*2.2.3 Surface area analysis*

**Figure 3** shows N2 adsorption and desorption isotherms of NaZSM-5 h and HZSM-5 h. The adsorption–desorption isotherms for all samples were found to belong to type IV isotherm according to BET classification, showing broad hysteresis loops indicating the presence of mesopores (ø > 2.0 nm) [16].

**Figure 3.** *Isotherm adsorption–desorption curve of ZSM-5 zeolites.*

*Partial Oxidation of Methane to Methanol on Cobalt Oxide-Modified Hierarchical ZSM-5 DOI: http://dx.doi.org/10.5772/intechopen.86133*
