Abstract The selectivity of adsorption of a component of a binary or a ternary gas mixture can be... more Abstract The selectivity of adsorption of a component of a binary or a ternary gas mixture can be a complex function of equilibrium gas phase pressure, temperature and composition and it must be experimentally measured for reliable design of adsorptive gas separation processes. The results of a literature search (1995–2015) using the search engine ‘Web of Science’ for experimental data on binary and ternary gas adsorption selectivity and their estimation from the corresponding pure gas adsorption isotherms by Ideal Adsorbed Solution Theory (IAST) are summarized. The published data cover a large range of equilibrium gas phase conditions and adsorption systems having different adsorbate (molecular size, polarity) and adsorbent (energetic heterogeneity, polarity) properties. The estimation of selectivity by IAST vis a vis the experimental data was good to reasonable for certain systems, while the deviation was large for others. Potential reasons for such observations are discussed.
ABSTRACT Three analytical adsorption isotherm models for energetically homogeneous (Langmuir) and... more ABSTRACT Three analytical adsorption isotherm models for energetically homogeneous (Langmuir) and heterogeneous (Toth, Sircar) adsorbents were tested for describing recently measured pure gas isotherm data for adsorption of N-2 and O-2 on pelletized LiLSX zeolite at three different temperatures and in the pressure range of 0-6 atm. Estimated binary gas isotherms for this system by these models and the Ideal Adsorbed Solution Theory (IAST) were compared with the corresponding experimental data. All three models describe the pure gas isotherms reasonably well, but the model that accounts for the differences in the degrees of adsorbent heterogeneity of the components of a mixture (Sircar) provided better correlation between experimental and estimated binary selectivities than the other models and LAST under various conditions of pressure, temperature, and gas composition. Predictions of multicomponent isotherm data by models must be extensively tested experimentally, since their ability to describe pure gas isotherms does not guarantee the quality of multicomponent isotherm predictions.
ABSTRACT New experimental data are reported for equilibrium adsorption isotherm and mass transfer... more ABSTRACT New experimental data are reported for equilibrium adsorption isotherm and mass transfer of pure argon on a sample of pelletized LiLSX zeolite. Model analysis of the data indicate that the zeolite behaved like a nearly homogeneous adsorbent for Ar adsorption while it exhibited substantial heterogeneity for adsorption of N2 and milder heterogeneity for adsorption of O2. The over-all mass transfer coefficient for Ar adsorption was comparable in magnitude with those of N2 and O2. The coefficient increased with increasing pressure and decreased with increasing temperature like those for N2 and O2. A large skin resistance at the adsorbent particle surface was observed for Ar mass transfer like that for adsorption of O2 and N2.
ABSTRACT An isothermal–isobaric column dynamic test apparatus was built to measure equilibrium ad... more ABSTRACT An isothermal–isobaric column dynamic test apparatus was built to measure equilibrium adsorption isotherms of pure N2 and O2 and their binary mixtures at 0, 30, and 65 °C in the pressure range of 0–6 atm on LiLSX zeolite. The data successfully passed an integral and a differential thermodynamic consistency test between pure and binary gas isotherms. The binary selectivities of N2 over O2 were functions of the gas-phase mole fraction and pressure, and the pure gas isosteric heats of adsorption decreased with increased loadings. Thus, the adsorbent was energetically heterogeneous for both gases. The degree of heterogeneity for N2 was larger than that for O2.
ABSTRACT Three analytical adsorption isotherm models for energetically homogeneous (Langmuir) and... more ABSTRACT Three analytical adsorption isotherm models for energetically homogeneous (Langmuir) and heterogeneous (Toth, Sircar) adsorbents were tested for describing recently measured pure gas isotherm data for adsorption of N-2 and O-2 on pelletized LiLSX zeolite at three different temperatures and in the pressure range of 0-6 atm. Estimated binary gas isotherms for this system by these models and the Ideal Adsorbed Solution Theory (IAST) were compared with the corresponding experimental data. All three models describe the pure gas isotherms reasonably well, but the model that accounts for the differences in the degrees of adsorbent heterogeneity of the components of a mixture (Sircar) provided better correlation between experimental and estimated binary selectivities than the other models and LAST under various conditions of pressure, temperature, and gas composition. Predictions of multicomponent isotherm data by models must be extensively tested experimentally, since their ability to describe pure gas isotherms does not guarantee the quality of multicomponent isotherm predictions.
