Effect of Cu content and zeolite framework of n-C4H10-SCR catalysts on de-NOx performances

Abstract

The catalytic activity of Cu/zeolites with different types of zeolite frameworks (SSZ-13, ZSM-5, and BETA) was investigated in the selective catalytic reduction of NOx with n-C4H10. The Cu content and zeolite framework significantly affected the catalytic performance in the C4H10-SCR process, where the low-Cu-impregnated medium-pore ZSM-5 structure (2Cu/ZSM-5) exhibited the optimal de-NOx performance, followed by the high- and medium Cu-impregnated large- and small-pore BETA and SSZ-13 zeolites (10Cu/BETA and 5Cu/SSZ-13), respectively. The effects of coexistent gases (CO2 and O2) and hydrothermal aging were also evaluated for 2Cu/ZSM-5. CO2 in the feed gas induced an unfavorable effect on NOx reduction because it competed with NO and C4H10 adsorption on the catalyst surface. O2 in the feed gas had a positive effect on NOx conversion, CO oxidation, and partial oxidation of C4H10, and N2 selectivity was highly affected by the O2 concentration, producing a large amount of NH3 in the absence of O2. The deactivation of the catalytic activity after hydrothermal aging was attributed to collapse of the pore structures and a drop in the zeolite crystallinity. However, there was no catalytic deactivation due to the coke formation by hydrocarbons within 24 h in the steady-state stability test.