Biodiesel as an additive for diesel-ethanol (diesohol) blend: physical-chemical parameters and origin of the fuels’ miscibility

Abstract

Diesohol, mixtures of diesel (D) – ethanol (E) are an important alternative for diesel substitution. However, there is a critical challenge: the miscibility of the fuels’ portion. In this sense, this article discusses the impact of biodiesel (B) as an additive on the stabilization of diesel-ethanol blend by molecular interaction studies. The findings were achieved experimentally by measuring the density, ultrasonic velocity, viscosity and surface tension and is further refined from the elucidation of few related thermo-acoustical parameters. Obtained results suggest that the stability has been enhanced through dispersive interactions and blend ratios such as D-80% + B-15% + E-5% is found to have similar molecular association compared to diesel. These conclusions as obtained by experiment are confirmed by theoretical predictions made by molecular dynamics (MD) simulation studies. The MD coupled to minimum-distance distribution functions (gmd(r)) showed an accumulation of diesel close to biodiesel at ~2.2 Å, and suggest an important interaction of ethanol with diesel carbazole molecules and methyl esters via hydrogen bonds. Further the simulation results show that the esters may act as a “bridge” promoting the dispersion of ethanol molecules into diesel solution.