Preparation of Activated Carbons from Macadamia Nut Shell and Coconut Shell by Air Activation

• Published in: Industrial & engineering chemistry research Vol. 38; no. 11; pp. 4268 - 4276
• Main Authors: Tam, Man S, Antal, Michael Jerry
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.11.1999
• Subjects: 09 BIOMASS FUELS; ACTIVATED CARBON; AGRICULTURAL WASTES; CARBONIZATION; CHEMICAL ACTIVATION; Chemistry; COCONUTS; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; KINETIC EQUATIONS; NUTS; OXIDATION; Porous materials; PRODUCTION; SURFACE AREA; Scanning electron microscopy; Pyrolysis; Coconut; Vegetal by product; Activation; Raw materials; Experimental study; Queensland nut; Porous material; Vegetal waste; Characterization; Carbonization; Activated carbon; Preparation; Shell(anatomy); Gasification; Porosity; Surface area; Oxygenation; Charcoal
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/ie990346m

A novel, three-step process for the production of high-quality activated carbons 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 again in an inert environment to a high temperature (“activated”). By use of this procedure, activated carbons with surface areas greater than 1000 m2/g are manufactured with an overall yield of 15% (based on the dry shell feed). Removal of carbon mass by the development of mesopores and macropores is largely responsible for increases in the surface area of the carbons above 600 m2/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-size distribution measurements. A kinetic model for gasification of carbon by oxygen, which provides for an Eley−Rideal type reaction of a surface oxide with oxygen in air, fits the measured gasification rates reasonably well over the temperature range of 550−660 K.