Abstract
The selective catalytic reduction of NO(x) with CH(4) (CH(4)-SCR) holds the potential to simultaneously abate harmful NO(x) and CH(4) greenhouse gases. In this study, a series of bimetallic M-In/H-SSZ-39 catalysts (where M represents Cr, Co, Ce, and Fe) were prepared via an ion exchange method and subsequently evaluated for their CH(4)-SCR activity. The influences of the preparation parameters, including the metal ion concentration and calcination temperature, as well as the operating conditions, such as the CH(4)/NO ratio, O(2) concentration, water vapor content, and gas hourly space velocity (GHSV), on the catalytic activity of the optimal Cr-In/H-SSZ-39 catalyst were meticulously examined. The results revealed that the Cr-In/H-SSZ-39 catalyst exhibited peak CH(4)-SCR catalytic performance when the Cr(NO(3))(3) concentration was 0.0075 M, the In(NO(3))(3) concentration was 0.066 M, and the calcination temperature was 500 °C. Under optimal operating conditions, namely GHSV of 10,000 h(-1), 400 ppm NO, 800 ppm CH(4), 15 vol% O(2), and 6 vol% H(2)O, the NO(x) conversion rate reached 93.4%. To shed light on the excellent performance of Cr-In/H-SSZ-39 under humid conditions, a comparative analysis of the crystalline phase, chemical composition, pore structure, surface chemical state, surface acidity, and redox properties of Cr-In/H-SSZ-39 and In/H-SSZ-39 was conducted. The characterization results indicated that the incorporation of Cr into In/H-SSZ-39 enhanced its acidity and also facilitated the generation of InO(+) active species, which promoted the oxidation of NO and the activation of CH(4), respectively. A synergistic effect was observed between Cr and In species, which significantly improved the redox properties of the catalyst. Consequently, the activated CH(4) could further interact with InO(+) to produce carbon-containing intermediates such as HCOO(-), which ultimately reacted with nitrate-based intermediates to yield N(2), CO(2), and H(2)O.