Review of nitrous oxide direct catalytic decomposition and selective catalytic reduction catalysts

Abstract

With the increasing global warming, the control of nitrous oxide (N2O) emissions in various fields has become urgent. Direct catalytic decomposition is currently the most widely used technology to reduce N2O emissions from the nitric acid industry. Selective catalytic reduction (SCR), which can utilize unburned NH3 from engine exhaust as a reductant, is the most promising technology for reducing N2O emissions from ammonia-fueled engines. Increasing demands on the operating temperature window, O2/H2O/NO resistance, and hydrothermal stability of catalysts have stimulated the development of novel catalytic N2O removal catalysts. This review first summarizes the N2O generation mechanism, comprehensive N2O catalytic removal reaction mechanism and O2/H2O/NO inhibition mechanism, and then provides a comprehensive overview of the related catalysts, including Ru- and Rh-based precious metal catalysts, Cu- and Co-based non-precious metal catalysts, and Fe- and Cu-based molecular sieve catalysts, focusing on direct catalytic decomposition of N2O and N2O-SCR. Effective strategies for various catalysts to improve the acidity, redox cycling, and toxicity resistance of the catalysts through modification, creation of novel nanostructures, and exposure of specific crystalline surfaces are summarized, and the challenges and opportunities they face are presented. In addition, this paper summarizes some other methods for catalytic removal of N2O and develops a detailed description for the synergistic removal of N2O and NOx. Finally, this review provides some suggestions for future research directions. It is hoped that this review will provide a theoretical basis for the optimal preparation of catalysts to bridge the gap between catalyst performance and practical needs, and help to realize the commercial application of efficient catalysts in the near future.