FTIR as a Powerful Tool for Measurements of Diffusion in Supercritical Carbon Dioxide Using Taylor Dispersion Method

Santos, Cecília I.A.V.; Barros, Marisa C.F.; Faro, Maria P. R. T.; Shevtsova, Valentina; Ribeiro, Ana C.F.

doi:10.3390/pr10081528

Cited by 3 publications

(6 citation statements)

References 60 publications

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“…The Taylor dispersion technique (TDT) here employed has been optimized for the measurement of high pressure and supercritical fluids [ 19 , 45 ], namely scCO 2 , and is represented in Figure 4 . It operates upon the fundamental basis of TDT: a pulse of a solute that is injected into a solvent stream, flowing under a laminar regime through a circular cross section capillary tube, will widen due to the joint action of convection occurring in the longitudinal axis and molecular diffusion occurring in the radial direction.…”

Section: Methodsmentioning

confidence: 99%

“…It is coiled on a channeled aluminum cylinder in the form of a helix with 0.36 m diameter for both support and temperature regulation and kept at the study temperature ±0.1 K using a temperature-regulated water bath (Grant GD100, Grant Instruments Keison, Chelmsford, UK). Dispersion of the injected samples is monitored using a FT-IR refractometer (Jasco FT-IR 4600, Jasco Inc.), placed at the outlet of the dispersion tube and equipped with a high-pressure demountable cell (Harrick, Pleasantville, NY, USA), optimized for the best possible signal-to-noise ratio [ 45 ]. The detector is connected to a computer for digital data acquisition (Spectra Manager v.2 software by Jasco) allowing it to follow the response curves corresponding to the changes in the stream with time and in terms of absorbance/transmittance infrared spectra at wavenumbers corresponding to the different vibration modes of the molecules studied here.…”

Section: Methodsmentioning

confidence: 99%

“…Calculation of the diffusion coefficients from the absorbance–response curve of the solute is performed using the same procedure described for conventional TDT [ 19 , 45 , 47 , 48 , 49 ], with the assumption that small changes in concentration C are directly proportional to variations in absorbance. Diffusion coefficients are extracted from the experimentally measured signal by fitting the response curve to:

where the three first terms A 0 + A 1 t + A 2 t 2 reflect the drift and curvature of the baseline due to small concentration and temperature variations; t R is the retention time of the peak, R = (∂A/∂C)λ is the sensitivity of the detector (directly dependent on the wavenumber at which the measurements are carried out) and Δ A is the peak height relative to the baseline.…”

Section: Methodsmentioning

confidence: 99%

“…The procedure to select the working wavenumbers for each solute and the experimental protocol have been explained in detail previously [ 19 , 45 ], so only the most relevant points are mentioned below.…”

Section: Methodsmentioning

confidence: 99%

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Binary Diffusion Coefficients for Short Chain Alcohols in Supercritical Carbon Dioxide—Experimental and Predictive Correlations

2023

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Experimental binary diffusion coefficients for short-chain alcohols in supercritical carbon dioxide were measured using the Taylor dispersion technique in a temperature range of 306.15 K to 331.15 K and along the 10.5 MPa isobar. The obtained diffusion coefficients were in the order of 10−8 m2 s−1. The dependence of D on temperature and solvent density was examined together with the influence of molecular size. Some classic correlation models based on the hydrodynamic and free volume theory were used to estimate the diffusion coefficients in supercritical carbon dioxide. Predicted values were generally overestimated in comparison with experimental ones and correlations were shown to be valid only in high-density regions.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Binary Diffusion Coefficients for Short Chain Alcohols in Supercritical Carbon Dioxide—Experimental and Predictive Correlations

2023

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“…The temperature, pressure and composition dependencies of the Fick diffusion coefficient remain largely unexplored over a wide range of thermodynamic conditions 22 . Experimental studies on mixtures with benzene 12 , 18 , 23 – 32 , toluene 5 , 13 , 25 , 26 , 32 , 33 or naphthalene 12 , 18 , 34 – 41 at high pressure (see Table 1 ) have provided valuable insights into the Fick diffusion coefficient, revealing a peculiar behavior in certain near-critical regions 28 , 30 , 42 , a significant dependence on the molecular mass of the solute 7 , 14 , 24 , 43 and deviations from the conventional Stokes–Einstein behavior 7 , 22 , 31 , 44 – 46 .…”

