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Alexis T Bell - One of the best experts on this subject based on the ideXlab platform.
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selective oxidation and Oxidative Dehydrogenation of hydrocarbons on bismuth vanadium molybdenum oxide
Journal of Catalysis, 2015Co-Authors: Zheng Zhai, Xuan Wang, Rachel B Licht, Alexis T BellAbstract:Abstract A systematic investigation of the Oxidative Dehydrogenation of propane to propene and 1- and 2-butene to 1,3-butadiene, and the selective oxidation of isobutene to methacrolein was carried out over Bi1−x/3V1−xMoxO4 (x = 0–1) with the aim of defining the effects of catalyst and reactant composition on the reaction kinetics. This work has revealed that the reaction kinetics can differ significantly depending on the state of catalyst oxidation, which in turn depends on the catalyst composition and the reaction conditions. Under conditions where the catalyst is fully oxidized, the kinetics for the oxidation of propene to acrolein and isobutene to methacrolein, and the Oxidative Dehydrogenation of propane to propene, 1-butene and trans-2-butene to butadiene are very similar—first order in the partial pressure of the alkane or alkene and zero order in the partial pressure of oxygen. These observations, together with XANES and UV–Vis data, suggest that all these reactions proceed via a Mars van Krevelen mechanism involving oxygen atoms in the catalysts and that the rate-limiting step involves cleavage of the weakest C H bond in the reactant. Consistent with these findings, the apparent activation energy and pre-exponential factor for both Oxidative Dehydrogenation and selective oxidation correlate with the dissociation energy of the weakest C H bond in the reactant. As the reaction temperature is lowered, catalyst reoxidation can become rate-limiting, the transition to this regime depending on ease of catalyst reduction and effectiveness of the reacting hydrocarbons as a reducing agent. A third regime is observed for isobutene oxidation at lower temperatures, in which the catalyst is more severely reduced and oxidation now proceeds via reaction of molecular oxygen, rather than catalyst lattice oxygen, with the reactant.
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Oxidative Dehydrogenation of propane over v2o5 moo3 al2o3 and v2o5 cr2o3 al2o3 structural characterization and catalytic function
Journal of Physical Chemistry B, 2005Co-Authors: Shuwu Yang, Enrique Iglesia, Alexis T BellAbstract:The structure and catalytic properties of binary dispersed oxide structures prepared by sequential deposition of VOx and MoOx or VOx and CrOx on Al2O3 were examined using Raman and UV−visible spectroscopies, the dynamics of stoichiometric reduction in H2, and the Oxidative Dehydrogenation of propane. VOx domains on Al2O3 modified by an equivalent MoOx monolayer led to dispersed binary structures at all surface densities. MoOx layers led to higher reactivity for VOx domains present at low VOx surface densities by replacing V−O−Al structures with more reactive V−O−Mo species. At higher surface densities, V−O−V structures in prevalent polyvanadates were replaced with less reactive V−O−Mo, leading to lower reducibility and Oxidative Dehydrogenation rates. Raman, reduction, and UV−visible data indicate that polyvanadates predominant on Al2O3 convert to dispersed binary oxide structures when MoOx is deposited before or after VOx deposition; these structures are less reducible and show higher UV−visible absorpti...
