Catalytic ketonization over metal oxide catalysts. XIII. Comparative measurements of activity of oxides of 32 chemical elements in ketonization of propanoic acid

• A systematic study of ketonization of propanoic acid in the presence of oxide catalysts was performed.
• The oxides of U, Th, Ce, Zr, Mn proved to be the most active.
• No synergistic effect was noted in binary oxide systems.
• Potassium ions significantly decrease the activity of the uranium oxide catalyst, but not that of thorium.
• Although Th and U catalysts are equally active, the use of the former is strongly recommended due to its much lower radioactivity.

The ketonization of propanoic acid in the presence of many metal oxides deposited on the surface of inorganic supports leads to the formation of 3-pentanone as the main product. This paper is the first to investigate simple oxides of Ag, Bi, Cd, Cu, In, Pb, Re, Cr, Mg, Zn, Ca, Ga, Sr, Ba, Al, Eu, Gd, V, Co, Fe, La, Mn, Zr, Ce, Th and U in the ketonization of propanoic acid under the same conditions. Such experiments allowed us to compare the activities of these oxides. Our results clearly show that the studied oxides can be divided into three groups: slightly active, fairly active and highly active. The last group consists of catalysts containing oxides of: manganese, zirconium, cerium, thorium, and uranium. It has also been checked whether any binary catalytic system containing two of these very active oxides shows a higher activity than the single oxide systems. However, no synergistic effect was noted between these oxides. Moreover, the influence of the addition of an alkali metal cation (K+) to the two most active catalysts on their activities has been studied. The results of these experiments indicate that the addition of potassium cations to uranium oxide significantly decreases its activity in this reaction due to the formation of potassium uranates, whereas thorium oxide is much more resistant to alkali metal ion poisoning. Another reason why thorium catalysts are better for practical implementation is their significantly lower radioactivity.

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