A novel type microporous adsorbent based on single-walled carbon nanotubes assembled by toluene molecules for methane storage

Single-walled carbon nanotube (SWCNT) based materials are considered as one of the most promising adsorbents for adsorption-based technology for methane storage. Molecular dynamic simulations are employed to investigate the assembling of single-walled carbon nanotubes into an array via toluene coordinator-molecules. The smallest number of toluene molecules sufficient to maintain the ASWCNT + nC7H8 supramolecular structure is defined. The potential, kinetic and total energies of the simulated system plotted as a function of toluene molecules are used to evaluate the stability condition for the supramolecular structure. Methane adsorption onto the model ASWCNT + nC7H8 adsorbent is simulated to assess the contributions of toluene molecules to its adsorption capacity. The radial and angular probability density distributions of methane molecules in the ASWCNT + nC7H8 adsorbent reveal the most probable location of adsorbed methane near the SWCNT walls and toluene molecules as centers of adsorption. A SWCNT-based adsorbent is prepared by the saturation with toluene and subsequent two-step regeneration with a slow-rate increase in temperature. The content of toluene of 5wt.% in the adsorbent thus obtained is evaluated from a gain in weight observed at 338 K. Methane adsorption on the initial SWCNT and SWCNT + 5%C7H8 adsorbents is measured at 178 and 273 K up to 101 kPa. A comparison of the initial and differential molar heats of methane adsorption on the initial SWCNT and ASWCNT + nC7H8 adsorbents points to the role of toluene molecules as additional centers of adsorption. We estimate the contribution of toluene molecules to the porosity of the ASWCNT + nC7H8 adsorbent from the methane adsorption data.