title: Transition Metal Phosphide Nanoparticles Supported on SBA-15 as Highly Selective Hydrodeoxygenation Catalysts for the Production of Advanced Biofuels.
abstract: A series of catalysts constituted by nanoparticles of transition metal (M = Fe, Co, Ni and Mo) phosphides (TMP) dispersed on SBA-15 were synthesized by reduction of the corresponding metal phosphate precursors previously impregnated on the mesostructured support. All the samples contained a metal-loading of 20 wt% and with an initial M/P mole ratio of 1, and they were characterized by X-ray diffraction (XRD), N2 sorption, H2-TPR and transmission electron microscopy (TEM). Metal phosphide nanocatalysts were tested in a high pressure continuous flow reactor for the hydrodeoxygenation (HDO) of a methyl ester blend containing methyl oleate (C17H33-COO-CH3) as main component (70%). This mixture constitutes a convenient surrogate of triglycerides present in vegetable oils, and following catalytic hydrotreating yields mainly n-alkanes. The results of the catalytic assays indicate that Ni2P/SBA-15 catalyst presents the highest ester conversion, whereas the transformation rate is about 20% lower for MoP/SBA-15. In contrast, catalysts based on Fe and Co phosphides show a rather limited activity. Hydrocarbon distribution in the liquid product suggests that both hydrodeoxygenation and decarboxylation/decarbonylation reactions occur simultaneously over the different catalysts, although MoP/SBA-15 possess a selectivity towards hydrodeoxygenation exceeding 90%. Accordingly, the catalyst based on MoP affords the highest yield of n-octadecane, which is the preferred product in terms of carbon atom economy. Subsequently, in order to conjugate the advantages of both Ni and Mo phosphides, a series of catalysts containing variable proportions of both metals were prepared. The obtained results reveal that the mixed phosphides catalysts present a catalytic behavior intermediate between those of the monometallic phosphides. Accordingly, only marginal enhancement of the yield of n-octadecane is obtained for the catalysts with a Mo/Ni ratio of 3. Nevertheless, owing to this high selectivity for hydrodeoxygenation MoP/SBA-15 appears as a very promising catalyst for the production of advanced biofuels.
authors.forename: Yongxing
authors.initials: Y
authors.lastname: Yang
authors.forename: Cristina
authors.initials: C
authors.lastname: Ochoa-Hernández
authors.forename: Víctor A
authors.initials: VA
authors.lastname: de la Peña O'Shea
authors.forename: Patricia
authors.initials: P
authors.lastname: Pizarro
authors.forename: Juan M
authors.initials: JM
authors.lastname: Coronado
authors.forename: David P
authors.initials: DP
authors.lastname: Serrano
mesh_terms: D056804:Biofuels; D002384:Catalysis; D006865:Hydrogenation; D053768:Metal Nanoparticles / Q000737:chemistry*; D010720:Phosphines / Q000737:chemistry*; D010938:Plant Oils / Q000737:chemistry / Q000378:metabolism; D012822:Silicon Dioxide / Q000737:chemistry*; D028561:Transition Elements / Q000737:chemistry*; D014280:Triglycerides / Q000737:chemistry / Q000378:metabolism
chemical_list: D056804:Biofuels; D010720:Phosphines; D010938:Plant Oils; C509969:SBA-15; D028561:Transition Elements; D014280:Triglycerides; D012822:Silicon Dioxide