Deoxygenation of esters over sulfur-free Ni-W/Al2O3 catalysts for production of biofuel components

Sulfur-free Ni-W/Al2O3 catalysts synthesized through incipient wetness impregnation technique were investigated in deoxygenation of methyl palmitate and ethyl caprate blend at 300 degrees C and P = 1 MPa (PH2 = 0.25 MPa) in a fixed-bed continuous flow reactor. Modification of Ni/Al2O3 catalysts by W (0.4-4.4 wt %) was found to give rise to higher both conversions of the feedstock and deoxygenation degree. In addition, this also resulted in a change in the selectivity of deoxygenation towards alkanes formed via direct hydrodeoxygenation route, compared to alkanes formed through decarboxylation/decarbonylation. Selectivity by alkanes with carbon chain length equal to those of an initial fatty acid formed via hydrodeoxygenation was found to increase withW content increasing. The synthesized catalysts were investigated by XRD, XPS, TEM, BET and H-2-TPR techniques. According to XPS study of the reduced samples, tungsten was in 6+ oxidation state on the sample surface and W6+ content increased in the near-surface layer of samples with tungsten content increasing in catalysts.