Catalytic reduction of SO2 with CH4 to elemental sulfur: A comparative analysis of alumina, copper-alumina and nickel-alumina catalysts

The catalytic reduction of sulfur dioxide with methane to form elemental sulfur has been studied. Al2O3, Cu-Al2O3 and Ni-Al2O3 were examined as catalysts and their performances were compared in terms of SO2 conversion and selectivity. Performance of the catalyst extremely enhanced when nickel and copper were added as promoters. The effects of temperature, SO2/CH4 molar ratio, and reaction time on SO2 reduction were studied. The operating temperature range was 550–800 °C and it was observed that the reaction is strongly temperature dependent. At temperatures lower than 700 °C, Al2O3-Cu (10%) catalyst showed the best performance of all the catalysts. But, at 700° and higher, performances of Al2O3-Cu (10%) and Al2O3-Ni(10%) catalysts were similar. Complete conversion and selectivity (more than 99.5%) was achieved by Al2O3-Cu (10%) and Al2O3-Ni(10%) catalyst, at 750 °C. Effect of molar feed ratio of SO2/CH4= 1-3 was studied and stoichiometric feed ratio showed the best performance. Also, investigation of reaction time for Al2O3-Cu(10%) and Al2O3-Ni(10%) catalysts showed a good long-term stability for SO2 reduction with methane.