posted on 2024-01-09, 09:45authored bySarah Mross, Sebastian Schmitt, Simon Stephan, Kerstin Münnemann, Hans Hasse
Poly(oxymethylene)
dimethyl ethers (OME, CH3O(CH2O)nCH3) are new synthetic
fuels that can be produced from renewable resources. An interesting
application of OME fuels is the use of them in mixtures with hydrogenated
vegetable oils (HVO), which mainly consist of alkanes. Data on diffusion
coefficients of OME containing mixtures are lacking in the literature
but are needed for modeling OME production processes and OME combustion.
Therefore, in the present work, self-diffusion coefficients of binary
mixtures of OME and alkanes were measured by pulsed field gradient
nuclear magnetic resonance (PFG-NMR). OME with chain lengths n = 1...4 were studied; the alkanes were n-dodecane (C12) and n-hexadecane (C16). The measurements
in the binary mixtures were carried out at high dilution of the diffusing
components and extrapolated to obtain the self-diffusion coefficients
at infinite dilution that are identical with the mutual diffusion
coefficient. For completeness, the self-diffusion coefficients of
the pure components were also measured. The experiments were carried
out at temperatures between 298.15 and 353.15 K at ambient pressure.
The experimental data for the diffusion coefficients at infinite dilution
were compared with the results from established prediction methods
(SEGWE and Wilke and Chang), revealing considerable discrepancies.
Furthermore, entropy scaling (ES) was applied here for the first time
for modeling diffusion coefficients at infinite dilution. By coupling
the results from entropy scaling with the Vignes equation, mutual
diffusion coefficients in mixtures of OME and alkanes can now be predicted
as a function of temperature, pressure, and composition for a wide
range of conditions.