**11. Conclusion**

Natural gas is a clean source of energy, but an efficient and economical means of storing and transporting it is a challenge that is a growing research area of interest. CNTs have the potential to store natural gas at low pressures and are an economical and efficient candidate for storing and transporting natural gas. Structural defect in SWCNT improves its methane adsorption capacity. Purification of MWCNT with acids increases its methane adsorption capacity. Increasing pressure increases CNT methane adsorption capacity while increasing temperature decreases CNT methane adsorption capacity. Adsorption capacity and adsorbed gas increase with increasing MWCNT diameter. Increasing the diameter of the nanotube reduces its density. Natural gas is more absorbed in carbon nanotubes than in silicon nanotubes. The porosity of the tanks has a significant effect on the adsorption capacity (gr/gr), but affects the total adsorbed mass of the gas (gr). By reducing the porosity of the tank, the loaded mass of the adsorbent in the container increases, and as a result, natural gas storage becomes more. Adsorption capacity is a function of adsorbent, temperature, and pressure. As the loading pressure increases, the inlet and gas absorption capacity improves. The adsorption capacity of the bed decreases with increasing bed temperature. Optimal conditions are a combination of maximum nanotube diameter, loading pressure, minimum possible porosity, and water bath temperature in the presence of carbon nanotubes.
