Oxygen-enriched carbon molecular sieve hollow fiber membrane for efficient CO₂ removal from natural gas

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 degrees 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 degrees 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.