Coke Deactivation of Acid Sites on ZSM-5 Zeolite
Научная публикация
| Общее |
Язык:
Английский,
Жанр:
Статья (Full article),
Статус опубликования:
Опубликована,
Оригинальность:
Оригинальная
|
| Конференция |
Catalyst Deactivation 2001 : 9th International Symposium
07-10 окт. 2001
,
Lexington, KY
|
| Сборник |
Catalyst Deactivation 2001 : Proceedings of the 9th International Symposium,
7-10 October 2001, Lexington, KY USA
Сборник,
2001.
523 c. ISBN 978-0-444-50477-7.
|
| Журнал |
Studies in Surface Science and Catalysis
ISSN: 0167-2991
|
| Вых. Данные |
Год: 2001,
Том: 139,
Страницы: 77-84
Страниц
: 8
DOI:
10.1016/S0167-2991(01)80183-X
|
| Авторы |
Echevsky G.V.
1
,
Ayupov A.B.
1
,
Paukshtis E.A.
1
,
O’Rear D.
2
,
Kibby C.
2
|
| Организации |
| 1 |
Boreskov Institute of Catalysis, Ak. Lavrentiev Av. 5, Novosibirsk, 630090, Russia
|
| 2 |
Chevron Research and Technology Company, 100 Chevron Way, P.O. Box 1627, Richmond, CA, USA
|
|
Acid centers (AC’s) on ZSM-5 external surfaces remain active in catalysis and visible by IR spectroscopy under progressive accumulation of condensed coke structures on them. With increasing amounts of accumulated coke, the strengths of the AC’s gradually decrease as evidenced by catalysis results and changes in the frequencies of stretching vibrations of OH- groups after CO adsorption. The number of catalytically valuable AC’s remains constant up to monolayer coverage of the external zeolite surfaces. A scheme for a condensed coke structure growing on the outer surface of ZSM-5 crystals is suggested. Coke agglomerates, though linked to acid sites, nevertheless leave them accessible for the reagent molecules. Coke agglomeration proceeds at the expense of carbon atom addition at the active site, while the agglomerate itself “swims” over the zeolite crystal surface and is most likely linked to the silanol OH-groups. The larger the agglomerate, the higher its degree of condensation, the greater the delocalization of its electron density over the structure of condensed aromatic rings, the further the shift of its electron density onto the active site proton, and the weaker its active site.