Oxygen-enriched carbon molecular sieve hollow fiber membrane for efficient CO2 removal from natural gas
Kaixin Wang, Chuning Fang, Zhi Li, Guanran Zhao, Yixing Wang, Zhen Song, Linfeng Lei, Zhi Xu
Abstract
Natural gas is considered one of the most attractive low carbon energy sources while the separation of CO 2 is a crucial process for the natural gas purification. Herein, cellulose-based carbon molecular sieve (CMS) hollow fiber membranes with high CO 2 affinity capability were fabricated through a post-treatment strategy of hydrogen-induced reduction followed by oxygen-doped modification (H-O treatment), and show good potential for high pressure natural gas purification. The CMS membranes were reduced by H 2 at high temperatures (500–600 °C) to form active sorption sites in the carbon matrix, and subsequently chemically absorbed O 2 to generate oxygen-containing functional groups, which are favorable for CO 2 adsorption and diffusion. After being treated at 600 °C (CMS-600), the CMS membrane presented a high CO 2 adsorption capacity of 62.78 cm 3 /g (298 K). As a result, the CO 2 permeability was enhanced from 264 to 1125 Barrer, with approximately 400 % improvement. Moreover, mixed gas separation performances (CO 2 /N 2 and CO 2 /CH 4 ) were investigated at high pressure and impurities feedings. The CMS membrane exhibited a remarkable CO 2 /CH 4 separation factor of 104 when operated at 20 bar and 500 ppm heptane existed.