Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 23Citation - Scopus: 29Dynamic Nature of Supercritical Co2 Adsorption on Coals(Springer Verlag, 2017) Özdemir, EkremAdsorption on non-rigid solids was shown to be a dynamic process. Excess adsorption and desorption isotherms of CO2 on eight Argonne Premium coal samples were measured at 55 °C and pressures up to 14 MPa by manometric method. The excess adsorption isotherms of CO2 on powdered coals showed almost Langmuir-like to rectilinear shape behavior at low pressures up to 9 MPa, and it increased noticeably at pressures higher than 9 MPa. There was a significant hysteresis between the excess adsorption and desorption isotherms for each rank of coals, which was related to the volumetric uncertainties occurring during the adsorption isotherm measurements. The parameters related to the adsorption capacity and micro porous characteristics of the coal were obtained at different pressure ranges by fitting the experimental data to the modified Dubinin-Astakhov (D-A) equation at the increasingly larger pressure ranges, using only the first 4 data points of the excess adsorption isotherm initially, and progressively using additional data points for the subsequent values. It was shown that the curve fit parameters vary with pressure, and therefore, concluded that the adsorption on non-rigid solids such as CO2 on coal is indeed a dynamic process. It was suggested that new adsorption isotherm equations need to be developed considering the dynamic nature of the adsorption on solid adsorbents.Article Citation - WoS: 5Citation - Scopus: 5Solvent Sorption in a Polymer-Solvent System - Importance of Swelling and Heat Effects(Elsevier Ltd., 2006) Alsoy Altınkaya, Sacide; Ramesh, Narayan; Duda, John LarrySorption experiments are often conducted in gravimetric sorption columns where several deviations from ideal conditions could potentially occur. For example, heat effects due to solvent sorption, errors introduced due to concentration dependent diffusion coefficients and swelling are unavoidable. In this study, we develop a model to study the importance of the combination of these effects in obtaining diffusion coefficients from sorption experiments. The model is used to explore a wide range of operating conditions and physical parameters.Article Citation - WoS: 2Citation - Scopus: 1Errors Associated With Swelling in the Analysis of Polymer-Solvent Diffusion Measurements(Elsevier Ltd., 2005) Alsoy Altınkaya, SacideSorption curves are generated from a mathematical model which includes the influence of the polymer swelling for unsteady-state sorption of a vapor or liquid by a polymer. To investigate the simultaneous effects of the specific volumes of the polymer-penetrant pair and the difference between the final and initial equilibrium concentrations on the sorption curves, statistical experimental design approach is used. Simulation results obtained from the numerical solution of model equations are utilized to estimate the error that would occur if one simply evaluates the diffusion coefficient using the traditional formulas derived from the analytical solution of the sorption equation. An empirical expression is developed that describes the effects of the difference between the final and initial equilibrium concentrations and the specific volumes of the polymer and the penetrant on the magnitude of error in diffusivity associated with the use of one of these traditional formulas so called the initial slope method. The predictive ability of the regression model is tested by performing additional simulations not used in the regression analysis.Article Citation - WoS: 26Citation - Scopus: 28Influence of Swelling and Diffusion-Induced Convection on Polymer Sorption Processes(John Wiley and Sons Inc., 2002) Alsoy Altınkaya, Sacide; Duda, John LarryUnsteady-state sorption of a vapor or liquid by a polymer is modeled to include the influence of the moving phase boundary associated with the polymer swelling and diffusion-induced convection. A formulation presented clearly elucidates the influence of these two effects on the overall sorption process. Numerical solutions of the model equations indicate the errors that can be induced when swelling or convection are neglected. For most polymer-solvent systems, the influence of the diffusion-induced convection associated with volume changes in mixing can be neglected in the analysis of sorption processes. In contrast, the correction for the moving boundary or swelling of the polymer phase can be quite significant, particularly when a large step change in solvent concentration is considered.Article Citation - WoS: 24Citation - Scopus: 25Processing of Polymers With Supercritical Fluids(John Wiley and Sons Inc., 1999) Alsoy Altınkaya, Sacide; Duda, John LarryThe removal of impurities, such as residual solvents, unreacted monomers, catalysts, and side-reaction products from polymers represents an important step in polymer processing. Conventional devolatilization techniques for the purification of polymers have limited effectiveness. Devolatilization with supercritical fluids, however, can enhance impurity removal by increasing the thermodynamic driving force and molecular diffusivity.