Selective catalytic reduction of NO_x with ethanol and other C_1-4 oxygenates over Ag/Al₂O₃ catalysts: A review

Abstract

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 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 NO_x with C_1-4 oxygenates are outlined.

Key words： SCR; nitrogen oxides; silver-alumina catalyst; silver species; ethanol; oxygenates

Acknowledgments

The author expresses his gratitude to Prof. Svitlana M. Orlyk and Dr. Nataliia O. Popovych for useful discussions.

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