Acetic Acid → Acrylic anhydride

In this example, the mole ratio between acrylic acid and acetic anhydride is equal to 1.5. The reaction mixture is subjected to stirring and, throughout the reaction which lasts for 5 hours, the acetic acid is drawn off under a pressure of 100 mmHg, the temperature being 85° C. at the beginning of the reaction and 95° C. at the end of the reaction. In addition, during the reaction and during the distillation, 500 ppm of copper sulphate and 500 ppm of phenothiazine are gradually introduced into the top of the distillation column. After the reaction, distillation is performed. There are distilled, as a first fraction, unreacted acetic anhydride and acrylic acid, acrylic acetic mixed anhydride as well as a little acrylic anhydride, under 200 mmHg at a temperature of 57° to 76° C. under 20 mmHg. This fraction represents 140 parts by weight. The acrylic anhydride is then distilled at 76° C. under 20 mmHg. 250 parts by weight of acrylic anhydride are collected. The yield is 75%.