Fatty acid hexyl esters: Influence of the reaction parameters on the synthesis and diesel-biodiesel-1-hexanol blend composition on the application properties

The matter of this study is the influence of reaction parameters – temperature (40–80 °C), time (2–60 min), molar ratio of 1-hexanol to waste cooking oil (5:1–12:1), and mass fraction of KOH catalyst (1–3 wt%) – on the synthesis, i.e. reaction conversion, of fatty acid hexyl esters (FAHE). Afterward, larger amounts of biodiesel were synthesized, purified, and blended with 1-hexanol and non-additized mineral diesel, to assess blends’ application properties, as possible transportation fuels used in diesel engines. An increase in biodiesel’s volume fraction up to 20 vol% in blends led to an increase in their densities, viscosities, as well as surface tension values. On the contrary, adding 1-hexanol up to 15 vol% resulted in a decrease in these values. Low-temperature properties of diesel–biodiesel blends, e.g. pour point and cloud point and heat of combustion were the same or very close to those of mineral diesel, whereas FAHE significantly improved lubricating properties of diesel. Altogether, application property values of the prepared blends fell within the corresponding guidelines set by the standard EN 590.