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Parametric study of the CaO-Ca12Al14O33 synthesis with respect to high CO2 sorption capacity and stability on multicycle operation / Christina S. Martavaltzi 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. 9537–9543 Titre : Parametric study of the CaO-Ca12Al14O33 synthesis with respect to high CO2 sorption capacity and stability on multicycle operation Type de document : texte imprimé Auteurs : Christina S. Martavaltzi, Auteur ; Angeliki A. Lemonidou, Auteur Année de publication : 2009 Article en page(s) : p. 9537–9543 Note générale : Chemistry engineering Langues : Anglais (eng) Mots-clés : Parametric  study  CaO−Ca12Al14O33  CO2  Sorption  capacity Résumé : This study focuses on the effect of various parameters of the synthesis procedure of the CO2 sorbent—CaO−Ca12Al14O33 derived from calcium acetate—on the CO2 sorption ability and lifetime. The synthesis procedure consists of the calcination of the acetate CaO precursor (step 1), the precipitation of the CaO with aluminum nitrates (step 2), followed by calcination at 500 °C for nitrates removal (step 3) and the calcination at 900 °C for the synthesis of Ca12Al14O33 (step 4). It has been shown, by employing TGA, that the applied difference in the calcination conditions (900 °C/2 h, 850 °C/1 h, 750 °C/0.5 h,) for the decomposition of the CaO acetate precursor (step 1) is not adequate to affect the sorption fixation and stability results. On the other hand calcination history of the precipitate and the addition of water in between the two calcination steps (nitrates removal and Ca12Al14O33 synthesis reaction) are of high importance for ensuring sorption capacities higher than 6.5 mol CO2/kg of sorbent in the first cycle. SEM observations showed that the addition of water after calcination at 500 °C (step 3) accounts for the generation of the regular hexagonal crystalloids of Ca(OH)2 which transforms in a porous network during calcination at 900 °C. It was also demonstrated that the quantity of CO2 molecules retained increases with decreasing aging time of the precipitate as a result of higher surface area (smaller crystal size) of the as-synthesized samples. The sorbent with the lower binder content (CaO/Ca12Al14O33 = 85:15) showed the prospective higher capacity (45% weight increase) in the first cycle but also a fair stability on repetitive sorption−desorption cycles. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800882d [article] Parametric study of the CaO-Ca12Al14O33 synthesis with respect to high CO2 sorption capacity and stability on multicycle operation [texte imprimé] / Christina S. Martavaltzi, Auteur ; Angeliki A. Lemonidou, Auteur . - 2009 . - p. 9537–9543. Chemistry engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9537–9543 Mots-clés : Parametric  study  CaO−Ca12Al14O33  CO2  Sorption  capacity Résumé : This study focuses on the effect of various parameters of the synthesis procedure of the CO2 sorbent—CaO−Ca12Al14O33 derived from calcium acetate—on the CO2 sorption ability and lifetime. The synthesis procedure consists of the calcination of the acetate CaO precursor (step 1), the precipitation of the CaO with aluminum nitrates (step 2), followed by calcination at 500 °C for nitrates removal (step 3) and the calcination at 900 °C for the synthesis of Ca12Al14O33 (step 4). It has been shown, by employing TGA, that the applied difference in the calcination conditions (900 °C/2 h, 850 °C/1 h, 750 °C/0.5 h,) for the decomposition of the CaO acetate precursor (step 1) is not adequate to affect the sorption fixation and stability results. On the other hand calcination history of the precipitate and the addition of water in between the two calcination steps (nitrates removal and Ca12Al14O33 synthesis reaction) are of high importance for ensuring sorption capacities higher than 6.5 mol CO2/kg of sorbent in the first cycle. SEM observations showed that the addition of water after calcination at 500 °C (step 3) accounts for the generation of the regular hexagonal crystalloids of Ca(OH)2 which transforms in a porous network during calcination at 900 °C. It was also demonstrated that the quantity of CO2 molecules retained increases with decreasing aging time of the precipitate as a result of higher surface area (smaller crystal size) of the as-synthesized samples. The sorbent with the lower binder content (CaO/Ca12Al14O33 = 85:15) showed the prospective higher capacity (45% weight increase) in the first cycle but also a fair stability on repetitive sorption−desorption cycles. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800882d

