Experimental Study Of Manganese-based Composite Oxide Catalyst On Low Temperature SCR Denitration

The massive emission of nitrogen oxides?NO_x?is one of the reasons of air pollution and the existing vanadium-tungsten-titanium type catalysts have low selective catalytic reduction?SCR?activity to removing NO_x at low temperature,so new environmentally friendly catalysts have become the focus of current research.In this paper,we using palygorskite loaded different crystal types of manganese dioxide and chemically synthesizing copper-manganese LDH precursors to obtaining copper-manganese oxide by calcination,respectively.The synthetic manganese-based composite oxide type low-temperature SCR denitration catalysts were applied to ammonia selection catalytic reduction?NH₃-SCR?reaction.Meanwhile,the physical and chemical properties and reaction mechanism of the catalysts were explored by XRD,BET,NH₃-TPD,H₂-TPR,FT-IR and XPS.In this paper,in-situ DRIFT analysis of the catalyst was also conducted to study its mechanism of SO₂ poisoning in the SCR reaction.The following results were obtained:?1?Compared with other palygorskite-supported catalysts,?-Mn O₂/PG catalysts exhibit the best catalytic activity in the temperature range of 50-400?,and have good stability,N₂ selectivity and water resistance.Water vapor has an inhibitory effect on the low-temperature denitration of the catalyst,but this inhibitory effect was reversible.The high specific surface area,more acid sites and surface active elements were the reasons why the?-Mn O₂/PG catalyst has the best catalytic activity.?2?When the ratio of copper to manganese was 3,calcination temperature was 400?and the prepared Cu₃Mn O_x catalyst was in the range of 150-300?,its optimal NO_xremoval efficiency is 93-96%.The excellent NH₃-SCR activity of Cu₃Mn O_x catalyst was related to its high specific surface area,high redox capacity and more surface active oxygen and Mn⁴⁺content.?3?Both the E-R mechanism and the L-H mechanism participate in the denitration reaction of the catalyst.SO₂ can react with the metal active components on the surface of the catalyst,resulting in the sulfation of the surface active components of the catalyst and to deactivate the catalyst.The effect of H₂O on SCR activity was reversible.?4?Introducing transition metal elements on the basis of existing catalysts,the results show that Ce and Co have a significant effect on improving sulfur resistance,but failed to maintain a stable high level.