Study on NH3-SCR performance, kinetics, and reaction mechanism of Ti–Ce–Cu–W composite oxide catalyst

Abstract

Selective catalytic reduction (SCR) technology is one of the main techniques for controlling nitrogen oxide (NO_x) emissions from diesel engines. The currently commercialized V₂O₅/TiO₂ catalyst exhibits high NO_x reduction efficiency at medium-to-high temperatures (300–400 °C). With increasingly stringent regulations, there is a growing need for SCR systems to operate efficiently at low temperatures. Examples include heavy-duty diesel vehicles under idling and cold-start conditions, SCR systems for marine low-speed engines installed behind turbochargers, and power plants placing SCR reactors after flue gas dedusting and desulfurization units. Therefore, the development of low-temperature SCR catalysts has become a critical research direction in the field of environmental catalysis. Solution combustion synthesis (SCS) can produce nanomaterials, which is beneficial for improving the physicochemical structure of catalysts and enhancing their low-temperature activity. This work focuses on catalysts synthesized via SCS to develop NH₃-SCR catalysts with high activity at low temperatures (<250 °C). Using Cu as the active element, a Ti_0.75Ce_0.15Cu_0.05W_0.05O_2−δ catalyst with excellent low-temperature performance and SO₂ resistance was prepared by SCS. Reaction kinetics experiments on the Ti_0.75Ce_0.15Cu_0.05W_0.05O_2−δ catalyst revealed its reaction rate constant and apparent activation energy. In situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) was used to study the reaction mechanism, confirming that the SCR reaction on this catalyst follows the Eley–Rideal mechanism, with NH₃ adsorbed on Lewis acid sites exhibiting strong reactivity.