Abstract
Cyclohexanone is an important industrial intermediate to produce nylons. The main industrial routes for cyclohexanone manufacture used cyclohexane and phenol as feedstock. The selective hydrogenation of phenol to cyclohexanone comprises one-step and two-step processes. This review presents a detailed analysis of the research findings available in the open literature for phenol hydrogenation to produce cyclohexanone and cyclohexanol and covers the research conducted during 2014-2020 using conventional and modern catalysts. This review aims to disseminate the knowledge of the current research conducted for phenol hydrogenation and provide a comprehensive resource for researchers working in this field. This review has included and discussed both methods of thermocatalytic and electrocatalytic hydrogenation of phenol. Most of the studies have used carbon or carbon-nitrogen supported catalysts loaded with Pd. The carbon and carbon-nitrogen materials were derived from different sources including polymers, activated carbon, and MOF. Oxygen treatment was found to produce highly active and stable catalysts. The high performance was found associated with the high surface area of the catalyst and uniformly dispersed metal nanoparticles. The acidic conditions exhibited an increase in catalyst performance. Alkali-promoted precious metal-loaded catalysts performed better than un-promoted catalysts.