Mesoporous molecular sieve Al-MCM-41 as a novel catalyst for vapor-phase Beckmann rearrangement of cyclohexanone oxime

Vapor-phase Beckmann rearrangement of cyclohexanone oxime to epsilon -caprolactam has been studied at 1 atm and 300-400 degreesC using mesoporous molecular sieve Al-MCM-41. Benzene and ethanol are utilized as solvents for cyclohexanone oxime. Increasing the reaction temperature enhances the catalyst activity and stability whereas epsilon -caprolactam selectivity varies only slightly. Ethanol exhibits much better catalytic results than benzene. Excellent catalyst performance is attained at 1 atm, 400 degreesC and W/F-C 149.2 g h/mol by using ethanol in the feed; the cyclohexanone oxime conversion and the epsilon -caprolactam selectivity remain higher than 99 and 90%, respectively, during at least 1200 h process time. The highly efficient catalysis on Al-MCM-41 is attributed to its large surface area, uniform mesopores as well as the weak and medium acidity.