COMBINED SORBENT CATALYST MEDIA FOR DESTRUCTION OF HALOGENATED VOCS

Several chromium modified zeolites have been developed and tested for their ability to physisorb chlorinated VOCs (CVOCs) at ambient and the n catalytically destroy them at elevated temperatures (ca. 300 degrees C). These dual function materials, which act as both sorbents and cat alysts, are believed to be the key to implementing a new energy effici ent process for the destruction of low concentration level CVOC stream s. Data showing catalytic activity, sorptivity and other physical prop erties for Y and ZSM-5 zeolites based media are presented. A chromium exchanged ZSM-5 (Cr-ZSM-5) medium which showed superior performance ca talytically (> 95% TCE and MeCl(2) destruction at 300 degrees C) and a dequate sorption capacity (0.074 g TCE/g sorbent, 0.064 g MeCl(2)/g so rbent at 23 degrees C in the presence of humid air) was chosen for sub sequent dual function tests. These tests showed that ambient temperatu re fixed bed sorption of CVOCs followed by periodic heating of the upp er portion of the bed to catalytic temperatures (ca. 35 degrees C) wit h slow temperature ramping of the lower portion to desorb trapped CVOC s, produced a highly energy efficient cyclic process for their destruc tion. A Cr-ZSM-5 bed, which alternately stored and then destroyed CVOC from a humid 110 ppm TCE stream at a space velocity of 2400 h(-1), wa s shown to operate over a 1460 min cycle which required heating for on ly 7% of the time.