(401ah) High-Resolution Scalable Propylene/Propane Separation for ZIF-8 Polycrystalline Membranes on Ceramic Tubular Supports

High-resolution Scalable
Propylene/Propane Separation for ZIF-8 Polycrystalline Membranes on Ceramic
Tubular Supports

Jingze Sun¹
and Hae-Kwon Jeong*^1,2

¹Artie
McFerrin Department of Chemical Engineering and ²Department of Materials
Science and Engineering, Texas A&M University, College Station, TX 77843-3122

* Corresponding author: hjeong7@tamu.edu

Zeolite-imidazole
frameworks (ZIFs) have been extensively studied as a new membrane material for
gas separations due to their robust synthesis protocols, chemical and thermal
stability, and well-defined ultra-micropores (~ 2 to 5 Å).^1,
2 ZIFs are comprised of metal centers (Zn, Co, and Cd) and bridging
imidazole-based ligands. ZIF-8, composed of zinc nodes and 2-methylimidazole
linkers, has been shown very promising for propylene/propane separations since its
effective aperture size lies in between propylene (~ 4 Å) and propane (~ 4.2 Å).³
In fact, some of the polycrystalline ZIF-8 membranes synthesized by various
methods have been reported to exhibit impressive propylene/propane separation
factors up to 200.^{4, 5} These highly propylene-selective ZIF-8
membranes were supported mostly on alumina disks or occasionally on hollow
fibers (polymer or ceramic).

For their large-scale industrial
applications, however, the productivities of ZIF-8 membranes must be
significantly improved.⁶
One way to increase the membrane productivity is to increase membrane area per
volume. As such, current disk supports are not desirable. Though hollow fiber
supports (either polymer or ceramic) are most desirable, they are unlikely to
be used for large-scale applications in near future. This is because ceramic hollow
fibers are highly fragile while polymer hollow fibers require much more
development. While hollow fiber supports are transformative, ceramic tubular
supports are readily available for large-scale applications. For example,
ceramic tubular supports have been used for commercial polycrystalline zeolite
membranes.⁷
Though ZIF-8 membranes on ceramic tubular supports were reported, none of those
membranes showed promising propylene/propane separation capabilities.^{8, 9}

Here, we would like to
present polycrystalline ZIF-8 membrane supported on alumina tubes showing high propylene/propane
separation performances. The tubular membranes were synthesized using our microwave
seeding and secondary growth method. The effects of the synthesis parameters on
the microstructures of tubular ZIF-8 membranes will be presented. Finally, the
propylene/propane separation performances of ZIF-8 membranes supported on
alumina tubes will be discussed.

References and Notes:

(1)        Park, S.; Kang, W. R.; Kwon, H. T.; Kim, S.; Seo, M.; Bang, J.; Lee, S. h.;
Jeong, H. K.; Lee, J. S., The polymeric upper bound for N2/NF3 separation and
beyond; ZIF-8 containing mixed matrix membranes. J. Membr. Sci. 2015,
486, 29-39.

(2)        Chen
Zhang, R. P. L., Ke Zhang, Justin R. Johnson, Oguz Karvan, William J. Koros,
Unexpected molecular sieving properties of zeolitic imidazolate framework-8. The
journal of physical chemistry letters 2012, 3, (16), 2130-2134.

(3)        Li,
K.; Olson, D. H.; Seidel, J.; Emge, T. J.; Gong, H.; Zeng, H.; Li, J., Zeolitic
imidazolate frameworks for kinetic separation of propane and propene. J. Am.
Chem. Soc. 2009, 131, (30), 10368-9.

(4)        Lee,
M. J.; Kwon, H. T.; Jeong, H. K., Defect-dependent stability of highly
propylene-selective zeolitic-imidazolate framework ZIF-8 membranes. J.
Membr. Sci. 2017, 529, 105-113.

(5)        Pan,
Y. C.; Li, T.; Lestari, G.; Lai, Z. P., Effective separation of
propylene/propane binary mixtures by ZIF-8 membranes. J. Membr. Sci. 2012,
390, 93-98.

(6)        Baker,
R. W., Future directions of membrane gas separation technology. Ind. Eng.
Chem. Res. 2002, 41, (6), 1393-1411.

(7)        Kosinov,
N.; Gascon, J.; Kapteijn, F.; Hensen, E. J., Recent developments in zeolite
membranes for gas separation. J. Membr. Sci. 2016, 499, 65-79.

(8)        Hara,
N.; Yoshimune, M.; Negishi, H.; Haraya, K.; Hara, S.; Yamaguchi, T., Diffusive
separation of propylene/propane with ZIF-8 membranes. J. Membr. Sci. 2014,
450, 215-223.

(9)        Zhang, X.; Liu, Y.; Kong, L.; Liu, H.;
Qiu, J.; Han, W.; Weng, L.-T.; Yeung, K. L.; Zhu, W., A simple and scalable
method for preparing low-defect ZIF-8 tubular membranes. J. Mater. Chem. A 2013,
1, (36), 10635.