The Catalytic Decomposition of Isopropyl Alcohol Vapor on Manganese (II) Oxide

Abstract

The vapor phase decomposition of isopropyl alcohol has been studied from 210 to 365 °C on manganese(II) oxide. Rates of conversion to acetone and propylene were measured with partial pressures of isopropyl alcohol from 0.3 to 22 mm. The catalyst selectivity towards dehydrogenation was around 0.80 between 320 and 365 °C while at 306 °C it was somewhat less and depended on the alcohol partial pressure. Propylene and hydrogen additions had no effect on the reaction rate while the reaction order with respect to isopropyl alcohol partial pressure was 0.4 to 0.6 except at 306 °C when it decreased with increase in the alcohol partial pressure. The effects of acetone and water additions were shown respectively to be exerted mainly on the dehydrogenation and dehydration reactions while at acetone pressures above 4 mm, considerable amounts of by-products including mesityl oxide and heavier ketones were clearly detected. The apparent activation energy of the overall decomposition as calculated from the experimental rates was 26 ± 0.5 kcal mol −1 . The results have been interpreted to be in general agreement with the concept that the rate-limiting step is linked to the direct interactions on the catalyst surface and it has been established that the reaction is significantly more complex than previously recognized. The physical properties of the manganese(II) oxide were determined by X-ray and nitrogen adsorption techniques while infrared, n.m.r., and gas chromatographic methods were used to analyze the products of catalysis.