The Study Of Platinum-based Catalysts For Propane Dehydrogenation

There is an ever-increasing demand for propylene around the world, because propylene is a very important organic chemical intermediate used for the production of a wide variety of bulk chemicals. China has rich resources of liquefied petroleum gas and natural gas, which contain a lot of propane. This provides a good base for the manufacture of propylene by selective dehydrogenation of propane. Currently, the major route for propane dehydrogenation to propylene is Oleflex process of UOP. This process increases energy consumption and facility cost because it needs to be run above 600℃. Additionally, high temperatures cause severe coke deposition and sintering of the metal phase. Thus how to reduce the reaction temperature and maintain good conversion and selectivity at the same time is an urgent task.In this paper, propane dehydrogenation were conducted over supported Pt-based catalysts in the presence of hydrogen focusing on coke deposition and the corresponding deactivation. This work mainly contains the following two aspects:1. Pt-Sn/Al2O3 catalysts were synthesized by impregnation and tested in propane dehydrogenation. The effect about of metal loading, bimetallic ratio, catalyst reduction temperature, calcination temperature, reaction temperature, feed gas ratio and reaction time on the catalytic performance was explored systematically. It was found that 6:12 is the optimum molar ratio for Pt:Sn, and 550℃ is the optimum temperature for redunction and calcination. The effect of catalyst regeneration atmosphere on catalyst performance was investigated as well, focusing on the activation/poisoning effect on the active centers. By using TG, TPO-MS and a series of characterizations, the type and amount of coke deposited on the used catalysts was determined. It was revealed that oxygen atmosphere could efficiently remove the coke but sinter metal site; nitrogen atmosphere could graphitize the coke, which make the catalyst deactivation temporarily; hydrogen atmosphere could present better regeneration.2. By using co-impregnation method, we added three kinds of dopants Sn, Ga and Zn into Pt/Al2O3 catalyst, then changed the bimetallic ratio to prepare different catalysts. The effect about of bimetallic ratio on the activity of the catalysts was studied and the relationship between them was established. It was found that Sn is the best dopant for Pt-base catalyst in propane dehydrogenation reaction.