Enhancement effect of organic additives on liquid-phase production of ε-caprolactam

The effect of various organic additives on the catalytic performance of zeolites and Al-containing MCM-41 in the liquid-phase Beckmann rearrangement of cyclohexanone oxime was investigated at 130 °C using benzonitrile as solvent. Over USY zeolite with a large amount of extraframework aluminum (EFAL), the lactam yield was dramatically improved, up to 82%, by adding ethanol, dimethyl sulfoxide, ammonia, diethylamine, or pyridine to the oxime solution. It is due to a selective adsorption of these additives on the detrimental hydrolysis sites as suggested by FTIR results. On the other hand, the additives enhanced both the oxime conversion and the lactam yield through a promotion of the desorption of lactam product from acid sites when beta zeolite and Al-MCM-41 with relatively low EFAL content were used as catalysts.