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Coke formation and characterization during 1-hexene isomerization and oligomerization over H-ZSM-5 catalyst under supercritical conditions / Jiawei Wang in Industrial & engineering chemistry research, Vol. 48 N° 17 (Septembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7899–7909 Titre : Coke formation and characterization during 1-hexene isomerization and oligomerization over H-ZSM-5 catalyst under supercritical conditions Type de document : texte imprimé Auteurs : Jiawei Wang, Auteur ; Faiza Hassan, Auteur ; Peter I. Chigada, Auteur Année de publication : 2009 Article en page(s) : pp. 7899–7909 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : 1-hexeneIsomerization  Oligomerization  Catalysts Résumé : The isomerization and oligomerization of 1-hexene was studied over ZSM-5 catalyst under sub- and supercritical conditions within a down-flow fixed bed reactor in the temperature range of 220−250 °C and pressure range 10−70 bar. The catalyst activity and the product selectivity were found to be dependent on the operation conditions. Reactions were carried out over beds with 10 and 0.5 g catalyst, the smaller bed being used to simulate coking in the top layer of the larger bed. The conversion of 1-hexene over the 10 g bed of catalyst was in the range 83−99%, depending upon the operating conditions and was stable during the test period. An increase of the reaction temperature from 220−250 °C led to higher selectivity toward oligomerization, as did increases in reaction pressure in the range 10−70 bar. The amount of coke deposited on the catalysts decreased from 18.8 wt % at 235 °C and 10 bar in the subcritical region to 10.4 wt % at 235 °C and 40 bar in the supercritical region. DRIFTS showed that deposited coke is mainly polyolefinic. Nitrogen sorption showed that following initial shallow pore filling over shorter contact times, the pore mouth subsequently became blocked and coke mainly formed on the outside of the zeolite crystallites. When operating with 0.5 g catalyst, some deactivation occurred under subcritical conditions, although not under supercritical conditions. It appeared that with the smaller catalyst mass oligomers were retained within the pore structure of ZSM-5. The results of the study demonstrate that adjustment of the operating temperature and pressure can be used to tune the product selectivity of the reaction and the total amount of coke deposited upon the catalyst is reduced by operating under supercritical conditions. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801466d [article] Coke formation and characterization during 1-hexene isomerization and oligomerization over H-ZSM-5 catalyst under supercritical conditions [texte imprimé] / Jiawei Wang, Auteur ; Faiza Hassan, Auteur ; Peter I. Chigada, Auteur . - 2009 . - pp. 7899–7909. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7899–7909 Mots-clés : 1-hexeneIsomerization  Oligomerization  Catalysts Résumé : The isomerization and oligomerization of 1-hexene was studied over ZSM-5 catalyst under sub- and supercritical conditions within a down-flow fixed bed reactor in the temperature range of 220−250 °C and pressure range 10−70 bar. The catalyst activity and the product selectivity were found to be dependent on the operation conditions. Reactions were carried out over beds with 10 and 0.5 g catalyst, the smaller bed being used to simulate coking in the top layer of the larger bed. The conversion of 1-hexene over the 10 g bed of catalyst was in the range 83−99%, depending upon the operating conditions and was stable during the test period. An increase of the reaction temperature from 220−250 °C led to higher selectivity toward oligomerization, as did increases in reaction pressure in the range 10−70 bar. The amount of coke deposited on the catalysts decreased from 18.8 wt % at 235 °C and 10 bar in the subcritical region to 10.4 wt % at 235 °C and 40 bar in the supercritical region. DRIFTS showed that deposited coke is mainly polyolefinic. Nitrogen sorption showed that following initial shallow pore filling over shorter contact times, the pore mouth subsequently became blocked and coke mainly formed on the outside of the zeolite crystallites. When operating with 0.5 g catalyst, some deactivation occurred under subcritical conditions, although not under supercritical conditions. It appeared that with the smaller catalyst mass oligomers were retained within the pore structure of ZSM-5. The results of the study demonstrate that adjustment of the operating temperature and pressure can be used to tune the product selectivity of the reaction and the total amount of coke deposited upon the catalyst is reduced by operating under supercritical conditions. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801466d

