Hydrophobic zeolites as adsorbents for removal of volatile organic compounds from air

Adsorption isotherms of 1,1,1-trichloroethane, trichloroethylene and ethanol on dealuminated Y zeolite (DAY) and silicalite were measured at 25, 100 and 175 degrees C. The isotherms for the VOCs on the zeolites are well correlated with the Langmuir model. The mechanism of VOC adsorption is by volume filling of zeolite micropores by physical adsorption, at relatively low pressures. DAY zeolite has 60-150% higher VOC adsorption capacity than silicalite due to larger pore volume of the former. Regeneration by temperature swing is thermodynamically more favorable for DAY zeolite. Due to its larger pore size, the rates of adsorption of VOC in DAY zeolite are up to one order of magnitude higher than in silicalite. The adsorption equilibrium and rate constants derived from the batch gravimetric experiments are used to predict the VOC breakthrough curves in zeolite packed adsorbers. The simulation model predicts longer breakthrough time and steeper breakthrough curves for DAY zeolite as compared to silicalite.