Preparation Of Low Loading Metal Catalyst And Its Performance For Wet Catalytic Oxidation Of Ammonia

Ammonia wasterwater is widely produced in the process of industry,agriculture,and life.It is a pollutant with a large discharge and great harm.Ammonia nitrogen in wastewater can make water eutrophication.Nitrate generated by ammonia nitration will harm the health of life.Ammonia after volatilization is the main source of haze particles.Therefore,efficient removal of ammonia has always been a hot topic in environmental research.In some scenarios,the traditional ammonia removal process has some problems,such as instability,high investment or secondary pollution.Therefore,the development of a wet air oxidation ammonia removal process,which can oxidize ammonia nitrogen to N₂,will have broad application prospects.In this work,a highly dispersed heterogeneous metal catalyst was designed and successfully prepared by one pot method Ru@TiO₂.For catalytic wet air oxidation（CWAO）of ammonia.The characterization of these catalysts showed that some ruthenium atoms were uniformly dispersed on the surface of TiO₂ in the form of clusters,and some ruthenium atoms were embedded in the framework of TiO₂.This structure can provide excellent catalytic performance and ensure that Ru is not easy to leach.Application experiments show that:when using 0.5%Ru@TiO₂ The results showed that NH₃ was completely oxidized and the selectivity of N₂ was 100%after 6 h with catalyst,240℃and 2 MPa.In addition,a new reaction mechanism was proposed.In addition,Ru,Pd and Cu Single Metal Zr O₂ Catalysts and three different combinations of bimetallic Zr O₂ Catalysts were prepared by one pot method to catalyze wet air oxidation of ammonia nitrogen wastewater.XRD,SEM,TEM and XPS were used to characterize the catalysts and their supports.The results showed that the supported metals were evenly distributed on the supports and the particle size was small.In bimetallic catalysts,there are some electron transfer between metals and between metal and support.In addition to the stable and uniform immobilization of metal nanoparticles on the support,these interactions also affect the selectivity and conversion of the catalyst.In the study of catalytic performance,it is found that when Cu is doped in Ru,the conversion of the Ru_0.25Cu_0.25@Zr O₂ remains 100%,while the nitrogen selectivity reaches 63.5%,which is 8%higher than that of single metal Ru catalyst.It is proved that the electron transfer between Cu and Ru is conducive to the improvement of nitrogen selectivity.