Pressure swing adsorption properties of activated carbon for methanol, acetone and toluene

Abstract

Volatile organic compounds (VOCs) emissions cause serious health problems and environmental pollution, and pressure swing adsorption (PSA) is one of the most promising technologies for VOCs removal and recovery. Commercial activated carbon and three typical VOCs (methanol, acetone and toluene) were selected as adsorbent and adsorbates, and the kilogram-level equipment was used to perform the pilot scale tests in order to study the application of PSA for removing and recycling VOCs in industry. The mechanism and industrial parameters including nonequilibrium time, effective length and enrichment ratio of PSA for removing and recycling VOCs has been studied by PSA experiments, static adsorption experiments, dynamic adsorption experiments, temperature programmed desorption (TPD) experiments and fitting. The results of PSA show that nonequilibrium time and effective length are related to the kinetic diameter, polarity of adsorbates and pore size, surface functional groups of adsorbents, and enrichment ratio is affected by the above factors and the boiling point of adsorbate. The horizontal comparison of three VOCs showed that methanol and acetone molecules with smaller kinetic diameter and greater polarity only need shorter effective length to removed completely by PSA. At low vacuum, the desorption performance is related to desorption activation energy (methanol 18.62 kJ/mol < acetone 22.20 kJ/mol < toluene 41.15 kJ/mol). At high vacuum, the desorption performance will be improved while the boiling point of adsorbate is lower than the temperature of fixed-bed. Based on this mechanism, the enrichment ratio of acetone can reach 2.1 under the same conditions, so that the recovery ratio of acetone became the highest among these three VOCs. This result provides new opportunities for the removal and recovery of VOCs gases.