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Fuel, Vol.255, 2019
Insights into the highly efficient Co modified MnSm/Ti catalyst for selective catalytic reduction of NOx with NH3 at low temperature
A novel cobalt-decorated MnSm/Ti catalyst was proposed for removal of NOx at low temperatures. Catalytic performance have been tested and the physicochemical properties were comprehensively characterized using X-ray diffraction, N-2 adsorption, X-ray photoelectron spectroscopy, NH3-temperature programmed desorption, H-2-temperature programmed reduction and in situ diffuse reflectance infrared Fourier transform spectroscopy. The best 5CoMnSm/Ti catalyst achieved above 90% NOx conversion at 100-200 degrees C with a gas hourly space velocity of 60,000 h(-1). The 5CoMnSm/Ti catalyst possesses increased Lewis acid sites and enhanced redox property attributed to the synergistic interaction among Mn, Co and Sm, which are beneficial to the chemisorption and activation of NO and NH3. The facile electron transfer through the redox cycle of Mn3++ Co3+ <-> Mn4++ Co2+ and the enhanced oxygen mobility can maintain the surface high valence metal ions and chemisorbed oxygen at high concentration. All these factors elevate the low-temperature catalytic activity of 5CoMnSm/Ti catalyst towards selective catalytic reduction of NOx with NH3. The bidentate nitrate is a reactive nitrate species after Co doping, which can participate in the NH3-SCR. The reaction over the 5CoMnSm/Ti catalyst can proceed through both Eley-Rideal and Langmuir-Hinshelwood mechanisms, in which the Eley-Rideal mechanism is predominant owing to its fast reaction rate.