Dynamical adsorption and temperature-programmed desorption of VOCs (toluene, butyl acetate and butanol) on activated carbons

The elimination of solvent vapors from paint shop atmosphere and their recovery for possible re-use is a current environmental requirement. We have studied the dynamical adsorption at 23 degreesC of typical car paint solvents, i.e. toluene, butylacetate and butanol, on two microporous activated carbons. and the thermal regeneration of these carbons with hot air at 150degreesC. A sequence of seven adsorption - desorption cycles with a mixture of these solvents left the carbons with some textural changes but the adsorption capacity remained virtually unaffected. Heavy volatile compounds, proceeding from the possibly unstabilized binder, are eliminated in the course of the first adsorption-desorption runs, Differential scanning calorimetry applied to the desorption in argon of pure solvents showed that the desorption enthalpies DeltaH(des) are close to, or slightly larger than. the evaporation enthalpies DeltaH(vap) except for butanol, which exhibited a particularly high DeltaH(des) value. Temperature-programmed desorption experiments, obtained with carbon samples heated in a helium How containing oxygen traces, evidenced the desorption of numerous oxidation products. This finding may have consequences for hot air regeneration processes. (C) 2003 Elsevier Science Ltd. All rights reserved.