# Structural, Densimetric, and Thermal Properties of Biodiesel and Diesel Blends

## TL;DR

This paper studies how mixing biodiesel and diesel affects their physical and thermal properties, revealing non-linear changes due to molecular interactions.

## Contribution

The study reveals non-linear excess phenomena in biodiesel-diesel blends, linked to molecular interactions and liquid cohesion.

## Key findings

- Infrared spectra show shifts in ester absorption bands with biodiesel fraction.
- Densimetric and thermal properties deviate from linear mixing rules.
- Excess phenomena in blends are attributed to secondary chemical bonds and liquid cohesion.

## Abstract

Binary blends of both commercial petrodiesel and biodiesel
were
prepared and characterized at room temperature. Petrodiesel-type ultralow
sulfur with a Sulfur level of 10 ppm/kg called S10 was used, while
biodiesel was a methylic one synthesized via soybean oil and methanol,
with a composition based on a mixture of several molecules-type fatty
acid monoalkyl esters. A set of 10 binary blends containing 0 to 100%
biodiesel were prepared by conventional mixing of volumetric fraction
of components. The structural characterization of blends was carried
out by attenuated total reflection Fourier transform infrared spectroscopy,
ATR-FTIR, in the Mid region. Volumetric properties of the blends were
measured via the pycnometry technique. Thermal conductivity was investigated
via a digital thermal conductivimeter, using a two-needle sensor.
Infrared spectra of all blends exhibited a significant shifting of
the position of the characteristic absorption band of biodiesel, a
specific vibration of the charged head assigned to esters groups.
Values of parameters intensity, area, and specific absorption bands
of diesel and biodiesel and volume of each blend, as well as thermal
conductivity, undergo changes as a function of biodiesel fraction
in the mixture. Evolution of parameters mentioned as a function of
the biodiesel fraction in the blend was assigned to the molecular
interaction between the molecule components of the mixture. In addition,
these values do not obey a linear simple mixture rule. However, the
set of structural, densimetric/volume, and thermal data of binary
blends show the development of Excess phenomena properties that are
associated with liquid cohesion. Based on the secondary chemical bond
concept, the properties of Excess were discussed.