Documents disponibles écrits par cet auteur

Hydroformylation of 1,4-diacetoxy-2-butene using HRh(CO)(PPh3)3 tethered on alumina as a catalyst / Rashmi Chansarkar in Industrial & engineering chemistry research, Vol. 48 N° 21 (Novembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9479–9489 Titre : Hydroformylation of 1,4-diacetoxy-2-butene using HRh(CO)(PPh3)3 tethered on alumina as a catalyst : kinetic study Type de document : texte imprimé Auteurs : Rashmi Chansarkar, Auteur ; Ashutosh A. Kelkar, Auteur ; Raghunath V. Chaudhari, Auteur Année de publication : 2010 Article en page(s) : pp. 9479–9489 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : 1,4-diacetoxy-2-butene  Kinetic  study Résumé : Hydroformylation of 1,4-diacetoxy-2-butene (DAB) was studied using [HRh(CO)(PPh3)3] complex catalyst tethered on alumina using phosphotungstic acid (PTA) as an anchoring agent, with the aim to understand the product distribution, selectivity, and intrinsic kinetics. It was observed that with the tethered heterogeneous catalyst a simultaneous hydroformylation followed by deacetoxylation steps was possible, which is relevant for combining two steps in the sequence of synthesis of vitamin-A intermediate [2-formyl-4-acetoxy butene (FAB)]. 31P cross-polarization magic angle spinning nuclear magnetic resonance (CP MAS NMR) and infrared (IR) instrumental techniques were found be the most effective techniques to establish the catalyst structure and true heterogeneity. On the basis of the spectroscopic evidence, we postulate the loss of a PPh3 group during tethering to give HRh(CO)(PPh3)2−PTA−Al2O3 as a heterogeneous complex catalyst. Experimental data on the concentration−time and CO/H2 consumption−time profiles were obtained and the effects of DAB concentration, CO partial pressure, H2 partial pressure, and catalyst loading were studied in a 50 mL stirred batch reactor over a temperature range of 338−358 K. The analysis of solid−liquid−gas mass transfer effects was investigated to ensure that the reaction was operating in the kinetic regime. Various models were developed, and the best model was chosen by a model discrimination procedure. The agreement between the model prediction and the experimental data was found to be excellent. The activation energies for the hydroformylation and deacetoxylation steps were found to be 42.5 and 80.2 kJ/mol. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900269z [article] Hydroformylation of 1,4-diacetoxy-2-butene using HRh(CO)(PPh3)3 tethered on alumina as a catalyst : kinetic study [texte imprimé] / Rashmi Chansarkar, Auteur ; Ashutosh A. Kelkar, Auteur ; Raghunath V. Chaudhari, Auteur . - 2010 . - pp. 9479–9489. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9479–9489 Mots-clés : 1,4-diacetoxy-2-butene  Kinetic  study Résumé : Hydroformylation of 1,4-diacetoxy-2-butene (DAB) was studied using [HRh(CO)(PPh3)3] complex catalyst tethered on alumina using phosphotungstic acid (PTA) as an anchoring agent, with the aim to understand the product distribution, selectivity, and intrinsic kinetics. It was observed that with the tethered heterogeneous catalyst a simultaneous hydroformylation followed by deacetoxylation steps was possible, which is relevant for combining two steps in the sequence of synthesis of vitamin-A intermediate [2-formyl-4-acetoxy butene (FAB)]. 31P cross-polarization magic angle spinning nuclear magnetic resonance (CP MAS NMR) and infrared (IR) instrumental techniques were found be the most effective techniques to establish the catalyst structure and true heterogeneity. On the basis of the spectroscopic evidence, we postulate the loss of a PPh3 group during tethering to give HRh(CO)(PPh3)2−PTA−Al2O3 as a heterogeneous complex catalyst. Experimental data on the concentration−time and CO/H2 consumption−time profiles were obtained and the effects of DAB concentration, CO partial pressure, H2 partial pressure, and catalyst loading were studied in a 50 mL stirred batch reactor over a temperature range of 338−358 K. The analysis of solid−liquid−gas mass transfer effects was investigated to ensure that the reaction was operating in the kinetic regime. Various models were developed, and the best model was chosen by a model discrimination procedure. The agreement between the model prediction and the experimental data was found to be excellent. The activation energies for the hydroformylation and deacetoxylation steps were found to be 42.5 and 80.2 kJ/mol. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900269z

