Catalytic Condensation of Carbonyl Compounds during the Synthesis of Cyclohexanone in the Production of Caprolactam

Kinetic features of the condensation processes of carbonyl and unsaturated impurities in cyclohexanone have been studied using model mixtures in a heterophase system in the presence and absence of phase-transfer catalysts. It has been shown that linear aldehydes are condensed with cyclohexanone in the heterophase system in the presence and absence of phase-transfer catalysts under mild conditions (30–50°C). Noncarbonyl unsaturated compounds (e.g., 2-cyclohexene-1-ol) can be removed only at temperatures above 100°C in the presence of acidic catalysts (e.g., high-temperature sulfonated cation-exchange resins). Unsaturated cyclic ketones are characterized by both alkylation reactions over acid catalysts and aldol condensation reactions in the presence of an alkali, thereby suggesting the possibility of their elimination at different cyclohexanone purification steps. The theoretical models built can be used to develop an effective cyclohexanone purification technology that will substantially enhance the manufacturability of high-purity caprolactam and polyamide.