Section: Introductionmentioning

confidence: 99%

Diffusion of hydrocarbons diluted in supercritical carbon dioxide

Saric,

Guevara-Carrion,

Gaponenko

et al. 2023

Sci Rep

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Mutual diffusion of six hydrocarbons (methane, ethane, isobutane, benzene, toluene or naphthalene) diluted in supercritical carbon dioxide ($${\hbox {CO}}_{2}$$ CO 2 ) is studied by molecular dynamics simulation near the Widom line, i.e., in the temperature range from 290 to 345 K along the isobar 9 MPa. The $${\hbox {CO}}_{2}$$ CO 2 + aromatics mixtures are additionally sampled at 10 and 12 MPa and an experimental database with Fick diffusion coefficient data for those systems is provided. Taylor dispersion experiments of $${\hbox {CO}}_{2}$$ CO 2 with benzene, toluene, n-dodecane and 1,2,3,4-tetrahydronaphthalene are conducted along the $$p =$$ p = 10 MPa isobar. Maxwell–Stefan and Fick diffusion coefficients are analyzed, together with the thermodynamic factor that relates them. It is found that the peculiar behavior of the Fick diffusion coefficient of some $${\hbox {CO}}_{2}$$ CO 2 mixtures in the extended critical region is a consequence of the thermodynamic factor minimum due to pronounced clustering on the molecular scale. Further, the strong dependence of the Fick diffusion coefficient on the molecular mass of the solute as well as the breakdown of the Stokes–Einstein relation near the Widom line are confirmed. Eleven correlations for the prediction of the Fick diffusion coefficient of $${\hbox {CO}}_{2}$$ CO 2 mixtures are assessed. An alternative two-step approach for the prediction of the infinite dilution Fick diffusion coefficient of supercritical $${\hbox {CO}}_{2}$$ CO 2 mixtures is proposed. It requires only the state point in terms of temperature and pressure (or density) as well as the molecular solute mass as input parameters. First, entropy scaling is applied to estimate the self-diffusion coefficient of $${\hbox {CO}}_{2}$$ CO 2 . Subsequently, this coefficient is used to determine the infinite dilution Fick diffusion coefficient of the mixture, based on the finding that these two diffusion coefficients exhibit a linear relationship, where the slope depends only on the molecular solute mass.

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Diffusion of Ethanol in Supercritical Carbon Dioxide—Investigation of scCO2-Cosolvent Mixtures Used in Pharmaceutical Applications

2022

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Diffusion coefficients, D, for ethanol in supercritical carbon dioxide (scCO2) were measured in the temperature range 306.15–331.15 K and along the 10.5 MPa isobar, using the Taylor dispersion technique. The obtained diffusivities ranged from 1.49 × 10−8 to 2.98 × 10−8 m2 s−1, an order of magnitude higher than in usual liquids. The dependence of D on temperature and solvent density was examined. Various correlation models based in the hydrodynamic theory were assessed to estimate the diffusion coefficients, with reasonable results obtained for the Wilke–Chang and Lai–Tan models.

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FTIR as a Powerful Tool for Measurements of Diffusion in Supercritical Carbon Dioxide Using Taylor Dispersion Method

Cited by 3 publications

References 60 publications

Binary Diffusion Coefficients for Short Chain Alcohols in Supercritical Carbon Dioxide—Experimental and Predictive Correlations

Binary Diffusion Coefficients for Short Chain Alcohols in Supercritical Carbon Dioxide—Experimental and Predictive Correlations

Diffusion of hydrocarbons diluted in supercritical carbon dioxide

Diffusion of Ethanol in Supercritical Carbon Dioxide—Investigation of scCO2-Cosolvent Mixtures Used in Pharmaceutical Applications

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