Preparation And Performance Of Low Temperature SCR Catalyst For Denitration Of Mn-Based Multi-Metal Oxides

The control of nitrogen oxides is an urgent objective requirement for national economic sustainable development and environmental protection.Nowadays,selective catalytic reduction technology（SCR）at low-temperature has attracted much attention in the field of denitrification because of its energy saving and low operating cost.However,the current low-temperature catalysts are still in the laboratory research stage and need to overcome many problems for the practical industrial application,such as its narrow temperature window,poor low-temperature N₂ selectivity and poor water and sulfur resistance.To overcome these problems,manganese-based multi-metal oxides were used as the research objects,and their low-temperature activity was modified and their action mechanism was studied.Firstly,4Ce-10Mn/TiO₂ catalyst was selected and the effects of impregnation,coprecipitation and reverse co-precipitation on the catalyst performance were investigated,and the preparation process of reverse co-precipitation was also optimized.It was found that the catalyst prepared by reverse co-precipitation method had the best low-temperature activity（T80=108°C,64°C lower than that of the impregnation method）.The reverse co-precipitation method can promote the interaction between active components,surface enrichment and uniform dispersion.It can also increase the specific surface area,the surface acidity and redox ability,and thus promote the SCR reaction.In situ FTIR analysis showed that both Br?nsted acidic sites and Lewis acidic sites existed in 4Ce-10Mn/TiO₂-RC and 4Ce-10Mn/TiO₂-I catalysts,and the NH₃-SCR reaction was controlled by both E-R mechanism.The 4Ce-10Mn/TiO₂ catalyst were modified with elemental compositing,and results showed that the Sb-composited could substantially improve the low-temperature water and sulfur resistance of the catalyst（NO conversion was increased from 45%to 75%in an atmosphere of 5%H₂O and SO₂ at 200°C）by activity measurements.The Sb-composited catalysts could not only improve the specific surface area,surface acid amount,Ce³⁺content,surface oxygen adsorption and redox ability,but also effectively protect the Br?nsted acid site and inhibit the sulfation of Mn⁴⁺,thus improve the sulfur resistance.In addition,the addition of Sm also improved the water and sulfur resistance of 4Ce-10Mn/TiO₂ catalysts at low temperature,and the optimum loading of Sm O_x was10%.The inhibition of catalyst agglomeration,higher concentration of chemisorbed oxygen,and more Br?nsted acid sites were the main factors to improve the low temperature water and sulfur resistance for the Sm-composited catalysts.