Suppression of Ammonia Slip by Smart Reductants in Selective Catalytic Reduction of Nitrogen Oxides

Ammonia (NH3)-based selective catalytic reduction (SCR) is a mainstream flue gas denitration technology for stationary and mobile sources, but NH3 slip remains a critical challenge from mismatches between stoichiometric reaction requirements and fluctuating nitrogen oxides (NOx) concentrations. Herein, we show organic amines (e.g., n-butylamine, n-B) act as smart reductants for SCR systems. Unlike NH3, n-B reacts stoichiometrically with NOx and undergoes NO-accelerated self-elimination when overdosed over TiO2-supported VOx catalysts. Mechanistic studies reveal Ti─OH sites on the catalyst facilitate n-B adsorption and activation, with the *NH3 intermediate driving NOx reduction. *NH2 from excess n-B oxidizes to nitrites and NO2 under NO+O2, which further react with *NH3 via an internal SCR pathway, avoiding free NH3 formation and slip. We propose a hybrid reductants system (NH3 + n-B) enabling efficient NH3 slip suppression over a reductant/NOx molar ratio of 1.2, providing a promising strategy without modifying existing SCR hardware or structures.