Liquid-phase Hydrogenation Of Chloronitrobenzene Catalyzed By Ordered Mesoporous Carbon-supported Pd

As an important raw material with broad application prospect,Chloraniline is widely applied in many fields,such as medicine,daily chemical industry,textile industry and so on.Catalytic hydrogenation of chloronitrobenzene to chloraniline is an economical and environmentally friendly process.Due to the excellent catalytic performance and the mild reaction conditions,Pd-based catalysts are often used in this reduction reaction.However,in the process of catalytic hydrogenation,the ultra-high hydrogenation ability of Pd-based catalyst facilitate the occurance of dechlorination reaction,resulting in the decreasement of the selectivity of chloraniline.Therefore,the research of high performance Pd-based catalysts are of great significance for the theoretical research and industrial application of the hydrogenation reduction of chloronitrobenzene to chloroaniline process.Therefore,in this study,ordered mesoporous carbon（OMC）and nitrogen-doped mesoporous carbon（NOMC）were prepared by soft template method,and the carbon supported Pd catalyst was prepared by impregnation method.The structure-activity relationship was systematically investigated.The results are as follows:（1）By comparing the performance of Pd-catalyzed selective hydrogenation of3-chloronitrobenzene with OMC,SBA-15,AC,and Al₂O₃as carriers,it was found that the performance of Pd/OMC catalyst was better than that of Pd/AC,Pd/SBA-15,and Pd/Al₂O₃,which may be due to the domain-limiting effect of ordered mesoporous carbon,which can effectively inhibit the agglomeration of Pd particles,while the large surface area and pore structure are conducive to diffusion and mass transfer.Moreover,compared with the straight pore channel of SBA-15,the pore structure of the body-centered cubic OMC is more helpful for the contact between the substrate and the active Pd site,which in turn improves its catalytic selective hydrogenation activity of 3-chloronitrobenzene.In addition,the pore structure and catalytic performance of the catalyst were related to the roasting temperature.With the increase in roasting temperature,the pore size and specific surface area of the carrier gradually increase;meanwhile,the surface C=O content increases,and C=O facilitates the anchoring of the Pd particles.After loading metal Pd by the impregnation method,the pore structure order of the carrier was basically unchanged.Among them,the chlorinated nitrobenzene hydrogenation performance of Pd/OMC-800 is better than that of Pd/OMC-600and Pd/OMC-700.（2）The NOMC carrier was prepared by the one-pot hydrothermal method using3-aminophenol as the precursor,and the Pd/NOMC-T catalyst was prepared by the impregnation method with Pd loading.The effects of the roasting temperature and reduction mode of the carrier on its performance in catalytic selective hydrogenation of3-chloronitrobenzene were investigated.It was found that the conversion of3-chloronitrobenzene and the selectivity of the target product by Pd/NOMC-T increased with the increase in roasting temperature;meanwhile,the Pd/NOMC-800 catalyst showed superior hydrogenation activity and selectivity than that of Pd/OMC-800.This may be attributed to the introduction of nitrogen atoms to enhance the metal-carrier interaction,which effectively inhibits the aggregation of Pd nanoparticles and regulates their electronic states,and the electron-rich Pd is beneficial to enhance the selectivity of 3-chloronitrobenzene.In addition,the conversion and selectivity of Pd/NOMC-800 remained stable after five cycles of use.