Overview of mechanisms of promotion and inhibition by H2O for selective catalytic reduction denitrification

Abstract

Selective catalytic reduction (SCR) is currently the main method for removing nitrogen oxides (NOx) from mobile sources. SCR catalysts are susceptible to the toxic effects of H2O in the actual flue gas. There is still a need to develop SCR catalysts with better activity and water resistance. A large number of existing studies have shown that the effect of H2O on the performance of SCR catalysts mainly depends on the type of reductant used in the SCR reaction, the reaction conditions and the catalyst type. This review summarized the mechanism of the promoting or inhibiting effect of H2O in the SCR reaction process in detail. The ways in which reaction conditions such as water content and reaction temperature affect different SCR reactions as well as SCR catalysts were discussed. Finally, current improvement strategies to enhance the catalytic activity and water resistance of SCR catalysts were collated. This work helps researchers to gain a deeper understanding of the mechanism of water's role in SCR reactions. It provides theoretical and methodological support for the preparation of SCR catalysts with higher water resistance.