Key words: isopropanol, water, oxides, dehydration, dehydrogenation, reduction.
Transformations of a series of simple oxides (Al2O3, SiO2, La2O3, CeO2, PrO2) during their treatment in an autoclave with isopropanol (i-C3H7OH) under supercritical (SC) conditions and subcritical water vapor were studied. It has been shown that at 350 °C in the presence of water vapor, a more intense decrease of specific surface areas and the transition of some of them (oxides of aluminum, lanthanum and praseodymium) into hydroxides occur. Under the influence of i C3H7OH for 6 hours at 350 °C almost complete conversion of PrO2 occurs, accompanied by its reduction and partial transition to hydroxide. In the case of CeO2, no transformations in both media (i C3H7OH, water vapor), including a decrease in specific surface area, hydration and reduction, were observed. The differences in the behavior of CeO2 and PrO2 are explained by the difference in the values of the 4th ionization potential of the Ce and Pr atoms and, as a consequence, in the binding energies of oxygen in higher oxides. The formation of products of various reactions of i-C3H7OH was detected, the composition of which depends on the type of oxide being processed. The most intense transformation of i-C3H7OH occurs in the presence of Al2O3; in this case, dehydration products (propylene, diisopropyl ether) are formed predominantly. In the presence of La, Ce and Pr oxides, the dehydrogenation process is more intense with the formation of acetone and hydrogen (maximum in the presence of La2O3). The catalytic nature of the isopropanol decomposition in the presence of the studied simple oxides has been established. SiO2, which does not have pronoun- ced acid-base and redox properties, exhibits the least activity in the decomposition of i- C3H7OH. It has been suggested that when oxides are treated with SC isopropanol, their structuring occurs under the action of water vapor, which is a product of the transformation of i-C3H7OH. The catalytic activity of the autoclave material (stainless steel) in the decomposition of i C3H7OH along both routes — dehydration and dehydrogenation — was noted.