Theoretical analyses of NH3-SCR reaction-mass transfer over Cu-ZSM-5

NH3-selective catalytic reduction (NH3-SCR) is a very effective technical means to control NOx emissions from diesel engines, and Zeolite Selony Mobil No. 5 (SiO2/Al2O3 ratio 53:1) ion exchanged with Cu (Cu-ZSM-5) provides support for the high performance of NH3-SCR within a wide temperature window under diesel engine operating conditions. The mechanism of the NH3-SCR reaction based on Cu-ZSM-5 is established. Resistance analysis, effective factor analysis, and characteristic time analysis are used to analyze the influence of external mass transfer limitation and washcoat diffusion limitation on NH3-SCR reaction and the transition between the washcoat diffusion control regime, the external mass transfer control regime, and the kinetic control regime of the NH3-SCR over Cu-ZSM-5. It provides the basis for the optimization of the catalyst structure and the support for the improvement of NH3-SCR performance.