Study On The Mechanism Of Formaldehyde Catalytic Reaction Over Gold-based Catalysts Anchored By Attapulgite

The treatment of formaldehyde(HCHO)pollution has become the focus of research in the field of environmental protection today.Thermal catalytic oxidation technology is widely used for the removal of HCHO pollutants because of its high removal efficiency,simple operation and no secondary pollution.Among them,Au-based catalysts have good prospects for HCHO catalytic oxidation reactions.However,the current Au-based catalysts have weak oxygen activation ability and are prone to sintering at high temperatures.Therefore,this work improves the oxygen activation ability and high-temperature sintering resistance of Au-based catalysts through the optimization of the attapulgite clay(ATP),the doping of transition metal Ni or Mn,and the regulation of pretreatment atmosphere.We systematically investigate the HCHO reaction mechanism on Au-based catalysts,and the following main conclusions are drawn:(1)Different ratios of transition metal Nickel(Ni)were doped on Au-based catalysts to enhance the catalytic performance of bimetallic AuNi/ATP catalysts.Physical and chemical characterization results show that the addition of appropriate amount of Ni was beneficial to improve the dispersion and reduce the size of Au particles on the catalyst surface.The presence of Au promoted the interaction between Ni and ATP support to form a strong metal-support interaction,which significantly improved the HCHO oxidation performance of the catalysts.The catalyst with Au/Ni=0.5/20 showed the best HCHO oxidation activity,achieving more than 80%HCHO conversion efficiency at 50℃.(2)Doping of transition metal Manganese(Mn)to modulate the HCHO catalytic performance of AuMn/ATP catalysts.The XPS results indicated that the Au-Mn interaction facilitated the formation of Au3+ species and oxygen vacancies,and the addition of Mn improved the number of acid sites and the lattice oxygen mobility on the catalyst surface,which enhanced the oxygen activation ability of the catalyst.The Au-Mn interaction is optimal at Au/Mn=0.5/0.5,and about 90%conversion of HCHO can be obtained at 50℃ with good stability,which has some application potential.(3)The mechanism of HCHO catalytic oxidation reaction on AuMn/ATP catalysts was further investigated by In situ DRIFTS combined with Density Functional Theory(DFT).It was found that there were two HCHO oxidation mechanisms on AuMn/ATP catalysts,named OHT-Oa and OHB-OHT-Oa mechanism.The results of DFT calculations showed that the introduction of active metals led to the addition of more HCHO conversion pathways initiated by OHB on the catalyst surface,which facilitated the multi-path conversion of HCHO molecules and improved the overall HCHO conversion efficiency of the catalyst.Moreover,the Au-Mn-ATP interface always maintains the lowest energy barrier in the HCHO conversion pathway,indicating that the presence of Au-Mn interaction greatly promotes the oxidative decomposition of HCHO.(4)The effect of TPAOH solution addition and pretreatment atmosphere on the morphological structure of catalysts was investigated,and the study of their structure-activity relationship were investigated in combination with their HCHO reactivity.It showed that the desilylation produced by the appropriate amount of TPAOH solution was beneficial to the particle size reduction and uniform dispersion of Au particles on the sample surface,which promoted the HCHO catalytic oxidation.Moreover,the HCHO oxidation reaction activity of the Au0.5Mn0.5/ATP catalysts was closely related to the sample pretreatment atmosphere,in which the H2 atmosphere treatment was beneficial to the generation of small-sized Au particles on the sample surface and the enhancement of metal-support interaction on the catalysts.