Controlled Fabrication Of Alumina-based Hierarchical LDHs Compounds For Propane Dehydrogenation Reaction

Propane dehydrogenation reaction often uses the heterogeneous catalyst to enhance the reaction performance.The active metal Pt NPs are the main catalytic activity center,whose metal dispersion,size and shape will have an important effect on the catalytic performance for propane dehydrogenation reaction.In recent years,layered double hydroxides(LDHs)with unique structural features have been widely used in the field of catalysis,including MgAl-LDHs,ZnAl-LDHs,etc..When the LDHs are used as a catalyst carrier,bivalent metal hydroxide can confine the growth of metal introduced into the lattice during the roasting and reduction process.At the same time,the lattice induction of the layered double hydroxides is beneficial to the dispersion of the active metal.Based on the above advantages,we have prepared the different morphology hierarchically structured MgAl-LDHs to explore the influence of different carrier on catalyst active component,surface acidity and catalytic activity and stability.Some research results have been obtained,and the specific contents are as follows:1.By in situ growth technology,three kinds of hierarchical composite materials with different morphologies have been obtained.Meanwhile,three different morphologies of PtSn/5MAF,PtSn/15MAF and PtSn/30MAF catalysts have been prepared via a traditional impregnation process.The catalysts were characterized by XRD,TEM,SEM,TP series and so on.Finally,the catalytic conversion,selectivity and stability of the catalysts were investigated by propane dehydrogenation reaction.The results show that the different morphologies of catalysts have a great influence on the catalytic activity.The catalytic conversion,selectivity and stability of PtSn/15MAF catalyst are the best.2.The mesoporous Al2O3 carrier modified with different morphologies of MgAl-LDHs have been prepared successfully.Meanwhile,five kinds of catalysts including PtSn/Al203,PtSn/OMAL,PtSn/lMAL,PtSn/2.5MAL and PtSn/4MAL have been obtained via a traditional impregnation process.The properties of the catalysts were studied by XRD,TEM,SEM,XPS,TP series and so on.Finally,the catalytic conversion,selectivity and stability of the catalysts were investigated by propane dehydrogenation reaction.The results show that the catalytic activity of the mesoporous Al2O3 was improved significantly after the modification of the MgAl-LDHs,and the PtSn/2.5MAL catalyst showed the best performance of propane dehydrogenation and catalytic stability.3.In order to further improve the catalytic stability of the catalyst,Pt-CeO2@HMSiO2/(Al2O3@MgAl-LDHs)catalyst was prepared.Meanwhile,it was characterized by TEM,SEM,N2 adsorption-desorption,FT-IR,EDX and other instruments.The results show that the active component Pt-CeO2@HMSiO2 had strong thermal stability.Finally,the excellent catalytic stability of novel Pt-CeO2@HMSiO2/(Al2O3@MgAl-LDHs)catalyst has been demonstrated by using propane dehydrogenation reaction as a probe.