Enhanced phenol hydrogenation for cyclohexanone production by membrane dispersion

Continuous liquid-phase phenol hydrogenation to cyclohexanone over Pd/Al₂O₃ was conducted in a membrane dispersion based fixed-bed reactor system. The effects of membrane structure on the phenol hydrogenation and gas–liquid two-phase flow were investigated by experimental results coupled with computational studies. The phenol conversion and cyclohexanone yield can be effectively improved by selecting suitable pore size and channel number of membrane. Gas holdup, axial fluid velocity and gas distribution predicted by computational fluid dynamics (CFD) studies provide insights into the relationship between membrane structure and catalytic efficiency. As compared to the phenol conversion and cyclohexanone yield obtained by direct feeding of hydrogen, those are enhanced substantially in the presence of membrane dispersion at the conditions of high LHSV and low hydrogen/phenol aqueous solution volume ratio. A phenol conversion above 85.6% and a cyclohexanone selectivity at ∼98% can be achieved in a continuous phenol hydrogenation to cyclohexanone of 50 h. This work will provide guidance for the green cyclohexanone production.