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kinetic isotopic effects in Oxidative Dehydrogenation of propane on vanadium oxide catalysts
Journal of Catalysis, 2000Co-Authors: Enrique Iglesia, Alexis T Bell, Kaidong ChenAbstract:Abstract Kinetic isotopic effects (KIEs) for Oxidative Dehydrogenation of propane were measured on 10 wt% V 2 O 5 /ZrO 2 . Normal KIEs were obtained using CH 3 CH 2 CH 3 and CD 3 CD 2 CD 3 as reactants for primary Dehydrogenation (2.8) and combustion (1.9) of propane and for secondary combustion of propene (2.6), suggesting that in all cases C–H bond dissociation is a kinetically relevant step. CH 3 CH 2 CH 3 and CH 3 CD 2 CH 3 reactants led to normal KIEs for Dehydrogenation (2.7) and combustion (1.8) of propane, but to a very small KIE (1.1) for propene combustion. These results show that the methylene C–H bond is activated in the rate-determining steps for propane Dehydrogenation and combustion reactions. The rate-determining step in secondary propene combustion involves the allylic C–H bond. In each reaction, the weakest C–H bond in the reactant is cleaved in the initial C–H bond activation step. The measured propane Oxidative Dehydrogenation KIEs are in agreement with theoretical estimates using a sequence of elementary steps, reaction rate expression, and transition state theory. The much smaller KIE for propane Oxidative Dehydrogenation (2.8) than the maximum KIE (6) expected for propane thermal Dehydrogenation indicates the participation of lattice oxygen. The different KIE values for propane primary Dehydrogenation and combustion suggest that these two reactions involve different lattice oxygen sites.
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isotopic tracer and kinetic studies of Oxidative Dehydrogenation pathways on vanadium oxide catalysts
Journal of Catalysis, 1999Co-Authors: Kaidong Chen, Andrei Y Khodakov, Jun Yang, Alexis T Bell, Enrique IglesiaAbstract:Kinetic analysis and isotopic tracer studies were used to identify elementary steps and their reversibility in the Oxidative Dehydrogenation of propane on VOx/ZrO2 catalysts with VOx surface densities between 1.6 and 6 VOx/nm2. Competitive reactions of C3H6 and CH313CH2CH3 showed that CO forms via secondary combustion of propene intermediates. CO2 formed via this reaction and also via the direct combustion of propane. Reactions of 18O2/C3H8 mixtures on supported V216O5 led to the preferential initial appearance of lattice 16O atoms in all oxygen-containing products, as expected if lattice oxygens were required for the activation of C–H bonds. Isotopically mixed O2 species were not detected during reactions of C3H8–18O2–16O2 reactant mixtures. Therefore, dissociative O2 chemisorption steps are irreversible. Similarly, C3H8–C3D8–O2 reactants undergo Oxidative Dehydrogenation without forming C3H8−xDx mixed isotopomers, suggesting that C–H bond activation steps are also irreversible. Normal kinetic isotopic effects (kC–H/kC–D=2.5) were measured for primary Oxidative Dehydrogenation reactions. Kinetic isotope effects were slightly lower for propane and propene combustion steps (1.7 and 2.2, respectively). These data are consistent with kinetically relevant steps involving the dissociation of C–H bonds in propane and propene. C3H6–D2O and C3D6–H2O cross exchange reactions occur readily during reaction; therefore, OH recombination steps are reversible and nearly equilibrated. These isotopic tracer results are consistent with a Mars–van Krevelen redox mechanism involving two lattice oxygens in irreversible C–H bond activation steps. The resulting alkyl species desorb as propene and the remaining O–H group recombines with neighboring OH groups to form water and reduced V centers. These reduced V centers reoxidize by irreversible dissociative chemisorption of O2. The application of pseudo-steady-state and reversibility assumptions leads to a complex kinetic rate expression that describes accurately the observed water inhibition effects and the kinetic orders in propane and oxygen when surface oxygen and OH groups are assumed to be the most abundant surface intermediates.
