Vapor-phase ketonization of aliphatic acids on a chromite catalyst

Abstract

The catalytic conversion of acetic, propionic, and butyric acid in the presence of water vapor on oxide chromium-zinc-manganese catalyst promoted by potassium carbonate in the temperature range 300–400°C was studied. The main products of the acids conversion were found to be symmetrical ketones, water, and carbon dioxide. The optimum yield of ketones is achieved at 325°C. The yields were as follows: up to 96 mol % of acetone, 95 mol % of diethyl ketone, and 92 mol % of dipropyl ketone. A side reaction is the decarboxylation of acids, the contribution of which increases with increasing temperature. Under these conditions a clevage of molecules with the formation of lower ketones, hydrogen, methane, and carbon monoxide. Yield of symmetrical ketones from aliphatic acids is much higher than from the corresponding aldehydes and alcohols, and the maximum yield is obtained at a lower temperature. By the example of ketonization of the acetic acid it was found that the reaction proceeds quite successfully at reducing the water concentration in the reaction mixture. This enabled us to improve the performance of the process of ketones production.