Miguel A.G. Hevia
University of Oviedo
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Featured researches published by Miguel A.G. Hevia.
Nature Chemistry | 2012
Detre Teschner; Gerard Novell-Leruth; Ramzi Farra; Axel Knop-Gericke; Robert Schlögl; L. Szentmiklósi; Miguel A.G. Hevia; Hary Soerijanto; Reinhard Schomäcker; Javier Pérez-Ramírez; Núria López
In heterogeneous catalysis, rates with Arrhenius-like temperature dependence are ubiquitous. Compensation phenomena, which arise from the linear correlation between the apparent activation energy and the logarithm of the apparent pre-exponential factor, are also common. Here, we study the origin of compensation and find a similar dependence on the rate-limiting surface coverage term for each Arrhenius parameter. This result is derived from an experimental determination of the surface coverage of oxygen and chlorine species using temporal analysis of products and prompt gamma activation analysis during HCl oxidation to Cl(2) on a RuO(2) catalyst. It is also substantiated by theory. We find that compensation phenomena appear when the effect on the apparent activation energy caused by changes in surface coverage is balanced out by the entropic configuration contributions of the surface. This result sets a new paradigm in understanding the interplay of compensation effects with the kinetics of heterogeneously catalysed processes.
CrystEngComm | 2016
Jochen A.H. Dreyer; Suman Pokhrel; Johannes Birkenstock; Miguel A.G. Hevia; Marco Schowalter; A. Rosenauer; Atsushi Urakawa; Wey Yang Teoh; Lutz Mädler
δ-Bi2O3 is one of the best oxygen ion conductors known. However, due to its limited thermal stability and complicated synthesis techniques, its applications are limited. Here, the synthesis of stable nano-sized δ-Bi2O3 using versatile and rapid flame spray pyrolysis (FSP) combined with in situ Ti and/or Mn doping for an enhanced thermal stability is reported for the first time. Exceptionally low Bi replacing cation concentrations (8 at% Ti) were sufficient to obtain phase-pure δ-Bi2O3 which was attributed to the extraordinarily high temperature gradient during FSP. The required cation amount for δ-phase stabilization was even further reduced by introducing mixtures of Mn and Ti (2.5 at% Mn + 2.5 at% Ti). Rietveld analysis revealed that the δ-Bi2O3 structure is best represented by the Fmm space group containing two closely neighbored 8c and 32f Wyckoff positions. Depending on the amount of Mn/Ti cations, about 25% of the possible oxygen positions remain vacant, suggesting high bulk oxygen mobility. The enhanced oxygen mobility was confirmed by temperature programmed reduction (H2-TPR) with bulk reduction for δ-Bi2O3 in contrast to exclusive surface reduction for β-Bi2O3.
Catalysis Today | 2005
Pablo Marín; Miguel A.G. Hevia; Salvador Ordóñez; Fernando V. Díez
Catalysis Today | 2014
Benjamin Beck; Vinzenz Fleischer; Sebastian Arndt; Miguel A.G. Hevia; Atsushi Urakawa; Peter Hugo; Reinhard Schomäcker
Aiche Journal | 2005
Davide Fissore; Antonello Barresi; Giancarlo Baldi; Miguel A.G. Hevia; Salvador Ordóñez; Fernando V. Díez
Aiche Journal | 2005
Miguel A.G. Hevia; Salvador Ordóñez; Fernando V. Díez; Davide Fissore; Antonello Barresi
Chemical Engineering Journal | 2007
Miguel A.G. Hevia; Salvador Ordóñez; Fernando V. Díez
Aiche Journal | 2006
Miguel A.G. Hevia; Salvador Ordóñez; Fernando V. Díez
Chemical Engineering Journal | 2007
Miguel A.G. Hevia; Davide Fissore; Salvador Ordóñez; Fernando V. Díez; Antonello Barresi
Archive | 2003
Miguel A.G. Hevia; A. Vega; Salvador Ordóñez; Davide Fissore