TY - JOUR
T1 - ZIF-8 Membrane Ethylene/Ethane Transport Characteristics in Single and Binary Gas Mixtures
AU - James, Joshua B.
AU - Wang, Jun
AU - Meng, Lie
AU - Lin, Jerry
N1 - Funding Information:
This work was supported by the National Science Foundation through grant CBET-1511005. We would like to thank the School for Engineering of Matter, Transport and Energy Lab Manager, Mr. Fred Peña, for his design and modification of the high pressure permeance cell utilized in this study. Additionally, we would like to acknowledge chemical engineering Professor Bin Mu and his Ph.D. student Bohan Shan for their work on the enclosed 3D ZIF-8 model. We gratefully acknowledge the use of facilities with the LeRoy Eyring Center for Solid State Science at Arizona State University.
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/7/5
Y1 - 2017/7/5
N2 - (Graph Presented) Zeolitic imidazolate framework-8 or ZIF-8 membranes have shown great promise in separating propylene/propane (C3) mixtures; however far fewer works have analyzed ethylene/ethane (C2) transport behavior in ZIF-8 membranes. This work studies C2 permeation behavior, transport properties, and selectivity as a function of temperature and pressure in single and binary gas mixtures. In single and binary separation tests conducted from 25 to 100°C, the permeances of ethylene and ethane show a negative correlation with temperature attributable to activation energies of diffusion (Ed) for ethylene and ethane (11.7 and 13.2 kJ/mol) that are lower than their respective heats of adsorption (16.2 and 17.1 kJ/mol). Low Ed values are observed for C2 molecules in ZIF-8 due to pore flexibility. C2 diffusive selectivity is limited in ZIF-8 due to the similar size of C2 molecules which are both smaller than the effective ZIF-8 pore aperture (low energetic selectivity) and sizable entropic selectivity is limited by the zeolitic pore shape. Binary selectivity is 20% lower than ideal selectivity due to cooperative adsorption, which enhances ethane adsorption in the presence of ethylene. The presence of relatively stronger adsorbing C2 molecules in mixture with hydrogen decreases H2 permeability and inverts the H2 temperature dependency of permeation from adsorption controlled to diffusion controlled. In single and binary C2 pressure dependent experiments performed between 1 and 4 atm, starkly contrasting ethylene/ethane separation profiles are observed due to differences in single and binary adsorption isotherms for C2 molecules. The ZIF-8 structure is amenable to adsorption/pressure induced distortions which greatly affect C2 permeation behavior.
AB - (Graph Presented) Zeolitic imidazolate framework-8 or ZIF-8 membranes have shown great promise in separating propylene/propane (C3) mixtures; however far fewer works have analyzed ethylene/ethane (C2) transport behavior in ZIF-8 membranes. This work studies C2 permeation behavior, transport properties, and selectivity as a function of temperature and pressure in single and binary gas mixtures. In single and binary separation tests conducted from 25 to 100°C, the permeances of ethylene and ethane show a negative correlation with temperature attributable to activation energies of diffusion (Ed) for ethylene and ethane (11.7 and 13.2 kJ/mol) that are lower than their respective heats of adsorption (16.2 and 17.1 kJ/mol). Low Ed values are observed for C2 molecules in ZIF-8 due to pore flexibility. C2 diffusive selectivity is limited in ZIF-8 due to the similar size of C2 molecules which are both smaller than the effective ZIF-8 pore aperture (low energetic selectivity) and sizable entropic selectivity is limited by the zeolitic pore shape. Binary selectivity is 20% lower than ideal selectivity due to cooperative adsorption, which enhances ethane adsorption in the presence of ethylene. The presence of relatively stronger adsorbing C2 molecules in mixture with hydrogen decreases H2 permeability and inverts the H2 temperature dependency of permeation from adsorption controlled to diffusion controlled. In single and binary C2 pressure dependent experiments performed between 1 and 4 atm, starkly contrasting ethylene/ethane separation profiles are observed due to differences in single and binary adsorption isotherms for C2 molecules. The ZIF-8 structure is amenable to adsorption/pressure induced distortions which greatly affect C2 permeation behavior.
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U2 - 10.1021/acs.iecr.7b01536
DO - 10.1021/acs.iecr.7b01536
M3 - Article
AN - SCOPUS:85022225705
SN - 0888-5885
VL - 56
SP - 7567
EP - 7575
JO - Industrial & Engineering Chemistry Research
JF - Industrial & Engineering Chemistry Research
IS - 26
ER -