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structure and catalytic properties of supported vanadium oxides support effects on Oxidative Dehydrogenation reactions
Journal of Catalysis, 1999Co-Authors: Andrei Y Khodakov, Alexis T Bell, Bryan Olthof, Enrique IglesiaAbstract:Abstract The effects of support (Al 2 O 3 , SiO 2 , HfO 2 , TiO 2 , and ZrO 2 ) on the structure and catalytic behavior of supported vanadia in the Oxidative Dehydrogenation of propane were examined over a wide range of vanadium surface densities (0.5–15.0 VO x /nm 2 ). X-ray diffraction and Raman and UV-visible spectra showed that vanadia exists as highly dispersed species at surface densities below 7 VO x /nm 2 on Al 2 O 3 , HfO 2 , TiO 2 , and ZrO 2 , but as large V 2 O 5 crystallites on SiO 2 . Surface structures evolve from isolated monovanadates to polyvanadate domains and V 2 O 5 crystallites as VO x surface density increases. Polyvanadates appear at lower surface densities on ZrO 2 and TiO 2 than on Al 2 O 3 and HfO 2 . UV-visible edge energies decrease as VO x domains grow with increasing VO x surface density on all supports. Initial propene selectivities increase with increasing VO x surface density, as monovanadate species and exposed support sites, which favor primary combustion pathways, decrease in concentration. Oxidative Dehydrogenation rates per V-atom reach a maximum on VO x domains of intermediate size, which provide a balance between the activity of surface VO x species and their accessibility to reactants. Interactions with supports determine the type of VO x structures present at a given surface density, but turnover rates do not depend on the identity of the support when differences in VO x structure are taken into account. Oxidative Dehydrogenation turnover rates are similar on polyvanadate species and on surface VO x sites on bulk V 2 O 5 . The relative rates of Oxidative Dehydrogenation to form propene and of secondary propene oxidation to CO x do not depend on the identity of the support or on VO x surface density or structure. Thus, it appears that these two reactions require similar VO x surface sites and that these sites are present at similar surface densities on polyvanadate domains and small V 2 O 5 clusters.
Enrique Iglesia - One of the best experts on this subject based on the ideXlab platform.
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Oxidative Dehydrogenation of propane over v2o5 moo3 al2o3 and v2o5 cr2o3 al2o3 structural characterization and catalytic function
Journal of Physical Chemistry B, 2005Co-Authors: Shuwu Yang, Enrique Iglesia, Alexis T BellAbstract:The structure and catalytic properties of binary dispersed oxide structures prepared by sequential deposition of VOx and MoOx or VOx and CrOx on Al2O3 were examined using Raman and UV−visible spectroscopies, the dynamics of stoichiometric reduction in H2, and the Oxidative Dehydrogenation of propane. VOx domains on Al2O3 modified by an equivalent MoOx monolayer led to dispersed binary structures at all surface densities. MoOx layers led to higher reactivity for VOx domains present at low VOx surface densities by replacing V−O−Al structures with more reactive V−O−Mo species. At higher surface densities, V−O−V structures in prevalent polyvanadates were replaced with less reactive V−O−Mo, leading to lower reducibility and Oxidative Dehydrogenation rates. Raman, reduction, and UV−visible data indicate that polyvanadates predominant on Al2O3 convert to dispersed binary oxide structures when MoOx is deposited before or after VOx deposition; these structures are less reducible and show higher UV−visible absorpti...
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kinetic isotopic effects in Oxidative Dehydrogenation of propane on vanadium oxide catalysts
Journal of Catalysis, 2000Co-Authors: Enrique Iglesia, Alexis T Bell, Kaidong ChenAbstract:Abstract Kinetic isotopic effects (KIEs) for Oxidative Dehydrogenation of propane were measured on 10 wt% V 2 O 5 /ZrO 2 . Normal KIEs were obtained using CH 3 CH 2 CH 3 and CD 3 CD 2 CD 3 as reactants for primary Dehydrogenation (2.8) and combustion (1.9) of propane and for secondary combustion of propene (2.6), suggesting that in all cases C–H bond dissociation is a kinetically relevant step. CH 3 CH 2 CH 3 and CH 3 CD 2 CH 3 reactants led to normal KIEs for Dehydrogenation (2.7) and combustion (1.8) of propane, but to a very small KIE (1.1) for propene combustion. These results show that the methylene C–H bond is activated in the rate-determining steps for propane Dehydrogenation and combustion reactions. The rate-determining step in secondary propene combustion involves the allylic C–H bond. In each reaction, the weakest C–H bond in the reactant is cleaved in the initial C–H bond activation step. The measured propane Oxidative Dehydrogenation KIEs are in agreement with theoretical estimates using a sequence of elementary steps, reaction rate expression, and transition state theory. The much smaller KIE for propane Oxidative Dehydrogenation (2.8) than the maximum KIE (6) expected for propane thermal Dehydrogenation indicates the participation of lattice oxygen. The different KIE values for propane primary Dehydrogenation and combustion suggest that these two reactions involve different lattice oxygen sites.
