Carbon molecular sieve gas separation membranes based on an intrinsically microporous polyimide precursor

• Published in: Carbon (New York) Vol. 62; pp. 88 - 96
• Main Authors: Ma, Xiaohua, Swaidan, Raja, Teng, Baiyang, Tan, Hua, Salinas, Octavio, Litwiller, Eric, Han, Yu, Pinnau, Ingo
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.10.2013; Elsevier
• Subjects: adsorption; Amorphous semiconductors, metals, and alloys; Carbon; Carbon dioxide; Chemistry; Colloidal state and disperse state; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Disordered solids; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; Gas separation; General and physical chemistry; Heat treatment; Materials science; Membranes; methane; Permeability; Physics; Polyimide resins; polymers; Porous materials; Selectivity; Specific materials; Structure of solids and liquids; crystallography; surface area; Methane; Membranes; Transport properties; Separation; Porous materials; Carbon dioxide; Selectivity; Molecular gas; Permeability; Molecular sieves; Carbon; Precursor; Heat treatments; Chemical reduction; Microporosity; Polyimides; Transport processes; Surface area; Polymers; Amorphous state structure; Inorganic membrane
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2013.05.057

We report the physical characteristics and gas transport properties for a series of pyrolyzed membranes derived from an intrinsically microporous polyimide containing spiro-centers (PIM-6FDA-OH) by step-wise heat treatment to 440, 530, 600, 630 and 800°C, respectively. At 440°C, the PIM-6FDA-OH was converted to a polybenzoxazole and exhibited a 3-fold increase in CO2 permeability (from 251 to 683 Barrer) with a 50% reduction in selectivity over CH4 (from 28 to 14). At 530°C, a distinct intermediate amorphous carbon structure with superior gas separation properties was formed. A 56% increase in CO2-probed surface area accompanied a 16-fold increase in CO2 permeability (4110Barrer) over the pristine polymer. The graphitic carbon membrane, obtained by heat treatment at 600°C, exhibited excellent gas separation properties, including a remarkable CO2 permeability of 5040Barrer with a high selectivity over CH4 of 38. Above 600°C, the strong emergence of ultramicroporosity (<7Å) as evidenced by WAXD and CO2 adsorption studies elicits a prominent molecular sieving effect, yielding gas separation performance well above the permeability-selectivity trade-off curves of polymeric membranes.