Effect of chemisorbed oxygen on char reactivity

Many workers have demonstrated that a substantial amount of oxygen can be chemisorbed to form oxide layers on carbon surfaces in the course of chemical oxidation reactions (Laine et al., 1963; Walker et al., 1965; Puri, 1970). This communication reports results of a set of experiments conducted to explore how such deposited oxygen affects the intrinsic reactivity and the pore enlargement in a series of bituminous chars. The five char samples used in this study were prepared from a single coal under various pyrolysis conditions, following the procedures set forth by Su and Perlmutter (1984) and labeled as samples B to F in the earlier work. Air oxidation of each sample was carried out at 673 K. At desired conversion levels (15, 30, 45, 60 and 75%), reaction was terminated within 1 min by purging nitrogen through the TGA reaction chamber. After 10 min without any detectable further weight loss at 673 K, the temperature of the nitrogen purge was rapidly raised to 1,223 K within 3 min and held at that temperature for 10 min. Substantial weight loss was observed during this heat treatment, most of it occurring before the temperature reached 1,173 K. Greater weight loss was observedmore » at greater conversion levels for all the chars tested.« less