1 Role of the surface intermediates in the activity and stability of basic mixed oxides in ethanol condensation Jorge Quesada, Laura Faba, Eva Díaz and Salvador Ordóñez* Department of Chemical and Environmental Engineering, University of Oviedo, Oviedo 33006, Spain KEYWORDS: Guerbet reaction, DRIFT spectroscopy, butanol, aldol condensation, deactivation ABSTRACT: The gas-phase ethanol self-condensation catalyzed by Mg-Al and Mg-Zr mixed oxides is studied in this work. The highest conversion and 1-butanol (key product) selectivity is obtained with Mg-Al, mainly working at 673 K and with a WSHV of 7.9 h -1 , whereas lower conversions and higher dehydration products are observed with Mg-Zr. The different activity of both materials is related to their surface properties concluding that, despite the complex mechanism, a good distribution of medium-strength basic-acid sites is compulsory to promote the 1-butanol production, whereas acid sites promote dehydration steps, yielding undesired products. The stability of these materials is also studied, by combining the evolution of product concentrations in the gas phase with changes in the catalytic surfaces, observed by spectroscopic techniques (DRIFT), during 8 hours. Both materials present a good stability at 673 K, without significant changes in conversion or selectivities, whereas partial deactivation was produced at higher temperatures (more relevant in the case of Mg-Zr) due to the