Autocatalytic synergism observed during lean-NO x reduction with a bifunctional reductant over Ag/Al2O3 catalyst

Graphical abstract Autocatalytic synergy between selective catalytic reduction by hydrocarbons and ammonia is observed with a bifunctional reductant, monoethanolamine, resulting in enhanced deNO x activity over a Ag/Al2 O3 catalyst. Display Omitted Highlights An autocatalytic synergism was observed during NO x reduction with MEA over Ag/Al2 O3 . MEA transforms the single-functional Ag/Al2 O3 into a dual-functional catalyst. Highly reactive reductants such as H2 , NH3 , and isocyanate species are formed by MEA. The kinetic synergy is attributable primarily to the formation of H-bonding in MEA. Autocatalytic kinetic synergism between the conventional selective catalytic reduction of NO x by hydrocarbon (HC-SCR) and ammonia (NH3 -SCR) has been observed during lean-NO x reduction with a bifunctional reductant (an amino alcohol) over a Ag/Al2 O3 catalyst, resulting in significant enhancement of the deNO x activity. Monoethanolamine (MEA) employed as the bifunctional reductant produces effective reductants such as H2 , NH3 , and isocyanate species, thereby transforming the single-functional Ag/Al2 O3 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 (OHN) hydrogen bonds in and among MEA molecules. Based on steady-state kinetic data, reaction pathways have been proposed for MEA-SCR over Ag/Al2 O3 , and a method for further improvement in deNO x activity has been demonstrated in a dual-bed reactor system. [PUBLICATION ABSTRACT]