Process for producing caprolactam
AssigneeSumitomo Chemical Company, Limited
InventorsFusao Oyama, Sadatomi Murao, Shizuo Okada
Life of this patent
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Abstract
Treatment of process waste waters to be discharged from a lactam manufacturing plant by stepwise concentration in two steps under suitable conditions, extraction of lactam from the concentrate with an organic solvent, oxidative combustion of the extract residue and conversion of sulfur dioxide formed into sulfuric acid can save losses of lactams, organic solvents and sulfur containing compounds to a considerable extent and render the waste waters no longer harmful.
Claims9
A process for producing caprolactam by effecting Beckmann rearrangement of cyclohexanone oxime with a concentrated sulfuric acid or fuming sulfuric acid, neutralizing the rearranged mixture with ammonia and separating ammonium sulfate and caprolactam from the neutralized product, wherein the improvement comprises treating process waste waters after separation of said ammonium sulfate and caprolactam in accordance with the following steps:
- (1) first concentrating by distillation at a temperature in the range from 80.degree. to 130.degree. C under a pressure in the range from 400 mm Hg to 2.7 Kg/cm.sup.2 to a water concentration in the range from 85 to 75 wt.%;
- (2) then further concentrating by distillation of the concentrate at a temperature in the range from 40.degree. to 80.degree. C under a pressure in the range from 50 to 400 mm Hg to a water concentration in the range from 70 to 15 wt.%;
- (3) extracting the caprolactam from the thus obtained concentrate at a pH controlled to a pH between 2.5 and 6 with an aromatic hydrocarbon as an extraction solvent thereby to recover the caprolactam;
- (4) conducting oxidative combustion of the extraction residue at a temperature in the range from 800.degree. to 1300.degree. C;
- and,
- (5) converting the thus formed sulfur dioxide to sulfuric acid.
Dependencies are inferred from the claim text.