Methane adsorption in nanoporous activated carbon [abstract]
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Natural gas is an economically and environmentally superior fuel to both gasoline and diesel. One challenge of this fuel is to find a high-capacity, low pressure method of storing it. Fractal networks of nanopores in activated carbon produced from waste corn cob have shown promising results with regard to storage of both natural gas (methane) and hydrogen. Adsorption of methane on briquetted and powder samples is measured gravimetrically after samples are out-gassed for two hours and exposed to the gas for one hour. This test is performed at varying pressures on different samples in order to determine the best performers. Additionally, small-angle X-ray scattering (SAXS) analysis is performed in order to determine the structure of the pore networks. The added surface area created by the pore structure (a combined surface area of up to 3 500 m²/g carbon), as well as strong Van der Waals forces in the pores which drive the methane into a supercritical, high-density liquid state, allow adsorption of the gas to occur at record-breaking levels. Data found through the gravimetric and SAXS measurements reveal improvements in pore size and carbon activation processes that can lead to better storage capacities. This storage technology is currently being tested on a natural gas tank prototype vehicle, and future improvements are being explored.