Effects of different alcohols additives on solubility of hydrous ethanol/diesel fuel blends

The purpose of this study was to evaluate effects of different alcohols on the solubility of the blends between diesel and hydrous ethanol (with 10 vol.% water) at various temperatures of 5, 15, and 30 °C. Among these alcohols, n-butanol, n-hexanol, n-octanol and n-dodecanol were selected for investigating the influence of alcohol chain length on solubility, while the effect of straight and branched chain on solubility was studied via comparing with four isomers of butanol (n-butanol, 2-butanol, iso-butanol and tert-butanol). Additionally, effects of various functional groups including both hydroxy and ketone group were studied by using cyclohexanol and cyclohexanone. The blend on hydrous ethanol (10 vol.% water) and diesel fuel was acted as an analyte with different diesel blending ratios varied from 0 to 100 vol.% in 10 vol.% increments. Then the given alcohol (titrant) was gradually added into the centrifuge tube by a high-precision pipette until phase boundaries of ternary system appeared. Results show that alcohols with higher carbon numbers provide a better inter-soluble capacity, but a higher carbon-number alcohol such as n-dodecanol correlates with a lower pour point which leads to the gelling for the blends. Based on the performance of 6-carbon alcohols on phase stability, it is clearly that the straight chain structure and hydroxy group shows a better hydrotropy than cyclic structure and ketone group, respectively. For butanol isomers, straight chain butanols have better soluble capacity than that of branched structures. Taking these factors into account, n-hexanol and n-octanol can be recommended as a co-solvent additive for hydrous ethanol/diesel system due to the acceptable fuel properties and soluble performance.