Steam regeneration of acetone and toluene in activated carbon and dealuminated Y-zeolite beds

The dynamics of steam regeneration in activated carbon and dealuminated Y-zeolite (DAY-zeolite) beds was studied to recover acetone and toluene from effluent gases. Due to the higher adsorption capacity of acetone on both adsorbents, the desorption breakthrough of toluene was faster than that of acetone, but the breakthrough shape of acetone was steeper than that of toluene. The variation in breakthrough time as a function of steam flow rate was less in the activated carbon bed than in the DAY-zeolite bed. The inside temperature profiles during regeneration showed stepwise shapes. A temperature plateau was observed near 355 K for toluene, which is lower than its boiling temperature and azeotrope. A temperature plateau for acetone occurred near 330 K, near its boiling temperature. The duration of the temperature plateau at the bed end corresponded with the time period of high desorption concentration during acetone desorption; for toluene, plateau duration was shorter than the duration of high desorption concentration. The maximum effluent concentration of toluene reached only 80% of the feed concentration, while that of acetone was almost 100%. Therefore, the water-miscibility of the adsorbate was an important factor in steam regeneration.