Preparation Of Pt/M-SiO₂ Catalysts And Their Catalytic Performance For Dehydrogenation Of Propane

As one of the most important organic chemical products,propylene is also the basic raw material for plastics,rubber and fiber.Its demand will gradually increase in the future.Therefore,it is extremely important to increase the production of propylene.At present,the main production processes for the production of propylene can be divided into two categories:traditional processes and emerging processes.With the depletion of oil resources and other issues,traditional production technologies are no longer able to meet the growing demand for propylene.Propane is an important part of natural gas and its reserve is very rich in China.The catalytic dehydrogenation of propane to propylene can increase propylene production in some extent.In this thesis,the paper used porous SiO₂ nanoparticles as carrier.The carrier is decorated by doping the transition metal Mn,Fe,Co,Ni,Cu and Zn species to activate the carrier surface.And a series of Pt-based catalysts were prepared by using Pt as the active component.The catalysts were characterized by XRD、SEM、TEM、N₂ adsorption-desorption、UV-Vis DRS、Raman、H₂-TPR and ICP.The catalysts were tested by gas chromatography.The relationship between the physicochemical properties and catalytic activity of catalysts doped with different transition metals were studied.The main conclusions of this thesis are as follows:（1）A series of transition metal doped SiO₂ supported Pt-based catalysts were prepared by emulsion method and impregnation method,and denoted as Pt/M-SiO₂（M=Mn,Fe,Co,Ni,Cu,Zn）.The catalytic performance was tested for propane dehydrogenation.It is found that the Pt-based catalysts doped with Mn and Fe species show relatively high activity and stability,while the catalysts doped with transition metals Co,Ni,Cu and Zn species inhibit the catalytic dehydrogenation of Pt-based catalysts.（2）A series of Mn-doped Pt/Mn-SiO₂ catalysts were prepared by emulsion method and impregnation method.The catalytic performance was tested for propane dehydrogenation.The results show that Mn species are highly dispersed on the surface of the support for the Pt/Mn-SiO₂ catalysts with low Mn-doped amount（Mn≤0.5 wt%）.With the increase of Mn doping amount,the crystallinity of Mn₃O₄ increase,and the dispersion of Pt becomes better by doping Mn metal.When the Mn-doped amount is 0.5wt%,the Pt/Mn-SiO₂ catalyst shows the highest catalytic performance.The initial conversion of propane is 56.5%,and the selectivity of propylene is 95.3%.After 6 h of reaction,the conversion of propane is 54.7%,and the selectivity of propylene is 98.3%。（3）A series of Fe-doped Pt/Fe-SiO₂ catalysts were prepared by emulsion method and impregnationmethod.Thecatalyticperformancewastestedforpropane dehydrogenation.The results show that Fe species are highly dispersed on the surface of the support for the Pt/Fe-SiO₂ catalysts.When the Fe-doped amount is 0.4 wt%,the Pt/Fe-SiO₂ catalyst shows the highest catalytic performance.The initial conversion of propane is 57.6%,and the selectivity of propylene is 90.8%.After 6 h of reaction,the conversion of propane is 51.1%and the selectivity of propylene is 98.0%.