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Catalytic performance of rhodium-based catalysts for CO preferential oxidation in H2-rich gases / Camilla Karnfelt in Industrial & engineering chemistry research, Vol. 47 n°15 (Août 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 n°15 (Août 2008) . - p. 5304–5312 Titre : Catalytic performance of rhodium-based catalysts for CO preferential oxidation in H2-rich gases Type de document : texte imprimé Auteurs : Camilla Karnfelt, Auteur ; Stefania Specchia, Auteur ; Guido Saracco, Auteur Année de publication : 2008 Article en page(s) : p. 5304–5312 Note générale : Bibliogr. p. 5311-5312 Langues : Anglais (eng) Mots-clés : Rhodium-based  catalysts;  CO  preferential  oxidation;  Gas Résumé : CO preferential oxidation (CO-PROX) can lead to a reduction of the CO content in the hydrogen-rich gas derived from hydrocarbon re-forming down to at least 10 ppmv or below, so as to enable its direct feed to standard polymer electrolyte membrane fuel cells (PEM FCs). Rh-based catalysts supported on A zeolites (3A, 4A, and 5A), alumina, titania, and ceria were prepared and tested for potential application in CO-PROX operating over a temperature range compatible with PEM FCs (80−100 °C). Among the prepared catalysts, the 1% Rh-zeolite 3A catalyst, tested with a weight space velocity (WSV) of 0.66 N·L·min−1·gcat.−1, was found to be the most suitable one for the CO-PROX at low temperature: it reduced the inlet CO concentration below 10 ppmv within a temperature range of at least 80−120 °C without the appearance of undesirable side reactions. Tests at progressively lower O-to-CO feed ratio and the same WSV value were carried out for the sake of reducing H2 consumption and improving CO-PROX selectivity. For 1% Rh-3A zeolite the minimum λ value, ensuring a sufficiently wide temperature range of a nearly complete CO conversion at temperatures compatible with PEM FCs operation, was found to be equal to 3. Finally, to decrease the catalyst cost, the Rh load on the catalyst was tentatively reduced from 1 to 0.5%. A better distribution of the active element crystallites over the support surface was even obtained for this last catalyst. When operating at λ = 3 and at WSV = 0.66 N·L·min−1·gcat.−1, the 0.5% Rh-3A catalyst could effectively reduce the inlet CO concentration below 10 ppmv within a temperature range of 100−140 °C, without the appearance of undesired side reactions. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0713588 [article] Catalytic performance of rhodium-based catalysts for CO preferential oxidation in H2-rich gases [texte imprimé] / Camilla Karnfelt, Auteur ; Stefania Specchia, Auteur ; Guido Saracco, Auteur . - 2008 . - p. 5304–5312. Bibliogr. p. 5311-5312 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 n°15 (Août 2008) . - p. 5304–5312 Mots-clés : Rhodium-based  catalysts;  CO  preferential  oxidation;  Gas Résumé : CO preferential oxidation (CO-PROX) can lead to a reduction of the CO content in the hydrogen-rich gas derived from hydrocarbon re-forming down to at least 10 ppmv or below, so as to enable its direct feed to standard polymer electrolyte membrane fuel cells (PEM FCs). Rh-based catalysts supported on A zeolites (3A, 4A, and 5A), alumina, titania, and ceria were prepared and tested for potential application in CO-PROX operating over a temperature range compatible with PEM FCs (80−100 °C). Among the prepared catalysts, the 1% Rh-zeolite 3A catalyst, tested with a weight space velocity (WSV) of 0.66 N·L·min−1·gcat.−1, was found to be the most suitable one for the CO-PROX at low temperature: it reduced the inlet CO concentration below 10 ppmv within a temperature range of at least 80−120 °C without the appearance of undesirable side reactions. Tests at progressively lower O-to-CO feed ratio and the same WSV value were carried out for the sake of reducing H2 consumption and improving CO-PROX selectivity. For 1% Rh-3A zeolite the minimum λ value, ensuring a sufficiently wide temperature range of a nearly complete CO conversion at temperatures compatible with PEM FCs operation, was found to be equal to 3. Finally, to decrease the catalyst cost, the Rh load on the catalyst was tentatively reduced from 1 to 0.5%. A better distribution of the active element crystallites over the support surface was even obtained for this last catalyst. When operating at λ = 3 and at WSV = 0.66 N·L·min−1·gcat.−1, the 0.5% Rh-3A catalyst could effectively reduce the inlet CO concentration below 10 ppmv within a temperature range of 100−140 °C, without the appearance of undesired side reactions. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0713588

