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On the Nature of Formate Species in the Decomposition and Reaction of Methanol over Cerium Oxide Surfaces: A Combined Infrared Spectroscopy and Density Functional Theory Study

Pablo Lustemberg
20 Jul., 10:30h - 20 Jul., 11:30h de 2015
Ceria-based materials are widely used in the field heterogeneous catalysis as support or promoter to improve the activity, selectivity and/or stability of the catalysts. This is because the ability of ceria to rapidly change between Ce4+ and Ce3+ oxidation states as the environment changes from oxidizing to reducing and vice versa. The active role of ceria in the water-gas-shift (WGS, CO +H2O →CO2 + H2) and the steam reforming of methanol (SRM, CH3OH+H2O → O2+3H2) reactions for hydrogen production has been widely reported. Some of the various mechanisms proposed so far for these reactions involve formate (HCOO) transient species, and it has been argued that they might be playing an active or spectator roles as intermediates.
 The possibility of elucidating the mechanism of catalytic reactions, which is essential for rational catalyst design, depends very much on the chances of isolating intermediates in the study of each step in the catalytic cycle. In particular, IR spectroscopy has been used to discriminate various kinds of molecularly bonded surface formate species [1]. The assignment of particular features in IR spectra to a chemisorbed species is in general not trivial. Strong bonding to the surface significantly affects the vibrational frequencies, and the different ways in which species may anchor to the surface result in complex IR spectra. Creating and evaluating experimental and theoretical model catalysts that mimic the real ones in their complexity is expected to aid towards the fundamental understanding.
 In the present work, the structure, stability and vibrational properties of various types of formate species on a model CeO2(111) surface in equilibrium with a realistic environment containing CH3OH , H2O and H2, using DFT+U and statistical thermodynamics is investigated. We combine this analysis with transmission infrared spectroscopy during the temperature-programmed decomposition and reaction of CH3OH on a real CeO2 support. In doing this we are able to explain the nature of the observed formate species and, as will be shown, hydroxyl groups are found to be crucial for their stabilization.
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Polímeros de coordinación porosos (MOFs): de la síntesis a las aplicaciones

Patricia Horcajada
2 Jul., 10:30h - 2 Jul., 11:30h de 2015
Los polímeros de coordinación cristalinos o MOFs (por Metal-Organic Frameworks), formados por la unión de unidades inorgánicas (clusters, cadenas, planos, etc.) y ligandos orgánicos policomplejantes (carboxilatos, fosfonatos, catecolatos, etc.), combinan una gran versatilidad estructural y composicional, fácilmente modificable, con una elevada porosidad (hasta 6000 m2.g-1 y 2 cm3.g-1). Además, algunos de estos materiales exhiben una estructura porosa flexible, capaz de modificar reversiblemente su estructura tras la aplicación de diversos estímulos, resultando en una adsorción muy selectiva.
Estos sólidos presentan un gran interés industrial y social gracias a su aplicación potencial en campos estratégicos de gran actualidad como son el almacenamiento de gases, separación selectiva de fluidos, sensores, catálisis o biomedicina, entre otros.
 
Este seminario presentará una visión general de algunas de las estructuras de tipo MOF más prometedoras desarrolladas en el Institut Lavoisier de Versailles, así como su potencial aplicación en varios campos, incluyendo la separación, catálisis y biomedicina.
seminarioSee event

A multi-copper oxidase as engine in chemo-enzymatic catalysts

Thierry Tron
2 Jun., 12:00h - 2 Jun., 12:00h de 2015
seminarioSee event

TESIS DOCTORAL: "Metagenómica aplicada a estudios estructura-función en comunidades microbianas de diferentes sistemas acuáticos"

María Alcaide López
24 Apr., 12:00h - 24 Apr., 14:00h de 2015
Dirigida por Manuel Ferrer  Martínez
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TESIS DOCTORAL: "Hidrólisis Ácida de Celulosa y Biomasa Lignocelulósica Asistida con Líquidos Iónicos"

Silvia Morales de la Rosa
23 Apr., 12:00h - 23 Apr., 14:00h de 2015
Director: Jose Miguel Campos Martín

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Enabling the Next‐Generation of Advanced Biofuels: The Joint BioEnergy Institute

Seema Singh
27 Jan., 12:00h - 27 Jan., 13:00h de 2015

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