The Standard Oil Company

Jeffrey H Schott

David A Palmer

Hobe Schroeder

Water is separated from a mixture of vapors containing 60 to 86 wt. % phthalic anhydride, 5 to 25 wt. % water, 0.8 to 10 wt. % benzoic acid, 0.1 to 4 wt. % o-toluic acid and up to 5 wt. % impurities boiling just above phthalic anhydride (PAN) by a fractionation zone whose reflux liquid is insert to PAN and the aromatic acids and immiscible with water but dissolves PAN at temperatures between its melting and freezing points and also dissolves benzoic acid and o-toluic acid at such temperatures. The reflux liquid or a component thereof when not a single compound leaves the top of the fractionation system as a vapor and does not leave the bottom thereof with PAN. Such water separation technique avoids having PAN vapors in a condenser whose cooled surfaces can and do become coated with solid PAN.

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Naperville, IL, United States of America

Jeffrey H Schott