New catalysts for the environmentally friendly processing of chlorinated organics

Abstract

New, high-efficiency Pd and Ni catalysts for the environmentally friendly processing of chlorinated organic waste have been prepared by laser electrodispersion (LED). The nanostructured catalysts contain ensembles of Pd and Ni nanoparticles 2 and 2.5 nm in size, respectively, and show an exceptionally high activity (above 105 (mol products)/(mol metal h)) in the gas- and liquid-phase hydrodechlorination of chlorobenzenes at t < 200°C. The activity of the Pd-based supported catalysts prepared by conventional methods is lower by approximately three orders of magnitude. Another significant advantage of the new catalysts is that they are highly resistant to poisoning under the conditions of the catalytic reaction. The structure and catalytic properties of the catalysts remain unchanged as the process is run for several days. The improved performance of the nanostructured catalysts is due to charge redistribution between clusters or between a cluster and the support. This effect is most pronounced for ∼2-nm nanoclusters at incomplete (<50%) surface coverages of the support. Making use of this effect allows the amount of metal on the support to be reduced by three orders of magnitude. This is particularly important for catalysts based on noble and rare metals. The results presented here open up new opportunities for the development of an efficient and safe technology for the processing of organochloride waste by catalytic hydrodechlorination.