Dependable method for quantifying the hydrothermal aging of Cu-CHA SCR catalysts

Jinyong  Luo, Cummins Inc.

A method for translating the diesel engine operating time, exhaust gas temperature and total number of miles in to a representative time at fixed hydrothermal aging temperature condition for aftertreatment catalysts hydrothermal deactivation of Cu-SSZ-13 based SCR catalysts, in a form of equivalent aging conditions (time at a fixed temperature), is critical for determining the state of a catalyst with unknown aging history. Typical diagnostic techniques are based on NOx conversion, total NH3 storage, or other gross performance measures, and their accuracy can be affected by the possible local variations in catalyst loading and by other factors such as sulfur loading, etc.

In this contribution, we identified a feature, based on distinguishable NH3 storage and release properties, which uniquely identifies the state of catalyst material aging. Using this feature, a technique including transfer function has been developed, which can translate the measured material state into equivalent aging time at different temperatures. This feature is common to the entire class of Si/Al-based Cu-CHA catalysts, independent on the washcoat amount and sulfur loading. Therefore, it shows great advantages over other conventional techniques in lab diagnostics.

In this presentation, we will first describe NH3-TPD techniques for feature characterization, including the physical meaning of the feature revealed by DRIFTS; next, we will translate the feature into mathematics and develop a transfer function, followed by validation and sensitivity analysis; last, case studies will be shown to demonstrate how to apply the transfer function to quantity the catalyst hydrothermal aging experienced by real-world SCR catalysts.