Changes of the C3H6-Poisoning Effect over a Cu-SSZ-13 NH3–SCR Catalyst upon Hydrothermal Treatment at Different Temperatures

The deactivation of the Cu-SSZ-13 catalyst used in a selective catalytic reduction with ammonia, for the elimination of NOx from diesel engines, by the presence of hydrocarbons (HCs) affected the application of this catalyst to some extent. In this work, the effect of HC poisoning on Cu-SSZ-13 catalysts upon hydrothermal aging treatment (HTA) was investigated. Three samples aged at different temperatures (700, 750, and 800 °C, respectively) were selected. The results showed that the activities were seriously decreased for fresh and HTA samples, especially in the range of 150–350 °C, while negligible effects were observed when the temperature was above 400 °C. The carbonous deposit, including aliphatic and aromatic compounds, formed in C3H6-poisoned Cu-SSZ-13 and HTA samples, which blocks the pore channels and covers the Cu2+ ion sites, resulting in the deactivation. The acidity and pore size affect the content and types of carbonous deposit. Much more carbonous deposit forms in Cu-SSZ-13 than in hydrothermal aged samples due to the larger content of Brønsted acid sites. The ratio of aromatic compounds increases with the increase of HTA temperatures, probably attributed to the greater generation of mesopores. The changes of carbonous deposit result in the different NOx conversion decline extent in the catalysts aged at different temperatures.