Alkali-Poisoning-Resistant Fe2O3/MoO3/TiO2 Catalyst for the Selective Reduction of NO by NH3: The Role of the MoO3 Safety Buffer in Protecting Surface Active Sites

The exhaust gas contains harmful products, including fuel-additive elements such as compounds of sodium, which cause dramatic catalyst deactivation of catalysts during selective catalytic reduction (SCR) of NO with NH3. There is an increasing demand to synthesize alkali-poisoning-resistant catalysts for industrial NH3-SCR applications. In this study, the as-synthesized Fe2O3/MoO3/TiO2 exhibits a high degree of resistance toward Na2SO4 poisoning during the NH3-SCR reaction. With 500 μmol g-1 Na+ poisoning, Fe2O3/MoO3/TiO2 showed approximately 95% (or more) of its original activity throughout the entire temperature rage. Even with 700 μmol g-1 Na+ poisoning, Fe2O3/MoO3/TiO2 still performed well. The 500 and 700 μmol g-1 Na+ loadings dictate that, on average, SCR catalysts could be exposed to alkali-rich and highly dusty environments for more than 14 000 and 20 000 h, respectively. The layered MoO3 building block is used as a binding buffer and sandwiched between the active phase and TiO2 support to provide sufficiently stable binding sites for Na2SO4 poison and to present alkali blocking of the surface active phase. Our findings provide useful information regarding the use of MoO3 as a safety buffer for developing functional NH3-SCR catalysts with enhanced alkali-poisoning-resistant performance and long lifetimes.