Ms. Tam et Mj. Antal, Preparation of activated carbons from macadamia nut shell and coconut shell by air activation, IND ENG RES, 38(11), 1999, pp. 4268-4276
a novel, three-step process for the production of high-quality activated ca
rbons from macadamia nut shell and coconut shell charcoals is described. In
this process the charcoal is (i) heated to a high temperature ("carbonized
"), (ii) oxidized in air following a stepwise heating program from low (ca,
450 K) to high (ca. 660 K) temperatures ("oxygenated"), and (iii) heated a
gain in an inert environment to a high temperature ("activated"). By use of
this procedure, activated carbons with surface areas greater than 1000 m(2
)/g are manufactured with an overall yield of 15% (based on the dry shell f
eed). Removal of carbon mass by the development of mesopores and macropores
is largely responsible for increases in the surface area of the carbons ab
ove 600 m(2)/g. Thus, the surface area per gram of activated carbon can be
represented by an inverse function of the yield for burnoffs between 15 and
60%. These findings are supported by mass-transfer calculations and pore-s
ize distribution measurements. A kinetic model for gasification of carbon b
y oxygen, which provides for an Eley-Rideal type reaction of a surface oxid
e with oxygen in air, fits the measured gasification rates reasonably well
over the temperature range of 550-660 K.