Infrared spectroscopic evidence of adsorbed species during the oxidation of 2-propanol catalyzed by γ-Al2O3-supported gold: Role of gold as a hydrogen-subtractor

Martinez-Ramirez, Z.; Jimenez‐Lam, Sergio A.; Fierro-Gonzalez, Juan C.

doi:10.1016/j.molcata.2011.05.001

Cited by 20 publications

(4 citation statements)

References 44 publications

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“…As can be seen in Fig. S4, ‡ there is a very good agreement between experimental and calculated (see below) IR spectra, except for the peak centered at around 3500 cm −1 , assigned to H-bonding 33 not considered in the DFT calculation. The ratio of the intensity of the bands due to Si-OH absorption at 3400-3450 cm −1 and those assigned to Si-O-Si at 1100 cm −1 is smaller for the derivatized silica particles than for the bare ones.…”

Section: Resultssupporting

confidence: 54%

Triplet state of 4-methoxybenzyl alcohol chemisorbed on silica nanoparticles

Arce

Bertolotti

Oliveira

et al. 2012

Photochem Photobiol Sci

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The knowledge of photochemical kinetics in colloidal systems is important in understanding environmental photochemistry on dispersed solid surfaces. As model materials for the chemically sorbed organic compounds present in natural environments, modified silica nanoparticles (NPs) were obtained here by condensation of the silanol groups of fumed silica nanoparticles with 4-methoxybenzyl alcohol. These particles were characterized by different techniques. To evaluate their toxicity, the inhibition of the natural luminescence emission of the marine bacterium Vibrio fischeri in suspensions of the particles was measured. Laser flash-photolysis experiments (λ exc = 266 nm) performed with NP suspensions in acetonitrile-aqueous phosphate buffer mixtures showed the formation of the lowest triplet excited state of the chemisorbed organic groups (λ max = 390 nm). DFT calculations of the absorption spectrum of this radical support the assignment. From the calculated triplet energy, a thermodynamically favorable energy transfer from these triplet states to oxygen to yield singlet molecular oxygen is predicted. A value of 0.09 was measured for the quantum yield of singlet molecular oxygen generation by air-saturated suspensions of the nanoparticles in the mixture of solvents acetonitrile-aqueous phosphate buffer. The quantum yield of singlet molecular oxygen generation by the free 4-methoxybenzyl alcohol in the same solvent is 0.31. † Dedicated to Prof. Kurt Schaffner on the occasion of his 80th birthday. ‡ Electronic supplementary information (ESI) available: TEM images, 29 Si NMR in solid state of the modified nanoparticles. Percentage of luminescence inhibition vs. the concentration of benzyl alcohol. FTIR spectra of 4-methoxybenzyl alcohol experimental and simulated. Experimental IR wavenumbers for NP and 4-methoxybenzyl alcohol. See

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Section: Resultssupporting

confidence: 54%

Triplet state of 4-methoxybenzyl alcohol chemisorbed on silica nanoparticles

Arce

Bertolotti

Oliveira

et al. 2012

Photochem Photobiol Sci

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“…Como el grupo estudia la estructura de los catalizadores en condiciones de reacción, se pri- vilegia la investigación de reacciones modelo. Algunas de las reacciones que se han estudiado son la oxidación de monóxido de carbono [4], la deshidrogenación selectiva de alcoholes de bajo peso molecular (e.g., metanol, etanol, 2-propanol) [5][6][7][8], las carbonilaciones de metanol y dimetil éter [1,2], y la hidrogenación de dióxido de carbono [9], entre otras [10]. La elección de estas reacciones no obedece únicamente a la simplicidad de las moléculas que involucran, sino que además existen intereses tecnológicos y/o ambientales por desarrollar mejores catalizadores para llevarlas a cabo.…”

Section: Estudio De Reacciones Con Moléculas Simplesunclassified

“…Aunque existe prácticamente un consenso en la literatura sobre el hecho de que la oxidación de alcoholes ocurre por una ruta deshidrogenativa, en la que el paso determinante de la velocidad de reacción consiste en el rompimiento del enlace β(C-H) del alcohol, la naturaleza de los sitios superficiales que participan en la reacción y la identidad de los intermediarios son aún un misterio [15]. El Grupo de Catálisis Heterogénea del itc ha investigado las reacciones de oxidación y deshidrogenación de etanol y 2-propanol catalizadas por nanopartículas de oro soportadas en γ-Al 2 O 3 y TiO 2 [5][6][7][8]. Además, recientemente ha comenzado a estudiar la influencia de la morfología del soporte en la actividad de catalizadores de nanopartículas y complejos mononucleares de Pt soportados en TiO 2 y nanotubos de TiO 2 .…”

Section: Oxidación Y Deshidrogenación Selectiva De Alcoholes Y Aminasunclassified

