Nanoscale Tubular Vessels for Storage of Methane at Ambient Temperatures

Abstract

Novel carbon nanostructures can serve as effective storage media for methane, a source of "clean energy" for the future. We have used Grand Canonical Monte Carlo Simulation for the modeling of methane storage at 293 K and pressures up to 80 MPa in idealized bundles of (10,10) armchair-type single-walled carbon nanotubes and wormlike carbon pores. We have found that these carbon nanomaterials can be treated as the world's smallest high-capacity methane storage vessels. Our simulation results indicate that such novel carbon nanostructures can reach a high volumetric energy storage, exceeding the US FreedomCAR Partnership target of 2010 (5.4 MJ dm(-3)), at low to moderate pressures ranging from 1 to 7 MPa at 293 K. On the contrary, in the absence of these nanomaterials, methane needs to be compressed to approximately 13 MPa at 293 K to achieve the same target. The light carbon membranes composed of bundles of single-walled carbon nanotubes or wormlike pores efficiently physisorb methane at low to moderate pressures at 293 K, which we believe should be particularly important for automobiles and stationary devices. However, above 15-20 MPa at 293 K, all investigated samples of novel carbon nanomaterials are not as effective when compared with compression alone since the stored volumetric energy and power saturate at values below those of the bulk, compressed fluid.

High-Pressure Methane Storage in Porous Materials: Are Carbon Materials in the Pole Position?

“…For samples with a purely microporous network excess adsorption isotherms exhibit a maximum at moderate pressures (6)(7)(8), the excess amount adsorbed slightly decreasing thereafter. This maximum in the excess adsorption isotherm indicates an increase in the methane density in the bulk phase while the adsorbed phase density remains mainly invariable, characteristic for adsorption of supercritical fluids.…”

“…[6][7][8] Grand Canonical Monte Carlo Simulations have predicted idealized bundles of SWNTs and wormlike carbon pores as promising nanomaterials for effective storage of methane at moderate pressures (1-7 MPa and 293K). 7 However, experimental studies from Yang et al using singlewalled carbon nanohorn assemblies have shown that the maximum gravimetric adsorption capacity at 6 MPa and 303 K cannot exceed 0.11 g/g. 8 Recently, higher methane uptakes were reported for ordered-mesoporous carbidederived-carbons (OM-CDC) with an excess adsorbed amount of 0.208 g/g at around 10 MPa and 298 K. 9 Unlike MOF materials, carbon materials exhibit a higher mechanical strength avoiding any packing-related efficiency loss provided that they can be optimized in terms of gravimetric and volumetric capacity.…”

Investigation of hydrogen and methane adsorption/separation on silicon nanotubes: a hierarchical multiscale method from quantum mechanics to molecular simulation

“…6. The methane fluid requires to be compressed to approximately 13 MPa at 293 K, to provide the 2010 target for volumetric energy storage (5.4 MJ/dm 3 ) (Kowalczyk et al 2006), whereas all the three silicon nanotubes investigated in this work achieved this goal at much lower pressures. Furthermore, since the interaction energies of methane with the SiNTs are in the region of physisorption, captured methane can simply be liberated by variation of the temperature.…”

“…The major impediments in this area are related to storage and transportation of these gases in a safe and economical way. Therefore, for H 2 and CH 4 storage, several alternative ways have been considered such as gas compression, liquefaction, and adsorption on solid state materials (Kowalczyk et al 2006;Morales-Cas et al 2007). …”

“…Their experimental data indicated that the methane uptakes of MWCNTs were higher than for zeolites. Kowalczyk et al (2006) have investigated methane storage on bundles of (10, 10) CNTs and worm-like carbon porous by GCMC simulation. Their results have revealed that such nanoscale materials can attain the US freedom CARP partnership goal at ambient temperature.…”