**8. Prospects of CNT as a natural gas storage device**

Carbon nanotubes have many industrial applications, but more attention is currently given to it as a material for natural gas storage. Several research studies have been conducted to investigate the adsorption behavior of methane, which is a major component of natural gas on SWCNT and MWCNT. The key to successful commercialization of CNT for gas storage is the adsorption capacity of the nanotubes at standard conditions, that is, the ratio of the volume of adsorbed natural gas to the volume of storage container (Vg/Vs). There are indications that substantial volume of methane can be stored in activated carbon pellets at atmospheric conditions, in fact an adsorption capacity of 126 Vg/Vs has been reported. Commercial development of CNT for adsorption of natural gas requires high storage gas capacity greater than 150 Vg/Vs. There are other advances in gas storage on CNT that can be leveraged on to improve the natural gas storage capacity on nanotubes. It should however be noted that a volumetric capacity of about 160 Vg/Vs for methane adsorption on SWCNT has been reported. One of the challenges facing the wide use of CNT as a major adsorbent for natural gas storage is achieving consistency in storage densities and replicable manufacturing capacity. The methods used to manufacture the carbon nanotubes that give the required capacity are quite rigorous, and research in its reproducibility is still ongoing. There is need to control the pressure, temperature, and the flow rate at which gas is efficiently filled and

released from the CNT tanks for automotive application. These conditions affect the performance of the storage system since the adsorption process is exothermic. The cost of producing, purifying, and tuning the CNT to obtain the required diameter in large quantity makes the existing methods economically viable [2].
