Hydrotreating of C-18 fatty acids for biofuel production was investigated with dodecane as solvent in a fixed bed reactor. The effects of temperature (300 degrees C-375 degrees C), pressure (2 MPa-8 MPa), WHSV (4 h(-1)-18 h(-1)) and hydrogen to oil ratio (500 NmL/mL-1000 NmL/mL) on the oxygen removal reaction pathways of hydrodeoxygenation (HDO), decarbonylation/decarboxylation (DCO/DCO2) as well as alpha/beta-C scission and isomerization reactions to form the C-15-C-18 hydrocarbons were systemically evaluated. For all experiments the same commercial Ni-W supported on modified SiO2-Al2O3 by NTY zeolite catalyst was used. The hydrotreating temperature is the most dominant operating parameter that affects the catalyst performance. The HDO to DCO/DCO2 ratio increases with decreasing temperature and/or increasing pressure. Low temperature and high WHSV will promote the isomerization reaction to cause more iso-paraffins in the products. The conversion of C-18 fatty acids and/or product yield is little affected by the H-2/oil ratio. Moreover, the concentration of C-18 fatty acids in dodecane has a significant effect on the conversion of C-18 fatty acids and C-18 yield (HDO reaction), which decreases with the concentration of C-18 fatty acids. Adsorbed hydrogen to fatty acid ratio has significant effect on deoxygenation pathways including C-O scission and C-C scission. (C) 2013 Elsevier B.V. All rights reserved.