Effect of preheating treatment on the measured heats of adsorption of organic probes on clays with different surface compositions / Nayef El-Thaher in Industrial & engineering chemistry research, Vol. 51 N° 20 (Mai 2012)  

Public ISBD [article]  inIndustrial & engineering chemistry research > Vol. 51 N° 20 (Mai 2012) . - pp. 7022–7027 Titre : Effect of preheating treatment on the measured heats of adsorption of organic probes on clays with different surface compositions Type de document : texte imprimé Auteurs : Nayef El-Thaher, Auteur ; Phillip Choi, Auteur Année de publication : 2012 Article en page(s) : pp. 7022–7027 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Preheating treatment Adsorption Organic Clays Résumé : The effect of column preconditioning temperature (Tcp) on the measured heats of adsorption of selected aliphatic and aromatic compounds for kaolinite and illite, two clay minerals commonly encountered in the oil sands industry, was studied using the technique of inverse gas chromatography (IGC). Tcp was varied from 100 to 340 °C. Our results showed that, as Tcp was increased from 100 to 170 °C, the heats of adsorption (affinities) of the selected aliphatic solutes for kaolinite increased slightly, but those for illite stayed nearly the same. At higher Tcp values (170–230 °C), solute adsorption exhibited essentially no dependence on Tcp for both kaolinite and illite. This observation is attributed to the decreasing hydrophilicity for kaolinite from 100 to 170 °C, but not for kaolinite from 170 to 230 °C or for illite from 100 to 230 °C. Higher Tcp values (230–340 °C) were used for the two aromatic solutes (benzene and toluene), and it was found that their heats of adsorption for illite were significantly reduced (50%) whereas those for kaolinite were insensitive to Tcp. It is believed that this observation can be attributed to the loss of surface water as a result of increasing temperature. Here, departure of surface water would decrease the number of Lewis acid sites on the tetrahedral surfaces, thereby reducing the attractive interaction between the surfaces and the π bonds of the aromatic solutes at elevated Tcp. Because illite contains only tetrahedral surfaces, the measured heats of adsorption of benzene and toluene decreased with increasing temperature. However, in the case of kaolinite, which contains 1:1 tetrahedral and octahedral surfaces, this effect was offset by the increasing attractive interaction between the exposed hydroxyl moieties on the octahedral surfaces and the π bonds of the aromatic probes. As demonstrated in this work, the measured heat of adsorption depends on Tcp. Therefore, care must be taken when comparing solute affinity for various types of minerals based on IGC measurements. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie202739x [article] Effect of preheating treatment on the measured heats of adsorption of organic probes on clays with different surface compositions [texte imprimé] / Nayef El-Thaher, Auteur ; Phillip Choi, Auteur . - 2012 . - pp. 7022–7027. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 20 (Mai 2012) . - pp. 7022–7027 Mots-clés : Preheating treatment Adsorption Organic Clays Résumé : The effect of column preconditioning temperature (Tcp) on the measured heats of adsorption of selected aliphatic and aromatic compounds for kaolinite and illite, two clay minerals commonly encountered in the oil sands industry, was studied using the technique of inverse gas chromatography (IGC). Tcp was varied from 100 to 340 °C. Our results showed that, as Tcp was increased from 100 to 170 °C, the heats of adsorption (affinities) of the selected aliphatic solutes for kaolinite increased slightly, but those for illite stayed nearly the same. At higher Tcp values (170–230 °C), solute adsorption exhibited essentially no dependence on Tcp for both kaolinite and illite. This observation is attributed to the decreasing hydrophilicity for kaolinite from 100 to 170 °C, but not for kaolinite from 170 to 230 °C or for illite from 100 to 230 °C. Higher Tcp values (230–340 °C) were used for the two aromatic solutes (benzene and toluene), and it was found that their heats of adsorption for illite were significantly reduced (50%) whereas those for kaolinite were insensitive to Tcp. It is believed that this observation can be attributed to the loss of surface water as a result of increasing temperature. Here, departure of surface water would decrease the number of Lewis acid sites on the tetrahedral surfaces, thereby reducing the attractive interaction between the surfaces and the π bonds of the aromatic solutes at elevated Tcp. Because illite contains only tetrahedral surfaces, the measured heats of adsorption of benzene and toluene decreased with increasing temperature. However, in the case of kaolinite, which contains 1:1 tetrahedral and octahedral surfaces, this effect was offset by the increasing attractive interaction between the exposed hydroxyl moieties on the octahedral surfaces and the π bonds of the aromatic probes. As demonstrated in this work, the measured heat of adsorption depends on Tcp. Therefore, care must be taken when comparing solute affinity for various types of minerals based on IGC measurements. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie202739x

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