Selective catalytic reduction of NOx with NH3 over TiO2 supported metal sulfate catalysts prepared via a sol-gel protocol

Due to the presence of SO2 in flue gas, SCR catalysts with high SO2 tolerance are in desperate required. However, except vanadium-based catalysts, most metal oxide catalysts exhibited low SO2 tolerance. In this research, CuSO4/TiO2, Fe2(SO4)3/TiO2, MnSO4/TiO2, Ce(SO4)2/TiO2 and CoSO4/TiO2 catalysts were prepared via a sol-gel protocol and used in NH3-SCR reaction. Low-temperature N2-sorbtion, XRD, FT-IR, XPS, H2-TPR, NH3-TPD and in situ DRIFTS were used to characterize the physicochemical properties of prepared catalysts. The presence of SO2 had little influence on the activity of all metal sulfate catalyst samples. Amongst, CuSO4/TiO2 performed the highest SCR activity and apparent activation energy on metal sulfate catalysts followed the sequence of CuSO4/TiO2 < Fe2(SO4)3/TiO2 < MnSO4/TiO2 < Ce(SO4)2/TiO2 < CoSO4/TiO2. Characterization results indicated that the amount of acid sites was the main factor which influenced catalytic activity of metal sulfate catalysts. NH3-SCR reaction at all metal sulfate catalysts followed the Eley-Rideal mechanism: NH3 was firstly adsorbed on surface acid sites (Lewis and Bronsted acid sites), and then reacted with gaseous NO and O2 to form N2 and H2O. Metal sulfate catalyst, especially CuSO4/TiO2, should be a promising candidate of vanadium-based SCR catalysts in NO reduction.