Revolutionary Ultrathin Carbon Molecular Sieve Hollow Fiber Membranes

Revolutionary ultrathin carbon molecular sieve hollow fiber membranes

 

Chen Zhang, William J. Koros

Georgia Institute of Technology, Atlanta, Georgia U.S.A.

 

 

Carbon molecular sieves (CMSs) are membrane materials with tailored microporosity offering attractive mechanical properties and extraordinary permselectivities for many gas pairs. The extraordinary permselectivities well exceed polymer upper bounds, which rely upon entropically-enabled diffusion selectivities and synergistic sorption selectivities.¹ CMSs can be transformed into the preferred scalable hollow fiber geometry by controlled pyrolysis of asymmetric polymer precursor hollow fibers. The porous substrate of CMS fibers tends to densify during pyrolysis. In that case, the CMS hollow fiber membrane completely or partially loses its asymmetry, thereby producing thick separation layer (30-50 μm) with unattractive permeance.²

In this work, we present formation of CMS hollow fiber membranes with ultrathin skin (separation) layers for gas and vapor separations. By tuning the membrane structure and formation process, we have created advanced CMS hollow fiber membranes with excellently-preserved asymmetry and defect-free sub-micron skin layers. The ultrathin CMS hollow fiber membranes show permeances that are an order of magnitude higher than state-of-the-art CMS hollow fiber membranes for a given precursor material³, while maintaining highly attractive separation factors. Combining high scalability, high permeance and high selectivity, the ultrathin CMS hollow fiber membranes offer an attractive and uniquely-flexible platform for next-generation membrane-enabled fluid separations.

References

1            Koros, W. J. & Zhang, C. Nat Mater 16, 289-297, (2017).

2            Xu, L., Rungta, M. & Koros, W. J. J. Membr. Sci. 380, 138-147, (2011).

3            Bhuwania, N. et al. Carbon 76, 417-434, (2014).