Low-temperature Aromatization Of C₄ Liquified Petroleum Gas Over Nano-zeolites

The aromatization of C₄LPG at low temperature is very significant for the comprehensive utilization of C₄LPG,because it can efficiently convert butenes into high octane number gasoline.This study mainly focuses on the influence of reaction conditions on the low-temperature aromatization of C₄LPG over nano-sized ZSM-5 zeolitic catalyst DL-5.It is found that,when the reaction temperature is at no more than 300℃,the major reactions of C₄LPG over DL-5 catalyst are the oligomerization of butenes and the cracking of the oligomers,in this low temperature range the deactivation of the catalyst is very fast.When the reaction temperature is beyond 330℃,the reactions of butane oligomers cracking,hydride-shift and aromatization become predominated.In such a high temperature range the coking deactivation of the catalyst can be slowdown effectively.The conversion of butane over DL-5 catalyst proceeds only at reaction temperature above 400℃.The influences of both feed velocity and reaction pressure on the reactions are investigated.It is observed that they have little influence on the conversion of butenes,but have obvious influence on the conversion of butane and the formation of propane.The decrease of feed velocity or increase of the reaction pressure would lead to the increase of butane conversion and the increase of propane yield.The reaction pathway of C₄LPG over DL-5catalyst is proposed,and the thermodynamics of the primary reactions is discussed.Besides,catalysts contain bi-nano-zeolites have been prepared from both nano-ZSM-5 and nano-Beta by changing the ingredient ratio of the two zeolite.Based on this,the catalytic properties of the bi-nano-zeolite catalysts in the low-temperature aromatization of C₄LPG have been investigated.It is found that the introduction of nano-beta zeolite can enhance the reaction of isomerization and the conversion of butane while keeping the aromatization activity.These results may be helpful for catalyst development.Finally,the economic aspect of the low-temperature aromatization technology of C₄LPG for the production of high octane number gasoline was estimated by using ASPEN PLUS 11.1 software.