Selective Catalytic Oxidation of Ammonia over LaMAl11O19- (M = Fe, Cu, Co and Mn) Hexaaluminates Catalysts at high temperature in Claus Process
Ammonia selective catalytic oxidation at high temperature method was innovatively proposed to substitute the traditional combustion method to remove the ammonia impurity in claus process. In the present work, transition metals (Fe, Cu Co and Mn) substituted La-hexaaluminate catalysts were synthesized and investigated for ammonia selective catalytic oxidation (NH3-SCO) reaction at high temperature. It was observed that Cu substituted catalysts can achieve the highest N2 yield at around 520 ℃. It was confirmed that the conversion of NH3 was closely related to the reducibility of the prepared catalyst. Particularly, it was observed that the molecular O2 cannot be dissociative adsorption on the prepared catalyst surface. But both lattice oxygen and gas-phase O2 can participate in NH3-SCO, and gas-phase O2 were even more favorable under the experimental conditions. It was evidenced that the NH3-SCO reaction over prepared catalysts followed the i-SCR mechanism. Moreover, monodentate nitrates were the mainly reactive intermediates to form N2. Therefore, the development of high-temperature SCO technology and the efficient catalyst was beneficial for the sustainable development of chemical industry.