Preparation of Granulated Activated Carbon from Oil Pitch and Soot by a Mixed Activation Method

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The samples of granulated (2–3 mm) active carbon were prepared by the alkaline activation of a mixture of soot and oil pitch (50/50) followed by washing and drying (the first stage). At the second stage, the prepared granules were steam activated at temperatures of 700–750°C. As a result, samples with a carbon loss of 10–56% were obtained; in this case, the specific surface area increased from 423 m²/g for a sample not subjected to steam activation to 723 m²/g for a sample with a carbon loss of 56% (the specific surface area increased by 70%). An analysis of the dependences of the specific surface area and strength on the carbon loss showed that both pitch coke and the material of soot particles reacted with water vapor in the course of activation. Taking the first order of reaction with respect to water vapor, we determined the apparent kinetic constants of the rate equation of a reaction of water vapor with the material of carbon granules. The low activation energy (202 kJ/mol) indirectly indicated a high reactivity of the granules obtained; this allowed us to perform steam activation at a temperature 100–150°С lower than that in the case of traditional activated carbons.