Selective Phenol Production by Hydrothermal Dehydrogenation of Cyclohexanone over Pd/C without External Oxygen and Hydrogen

摘要

An efficient and greener method for the hydrothermal dehydrogenation of cyclohexanone to phenol using recyclable Pd/C catalyst without external O2 and H2 was first reported. Pd/ C as catalyst exhibited an excellent catalytic performance and hydrothermal stability for the present transformation, and phenol from cyclohexanone was produced in 60.4% yield with 100% selectivity. TON of 8.27 and TOF of 3.31 h~(-1) were achieved, respectively. A poisoning experiment with Hg indicated that Pd/C catalyst was a heterogenous active species. Moreover, Pd/C can be recycled several times without loss of its activity. The scope of substrates, such as substituted ethyl, methyl, phenyl groups and diketones, were investigated under the optimized conditions, and the results showed that more bulky groups exerted a significant influence on the formation of phenol. A possible mechanism for the hydrothermal dehydrogenation of cyclohexanone to phenol was also proposed.