Correlation of Infinite-Dilution Diffusion Coefficients in Supercritical Fluids

Abstract

A correlation based on an extensive literature database was proposed to estimate the infinite-dilution diffusion coefficients in supercritical fluids. The input parameters required for the correlation are temperature, the solute molar mass, the solute density near ambient temperature, the solvent critical temperature, the solvent critical density, and the solvent reduced density. The total average absolute deviation (AAD%) of the prediction is 6.55% for 153 binary systems and 1968 data points over the solvent reduced temperature range of 1.00-1.78, the solvent reduced density range of 0.21-2.34, the solute molar mass range of 58.08-885.40 g/mol, and the solute ambient-temperature density range of 0.63-2.04 g/cm 3 . Introduction of solute density into this new correlation makes it possible to predict with reasonable accuracy the diffusivities in supercritical fluids over a wide solute density range.

Molecular Dynamics Simulation of Diffusion and Structure of Some n-Alkanes in near Critical and Supercritical Carbon Dioxide at Infinite Dilution

“…The diffusion coefficient at high pressures is very important for estimating the separation rate and designing separation processes. However, it is very difficult and expensive to determine diffusion data experimentally because of the rigorous experimental conditions required. − The Taylor dispersion method was applied to determinate diffusion coefficients of various organic compounds in supercritical carbon dioxide (scCO 2 ) and which were correlated with molecular parameters and viscosity of fluids by several empirical equations. − At present, computer simulation has already become one of the most important methods for obtaining diffusion coefficients of fluids. − Moreover, such simulations can provide detailed and valuable characteristic pictures of molecular structure at the atomic level. − …”

Diffusion coefficients and phase equilibria of carbon dioxide–ionic liquid, 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim][PF6]) system

“…Shi-Lu and He-Yu correlations are employed to determine the infinite dilution diffusivity of [bmim][PF 6 ] in carbon dioxide. [52,53] The He-Yu correlation is expressed as follows:…”

Accurate hydrodynamic models for the prediction of tracer diffusivities in supercritical carbon dioxide

“…(2) and (5) combined with Eq. (13) -were fitted to the experimental diffusivities of database (Section 4), but specific constants were additionally optimized for n-alkanes since most equations generally fail to describe this group of molecules [38,51,77,78]. The resulting parameters are compiled in Table 1.…”