Unsupported MoS2 and CoMoS2 catalysts for hydrodeoxygenation of phenol

The structural properties and catalytic functionality of two different morphologies of unsupported MoS₂ catalysts were investigated systematically. Hydrodeoxygenation (HDO) of phenol was used as the model reaction to examine the effect of the catalyst structure on the hydrogenolysis and hydrogenation activity and selectivity. The unsupported MoS₂, with amorphous and highly bent multi-layer structures, was much more active than the highly crystalline structured MoS₂ and resulted in direct oxygen elimination. Co promoter showed a strong effect on the activity and selectivity of Mo sulfides. Temperature programmed reduction (TPR) exhibited the close interaction between Co and Mo in the bimetallic sulfide catalysts resulting in shift of TPR peaks to lower temperatures. The addition of promoter also affected the textural properties of amorphous Mo sulfide by decreasing the surface area, changing the pore characteristics and shifting the pore-size distribution towards smaller sizes. The growth of MoS₂ crystallized particles was inhibited when Co was incorporated. The enhanced catalytic activity observed with the promoter addition was essentially due to the enhancement of the rate of direct-deoxygenation route. The present study indicated that the activity and selectivity for phenol HDO can be controlled by tailoring the morphology and the promoter of the unsupported MoS₂ catalysts.