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Denitrification of water with activated carbon-supported metallic catalysts / Luisa Calvo in Industrial & engineering chemistry research, Vol. 49 N° 12 (Juin 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 12 (Juin 2010) . - pp. 5603–5609 Titre : Denitrification of water with activated carbon-supported metallic catalysts Type de document : texte imprimé Auteurs : Luisa Calvo, Auteur ; Miguel A. Gilarranz, Auteur ; José A. Casas, Auteur Année de publication : 2010 Article en page(s) : pp. 5603–5609 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Nitrates  Catalytic  reduction  Trickle  bed  reactor Résumé : The catalytic reduction of nitrates with hydrogen in aqueous phase was studied in a trickle bed reactor using different activated carbon-supported metallic catalysts. Continuous experiments were performed at ambient conditions (25 °C and 1 atm) at different space-time values in the range of 25.8−103.3 kgcat h/mol. The activity of monometallic catalysts based on Pd, Rh, Cu, and Ni was low in all the cases, yielding nitrate conversions below 15%. The introduction of a second metal produced a synergistic effect, improving the catalytic activity and the selectivity toward N2. That increase in activity was more pronounced when using Pd or Rh combined with Cu, reaching nitrate conversions above 80% in the case of Pd−Cu catalysts. The catalyst with a Pd/Cu mass ratio of 2:1 (Pd050Cu025) also showed the lowest selectivity to nitrite and the highest to N2. Metal leaching was always below detection limits for Pd and Rh, whereas in the case of Cu and Ni, significant metal concentrations were found in the reaction effluent, the leaching of Ni being higher. The initial pH significantly affected both activity and selectivity of the bimetallic catalysts, the maximum activity being achieved within the 6−7 range, which also led to the lowest Cu leaching. The use of a two-step reaction system was checked using two different catalysts, a bimetallic Pd−Cu in the first and a monometallic Pd catalyst in the second. With this two-step system, an important reduction of the nitrite originating in the first stage was observed, and the formation of N2 at the expense of ammonium was favored. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100838r [article] Denitrification of water with activated carbon-supported metallic catalysts [texte imprimé] / Luisa Calvo, Auteur ; Miguel A. Gilarranz, Auteur ; José A. Casas, Auteur . - 2010 . - pp. 5603–5609. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 12 (Juin 2010) . - pp. 5603–5609 Mots-clés : Nitrates  Catalytic  reduction  Trickle  bed  reactor Résumé : The catalytic reduction of nitrates with hydrogen in aqueous phase was studied in a trickle bed reactor using different activated carbon-supported metallic catalysts. Continuous experiments were performed at ambient conditions (25 °C and 1 atm) at different space-time values in the range of 25.8−103.3 kgcat h/mol. The activity of monometallic catalysts based on Pd, Rh, Cu, and Ni was low in all the cases, yielding nitrate conversions below 15%. The introduction of a second metal produced a synergistic effect, improving the catalytic activity and the selectivity toward N2. That increase in activity was more pronounced when using Pd or Rh combined with Cu, reaching nitrate conversions above 80% in the case of Pd−Cu catalysts. The catalyst with a Pd/Cu mass ratio of 2:1 (Pd050Cu025) also showed the lowest selectivity to nitrite and the highest to N2. Metal leaching was always below detection limits for Pd and Rh, whereas in the case of Cu and Ni, significant metal concentrations were found in the reaction effluent, the leaching of Ni being higher. The initial pH significantly affected both activity and selectivity of the bimetallic catalysts, the maximum activity being achieved within the 6−7 range, which also led to the lowest Cu leaching. The use of a two-step reaction system was checked using two different catalysts, a bimetallic Pd−Cu in the first and a monometallic Pd catalyst in the second. With this two-step system, an important reduction of the nitrite originating in the first stage was observed, and the formation of N2 at the expense of ammonium was favored. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100838r

