Urea-assisted synthesis of biomass-based hierarchical porous carbons for the light hydrocarbons adsorption and separation

The light hydrocarbons adsorption and separation from mixed gas is very important to the petroleum industry. Herein, a simple and effective strategy for preparing hierarchical porous carbons (HPCs) derived from biomass and urea with tunable pore size distribution is proposed. With the increase of urea content, the pore size distributions of HPCs become narrow, and the surface area (from 3588 to 2626 m2 g−1) and total pore volume (2.605 to 1.688 mL g−1) decrease. Tested at an adsorption temperature of 25 °C and a pressure of 1 bar, the resulting HPC800-0.5 has excellent C3H8 (12.18 mmol g−1) and C2H6 (6.88 mmol g−1) uptake capacity, while HPC800-1.5 exhibits the highest IAST-predicted C3H8/CH4 (91) and C2H6/CH4 (15) selectivity. Molecular simulations suggest that the porous structure (or more specifically micropores) has a more prominent effect on C2H6 and C3H8 capture at 1 bar than functional groups. The selectivity of C3H8/CH4 and C2H6/CH4 mainly depends on the narrow micropores (C3H8/CH4, pore size ＜1.2 nm and C2H6/CH4, pore size ＜1 nm) of carbon-based materials. This study provides insights for the further design and development of adsorbents for light hydrocarbons adsorption and separation from natural gas.