Preparation And Characterization Of Pt/BN And Pt-V/SiO₂ Catalysts For Catalytic Combustion Of Propane

Alkanes are one of the most difficult volatile organic compounds?VOCs?to be totally oxidized because of their inert chemical nature.The catalytic total oxidation of propane is a representative model reaction to evaluate the performance of catalyst system.This work reported catalytic total oxidation of propane over Pt-based catalysts.A series of Pt/BN and Pt-V/SiO₂ catalysts were prepared and tested for this reaction.Combined with various characterizations such as XRD,TEM,XPS,H₂-TPR,H₂ chemisorption,reaction mechanisms were thoroughly discussed.Detailed contents of this work are as follows:1.A series of Pt/BN catalysts were prepared by impregnation method with hexagonal boron nitride?h-BN?as carrier and platinum nitrate as precursor.The Pt catalysts supported on hexagonal BN?Pt/BN?are highly active and stable for propane combustion,with the highest specific reaction rate of 92.3?mol?s^-1?g^-1 and turnover frequency of 0.037 s^-1 obtained on a 0.2Pt/BN catalyst at 220?.The Pt particles are preferentially deposited at the grain boundary of the support at low Pt loadings.When the Pt loading is high,the Pt species tend to disperse on the surface.The Pt oxide in the catalyst could be partially reduced to the metallic state by propane during the reaction,which is beneficial for the improvement of activity,indicating that metallic Pt might be the active sites.The highly dispersed Pt particles stabilized at the grain boundary of BN could be more easily reduced in the reaction than those on the surface and thus are more active.Moreover,kinetic investigation reveals that the apparent activation energy of the Pt species at the grain boundary(111.6±8.0kJ?mol^-1)is much lower than that on the surface(172.4±16.5 kJ?mol^-1),suggesting different reaction pathways on these catalysts and the possible participation of the grain boundary of the BN support in the reaction.2.A series of Pt-V/SiO₂ catalysts were synthesized by a co-impregnation method and tested for propane combustion to investigate the effects of vanadium contents on the catalytic behaviors.It is found that the Pt-V/SiO₂ catalysts are highly active and stable for propane combustion,with the highest specific reaction rate of 153.2?mol?s^-1?g^-1 obtained on a 2Pt-10V/SiO₂ catalyst at 200?.And almost 100%conversion of propane is achieved on a pre-reduced 2Pt-3V/SiO₂-H catalyst at 220?.Various characterizations of the Pt-V/SiO₂ catalysts show that the catalytic behavior is closely related to the surface properties of the Pt species.The Pt⁰ content in the catalyst is a key factor in governing the catalyst activity,as the reactivity generally increases with the content of Pt⁰ in the catalyst.Moreover,the addition of vanadium enhances surface acidity of the catalyst and stabilizes the Pt species in low valence state,which improves its performance.Besides,it is found that the Pt⁰ content is almost constant when the vanadium loading reaches a certain level,indicating that the VOx species may have a special role in stabilizing the Pt⁰ content in the catalyst.