(502g) Ethanol Conversion over Metal Oxides

Ethanol conversion was investigated in a gas-solid tubular flow reactor at atmospheric pressure using both commercial and home-made metal oxides  as catalysts. This research has been performed on the frame of a larger study concerning the possible use of bioethanol as a source of renewable organic compounds. While some zeolites (H-FER, HY) give rise to almost total yield to ethylene at 523 K, the same can be obtained on alumina and silica-alumina at higher temperatures (623 K). Even very small amounts of sodium (100 ppm) decrease catalytic activity of aluminas shifting full conversion at ca. 673 K. Very high yields to ethylene (> 99%) have also been obtained on WO₃-ZrO₂ and WO₃-TiO₂ catalysts at 623 K. Ethylene is also the main product of ethanol conversion on zirconia, titania and calcined hydrotalcite, but with lower yields. In this case, propene production is significant (selectivity < 10%) at high ethanol conversion. Only in the case of ZnO the main products are acetaldehyde (yield >30% at 623 K) and acetone (yield approaching 50% at 723 K).

The addition of lanthanum to alumina produces a shift from dehydration reaction to dehydrogenation one where acetaldehyde production increases as La-loading increases but ethylene is still the major product.

The results have been interpreted as an effect of the surface properties of the different oxides, which were characterized using different techniques as: FE-SEM, XRD, UV-vis, S_BET, FT-IR spectroscopy of the surface -OH’s, of adsorbed CO and of adsorbed pyridine.