Study Of O-chloronitrobenzene Selectivity Hydrogenation

Aromatic chloroamines are important intermediates for dyes,drugs,herbicides,and pesticides.Traditionally,the aromatic chloroamine was reduced from aromatic nitro compounds either by iron powder or sodium sulfide.These processes had certain disadvantages such as environmental pollution,small output,and low yield of the products.The environmental-friendly catalytic hydrogenation processes have attracted tremendous int-erest in recent years.Green environment-friendly solvent-free catalytic hydrogenation processes not only resolve the volatile organic solvents on the environment pollution and health effects on the production staff,but also achieve phase separation of the product without rectification,both in theory and industry have important value.The paper researched the o-chloronitrobenzene in the liquid phase catalytic hydrogenation of o-chloroaniline and the intrinsic dynamic behavior in the condition of solvent-free.Especially stresses on the study of macroscopic kinetics of the reaction in solvent-free conditions.A 2 wt%Pd/C catalyst has been prepared by chemical impregnation and used to catalyze the hydrogenation of o-CNB to o-CAN in solvent-free conditions.the effects of temperature,pressure,amount of catalyst,stirring rate in feed on the conversion of o-CNB and the selectivity of o-CAN have been investigated with high-pressure reaction kettle.The favorable reaction condition were found to be temperature T:363?383K,hydrogen pressure P:1.0?1.2MPa,stirring rate n:900?1200 r/min,and feeding ratio o-CNB/catalyst = 200:1(m:m).Then the conversion of o-CNB reached 100%and the selectivity of o-CAN could reach higher than 99%.The kinetics of liquid-phase hydrogenation of o-CNB to o-CAN in solvent-free condition on Pd/C catalysts have been systematically studied under the stirring influence had been eliminated.The macroscopic kinetics parameters sush as reaction order,rate constant,and apparent activation energy and frequency factor have been obtained.It was concluded that the o-CNB selectivity hydrogenation is first order with respect to o-CNB,and is zero point six order with respect to hydrogen.The apparent activation energy of o-CNB is 60.82KJ/mol.The frequency factor of o-CNB is 7.2×105min-1.Based on these results,the kintics equation of o-CNB selectivity hydrogenation to o-CAN was given.According to the reaction kinetics search for receiving,two kinds of reaction mechanism have been drawn out which obey Langmuir-Hinshelwood modle.The equations are obtained in a straightforward manner subject to the assumption that there are two different kinds of active sites on the catalyst surface,which also follow Langmuir adsorption istotherm.Then derivation of the rate equation the same as the experimental result.