Selective catalytic reduction of NOx with ethanol and other C1–4 oxygenates over Ag/Al2O3 catalysts: A review

Abstract

Research results regarding selective catalytic reduction (SCR) of NOx with ethanol and other C1-4 oxygenates as reductants over silver-alumina catalysts are summarized. The aspects of the process mechanism, nature of active sites, role of alumina and silver (especially in the formation of bifunctional active sites), effects of reductants and reaction conditions are discussed. It has been determined that key stages of the process include formation of reactive enolic species, their interaction with NOx and formation of nitroorganic compounds which transform to NCOads species and further to N2. The results obtained over various silver-alumina catalysts demonstrate the perspectives of their application for reducing the level of nitrogen oxides in engine emissions, including in the presence of water vapor and sulfur oxides. Ways to improve the catalysts for the SCR of NOx with C1-4 oxygenates are outlined.