The effect of catalyst composition and surface properties on the selective catalytic dehydrogenation of bioethanol

Abstract

The article provides a comparative analysis of bioethanol dehydrogenation using Cr-Cu-O and Ce-Cu-O catalyst systems. For the Cr-Cu-O catalysts, bioethanol is converted into a range of products including acetaldehyde, acetone, ethylene. Advanced characterization revealed that these catalysts are structurally complex, containing not only just individual copper and chromium oxides but also a distinct compound, Cu₂CrO₄. A key finding is the clear structure-property relationship: the catalyst's crystallinity, which varied widely from 41.9% (mostly amorphous) to 73.8% (highly crystalline), has a major effect on its catalytic activity. The Ce-Cu-O system converted bioethanol into a diverse mixture of products such as acetaldehyde, acetone, and ethyl acetate, indicating the occurence of multiple simultaneous reactions, including dehydrogenation and condensation. Most compositions result in separate CeO₂ and CuO phases; however, a specific Ce:Cu ratio of 1:9 is unique. At this ratio, the material reduced to form CeO₂ with elemental copper, rather than CuO, and its crystallinity increases from 52.7% to 71.2%. The research shows that structural order is crucial for steering the reaction pathway, as only catalysts with low crystallinity produce ethyl acetate. Furthermore, while the specific surface area of a catalyst (5.0 to 17.0 m²/g in this study) is a key factor in surface-driven reactions such as dehydrogenation, it does not affect all products equally.