Kinetic study on the selective catalytic oxidation of 2-propanol to acetone over nickel foils

The kinetics of the catalytic oxidation of 2-propanol with molecular oxygen on clean and oxygen-pretreated Ni foil samples was studied by using a microbatch reactor with mass spectrometry detection. It was found that, under the right conditions, high selectivity for acetone formation can be achieved in this system. Specifically, it was determined that high partial oxidation selectivity requires the use of temperatures below 700 K and oxygen partial pressures higher than stoichiometric, i.e. oxygen-to-alcohol ratios above 1:2. Zero- and half-order kinetics with respect to 2-propanol and oxygen pressures, respectively, were observed for the conversion of 2-propanol to acetone on the clean Ni catalyst. A thin oxide-like layer was determined to be the active catalyst for this reaction, and the rate of oxidation was found to be significantly higher on oxygen-pretreated Ni surfaces. Our kinetic evidence also indicates that the undesirable complete oxidation of the alcohol to CO2 and water is mainly a sequential reaction that takes place on the acetone produced from the alcohol, not a primary alcohol oxidation step. Finally, it was found that dehydrogenation of 2-propanol to acetone in the absence of oxygen is also possible, but occurs at a significantly slower rate than when oxygen is present in the gas mixture, and leads to poisoning of the surface of the catalyst via the deposition of carbonaceous deposits. (C) 2002 Elsevier Science B.V. All rights reserved.