Evolution C3H6 poisoning mechanism study of coke deposition in Cu-SSZ-13 catalytic microchannel reactors

Abstract

To address the increasingly stringent global mobile source emission regulations, post-injection technology in diesel engines was widely applied to the thermal management of after-treatment systems. However, the additional hydrocarbon (HCs) species generated by post-injection could poison the catalysts in the SCR (Selective Catalytic Reduction) microchannel reactor, significantly reducing the reliability of the after-treatment system. This study investigated the mechanism of coke deposition induced by C₃H₆ poisoning on Cu-SSZ-13 catalysts. By combining thermogravimetric analysis, in situ infrared spectroscopy, and reaction kinetics simulation models, the key species involved in coke deposition formation and the regulation of reaction pathways on the Cu-SSZ-13 catalyst surface during the cracking of C₃H₆ were elucidated. The results showed that 20 h of C₃H₆ poisoning at 200 °C led to the formation of 3.02 wt% coke deposition on the Cu-SSZ-13 catalyst surface and shifted the NO_x reduction temperature range from 182–470 °C to 288–532 °C. In situ infrared spectroscopy and reaction kinetics analysis together identified the main pathway for coke deposition as C₃H₆ → C₂H₅ → C₂H₃ → CH₃CO → CH₃ → CH₂ → CH → C. A higher C₃H₆ /O₂ molar ratio effectively reduced the reaction rates of C₃ → C₂ and C₂ → C₁ at 218.6 °C and 342.5 °C, ultimately decreasing the maximum coke formation rate from 734.8 mol/(m³·s) to 1587.8 mol/(m³·s), thus inhibiting coke deposition formation.