were used to prepare five different supported catalysts MnOx/USY to achieve high-efficiency catalytic ozonation of toluene at low temperature. It was found that aluminum species were successfully leached from the zeolite framework to the extra-framework, which changed the properties of the manganese oxide nanoparticles loaded on the zeolite. Moreover, the oxygen vacancies and the acid sites in different catalysts showed great differences. As the extra-framework aluminum species increased, the amount of oxygen vacancies in the catalysts decreased, while the content of acid sites exhibited a “volcano-type” trend similar to toluene conversion. The best catalysts (Mn-Y-3) maintain > 90% toluene conversion at 30 °C but the worst catalysts (Mn-Y-5) deactivate rapidly. With the help of in situ DRIFTS, it is found that the activation ability of toluene on the acidic sites of the catalyst is the key to the toluene conversion when the amount of oxygen vacancies is sufficient to decompose ozone into active oxygen species, and the contribution of Lewis acid sites is greater than Brønsted acid sites. It provides some theoretical guidance in designing effective catalysts for ozone catalytic oxidation of VOCs.