Studies on adsorption isotherms and heats of adsorption of CH4 on microporous and mesoporous adsorbents

Abstract

In our present area of research we have picked CH4 as the probe. Methane is a non-polar molecule with a kinetic diameter of 3.8 Å. Methane in ‘adsorbed’ mode is being projected to be an alternative to compressed natural gas (or, CNG) as fuel in vehicular transportation. It is
therefore of paramount importance to find an adsorbent suitable enough for its storage. The two very fundamental things before any adsorbent can be claimed to a suitable one are:
(a) High storage capacity
(b) Fast kinetics
Capacity signifies amount of gas being adsorbed (usually expressed in molar units) per unit mass or volume of adsorbent sample. Kinetics on the other hand explains how fast or slow a gas molecule will be released from the adsorbed phase to the bulk gas phase in desorption
cycle. Although several research works in the recent past have published experimental data on CH4 adsorption (both gravimetry and volumetry) on various adsorbents, but a careful observation would indicate ambiguity. Data published for same experimental conditions on
similar adsorbent surfaces varied from lab to lab. More importantly, concrete experimental data of CH4 on MOF surfaces are limited as compared to other conventional adsorbents. In our present endeavour, we clearly defined our objectives in two fronts: