abstract
The tracer diffusion coefficients, D-12, of solutes in supercritical carbon dioxide (SC-CO2), modified or not with cosolvents, are necessary for industrial and research applications. In this study, the determination and analysis of D-12 values of chromium(III) acetylacetonate in SC-CO2 are presented. The measurements were carried out by the chromatographic impulse response (CIR) method from 308.15 to 333.15 K at pressures from 125 to 250 bar, and yield diffusivities between 0.570 x 10(-4) and 1.529 x 10(-4)cm(2) . s(-1) The experimental trends of D-12 with temperature, pressure, density, and Stokes-Einstein coordinates are also presented. Eleven equations were evaluated for modeling the new data, and the best results were achieved using the semi-empirical correlations of Magalhaes et al. (error of 1.95% and 1.90%), the universal model of Lito et al. (2.01%), and the predictive modified Stokes-Einstein equation (3.16%) and Vaz et al. expression (3.27%). Finally, a comparison between the diffusivities of this work and those reported in the literature for other metal acetylacetonates (Co(acac)(3), Cr(acac)(3), Pd(acac)(2) and Pt(acac)(2)) was accomplished, being possible to conclude that the correct interpretation of the diffusive phenomenon of these systems requires not only the molecular weight but also solute diameter. (C) 2016 Elsevier B.V. All rights reserved.
keywords
CARBON-DIOXIDE; INFINITE-DILUTION; FLUID CHROMATOGRAPHY; TAYLOR DISPERSION; PRESSURE RANGE; LENNARD-JONES; DENSE FLUIDS; WIDE RANGES; COEFFICIENTS; LIQUID
subject category
Chemistry; Engineering
authors
Cordeiro, J; Magalhaes, AL; Valente, AA; Silva, CM
our authors
Ana Luísa Carvalho Magalhães
Post-doc Fellowship
Anabela Tavares Aguiar Valente
Principal Researcher
Carlos Manuel Silva
Associate Professor
Joana Duarte Cordeiro
MSc Studentacknowledgements
A.L. Magalhaes acknowledges a Post-doc grant provided by Fundacao para a Ciencia e a Tecnologia, Portugal (SFRH/BPD/95393/2013). This work was developed in the scope of the project CICECO-Aveiro Institute of Materials (Ref. FCTUID/CTM/50011/2013), financed by national funds through the FCT/MEC and when applicable co-financed by FEDER under the PT2020 Partnership Agreement.