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Deactivation and coke formation on nickeltungsten supported on silica-alumina catalysts / Yacine Rezgui in Industrial & engineering chemistry research, Vol. 47 n°12 (Juin 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 n°12 (Juin 2008) . - p. 4056–4062 Titre : Deactivation and coke formation on nickeltungsten supported on silica-alumina catalysts Type de document : texte imprimé Auteurs : Yacine Rezgui, Auteur ; Miloud Guemini, Auteur Année de publication : 2008 Article en page(s) : p. 4056–4062 Note générale : Bibliogr. p. 4061-4062 Langues : Anglais (eng) Mots-clés : Nickel−tungsten  supported;  Silica-alumina  catalysts;  Coke;  Temperatureprogrammed  oxidation Résumé : Nickel−tungsten oxides supported on silica−alumina catalysts were submitted to the coking reaction with n-octane at 150, 250, and 300 °C. The characteristics of deposited coke with different times on stream were studied using the temperature-programmed oxidation (TPO) technique. The results revealed that the strength and density of acid sites as well as the reaction temperature affect the nature of the coke formed: at 300 °C, it was observed that for the WT7 catalyst, the most acidic solid, there were two peaks corresponding to two kinds of coke recorded in TPO profiles, while at 150 °C only one peak was observed. On the other hand, for the WT4 catalyst, the less acidic sample, only the soft coke was observed. In addition, the oxidation temperature of coke shifted to higher values with high medium acid sites concentration and high temperature values with the increase of coke deposits. Besides, coke molecules interacted preferentially with the most acidic sites, which was confirmed by the strong deactivation in the first reaction stages, especially for the WT7 catalyst. For the regeneration tests, the collected data suggested that the coked WT4 catalyst showed a good combustion behavior; it was regenerated at 500 °C for 1 h, whereas the coked WT7 could not be regenerated at this temperature. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071407g [article] Deactivation and coke formation on nickeltungsten supported on silica-alumina catalysts [texte imprimé] / Yacine Rezgui, Auteur ; Miloud Guemini, Auteur . - 2008 . - p. 4056–4062. Bibliogr. p. 4061-4062 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 n°12 (Juin 2008) . - p. 4056–4062 Mots-clés : Nickel−tungsten  supported;  Silica-alumina  catalysts;  Coke;  Temperatureprogrammed  oxidation Résumé : Nickel−tungsten oxides supported on silica−alumina catalysts were submitted to the coking reaction with n-octane at 150, 250, and 300 °C. The characteristics of deposited coke with different times on stream were studied using the temperature-programmed oxidation (TPO) technique. The results revealed that the strength and density of acid sites as well as the reaction temperature affect the nature of the coke formed: at 300 °C, it was observed that for the WT7 catalyst, the most acidic solid, there were two peaks corresponding to two kinds of coke recorded in TPO profiles, while at 150 °C only one peak was observed. On the other hand, for the WT4 catalyst, the less acidic sample, only the soft coke was observed. In addition, the oxidation temperature of coke shifted to higher values with high medium acid sites concentration and high temperature values with the increase of coke deposits. Besides, coke molecules interacted preferentially with the most acidic sites, which was confirmed by the strong deactivation in the first reaction stages, especially for the WT7 catalyst. For the regeneration tests, the collected data suggested that the coked WT4 catalyst showed a good combustion behavior; it was regenerated at 500 °C for 1 h, whereas the coked WT7 could not be regenerated at this temperature. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071407g