Catálisis en el Instituto Tecnológico de Celaya

Fierro-González

2017

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RESUMEN:En este trabajo se presenta de manera general la investigación que lleva a cabo el Grupo de Catálisis Heterogénea del Departamento de Ingeniería Química del Instituto Tecnológico de Celaya (itc). Se describen brevemente algunos proyectos realizados recientemente y se hace énfasis en la aproximación que el grupo utiliza para avanzar hacia la comprensión del funcionamiento de catalizadores de metales soportados. Se discuten también las perspectivas del grupo y su intención de aprovechar las oportunidades de colaboración dentro y fuera del Departamento de Ingeniería Química del itc.ABSTRACT: This paper describes the research conducted by the Heterogeneous Catalysis Research group of the Department of Chemical Engineering at the Instituto Tecnológico de Celaya (itc). Recent examples of some research projects are discussed, with emphasis on the scientific approach that the group uses to advance on the understanding of supported metal catalysts. The outlook of the research group is also explained, including the opportunities to collaborate with other research groups.

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“…Supported gold catalysts have recently attracted attention because they are active for many industrially relevant chemical reactions and because their catalytic properties were unexpected, as gold is the most inert metal in its bulk form. Among the many reactions catalyzed by supported gold, the water–gas shift − and the oxidations of carbon monoxide − and alcohols − have been widely investigated. For these reactions, it has been observed that the catalysts are typically more active when the gold particles are dispersed on reducible metal oxides (e.g., Fe 2 O 3 , ,, TiO 2 , ,, CeO 2 , ,, La 2 O 3 , , etc …”

Section: Introductionmentioning

confidence: 99%

Influence of Supported Gold on the Dynamics of Reduction and Crystallization of Iron Oxides: A Dispersive X-ray Absorption Near Edge Structure Spectroscopy and X-ray Diffraction Study

et al. 2011

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Iron oxide-supported gold samples were characterized by X-ray absorption near edge structure (XANES) spectroscopy during treatments in flowing H 2 at increasing temperature. Spectra were recorded at the Au L III and Fe K edges to monitor the reduction of both metals and to determine the influence of gold on the reducibility of the support. The results show that reduction of Fe 3+ to Fe 2+ on the support occurs at lower temperatures in samples containing gold than on samples of the bare support, with the reduction temperature being dependent on the gold content. X-ray diffraction patterns characterizing samples after H 2 treatments at various temperatures complement the XANES data and indicate that the presence of gold favors the crystallization of the support to give Fe 3 O 4 . Our data emphasize the power of XANES spectroscopy in following changes in the oxidation states of both gold and iron and suggest that the role that gold might have in promoting the reduction and crystallization of iron oxide support is to provide sites for hydrogen dissociation. Hydrogen moieties might spillover from the gold nanoparticles to the support, promoting its reduction and ensuing structural changes. ' INTRODUCTIONSupported gold catalysts have recently attracted attention because they are active for many industrially relevant chemical reactions and because their catalytic properties were unexpected, as gold is the most inert metal in its bulk form. Among the many reactions catalyzed by supported gold, the waterÀgas shift 1À3 and the oxidations of carbon monoxide 4À6 and alcohols 7À9 have been widely investigated. For these reactions, it has been observed that the catalysts are typically more active when the gold particles are dispersed on reducible metal oxides (e.g., Fe 2 O 3 , 4,10,11 TiO 2 , 5,12,13 CeO 2 , 1,2,14 La 2 O 3 , 5,15 etc. 16 ) than when they are on nonreducible metal oxides (e.g., γ-Al 2 O 3 , 6 MgO, 17 SiO 2 , 18 etc. 16 ). This observation has led some authors 19À21 to conclude that the interaction between the gold and the support is important in determining the activity of the catalysts, with the existence of a synergistic effect between the gold and reducible metal oxides at the gold-support interface. It has been hypothesized that such effect might involve redox processes, in which the gold particles favor the reduction of the metal oxide, thus allowing lattice oxygen atoms from the support to become activated species available for the oxidation reactions. 19À21

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Infrared spectroscopic evidence of adsorbed species during the oxidation of 2-propanol catalyzed by γ-Al2O3-supported gold: Role of gold as a hydrogen-subtractor

Cited by 20 publications

References 44 publications

Triplet state of 4-methoxybenzyl alcohol chemisorbed on silica nanoparticles

Triplet state of 4-methoxybenzyl alcohol chemisorbed on silica nanoparticles

Catálisis en el Instituto Tecnológico de Celaya

Influence of Supported Gold on the Dynamics of Reduction and Crystallization of Iron Oxides: A Dispersive X-ray Absorption Near Edge Structure Spectroscopy and X-ray Diffraction Study

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