Hydrogenation of nitrotoluenes controlled by the electrochemical potential of the catalyst

The hydrogenation of 2-nitrotoluene, 2,4-dinitrotoluene and 2,4,6-trinitrotoluene on Pd/C, Pt/C and Ni/SiO₂ catalysts was investigated in a liquid phase batch reactor at pressures between 0.4 and 2.5 MPa. The reaction was controlled by regulating the substrate supply in such a way that the electrochemical potential of the catalyst and, consequently, the surface concentration of active hydrogen was kept at a constant level. The observed hydrogenation rate dependence on the concentration of active surface hydrogen shows that the hydrogen activation is at least one of the rate determining steps. Additionally, controlling the reaction by the potential of the catalyst allows one to prevent dangerous feed concentrations and fast deactivation, too.