Kinetics of the hydrodechlorination of 4-chlorophenol in water using Pd, Pt, and Rh/Al2O3 catalysts / Elena Díaz in Industrial & engineering chemistry research, Vol. 47 n°11 (Juin 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3840–3846 Titre : Kinetics of the hydrodechlorination of 4-chlorophenol in water using Pd, Pt, and Rh/Al2O3 catalysts Type de document : texte imprimé Auteurs : Elena Díaz, Auteur ; José A. Casas, Auteur ; Ángel F. Mohedano, Auteur ; Luisa Calvo, Auteur Année de publication : 2008 Article en page(s) : p. 3840–3846 Note générale : Bibliogr. p. 3845-3846 Langues : Anglais (eng) Mots-clés : 4-chlorophenol;  Hydrodechlorination;  Tank  reactor;  Catalytic  activity Résumé : The hydrodechlorination of 4-chlorophenol in an aqueous phase was studied in a semicontinuous basket stirred tank reactor using Pd, Pt, and Rh on γ-alumina commercial catalysts (0.5% w/w) under mild reaction conditions. The catalytic activity was studied in the temperature range of 20−40 °C. Pd and Rh showed a higher catalytic activity than Pt. From consumption of 4-chlorophenol and evolution of the reaction products, phenol, cyclohexanone, and cyclohexanol, a reaction scheme based on a parallel-series pathway and a kinetic model based on pseudo-first-order dependence on 4-chlorophenol have been proposed. Hydrodechlorination of 4-chlorophenol to phenol exhibits the largest apparent kinetic constant for Pd (k1 = 0.42–0.73 h−1) and Pt (k1 = 0.20–0.42 h−1) catalysts, while in the case of Rh, the three reactions, hydrodechlorination of 4-chlorophenol to phenol (k1 = 0.43–0.64 h−1) and hydrogenation of phenol to cyclohexanone (k3 = 0.42–0.78 h−1) and to cyclohexanol (k4 = 0.38–0.65 h−1), have comparable values of the kinetic constant. The apparent activation energy for 4-chlorophenol disappearance was determined, and values of 21.0, 26.2, and 15.3 kJ/mol were obtained for Pd, Pt, and Rh, respectively. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071517n [article] Kinetics of the hydrodechlorination of 4-chlorophenol in water using Pd, Pt, and Rh/Al2O3 catalysts [texte imprimé] / Elena Díaz, Auteur ; José A. Casas, Auteur ; Ángel F. Mohedano, Auteur ; Luisa Calvo, Auteur . - 2008 . - p. 3840–3846. Bibliogr. p. 3845-3846 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 n°11 (Juin 2008) . - p. 3840–3846 Mots-clés : 4-chlorophenol;  Hydrodechlorination;  Tank  reactor;  Catalytic  activity Résumé : The hydrodechlorination of 4-chlorophenol in an aqueous phase was studied in a semicontinuous basket stirred tank reactor using Pd, Pt, and Rh on γ-alumina commercial catalysts (0.5% w/w) under mild reaction conditions. The catalytic activity was studied in the temperature range of 20−40 °C. Pd and Rh showed a higher catalytic activity than Pt. From consumption of 4-chlorophenol and evolution of the reaction products, phenol, cyclohexanone, and cyclohexanol, a reaction scheme based on a parallel-series pathway and a kinetic model based on pseudo-first-order dependence on 4-chlorophenol have been proposed. Hydrodechlorination of 4-chlorophenol to phenol exhibits the largest apparent kinetic constant for Pd (k1 = 0.42–0.73 h−1) and Pt (k1 = 0.20–0.42 h−1) catalysts, while in the case of Rh, the three reactions, hydrodechlorination of 4-chlorophenol to phenol (k1 = 0.43–0.64 h−1) and hydrogenation of phenol to cyclohexanone (k3 = 0.42–0.78 h−1) and to cyclohexanol (k4 = 0.38–0.65 h−1), have comparable values of the kinetic constant. The apparent activation energy for 4-chlorophenol disappearance was determined, and values of 21.0, 26.2, and 15.3 kJ/mol were obtained for Pd, Pt, and Rh, respectively. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071517n