Production of activated carbon by waste tire thermochemical degradation with CO2

The thermochemical degradation of waste tires in a CO2 atmosphere without previous treatment of devolatilization (pyrolysis) in order to obtain activated carbons with good textural properties such as surface area and porosity was studied. The operating variables studied were CO2 flow rate (50 and 150 mL/min), temperature (800 and 900 degrees C) and reaction time (1, 1.5, 2, 2.5 and 3 h). Results show a considerable effect of the temperature and the reaction time in the porosity development. Kinetic measurements showed that the reactions involved in the thermochemical degradation of waste tire with CO2, are similar to those developed in the pyrolysis process carried out under N-2 atmosphere and temperatures below 760 degrees C, for particles sizes of 500 mu m and heating rate of 5 degrees C/min. For temperatures higher than 760 degrees C the CO2 starts to oxidize the remaining carbon black. Activated carbon with a 414-m(2)/g surface area at 900 degrees C of temperature, 150 mL/min of CO2 volumetric flow and 180 min of reaction time was obtained. In this work it is considering the no reactivity of CO2 for devolatilization of the tires (up to 760 degrees C), and also the partial oxidation of residual char at high temperature for activation (>760 degrees C). It is confirmed that there are two consecutive stages (devolatilization and activation) developed from the same process. (C) 2009 Elsevier B.V. All rights reserved.