JPS5498715A - Preparation of oxalic acid - Google Patents

Abstract

PURPOSE: To prepare oxalic acid, useful as chemicals, dyeing additives, reagent for analysis, etc., through successive processes comprising hydrolyzation of alkyl oxalate, phase-separation to an organic phase and an aqueous phase, recycling of the organic phase to the hydrolyzing process, and crystallization of oxalic acid from the aqueous phase.

CONSTITUTION: An alkyl oxalate (1 part by weight) and water (0.8W5 parts by weight) are introduced into the hydrolyzing vessel 1 through the tube 6 and the tube 7, respectively. The evaporated alcohol and water are condensed with the condenser 4. The water is taken out of the reaction vessel and circulated through the tube 10. The hydrolysis solution is introduced into the phase separation vessel 2 through the tube 11, and separated into an organic phase and an aqueous phase. The organic phase is circulated through the tube 12. The aqueous phase is introduced through the tubes 13 and 14 into the crystallization vessel 3, and crystals of oxalic acid are taken out from the tube 19. On the other hand, the residual solution is circulated through the tube 18. The following process comprising the separation of the alcohol dissolved in the aqueous phase in the distillation column 5 followed by the recycling of the residual solution into the crystallization vessel 3, may be added in option.

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