کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
156062 456920 2011 12 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Experimental validation of physico-chemical models of effective diffusion in chromatographic columns packed with superficially porous particles
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی مهندسی شیمی (عمومی)
پیش نمایش صفحه اول مقاله
Experimental validation of physico-chemical models of effective diffusion in chromatographic columns packed with superficially porous particles
چکیده انگلیسی

The effective diffusion coefficient of a non-retained compound (uracil) was measured with the peak parking (PP) method for two series (4.6 mm×100 mm and 2.1 mm×100 mm) of six replicate columns packed with the same batch of superficially porous 2.6μm Kinetex-C18 particles. The abilities of four different models of effective diffusion in packed beds to account for the experimental data are compared. These models include the conventional Knox time-averaged model, the extension to molecular diffusion of the Landauer electrical conductance model, the Garnett diffusion model for the inclusion of core-shell spheres down to infinitesimal small sizes, and the stochastic Torquato model for a random dispersion of spheres in contact.The choice of a non-retained compound for this purpose is justified by the facts that the diffusivity of this compound through the porous shell can be estimated independently from its internal porosity derived from inverse size-exclusion chromatography (ISEC) data, that the internal obstruction factor can be assessed by nuclear magnetic resonance (NMR) using the spin-echo pulsed field-gradient method, and that the hindrance diffusion factor can be estimated with either the Renkin or the Brenner correlations. The experimental effective diffusion coefficient of uracil was found to be in excellent agreement with the value predicted by Knox semi-empirical model, in good agreement with those predicted by Torquato and Landauer models while the Garnett model failed definitely. In conclusion, the longitudinal diffusion terms of columns packed with core-shell particles cannot yet be accurately predicted by any of the sophisticated, physically relevant models of effective diffusion actually available in the scientific literature.


► We attempted to validate the available models of diffusion through heterogeneous media.
► The media studied consist in superficially porous or shell particles in a percolated bed.
► A non-retained compound was used because its diffusivity through the bed can be measured exactly.
► Experimental data agree well with the predictions of the Knox, Torquato, and Landauer models.
► They do not agree with the prediction of the Garnett model.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Chemical Engineering Science - Volume 66, Issue 23, 1 December 2011, Pages 6168–6179
نویسندگان
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