Vapor phase oxidation of dimethyl sulfide with ozone over ion-exchanged zeolites

Abstract

This work studied the catalyst activity and stability of ion-exchanged zeolites during the oxidation of dimethyl sulfide (DMS) in the presence of ozone. Ozone was used as an oxidant to assess the oxidation capability of Ag/ZSM-5, Mn/ZSM-5 and Ag-Mn/ZSM-5 of DMS at both room temperature and 130 °C. Ion-exchange with silver ions (Ag +) strengthened the adsorption of DMS, resulting in an increased oxidation capacity for DMS. Furthermore, the introduction of manganese ions (Mn 2+) strengthened the oxidation capability of DMS, thus enhancing the selectivity of SO 2 obtained from the oxidation and reducing the degradation of activity because the pores of the catalyst were blocked by the oxidation products, such as dimethyl sulfoxide (DMSO) and dimethyl sulfone (DMSO 2). Ag-Mn/ZSM-5 demonstrated a 100% conversion of DMS; not only SO 2 but also H 2SO 3 and H 2SO 4 were detected at a high GHSV (90,000 h −1) and low reaction temperature (130 °C). The SO 2 adsorption curve and temperature-programmed desorption (TPD) showed that the single metal ion-exchanged zeolite had a weak adsorption capability for SO 2 at room temperature, whereas the bi-metal ion-exchanged zeolite had an excellent adsorption capability towards SO 2; it could convert SO 2 into H 2SO 3 and could convert oxidized SO 2 into H 2SO 4 in gas phase at room temperature.