Effect of hydrogen pressure on detoxification of 1,2,3-trichlorobenzene by catalytic hydrodechlorination with both unsulphided and sulphided NiMoγ-Al2O3 catalyst

A process which has large potential as a disposal method of organic toxic wastes is hydrotreating. The present work has investigated the effects of hydrogen pressure on the catalytic hydrodechlorination of 1,2,3-trichlorobenzene using the unsulphided and sulphided forms of NiMo γ- Al 2 O 3 catalyst. All the experiments were carried out in a stirred autoclave at a constant temperature of 330°C and at the hydrogen pressures (kept constant during each experiment) in the range 35 ⩽ p H 2 ⩽ 100 bar. Hexadecane was used as reaction medium The experimental results allowed us to identify the reaction networks: (i) for the unsulphided form of the catalyst, there were parallel reactions to 1,2 and 1,3 dichlorobenzene. Both these species then reacting with hydrogen to form chlorobenzene, which in turn formed benzene; (ii) the sulphided form of the catalyst holds the same network but with one extra reaction from benzene to hydrocracking products. With the help of the Langmuir-Hinshelwood theory it was possible to gain an insight into the mechanism of the single reactions which form the networks: hydrogen is adsorbed according to a Langmuir-type dissociative adsorption and the rate determining step is the surface reaction. Finally it was demonstrated that the major dechlorination path of the reaction network is pressure independent with sulphided catalyst.