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kinetics and mechanism of Oxidative Dehydrogenation of propane on vanadium molybdenum and tungsten oxides
Journal of Physical Chemistry B, 2000Co-Authors: Kaidong Chen, And Alexis T Bell, Enrique IglesiaAbstract:The effect of cation identity on Oxidative Dehydrogenation (ODH) pathways was examined using two-dimensional VOx, MoOx, and WOx structures supported on ZrO2. The similar kinetic rate expressions obtained on MoOx and VOx catalysts confirmed that Oxidative Dehydrogenation of propane occurs via similar pathways, which involve rate-determining C−H bond activation steps using lattice oxygen atoms. The activation energies for propane Dehydrogenation and for propene combustion increase in the sequence VOx/ZrO2 < MoOx/ZrO2 < WOx/ZrO2; the corresponding reaction rates decrease in this sequence, suggesting that turnover rates reflect C−H bond cleavage activation energies, which are in turn influenced by the reducibility of these metal oxides. Propane ODH activation energies are higher than for propene combustion. This leads to an increase in maximum alkene yields and in the ratio of rate constants for propane ODH and propene combustion as temperature increases. This difference in activation energy (48−61 kJ/mol) be...
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isotopic tracer and kinetic studies of Oxidative Dehydrogenation pathways on vanadium oxide catalysts
Journal of Catalysis, 1999Co-Authors: Kaidong Chen, Andrei Y Khodakov, Jun Yang, Alexis T Bell, Enrique IglesiaAbstract:Kinetic analysis and isotopic tracer studies were used to identify elementary steps and their reversibility in the Oxidative Dehydrogenation of propane on VOx/ZrO2 catalysts with VOx surface densities between 1.6 and 6 VOx/nm2. Competitive reactions of C3H6 and CH313CH2CH3 showed that CO forms via secondary combustion of propene intermediates. CO2 formed via this reaction and also via the direct combustion of propane. Reactions of 18O2/C3H8 mixtures on supported V216O5 led to the preferential initial appearance of lattice 16O atoms in all oxygen-containing products, as expected if lattice oxygens were required for the activation of C–H bonds. Isotopically mixed O2 species were not detected during reactions of C3H8–18O2–16O2 reactant mixtures. Therefore, dissociative O2 chemisorption steps are irreversible. Similarly, C3H8–C3D8–O2 reactants undergo Oxidative Dehydrogenation without forming C3H8−xDx mixed isotopomers, suggesting that C–H bond activation steps are also irreversible. Normal kinetic isotopic effects (kC–H/kC–D=2.5) were measured for primary Oxidative Dehydrogenation reactions. Kinetic isotope effects were slightly lower for propane and propene combustion steps (1.7 and 2.2, respectively). These data are consistent with kinetically relevant steps involving the dissociation of C–H bonds in propane and propene. C3H6–D2O and C3D6–H2O cross exchange reactions occur readily during reaction; therefore, OH recombination steps are reversible and nearly equilibrated. These isotopic tracer results are consistent with a Mars–van Krevelen redox mechanism involving two lattice oxygens in irreversible C–H bond activation steps. The resulting alkyl species desorb as propene and the remaining O–H group recombines with neighboring OH groups to form water and reduced V centers. These reduced V centers reoxidize by irreversible dissociative chemisorption of O2. The application of pseudo-steady-state and reversibility assumptions leads to a complex kinetic rate expression that describes accurately the observed water inhibition effects and the kinetic orders in propane and oxygen when surface oxygen and OH groups are assumed to be the most abundant surface intermediates.
