Oxidative dehydrogenation of isobutyric acid on V 2O 5P 2O 5 catalysts

Abstract

V 2O 5P 2O 5 binary oxides were found to be effective for the synthesis of methacrylic acid (MAA) in the vapor-phase air oxidation of isobutyric acid (IBA), much like vanadium-containing heteropoly compounds. The products are MAA, acetone, propylene, and carbon oxides. With an increase in the content of phosphorus, the selectivity to acetone steadily decreases, while that to propylene increases. The selectivity to MAA passes through a maximum (50 to 60 mol%) at a P V atomic ratio between 1.0 and 1.6, and it is little affected by the method of catalyst preparation. It was found that the selectivity is clearly related to the acid-base property of the catalyst. The oxidation activity attains a maximum at P V = 1.0 to 1.6 , and the activities of the V-P (1–1.6) catalysts are of the same order of magnitude as that of H 5PMo 10V 2O 40. The effects of reaction variables, such as oxygen concentration, IBA concentration, water vapor, and temperature, on activity and selectivity were studied for both the V 2O 5P 2O 5 and H 5PMo 10V 2O 40 catalysts, and an attempt was made to clarify the difference in catalytic performance between V 2O 5P 2O 5 and H 5PMo 10V 2O 40.