The dual role of acetate additives among carbon materials functionalized and CH4/N2 separation

Carbon materials with superior advantages have attracted much attention in the field of CH4/N2 separation, and selecting suitable carbon precursors and activated ways can be crucial to driving the further development of this domain. Through it, we proposed a feasible method to prepare composite carbon materials (Ni@C-n and Co@C-n) based on cellulose acetates (CA) with acetate activation. Such additives played a dual role, which means the produced thermal decomposition of anions to optimize the porous structure and they induce cations transforming into metal species to enhance the adsorbed potential towards CH4. Consequently, the N2 adsorption-desorption isotherm showed that the excellent Ni@C-M adsorbent was rich in micropores and mesopores, with a BET surface area of 610.2 cm2/g and microporous area of 358.8 cm2/g. The Ni@C-M adsorbent reached 18.2 cm3/g at 298 K and 0.1 MPa, increasing by 43.3% compared to C support, and exhibited the highest CH4/N2 selectivity of 7.5 (5/95, v/v) among various series adsorbents, which was superior to most carbon materials reported so far. The values of adsorption heat (Qst) ranged between 14.63–19.23 kJ/mol and 22.69–24.87 kJ/mol for C support and Ni@C-M adsorbents respectively, confirming Ni@C-M with the stronger adsorption potential energy towards CH4. This research provides promising adsorbents for the purification of low-concentration coal gas and offers new clues for functionalizing carbon materials via utilizing metal salts.