Catalytic Hydrodechlorination of a PCB Dielectric Oil

Abstract

Results of catalytic hydrodechlorination of PCBs in a commercial dielectric oil are reported. Experimental runs were carried out in a batch reactor (300 cm3) at PH2 = 50 bar and T = 280−300−320−350 °C. Dielectric oil (2 wt %) in admixture with hexadecane (98wt %) was treated using a sulfided Ni−Mo catalyst. Dielectric oil composition is 58−60 wt % PCBs and 40−42 wt % chlorobenzenes. PCBs in the oil are mainly from penta- to nonachlorobiphenyls. Total chlorine content is 58 wt %. Liquid-phase samples were withdrawn during the reaction run and analyzed by GC-ECD and GC-FID. Destruction and removal efficiency has been evaluated in function of the operating conditions. The results show that PCBs are transformed into biphenyl and hydrochloric acid, and quite complete hydrodechlorination was accomplished in about 200 min at T = 350 °C. At lower temperatures longer reaction times are needed. The reaction organic chlorine → inorganic chlorine has been modeled, and Arrhenius parameters have been evaluated. In the absence of specific data, these values can be used to size HDCl reactors for the treatment of PCB oils.

Electrochemical oxidation of perfluorobutane sulfonate using boron-doped diamond film electrodes

“…Hydroxyl radical activation barriers this high are generally associated with reactions that do not readily occur at room temperature [27]. For example, activation energies for HO reaction with perchlorinated biphenyls (PCBs) range from 71 to 93 kJ mol -1 [28,29]. These high activation energies explain the lack of PCB ) E a = 9.3 ±3 kJ mol -1 Fig.…”

Destruction and Removal of PCBs in Waste Transformer Oil by a Chemical Dechlorination Process

“…23 Throughout the commercial PCB mixtures, the toxic PCB congeners such as PCB no. 77 (3,3',4,4'-tetraCB), 105 (2,3,3',4,4'-pentaCB), 118 (2,3',4,4',5-pentaCB), 123 (2',3,4,4',5-pentaCB) and 169 (3,3',4,4',5,5'-hexaCB) were identified.…”

Catalytic hydrotreating of 2,4′-DDT and 4,4′-DDT

“…Single hydrodechlorination reactions are generally well modeled by a first order kinetic equation, at low reactant concentration [2]. But the overall reaction of polychlorinated molecules is not necessary first order [8,9]. In this case, even if reactant concentration is low (83 ppm as sum of 2,4 -DDT and 4,4 -DDT), the fitting of experimental data in Fig.…”

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