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.