n-Heptane cracking on dealuminated HBEA zeolites
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| Title: | n-Heptane cracking on dealuminated HBEA zeolites |
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| Authors: | Marques, J.P.1,2, Gener, I.2, Lopes, J.M.1 jmlopes@popsrv.ist.utl.pt, Ramôa Ribeiro, F.1, Guisnet, M.2 |
| Source: | Catalysis Today. Oct2005, Vol. 107-108, p726-733. 8p. |
| Subjects: | Catalytic cracking, Alkenes, Petroleum refining, Aliphatic compounds |
| Abstract: | Abstract: n-Heptane cracking was carried out at 450°C over HBEA samples resulting from dealumination of the same parent HBEA zeolite by three different methods: steaming, treatment with solution of hydrochloric acid or ammonium hexafluorosilicate. With all the dealuminated samples, the main reaction products were C3 and C4 alkenes and alkanes (iso/n >1) which suggests a successive isomerization-cracking process with the participation of a carbocation chain mechanism. Dealumination causes a decrease in the catalytic activity. A linear relation was found between the activity and the square of protonic acid site concentration suggesting that n-heptane cracking is a demanding reaction. A small amount of methane, ethylene and ethane can also be observed, which indicates the participation of the protolytic process in n-heptane cracking. The relative significance of this process depends very much on the method used for dealumination: it decreases with acid and ammonium hexafluorosilicate treatments that eliminates most of the extraframework Al Lewis species and increases with steaming. This suggests that Lewis acid sites play a significant role in the protolytic cracking of n-heptane. [Copyright &y& Elsevier] |
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| Database: | Engineering Source |
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