Synthesis Of Pd-Al₂O₃and Pt-Al₂O₃Catalysts And Their Application In Catalytic Hydrogenation

Noble metal catalysts are used in various industrial catalytic reactions, and especiallyhave been widely used in chemical, petroleum, medicine and new energy, automotive exhaustpurification, catalytic combustion of natural gas, and other fields. However, due to the scarceresources of the noble metals, their applications are greatly limited. Therefore, on the premiseof high catalytic activity, how to reduce the cost of catalyst becomes a research focus on thesubject.This thesis mainly studied the synthesis of supported palladium and platinum catalystswith low loading, and their application in catalytic hydrogenation of aromatic nitrocompounds. In this work, a series of alumina supported Pd and Pt catalysts with low loadingwere prepared by an impregnation method, and the influence of operational conditions on thehydrogenation conversion and selectivity was investigated. Moreover, the dechlorinationmechanism and the method of inhibition of dechlorination were also preliminary studied.Studies revealed that the best reaction conditions for hydrogenation of6-chloro-3-nitrotoluene-4-sulfonic acid to6-chloro-3-amino toluene-4-sulfonic acid over Pd catalysts arethe following: reaction temperature-100oC, hydrogen pressure-3MPa, reaction time-2h, theweight percentage of catalysts-0.2%, conversion-95.35%, pH value of product solution-6.45which closes to neutral. This thesis also preliminarily investigated the influence ofdechlorination on the hydrogenation of6-chloro-3-nitro toluene-4-sulfonic acid. Theresults showed that morphine has the most significant effect on inhibition of dechlorination,and provide a guiding role for the large (trickle bed) reactor with platinum catalysts.This thesis also investigated the application of shaped alumina supported Pt catalysts inthe synthesis of6-chloro-3-amino toluene-4-sulfonic acid and aniline. The catalytichydrogenation was carried out in a trickle bed reactor. The results showed that the aluminasupported platinum catalysts not only have a good catalytic activity but also have a goodstability in the two reactions.The study of synthesis of6-chloro-3-amino toluene-4-sulfonic acid over palladium andplatinum catalysts revealed that the catalytic performance of these two kinds of catalysts isexcellent with low cost, and can be applied in industrial processes.