Selective Catalytic Reduction of NOx by Methanol on Metal-Free Zeolite with Bronsted and Lewis Acid Pair

The selective catalytic reduction deNO(x) technology by ammonia (NH3-SCR) on vanadium-based catalysts is now being used worldwide for industrial exhaust treatment, while the disposal of spent catalysts faces a high level of environmental risk posed by poisonous vanadium. We present here an environmentally friendly deNO(x) method with pure H-FER zeolite as the catalyst using methanol as a reductant instead of NH3 (CH3OH-SCR). This metal-free zeolite with Bronsted and Lewis acid pairs shows almost 4 times higher activity than the most investigated precious metal catalyst (Ag/Al2O3). Furthermore, it shows a comparable deNO(x) efficiency with state-of-the-art of NH3-SCR on vanadium-based catalysts, as well as good stability with potential for industrial application. Operando Fourier transform infrared (FT-IR), in situ NMR, and theoretical calculations demonstrated that solid acid species are highly active for the CH3OH-SCR reaction. A reaction mechanism based on a synergistic catalytic effect between Si-O(H)-Al sites and neighboring extra-framework aluminum (EFAL) species has been proposed.