Caprolactam recovery by a column packed with polysulfone microcapsules containing 1-octanol

Caprolactam recovery from its dilute aqueous solution is a challenging task in industry. To save resources and protect environment, a caprolactam recovery technology based on extractant microcapsules as the separation material was introduced. In this new technology, polysulfone microcapsules containing 1-octanol were packed in a column. In the extraction process, recovery ratio of 0.99 was achieved within 0.6 bed volume. More than 10 theoretical plates per meter microcapsule column were realized. In the regeneration process, sulfuric acid aqueous solution was introduced as the stripping agent. Accordingly the new technology can be integrated with existing caprolactam production process because the eluent could be returned to NH3 causticization section. Caprolactam was successfully stripped and concentrated. Caprolactam concentration of 112 g/L in the eluent was obtained. New technology based on extractant microcapsules shows high efficiency in caprolactam recovery.