Rhodia Operations

Thierry Alban Marcel Vidal

Pierre Marcel Ardaud

Rabih Rached

Rabih Julien Rached

The present invention relates to a process for preparing an anhydride of formula A-C(&#x2550;O)&#x2014;O&#x2014;(O&#x2550;)C-A, where A is &#x2014;CR&#x2550;CH2 and R is &#x2014;H or &#x2014;CH3, comprising: a) a step of reacting an anhydride B&#x2014;C(&#x2550;O)&#x2014;O&#x2014;(O&#x2550;)C&#x2014;B with an acid A-COOH, A being as defined above, wherein the step results in the formation of an anhydride A-C(&#x2550;O)&#x2014;O&#x2014;(O&#x2550;)C&#x2014;B and of an acid B&#x2014;COOH, A and B being such that said acid B&#x2014;COOH is more volatile than said acid A-COOH, and b) a step of reacting said anhydride A-C(&#x2550;O)&#x2014;O&#x2014;(O&#x2550;)C&#x2014;B with the acid A-COOH under conditions such that the amount of acid B&#x2014;COOH is less than the amount of acid A-COOH, resulting in the formation of the anhydride A-C(&#x2550;O)&#x2014;O&#x2014;(O&#x2550;)C-A, in which said reaction steps are carried out in the presence of an acid catalyst which is more volatile than said anhydride A-C(&#x2550;O)&#x2014;O&#x2014;(O&#x2550;)C-A.

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Lyons, France

Thierry Alban Marcel Vidal