Ce–Si Mixed Oxide: A High Sulfur Resistant Catalyst in the NH3–SCR Reaction through the Mechanism-Enhanced Process

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Investigating catalytic reaction mechanisms could help guide the design of catalysts. Here, aimed at improving both the catalytic performance and SO 2 resistance ability of catalysts in the selective reduction of NO by NH 3 (NH 3 –SCR), an innovative CeO 2 –SiO 2 mixed oxide catalyst (CeSi2) was developed based on our understanding of both the sulfur poisoning and reaction mechanisms, which exhibited excellent SO 2 /H 2 O resistance ability even in the harsh working conditions (containing 500 ppm of SO 2 and 5% H 2 O). The strong interaction between Ce and Si (Ce–O–Si) and the abundant surface hydroxyl groups on CeSi2 not only provided fruitful surface acid sites but also significantly inhibited SO 2 adsorption. The NH 3 –SCR performance of CeSi2 was promoted by an enhanced Eley–Rideal (E–R) mechanism in which more active acid sites were preserved under the reaction conditions and gaseous NO could directly react with adsorbed NH 3 . This mechanism-enhanced process was even further promoted on sulfated CeSi2. This work provides a reaction mechanism-enhanced strategy to develop an environmentally friendly NH 3 –SCR catalyst with superior SO 2 resistance.