Characterization of Hydroprocessed Used Cooking Oils as High Cetane Number Blending Component for Automotive Diesel

Renewable substitutes for transportation fuels have had an important role in the recent years. Hydrotreated vegetable oils (HVO) are produced from two stage hydrotreating process of vegetable oils. The second stage of this hydroteating process is used to convert normal paraffins to isoparaffins in order to improve cold flow properties of these fuels. As this stage is a high energy consuming process, it is of interest to investigate the characteristics and the usability of the first stage of hydrotreatment of lipids. This paper examines the properties of alternative fuel derived from the hydrotreatment of used cooking oil (UCO). Used cooking oil is a difficult feedstock for biodiesel production. The hydrotreating of UCO converts triglycerides mainly into normal paraffins within the diesel fuel range. The hydrotreated UCO (HUCO) has an excellent cetane number and cetane index (>90), but very poor cold flow properties. As the amount of the produced HUCO is limited, the main idea is to use it in blends with petroleum diesel fuel. For this reason, the HUCO was blended with ultra-low diesel fuel (ULSD) and low cetane number high aromatic middle distillate. The results showed that ternary blends of these fuels can produce fuel that meets the specifications set by EN 590 standard, mainly summer grade fuel, as the poor cold flow properties of the HUCO affect negatively the cold flow properties of the blend. The lubricity of the HUCO does not meet EN 590 standards, but the blends have improved lubricating characteristics, within specification limits.