Kinetic modeling of hydroxycarbonylation of styrene using a homogeneous palladium complex catalyst / Yuanchun Li in Industrial & engineering chemistry research, Vol. 50 N° 16 (Août 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 16 (Août 2011) . - pp. 9577-9586 Titre : Kinetic modeling of hydroxycarbonylation of styrene using a homogeneous palladium complex catalyst Type de document : texte imprimé Auteurs : Yuanchun Li, Auteur ; Raghunath V. Chaudhari, Auteur Année de publication : 2011 Article en page(s) : pp. 9577-9586 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Modeling  Catalyst  Kinetic  model Résumé : Kinetics of hydrorycarbonylation of styrene using Pd(pyca)(PPh3)(OTs)/PPh3/TsOH/LiCl catalyst was investigated in a stirred batch reactor. The effects of catalyst, styrene, and water concentrations and the partial pressure of CO on the rate of hydroxycarbonylation as well as the concentration—time profiles have been investigated over a temperature range of 368-388 K. A unique observation was the induction period which was CO pressure dependent leading to lower rates of carbonylation at the start of the reaction. A molecular level description of the reaction mechanism (catalytic cycle) has been proposed to explain the observed trends. The results were found to be consistent with a mechanism based on a Pd-hydride complex as an active intermediate species. The proposed mechanism also captured the experimentally observed trends of induction period. The approach of microkinetic modeling used here does not require the assumption of a rate determining step and provides a good description of the complex trends observed with respect to reaction parameters over a wide range of conditions. Note de contenu : http://acatalogue_2.biblio.intranet.enp.edu.dz/catalog.php?categ=serials&sub=analysis&action=analysis_form&bul_id=15578&analysis_id=0 DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24425200 [article] Kinetic modeling of hydroxycarbonylation of styrene using a homogeneous palladium complex catalyst [texte imprimé] / Yuanchun Li, Auteur ; Raghunath V. Chaudhari, Auteur . - 2011 . - pp. 9577-9586. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 16 (Août 2011) . - pp. 9577-9586 Mots-clés : Modeling  Catalyst  Kinetic  model Résumé : Kinetics of hydrorycarbonylation of styrene using Pd(pyca)(PPh3)(OTs)/PPh3/TsOH/LiCl catalyst was investigated in a stirred batch reactor. The effects of catalyst, styrene, and water concentrations and the partial pressure of CO on the rate of hydroxycarbonylation as well as the concentration—time profiles have been investigated over a temperature range of 368-388 K. A unique observation was the induction period which was CO pressure dependent leading to lower rates of carbonylation at the start of the reaction. A molecular level description of the reaction mechanism (catalytic cycle) has been proposed to explain the observed trends. The results were found to be consistent with a mechanism based on a Pd-hydride complex as an active intermediate species. The proposed mechanism also captured the experimentally observed trends of induction period. The approach of microkinetic modeling used here does not require the assumption of a rate determining step and provides a good description of the complex trends observed with respect to reaction parameters over a wide range of conditions. Note de contenu : http://acatalogue_2.biblio.intranet.enp.edu.dz/catalog.php?categ=serials&sub=analysis&action=analysis_form&bul_id=15578&analysis_id=0 DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24425200

Supercritical deoxygenation of a model bio - oil oxygenate / Jackson W. Ford 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. 10852–10858 Titre : Supercritical deoxygenation of a model bio - oil oxygenate Type de document : texte imprimé Auteurs : Jackson W. Ford, Auteur ; Raghunath V. Chaudhari, Auteur ; Bala Subramaniam, Auteur Année de publication : 2011 Article en page(s) : pp. 10852–10858 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Deoxygenation  Oil Résumé : A novel process for the fixed-bed deoxygenation of a model bio-oil compound in supercritical media at mild pressures (tens of bars) is presented. As an example, nonanal deoxygenation over Pt/Al2O3 catalyst in supercritical n-hexane (Tc = 234.45 °C, Pc = 30.2 bar) with excess hydrogen (molar H2/nonanol in feed = 57) at 300 °C provides steady conversions of approximately 60% over a pressure range of 7−80 bar with approximately 40% selectivity to C8 and C9 hydrocarbons, at liquid hourly space velocities of 80 g nonanal·(g Pt)−1·h−1. Further, the conversions display only a mild temperature dependence. This suggests that for the conditions under study, the reaction is limited by mass transfer of nonanal (limiting reactant) from the bulk fluid phase to the catalyst particle. Among the alkanes, the selectivity to the decarbonylation product (n-octane) is higher at all pressures relative to the hydrogention product (n-nonane). However, the selectivities toward nonane and nonanol increase relative to the decarbonylation product (n-octane) at higher reactor pressures, attributed to the enhanced hydrogen partial pressures at supercritical conditions. Effective rate constants, estimated from a simple isothermal packed-bed reactor model that assumes first-order dependence on nonanal concentration, decrease exponentially as the pressure is tuned from subcritical pressures (gaslike properties) to supercritical pressures (liquidlike properties). This decrease is characteristic of the pressure dependence of the external mass transfer coefficient. Mass transfer coefficients, predicted using published correlations, are of the same order of magnitude as the effective rate constants, further affirming that the measured reaction rates are controlled by external mass transfer. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie1005492 [article] Supercritical deoxygenation of a model bio - oil oxygenate [texte imprimé] / Jackson W. Ford, Auteur ; Raghunath V. Chaudhari, Auteur ; Bala Subramaniam, Auteur . - 2011 . - pp. 10852–10858. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 10852–10858 Mots-clés : Deoxygenation  Oil Résumé : A novel process for the fixed-bed deoxygenation of a model bio-oil compound in supercritical media at mild pressures (tens of bars) is presented. As an example, nonanal deoxygenation over Pt/Al2O3 catalyst in supercritical n-hexane (Tc = 234.45 °C, Pc = 30.2 bar) with excess hydrogen (molar H2/nonanol in feed = 57) at 300 °C provides steady conversions of approximately 60% over a pressure range of 7−80 bar with approximately 40% selectivity to C8 and C9 hydrocarbons, at liquid hourly space velocities of 80 g nonanal·(g Pt)−1·h−1. Further, the conversions display only a mild temperature dependence. This suggests that for the conditions under study, the reaction is limited by mass transfer of nonanal (limiting reactant) from the bulk fluid phase to the catalyst particle. Among the alkanes, the selectivity to the decarbonylation product (n-octane) is higher at all pressures relative to the hydrogention product (n-nonane). However, the selectivities toward nonane and nonanol increase relative to the decarbonylation product (n-octane) at higher reactor pressures, attributed to the enhanced hydrogen partial pressures at supercritical conditions. Effective rate constants, estimated from a simple isothermal packed-bed reactor model that assumes first-order dependence on nonanal concentration, decrease exponentially as the pressure is tuned from subcritical pressures (gaslike properties) to supercritical pressures (liquidlike properties). This decrease is characteristic of the pressure dependence of the external mass transfer coefficient. Mass transfer coefficients, predicted using published correlations, are of the same order of magnitude as the effective rate constants, further affirming that the measured reaction rates are controlled by external mass transfer. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie1005492