Abstract
AbstractWe used molecular simulations to study the effect of pore structure and geometry on the selectivity of carbon materials for the adsorption of methane from a mixture of methane and hydrogen at 50 bar and 298 K. We modeled hydrogen as a more realistic dumb-bell shaped fluid and methane as spherical Lennard-Jones sphere. The pore geometry studied includes the slit, nanotube, random carbon structure and carbon pores that mimic a foam structure. Our results confirm that both the pore size and pore structure have a significant effect on the selectivity for methane molecules. An array of nanotubes that have a closed structure has the highest selectivity for methane molecules, followed by carbon foam, slit and random pore structures. Energetic and packing effects at low and high pressures, respectively, influence the selectivity for methane. Reduction in entropy of hydrogen in smaller pores increases the selectivity for methane molecules.
Highlights
Physical adsorption of methane and hydrogen gas mixtures in microporous carbons is considered to be important and fundamental in (i) heterogeneous catalytic processes, (ii) cleaner hydrogen production technologies and (iii) fuel storage applications.In any case, the selectivity remains higher than unity due to the energetic effects.Pores that can hold [1,2] layers of CH4 were found to be the optimum pore size for the selective adsorption of CH4mole3cu5les at 298 K 6001.5 nm random foam p, bar Considering the significance of adsorption and separation of CH4 and H2 mixtures in carbon materials, in this work we carried out GCMC simulations to theoretically study the effect of pore structure and geometry on the selective separation of methane molecules from CH4/H2 mixtures
The GCMC results shows that the pore structure and geometry have a significant effect on the selectivity of methane
Irrespective of the carbon pore structure or geometry, the selectivity at 298K was affected by both energetic effects at low pressure and packing effects at higher pressures
Summary
Müller (b)* and Francisco RodriguezReinoso (a) eMffeacyt oWf proarepgteoomtheteryNaendxtstLruicnteure (a) Laboratorio de Materiales Avanzados, Departamento de Química InorgánicaUniversidad de Alicante, Apartado 99. (b) Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7. In larger pores these effects seems to negligible and the selectivity was found to be relatively higher in pores of size that can hold [1,2] layers of methane molecules. Nature Precedings : doi:10.1038/npre.2011.6132.1 : Posted 21 Jul 2011 selectivity selectivity selectivity selectivity
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