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Effect of oxidizers on microwave-assisted oxidative degradation of poly(alkyl acrylates) / A. Marimuthu in Industrial & engineering chemistry research, Vol. 47 N°20 (Octobre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N°20 (Octobre 2008) . - P. 7538-7544 Titre : Effect of oxidizers on microwave-assisted oxidative degradation of poly(alkyl acrylates) Type de document : texte imprimé Auteurs : A. Marimuthu, Editeur scientifique ; Giridhar Madras, Editeur scientifique Année de publication : 2008 Article en page(s) : P. 7538-7544 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Effect  of  oxidizers  Microwave-assisted  oxidative  Poly(methyl  acrylate)  (PMA)  Poly(ethyl  acrylate)  (PEA) Résumé : The effect of oxidizers on the microwave-assisted oxidative degradation kinetics of poly(alkyl acrylates), namely, poly(methyl acrylate) (PMA), poly(ethyl acrylate) (PEA), and poly(butyl acrylate) (PBA), was studied. The molecular weight distributions were measured by gel permeation chromatography, and continuous distribution kinetic models were used to determine the degradation rate coefficients. The effect of alkyl group substituents on the microwave-assisted oxidative degradation of poly(alkyl acrylates) was also investigated. The degradation rate of poly(alkyl acrylates) decreased with an increase in the number of carbon atoms of the alkyl substituents and thus followed the order PMA > PEA > PBA, while the activation energy increased with the length of alkyl group substituents. The rate coefficients of hydrogen abstraction and oxidative random chain scission were found to be independent of the oxidizer and dependent only on the nature of the polymer. The differences in the overall degradation rate of poly(ethyl acrylate) in the presence of different oxidizing agents were only dependent on the rate of oxidizer dissociation. This is the first study that shows that the degradation rate of the polymer in the presence of any oxidizer can be predicted by knowing only the thermal dissociation rate constant values of the oxidizer, which can be easily obtained from existing literature. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie7017349 [article] Effect of oxidizers on microwave-assisted oxidative degradation of poly(alkyl acrylates) [texte imprimé] / A. Marimuthu, Editeur scientifique ; Giridhar Madras, Editeur scientifique . - 2008 . - P. 7538-7544. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N°20 (Octobre 2008) . - P. 7538-7544 Mots-clés : Effect  of  oxidizers  Microwave-assisted  oxidative  Poly(methyl  acrylate)  (PMA)  Poly(ethyl  acrylate)  (PEA) Résumé : The effect of oxidizers on the microwave-assisted oxidative degradation kinetics of poly(alkyl acrylates), namely, poly(methyl acrylate) (PMA), poly(ethyl acrylate) (PEA), and poly(butyl acrylate) (PBA), was studied. The molecular weight distributions were measured by gel permeation chromatography, and continuous distribution kinetic models were used to determine the degradation rate coefficients. The effect of alkyl group substituents on the microwave-assisted oxidative degradation of poly(alkyl acrylates) was also investigated. The degradation rate of poly(alkyl acrylates) decreased with an increase in the number of carbon atoms of the alkyl substituents and thus followed the order PMA > PEA > PBA, while the activation energy increased with the length of alkyl group substituents. The rate coefficients of hydrogen abstraction and oxidative random chain scission were found to be independent of the oxidizer and dependent only on the nature of the polymer. The differences in the overall degradation rate of poly(ethyl acrylate) in the presence of different oxidizing agents were only dependent on the rate of oxidizer dissociation. This is the first study that shows that the degradation rate of the polymer in the presence of any oxidizer can be predicted by knowing only the thermal dissociation rate constant values of the oxidizer, which can be easily obtained from existing literature. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie7017349

Selective catalytic reduction of NOx / Sounak Roy in Industrial & engineering chemistry research, Vol. 47 N° 23 (Décembre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9240–9247 Titre : Selective catalytic reduction of NOx : mechanistic perspectives on the role of base metal and noble metal ion substitution Type de document : texte imprimé Auteurs : Sounak Roy, Auteur ; A. Marimuthu, Auteur ; Parag A. Deshpande, Auteur Année de publication : 2009 Article en page(s) : p. 9240–9247 Note générale : Chemistry engineering Langues : Anglais (eng) Mots-clés : NOx  Catalytic  Reduction  Noble  Metal  Ion  Substitution Résumé : Selective catalytic reduction (SCR) of NO by NH3 in presence of excess oxygen is an industrially and environmentally important reaction. Determining a suitable catalyst substituted with noble metals or base metal ions with a suitable reaction mechanism is important. In this study, ionically substituted Mn and Pd in TiO2 catalysts were synthesized by the solution combustion technique and examined for SCR activity. A seven-step reaction mechanism was proposed to incorporate the role of NH3 oxidation in the SCR reaction that shows minima in the NO concentration profile. Both modeling and experimental results show that the reduction of NO in SCR condition follows the order Ti0.9Mn0.1O2-δ > Ti0.89Mn0.1Pd0.01O2-δ > Ti0.99Pd0.01O2-δ. However, the hydrogen uptake study showed that the noble metal ion (Pd2+) substituted TiO2 has better reducibility than the base metal ion (Mn3+) substituted TiO2. The rate of ammonia oxidation by different catalysts followed the reverse order such as that of NO reduction. This clearly indicates that catalysts with higher reducibility and that which exhibit higher rates of ammonia oxidation have poor SCR activity. Thus, the base metal ion substitution is better than noble metal ion substitution for SCR. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8010879#afn2 [article] Selective catalytic reduction of NOx : mechanistic perspectives on the role of base metal and noble metal ion substitution [texte imprimé] / Sounak Roy, Auteur ; A. Marimuthu, Auteur ; Parag A. Deshpande, Auteur . - 2009 . - p. 9240–9247. Chemistry engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9240–9247 Mots-clés : NOx  Catalytic  Reduction  Noble  Metal  Ion  Substitution Résumé : Selective catalytic reduction (SCR) of NO by NH3 in presence of excess oxygen is an industrially and environmentally important reaction. Determining a suitable catalyst substituted with noble metals or base metal ions with a suitable reaction mechanism is important. In this study, ionically substituted Mn and Pd in TiO2 catalysts were synthesized by the solution combustion technique and examined for SCR activity. A seven-step reaction mechanism was proposed to incorporate the role of NH3 oxidation in the SCR reaction that shows minima in the NO concentration profile. Both modeling and experimental results show that the reduction of NO in SCR condition follows the order Ti0.9Mn0.1O2-δ > Ti0.89Mn0.1Pd0.01O2-δ > Ti0.99Pd0.01O2-δ. However, the hydrogen uptake study showed that the noble metal ion (Pd2+) substituted TiO2 has better reducibility than the base metal ion (Mn3+) substituted TiO2. The rate of ammonia oxidation by different catalysts followed the reverse order such as that of NO reduction. This clearly indicates that catalysts with higher reducibility and that which exhibit higher rates of ammonia oxidation have poor SCR activity. Thus, the base metal ion substitution is better than noble metal ion substitution for SCR. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8010879#afn2