Revealing the synergistic effect of InO and Brønsted acid on the superior activity of hybrid In/H-SSZ-39 in the selective catalytic reduction of NO with CH.

Selective catalytic reduction of NO with CH (CH-SCR) is a promising strategy for NO abatement that utilizes CH escaping from the incomplete combustion of liquefied natural gas (LNG) to reduce NO. However, developing CH-SCR catalysts with high efficiency at temperature < 450°C remains a significant challenge. Herein, this work reported an In/H-SSZ-39-Hy zeolite catalyst (Hy represents hybrid AEI/MOR topology) with superior activity by utilizing the synergistic effect of InO and Brønsted acid (BA). The maximum NO conversion (74 %) achieved over the In/H-SSZ-39-Hy at 430°C with a gas hourly space velocity (GHSV) of 48,000 h, which was significantly higher than that over the commercial In/H-SSZ-39 and In/H-SSZ-13 catalysts. A series of characterizations revealed that abundant BA sites and surface adsorbed oxygen contributed to the formation of reactive InO and nitrate species, which played a critical role in facilitating CH activation and redox cycling. In situ DRIFTS confirmed that CH was activated at the InO site and reacted with nitrate at the BA sites to form the important intermediate CHNO, which further converted to N, CO and HO. This study elucidates the synergistic roles of InO and BA in CH-SCR, and provides a deeper understanding of catalytic mechanism.