Correlation of Gas Permeability and Diffusivity with Selectivity: Orientations of the Clouds of the Data Points and the Effects of Temperature
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- 作者：Alexandre Alentiev ; Yuri Yampolskii
- 刊名：Industrial & Engineering Chemistry Research
- 出版年：2013
- 出版时间：July 3, 2013
- 年：2013
- 卷：52
- 期：26
- 页码：8864-8874
- 全文大小：842K
- 年卷期：v.52,no.26(July 3, 2013)
- ISSN：1520-5045
文摘
For an extended data set for amorphous glassy polymers, the pair correlations Pi鈥?i>Pj fulfill with very good accuracy (R2 about 0.9 or higher) where Pj and Pj are the permeability coefficients of the gases Mi and Mj in the same polymers. This allowed us to determine the orientation (medians) of the clouds of the data points on the correlations log Pi versus 伪ij = Pi/Pj. It was shown that for various gas pairs the slopes of these medians are negative and increase by absolute value when the ratio of kinetic diameters of the penetrants increases. For the first time a similar analysis was carried out for pair correlations of the diffusion coefficients Di and Dj. On the diagrams log Di versus 伪Dij = Di/Dj, the medians show the same trend as in the diagrams for permeability coefficients. The effects of temperature on the orientation of the clouds of the data points and upper bounds (limiting lines) of the diagrams log Pi versus 伪ij = Pi/Pj were investigated using the available values of the activation energy of permeation. It was shown that for all the gas pairs the medians tend to shift down along the selectivity axis when temperature increases. Depending on a selected gas pair the slopes of the medians and upper bounds get either steeper or weaker. It was discussed that the positions and the slopes of the medians and limiting lines are sensitive to the Arrhenius parameters of gas permeation and temperature.