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structure and catalytic properties of supported vanadium oxides support effects on Oxidative Dehydrogenation reactions
Journal of Catalysis, 1999Co-Authors: Andrei Y Khodakov, Alexis T Bell, Bryan Olthof, Enrique IglesiaAbstract:Abstract The effects of support (Al 2 O 3 , SiO 2 , HfO 2 , TiO 2 , and ZrO 2 ) on the structure and catalytic behavior of supported vanadia in the Oxidative Dehydrogenation of propane were examined over a wide range of vanadium surface densities (0.5–15.0 VO x /nm 2 ). X-ray diffraction and Raman and UV-visible spectra showed that vanadia exists as highly dispersed species at surface densities below 7 VO x /nm 2 on Al 2 O 3 , HfO 2 , TiO 2 , and ZrO 2 , but as large V 2 O 5 crystallites on SiO 2 . Surface structures evolve from isolated monovanadates to polyvanadate domains and V 2 O 5 crystallites as VO x surface density increases. Polyvanadates appear at lower surface densities on ZrO 2 and TiO 2 than on Al 2 O 3 and HfO 2 . UV-visible edge energies decrease as VO x domains grow with increasing VO x surface density on all supports. Initial propene selectivities increase with increasing VO x surface density, as monovanadate species and exposed support sites, which favor primary combustion pathways, decrease in concentration. Oxidative Dehydrogenation rates per V-atom reach a maximum on VO x domains of intermediate size, which provide a balance between the activity of surface VO x species and their accessibility to reactants. Interactions with supports determine the type of VO x structures present at a given surface density, but turnover rates do not depend on the identity of the support when differences in VO x structure are taken into account. Oxidative Dehydrogenation turnover rates are similar on polyvanadate species and on surface VO x sites on bulk V 2 O 5 . The relative rates of Oxidative Dehydrogenation to form propene and of secondary propene oxidation to CO x do not depend on the identity of the support or on VO x surface density or structure. Thus, it appears that these two reactions require similar VO x surface sites and that these sites are present at similar surface densities on polyvanadate domains and small V 2 O 5 clusters.
Larry A. Curtiss - One of the best experts on this subject based on the ideXlab platform.
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Subnanometer cobalt oxide clusters as selective low temperature Oxidative Dehydrogenation catalysts
Nature Communications, 2019Co-Authors: Sungsik Lee, Sonke Seifert, Randall E. Winans, Robert Schlögl, Avik Halder, Glen A. Ferguson, Detre Teschner, Vasiliki Papaefthimiou, Jeffrey Greeley, Larry A. CurtissAbstract:The discovery of more efficient, economical, and selective catalysts for Oxidative Dehydrogenation is of immense economic importance. However, the temperatures required for this reaction are typically high, often exceeding 400 °C. Herein, we report the discovery of subnanometer sized cobalt oxide clusters for Oxidative Dehydrogenation of cyclohexane that are active at lower temperatures than reported catalysts, while they can also eliminate the combustion channel. These results found for the two cluster sizes suggest other subnanometer size (CoO)x clusters will also be active at low temperatures. The high activity of the cobalt clusters can be understood on the basis of density functional studies that reveal highly active under-coordinated cobalt atoms in the clusters and show that the oxidized nature of the clusters substantially decreases the binding energy of the cyclohexene species which desorb from the cluster at low temperature. Current Oxidative Dehydrogenation processes are based on petroleum cracking that is indirect, environmentally unfriendly, and energy intensive. Here, the authors discover that subnanometer sized cobalt oxide clusters are active for Oxidative Dehydrogenation of cyclohexane at lower temperatures than reported catalysts.
