Measurement and modeling of biodiesels surface tensions

S. Freitas1, M. Oliveira1, M. Pratas1 and A. Queimada2

1Centre for Research in Ceramics and Composite Materials (CICECO), Chemistry Department, University of Aveiro, Campus de Santiago, Aveiro, Portugal
2LSRE - Laboratory of Separation and Reaction Engineering, Faculdade de engenharia, Universidade do Porto, Porto, Portugal

Keywords: modeling, CPA EOS
property: surface tensions
material: biodiesel, biodiesel blends

Biodiesel has recently emerged as a reliable alternative to petrodiesel in the contemporary fuel market, as it offers immense benefits regarding resources availability and renewability and also the environmental impact [1-2].

Biodiesel properties, however, must be tuned in order to achieve an optimal fuel performance, increasing its acceptance among consumers.

Surface tension is one of biodiesel physical properties that influence the design of purification processes and the fuel performance. Surface tension also controls the formation of oil drops that determine the fuel atomization on the engine combustion chamber. A higher surface tension disables the formation of small droplets from the liquid fuel [3]. Surface tension is thus a key property to be taken into consideration while designing new injection systems and producing biodiesel [4].

Unfortunately, much less attention has been given to that property when comparing with other biodiesel properties, such as density and viscosity.5 In fact, there are almost no reports in literature about experimental surface tension of biodiesels or fatty acid esters from which biodiesels are comprised. When available, biodiesel surface tension data are limited to one temperature point.

In this work, new experimental measurements were carried out for the temperature dependence of surface tensions of soy, palm and sunflower biodiesels and their binary and ternary mixtures.

Additionally, the combination of the Cubic-Plus-Association equation of state (CPA EoS) with the gradient theory is applied to predict the new experimental data here presented.

  1. Knothe, G. Energy Fuels 2010, 24, 2098.

  2. Anand, K.; Ranjan, A.; Mehta, P. S. Energy Fuels 2009, 24, 664.

  3. Ejim, C. E.; Fleck, B. A.; Amirfazli, A. Fuel, 86, 1534.

  4. Blangino, E.; Riveras, A. F.; Romano, S. D. Physics and Chemistry of Liquids: An International Journal 2008, 46, 527-547

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