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Calorimetric and microscopic studies on the noncatalytic hydrothermolysis of ammonia borane / Junshe Zhang in Industrial & engineering chemistry research, Vol. 50 N° 18 (Septembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 18 (Septembre 2011) . - pp. 10407–10413 Titre : Calorimetric and microscopic studies on the noncatalytic hydrothermolysis of ammonia borane Type de document : texte imprimé Auteurs : Junshe Zhang, Auteur ; Yu Zhao, Auteur ; Daniel L. Akins, Auteur Année de publication : 2011 Article en page(s) : pp. 10407–10413 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Calorimetric  Microscopic  Hydrothermolysis Résumé : The hydrothermolysis of ammonia borane (AB) can release more hydrogen than AB thermolysis itself at mild temperatures. To obtain more insight into the noncatalytic hydrothermolysis, we investigated this process using a high-pressure differential scanning calorimeter and characterized the condensed residue by thermal analysis and infrared spectroscopy. For mass ratios of AB to water of 3.6, 1.44, and 0.72, the first pyrolysis step is not completed in 1 h at 85 °C. As the temperature increases from 25 to 115 at 1 °C min–1, there exist two exothermic peaks for the mass ratio of 3.6, centered around 82 and 103 °C on the heat flow curve, attributed to the hydrolysis and the first step of AB pyrolysis, respectively. For the mass ratio of 1.44, the top temperatures of these two exothermic peaks are 90 and 100 °C, respectively. However, for the mass ratio of 0.72, only the exothermic peak related to hydrolysis is observed, and its top temperature is ca. 106 °C. At temperatures up to 115 °C, the structural features associated with the product of the second pyrolysis step are absent for the mass ratios of 1.44 and 3.6. In the noncatalytic hydrothermolysis, the hydrolysis occurs much faster than the pyrolysis, and the latter is accelerated by both the heat desorbed from the hydrolysis and its product. Our findings suggest that water prefers reacting with AB rather than binding to the hydrolysis product to form hydrates and the hydrolysis itself can generate about 9 wt % of hydrogen with respect to the total mass of AB and water if sufficient AB is present. In this case, the heat of hydrolysis is 131 kJ (mol of AB)−1, and the solid hydrolysis product decomposes at temperatures about 350 °C. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie200878u [article] Calorimetric and microscopic studies on the noncatalytic hydrothermolysis of ammonia borane [texte imprimé] / Junshe Zhang, Auteur ; Yu Zhao, Auteur ; Daniel L. Akins, Auteur . - 2011 . - pp. 10407–10413. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 18 (Septembre 2011) . - pp. 10407–10413 Mots-clés : Calorimetric  Microscopic  Hydrothermolysis Résumé : The hydrothermolysis of ammonia borane (AB) can release more hydrogen than AB thermolysis itself at mild temperatures. To obtain more insight into the noncatalytic hydrothermolysis, we investigated this process using a high-pressure differential scanning calorimeter and characterized the condensed residue by thermal analysis and infrared spectroscopy. For mass ratios of AB to water of 3.6, 1.44, and 0.72, the first pyrolysis step is not completed in 1 h at 85 °C. As the temperature increases from 25 to 115 at 1 °C min–1, there exist two exothermic peaks for the mass ratio of 3.6, centered around 82 and 103 °C on the heat flow curve, attributed to the hydrolysis and the first step of AB pyrolysis, respectively. For the mass ratio of 1.44, the top temperatures of these two exothermic peaks are 90 and 100 °C, respectively. However, for the mass ratio of 0.72, only the exothermic peak related to hydrolysis is observed, and its top temperature is ca. 106 °C. At temperatures up to 115 °C, the structural features associated with the product of the second pyrolysis step are absent for the mass ratios of 1.44 and 3.6. In the noncatalytic hydrothermolysis, the hydrolysis occurs much faster than the pyrolysis, and the latter is accelerated by both the heat desorbed from the hydrolysis and its product. Our findings suggest that water prefers reacting with AB rather than binding to the hydrolysis product to form hydrates and the hydrolysis itself can generate about 9 wt % of hydrogen with respect to the total mass of AB and water if sufficient AB is present. In this case, the heat of hydrolysis is 131 kJ (mol of AB)−1, and the solid hydrolysis product decomposes at temperatures about 350 °C. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie200878u

