Selective Hydrogenation Catalytic Performance Of New-structured Ir-Cu Bimetallic Catalyst

As a platinum group metal,iridium exhibits excellent catalytic performance and can be widely used in electrocatalytic,catalytic hydrogenation and other fields.Now it is of great academic significance to modify of catalytic performance,and the modification of catalytic performance can be reached by modifying the carrier with small molecules or introducing another metal to regulate the catalytic performance.In this thesis,the catalytic performance of iridium nanoparticles was modified by introducing inert metal copper to study the influence of electronic effect and geometric effect on the catalytic performance of the catalyst,laying a foundation for the regulation of the catalytic performance of bimetallic catalysts.In this paper,the Catalytic hydrogenation of p-bromonitrobenzene was investigated as a model reaction.Firstly,a series of platinum group catalysts Ru/C,Rh/C,Ir/C were prepared,followed by introduction of copper to modify such catalysts to synthesize Cu/C-Ru,Cu/C-Rh,Cu/C-Ir catalysts on the catalytic hydrogenation of halonitrobenzene.The results reveal that copper has an evident influence on the catalytic performance of iridium nanocatalysts.In order to study the effect of copper on iridium nanocatalysts,we synthesized different ratios of Cu-C/Ir catalyst and Ir-C/Cu catalyst.X-ray diffraction（XRD）and transmission electron microscopy（TEM）of the two types of catalysts showed that the structure of the two types of catalysts did not change,and it was in a metallic state,which proved that the catalyst did not form an alloy.It was found by spherical electron microscopy that the scale of copper is 0.18 nm,which is a single atom substructure.For the first time,we clarified the structure of Ir-Cu catalysts.In order to study the electron transfer between iridium and copper,Ir-PVP and IrCu-PVP alloys were preared.The PVP-Ir and PVP-IrCu alloys were characterized by XPS.The binding energy of Ir in PVP-IrCu alloy was lower than that in PVP-Ir,revealing the electron transfer from copper to Ir.Then we measured the dispersion of Cu-C/Ir catalyst and Ir-C/Cu catalysts.It is found that the ratio of Cu-C/Ir catalyst to Ir-C/Cu is higher than that of the same ratio of beryllium copper catalyst.The Cu-C/Ir catalyst exposed more active sites than Ir-C/Cu,providing a basis for studying the effects of geometric effects.The experimental results of catalytic hydrogenation of p-bromonitrobenzene showed that the catalytic activity of Cu-C/Ir catalyst was lower than that of Ir/C catalyst,but the selectivity of the reaction was improved.The Ir-C/Cu catalyst activity was significantly reduced,and no aniline was formed after the reaction.In order to explain why copper has such an effect on the activity and selectivity of ruthenium nanocatalysts,we performed H₂-TPD（hydrogen temperature programmed desorption）test on the catalyst.It is found that under the same conditions,the desorption temperature of Cu-C/Ir catalyst is lower than the desorption temperature of Ir/C,indicating that the interaction of copper and iridium nanoparticles in Cu-C/Ir catalyst have weaker ability to adsorb hydrogen.The adsorption capacity is weak,resulting in a low activity and high selectivity of the Cu-C/Ir catalyst over the Ir/C catalyst.