ABSTRACT The performances of a novel rapid pressure swing adsorption system for continuous produc... more ABSTRACT The performances of a novel rapid pressure swing adsorption system for continuous production of ~ 90% O2 from a compressed air feed were experimentally studied using two different samples of pelletized LiLSX zeolite. Bed size factor (BSF) and O2 recovery (R) were compared as functions of total process cycle times. The optimum performance by the samples differed substantially - one exhibiting ~ 30 % smaller BSF and ~ 6 % higher R than the other, even though the adsorption isotherms and column dynamics for the pure gases were nearly identical. Column pressure drop during the desorption step was the cause.
ABSTRACT An isothermal–isobaric column dynamic test apparatus was built to measure equilibrium ad... more ABSTRACT An isothermal–isobaric column dynamic test apparatus was built to measure equilibrium adsorption isotherms of pure N2 and O2 and their binary mixtures at 0, 30, and 65 °C in the pressure range of 0–6 atm on LiLSX zeolite. The data successfully passed an integral and a differential thermodynamic consistency test between pure and binary gas isotherms. The binary selectivities of N2 over O2 were functions of the gas-phase mole fraction and pressure, and the pure gas isosteric heats of adsorption decreased with increased loadings. Thus, the adsorbent was energetically heterogeneous for both gases. The degree of heterogeneity for N2 was larger than that for O2.
ABSTRACT New experimental data are reported for equilibrium adsorption isotherm and mass transfer... more ABSTRACT New experimental data are reported for equilibrium adsorption isotherm and mass transfer of pure argon on a sample of pelletized LiLSX zeolite. Model analysis of the data indicate that the zeolite behaved like a nearly homogeneous adsorbent for Ar adsorption while it exhibited substantial heterogeneity for adsorption of N2 and milder heterogeneity for adsorption of O2. The over-all mass transfer coefficient for Ar adsorption was comparable in magnitude with those of N2 and O2. The coefficient increased with increasing pressure and decreased with increasing temperature like those for N2 and O2. A large skin resistance at the adsorbent particle surface was observed for Ar mass transfer like that for adsorption of O2 and N2.
Abstract The selectivity of adsorption of a component of a binary or a ternary gas mixture can be... more Abstract The selectivity of adsorption of a component of a binary or a ternary gas mixture can be a complex function of equilibrium gas phase pressure, temperature and composition and it must be experimentally measured for reliable design of adsorptive gas separation processes. The results of a literature search (1995–2015) using the search engine ‘Web of Science’ for experimental data on binary and ternary gas adsorption selectivity and their estimation from the corresponding pure gas adsorption isotherms by Ideal Adsorbed Solution Theory (IAST) are summarized. The published data cover a large range of equilibrium gas phase conditions and adsorption systems having different adsorbate (molecular size, polarity) and adsorbent (energetic heterogeneity, polarity) properties. The estimation of selectivity by IAST vis a vis the experimental data was good to reasonable for certain systems, while the deviation was large for others. Potential reasons for such observations are discussed.
ABSTRACT Three analytical adsorption isotherm models for energetically homogeneous (Langmuir) and... more ABSTRACT Three analytical adsorption isotherm models for energetically homogeneous (Langmuir) and heterogeneous (Toth, Sircar) adsorbents were tested for describing recently measured pure gas isotherm data for adsorption of N-2 and O-2 on pelletized LiLSX zeolite at three different temperatures and in the pressure range of 0-6 atm. Estimated binary gas isotherms for this system by these models and the Ideal Adsorbed Solution Theory (IAST) were compared with the corresponding experimental data. All three models describe the pure gas isotherms reasonably well, but the model that accounts for the differences in the degrees of adsorbent heterogeneity of the components of a mixture (Sircar) provided better correlation between experimental and estimated binary selectivities than the other models and LAST under various conditions of pressure, temperature, and gas composition. Predictions of multicomponent isotherm data by models must be extensively tested experimentally, since their ability to describe pure gas isotherms does not guarantee the quality of multicomponent isotherm predictions.
