Autocatalytic synergism observed during lean-NOx reduction with a bifunctional reductant over Ag/Al2O3 catalyst

Abstract

Autocatalytic kinetic synergism between the conventional selective catalytic reduction of NO, by hydrocarbon (HC-SCR) and ammonia (NH3-SCR) has been observed during lean-NO, reduction with a bifunctional reductant (an amino alcohol) over a Ag/Al2O3 catalyst, resulting in significant enhancement of the deNO(x) activity. Monoethanolamine (MEA) employed as the bifunctional reductant produces effective reductants such as H-2, NH3, and isocyanate species, thereby transforming the single-functional Ag/Al2O3 catalyst for HC-SCR into a dual-functional catalyst for both HC-SCR and NH3-SCR. The production of those highly reactive intermediate reductants by MEA initiates the autocatalytic deNO(x) process, while the kinetic synergy in the deNO(x) catalysis can be attributed to the formation of (OH center dot center dot center dot N) hydrogen bonds in and among MEA molecules. Based on steady-state kinetic data, reaction pathways have been proposed for MEA-SCR over Ag/Al2O3, and a method for further improvement in deNO(x) activity has been demonstrated in a dual-bed reactor system. (C) 2012 Elsevier Inc. All rights reserved.