Supercritical carbon dioxide regeneration of activated carbon for exhaust processing

Supercritical carbon dioxide (ScCO ₂ ) is a promising solvent for regeneration because of its high diffusivity into the microstructure of activated carbon and its ability to operate at a moderate temperature. In this study, we investigated a ScCO ₂ cleaning method of the activated carbon used in the exhaust processor of a semiconductor manufacturing process. The ScCO ₂ cleaning was carried out at temperature of 80°C, pressure of 20 MPa and regeneration time of 6.0 h. The experimental results showed the activated carbon used in the exhaust processor for a long duration could not be regenerated. Thermogravimetric analysis (TGA) showed that ScCO ₂ could remove low boiling point adsorbates (100‒400°C) but not high boiling point adsorbates (400‒900°C). Analysis of the results of ScCO ₂ cleaning in terms of a high boiling point ratio, defined as the proportion of high boiling point adsorbates, showed that regeneration rates of 90% and 80% respectively were achieved at high boiling ratios of 2.0% and 4.0%, suggesting that the high boiling point ratio could serve as an indicator of potential regeneration rate.