Adsorbents methane storage data

From the above data, it would appear that methane densities in pores with carbon surfaces are higher than those of other materials. In the previous section it was pointed out that to maximize natural gas or methane storage, it is necessary to maximize micropore volume, not per unit mass of adsorbent, but per unit volume of storage vessel. Moreover, a porous carbon filled vessel will store and deliver more methane than a vessel filled wnth a siliea based or polymer adsorbent which has an equivalent micropore volume fraction of the storage vessel. 

A large body of experimental data on the adsorption isotherms exists in the literature (both journal publications and commercial brochures). With the exception of methane storage, most of the data are related to purification, particularly for environmental applications. Comparing different ACFs, the amounts adsorbed are, in general, directly dependent on the BET surface area and the micropore volume of the ACF. However, the heats of adsorption on ACF are higher than those on the granulated activated carbon. This is shown in Table 5.9 for hydrocarbons and CO2. The data in Table 5.9 are taken from Kuro-Oka et al. (1984), Meredith and Plank (1967), Laukhuf and Plank (1969), and Reich et al., (1980). 

The two key factors for methane storage are micropore volume and sorbentpacking density. Optimal storage will occur when the micropore volume is maximized. However, for fast mass-transfer rates, some mesopores and macropores are also needed as feeder pores. The micropore volumes of carbons are correlated well with the BET surface areas measured with N2 at 77 K. In fact, a linear correlation was obtained for the amount of methane adsorbed at 3.5 MPa and 25 °C and the BET surface area based on the data on 35 commercial carbons (MuUhaupt et al., 1992). 

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