Study Of New Process For Producing High Purity Isobutene

Isobutene,as an important petrochemical product,is widely used for preparing various industrial synthesis of raw materials and intermediates.The high purity isobutene refers to the mass fraction of isobutene is more than 99.5%,which can be used in the synthesis of higher value-added chemical products,such as Methyl Methacrylate,Isobutylene Isoprene Rubber and High Activity Polyisobutylene,etc.Currently,high purity isobutene is extracted from C4 fraction by MTBE cracking,which is most widely used method at home.However,this process has many disadvantages,for example,its reaction requires higher temperature and the crude isobutene contains much more by-products which could cause the separation difficulties.In this research,the distillation column is combined with fixed bed reactor to from a catalytic distillation tower.Based on this,a new catalytic distillation process is created.This paper studies technology that is comprised of isobutene hydration and tert-Butanol dehydration by the new process.The first part,effects of reaction pressure,feed flow of C4,space velocity of the C4 fraction(C4,24.40% isobutene),the molar ratio of H2O/C4 and temperature on the conversion of isobutene and the selectivity and yield of tert-Butanol are studied.Finally,the best condition of isobutene hydration process is obtained,under the above condition,the conversion of isobutene is 80.07%,the selectivity of tert-Butanol is 99.96%.Especially,water was introduced into the system from both the top and middle part of the reactor.The results of optimization proves that top-feeding water could absorb tert-Butanol in off-gas and the middle-feeding water could be conducive to control reaction temperature.The second part,effects of the feed position,space velocity of the tert-Butanol,top-feeding water flow,kettle heating temperature,reaction pressure,mass of catalyst in column on the composition distribution of off-gas,conversion of tert-Butanol and the selectivity of isobutene are studied.Finally,the best condition of tert-Butanol dehydration process is obtained,under the above condition,the purity of isobutene is 99.98%,the conversion of tert-Butanol is 99.89%,the selectivity of isobutene is 99.97%.The results of experiment shows that the new process has some advantages of simple process,little pollution,low cost,easy operation,high conversion rate,good selectivity and high purity of products.