Stability, Lubricity, Viscosity, and Cold-Flow Properties of Alcohol-Diesel Blends

Alcohols have an interesting potential as blending components for diesel fuels because of their capacity to reduce soot formation. Because they have increasing routes for their production from renewable sources, they could contribute toward increasing the renewable fraction of these fuels and, therefore, toward reducing the impact of diesel transportation on the global warming effect. To increase the knowledge about the implications of the use of short- and long-chain alcohols/diesel fuel blends in diesel engines, the stability, lubricity, viscosity, and cold filter plugging point (CFPP) have been tested. Blends of methanol, ethanol, propanol, butanol, and pentanol with diesel fuel have been analyzed at 1, 2.5, 7.7, 17, 50, 75, and 90% in volume [including 95% (v/v) in the case of CFPP]. Results have shown that short-chain alcohols depict poor blending stability and low viscosity (mainly for concentrations of ethanol and propanol in diesel fuel blends beyond 22 and 45%, respectively). A synergistic effect was observed in viscosity when moderate concentrations of butanol and pentanol were mixed with diesel fuel. The lubricity of the blends decreases with the alcohol content, but this effect is partially compensated by the alcohol volatility. The blends with the highest restriction of use are those containing pentanol, which should be limited to concentrations below 10% (v/v), because its volatility does not compensate for its lubricating capacity. The use of alcohol/winter diesel fuel blends provides a substantial benefit only when high alcohol concentrations are used. It can be concluded that alcohols can be blended with diesel fuel under low and high concentrations, although to improve the blending stability of short-chain alcohols in medium concentrations, the use of additives or fatty acid esters would be necessary.