Simulation of a membrane reactor for the catalytic oxidehydrogenation of ethane / María L. Rodriguez in Industrial & engineering chemistry research, Vol. 48 N°3 (Février 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N°3 (Février 2009) . - p. 1090–1095 Titre : Simulation of a membrane reactor for the catalytic oxidehydrogenation of ethane Type de document : texte imprimé Auteurs : María L. Rodriguez, Auteur ; Daniel E. Ardissone, Auteur ; Angeliki A. Lemonidou, Auteur ; Eleni Heracleous, Auteur Année de publication : 2009 Article en page(s) : p. 1090–1095 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Ethylene  Catalytic  Oxidehydrogenation  Reactor  catalytic Résumé : Industrial-scale ethylene production using a novel membrane multitubular reactor for the ethane oxidative dehydrogenation process over a Ni−Nb−O catalyst is proposed. A theoretical study was performed by means of a pseudohomogeneous model of the tube and shell sides. The feasibility and convenience of using this novel design, as well as the influence of the main operating variables on the reactor performance, were analyzed. The introduction of the membrane leads to lower oxygen partial pressures inside the catalyst tubes when compared with a conventional multitubular reactor. This leads to very good ethylene selectivities, good temperature control as a result of lower heat generation rates, and reasonable production rates. The reactor performance appears to be highly affected by the balance between the rate of oxygen consumption by the chemical reaction and its rate of permeation through the membrane. Under certain operating conditions leading to lower reaction rates, an undesired accumulation of oxygen inside the tubes is observed. A minimum amount of O2 injected at the tube mouth appears beneficial to overcoming this accumulation phenomenon. The membrane reactor shows a nonconventional inverse parametric sensitivity with respect to the inlet temperature. When the reactor is operated at conditions where the reaction is controlled by the permeation flow of O2 through the membrane, it is possible to reach high selectivities to ethylene, significant ethane conversions, and mild temperature profiles. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800564v [article] Simulation of a membrane reactor for the catalytic oxidehydrogenation of ethane [texte imprimé] / María L. Rodriguez, Auteur ; Daniel E. Ardissone, Auteur ; Angeliki A. Lemonidou, Auteur ; Eleni Heracleous, Auteur . - 2009 . - p. 1090–1095. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N°3 (Février 2009) . - p. 1090–1095 Mots-clés : Ethylene  Catalytic  Oxidehydrogenation  Reactor  catalytic Résumé : Industrial-scale ethylene production using a novel membrane multitubular reactor for the ethane oxidative dehydrogenation process over a Ni−Nb−O catalyst is proposed. A theoretical study was performed by means of a pseudohomogeneous model of the tube and shell sides. The feasibility and convenience of using this novel design, as well as the influence of the main operating variables on the reactor performance, were analyzed. The introduction of the membrane leads to lower oxygen partial pressures inside the catalyst tubes when compared with a conventional multitubular reactor. This leads to very good ethylene selectivities, good temperature control as a result of lower heat generation rates, and reasonable production rates. The reactor performance appears to be highly affected by the balance between the rate of oxygen consumption by the chemical reaction and its rate of permeation through the membrane. Under certain operating conditions leading to lower reaction rates, an undesired accumulation of oxygen inside the tubes is observed. A minimum amount of O2 injected at the tube mouth appears beneficial to overcoming this accumulation phenomenon. The membrane reactor shows a nonconventional inverse parametric sensitivity with respect to the inlet temperature. When the reactor is operated at conditions where the reaction is controlled by the permeation flow of O2 through the membrane, it is possible to reach high selectivities to ethylene, significant ethane conversions, and mild temperature profiles. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800564v