(448g) A DFT Study of the Support Effect on Hydrodeoxygenation Reaction

Catalysts used in hydrotreating of renewable oil are typically composed of sulfide active phases (NiMoS or CoMoS) on catalyst supports. The catalyst support in the hydrotreating reaction was originally considered as inert and only served to provide enlarged surface area.¹ However, the progress in this area challenges this concept. Literature has shown that catalyst support in hydrogenation reaction could affect catalyst activity, stability and selectivity. This is due to different textural properties (e.g. surface area and pore size) of catalyst support, catalyst-support interaction, crystal structure and acidity property provided by catalyst support.^2,3

In this work, DFT was used to investigate the catalyst support effect on the hydrodeoxygenation reaction, with a focus on the reaction of propanol to propane. We present the elementary steps for the hydrodeoxygenation reaction of propanol to propane over NiMoS catalyst in four stages: hydrogen dissociation, water removal, hydrogen migration and propane formation. Among these elementary steps, hydrogen dissociation and C-O bond cleavage were identified as the most critical due to their high activation energies. These two elementary steps were further studied on NiMoS with different catalyst supports: TiO₂, SiO₂ and Al₂O₃. Catalyst support can affect the elementary steps by providing different electron structures, electronic properties and catalyst-support interactions. The detailed effect of catalyst support on these two critical elementary steps in hydrodeoxygenation reaction will be discussed and presented.

Reference:

1. Coenen, J. W. E. Catalytic Hydrogenation of Fatty Acids. Ind. Eng. Chem. Fundam. 1986, 25, 43–52.
2. Candia, R.; Sorensen, O.; Villadsen, J.; Topsoe, N.; Clausen, B. S.; Topsoe, H. Effect of Sulfiding Temperature on Activity and Structures of Co-Mo/Al₂O₃ Catalysts. Ii. Bulletin des Sociétés Chimiques Belges 1984, 93 (8–9), 763–774.
3. Vissers, J. P. R.; Scheffer, B.; De V. H. J., B.; Moulijn, J. a; Prins, R. Effect of the Support on the Structure of Molybdenum-Based Hydrodesulfurization Catalysts: Activated Carbon versus Alumina. Journal of Catalysis 1987, 105 (2), 277–284.