Development of a detailed surface mechanism for the selective catalytic reduction of NO_x with ethanol on silver alumina catalyst

Ethanol selective catalytic reduction (SCR) Of NO_x on silver alumina catalyst is a promising technology in reducing NO_x from Diesel engines. In particular, experimental results show that using ethanol reductant on low loading silver alumina catalyst can result in greater than 90% of NO_x reduction over a wide temperature range. Even though this technology has been demonstrated experimentally, there is no known detailed surface model to describe the ethanol SCR process. In this work, a detailed surface mechanism with 35 irreversible reactions has been developed by critically reviewing literature data on ethanol SCR and by performing Surface Perfectly Stirred Reactor (SPSR) simulations. Using the new surface SCR mechanism along with validated ethanol gas phase chemistry from LLNL, the cause of the inactivity of ethanol SCR at temperatures above 500 °C is found to be the desorption of NO and ethanol rather than gas phase ethanol oxidation. Predictions with the new ethanol SCR mechanism agree well with the experimental NO_x conversion. However, further improvement on the model is needed to improve predictions involving the hydrocarbon species.