CATALYTIC-OXIDATION OF ETHANOL AND ACETALDEHYDE IN SUPERCRITICAL CARBON-DIOXIDE

Catalytic oxidation of ethanol and acetaldehyde over a 4.45% Pt/TiO2 c atalyst in supercritical carbon dioxide was studied in a 1/2 in. fixed bed reactor. Experiments for ethanol oxidation were performed at temp eratures from 423 to 573 K and at a pressure of 8.96 MPa with a 5:1 mo lar ratio of oxygen to ethanol in the feed. Acetaldehyde oxidation was performed at temperatures from 423 to 548 K and at 8.96 MPa with an a pproximate 4.7:1 molar ratio of oxygen to acetaldehyde in the feed. In addition to CO2, the complete oxidation product, acetaldehyde and tra ce amounts of CO were generated during ethanol oxidation, while a trac e amount of CO was the only partial oxidation product during acetaldeh yde oxidation. A parallel and consecutive reaction mechanism was postu lated for ethanol oxidation, whereas dissociative adsorption of acetal dehyde on the catalyst surface and surface reaction rate control were postulated for acetaldehyde oxidation. The kinetic parameters in the r ate expressions based on the mechanisms were obtained by fitting the e xperimental data with the results of the model calculation. The models were used to predict the conversion and yield for ethanol oxidation a nd acetaldehyde oxidation.