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Subnanometer cobalt oxide clusters as selective low temperature Oxidative Dehydrogenation catalysts
Nature Publishing Group, 2019Co-Authors: Sungsik Lee, Sonke Seifert, Randall E. Winans, Robert Schlögl, Avik Halder, Glen A. Ferguson, Detre Teschner, Vasiliki Papaefthimiou, Jeffrey Greeley, Larry A. CurtissAbstract:Current Oxidative Dehydrogenation processes are based on petroleum cracking that is indirect, environmentally unfriendly, and energy intensive. Here, the authors discover that subnanometer sized cobalt oxide clusters are active for Oxidative Dehydrogenation of cyclohexane at lower temperatures than reported catalysts
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subnanometre platinum clusters as highly active and selective catalysts for the Oxidative Dehydrogenation of propane
Nature Materials, 2009Co-Authors: Jeffrey Greeley, Larry A. Curtiss, Stefan Vajda, Michael J Pellin, Christopher L Marshall, Gregory A Ballentine, Jeffrey W Elam, Stephanie CatillonmucherieAbstract:Catalytic Oxidative Dehydrogenation of alkanes is limited by poor activity and/or selectivity. Efficient conversion of propane to propylene is now achieved using sub-nanometre Pt clusters stabilized on alumina supports. The clusters are shown to be substantially more active than conventional catalysts and are highly selective towards propylene formation. Small clusters are known to possess reactivity not observed in their bulk analogues, which can make them attractive for catalysis1,2,3,4,5,6. Their distinct catalytic properties are often hypothesized to result from the large fraction of under-coordinated surface atoms7,8,9. Here, we show that size-preselected Pt8−10 clusters stabilized on high-surface-area supports are 40–100 times more active for the Oxidative Dehydrogenation of propane than previously studied platinum and vanadia catalysts, while at the same time maintaining high selectivity towards formation of propylene over by-products. Quantum chemical calculations indicate that under-coordination of the Pt atoms in the clusters is responsible for the surprisingly high reactivity compared with extended surfaces. We anticipate that these results will form the basis for development of a new class of catalysts by providing a route to bond-specific chemistry, ranging from energy-efficient and environmentally friendly synthesis strategies to the replacement of petrochemical feedstocks by abundant small alkanes10,11.
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subnanometre platinum clusters as highly active nbsp and selective catalysts for the Oxidative Dehydrogenation of propane
Nature Materials, 2009Co-Authors: Jeffrey Greeley, Larry A. Curtiss, Stefan Vajda, Michael J Pellin, Christopher L Marshall, Gregory A Ballentine, Jeffrey W Elam, Stephanie CatillonmucherieAbstract:Catalytic Oxidative Dehydrogenation of alkanes is limited by poor activity and/or selectivity. Efficient conversion of propane to propylene is now achieved using sub-nanometre Pt clusters stabilized on alumina supports. The clusters are shown to be substantially more active than conventional catalysts and are highly selective towards propylene formation. Small clusters are known to possess reactivity not observed in their bulk analogues, which can make them attractive for catalysis1,2,3,4,5,6. Their distinct catalytic properties are often hypothesized to result from the large fraction of under-coordinated surface atoms7,8,9. Here, we show that size-preselected Pt8−10 clusters stabilized on high-surface-area supports are 40–100 times more active for the Oxidative Dehydrogenation of propane than previously studied platinum and vanadia catalysts, while at the same time maintaining high selectivity towards formation of propylene over by-products. Quantum chemical calculations indicate that under-coordination of the Pt atoms in the clusters is responsible for the surprisingly high reactivity compared with extended surfaces. We anticipate that these results will form the basis for development of a new class of catalysts by providing a route to bond-specific chemistry, ranging from energy-efficient and environmentally friendly synthesis strategies to the replacement of petrochemical feedstocks by abundant small alkanes10,11.
Jeffrey Greeley - One of the best experts on this subject based on the ideXlab platform.
