Research On Catalysts And Process For Dehydrogenation Of Isobutane Into Isobutene

Isobutene is an important organic raw material,which has a wide range of application value.In recent years,with the rapid development of downstream products of isobutene,the demand of isobutene grows rapidly.But the domestic production of isobutene is very little,isobutene has become one of scarce resources in our country.By contrast,isobutane is very rich while utilization rate is very low.Therefore,the development of the production of isobutene by dehydrogenation of isobutane into isobutene is competitive means,which can relieve the shortage of isobutene.Pt-Sn/γ-A1₂O₃ catalyst has been widely used in dehydrogenation industry for its high activity.In this work,Pt-Sn/γ-Al₂O₃ catalyst is studied.The effects of metal promoters and support of Pt-Sn/γ-Al₂O₃ based catalyst are investigated.the dehydrogenation process conditions are optimized,the regeneration stability of catalyst is researched.Firstly,the metal-Ce has been added to Pt-Sn-K/γ-Al₂O₃ catalyst,the result shows that Ce can significantly improve the dehydrogenation properties:segregating Pt into small size,improving the selectivity of butene,reducing the butane content of product and the content of carbon deposited on the surface of the catalyst.The effect of K has aslo been studied,but the result backfires.The dehydrogenation process conditions are optimized,it has been shown that when the reaction temperature is 600℃,volume space velocity of light hydrocarbons is 1000h-1,the ratio of hydrogen to hydrocarbon is 1:2,better performance can be achieved.Secondly,MgAl₂O₄ is used as support due to its good thermal stability.The result shows that the conversion of isobutane and the selectivity of isobutene are significantly increased.Thus,the dehydrogenation properties of MgAl₂O₄ is better than that of γ-Al₂O₃.The dehydrogenation process conditions are optimized too,it has been shown that when the reaction temperature is 600℃,volume space velocity of light hydrocarbons is 1100h-1,the ratio of hydrogen to hydrocarbon is 1:2,better performance can be achieved.Lastly,beause the catalyst is easily deactivated by coking and need to be regenerated frequently,so the regeneration stability of catalyst is an important aspect.The changes of structure and surface properties are studied.The temperature and oxygen concentration during the coke burning process is the two factors affecting the regeneration performance.The experimental results show that when the regeneration temperature is 450℃,the oxygen concentration is 1%,regeneration performance is better.