PROCESS FOR THE MANUFACTURE OF CITRACONIC ACID ANHYDRIDE

1,172,125. Citraconic acid anhydride. H. PICHLER. 18 July, 1967 [29 July, 1966], No. 32903/67. Heading C2C. [Also in Division C1] Citraconic acid anhydride is prepared by the catalytic gas phase oxidation of gases containing isoprene in admixture with oxygen or oxygen containing gases at a temperature between 200‹ and 500‹ C. over a catalyst containing V 2 O 5 . Good results are obtained using an SnO 2 .V 2 O 5 catalyst at 250-400‹ C. and a pure isoprene : air volume ratio of 1 : 80-200 respectively and a contact time of 0À05 to 5 sees., preferably 0À5 sees. Other products resulting from the oxidation include furan-3- aldehyde, 3-methyldihydrofuran, acetic acid, carbon monoxide and carbon dioxide.