Enhanced HDO activity of Ni2P promoted with noble metals

Abstract

A series of bimetallic Ni₂P–noble metal (Pt, Rh, Ir or Ru) catalysts supported on commercial silica were prepared in order to evaluate the promoter effect of noble metals on the activity and stability of these catalysts in the hydrodeoxygenation (HDO) of dibenzofuran (DBF), as a model oxygenated compound, at P = 3.0 MPa and 175–300 °C. Ni₂P and Ni_1.8M_0.2P catalysts were characterized by X-ray diffraction (XRD), N₂ adsorption–desorption at −196 °C, X-ray photoelectron spectroscopy (XPS), CO chemisorption and H₂-thermoprogrammed desorption. Bimetallic catalysts containing Rh, Ru and Ir showed excellent catalytic behavior in the HDO reaction of DBF, greater than their corresponding monometallic counterparts. The results suggest that there is a synergic effect between both phases mainly at low temperatures. The addition of Pt worsened the catalytic activity of the monometallic phases. The enhanced activity of the catalysts containing Rh, Ru and Ir was ascribed to the presence of greater amounts of H-active species on the surface as well as an increase in Ni surface exposure during the catalytic test. The poor catalytic activity of the Pt-containing catalyst could be due to the possible formation of a solid solution as observed from XPS and CO-chemisorption data, which seems to be detrimental to the catalytic response of these systems.