| Propylene and isobutylene are important chemical raw materials.Currently,with the rapid development of olefin derivatives related industries,the demand for olefins sharply increased.But the light alkanes as the byproducts in refinery are the mixture of C3 and C4,so it will increase the costs and reduce the profits if the components are firstly separated and then dehydrogenated.Therefore,to develop a direct catalyst for the dehydrogenation of mixed alkanes is the great significance.This paper explored the dehydrogenation performance of propane and the mixture of propane and isobutane as feedstocks on the Pt-Sn-Ce-K/γ-Al2O3 catalyst respectively,and modified catalyst for the dehydrogenation of the mixed feedstocks,and explored the optimum process conditions,as well as investigated the regeneration stability of the catalyst.Firstly,the process conditions of propane dehydrogenation on Pt-Sn-Ce-K/γ-Al2O3catalyst were optimized.The effect of propane dehydrogenation was best at a temperature of610℃,space velocity of 500h-1,and hydrogen hydrocarbon ratio of 0.5,the initial conversion rate was 44%and the selectivity could be maintained at around 95%.Meanwhile,according to thermodynamic data,we could calculate that the equilibrium constant of propane dehydrogenation was 0.38 and the equilibrium conversion rate was 30%with the optimum conditions.Secondly,the active components of catalyst used for the dehydrogenation of mixed feedstocks were modified.The dehydrogenation performance of three series of catalysts with different K,Na,Li contents were investigated,and the process conditions were optimized with the most active catalyst:Pt-Sn-Ce-Na/γ-Al2O3.The results showed that under the optimum conditions:temperature of 580℃,space velocity of 1000h-1 and hydrogen hydrocarbon ratio of0.5,the initial conversion rate of paraffins was 44%and the selectivity of olefins was up to 95%.Meanwhile,the stability of the regenerated catalyst was studied under optimum conditions.The result showed:in continuous 24h reaction-regeneration-24h reaction process,the selectivity of products was always stable at around 95%and the conversion rate was over 30%,indicating that this catalyst has a good stability of regeneration.Finally,the situation of magnesium aluminate spinel as a catalyst support for the dehydrogenation of mixed feedstocks was preliminarily explored.The results showed that the catalyst supported by magnesium aluminate spinel had a low mechanical strength,so that the stability of the catalyst during the dehydrogenation was poor. |
