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

Abstract

Investigating catalytic reaction mechanisms could help guide the design of catalysts. Here, aimed at improving both the catalytic performance and SO2 resistance ability of catalysts in the selective reduction of NO by NH3 (NH3-SCR), an innovative CeO2-SiO2 mixed oxide catalyst (CeSi2) was developed based on our understanding of both the sulfur poisoning and reaction mechanisms, which exhibited excellent SO2/H2O resistance ability even in the harsh working conditions (containing 500 ppm of SO2 and 5% H2O). 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 SO2 adsorption. The NH3-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 NH3. This mechanism-enhanced process was even further promoted on sulfated CeSi2. This work provides a reaction mechanism-enhanced strategy to develop an environmentally friendly NH3-SCR catalyst with superior SO2 resistance.