Process for the production of acid anhydrides from epoxides

A method for the continuous production of an acid anhydride, the method comprising the steps of:

• a) contacting an epoxide with carbon monoxide, optionally in the presence of a carbonylation catalyst in a first reaction zone to provide a first product stream comprising a beta-lactone, residual epoxide, and, if present, the carbonylation catalyst;
• b) feeding the first product stream to a second reaction zone, where the stream is contacted with additional carbon monoxide under conditions sufficient to convert substantially all of the residual epoxide to the beta-lactone and to convert a portion of the beta-lactone to an acid anhydride, to provide a second product stream comprising dissolved acid anhydride and, if present, carbonylation catalyst;
• c) treating the second product stream such that the concentration of the acid anhydride in the stream exceeds the solubility of the acid anhydride;
• d) separating solid acid anhydride from the second product stream to produce an acid anhydride product stream comprising solid acid anhydride and a liquid catalyst recycling stream comprising the dissolved catalyst, if present, and dissolved acid anhydride;
• and
• e) returning the liquid catalyst recycling stream to an inlet of the first reaction zone, wherein the acid anhydride is a succinic anhydride.