Pulse and IR Study on the Reaction Pathways for the Conversion of Ethanol to Propene over Scandium-Loaded Indium Oxide Catalysts

Potential reaction intermediates in the conversion of ethanol to propene, acetaldehyde, ethyl acetate, crotonaldehyde, acetic acid, acetone, and 2-propanol were introduced as pulses onto a scandium-loaded indium oxide catalyst. The product distributions were primarily measured as a function of the space velocity in the absence or presence of hydrogen and water. The FT-IR spectra of the surface adsorbates were also collected after ethanol adsorption and indicated the formation of ethoxide species, which were converted to acetate species over the catalyst. The proposed reaction route involved the dehydrogenation of ethanol to acetaldehyde, direct oxidation of acetaldehyde with water or a surface hydroxyl group to yield acetic acid, ketonization of acetic acid to acetone and carbon dioxide, and hydrogenation and subsequent dehydration of acetone to propene. The total reaction can be described as 2 CH 3 CH 2 OH → CH 2 ═CHCH 3 + CO 2 + 3 H 2 . A side reaction involving isobutene formation also occurred via the acetone intermediate.