Preparation Of Highly Active Molybdenum Disulfide Catalyst For Catalytic Hydrogenation Of Nitroaromatics

MoS₂ catalyst shows excellent performance in many catalytic reactions due to their unique structure and optoelectronic properties.However,it is generally believed that the active site of MoS₂ is located at the edge,and most of the planar sites are inert,so the catalytic activity of commercial bulk 2H-MoS₂ is not high.The main aspect of improving catalytic activity is to activate inert planes and increase reaction sites.In this disseration,the catalytic transfer hydrogenation of nitroaromatics on defect-rich MoS₂catalysts was systematically studied,and the reaction mechanism was explored through theoretical and experimental analysis.Then,Ni MoS catalyst was synthesized and prepared by doping Ni element,and its reaction performance for the catalytic hydrogenation of 5-nitroquinoline was studied.The main research contents and results are as follows:1.The effect of defects in MoS₂ on the catalytic transfer hydrogenation of nitroarenes was investigated.Combined with various structural characterizations such as TEM,XPS,EPR,and XAS,it is found that the density of sulfur defects can be adjusted by the intercalation of ammonium and dimethylamine cations.Depending on the size of the intercalators,the contents of sulfur defects increase with the interlayer expanding due to lattice strain,distortion,and ligand substitution.The abundant sulfur defects can expose more coordinatively unsaturated molybdenum sites to improve the catalytic efficiency,and the dependence of the catalytic activity on defects is clearly demonstrated in the catalytic transfer hydrogenation of nitrobenzene with isopropanol as the hydrogen donor.The important role of coordinatively unsaturated molybdenum sites in the hydrogenation reaction is highlighted.Combining experimental results and theoretical calculations,the molybdenum sites on the edge of defective MoS₂ can chemisorb and activate isopropanol by Mo…OH-iPr,followed by dehydrogenation of isopropanol on the adjacent sulfur sites.Active hydrogen is generated,which is the rate-determining step in kinetics because it provides reactive hydrogen that can rapidly reduce chemisorbed nitrobenzene to aniline.Defect-rich MoS₂ also has excellent stability,and can still maintain 90%conversion and99%selectivity after 5 consecutive cycles of reaction.Furthermore,defect-rich MoS₂ can efficiently and selectively hydrogenate various functionalized nitroarenes to the corresponding aniline derivatives while retaining other reducible functional groups.2.Ni-Mo-S catalyst was synthesized via a one-pot hydrothermal method.The performance of Ni-Mo-S catalyst synthesized with different Ni doping amounts,different hydrothermal time and different solvents was studied for the catalytic hydrogenation of 5-nitroquinoline.Through a series of characterizations and performance tests,it is found that the synthesized Ni-Mo-S-0.33-3catalyst has good structure and morphology.Compared with MoS₂ or NiS catalysts,the Ni-Mo-S-0.33-3 affords the obviously improved reactivity for 5-nitroquinoline hydrogenation,due to the interactions between MoS₂ and Ni S.The conversion of 5-nitroquinoline can reach96%,and the selectivity can be maintained at 99%.In addition,Ni-Mo-S-0.33-3 catalyst also has excellent stability.