Kinetics of o-chlorotoluene hydrogenolysis in the presence of 3%, 5% and 10% Pd/C catalysts

Abstract: The kinetics of o-chlorotoluene hydrogenolysis in the presence of 3%, 5% and 10% Pd/C catalysts was experimentally investigated in an alkaline –n-heptane – gaseous hydrogen system. The main product of hydrogenolysis was toluene. Kinetic characteristics for the reaction were obtained at temperatures of 20, 40 and 60°C at atmospheric pressure of hydrogen for all catalysts; the effectiveness of the latter in o-chlorotoluene hydrogenolysis was compared. The pseudo-zero-order rate constants and times of 90% conversion for each of the catalysts at 40 and 60°C were quite similar. The overall kinetic constants were obtained assuming the Langmuir–Hinshelwood mechanism. The activation energies of o-chlorotoluene hydrogenolysis for these catalysts were calculated. The selectivity of the reacting system was evaluated in competitive experiments with o-chlorotoluene, 1,2-dichlorobenzene and 4-chlorobiphenyl. The stability of the catalysts in a hydrogenolytic environment was tested. [Copyright &y& Elsevier]