Catalytic reduction of SO2 with CO over supported iron catalysts

Iron oxides supported on several types of carriers (gamma-Al2O3, HZSM-5, SiO2, and MgO) were investigated for the catalytic reduction of SO2 by CO. The catalytic tests show that the activity of the catalysts followed the order Fe2O3/gamma-Al2O3 > Fe2O3 > HZSM-5 >> Fe2O3/SiO2 > Fe2O3/MgO. The X-ray diffraction analysis characterization of the presulfided catalysts revealed that FeS2 formation was greatly dependent on the acidic nature of the supports, with an evident FeS2 phase detected on both gamma-Al2O3 and HZSM-5, in contrast with Fe7S8 formed on SiO2 and MgO. Presulfidation with a reacting gas mixture above 500 degrees C was necessary for obtaining a high activity because of the formation of active-phase FeS2 during this process. The catalytic activity correlated well with the sulfidation degree of Fe2O3, which is mainly dependent on the acidic nature of the support and the choice of the presulfidation conditions. When the Fe content was at 20 wt %, under the optimal feed compositions (CO/SO2 = 2: 1), the Fe2O3/gamma-Al2O3 catalyst exhibited the best catalytic performance, with 99.31% SO2 conversion and a 99.17% sulfur yield obtained at 380 degrees C.