Catalytic conversion of CO, NO and SO2 on supported sulfide catalysts: II. Catalytic reduction of NO and SO2 by CO

To investigate the possibility of simultaneous catalytic reduction of NO and SO2 by CO, reactions of NO, NOCO, and NOSO2CO were performed on γ-alumina-supported sulfides of transition metals including Co, Mo, CoMo and FeMo. decomposed into N2O and N2 accompanied with the formation of SO2; this serious oxidation of lattice sulfur resulted in the deactivation of the catalysts. The addition of CO to the NO stream suppressed SO2 formation and yielded COS instead. A stoichiometric conversion of NO and CO to N2 and CO2 was observed above 350°C on the CoMo and the FeMo catalysts. Although the CO addition lengthened catalyst life, it was not enough to maintain activity. After the NOCO reaction, an XPS analysis showed the growth of Mo6+ and SO42− peaks, especially for the sulfided FeMo/Al2O3; the FeMo catalyst underwent strong oxidation in the NOCO reaction. The NO and the NOCO reactions proceeded non-catalytically, consuming catalyst lattice sulfur to yield SO2 or COS. dition of SO2 in the NOCO system enabled in situ regeneration of the catalysts; the catalysts oxidized through abstraction of lattice sulfur experienced anew reduction and sulfurization through the SO2CO reaction at higher temperature. NO and SO2 were completely and catalytically converted at 400°C on the sulfided CoMo/Al2O3. By contrast, the sulfided FeMo/Al2O3 was easily oxidized by NO and hardly re-sulfided under the test conditions. ion states of the metals before and after the reactions were determined. Silica and titania-supported CoMo catalysts were also evaluated to study support effects.