Novel asphaltene-derived nanoporous carbon with N-S-rich micro-mesoporous structure for superior gas adsorption: Experimental and DFT study

© 2018 The development of waste-derived nanoporous carbon, especially from petroleum wastes, as a challenging type of contaminants, has drawn tremendous attention during the past decade. In this work, for the first time, a novel N-S-rich nanoporous carbon possessing high value-added and porosity, was prepared from asphaltene residue through a simple chemical activation. After carbonization of the precursor at 450 °C, chemical activation by different KOH/C ratios (2:1 to 5:1 g/g) was followed which resulted in the formation of unique micro-mesoporous structures (named as IANC samples). The results displayed that large surface area (up to 2186 m2/g) and pore volume (up to 1.3 cm3/g) were obtained. The IANC samples showed outstanding CO2 and H2S uptake at both atmospheric (7.15 mmol/g for CO2 and 12.86 mmol/g for H2S at 1 bar and 25 °C) and high pressures (29.29 mmol/g for CO2 and 38.61 mmol/g for H2S at 35 bar and 25 °C). Furthermore, the IANCs exhibited excellent selectivity for CO2/CH4, H2S/CH4 and CO2/N2 samples. To better understand the interactions mechanism between adsorbent and each adsorbed molecule and also to determine the active sites in the adsorption process, the density functional theory (DFT) method was employed. The quantum chemistry calculations elucidated the exciting impact of defected nitrogen and sulfur sites in enhancing adsorption interaction of H2S and CO2. Besides the fascinating gas uptake and the preferential gas adsorption, the synthesized IANCs possessed high heat of adsorption and stable cyclic adsorption-desorption ability. Considering the inexpensive cost of asphaltene along with the desired adsorption properties, the asphaltene-derived activated nanoporous carbon (i.e., IANC) can be a promising candidate for superior gas adsorption.