Modulating the porosity of activated carbons via pre-mixed precursors for simultaneously enhanced gravimetric and volumetric methane uptake†
Pre-mixed precursors containing biomass-derived carbonaceous matter of varying O/C ratio and polypyrrole have been used as starting materials to modulate the porosity of activated carbons. The use of pre-mixtures of polypyrrole and CNL carbon (from accidental and uncontrolled burning of wood under fierce fire conditions of the first Carbon Neutral Laboratory, CNL, building at Nottingham) or polypyrrole and ACDS carbon (air-carbonised date seed) generates activated carbons with substantially greater surface area than single use of any of the precursors. Mixing of CNL carbon or ACDS carbon, which are known to generate highly microporous carbons, with polypyrrole, which generates mesoporous carbons, yielded activated carbons with a much wider range of porosity. More importantly, it is possible to prepare activated carbon with ultra-high surface area (up to 3890 m2 g−1) and pore volume (up to 2.40 cm3 g−1) in a manner not possible via single use of any of the precursors. The resulting ultra-high surface area carbons have excellent gravimetric methane uptake, which at 25 °C and 100 bar, can reach up to 28.4 mmol g−1 (or 0.46 g g−1). In addition to the excellent gravimetric uptake, at 25 °C and 100 bar, the carbons have total volumetric methane uptake of up to 260 cm−3 (STP) cm−3, and working capacity (100–5 bar) of 210 cm−3 (STP) cm−3. The combination achieved for gravimetric and volumetric uptake is higher and more attractive than any previous value for porous carbons or metal–organic-frameworks (MOFs).
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