Abstract: By using coconut shell, almond shell, camellia nutshell and Chinese fir sawdust as raw materials, high microporosity activated carbons were prepared via the activation method of autogenic pressure at elevated temperatures without activating agent. The effects of activation temperature, activation time and system pressure on the pore structure and adsorption properties of AC were studied. The results showed that coconut shell based AC was prepared with microporisty rate of 87.8%, and the yield was 13.8% under the autogenic pressure at elevated temperatures with activation 900 ℃ kept for 6 h. The surface area, total volume, iodine value, and methylene blue value were 1194.4 m²/g, 0.528 cm³/g, 1280 mg/g, and 315 mg/g, respectively. Water vapour and carbon dioxide generated from pyrolysis of woody materials formed mixed activation agent, and the autogenous pressure effectively promote the activation reaction rate of gas and solid. The activation method of autogenic pressure at elevated temperatures was a kind of new activation method which had good economic and environmental benefits, since the production process could keep clean and convenient without any pollution and the yield of product was high.

Key words: activated carbon, autogenic pressure, microspore, self-activation