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

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 (Mn2+) strengthened the oxidation capability of DMS, thus enhancing the selectivity of SO2 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 (DMSO2). Ag-Mn/ZSM-5 demonstrated a 100% conversion of DMS; not only SO2 but also H2SO3 and H2SO4 were detected at a high GHSV (90,000 h−1) and low reaction temperature (130 °C). The SO2 adsorption curve and temperature-programmed desorption (TPD) showed that the single metal ion-exchanged zeolite had a weak adsorption capability for SO2 at room temperature, whereas the bi-metal ion-exchanged zeolite had an excellent adsorption capability towards SO2; it could convert SO2 into H2SO3 and could convert oxidized SO2 into H2SO4 in gas phase at room temperature.

Figure optionsDownload high-quality image (79 K)Download as PowerPoint slideResearch highlights▶ Ag-Mn/ZSM-5 oxidizes DMS in the presence of ozone. ▶ The Mn2+ in Ag-Mn/ZSM-5 enhances the oxidizing activity of the catalyst for DMS. ▶ The two metals contained in Ag-Mn/ZSM-5 are cooperative in the oxidization of SO2. ▶ Ag-Mn/ZSM-5 converts SO2 into H2SO3 and oxidizes SO2 to H2SO4 in gas phase.