Kinetic studies on Pd / CexZr1 − xO2 catalyst for methane combustion / Stefania Specchia in Industrial & engineering chemistry research, Vol. 49 N° 21 (Novembre 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 11101-11111 Titre : Kinetic studies on Pd / CexZr1 − xO2 catalyst for methane combustion Type de document : texte imprimé Auteurs : Stefania Specchia, Auteur ; Fabio Conti, Auteur ; Vito Specchia, Auteur Année de publication : 2011 Article en page(s) : pp. 11101-11111 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Combustion  Catalyst  Kinetics Résumé : In recent years, catalytic combustion of CH4 has been extensively studied as an alternative option to conventional thermal combustion for the production of heat and energy in view of its capability to achieve effective combustion at much lower temperatures than in conventional oxidation processes, with high efficiency and reduced pollutants such as CO and NOx. In this paper a kinetic study on 2% Pd over CexZr1-xO2 catalyst is presented. The catalyst was prepared by solution combustion synthesis, fully characterized and tested for CH4 catalytic combustion. A kinetic study was carried out in a continuous recycle reactor, operated in differential conditions. Twelve different possible rate equations belonging to Eley-Rideal, Langmuir-Hinshelwood, and Mars van Krevelen models were fitted to the experimental data. The best fitting belonged to a Mars van Krevelen mechanism, considering the concentration of the molecular O2 adsorbed on a single active site, which successively dissociated creating an active site with atomic O2. The obtained kinetic parameters were inside the range reported in literature for similar catalysts (Eact,1 = 23.8 kJ mol―1; Eact,2 = 31.9 kJ mol 1; E*act,1 = 5.4 kJ mol―1). For comparison, to better assess the catalytic role of Pd in the CH4 combustion, also the kinetic parameters of the sole carrier, CexZr1-xO2, were calculated. The best rate equation for the carrier was based on a different Mars van Krevelen mechanism, a simpler one, involving the surface reaction between adsorbed molecular oxygen and methane from the gas phase (Eact,1 = 79.6 kJ mol―1, Eact,2 = 1 14.6 kJ mol―1). ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23448008 [article] Kinetic studies on Pd / CexZr1 − xO2 catalyst for methane combustion [texte imprimé] / Stefania Specchia, Auteur ; Fabio Conti, Auteur ; Vito Specchia, Auteur . - 2011 . - pp. 11101-11111. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 11101-11111 Mots-clés : Combustion  Catalyst  Kinetics Résumé : In recent years, catalytic combustion of CH4 has been extensively studied as an alternative option to conventional thermal combustion for the production of heat and energy in view of its capability to achieve effective combustion at much lower temperatures than in conventional oxidation processes, with high efficiency and reduced pollutants such as CO and NOx. In this paper a kinetic study on 2% Pd over CexZr1-xO2 catalyst is presented. The catalyst was prepared by solution combustion synthesis, fully characterized and tested for CH4 catalytic combustion. A kinetic study was carried out in a continuous recycle reactor, operated in differential conditions. Twelve different possible rate equations belonging to Eley-Rideal, Langmuir-Hinshelwood, and Mars van Krevelen models were fitted to the experimental data. The best fitting belonged to a Mars van Krevelen mechanism, considering the concentration of the molecular O2 adsorbed on a single active site, which successively dissociated creating an active site with atomic O2. The obtained kinetic parameters were inside the range reported in literature for similar catalysts (Eact,1 = 23.8 kJ mol―1; Eact,2 = 31.9 kJ mol 1; E*act,1 = 5.4 kJ mol―1). For comparison, to better assess the catalytic role of Pd in the CH4 combustion, also the kinetic parameters of the sole carrier, CexZr1-xO2, were calculated. The best rate equation for the carrier was based on a different Mars van Krevelen mechanism, a simpler one, involving the surface reaction between adsorbed molecular oxygen and methane from the gas phase (Eact,1 = 79.6 kJ mol―1, Eact,2 = 1 14.6 kJ mol―1). ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23448008

