The treatment of binary VOC mixtures by adsorption and oxidation using activated carbon and a palladium catalyst

The adsorption of binary thiophene-containing mixtures on activated carbon and their subsequent desorption and oxidation over a Pd/CeO₂/Al₂O₃ catalyst has been studied as a model for the treatment of dilute VOC streams by intermittent accumulation and combustion. When adsorbed together, cyclohexene and thiophene have similar breakthrough times with little tendency for one to displace the other. However the adsorption of thiophene continues beyond that of diethylamine in mixtures while thiophene is itself displaced by methylmethacrylate. Oxidation of the binary mixtures is controlled by that of thiophene which requires temperatures somewhat above 300°C for complete removal. Combustion of the other VOCs proceeds in parallel with thiophene although they react at much lower temperatures when alone. Both components of the mixtures can be removed by a system in which the VOCs are accumulated on carbon and then undergo temperature programmed desorption in air onto Pd/CeO₂/Al₂O₃ held at 350°C. However it is not possible to operate with the adsorbent and catalyst together since desorption then occurs before the catalyst reaches working temperature.