This paper deals with the application of some chemical reaction engineering principles in order to develop a supported liquid phase reagent (SLPR) able to dechlorinate PCBs contained in highly viscous media. The reagent consists of polyethyleneglycols containing a dissolved base and a radical initiator. Recently this mixture was proposed as CDP(R)(Chemical Dechlorination Process) for PCBs detoxification. In this paper are reported several experimental tests designed to optimise configuration of reagents on inert support to dechlorinate the PCBs contained in the transformer oil. The main results are: the evaluation of optimum reagent load on support, the set up of dechlorination kinetics of commercial PCBs as AROCLOR 1260 in transformer oil tested in the 50-2500 ppm range. SLPR was tested in a “fixed-bed” as well as in “slurry” reactor configurations. The above results were used to design two mobile plants for on-site treatments.