Organic reactions with solid catalysts under supercritical carbon dioxide are green sustainable because: i) high reaction rates due to increased solubility of reactant gases in supercritical fluid, thereby eliminating mass transfer resistance; ii) easy separation of catalysts and products, iii) eliminating the use of organic solvents. Catalytic ring hydrogenation of phenol to KA oil (the mixture of cyclohexanol and cyclohexanone) was demonstrated with the green chemical process. A charcoal-supported rhodium catalyst was highly active for the ring hydrogenation of phenol to KA oil at 328K under supercritical carbon dioxide, while gas reactions at > 453K palladium is reported to be a suitable catalyst for this reaction.