Preparation Of Supported Catalysts And Their Catalytic Properties

Metal colloidal catalysts have great significance in the field of catalysis for theirfascinating catalytic properties. However the tedious operation of separation andrecovery limits their practice applications. Supported catalysts have shown promisingapplications in catalysis. Chlorinated organic compounds are highly toxic and difficultto degradate in the nature environment, so we chosen chlorobenzene ando-chloronitrobenzene as test object. The thesis focused on the following aspects:Firstly, an ionic-liquid-assisted method was developed for the preparation ofplatinum metal nanoparticles supported on Al₂O₃. The result showed that, the averagesize of Pt nanoparticles did not change obviously with the increasing dose of the theionic liquid, while the nanoparticles could not be fully loaded on the carriers ifexcessive dose of ionic liquid was added; When the mass percentage of Ptnanoparticles is1%in the supported catalysts, the catalysts exhibited the highestselectivity of cyclohexane. The catalysts preferred to agglomerate when the Pt masspercentage is more than5%, as a result, catalysts’ activity and selectivity became lower.In the best case of our work, the conversion rate of o-chloronitrobenzene reached99.74%and the selectivity of cyclohexane reached86.15%.Secondly, colloidal Platinum nanoparticles were first prepared and then adsorptedto the Al₂O₃carrier. The conversion rate of o-chloronitrobenzene reached99.05%andselectivity of o-chloraniline reached84.68%. The selectivity of o-chloranilinedecreased as increasing the reaction time.By changing reaction condition, we observedthat, catalyst activity showed an upward trend as temperature or pressure increased, buttemperature and pressure had no significant effect on the selectivity; When adding Fe3+cation, the catalytic activity increased from1115h-1to1195h-1and selective jumpedfrom84.68%to92.63%; Under the same catalytic condition, the activity increased three times by adding Al₂O₃carrier at last instead of at first. The Pt/Al₂O₃catalyst wascircularly used for4times under the standard reaction condition and exhibited stableproperties.Finally, colloidal Platinum nanoparticles were first prepared and then adsorpted tothe Al₂O₃carrier. The product components were inverable as increasing the reactiontime. By changing reaction condition, we observed that, catalyst activity showed anupward trend as temperature increased; Catalyst activity increased at first and thengradually declined as pressure increased.