Deactivation during 1-hexene isomerization over zeolite Y and ZSM5 catalysts under supercritical conditions / Faiza Hassan in Industrial & engineering chemistry research, Vol. 50 N° 12 (Juin 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 12 (Juin 2011) . - pp. 7161-7171. Titre : Deactivation during 1-hexene isomerization over zeolite Y and ZSM5 catalysts under supercritical conditions Type de document : texte imprimé Auteurs : Faiza Hassan, Auteur ; Jiawei Wang, Auteur ; Peter I. Chigada, Auteur Année de publication : 2011 Article en page(s) : pp. 7161-7171. Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Zeolite  catalysts Résumé : Catalytic deactivation caused by coking was studied in zeolite Y and ZSM5 during 1-hexene isomerization under subcritical and supercritical conditions. The effects of varying temperature and pressure, from 220 to 250 degrees C and from 10 to 70 bar, respectively, on conversion and coke deposition were studied in both zeolites. Thermogravimetric analysis (TGA) data, diffuse reflectance infrared Fourier transform spectra (DRIFTS), and nitrogen sorption isotherms for fresh and coked catalysts were compared. In zeolite Y an exponential decay in conversion was observed with the rate of deactivation being slower at supercritical conditions at 235 degrees C and 40 bar than subcritical conditions at 235 degrees C and 10 bar. It is thought that in zeolite Y the micropores with diameter 7.4 angstrom could accommodate coke molecules leading to the observed deactivation; however, in ZSM5 the micropores of 5.3-5.6 angstrom diameter were too small to accommodate coke molecules, and thus coke was deposited outside the zeolite crystals within the mesopores of the alumina binder. Although zeolite Y deactivated, while ZSM5 did not, the use of a supercritical fluid reaction environment enabled the conversion at 235 degrees C, 40 bar to be maintained at 42% over zeolite Y, which was higher than the conversion of 34% over ZSM5 catalyst under the same conditions. Operating with supercritical fluid led to the partial alleviation of the significant coking effects observed with zeolite Y and improved its viability for use in this reaction compared with the performance of ZSM5. DEWEY : 660 ISSN : 0888-5885 En ligne : http://opus.bath.ac.uk/24601/ [article] Deactivation during 1-hexene isomerization over zeolite Y and ZSM5 catalysts under supercritical conditions [texte imprimé] / Faiza Hassan, Auteur ; Jiawei Wang, Auteur ; Peter I. Chigada, Auteur . - 2011 . - pp. 7161-7171. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 12 (Juin 2011) . - pp. 7161-7171. Mots-clés : Zeolite  catalysts Résumé : Catalytic deactivation caused by coking was studied in zeolite Y and ZSM5 during 1-hexene isomerization under subcritical and supercritical conditions. The effects of varying temperature and pressure, from 220 to 250 degrees C and from 10 to 70 bar, respectively, on conversion and coke deposition were studied in both zeolites. Thermogravimetric analysis (TGA) data, diffuse reflectance infrared Fourier transform spectra (DRIFTS), and nitrogen sorption isotherms for fresh and coked catalysts were compared. In zeolite Y an exponential decay in conversion was observed with the rate of deactivation being slower at supercritical conditions at 235 degrees C and 40 bar than subcritical conditions at 235 degrees C and 10 bar. It is thought that in zeolite Y the micropores with diameter 7.4 angstrom could accommodate coke molecules leading to the observed deactivation; however, in ZSM5 the micropores of 5.3-5.6 angstrom diameter were too small to accommodate coke molecules, and thus coke was deposited outside the zeolite crystals within the mesopores of the alumina binder. Although zeolite Y deactivated, while ZSM5 did not, the use of a supercritical fluid reaction environment enabled the conversion at 235 degrees C, 40 bar to be maintained at 42% over zeolite Y, which was higher than the conversion of 34% over ZSM5 catalyst under the same conditions. Operating with supercritical fluid led to the partial alleviation of the significant coking effects observed with zeolite Y and improved its viability for use in this reaction compared with the performance of ZSM5. DEWEY : 660 ISSN : 0888-5885 En ligne : http://opus.bath.ac.uk/24601/