| abstract |
Fumaric acid is produced from the wash waters of exhaust gases resulting from hydrocarbon oxidation, which contain maleic acid. The process comprises a thermal pre- treatment of the impure maleic acid solution, with optional concurrent concentration, with transformation of part of the impurities to facilitate their elimination from the final product, subsequent hot filtration, isomerization of the maleic acid to fumaric acid, crystallization according to a pre-set time/temperature chart, removal of the mother liquors by filtration, subsequent dissolution in water or in a fumaric acid solution, decolorization, recrystallization and drying. |