A Comparative Study of 4-Methylphenol Hydrodeoxygenation Over High Surface Area MoP and NiP.

Unsupported, high surface area MoP and NiP catalysts were synthesized by adding citric acid (CA) to solutions of ammonium heptamolybdate and diammonium hydrogen phosphate or nickel nitrate and diammonium hydrogen phosphate, respectively, followed by drying (397 K), calcination (773 K), and reduction in H (923 K). The addition of CA increased the surface area, decreased the particle size, and increased the CO uptake of the MoP and NiP catalysts. At 623 K and 4.4 MPa, the NiP was 2.3 times more active than the MoP on a mass basis and 6 times more active on a site basis for the hydrodeoxygenation of 4-methylphenol. However, the NiP catalysts deactivated due to non-selective carbon deposition on the catalyst surface. Oxidation was excluded as a potential cause of deactivation over the NiP catalysts. The rate of deactivation was well described by an exponential decay law. Deactivation was eliminated by operation at higher H pressures (5.3 and 6.1 MPa) but the hydrogenation selectivity of the NiP increased at these conditions. No deactivation was observed over the MoP catalysts at the conditions of the present study. [ABSTRACT FROM AUTHOR]