TY - JOUR
T1 - Thermal stability of ZIF-8 membranes for gas separations
AU - James, Joshua B.
AU - Lin, Jerry
N1 - Funding Information:
This work was supported by the National Science Foundation through grant CBET-1511005. We would like to thank our Lab Manager Mr. Fred Peña for his design and modification of the high temperature permeance cell utilized in this study. We gratefully acknowledge the use of facilities with the LeRoy Eyring Center for Solid State Science at Arizona State University.
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2017
Y1 - 2017
N2 - 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.
AB - 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.
KW - Gas separation
KW - High temperature
KW - Membrane carbonization
KW - Thermal stability
KW - ZIF-8 membrane
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U2 - 10.1016/j.memsci.2017.02.017
DO - 10.1016/j.memsci.2017.02.017
M3 - Article
AN - SCOPUS:85014927527
SN - 0376-7388
VL - 532
SP - 9
EP - 19
JO - Jornal of Membrane Science
JF - Jornal of Membrane Science
ER -