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| Content Provider | Springer Nature Link |
|---|---|
| Author | Guisnet, M. Andy, P. Boucheff, Y. Gnep, N.S. Travers, C. Benazzi, E. |
| Copyright Year | 1998 |
| Abstract | The nature of the active species responsible for butene isomerization over aged HFER samples is reexamined in the light of the change in the product yields at very short time-on-stream and of the reversible and irreversible increases in weight of the zeolite during the reaction. At very short time-on-stream, the selectivity of butene isomerization is that expected from a dimerization-cracking process, in particular simultaneous formation of isobutene, propene and pentenes. A rapid decrease of all the yields is observed with time-on-stream; however, for isobutene but not for the other products, the initial decrease is followed (after 10 minutes-on-stream) by an increase. The decrease in the yield can be related to the formation of carbonaceous compounds (``coke'') which block the access to the pores, while the increase in isobutene yield can be explained by the development of a new isomerization mode which is very selective to isobutene. This new mode could be catalyzed by carbonaceous compounds and/or by reaction products which are shown to be retained inside the pores during the reaction. It is proposed that at short time-on-stream the increase in isobutene yield is due to an autocatalytic reaction, n-butene isomerization occurring on t-butyl carbenium ions formed by adsorption of isobutene molecules (which are slowly desorbed from the pores) on the protonic sites of the zeolite. At long time-on-stream, the active species would be benzylic carbocations formed from carbonaceous compounds trapped in the pores near the outer surface of the crystallites. |
| Starting Page | 159 |
| Ending Page | 164 |
| Page Count | 6 |
| File Format | |
| ISSN | 1011372X |
| Journal | Catalysis Letters |
| Volume Number | 50 |
| Issue Number | 3-4 |
| e-ISSN | 1572879X |
| Language | English |
| Publisher | Kluwer Academic Publishers-Plenum Publishers |
| Publisher Date | 1998-01-01 |
| Publisher Place | New York |
| Access Restriction | One Nation One Subscription (ONOS) |
| Subject Keyword | Physical Chemistry Industrial Chemistry/Chemical Engineering Catalysis Pharmacy |
| Content Type | Text |
| Resource Type | Article |
| Subject | Chemistry Catalysis |
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