کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
10239216 46048 2005 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Cracking of pentenes to C2-C4 light olefins over zeolites and zeotypes
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی کاتالیزور
پیش نمایش صفحه اول مقاله
Cracking of pentenes to C2-C4 light olefins over zeolites and zeotypes
چکیده انگلیسی
The cracking of 2-methyl-2-butene was carried out as a model reaction of C4+ olefins cracking by using of various zeolite and zeotype catalysts to obtain light olefins, such as ethylene and propylene. Only ZSM-5 and ZSM-11 zeolites with 10-MRP with intersecting channels and acid sites concentration ranging between 0.03 and 0.1 mmol/g exhibit high and stable selectivity to C2-C4 olefins at high conversion level. Active and selective catalysts were prepared by three different methods: direct synthesis of H-ZSM-5 with high Si/Al ratio, steaming of H-ZSM-5 and “partial” ammonium ion exchange of Na-ZSM-5. Neither H-(Al)ZSM-5 with high concentration of acid sites nor H-(Fe)ZSM-5 are suitable catalysts as they catalyze hydrogen-transfer reactions yielding paraffins and aromatics, showing the importance of low concentration and high strength of acid sites for cracking activity-selectivity. High yield of butenes in the reaction products indicates that pentenes cracking in 10-MRP proceeds via formation of voluminous carbenium ion intermediates demanding sufficient space inside of zeolites channel. Therefore, the presence of intersection of 10-MRP is very important. While in ZSM-5 and ZSM-11 zeolites the low amount of active sites mainly situated in the pores intersection is sufficient to achieve high activity-selectivity in the case of mono-dimensional 12-MRP zeolites such as mordenite and ZSM-12 and also with 10-MRP ferrierite much higher total acid concentration is necessary, as vast of the acid sites, situated out of the main channel do not take part in the reaction. AlPO-11 materials with narrow mono-dimensional channel exhibit low conversion with majority of β-scission cracking mechanism independently on the acid sites concentration.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Applied Catalysis A: General - Volume 287, Issue 2, 22 June 2005, Pages 203-213
نویسندگان
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