Tuning carbon molecular sieves for natural gas separations: A diamine molecular approach

详细信息    查看全文

• 作者：Graham B. Wenz and William J. Koros
• 刊名：AIChE Journal
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：63
• 期：2
• 页码：751-760
• 全文大小：795K
• ISSN：1547-5905

文摘

This article introduces a new postsynthetic modification method for tuning the separation properties of carbon molecular sieve (CMS) membranes. Polymeric hollow fibers of 6FDA/BPDA-DAM were pyrolyzed to 550°C under inert Argon, and were then exposed to a tetrahydrofuran solution containing PPM levels of paraphenylenediamine dopant. The original goal of the treatment was to modify the morphology in a manner to prevent relaxation of the CMS to suppress physical aging, envisioned to be analogous to that in glassy polymer membranes where reduction of “unrelaxed free volume” causes reduced permeance with a mild increase in selectivity. Results of long-term CO₂ and CH₄ permeation experiments of doped fibers showed that aging-resistant membranes did not result. This fact notwithstanding, results revealed this approach provides a valuable new tuning tool for CMS transport properties. Complementary gas sorption experiments performed suggest the amine dopants tune large ultramicropores, thereby increasing size and shape based diffusion selectivity.