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Diffusional effects in nickel oxide reduction kinetics / Peter Erri in Industrial & engineering chemistry research, Vol. 48 N°1 (Janvier 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N°1 (Janvier 2009) . - p. 4-6 Titre : Diffusional effects in nickel oxide reduction kinetics Type de document : texte imprimé Auteurs : Peter Erri, Editeur scientifique ; Arvind Varma, Editeur scientifique Année de publication : 2009 Article en page(s) : p. 4-6 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Nickel  oxide  Industrial  catalyst Résumé : Nickel is widely used as an industrial catalyst and has recently been investigated as an oxygen carrier in chemical looping combustion (CLC), which is a novel approach for power generation that offers inherent CO2 capture. However, prior studies have reported a wide range of activation energy values for nickel formation from the reduction of NiO by hydrogen. In the present work, this reaction was investigated using the Friedman isoconversional method for a series of thermogravimetric curves, which were obtained at varying heating rates. The intrinsic activation energy for the reduction of NiO was observed to be in the range of 91.8−94.5 kJ/mol, whereas values of 42.6 kJ/mol and ∼0 kJ/mol were found at intermediate and high heating rates, respectively, which correspond to intermediate and high temperatures. This demonstrates the presence of internal and external mass-transfer limitations during the reaction, and it provides a likely explanation for the varying activation energy values reported in prior work. Therefore, these findings emphasize the importance of assessing diffusional effects in the determination of reaction kinetics. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071588m [article] Diffusional effects in nickel oxide reduction kinetics [texte imprimé] / Peter Erri, Editeur scientifique ; Arvind Varma, Editeur scientifique . - 2009 . - p. 4-6. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N°1 (Janvier 2009) . - p. 4-6 Mots-clés : Nickel  oxide  Industrial  catalyst Résumé : Nickel is widely used as an industrial catalyst and has recently been investigated as an oxygen carrier in chemical looping combustion (CLC), which is a novel approach for power generation that offers inherent CO2 capture. However, prior studies have reported a wide range of activation energy values for nickel formation from the reduction of NiO by hydrogen. In the present work, this reaction was investigated using the Friedman isoconversional method for a series of thermogravimetric curves, which were obtained at varying heating rates. The intrinsic activation energy for the reduction of NiO was observed to be in the range of 91.8−94.5 kJ/mol, whereas values of 42.6 kJ/mol and ∼0 kJ/mol were found at intermediate and high heating rates, respectively, which correspond to intermediate and high temperatures. This demonstrates the presence of internal and external mass-transfer limitations during the reaction, and it provides a likely explanation for the varying activation energy values reported in prior work. Therefore, these findings emphasize the importance of assessing diffusional effects in the determination of reaction kinetics. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071588m