Investigation of methane adsorption on chlorite by grand canonical Monte Carlo simulations

In this paper, the methane adsorption behaviours in slit-like chlorite nanopores were investigated using the grand canonical Monte Carlo simulation method, and the influences of the pore sizes, temperatures, water, and compositions on methane adsorption on chlorite were discussed. Our investigation revealed that the isosteric heat of adsorption of methane in slit-like chlorite nanopores decreased with an increase in pore size and was less than 42 kJ/mol, suggesting that methane adsorbed on chlorite through physical adsorption. The methane excess adsorp- tion capacity increased with the increase in the pore size in micropores and decreased with the increase in the pore size in mesopores. The methane excess adsorption capacity in chlorite pores increased with an increase in pressure or decrease in pore size. With an increase in temperature, the isosteric heats of adsorption of methane decreased and the methane adsorption sites on chlorite changed from lower- energy adsorption sites to higher-energy sites, leading to the reduction in the methane excess adsorption capacity. Water molecules in chlorite pores occupied the pore wall in a directional manner, which may be related to the van der Waals and Coulomb force interactions and the hydrogen bonding interaction. It was also found that water molecules existed as aggregates. With increasing water content, the water molecules occupied the adsorption sites and adsorption space of the methane, leading to a reduction in the methane excess adsorption capacity. The excess adsorption capacity of gas on chlorite decreased in the following order： carbon dioxide 〉 methane 〉 nitrogen. If the mole fraction of nitrogen or carbon dioxide in the binary gas mixture increased, the mole fraction of methane decreased, methane adsorption sites changed, and methane adsorption space was reduced, resulting in the decrease in the methane excess adsorption capacity.

Hydrogen storage in BC_3 composite single-walled nanotube:a combined density functional theory and Monte Carlo investigation

This paper applies a density functional theory （DFT） and grand canonical Monte Carlo simulations （GCMC） to investigate the physisorptions of molecular hydrogen in single-walled BC3 nanotubes and carbon nanotubes. The DFT calculations may provide useful information about the nature of hydrogen adsorption and physisorption energies in selected adsorption sites of these two nanotubes. Furthermore, the GCMC simulations can reproduce their storage capacity by calculating the weight percentage of the adsorbed molecular hydrogen under different conditions. The present results have shown that with both computational methods, the hydrogen storage capacity of BC3 nanotubes is superior to that of carbon nanotubes. The reasons causing different behaviour of hydrogen storage in these two nanotubes are explained by using their contour plots of electron density and charge-density difference.