The effect of ozone treatment on activated carbon for methane adsorption

Abstract

The consumption of natural gas, having methane as a main component, has been increased in the transportation sector. Since the storage capacity for methane via compression so called compressed natural gas (CNG) in a tank is relatively limited, the use of a porous material such as activated carbon has been suggested as an adsorbent to increase the storage capacity. Several researches have reported to modify the surface of activated carbon to increase the adsorption capacity. This work explored the possibility to use ozone to treat activated carbon. With strong oxidizing power, ozone treatment can change activated carbon properties such as surface area and pore size diameter. Moreover, these properties can play an important role in methane adsorption. The physical surface properties of treated activated carbon were characterized by FTIR and BET surface area analyzer. The results showed that the exposure time to ozone treatment directly affects the properties of activated carbon surface. Specific surface area, total pore volume, and micropore volume increase with increasing ozone treatment time until 25 min. The reaction of ozone causes degradation and excessive pitting of carbon surface leads to the higher surface area. Due to the higher surface area and pore volume, these properties lead to an increase in adsorption capacity of methane. After 25 min, the ozonation decreased surface area, micropore volume and generally increased the diameter of the pores. These lead to a decrease in adsorption capacity of methane.