Transformation of Phenol over an Unsupported NiMoS Catalyst: Water as a Source of In Situ Hydrogen and a Cosolvent for Tuning Selectivity to Hydrocarbons

We report the water-assisted transformation of phenol, a lignocellulose-derived bio-oil component, into value-added hydrocarbons over an unsupported NiMoS catalyst. The catalyst was produced by dispersing oil-soluble metal salts in a water-in-oil emulsion containing a sulfiding agent precursor, which enabled the self-assembly of active sulfide species. Water was found to serve a dual function: (i) as a source of in situ hydrogen generated via the water–gas shift reaction (WGSR) and (ii) as a cosolvent, facilitating both the targeted transformation of reactants and the separation of products based on their polarity differences. It was demonstrated that in the water-assisted process, phenol-derived cyclohexene undergoes isomerization to methylcyclopentane or reacts with phenol to form bicyclic hydrocarbons. The optimal CO:H2O molar ratio was found to be in the range of 1.2–1.8. Effective transformation of phenol into hydrocarbons was achieved under a CO pressure of 3–5 MPa with a water content of 20–30 wt %. At 380–400 °C, the selectivity toward methylcyclopentane and bicyclic hydrocarbons reached 20 and 15%, respectively, while the selectivity for cyclohexane was as high as 50%. The hydrogenation pathway was predominant, whereas selectivity to benzene, which formed via the direct deoxygenation route, did not exceed 13–15%. The water-assisted hydroconversion process may represent a promising “one-pot” strategy for producing biofuel components or biobased chemicals.