A new procedure for the treatment of organochlorinated off-gases combining adsorption and catalytic hydrodechlorination.

Environmental science & technology

PubMedID: 19368204

Elola A, Díaz E, Ordoñez S. A new procedure for the treatment of organochlorinated off-gases combining adsorption and catalytic hydrodechlorination. Environ Sci Technol. 2009;43(6):1999-2004.
A new process for the treatment of off-gases containing chlorinated pollutants is presented in this paper. The proposed process consists of the adsorption of the chlorinated compound, followed by the regeneration of the spent adsorbent using hydrogen. Therefore, this process gathers the advantages of the conventional adsorption (useful for a wide range of emissions, even those air-diluted) and the catalytic hydrodechlorination (complete destruction of the chlorinated compound, ensuring the absence of oxidized byproduct). Since it is widely accepted that palladium is the most active phase for catalytic hydrodechlorination, this metal was supported on a given adsorbent. Different materials were tested in this work for use as adsorbents in this application (NaX, KL and ZSM-5 zeolites; activated carbons and synthetic clays), using trichloroethene as model compound. Based on their adsorption capacities, measured by temperature-programmed desorption (TPD), KL and NaX zeolites (adsorption capacity of 25 and 30 micromol/g, respectively), as well as an activated carbon (30 micromol/ g), have been selected for preparing the Pd-containing adsorbents (0.5 wt% of Pd). The most selective catalyst for the total hydrodechlorination of the adsorbed chlorinated compound was the KL supported zeolite, showing full selectivity (at a 92% conversion) for total hydrodechlorination in the hydrogen treatment of the saturated material.