The Modification of Diphenyl Sulfide to Pd/C Catalyst and Its Application in Selective Hydrogenation of p-Chloronitrobenzene

In this study, diphenyl sulfide(Ph2S) was employed to prepare a series of Ph2S-modified Pd/C catalysts(Pd–Ph2S/C). Catalyst characterization carried out by Brunner–Emmet–Teller(BET), energy dispersive spectrometer(EDS), X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS) and CO chemisorption uptake measurements suggested a chemical interaction between Ph2 S and Pd. The ligand was preferably absorbed on the active site of Pd metal but after increasing the amount of Ph2 S, the adsorption of Ph2 S on Pd metal tended to be saturated and the excess of Ph2 S partially adsorbed on the activated carbon. A part of Pd atoms without adsorbing any Ph2 S still existed, even for the saturated Pd–Ph2S/C catalyst. The Pd–Ph2S/C catalysts exhibited a good selectivity of p-chloroaniline(p-CAN) in the hydrogenation of p-chloronitrobenzene(p-CNB). However,the chemisorption between Ph2 S and Pd was not so strong that part of Ph2 S was leached from Pd–Ph2S/C catalyst during the hydrogenation, which caused the decline of the selectivity of p-CAN over the used Pd–Ph2S/C catalyst.Resulfidation of the used Pd–Ph2S/C catalyst was effective to resume its stability, and the regenerated Pd–Ph2S/C catalyst could be reused for at least ten runs with a stable catalytic performance.

Adsorption and Hydrogenation Process of p-Chloronitrobenzene on Au_(20)Cluster:a DFT Study

We have systematically investigated the adsorption and hydrogenation process of p-chloronitrobenzene on Au20 cluster using density functional theory-DFT） calculations.The adsorption of two types of all species,vertical adsorption and parallel adsorption,is compared,revealing that former model is more stable than the latter,and all of the species prefer to adsorb at the vertex site.After adsorption,electrons transferred from Au20 cluster to the p-chloronitrobenzene molecule.Almost all hydrogenation processes are exothermic,and the C–Cl bond scissions are considered as the rate-limiting step for both Paths A-p-CNB→p-CAN→AN） and B-p-CNB→NB→AN） with the energy barriers of 2.62 and 2.95 e V,respectively.These suggest that the C–Cl bond scission is not easy to occur on Au20 cluster due to the high energy barrier,especially the path B.The p-chloroaniline is the main hydrogenation product catalyzed by Au20.

Embedding Pd-Cu Alloy Nanoparticles in Shell of Surface-Porous N-Doped Carbon Nanosphere for Selective Hydrogenation of p-Chloronitrobenzene

Main observation and conclusion A catalyst PdxCuy/NC in which Pd-Cu alloy nanoparticles are superficially embeded in shell of surface-porous N-doped carbon nanosphere was successfully devised for p-chloronitrobenzene(p-CNB)selective hydrogenation.Bimetal ions were loaded in shell of a m-phenylenediamine derived core-shell polymer sphere and the catalyst was obtained after calcination under reducing atmosphere.The as synthesized catalyst exhibited high selectivity in hydrogenation of p-CNB to p-chloroaniline(p-CAN)(up to 98.8%)under full conversion and the performance was basically remained after 6 cyclic experiments.The reasons for the high selectivity were discussed based on the characterization results of catalyst.The interaction between N-doped support and metal atoms affected the electron distribution in alloy,electron-deficient Pd and electron-rich Cu,and thus improved hydrogenation selectivity.In addition,the alloy nanoparticles were distributed only in the porous shell of support,which benefits to prevent side reactions.This work described a scheme for tactfully designing catalyst for selective hydrogenation,which can provide experience and inspiration for relevant works and fields.