Selective Hydrogenation Of Chloronitrobenzene And The Study Of Kinetics

The selective hydrogenation of chloronitrobenzene to thecorresponding chloronitroaniline has been considered to replace thechemical reduction of chloronitroaniline due to the environment. It is oneof most essential reaction in the synthesis of fine chemicals. But thedehalogenation may be together with the hydrogenation ofchloronitrobenzene. So many efforts have been focused on how tominimize to dehalogenation. Nowadays the organic solvent is widelyused in the hydrogenation of chloronitrobenzene. So it is meaningful thatmuch more study should be focused on how to improve the selectivity ofchloroaniline in organic solvent. We choose2-chloro-6-nitrotioluene（2-CNT） as the raw materials to study the catalytic hydrogenation ofchloronitrobenzene. It is found that the water addition has a promotingeffect to the hydrogenation of2-CNT over2wt%Pd/C catalyst. And theoptimized volume percent of in the solvent of ethanol is5-10%. However, selective hydrogenation of chloronitrobenzene tochloronitroaniline is usually used in the solvent of methanol or ethanol,which is flammability and waste. The melting point ofchloronitrobenzene and chloronitrobenzene are a little lower that it ispossible to carry out the hydrogenation in the solvent-free conditions. Inour work, the stability of the Pd/C catalyst in the recycling hydrogenationhas been also studied. The Pd/C catalyst could be used be many times inthe hydrogenation of2-CNT. However, the Pd/C would be inactivatedwith the increased reclycling times. The possible reason is that thecatalyst is blocked by the organic chloride compounds.The kinetics of liquid-phase hydrogenation of2-CNT in solvent-freeconditions over2wt%Pd/C catalyst have been studied in under thestirring influence eliminated. The reaction order, rate constant andapparent activation energy has been obtained. It could be concluded thatthe reaction order of2-CNT is0, H₂reaction order is1.12in thehydrogenation of2-CNT. The apparent activation energy of the reactionis60.58kJ/mol, and the frequency factor is5.66×10⁷min^-1.