ABSTRACT New experimental data are reported for equilibrium adsorption isotherm and mass transfer... more ABSTRACT New experimental data are reported for equilibrium adsorption isotherm and mass transfer of pure argon on a sample of pelletized LiLSX zeolite. Model analysis of the data indicate that the zeolite behaved like a nearly homogeneous adsorbent for Ar adsorption while it exhibited substantial heterogeneity for adsorption of N2 and milder heterogeneity for adsorption of O2. The over-all mass transfer coefficient for Ar adsorption was comparable in magnitude with those of N2 and O2. The coefficient increased with increasing pressure and decreased with increasing temperature like those for N2 and O2. A large skin resistance at the adsorbent particle surface was observed for Ar mass transfer like that for adsorption of O2 and N2.
ABSTRACT An isothermal–isobaric column dynamic test apparatus was built to measure equilibrium ad... more ABSTRACT An isothermal–isobaric column dynamic test apparatus was built to measure equilibrium adsorption isotherms of pure N2 and O2 and their binary mixtures at 0, 30, and 65 °C in the pressure range of 0–6 atm on LiLSX zeolite. The data successfully passed an integral and a differential thermodynamic consistency test between pure and binary gas isotherms. The binary selectivities of N2 over O2 were functions of the gas-phase mole fraction and pressure, and the pure gas isosteric heats of adsorption decreased with increased loadings. Thus, the adsorbent was energetically heterogeneous for both gases. The degree of heterogeneity for N2 was larger than that for O2.
ABSTRACT Three analytical adsorption isotherm models for energetically homogeneous (Langmuir) and... more ABSTRACT Three analytical adsorption isotherm models for energetically homogeneous (Langmuir) and heterogeneous (Toth, Sircar) adsorbents were tested for describing recently measured pure gas isotherm data for adsorption of N-2 and O-2 on pelletized LiLSX zeolite at three different temperatures and in the pressure range of 0-6 atm. Estimated binary gas isotherms for this system by these models and the Ideal Adsorbed Solution Theory (IAST) were compared with the corresponding experimental data. All three models describe the pure gas isotherms reasonably well, but the model that accounts for the differences in the degrees of adsorbent heterogeneity of the components of a mixture (Sircar) provided better correlation between experimental and estimated binary selectivities than the other models and LAST under various conditions of pressure, temperature, and gas composition. Predictions of multicomponent isotherm data by models must be extensively tested experimentally, since their ability to describe pure gas isotherms does not guarantee the quality of multicomponent isotherm predictions.
ABSTRACT The performances of a novel rapid pressure swing adsorption system for continuous produc... more ABSTRACT The performances of a novel rapid pressure swing adsorption system for continuous production of ~ 90% O2 from a compressed air feed were experimentally studied using two different samples of pelletized LiLSX zeolite. Bed size factor (BSF) and O2 recovery (R) were compared as functions of total process cycle times. The optimum performance by the samples differed substantially - one exhibiting ~ 30 % smaller BSF and ~ 6 % higher R than the other, even though the adsorption isotherms and column dynamics for the pure gases were nearly identical. Column pressure drop during the desorption step was the cause.
ABSTRACT An isothermal–isobaric column dynamic test apparatus was built to measure equilibrium ad... more ABSTRACT An isothermal–isobaric column dynamic test apparatus was built to measure equilibrium adsorption isotherms of pure N2 and O2 and their binary mixtures at 0, 30, and 65 °C in the pressure range of 0–6 atm on LiLSX zeolite. The data successfully passed an integral and a differential thermodynamic consistency test between pure and binary gas isotherms. The binary selectivities of N2 over O2 were functions of the gas-phase mole fraction and pressure, and the pure gas isosteric heats of adsorption decreased with increased loadings. Thus, the adsorbent was energetically heterogeneous for both gases. The degree of heterogeneity for N2 was larger than that for O2.
ABSTRACT New experimental data are reported for equilibrium adsorption isotherm and mass transfer... more ABSTRACT New experimental data are reported for equilibrium adsorption isotherm and mass transfer of pure argon on a sample of pelletized LiLSX zeolite. Model analysis of the data indicate that the zeolite behaved like a nearly homogeneous adsorbent for Ar adsorption while it exhibited substantial heterogeneity for adsorption of N2 and milder heterogeneity for adsorption of O2. The over-all mass transfer coefficient for Ar adsorption was comparable in magnitude with those of N2 and O2. The coefficient increased with increasing pressure and decreased with increasing temperature like those for N2 and O2. A large skin resistance at the adsorbent particle surface was observed for Ar mass transfer like that for adsorption of O2 and N2.
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Papers by Chin-Wen Wu