Tertiary amine-mediated synthesis of microporous carbon membranes

• Published in: Journal of membrane science Vol. 280; no. 1; pp. 603 - 609
• Main Authors: Nishiyama, Norikazu, Dong, Yong-Rong, Zheng, Tao, Egashira, Yasuyuki, Ueyama, Korekazu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2006
• Subjects: Carbon; Gas separation; Micropore; Resorcinol/formaldehyde resin; Tertiary amines; Gas separation; Tertiary amines; Micropore; Carbon; Resorcinol/formaldehyde resin
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2006.02.018

Microporous carbon membranes were prepared on an α-alumina support by a pyrolysis of cationic tertiary amine/anionic polymer composites. The precursor solutions contain a thermosetting resorcinol/formaldehyde (RF) polymer and a cationic tertiary amine. Three types of cationic tertiary amines with different chain lengths were used, such as tetramethlammonium bromide (TMAB), tetrapropylammonium bromide (TPAB) and cetyltrimethylammonium bromide (CTAB). A porous structure was produced by a decomposition of the amine and the resulting pores assisted the further gasification of the RF polymer at high temperature. The carbon/alumina membranes have thin and continuous carbon top layers with a thickness of 1 μm. Gas permeation tests were performed using single gases of CO 2, O 2, N 2, CF 4, n-C 4H 10 and i-C 4H 10, as well as binary mixtures of CH 4/ n-C 4H 10 and N 2/CF 4 at different temperatures between 23 and 150 °C. The carbon membrane prepared using TMAB showed separation factors higher than 650 for the CH 4/ n-C 4H 10 mixtures and higher than 8100 for the N 2/CF 4 mixture. From the permeation of pure gases with different molecular sizes, the pore sizes of the carbon membrane prepared using TMAB, TPAB and CTAB are estimated to be 4.0, 5.0 and larger than 5.5 Å, respectively, indicating that the micropore size of the carbon membranes is controllable by using different amines.