Surfactant assisted upgrading fuel properties of waste cooking oil biodiesel

Biodiesel from waste cooking oil has drawbacks such as poor cold flow properties and low oxidation stability. Cold flow properties and ignition delay of biodiesel assessed by thermogravimetric methods were improved in the present study by formation of water-in-biodiesel microemulsions with the assistant of different surfactants. More interestingly, Span 80 based microemulsion experienced precipitation (phase separation) during the storage at 4 degrees C in 60 days. But this separation was not a de emulsification but a purification process. The total fatty acid methyl esters content in purified biodiesel was increased considerably (from 90.2% to 963%) with cold flow properties and oxidation stability being also improved. Both the purification and addition of Span 80 (the formation of microemulsion) contributed to the improved cold flow properties and oxidation stability of biodiesel. The overall fuel properties of biodiesel after microemulsification-purification were close to those of biodiesel/diesel (V/V, 5/5) blend. Note that emulsion/microemulsion fuel also has great potential to reduce NOx emission during combustion in diesel engine, application of Span 80 for biodiesel purification may be further developed as a promising biodiesel upgrading technology. (C) 2018 Elsevier Ltd. All rights reserved.