The preparation of active carbons from natural materials for use in gas storage

Abstract

The repetitive treatment of monolithic pellets of coconut shell chars and peach pit chars with an air stream at relatively low temperatures, ≈450 K, followed by heating the samples to an elevated temperature in an inert atmosphere, around 1120 K, resulted in considerable weight loss. The surface of the char is most likely covered with surface oxide groups at low temperatures which are desorbed as CO and CO2 upon heating. Associated surface area increases indicate a selective activation of the char with each cycle from low to high temperature. The resulting changes in the macropore volumes of the pellets were minimized, evidence of a selective activation procedure. The activated chars show an increase in adsorption of methane on a per volume basis suggesting this cyclic activation method may be beneficial when attempting to increase storage capacity in a system where limited space is available.