Study On Application Of Pd(Pt) Supported Catalysts In Hydrogenation Of Chloronitrobenzene Prepared By Pulsed Laser Deposition

Halogenated anilines are important organic intermediates, which arewidely used in synthesis of dyes, drugs, herbicides, and pesticides. In thesynthesis of halogenated anilines, catalytic reduction of halogenatednitrobenzenes is the main way and the metal supported-catalysts weremainly prepared by chemical methods, such as impregnation andion-exchange. These chemical methods not only have complicatedprocedure (such as impregnation,dry,activation,reduction, etc.) but alsothe catalytic activity were affected by many preparation parameters(suchas temperature,PH,etc.). In order to overcome this drawback, a newapproach, pulsed laser deposition(PLD), was proposed for preparationmetal supported-catalyst. The metal atoms were vaporized by pulse laserto form a beam of atoms, which directly toward the surface of support.This method has only one step for the preparation of catalysts and the procedure is completely green. Also the catalyst have higherreproducibility.In this paper, we used the PLD method to prepare Pd,Pt metalsupported-catalysts, and then compared those catalysts with chemicalmethod's catalysts on studying the liquid phase hydrogenation ofchloro-nitrobenzene to produce chloro-anilines. Main points of thisdissertation are listed as follows.1. Optimized the technical parameters of the Pd-supported catalyst'sPLD process, showed that when the conditions as follows: laser's voltageat 250V, deposition system's vacumm at -0.1MPa and the support innormal temperature, the prepared catalysts exhibited higher catalyticactivity. Those Pd/CNTs(carbon nanotubes) and Pd/γ-Al₂O₃ catalystswere characterized by XRD and TEM. The results indicated that the meandiameter of metallic Pd particles were about 10nm, which weredistributed on the surface of support. Then, the process for synthesisinganilines from nitrobenzene via liquid phase hydrogenation in ethanolusing Pd/γ-Al₂O₃ as the catalyst was studied. The result shows that atmild condition of T=60℃, P=1.0MPa, n(NB)/n(Pd)=3420(V_NB=5ml), theconversion and the yield reached above 99.9% and 99.6%. when useCNTs as support, the yield reached 99.8%.2. Optimized the technical parameters of the Pt-supported catalyst'sPLD process, showed that when the conditions as follows: laser's voltage at 250V, deposition system's vacumm at -0.1MPa and the carrier innormal temperature, the prepared catalysts exhibited higher catalyticactivity for hydrogenation of o-chloronitrobenzene. The Pt/CNTs werecharacterized by XRD,TEM and XPS, indicated that the mean diameterof metallic Pt particles were about 8.5 nm, which Pt were atomic statesand equality distributed on the surface of CNTs. Then, the process forsynthesising chloroanilines from chloronitrobenzene via liquid phasehydrogenation in ethanol using Pt/CNTs as the catalyst was studied. Theresult shows that at mild condition of T=60℃, P=1.0MPa, the o-CNB'sconversion reached 99.7%, and the yield reached 99.1%. When usedγ-Al₂O₃ as support, the conversion were lower.Compared with chemical methods, the catalysts prapared by PLDmethod has a little lower activity, but better selectivity. The PLD methodhas simple and completely green procedure and it is fited for preparing allsingle metal and multicomponent alloy supported catalysts, must have agood industrial application prospect.