REPROCESSING OF USED TIRES INTO ACTIVATED CARBON AND OTHER PRODUCTS

Landfilling used tires which are generated each year in the United Sta tes is increasingly becoming an unacceptable solution. A better approa ch, from an environmental and economic standpoint, is to thermally rep rocess the tires into valuable products such as activated carbon, othe r solid carbon forms (carbon black, graphite, and carbon fibers), and liquid fuels. In this study, high surface area activated carbons (>800 m(2)/g solid product) were produced in relatively high yields by pyro lysis of tires at up to 900 degrees C, followed by activation in CO2 a t the same temperature. The surface areas of these materials are compa rable with those of commercial activated carbons. The efficiency of th e activation process (gain in specific surface area/loss in mass) was greatest (up to 138 m(2)/g original tire) when large pieces of tire ma terial were used (similar to 170 mg). Oxygen pretreatment of tires was found to enhance both the yield and the surface area of the carbon pr oduct. High-pressure treatment of tires at low temperatures (<400 degr ees C) is an alternative approach if the recovery of carbon black or f uel oils is the primary objective.