Porosity development in carbons derived from scrap automobile tires

The problem of disposal of scrap automotive tires has led to many investigations of possible processes leading to high value added products, including those yielding activated carbons. This study examines the porous nature of such carbons, and how it develops under oxidizing conditions that model “physical activation” or combustion types of conditions. The characterization of porosity is based upon information obtained from nitrogen and carbon dioxide adsorption isotherms. Up to a certain degree of conversion, remarkably similar patterns of porosity development are seen during burnoff in oxygen, carbon dioxide and nitric oxide, but this gives way to more unique behaviors in the different gases at high conversions. The implication is that there is imprinted during pyrolysis a certain pattern of porosity development that is initially followed, regardless of activation conditions (within the intrinsic chemical reaction rate controlled regime), but that this gradually gives way to development that is more heavily dictated by particular reaction conditions.