High Pressure Synthesis of Acetic Acid from Methanol and Carbon Monoxide

Abstract

Kinetic studies have been made on the high pressure synthesis of acetic acid from methanol and carbon [monoxide] catalyzed by phosphoric acid. The reaction proceeds in the phosphoric medium between the dissolved carbon monoxide and the dissolved methanol, the vapor of the latter being in equilibrium with the dehydration products i. e., dimethylether and water, and the reaction is of the first order with respect to each component.A theoretical rate equation has been derived which can explain quantitatively the effects of operation variables such as the carbon monoxide pressure and the charge ratio of methanol, water or phosphoric acid; the rate constant is 7.5×10-5atm-1min-1 at 370°C and the activation energy is 27kcal/mole.Owing to the occurrence of side reaction producing tarry matters above 390°C, the optimum reaction temperature is confined to 370°C.The activity of the catalyst increased gradually for the first 2 hours at 370°C, and remained constant thereafter. Furthermore, no change was observed in the activity of the regenerated catalyst, thus, the catalyts appears to have a fairly long life.