30/07/2012, by

The origin of compensation in heterogeneous catalysis

An international team of scientists from ICIQ (Spain), FHI (Germany) and ETH (Switzerland) solves the controversy about the origin of compensation in heterogeneous catalysis. The research combines an experimental and theoretical study focused on the Deacon reaction, an energy-efficient process used to manufacture chlorine from by-product HCl.

Tarragona, 30th July, 2012 – The phenomenon of compensation in heterogeneous catalysis was described by F.H. Constable and E. Cremer at the beginning of the last century. This phenomenon is characterized by a mathematical equation in which two fundamental parameters of a chemical reaction, the enthalpy and the entropy, are linearly related.

Since then, there have been many researchers who have tried to prove this equation by theoretical simulations and model systems. However, due to the complexity of the experimental studies and technical limitations no direct experiments had substantiated these theoretical insights to date.

This study, published in the journal Nature Chemistry *, is the first in which the authors perform state of-the-art experiments and calculations to justify the origin of compensation.

RuO2 Catalyst Surface

RuO2 Catalyst Surface

The paper presents the first accurate experimental in situ quantification of surface coverage of a catalyst, in this case the coverage of RuO2 during HCl oxidation to Cl2. Besides these innovative experimental studies, DFT and massive microkinetic models, more than 2000 calculations, identify the Surface Configurational Entropy terms as the missing key that explains the origin of the compensation and verifies the observations of Constable-Cremer. The authors give a microscopic understanding of why coverage variations imply simultaneous changes in the enthalpies and the entropies of the reaction.

This ground-breaking research improves the understanding of compensation effects in heterogeneous catalysis and it can lead to the optimization and improvement of many chemical processes.


In situ surface coverage analysis of the 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, László Szentmiklósi, Miguel González Hevia, Hary Soerijanto, Reinhard

Schomäcker, Javier Pérez-Ramírez and Núria López

*Nature Chemistry, doi:10.1038/nchem.1411

Surface Configurational Entropy videos:





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