Hydrodechlorination of chlorophenols over Pt- and Co-containing ZSM-5 zeolite catalysts

Some of the chlorinated organic compounds are widely used commercially because of their advantageous chemical/physical properties or being toxic to pestiferous living substances. We have prepared and applied monometallic Co-, Pt- and bimetallic Co, Pt-ZSM-5 zeolite catalysts for hydrotreating 2- and 4-chlorophenols in the temperature range of 300-400 degrees C using a fixed-bed laboratory reactor system equipped with a gas chromatograph for analysis. In the reaction over the Pt-containing catalyst high initial conversion can be observed, the compounds transform to cyclohexanone, however, the activity of the catalyst decreases even during the 2 h reaction time. In the presence of Co- ZSM-5, the main reaction is simple hydrodechlorination resulting in phenol as the main product, and this catalyst is stable, and the activity does not change. The bimetallic catalyst combines the advantages (and disadvantages) of the monometallic samples. The hydroconversion of chlorophenols resulted in the formation of cyclohexanone with high initial selectivity. However, because of the relatively short catalyst lifetime further optimization is necessary before practical application.