Efficient Ce–Ti/coal gangue catalysts via microwave synthesis for NH3-SCR: enhanced activity and mechanistic insights

Abstract

This study successfully synthesized a series of 15Ce–xTi/CG catalysts with different TiO₂ loading levels by integrating hydrothermal synthesis, impregnation techniques, and subsequent microwave sintering. To comprehensively evaluate the catalytic activity, microstructure, surface properties, and reaction mechanisms of the catalysts, a range of advanced techniques was employed, including NH₃-SCR testing, XRD, XPS, SEM, BET, NH₃-TPD, H₂-TPR, and in situ DRIFTs. The experimental findings revealed that the incorporation of TiO₂ significantly enhanced both the structural integrity and functional performance of the catalysts. Specifically, TiO₂ facilitated stronger interactions between Ce and Ti, increased the Ce³⁺/(Ce³⁺ + Ce⁴⁺) ratio, enriched the surface acidic sites, and boosted the concentration of chemically adsorbed oxygen species. Among all the catalysts, 15Ce–6Ti/CG demonstrated superior NO conversion efficiency (exceeding 92% at 300 °C) and maintained high activity across an extensive temperature range of 250–400 °C, while exhibiting remarkable resistance to SO₂ and H₂O poisoning. In situ DRIFTs experiments further corroborated the coexistence of both Eley–Rideal and Langmuir–Hinshelwood mechanisms, indicating that the catalytic process can proceed via multiple pathways. These results highlight the synergistic effects between Ce and Ti species, as well as the structural advantages of coal gangue as a sustainable support material, providing critical insights for the development of high-performance, environmentally friendly NH₃-SCR catalysts.