Effect of composition on dehydrogenation of mesoporous silica/ammonia borane nanocomposites / Yu Zhao in Industrial & engineering chemistry research, Vol. 50 N° 17 (Septembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 17 (Septembre 2011) . - pp. 10024-10028 Titre : Effect of composition on dehydrogenation of mesoporous silica/ammonia borane nanocomposites Type de document : texte imprimé Auteurs : Yu Zhao, Auteur ; Junshe Zhang, Auteur ; Daniel L. Akins, Auteur Année de publication : 2011 Article en page(s) : pp. 10024-10028 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Nanocomposite  Dehydrogenation Résumé : This paper discusses the dehydrogenation of ammonia borane (AB) and MCM-41/AB nanocomposites in which the loading level of AB (i.e., the mass ratio of AB to mesoporous silica) varies from 0.11 to 2.36. The dehydrogenation temperatures shift to low temperatures with decreasing loading levels. At loading levels of 0.11 and 0.15, only one dehydrogenation step is observed at temperatures less than 200 °C. Our results also show that 12.6 wt % of hydrogen in the incorporated AB is liberated from the nanocomposite at a loading level of 0.15 in 1 h at 89.5 °C. We deduce that AB confined within the mesopores is amorphous, while AB outside of the channels has a tetragonal structure. Furthermore, we deduce that at relative low loading levels AB coats the inner surface of mesoporous silica as a monolayer. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24483646 [article] Effect of composition on dehydrogenation of mesoporous silica/ammonia borane nanocomposites [texte imprimé] / Yu Zhao, Auteur ; Junshe Zhang, Auteur ; Daniel L. Akins, Auteur . - 2011 . - pp. 10024-10028. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 17 (Septembre 2011) . - pp. 10024-10028 Mots-clés : Nanocomposite  Dehydrogenation Résumé : This paper discusses the dehydrogenation of ammonia borane (AB) and MCM-41/AB nanocomposites in which the loading level of AB (i.e., the mass ratio of AB to mesoporous silica) varies from 0.11 to 2.36. The dehydrogenation temperatures shift to low temperatures with decreasing loading levels. At loading levels of 0.11 and 0.15, only one dehydrogenation step is observed at temperatures less than 200 °C. Our results also show that 12.6 wt % of hydrogen in the incorporated AB is liberated from the nanocomposite at a loading level of 0.15 in 1 h at 89.5 °C. We deduce that AB confined within the mesopores is amorphous, while AB outside of the channels has a tetragonal structure. Furthermore, we deduce that at relative low loading levels AB coats the inner surface of mesoporous silica as a monolayer. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24483646

Enhanced kinetics of CO2 hydrate formation under static conditions / Junshe Zhang in Industrial & engineering chemistry research, Vol. 48 N° 13 (Juillet 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 13 (Juillet 2009) . - pp. 5934–5942 Titre : Enhanced kinetics of CO2 hydrate formation under static conditions Type de document : texte imprimé Auteurs : Junshe Zhang, Auteur ; Jae W. Lee, Auteur Année de publication : 2009 Article en page(s) : pp. 5934–5942 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : CO2  hydrate  formation  Cyclopentane  Nonstirred  batch  reactor Résumé : Trapping CO2 in hydrates is one of the new technologies for CO2 capture and storage. One of the primary obstacles to this option is the low formation rate. This work presents the rapid formation of CO2 hydrates with a small amount of cyclopentane (CP). The formation kinetics was investigated in a 474 cm3 nonstirred batch reactor with 100 and 200 cm3 of water. At volume ratios of CP to water between 0.01 and 0.1, the maximum growth rate is 0.32 mol h−1 at CO2 pressures ranging from 1.9 to 3.4 MPa and at 274 K. CO2 hydrates (sI) and CO2 + CP (sII) binary hydrates coexist at the end of hydrate growth. The mole ratio of CO2 entrapped in the sI hydrates to that in the sII binary hydrates is higher with 100 cm3 of water than with 200 cm3 of water. The same trend is also observed for the total amount of CO2 entrapped in the hydrate phase. The growth rate depends not only on the water volume but also on the pressure. The hydrate growth rate and the water conversion reach a maximum at 3.06 MPa and then decrease as the pressure increases from 1.9 to 3.4 MPa with 100 cm3 of water and 5 cm3 of CP. The water conversion to the hydrates reaches 52% within 2 h. This accelerated formation kinetics can provide a stepping-stone for developing a new hydrate-based CO2 capture and storage technique. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801170u [article] Enhanced kinetics of CO2 hydrate formation under static conditions [texte imprimé] / Junshe Zhang, Auteur ; Jae W. Lee, Auteur . - 2009 . - pp. 5934–5942. