Tungsten promoted HZSM-5 in the SCR of NO by acetylene

Abstract

The performance of 6% W/HZSM-5 catalyst in the SCR of NO by C 2H 2, C 3H 6 and CH 4 was compared. Contrary to the low selectivity of C 3H 6 in NO reduction and the high temperature required by CH 4 for activation, high and steady NO conversion to N 2 (89%) was achieved at 350 °C when C 2H 2 was used as reductant with a feed of 1600 ppm of NO, 800 ppm of C 2H 2, 10% of O 2 in He. It was found that tungsten dispersed on HZSM-5 has a synergistic effect with protons in the C 2H 2-SCR of NO. Tungsten incorporation into HZSM-5 significantly accelerated the NO oxidation to NO 2 and enlarged strong adsorption of NO x on the catalyst surface, and thus considerably enhanced the aimed reaction. For the C 2H 2-SCR of NO carried out over the 6% W/HZSM-5 catalyst, carbonous species containing a carbonyl group were active species responsible for the aimed reaction, which involves the reduction of bidentate and bridging nitrate species formed on the catalyst under the reaction conditions.