abstract
The tracer diffusion coefficients, D-12, are fundamental properties for the design and simulation of rate-controlled processes. Nowadays, under the scope of the biorefinery concept and strict environmental legislation, the D-12 values are increasingly necessary for extractions, reactions, and chromatographic separations carried out at supercritical conditions, particularly using carbon dioxide. Hence, the main objective of this work is the development of accurate and simple models for the pure prediction of D-12 values in supercritical CO2. Two modified Stokes-Einstein equations (mSE(1) and mSE(2)) are proposed and validated using a large database comprehending extremely distinct molecules in terms of size, molecular weight, polarity and sphericity. The global deviations achieved by the mSE1 (Eqs. (2) and (13)) and mSE(2) (Eqs. (5), (13), (3), (4)) models are only 6.38% and 6.75%, respectively, in contrast to the significant errors provided by well known predictive correlations available in the literature: Wilke-Chang, 12.17%; Tyn-Calus, 17.01%; Scheibel, 19.04%; Lusis-Ratcliff, 27.32%; Reddy-Doraiswamy, 79.34%; Lai-Tan, 25.82%. Furthermore, the minimum and maximum deviations achieved by the new models are much smaller than those of the reference equations adopted for comparison. In conclusion, our mSE(1) and mSE(2) models can be recommended for the prediction of tracer diffusivities in supercritical CO2. (C) 2013 Elsevier B.V. All rights reserved.
keywords
BINARY DIFFUSION-COEFFICIENTS; SIMULATED MOVING-BED; FLUID CHROMATOGRAPHY SFC; IMPULSE-RESPONSE METHOD; TAYLOR DISPERSION TECHNIQUE; PARTIAL MOLAR VOLUMES; LENNARD-JONES FLUID; ACID METHYL-ESTERS; HARD-SPHERE THEORY; INFINITE-DILUTION
subject category
Chemistry; Engineering
authors
Magalhaes, AL; Vaz, RV; Goncalves, RMG; Da Silva, FA; Silva, CM
our authors
Ana Luísa Carvalho Magalhães
Post-doc Fellowship
Carlos Manuel Silva
Associate Professor
Francisco Avelino Silva Freitas
Assistant Professor
Graça Raquel Veiga Vaz
PhD Student
Projects
acknowledgements
A.L. Magalhaes and R.V. Vaz thank the PhD grants provided by Fundacao para a Ciencia e a Tecnologia (SFRH/BD/46776/2008 and SFRH/BD/69257/2010). Authors thank European Community's Seventh Framework Programme FP7/2007-2013 under grant agreement No CP-IP 228589-2 AFORE, and programme PEst-C/CTM/LA0011/2013 (CICECO).