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 13 (Juillet 2009) . - pp. 5934–5942 Mots-clés : CO2  hydrate  formation  Cyclopentane  Nonstirred  batch  reactor Résumé : Trapping CO2 in hydrates is one of the new technologies for CO2 capture and storage. One of the primary obstacles to this option is the low formation rate. This work presents the rapid formation of CO2 hydrates with a small amount of cyclopentane (CP). The formation kinetics was investigated in a 474 cm3 nonstirred batch reactor with 100 and 200 cm3 of water. At volume ratios of CP to water between 0.01 and 0.1, the maximum growth rate is 0.32 mol h−1 at CO2 pressures ranging from 1.9 to 3.4 MPa and at 274 K. CO2 hydrates (sI) and CO2 + CP (sII) binary hydrates coexist at the end of hydrate growth. The mole ratio of CO2 entrapped in the sI hydrates to that in the sII binary hydrates is higher with 100 cm3 of water than with 200 cm3 of water. The same trend is also observed for the total amount of CO2 entrapped in the hydrate phase. The growth rate depends not only on the water volume but also on the pressure. The hydrate growth rate and the water conversion reach a maximum at 3.06 MPa and then decrease as the pressure increases from 1.9 to 3.4 MPa with 100 cm3 of water and 5 cm3 of CP. The water conversion to the hydrates reaches 52% within 2 h. This accelerated formation kinetics can provide a stepping-stone for developing a new hydrate-based CO2 capture and storage technique. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801170u

Inhibition effect of surfactants on CO2 enclathration with cyclopentane in an unstirred batch reactor / Junshe Zhang in Industrial & engineering chemistry research, Vol. 48 N° 10 (Mai 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 10 (Mai 2009) . - pp. 4703–4709 Titre : Inhibition effect of surfactants on CO2 enclathration with cyclopentane in an unstirred batch reactor Type de document : texte imprimé Auteurs : Junshe Zhang, Auteur ; Jae W. Lee, Auteur Année de publication : 2009 Article en page(s) : pp. 4703–4709 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Sodium  dodecyl  sulfate  Cetyl  trimethylammonium  bromide  Fatty  alcohol  EO/PO  CO2  absorption Résumé : The effect of sodium dodecyl sulfate (SDS), cetyl trimethylammonium bromide (CTAB), and fatty alcohol EO/PO derivative (LS54) on unsteady-state CO2 absorption in the metastable region of CO2 hydrates and CO2 enclathration with cyclopentane (CP) was investigated in an unstirred batch reactor. These surfactants have no measurable effect on the mass transfer of CO2 across the gas−liquid interface into water. However, they retard CO2 enclathration, and this inhibition effect becomes significant at 200 ppm of SDS and 100 ppm of LS54 or CTAB. A layer of clathrate hydrates is visually observed if charging CO2 and CP sequentially. Even though this layer cannot be macroscopically detected when swapping the order of CO2 and CP charge, the existence of this layer can be inferred from the unchanged pressure profile. This layer prevents CO2 from contacting with water and thus delays CO2 enclathration. The habit of clathrate hydrates growing along the reactor wall without agitation is discussed based on the magnitude of temperature spikes at the initial stage of the enclathration. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8019328 [article] Inhibition effect of surfactants on CO2 enclathration with cyclopentane in an unstirred batch reactor [texte imprimé] / Junshe Zhang, Auteur ; Jae W. Lee, Auteur . - 2009 . - pp. 4703–4709. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 10 (Mai 2009) . - pp. 4703–4709 Mots-clés : Sodium  dodecyl  sulfate  Cetyl  trimethylammonium  bromide  Fatty  alcohol  EO/PO  CO2  absorption Résumé : The effect of sodium dodecyl sulfate (SDS), cetyl trimethylammonium bromide (CTAB), and fatty alcohol EO/PO derivative (LS54) on unsteady-state CO2 absorption in the metastable region of CO2 hydrates and CO2 enclathration with cyclopentane (CP) was investigated in an unstirred batch reactor. These surfactants have no measurable effect on the mass transfer of CO2 across the gas−liquid interface into water. However, they retard CO2 enclathration, and this inhibition effect becomes significant at 200 ppm of SDS and 100 ppm of LS54 or CTAB. A layer of clathrate hydrates is visually observed if charging CO2 and CP sequentially. Even though this layer cannot be macroscopically detected when swapping the order of CO2 and CP charge, the existence of this layer can be inferred from the unchanged pressure profile. This layer prevents CO2 from contacting with water and thus delays CO2 enclathration. The habit of clathrate hydrates growing along the reactor wall without agitation is discussed based on the magnitude of temperature spikes at the initial stage of the enclathration. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8019328