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Subnanometer cobalt oxide clusters as selective low temperature Oxidative Dehydrogenation catalysts
Nature Communications, 2019Co-Authors: Sungsik Lee, Sonke Seifert, Randall E. Winans, Robert Schlögl, Avik Halder, Glen A. Ferguson, Detre Teschner, Vasiliki Papaefthimiou, Jeffrey Greeley, Larry A. CurtissAbstract:The discovery of more efficient, economical, and selective catalysts for Oxidative Dehydrogenation is of immense economic importance. However, the temperatures required for this reaction are typically high, often exceeding 400 °C. Herein, we report the discovery of subnanometer sized cobalt oxide clusters for Oxidative Dehydrogenation of cyclohexane that are active at lower temperatures than reported catalysts, while they can also eliminate the combustion channel. These results found for the two cluster sizes suggest other subnanometer size (CoO)x clusters will also be active at low temperatures. The high activity of the cobalt clusters can be understood on the basis of density functional studies that reveal highly active under-coordinated cobalt atoms in the clusters and show that the oxidized nature of the clusters substantially decreases the binding energy of the cyclohexene species which desorb from the cluster at low temperature. Current Oxidative Dehydrogenation processes are based on petroleum cracking that is indirect, environmentally unfriendly, and energy intensive. Here, the authors discover that subnanometer sized cobalt oxide clusters are active for Oxidative Dehydrogenation of cyclohexane at lower temperatures than reported catalysts.
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Subnanometer cobalt oxide clusters as selective low temperature Oxidative Dehydrogenation catalysts
Nature Publishing Group, 2019Co-Authors: Sungsik Lee, Sonke Seifert, Randall E. Winans, Robert Schlögl, Avik Halder, Glen A. Ferguson, Detre Teschner, Vasiliki Papaefthimiou, Jeffrey Greeley, Larry A. CurtissAbstract:Current Oxidative Dehydrogenation processes are based on petroleum cracking that is indirect, environmentally unfriendly, and energy intensive. Here, the authors discover that subnanometer sized cobalt oxide clusters are active for Oxidative Dehydrogenation of cyclohexane at lower temperatures than reported catalysts
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subnanometre platinum clusters as highly active and selective catalysts for the Oxidative Dehydrogenation of propane
Nature Materials, 2009Co-Authors: Jeffrey Greeley, Larry A. Curtiss, Stefan Vajda, Michael J Pellin, Christopher L Marshall, Gregory A Ballentine, Jeffrey W Elam, Stephanie CatillonmucherieAbstract:Catalytic Oxidative Dehydrogenation of alkanes is limited by poor activity and/or selectivity. Efficient conversion of propane to propylene is now achieved using sub-nanometre Pt clusters stabilized on alumina supports. The clusters are shown to be substantially more active than conventional catalysts and are highly selective towards propylene formation. Small clusters are known to possess reactivity not observed in their bulk analogues, which can make them attractive for catalysis1,2,3,4,5,6. Their distinct catalytic properties are often hypothesized to result from the large fraction of under-coordinated surface atoms7,8,9. Here, we show that size-preselected Pt8−10 clusters stabilized on high-surface-area supports are 40–100 times more active for the Oxidative Dehydrogenation of propane than previously studied platinum and vanadia catalysts, while at the same time maintaining high selectivity towards formation of propylene over by-products. Quantum chemical calculations indicate that under-coordination of the Pt atoms in the clusters is responsible for the surprisingly high reactivity compared with extended surfaces. We anticipate that these results will form the basis for development of a new class of catalysts by providing a route to bond-specific chemistry, ranging from energy-efficient and environmentally friendly synthesis strategies to the replacement of petrochemical feedstocks by abundant small alkanes10,11.
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subnanometre platinum clusters as highly active nbsp and selective catalysts for the Oxidative Dehydrogenation of propane
Nature Materials, 2009Co-Authors: Jeffrey Greeley, Larry A. Curtiss, Stefan Vajda, Michael J Pellin, Christopher L Marshall, Gregory A Ballentine, Jeffrey W Elam, Stephanie CatillonmucherieAbstract:Catalytic Oxidative Dehydrogenation of alkanes is limited by poor activity and/or selectivity. Efficient conversion of propane to propylene is now achieved using sub-nanometre Pt clusters stabilized on alumina supports. The clusters are shown to be substantially more active than conventional catalysts and are highly selective towards propylene formation. Small clusters are known to possess reactivity not observed in their bulk analogues, which can make them attractive for catalysis1,2,3,4,5,6. Their distinct catalytic properties are often hypothesized to result from the large fraction of under-coordinated surface atoms7,8,9. Here, we show that size-preselected Pt8−10 clusters stabilized on high-surface-area supports are 40–100 times more active for the Oxidative Dehydrogenation of propane than previously studied platinum and vanadia catalysts, while at the same time maintaining high selectivity towards formation of propylene over by-products. Quantum chemical calculations indicate that under-coordination of the Pt atoms in the clusters is responsible for the surprisingly high reactivity compared with extended surfaces. We anticipate that these results will form the basis for development of a new class of catalysts by providing a route to bond-specific chemistry, ranging from energy-efficient and environmentally friendly synthesis strategies to the replacement of petrochemical feedstocks by abundant small alkanes10,11.
