Synthesis of a High-Yield Activated Carbon by Air Gasification of Macadamia Nut Shell Charcoal

Macadamia nut shell charcoal was heated in an inert environment to temperatures above 1000 K (“carbonized”), reacted with oxygen ( P O 2 = 2.68−11.3 kPa) at temperatures between 525 and 586 K (“oxygenated”), and heated again in an inert environment to temperatures above 1000 K (“activated”) to produce an activated carbon. Carbons produced by this process possess surface areas and iodine numbers in the range of 400−550. Overall yields of these carbons (based on the dry, raw macadamia nut shell feed) ranged from 24 to 30 wt %. Under the conditions employed in this work, the rates of chemisorption and gasification were not mass transfer limited. Initially, the gasification reaction was first-order with respect to oxygen concentration but became independent of oxygen concentration as the surface sites of the carbon became saturated with oxygen.