Unraveling the mechanism of catalytic reactions through combined kinetic and thermodynamic analyses: Application to the condensation of ethanol
Résumé
The combination of kinetic and thermodynamic analyses can provide an in-depth knowledge of the crucial steps of catalyzed reactions. Earlier examples are recalled to stress how a reaction mechanism can be supported or rejected based on trivial reactant and product concentration analyses. The method is then applied to the important reaction of alcohol condensation, the so-called Guerbet reaction, which enables converting ethanol, a renewable feedstock, into higher alcohols. Important conclusions regarding the design of ethanol condensation processes can be drawn, as the main reaction mechanism occurring at high temperatures (ca. 350-420 degrees C) appears to be different from that proposed at low temperatures (< 250 degrees C). In the former case, the pathway involving acetaldehyde is negligible, and therefore a multi-step process based on ethanol dehydrogenation followed by acetaldehyde self-aldolization would be irrelevant. (C) 2014 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.