Selective Catalytic Reduction of NO<i><sub>x</sub></i> by Methanol on Metal-Free Zeolite with Brønsted and Lewis Acid Pair
Fei Han, Han Sun, Zhenchao Zhao, Yaxin Xu, Hong Dong, Weiwei Liu, Lu Sun, Zhili Wang, Guangjin Hou, Masaaki Kitano, Wei Li, Meiqing Shen, Haijun Chen
Abstract
The selective catalytic reduction deNOx 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 deNOx method with pure H-FER zeolite as the catalyst using methanol as a reductant instead of NH3 (CH3OH-SCR). This metal-free zeolite with Brønsted and Lewis acid pairs shows almost 4 times higher activity than the most investigated precious metal catalyst (Ag/Al2O3). Furthermore, it shows a comparable deNOx 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.