Construction of Macropores in a Hollow Fiber Carbon Membrane Enables Efficient CO₂ Removal from Natural Gas

Membrane-based CO2 separation technology is highly desired for natural gas sweetening, and the development of advanced membrane materials with low cost and high CO2/CH4 separation factors under high pressures is the key to the membrane market. Herein, cellulose-derived carbon molecular sieve (CMS) hollow fiber membranes within macropores were constructed by incorporating a thermal labile polymer of poly(vinyl butyral) (PVB). During a controlled carbonization protocol, the spun cellulose membranes formed the CMS membrane matrix, while the PVB formed homogenized macropores. As a result, the generated macropores in the CMS hollow fiber membranes (CHFMs) effectively reduced the gas transport resistance, confirmed by an increased CO2 permeance by ∼2.9-fold from 8.48 to 24.72 GPU (CHFM-1) compared to CHFM-0. Moreover, the membranes were evaluated using a simulated high-pressure natural gas stream (3.44 mol % CO2–87.0 mol % CH4–9.56 mol % N2) and showed good separation performance with a CO2 permeance of 11.66 GPU and a CO2/CH4 separation factor of 38.3 at 30 bar feeding. A long-term durability test over 100 h at 20 bar with a slight decrease in permeance further verified its potential for CO2 removal from high-pressure natural gas.