Studies On Hydrotreating Of C₁₈ Fatty Acids To Hydrocarbons

The development of alternative fuels from plant-derived oils (such as sunflower,palm, rapeseed, algal oil and their derivates) as a substitute for fossil fuels hasattracted much more attention due to the increased energy demand, environmentalconcerns and the depletion of fossil fuel resources.Hydrotreating of C18fatty acids for biofuel production was investigated withdodecane as solvent in a fixed bed reactor. The effects of temperature, pressure,WHSV and hydrogen to oil ratio on the oxygen removal reactions pathways ofhydrodeoxygenation (HDO), decarbonylation/decarboxylation (DCO/DCO2) as wellas/β-C scission and isomerizaiton reactions to form the C15-C18hydrocarbons weresystemically evaluated. For all experiments the same commercial Ni-W supported onmodified SiO2-Al2O3by NTY zeolite catalyst was used. The hydrotreatingtemperature is the most dominant operating parameter that affects the catalystperformance. The HDO increases with decreasing temperature and/or increasingpressure, while the DCO/DCO2decreases with decreasing temperature and/orincreasing pressure. Low temperature and high WHSV will promote the isomerizationreaction to cause more iso-paraffins in the products. The conversion of C18fatty acidsand/or product yield is little affected by the H2/oil ratio.The concentration of C18fatty acids in dodecane has a significant effect on theconversion of C18fatty acids and C18yield (HDO reaction), which decreases with theconcentration of C18fatty acids. Adsorbed hydrogen to fatty acid ratio has significanteffect on deoxygenation pathways including C-O scission and C-C scission. Shorterchain solvent has positive effect on the conversion and product yields.The effects of two types of additives, the hydrogen donors (condensed aromaticsand hydroxy compounds) and electron donors (nitrogenous compounds), on the C18fatty acids deoxygenation were investigated. Wherein the hydrogen donor, includingcondensed aromatics and hydroxy compounds, have significantly positive effect on theC18fatty acids conversion and product yields. But the effect of electron donors oneither conversion or isomerization is noticeably negative.