Study Of Monolithic Catalysts Using Different Carriers Supported Mn-Fe-Ce For Performance Of Selective Catalytic Reduction Of NO_x With NH₃

The nitrogen oxides produced by fixed source burning is one of the main pollutants for many environmental problems,which can cause acid rain,photochemical pollution and greenhouse effect, and make a negative impact on the environment and human health. The selective reduction technology of NH₃ is the main technology to eliminate NO_x. Currently, the vast majority of commercial catalysts are V₂O₅-WO₃（MoO₃）/TiO₂, which have high catalytic activity in the range of 300-400 °C. But flue gas temperature of desulphurization device is lower than 300 °C. Therefore, the designed catalyst should not only prevent sulfate deposition caused by pore blocking, but also avoid energy waste of tail gas reheating, the research focused on the catalytic activity of SCR catalysts with low temperature（<200 °C）.In this paper, ZSM-5 and Al-SBA-15 are respectively used as carriers to prepare powder catalysts with Mn, Fe, Ce for the active component, then, and slurry coating method is used to prepare monolithic catalysts on cordierite ceramic substrate pretreated by oxalate. The optimum ratio of active components, impregnation sequence of active components, roasting temperatureof Al-SBA-15 carrier and the influence of Si/Al on NH₃-SCR catalytic reduction reaction are investigated, phase structure, surface element valence and the influence of pore structure parameters on the activity are analyzed combining with XRD, XPS, BET and TEM. Meanwhile, the life testing and sulfur resistance testing were carried out for 150 h on the fixed bed reactor with tail gas simulation. Main conclusions of this dissertation are as follows:（1） The catalytic reduction performance of NO for the cordierite catalyst prepared by the co-impregnation is stronger, when the active component ratio of the mass fraction of Mn, Fe, Ce is 1:1:1.（2） The optimal preparation conditions of the 10Mn-10Fe-10Ce/Al-SBA-15/CC catalyst for: the Al-SBA-15 powder carrier of Si/Al = 25, under air atmosphere calcination with 600 °C. The reaction temperature range of SCR activity above 90% is 210-390 °C.（3） The pore structure of 10Mn-10Fe-10Ce/Al-SBA-15/CC（25,600）catalyst is relatively uniform. Its structure is two-dimensional six-party mesoporous, and the average pore diameter is 3.8 nm. Al atom in the carrier AlSBA-15 by hydrothermal synthesis method successfully grafted on the molecular sieve skeleton with the higher degree of long range order.（4） XPS results showed that the surface active component of the best catalyst was higher.（5） The synergy of the coexistence Mn₂O₃-MnO₂, Fe₂O₃, CeO₂ facilitate the redox reaction between NH₃ and NO.（6） The amorphous oxidation state of active components, the chemical adsorption oxygen content and pore diameter of around 3.8 nm mesoporous materials is advantageous to the reaction NH₃-SCR reaction.（7） By comparing monolithic catalysts prepared different molecular sieve carrier, the catalytic activity of 10Mn-10Fe-10Ce/ZSM-5/CC is slightly superior,and longer service life. But its capacity to resist SO₂ and H₂O is still below the point of practical application.