Regeneration of activated carbons saturated with benzene or toluene using an oxygen-containing atmosphere

Regeneration of activated carbons (ACs) after their use for benzene and toluene removal at low concentration was studied in an oxygen-containing atmosphere, analysing the effect of porosity of the adsorbent. Attention was paid to the effect of regeneration cycles on the adsorption capacity and surface chemistry of the AC. Results show that ACs with large mesopore volumes, together with wide micropore size distributions, are desired to achieve complete regeneration at low temperatures (250–300 °C). The effect of successive regeneration cycles under an oxygen-containing atmosphere indicates that 250 °C is suitable for regeneration of most benzene-exhausted adsorbents, whereas for toluene the process requires higher temperatures (300–350 °C). The experiments show that in the case of benzene, regeneration efficiencies remain essentially constant with the number of cycles and the achieved regeneration efficiencies are close to 100%. The slight differences in regeneration efficiencies can be explained considering changes in microporosity and surface chemistry of the AC with the cycles. For regeneration of toluene-saturated AC, the regeneration percentage only remains constant for one AC, whereas some decrease is observed for the rest. This decrease can be explained, in general, by a reduction in the narrow micropore volume with cycling.