Patent ID: 6664417
Filing Date: 2003-12-16
Classification: C07C,C07D

Abstract:
A process for the preparation of citraconic acid in an aqueous solution which comprises:(a) contacting a molar excess of an aqueous solution of formaldehyde, gaseous formaldehyde or trioxane in a solvent with at least one compound selected from the group consisting of mono- and di-lower alkyl esters of succinic acid in vapor phase with a metal oxide catalyst at a temperature from about 320Â° to 440Â° C., at a pressure from about 20 to 400 psi, at a Weight Hourly Space Velocity (WHSV) from about 0.3 to 4 kg succinate/hr*kg catalyst, the catalyst consisting of a porous material having a surface area between about 30 m2/g and 700 m2/g, surface acid site density from about 66 to 2350 micromole/g, surface base site density from about 0 to 500 micromole/g and acid strength (pKa) of about +3 to âˆ’3 until reaction is substantially, complete to produce citraconic anhydride and unreacted ester of succinic acid which is recycled and methanol in the aqueous solution said lower alkyl having from 1 to 4 carbon atoms; (b) separating the methanol and unreacted formaldehyde or trioxane from the aqueous solution; (c) hydrolyzing the citraconic anhydride to citraconic acid and the ester of succinic acid to succinic acid at elevated temperatures in the aqueous solution while evaporating water from the aqueous solution and crystalizing the succinic acid from the aqueous solution to produce the citraconic acid in an aqueous solution.