Control of pore environment in highly porous carbon materials for C2H6/C2H4 separation with exceptional ethane uptake

Adsorptive separation of C 2 H 6 from C 2 H 4 by adsorbents is an energy-efficient and promising method to boost the polymer grades C 2 H 4 production. However, that C 2 H 6 and C 2 H 4 display very similar physical properties, making their separation extremely challenging. In this work, by regulating the pore environment in a family of chitosan-based carbon materials (C-CTS-1, C-CTS-2, C-CTS-4, and C-CTS-6)- we target ultrahigh C 2 H 6 uptake and C 2 H 6 /C 2 H 4 separation, which exceeds most benchmark carbon materials. Explicitly, the C 2 H 6 uptake of C-CTS-2 (166 cm 3 /g at 100 kPa and 298 K) has the second-highest adsorption capacity among all the porous materials. In addition, C-CTS-2 gives C 2 H 6 /C 2 H 4 selectivity of 1.75 toward a 1:15 mixture of C 2 H 6 /C 2 H 4 . Notably, the adsorption enthalpies for C 2 H 6 in C-CTS-2 are low (21.3 kJ/mol), which will facilitate regeneration in mild conditions. Furthermore, C 2 H 6 /C 2 H 4 separation performance was confirmed by binary breakthrough experiments. Under different ethane/ethylene ratios, C-CTS-X extracts a low ethane concentration from an ethane/ethylene mixture and produces high-purity C 2 H 4 in one step. Spectroscopic measurement and diffraction analysis provide critical insight into the adsorption/separation mechanism. The nitrogen functional groups on the surface play a vital role in improving C 2 H 6 /C 2 H 4 selectivity, and the adsorption capacities depend on the pore size and micropore volume. Moreover, these robust porous materials exhibit outstanding stability (up to 800 °C) and can be easily prepared on a large scale (kg) at a low cost (∼$26 per kg), which is very significant for potential industrial applications.