(160c) Mixed-Matrix Membranes Containing Engineered Nanoporous Materials for Biogas Purification

Authors: 
Bae, T. H., Nanyang Technological University
Biogas produced in anaerobic digestion process has been considered as a renewable energy source. For the recovery and the purification of biogas, various processes for CO2 separation including amine-scrubbing and adsorption have been employed. Although membrane-based gas separation is an ideal platform for the biogas recovery/purification, the applications have been limited by the unsatisfactory performance of commercial polymeric membranes under the biogas separation conditions such as low CO2 partial pressure. Thus, improving the performance of current polymeric membranes, which are inexpensive and mechanically stable, may facilitate the application of membrane technology in large-scale biogas upgrading processes. To this end, various porous materials that can selectively transport CO2 can be incorporated into polymer matrices to design CO2-selective mixed-matrix membranes.

Among various porous materials, metal-organic frameworks which comprise metal center and organic linkers to form three-dimensional porous structure have attracted vast research interests in the recent years as potential fillers for mixed-matrix membrane fabrication owing to their large pore volumes and tunable functionalities. In this work, a submicron-sized Zn(pyrz)2(SiF)6 metal-organic framework crystal possessing both an optimum pore size for selective CO2 permeation and a strong affinity for CO2 molecule was synthesized and incorporated into various polymer membranes to design mixed-matrix membranes for biogas upgrading. CO2/CH4 mixture gas permeation tests revealed that the separation properties of mixed-matrix membranes, especially selectivities, were significantly improved compared to those of pure polymeric membrane owing to the selective CO2 uptake and transport in the metal-organic framework crystals.

Recently, our research group have developed hierarchical mesoporous Ca-A zeolites with amine-appended mesoporous domain for application in post-combustion CO2 capture. Owing to the contributions of both the active sites in Ca-A zeolites and the amine groups in mesoporous surfaces, the material exhibited an excellent CO2 uptake property even at low CO2 partial pressure. Moving forward, amine-appended hierarchical Ca-A was employed as a filler for mixed-matrix membranes to improve CO2 selectivity. Gas permeation testing revealed that the amine-appended hierarchical Ca-A is highly efficient in enhancing CO2/CH4 selectivity of polymeric membranes.

References

1. H. Gong, T. H. Nguyen, R. Wang, T. H. Bae, Separations of binary mixtures of CO2/CH4 and CO2/N2 with mixed matrix membranes containing Zn(pyrz)2(SiF)6 metal-organic framework, J. Membr. Sci. 2015, 495, 169-175

2. T. H. Nguyen, S. Kim, M. Yoon, T. H. Bae, Hierarchical LTA zeolites with amine-functionalized mesoporous domain for carbon dioxide capture, ChemSusChem, 2016, DOI:10.1002/cssc.201600004

3. T. H. Nguyen, H. Gong, S. S. Lee, T. H. Bae, Amine-appended hierarchical Ca-A zeolite for enhancing CO2/CH4 selectivity of mixed-matrix membranes, submitted