Study On The Recovery Of Caprolactam From Waste Solution

Caprolactam is the most important raw material to polymerize Nylon6. SNIA method is an advanced technics. But lots of waste oil companied by the process, including C6H6, C7H8, CPL, have a negative effect on the environment and the product ratio. Therefore, recovery CPL form the waste solution with suitable method is the requirement for industrial production. Extraction and vacuum distillation to purify CPL were studied in this paper.Optimized gas chromatography (GC) conditions suitable for the extraction phase, raffinate phase and CPL product were established:Column temperature180℃, injection temperature 280℃and detective temperature250℃.The influences of solvent ratio and dilution ratio on the extraction process were studied by the extraction experiments. Preferable extraction conditions was: water as extractant, solvent ratio1:1and extraction temperature 30℃.In the paper, four groups of liquid-liquid equilibrium(LLE) data were measured in the CPL-water- C6H6 system at 30℃and 45℃, dilution ratio 4:1 and 2:1. The LLE data were correlated by Hand equation to obtain a practical formula for the design of industrial continuous extraction process. Multi-stage countercurrent extractions were studied compared by the academic result.The water phase from extraction and multi-stage extraction were concentrated and then refined in a vacuum distillation column.With the reflux ratio 6 and absolute pressure 1~1.5KPa, the one-pass purity of CPL was up to 97.8%.