Vapor-phase reaction of methanol with methyl acetate and acetic acid in the presence of oxygen

Abstract

Vapor-phase reactions of methanol with methyl acetate and acetic acid in the presence of gaseous oxygen were studied using a binary phosphate catalyst with a V/Ti/P atomic ratio of 1/2/5.2. In the presence of gaseous oxygen, methyl acetate itself undergoes hydrolysis to methanol and acetic acid, then the produced methanol is oxidized promptly to formaldehyde, and finally the formaldehyde reacts with acetic acid and methyl acetate. The yields of acrylic acid and methyl acrylate attained 21 and 13 mol%, respectively, at 330 °C with SV = ca. 310 h −1. In the presence of an excess of oxygen, the sum of the yields of acrylic acid and methyl acrylate was almost the same, whether one of the reactants was formaldehyde or methanol, and whether methanol was fed in with methyl acetate or acetic acid. It was found that the oxidation of methanol and the esterification-hydrolysis proceed much more promptly than the aldol condensations. In the reaction of methanol with acetic acid at 350 °C with a feed rate of CH 3COOH/CH 3OH/O 2/N 2 = 19/38/25/350 mmol/h (SV = ca. 340 h −1), the yields of acrylic acid and methyl acrylate attained 42 and 13 mol% (based on the charged acetic acid), respectively, and the selectivity of acetic acid to the condensation products was about 73 mol%.