Engineered cellulose-based porous carbon adsorbents for superior gas adsorption and selective separation of CH4/H2 and CH4/N2

Abstract

Adsorption and separation of methane from turquoise hydrogen and coalbed methane is becoming an important method for using unconventional natural gas. Adsorbent performance determines this technique. In this regard, the cellulose-based (Cell-PC) adsorbents were engineered by a facile process with a one-pot calcination method without solvent and an activating reagent-free like KOH with an economical and green approach for CH4/H2 and CH4/N2 separation. The series of adsorbents were synthesized, such as Cell-100, U-Cell-111, O-Cell-111, O-Cell-112, O-Cell-113, and O-Cell-113-a, from cellulose with urea/oxalic acid and sodium hydrogen carbonate, which helps to create pore structure. All adsorbents were characterized by several techniques, including XRD, SEM, XPS, and BET. All Cell-PC adsorbents were used to systematically investigate adsorption studies for CH4, N2, and H2. The O-Cell-113-a adsorbent demonstrated a superior CH4 uptake capacity of 52.75 cm3/g at 273 K and 37.92 cm3/g at 298 K under 100 kPa. It was attributed to the synergistic role of high surface area, mesopore volume, micropore volume, morphology, and surface functional group. However, the O-Cell-113-a showed lower adsorption for N2 and was unable to adsorb H2 at 298 K, indicating the adsorbent has selective adsorption properties for CH4. Furthermore, the ideal adsorbed solution theory (IAST) model was used to calculate the selectivity of CH4/N2, which was found to be around 13.78 at 273 K and 12.64 at 298 K, which is higher than most previously reported porous carbon. The isosteric heat of adsorption of O-Cell-113-a adsorbent was further calculated for CH4 and N2.