Simultaneous catalytic reductions of NO and SO2 by H2 over nickel-tungsten catalysts

The simultaneous reductions of SO2 and NO by H-2 on sulfided nickel-tungsten catalysts are investigated for the first time. Virtually 100% conversions of NO and SO2 with 100% and 90% selectivity toward nitrogen and sulfur, respectively, over sulfided NiW/Al2O3 have been revealed at 550 degrees C. As a result, this highly active and selective catalyst has been characterized extensively by X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. It has been found that the oxidative leakage of lattice sulfur by NO results in a rapid deactivation of this sulfided catalyst in both NO decomposition and the NO reduction reaction. The sulfur produced from the hydrogen reduction of SO2 can, however, replenish the lost sulfur while maintaining the essential sulfide structure necessary for steady catalytic activity. Thus, a tentative reaction mechanism for the simultaneous reductions of SO2 and NO with H-2 over this new sulfided NiW/Al2O3 catalyst is proposed.