Study On Preparation And Performance Of Isobutene Catalyst For Dehydration Of Biological Isobutanol

Bio-isobutanol,a renewable energy source,can be used directly as a biofuel or dehydrated to generate isobutene.As an important basic organic chemical raw material,isobutylene is used to produce various organic chemical raw materials and fine chemicals such as butyl rubber and polyisobutylene.However,there is no natural source of isobutylene,and the raw materials for production are excessively dependent on the increasingly scarce oil resources and urgently need to be supplemented by new processes.Isobutene is produced by dehydration of biological isobutanol.Most of the liquid products are water.It is an environmentally friendly new way to produce isobutylene.In this paper,pore structure and acidity of Al₂O₃ support were modified by adding pore-enlarging agent and metal element,and the performance of modified Al₂O₃catalyst in dehydration of isobutanol to isobutylene was investigated.Different solid acid catalysts were screened to find a suitable isobutanol dehydration catalyst.The pore structure of the Al₂O₃ support was modified with a pore-enlarging agent,and XRD,mercury intrusion,and NH₃-TPD characterization were performed on the Al₂O₃ after pore expansion.The results showed that by adding different proportions of pore-enlarging agents,four kinds of pore expansion ratios?0,10%,20%,30%?of?-Al₂O₃ catalysts were successfully prepared to achieve effective pore structure of?-Al₂O₃ catalysts.Modulate.The pore size of the catalyst after pore expansion is significantly increased from 1000 to 7000 nm.When the amount of pore-enlarging agent added reaches 30%,the macroporous ratio of the?-Al₂O₃ catalyst reaches 50%.Under the conditions of heavy hourly space velocity of 12 h^-1and 330?,the conversion of isobutanol increased with the increase of the ratio of expanded pores,and the selectivity of isobutylene did not change much,and remained at about 93%.Among them,the?-Al₂O₃ catalyst with 30%pore-enlarging agent had the best catalytic performance,and the isobutanol conversion rate reached 97%.The K,Ce and Ba elements were loaded onto a?-Al₂O₃ support with a 30%pore-enlarging agent in an equal volume impregnation method.The effect of surface acidity on the dehydration of isobutanol to isobutene was investigated.The results showed that the acidity of?-Al₂O₃ catalyst was significant after loading K,Ba,and Ce.When the impregnation amount is 3%,the decrease of the medium-strong acid amount of K?-Al₂O₃ catalyst is most obvious,followed by Ba,Ce is the weakest,and the conversion rate of the three isobutanol also decreases with the decrease of the acid amount.The addition of Ce slightly increases the selectivity of isobutene while also lowering the isobutanol conversion.Overall,Ce-modified?-Al₂O₃ did not achieve the desired catalytic effect.The effects of process conditions on the dehydration of isobutanol on?-Al₂O₃catalyst with 30%pore-enlarging agent were investigated.It was found that the conversion rate of isobutanol increased when the reaction temperature increased,the feed airspeed decreased,or the isobutanol water content increased.The selectivity of isobutene was mainly affected by the reaction temperature,and the reaction temperature increased slowly.decline.The more appropriate process conditions:reaction temperature 330?³50?,heavy hourly space velocity 6 h^-122 h^-1,isobutanol water content 0¹0%wt.In industrial production,when the reactor is operated at a reaction temperature greater than 330?,an isobutanol raw material having a water content of 0to 10%wt can be directly used to improve production efficiency.The performance of?-Al₂O₃ catalyst with 30%pore-enlarging agent was the best.At high speed,the isobutylene yield was stable at about 93%in the reaction time of 148 h.