Activation Oxidation Of Methane By Doped Noble Metal Oxide Clusters

Methane,the simplest low-carbon alkane molecule,as the main component of natural gas,shale gas,biogas and pit gas,is an extremely important non-renewable and clean energy.In addition to the burning of heating or power generation,the efficient catalytic conversion of it into chemicals of higher value(such as hydrogen,methanol,formaldehyde,ethanol,acetylene,hydrocyanic acid and benzene)is of great significance for modern industrial production and sustainable development of human society.Because of the complexity of the surface reaction of the associated condensed phase in the actual catalyst system(such as the interference of carrier effect and solvent effect),the understanding of the surface reaction mechanism of the catalyst is stilt not very clear.The gas-phase mass spectrometry experiment combined with density functional calculation to study the reaction of noble metal doped heteronuclear oxide clusters with methane and other small molecules can understand the atomic mechanism of the surface reaction of related condensed phases from the molecular level,which can provide important guidance for the rational design of efficient,practical and economic methane catalyst systems.The main contents of this paper are as follows:Catalytic activation of CH4 by gold silicon heteronuclear oxide clusters.Doped heteronuclear oxide cluster Au(SiO2)1-3O-with variable sizes are generated by laser sputtering cluster method.After selected by quadrupole mass selector,the clusters are entered into linear ion trap reactor to react with CH4 or CD4,and then the product and non-reactive cluster ions enter reflection time mass spectrometer for detection.The results of mass spectrum experiment showed that the small size of cluster Au(SiO2)1-2O-in the reaction with CH4 can produce Molecular absorption(MA)product ion Au(SiO2)1-2OCH4-and dissociative product ion(SiO2)1-2OH-.However,when the larger size cluster Au(SiO2)3O-reacted with CH4,only the dissociative product(SiO2)3OH-appeared.The density functional theory(DFT)calculates three reaction processes and mechanisms,and it is found that these two different experimental phenomena are accompanied by two different reaction mechanisms,that is,the change of reaction mechanism caused by size variation.Further studies have found that the properties of different coordination on the supported oxide clusters of noble metal Au atoms have great influence on their reactivity.