Melamine-Copolymerization Strategy Engineered Fluorinated Polyimides for Membrane-Based Sour Natural Gas Separation.

Membrane-based gas separation provides an energy-efficient approach for the simultaneous CO2 and H2S removal from sour natural gas. The fluorinated polyimide (PI) membranes exhibited a promising balance between permeability and permselectivity for sour natural gas separation. To further improve the separation efficiency of fluorinated PI membranes, a melamine-copolymerization synthetic approach is devised that aims to incorporate melamine motifs with high sour gas affinity into the structure of the PI membranes. The fluorinated copolyimide membranes that are structurally engineered exhibited excellent solution-processability and enhanced sweet-mixed gas selectivity compared to their original PI membranes. Additionally, under a five-component sour mixed-gas feed, these melamine-copolymerized fluorinated PI membranes provided superior combined H2S and CO2 removal efficiency in comparison to conventional glassy polymer membranes. The melamine-copolymerization strategy provides an easily operable and generally effective approach to developing performance-enhancing PI membranes for sour natural gas separation.