Experimental Study Of The Preparation Of Mn-Cu/TiO₂ Catalysts And Its NO Catalytic Oxidation Behavior At Low Temperature

The coal-fired power plant over 95% of NOx is NO, if NO could be partialy oxidized to NO2, then removal by wet method; it will be beneficial for developing resources economic society and circulated economy.The first step:catalytic oxidation of NO is crucial.The preparation of Mn-Cu/TiO2 and its catalytic oxidation of NO ability at low temperature were studied.The heterogeneous kinetic of NO oxidation was discussed and the catalytic oxidation-chemical absorption process was also simulated. The results provide the evidences for the industrialization application of the new NO oxidation catalysts.Firstly, combined characterization methods of BET, XRD, SEM,FT-IR and TG/DTA, the catalytic activities of a series of transition metal oxide catalysts M/TiO2 (M=Mn, Co, Ce, Fe, Cu, Cr, Ni, Zn and Zr) were screened under the fixed bed heterogeneous catalysis reaction setup. The Mn-Cu/TiO2 shows the best catalytic activity at low temperature.As P type semiconductors, MnOx and CuOx receive electorns much faster, absorb more oxygen on the surface;Cu2+ may substitute of Mn2+ in the lattice, result in decreasing the Fermi energy level and promoting the electric ability of P type semiconductor, so the reactants were absorbed faster and the catalytic oxidation reaction will be accelerated eventually. The effects of different preparation methods and conditions on the catalytic activity over Mn-Cu/TiO2 were investigated.It showed that activity components with 10% total loadings, Mn/Cu=2, supported on the TiO2 which was prepared by sol-gel method, impregnated, evaporated and calcinated at 300℃,exhibited the best effect of NO oxidation. Under the simulated flue gas conditions:300ppmNO and 10%O2 at a GHSV of 41324h-1,the NO conversion reached 50% at 220℃,as well as the highest NO conversion of 76.3% was reached at 300℃.A larger surface area(30.4m2/g)and pore volume(0.05mL/g) could be obtained at a relative lower calcination temperature(300℃),and contribute to a higher catalytic activity.Then, the effects of several different operation conditions (temperatures, NO concentrations, GHSV, O2 concentrations, the existence of H2O and SO2) on the catalytic activity of Mn-Cu/TiO2 were studied.The results appear that activity curve raised between 150～300℃,the decrease of GHSV and NO concentration or the increase of O2 concetration will both make the NO conversion increased.The catalyst appeared stable during the continuous experiments.The catalyst was almost not affected at 220℃when H2O was introduced in the stream;And showed anti-sulfur ability under a lower GHSV when large amount of SO2 were introduced.Moreover, the heterogeneous kinetic of NO oxidation over Mn-Cu/TiO2 catalyst was studied by experiments and calculations.Under the conditions of temperatures below 300℃and O2 concentration below 8%,the results indicated that the reaction order with respect to NO was 1.1061,while the reaction order with respect to O2 was 0.3972 and the energy of activation determined was 25757.05 J/mol.The effect of outer diffuse can be ignore basicly, however the inner diffuse can not.Lastly,200MW coal-fired power plant was simulated as example, combined of the catalytic oxidation of NO and ammonia absorption part, the simultaneous desulfurization and denitrification process was simulated by ChemCAD software.The results provided the reference for the industrialization.application.