Study On The Catalytic Oxidation Of Toluene On Modified Mn-based Catalysts

As a common precursor of two key pollutants–ozone and PM_2.5,the control and treatment of VOCs is a very important for the improvement of the air quality.Catalytic oxidation is a very effective method for treating VOCs,and the core of its technology rests with the research and development of efficient,stable and low-cost catalysts.In this research,toluene was picked as the reaction gas and the influence of acid treatment on the catalytic oxidation of manganese-based composite oxide was explored by taking manganese-based composite oxide as the research object,and the main results were as follows:（1）The effect of acid treatment on the catalytic oxidation of toluene by Cr Mn composite oxide was investigated.Experimental results show that acid treatment can effectively improve the activity of Cr Mn catalysts for the catalytic oxidation of toluene.And different acid treatment times will also cause different effects.The Cr Mn-Ac-3 catalyst obtained after 3 hours of treatment with 1 M acetic acid completed 90%conversion of 1500 ppm toluene at 209°C.The characterization results showed that electrons were transferred on the surface of the Cr Mn catalysts after acid treatment.The addition of acid will promote the occurrence of Mn³⁺disproportionation reaction,form more Mn⁴⁺to cause a large number of surface defects,accelerate the cycle of oxygen species,and thus promote the catalytic oxidation reaction.（2）The effect of acid treatment on the catalytic oxidation of toluene by Cu Mn composite oxides was explored.The experimental results show that acid treatment will make Cu Mn catalysts have better ability to catalyze the oxidation of toluene,and the Cu Mn-Ac-6 catalysts obtained after 6 hours of treatment with 1 M acetic acid has completed 90%conversion of 1500 ppm toluene at 213°C,which is 70°C lower than that of Cu Mn catalysts without acid treatment.This may be due to the reaction of acid with Cu Mn catalysts surface Cu element to create more defects,and the formation of Cu-O bond fracture Cu vacancy affects the bond energy strength of Mn-O,so that the catalysts has better redox ability and thus improves catalytic performance.The effect of acetic acid on Cu Mn catalysts treatment is stronger than that of nitric acid,which may be that nitric acid dissolves too many Cu ions and destroys the synergy between Cu Mn₂O₄ and CuO on Cu Mn catalysts.