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Dive into the research topics where Miguel A.G. Hevia is active.

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Featured researches published by Miguel A.G. Hevia.


Nature Chemistry | 2012

In situ surface coverage analysis of RuO2-catalysed HCl oxidation reveals the entropic origin of compensation in heterogeneous catalysis

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

Decrease of the required dopant concentration for δ-Bi2O3 crystal stabilization through thermal quenching during single-step flame spray pyrolysis

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

Combustion of methane lean mixtures in reverse flow reactors: Comparison between packed and structured catalyst beds

Pablo Marín; Miguel A.G. Hevia; Salvador Ordóñez; Fernando V. Díez


Catalysis Today | 2014

Oxidative coupling of methane—A complex surface/gas phase mechanism with strong impact on the reaction engineering

Benjamin Beck; Vinzenz Fleischer; Sebastian Arndt; Miguel A.G. Hevia; Atsushi Urakawa; Peter Hugo; Reinhard Schomäcker


Aiche Journal | 2005

Design and testing of small-scale unsteady-state afterburners and reactors

Davide Fissore; Antonello Barresi; Giancarlo Baldi; Miguel A.G. Hevia; Salvador Ordóñez; Fernando V. Díez


Aiche Journal | 2005

Design and testing of a control system for reverse‐flow catalytic afterburners

Miguel A.G. Hevia; Salvador Ordóñez; Fernando V. Díez; Davide Fissore; Antonello Barresi


Chemical Engineering Journal | 2007

Effect of the catalyst properties on the performance of a reverse flow reactor for methane combustion in lean mixtures

Miguel A.G. Hevia; Salvador Ordóñez; Fernando V. Díez


Aiche Journal | 2006

Effect of Wall Properties on the Behavior of Bench-Scale Reverse Flow Reactors

Miguel A.G. Hevia; Salvador Ordóñez; Fernando V. Díez


Chemical Engineering Journal | 2007

Combustion of medium concentration CH4-air mixtures in non-stationary reactors

Miguel A.G. Hevia; Davide Fissore; Salvador Ordóñez; Fernando V. Díez; Antonello Barresi


Archive | 2003

Catalytic combustion of methane lean mixtures in a reverse flow reactor

Miguel A.G. Hevia; A. Vega; Salvador Ordóñez; Davide Fissore

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Reinhard Schomäcker

Technical University of Berlin

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Jochen A.H. Dreyer

City University of Hong Kong

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Wey Yang Teoh

City University of Hong Kong

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