Selective catalytic reduction of NO_x with ethanol and other C_(1-4) oxygenates over Ag/Al_2O_3 catalysts: A review

摘要

Research results regarding selective catalytic reduction (SCR) of NO_x with ethanol and other C_(1-4) 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 NO_x and formation of nitroorganic compounds which transform to NCO_(ads) species and further to N_2. 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 NO_x with C_(1-4) oxygenates are outlined.