Bimetallic Cr-In/H-SSZ-13 for selective catalytic reduction of nitric oxide by methane

Bimetallic Cr-In/H-SSZ-13 zeolites were prepared by wet impregnation and investigated for selective catalytic reduction of nitric oxide by methane (CH4-SCR). Reduction-oxidation treatments led to close contact and interaction between Cr and In species in these zeolites, as revealed by transmission electron microscopy and X-ray photoelectron spectroscopy. Compared to monometallic Cr/H-SSZ-13 and In/H-SSZ-13, the bimetallic catalyst system exhibited dramatically enhanced CH4-SCR performance, i.e., NO conversion greater than 90% and N2selectivity greater than 99% at 550 °C in the presence of 6% H2O under a high gas hourly space velocity of 75 000/h. The bimetallic Cr-In/H-SSZ-13 showed very good stability in CH4-SCR with no significant activity loss for over 160 h. Catalytic data revealed that CH4and NO were activated on the In and Cr sites of Cr-In/H-SSZ-13, respectively, both in the presence of O2during CH4-SCR.