Stefan Vajda - One of the best experts on this subject based on the ideXlab platform.
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subnanometre platinum clusters as highly active and selective catalysts for the Oxidative Dehydrogenation of propane
Nature Materials, 2009Co-Authors: Jeffrey Greeley, Larry A. Curtiss, Stefan Vajda, Michael J Pellin, Christopher L Marshall, Gregory A Ballentine, Jeffrey W Elam, Stephanie CatillonmucherieAbstract:Catalytic Oxidative Dehydrogenation of alkanes is limited by poor activity and/or selectivity. Efficient conversion of propane to propylene is now achieved using sub-nanometre Pt clusters stabilized on alumina supports. The clusters are shown to be substantially more active than conventional catalysts and are highly selective towards propylene formation. Small clusters are known to possess reactivity not observed in their bulk analogues, which can make them attractive for catalysis1,2,3,4,5,6. Their distinct catalytic properties are often hypothesized to result from the large fraction of under-coordinated surface atoms7,8,9. Here, we show that size-preselected Pt8−10 clusters stabilized on high-surface-area supports are 40–100 times more active for the Oxidative Dehydrogenation of propane than previously studied platinum and vanadia catalysts, while at the same time maintaining high selectivity towards formation of propylene over by-products. Quantum chemical calculations indicate that under-coordination of the Pt atoms in the clusters is responsible for the surprisingly high reactivity compared with extended surfaces. We anticipate that these results will form the basis for development of a new class of catalysts by providing a route to bond-specific chemistry, ranging from energy-efficient and environmentally friendly synthesis strategies to the replacement of petrochemical feedstocks by abundant small alkanes10,11.
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subnanometre platinum clusters as highly active nbsp and selective catalysts for the Oxidative Dehydrogenation of propane
Nature Materials, 2009Co-Authors: Jeffrey Greeley, Larry A. Curtiss, Stefan Vajda, Michael J Pellin, Christopher L Marshall, Gregory A Ballentine, Jeffrey W Elam, Stephanie CatillonmucherieAbstract:Catalytic Oxidative Dehydrogenation of alkanes is limited by poor activity and/or selectivity. Efficient conversion of propane to propylene is now achieved using sub-nanometre Pt clusters stabilized on alumina supports. The clusters are shown to be substantially more active than conventional catalysts and are highly selective towards propylene formation. Small clusters are known to possess reactivity not observed in their bulk analogues, which can make them attractive for catalysis1,2,3,4,5,6. Their distinct catalytic properties are often hypothesized to result from the large fraction of under-coordinated surface atoms7,8,9. Here, we show that size-preselected Pt8−10 clusters stabilized on high-surface-area supports are 40–100 times more active for the Oxidative Dehydrogenation of propane than previously studied platinum and vanadia catalysts, while at the same time maintaining high selectivity towards formation of propylene over by-products. Quantum chemical calculations indicate that under-coordination of the Pt atoms in the clusters is responsible for the surprisingly high reactivity compared with extended surfaces. We anticipate that these results will form the basis for development of a new class of catalysts by providing a route to bond-specific chemistry, ranging from energy-efficient and environmentally friendly synthesis strategies to the replacement of petrochemical feedstocks by abundant small alkanes10,11.