Modeling study on the performance of an integrated APU fed with hydrocarbon fuels / Stefania Specchia in Industrial & engineering chemistry research, Vol. 49 N° 15 (Août 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 15 (Août 2010) . - pp 6803–6809 Titre : Modeling study on the performance of an integrated APU fed with hydrocarbon fuels Type de document : texte imprimé Auteurs : Stefania Specchia, Auteur ; Vito Specchia, Auteur Année de publication : 2010 Article en page(s) : pp 6803–6809 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Hydrocarbon  fuels  Modeling. Résumé : The employment of H2 in fuel cell (FCs) technologies could ensure significant advantages in terms of efficiency and environmental impact, representing thus an important alternative to the conventional energy production systems. As far as the actual lack of infrastructure for H2 production, storage, and distribution is concerned, FCs fed with H2, produced by fossil fuel reforming to generate on-board vehicles at least auxiliary power, represent a valid and interesting alternative to overcome the actual unfavorable situation, waiting for further development of infrastructures. The present work deals with the analysis of a 5 kWe auxiliary power unit (APU) integrated with a fuel processor unit (FPU), based on oxidative steam reforming (OSR, with bleed air, BA) and related CO clean-up technologies, for the production of H2-rich fuel gas, which is fed to a PEM-FC stack. Using the results of a series of steady-state system simulations with Matlab/Simulink, the APU performance was analyzed in terms of FP and APU efficiency, specific power produced by the stack, and water balance, by considering different liquid hydrocarbon fuels (gasoline, light and heavy diesel) and compressed natural gas (CNG) as feed. A parametric sensitivity analysis concerning the effects of the variation of steam to carbon ratio (SCR) and the BA rate to OSR was also carried out. As the main obtained results, the APU performance in transforming the primary fuel in H2-rich gas was more efficient according to the higher H2 to carbon ratio HCR of the feedstock. In fact, the APU net efficiency decreased with the following order: methane (27.8%) > gasoline (27.0%) > light diesel (26.5%) > heavy diesel (26.0%). The parametric sensitivity analysis revealed that with small SCR decrease and bleed air rate increase it was possible to improve the APU performance. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901696j [article] Modeling study on the performance of an integrated APU fed with hydrocarbon fuels [texte imprimé] / Stefania Specchia, Auteur ; Vito Specchia, Auteur . - 2010 . - pp 6803–6809. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 15 (Août 2010) . - pp 6803–6809 Mots-clés : Hydrocarbon  fuels  Modeling. Résumé : The employment of H2 in fuel cell (FCs) technologies could ensure significant advantages in terms of efficiency and environmental impact, representing thus an important alternative to the conventional energy production systems. As far as the actual lack of infrastructure for H2 production, storage, and distribution is concerned, FCs fed with H2, produced by fossil fuel reforming to generate on-board vehicles at least auxiliary power, represent a valid and interesting alternative to overcome the actual unfavorable situation, waiting for further development of infrastructures. The present work deals with the analysis of a 5 kWe auxiliary power unit (APU) integrated with a fuel processor unit (FPU), based on oxidative steam reforming (OSR, with bleed air, BA) and related CO clean-up technologies, for the production of H2-rich fuel gas, which is fed to a PEM-FC stack. Using the results of a series of steady-state system simulations with Matlab/Simulink, the APU performance was analyzed in terms of FP and APU efficiency, specific power produced by the stack, and water balance, by considering different liquid hydrocarbon fuels (gasoline, light and heavy diesel) and compressed natural gas (CNG) as feed. A parametric sensitivity analysis concerning the effects of the variation of steam to carbon ratio (SCR) and the BA rate to OSR was also carried out. As the main obtained results, the APU performance in transforming the primary fuel in H2-rich gas was more efficient according to the higher H2 to carbon ratio HCR of the feedstock. In fact, the APU net efficiency decreased with the following order: methane (27.8%) > gasoline (27.0%) > light diesel (26.5%) > heavy diesel (26.0%). The parametric sensitivity analysis revealed that with small SCR decrease and bleed air rate increase it was possible to improve the APU performance. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901696j