Synthesis Of MnO_x-CeO₂/UiO-66 Catalyst And Its Performance In CO-SCR Under Oxygen Rich Condition

The flue gas produced by the burning of fossil fuels contains two major air pollutants,nitrogen oxides（NO_x）and carbon monoxide（CO）,they can cause a series of environmental problems and seriously endanger human health when discharged into the atmosphere.Selective catalytic reduction of NO_x（SCR）is the most effective denitration technology currently.Among them,selective catalytic reduction of NO_X with CO（CO-SCR）attract increasing attention because of its ability to remove both NO_X and CO pollutants.Catalysts are the core and research hotspots of CO-SCR.However,current catalysts still have disadvantages such as poor oxygen resistance and poor denitration efficiency under low temperature conditions,which make it difficult to realize application.Metal-organic frameworks（MOFs）have exhibited outstanding properties including high specific surface area,regular pore structure,and strong adsorption capacity which make them suitable for used as catalyst carriers.Therefore,this study aims to develop a catalyst with activity at low temperature and oxygen rich environment,choose the UiO-66 which exhibits excellent stabilities among MOFs as the carrier,and choose manganese（Mn）and cerium（Ce）as active components to synthesis MnO_x-CeO₂/UiO-66 catalyst,and the performance of catalyst is optimized through aspects of the ratio of manganese to cerium,loading amount and carrier modification.The main contents of the study are as follows:（1）The MnO_x-CeO₂/UiO-66 catalysts are synthesized by impregnation method to investigate the influence of the ratio of manganese to cerium and the loading of active components on the catalytic denitration performance under 7%oxygen content.The physical and chemical properties of the catalyst are also analyzed.The results show that there is an interaction among manganese,cerium and UiO-66 support which lead to higher catalytic performance.The number of hydroxyl groups in the catalyst increases when the proportion of cerium increases,which is conducive to gas adsorption and oxidation,and can improve the CO oxidation performance of the catalyst.When the loading is too high,the active material agglomerate on the surface of catalyst cause greatly reduce in specific surface area and pore volume,result in the drop of catalytic performance.The catalyst shows best performance when the concentration of manganese solution is 30%and the ratio of manganese to cerium is 25:10 where more than 60%denitration efficiency as well as complete oxidation of CO is achieved in the range of 250-300℃.（2）For the problems of tremendous reduction in specific surface area and agglomeration of active materials and destruction of pore structure after the active components are loaded,the UiO-66 is prepared with a modulation process in which hydrochloric acid of different volumes are chosen as modulators.The influence of modulator addition on the catalytic performance under 7%oxygen content and the physicochemical properties of the catalyst are investigated.The results show that UiO-66 carrier shows higher crystallinity and larger crystal grains after the addition of modulator.When the modified carrier is used to synthesis the catalyst,its morphology does not change greatly and the active substance are not prone to agglomeration.Thus,larger specific surface area and higher pore volume can be obtained,which boost to the adsorption and diffusion of gas in the catalyst.At the same time,the catalyst prepared by the modified carrier has better thermal stability which helps catalyst to achieve a wider operating temperature range.The MnO_x-CeO₂/UiO-66 catalyst synthesized by the modified carrier with hydrochloric acid addition shows better denitration and CO oxidation performance.（3）In a word,the MnO_x-CeO₂/UiO-66 catalyst has high activity at low temperature and oxygen rich environment and the result provides a good reference for the application of MOFs in CO-SCR technology.