Preparation And Performance Of Pt Catalysts For Propane Combustion

It is well known that volatile organic compounds(VOCs)are not only a major source of environmental pollution,but also a threat to human health.Growing strict regulations result in world-wide attention on the abatement of VOCs.The catalytic combustion method has the advantages of relatively low treatment temperature,low energy consumption,easy control of reaction,and low secondary pollution,and thus it is the most effective way to eliminate alkane VOCs.Propane is a representative alkane compound that is extremely difficult to be totally oxidzed and its catalytic combustion is usually taken a model reaction to evaluate the performance of various catalyst systems.The most commonly employed catalysts are noble metals and transitional metal oxides.Noble metal catalysts have received much attention for their excellent activity,selectivity and stability.In this work,the catalytic performance of Pt catalysts for complete oxidation of propane was studied.The crucial parameters governing the catalytic behaviors were discussed based on detailed catalytic tests and catalyst characterizationsThe detailed contents of this work are as follows1.Catalytic propane combustion was performed on a series of supported Pt/AlF3 catalysts.These catalysts are very active and stable in the reaction,and the 0.2Pt/AlF3 catalyst gives the highest specific reaction rate of 207.3 ?mol gpt-1s-1 at 220?.The 1Pt/AlF3 is much more active than the reference Pt/Al2O3 catalyst,due to its higher content of metallic Pt species than that in the Pt/Al2O3.Furthermore,turnover frequency(TOF)based on Pt dispersion increases with the surface concentration of metallic Pt0 in the catalyst,suggesting these species might be the active sites.Furthermore,synergistic roles of metallic and oxidized Pt species are found,as the TOFs calculated based on surface Pt0 concentration reaches a maximum at the Pt0/P2+ molar ratio of about 1.Such optimal Pt0/Pt2+ ratio implies the requirement of Pt0-Pt2+ pair in the reaction,probably due to the activation and cleavage of C-H bond on metallic Pt atom and the sequential oxidation on the oxidized Pt atoms.2.Nb-doped Pt/Al2O3 catalysts were synthesized by a co-impregnation method and tested for the complete oxidation of propane.The Nb-doped catalysts show higher activity compared to the Pt/Al2O3,and the activity gradually increases with increasing Nb loading.Based on the XPS and NH3-TPD results,it is found that new acidic sites are generated in the Nb-doped Pt/Al2O3 catalyst,which leads to an increase in the Pto content of the catalyst surface and improve the catalytic activity of the catalyst.