Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4988970 | Journal of Membrane Science | 2017 | 41 Pages |
Abstract
The thermal stability of ZIF membranes is important for high temperature separation applications but has not been systematically studied. This work highlights the results of a thermal stability study of ZIF-8 membranes in terms of material structure, H2/CO2 gas permeation and separation characteristics. During binary and single gas temperature dependent permeance tests conducted from 25 to 250 °C, both H2 and CO2 permeances decrease as a function of temperature. In the binary test, H2/CO2 selectivity increases between 25 and 225 °C, and then decreases as temperature is further increased between 225-275 °C. The results can be explained by the adsorption/diffusion mechanism. Beyond 275 °C, H2/CO2 permeance and selectivity drastically increase with respect to temperature and is indicative of ZIF-8 membrane partial carbonization during the dynamic 30 h temperature dependent test. The time/temperature dependency of the onset of ZIF-8 thin film structural change was deconvoluted in isothermal transient permeation experiments. Transient tests performed at 50, 100, 150 and 300 °C for 24 h indicate that ZIF-8 thin films maintain their crystallinity and structural integrity below 150 °C. However, at temperatures of 150 °C and greater the framework undergoes increased magnitudes of thermally induced carbonization as a function of temperature. Thermomechanically induced stresses between the ZIF-8 membrane thin film and α-alumina support may account for differences in static thermal stability observed when comparing ZIF-8 membranes and ZIF-8 crystalline powders.
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Filtration and Separation
Authors
Joshua B. James, Y.S. Lin,