Pt Catalysts Over Modified Alumina For Propane Dehydrogenation

Propylene is an important chemical raw material, which is of increasing demand in chemical industry year by year. The catalytic dehydrogenation of propane is one of the main processes to produce propylene, where high efficient catalyst is the key issue. Alumina has been extensively used as a support for propane dehydrogenation reaction due to its strong mechanical strength and high surface areas. However, Al2O3also has some features that are not favorable for propane dehydrogenation, such as its too strong acidity, which makes Al2O3supported catalyst quickly deactivated. Therefore, modification of alumina support is one of promising paths to enhance catalytic performance in propane dehydrogenation.In this work, two types of modified alumina supports were prepared, including CCA and AS supports, which were used as supports for Pt catalysts and evaluated in propane dehydrogenation reaction.CCA(Carbon Covered Alumina) supports were prepared through thermal cracking of different carbon sources at high temperature. Results demonstrated that acidity and coke formation of Pt/CCA catalysts had negative correlation with carbon content. The effect of carbon content of CCA supports that were prepared through thermal cracking of sucrose was also discussed. The results showed that CCA supports with carbon content of8.9%exhibited comparably better catalytic performance, however, propylene selectivity of this catalyst was still very low, only75%.AS(tin-modified Alumina) supports were prepared through tin-addition in sol-gel process of pseudoboehmite. The characterization and evaluation results showed that tin introduced by sol-gel method was in highly-dispersed oxidative state on alumina surface. The highly-dispersed tin oxides could enhance the mutual interaction between support and tin compound which stabilized the Sn as oxidation state in Pt-Sn catalysts. Therefore, the metallic Pt particles were isolated by highly-dispersed tin oxide species, which higher Pt dispersion and catalytic activity of Pt/AS catalysts lay in. AS7.5support with0.5%Pt loading showed the best catalytic performance among different tin loading supports with initial propane conversion33%and propylene selectivity97%.