Advanced nanostructured composite membranes for gas separations

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Advanced technologies for gas separation have become increasingly important to Canadian industry because of its significance to petrochemical, energy and resource sectors; however, current solutions are limited for certain applications. The proposed research will pursue development of advanced composite membranes with tailored nanostructures to effect gas separations that are important to Canadian industries but difficult to carry out with traditional technologies. Specifically, this research aims at developing innovative composite membranes with tailored nanostructures for 1) olefin/paraffin separation (to replace or complement with traditional energy-intensive low temperature distillation), 2) nitrogen removal from natural gas for upgrading, and 3) CO2 separations from flue gas for greenhouse gas emission control where a high membrane permselectivity is needed for the process to be economically feasible. Olefin separation and natural gas denitrogenation are two most challenging operations in the gas industry, while flue gas separation is important for carbon capture and pollution abatement. They are all directly related to Canada's strategic development of innovative technologies in the petrochemical, resource and energy industries. Membrane technologies have emerged as an energy efficient unit operation, but the current generation of membranes is not good enough for the aforementioned separations. It is proposed to tailor the membrane composition and nanostructure to enhance the membrane performance. In one approach, appropriate complexing agents will be incorporated into a polymeric base membrane to facilitate the permeation of a target component (e.g., olefin) by chemical interactions. The complexing agents will be embedded uniformly in the base polymer membrane to form nanostructured composite membranes. Silver ions and amine molecules will be chosen as the complexing agents for olefin and CO2 applications, respectively, to exploit the specific olefin-silver and CO2-amine interactions. In another approach, block copolymers with micro-biphase separated microstructures comprising of soft segments and rigid segments will be used for N2/CH4 separation, which is truly a challenge in practice for denitrogenation of natural gas as other techniques (e.g., absorption, adsorption) are also inadequate. For this pair of gases, suitable complexing agents for chemical facilitation are lacking. However, in block copolymers, the soft segments contribute to a high permeability, while the rigid segments are expected to be discretive to the diffusion of gas molecules. Their molecular structures can be tailored by adjusting the two segments, and additives that have specific interactions with or molecular sieving effect for CH4 or N2 may also be incorporated into the membrane to form a mixed matrix nanocomposite, thereby enhancing the overall membrane selectivity for N2/CH4 separation. Many natural gas reserves in Canada are of sub-quality because of high nitrogen contents, and successful development of the membrane will have a significant economic impact to the industry. The proposed research is highly original and innovative. Based on our preliminary success with such an innovative approach for olefin/paraffin separation, which is being exploited for commercial development by Canadian industry as a Canadian-owned potential "breakthrough" technology, this research will extend to include advanced membranes for CO2 separation and natural gas denitrogenation via appropriate nanostructuring of the membranes. Not only does this work directly address Canada's industrial needs for advanced membrane technologies, it will also contribute significantly to advancing knowledge and training of highly qualified personnel.