Challenges and Perspectives of Environmental Catalysis for NO x Reduction.

Abstract

Environmental catalysis has attracted great interest in air and water purification. Selective catalytic reduction with ammonia (NH₃-SCR) as a representative technology of environmental catalysis is of significance to the elimination of nitrogen oxides (NO _x ) emitting from stationary and mobile sources. However, the evolving energy landscape in the nonelectric sector and the changing nature of fuel in motor vehicles present new challenges for NO _x catalytic purification over the traditional NH₃-SCR catalysts. These challenges primarily revolve around the application limitations of conventional industrial NH₃-SCR catalysts, such as V₂O₅-WO₃(MoO₃)/TiO₂ and chabazite (CHA) structured zeolites, in meeting both the severe requirements of high activity at ultralow temperatures and robust resistance to the wide array of poisons (SO₂, HCl, phosphorus, alkali metals, and heavy metals, etc.) existing in more complex operating conditions of new application scenarios. Additionally, volatile organic compounds (VOCs) coexisting with NO _x in exhaust gas has emerged as a critical factor further impeding the highly efficient reduction of NO _x . Therefore, confronting the challenges inherent in current NH₃-SCR technology and drawing from the established NH₃-SCR reaction mechanisms, we discern that the strategic manipulation of the properties of surface acidity and redox over NH₃-SCR catalysts constitutes an important pathway for increasing the catalytic efficiency at low temperatures. Concurrently, the establishment of protective sites and confined structures combined with the strategies for triggering antagonistic effects emerge as imperative items for strengthening the antipoisoning potentials of NH₃-SCR catalysts. Finally, we contemplate the essential status of selective synergistic catalytic elimination technology for abating NO _x and VOCs. By virtue of these discussions, we aim to offer a series of innovative guiding perspectives for the further advancement of environmental catalysis technology for the highly efficient NO _x catalytic purification from nonelectric industries and motor vehicles.