Hydrotreating of C18 fatty acids to hydrocarbons on sulphided NiW/SiO2–Al2O3

Hydrotreating of C18 fatty acids for biofuel production was investigated with dodecane as solvent in a fixed bed reactor. The effects of temperature (300 °C–375 °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 α/β-C scission and isomerization reactions to form the C15–C18 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 C18 fatty acids and/or product yield is little affected by the H2/oil ratio. Moreover, the concentration of C18 fatty acids in dodecane has a significant effect on the conversion of C18 fatty acids and C18 yield (HDO reaction), which decreases with the concentration of C18 fatty acids. Adsorbed hydrogen to fatty acid ratio has significant effect on deoxygenation pathways including C–O scission and C–C scission.