Study On Aromatization Of Alkene In LPG To Synthesize High Octane Gasoline

Aromatization of alkene in LPG not only can synthesize desirable high octanegasoline rich in aromatics, but also can create qualified LPG for motors. Thisdissertation is mainly focused on the investigation of the effects of acidity andpore channel structures on the activity and stability of aromatization reaction.The reaction results of butene aromatization on various zeolites showed thatZSM-5 possessed favorable aromatization performance due to its uniform porestructure and suitable acidity. On the basis, the effects of reaction conditions onthe performance of alkene aromatization over HZSM-5 catalyst were investigated.The increase in reaction temperature and decrease in space velocity are favorablefor the enhancement in aromatization activity. The variation in reaction pressurehad no obvious influence on the aromatization performance. The aromatizationstability was somewhat improved under the H2 ambience. Binder in the catalystplayed a role only in enhancing physical strength of catalyst.It was first found that the reaction stability was influenced simultaneously byboth the total amount of acid sites and the acidity distribution. The reduction ofthe total acid sites and the maintenance of appropriate acidity distribution greatlyimproved the aromatization stability. A reduction in strong acid sites and presenceof a large amount of weak acid sites could not effectively improve thedeactivation behavior of catalyst.In order to further improve the reaction stability, a method of alkali-treatmentwas chosen. The treatment led to generation of mesopores while, no drasticchanges in the micropores and acidity occurred. The co-existence of microporesand mesopores resulted in change in the coking position and enhanced thetolerance to the carbonaceous deposit. Thus, reaction stability was greatlyenhanced. The results from pulse reaction and TPSR indicated that the first step inhydro-transfer reactions (i.e. formation of dienes or cycloolefins) was catalyzedonly by strong acid sites and can occur at lower temperatures than 200℃; thesubsequent hydro-transfer reactions can proceed on both strong and weak acidsites, while they required higher temperatures. Moreover, all hydro-transferreactions occurred on various acid sites, not on a separate acid site.