Preparation Of Catalysts Based On Copper And Their Studies On The Catalytic Reduction Of P-nitrophenol

With the continuous development of industry,4-nitrophenol（4-NP）has broad application in the fields of pesticides,rubber,pharmaceuticals and plastics,because it is an important intermediate of chemical raw material.However,highly toxic 4-NP is non-degradable and has the characteristics of accumulation,which often results in mutations of genes that prompte the development of cancer.In recent years,the extensive production and use of 4-NP pose a great threat to drinking water and food safety.Therefore,it is a significantly important issue about how to eliminate 4-NP pollutants for water resources protection and food safety.With the in-depth studies of 4-NP pollutants,the researchers have found that 4-NP can be reduced by sodium borohydride to low-toxic4-aminophenol（4-AP）in the presence of special catalysts.The reduced product of 4-AP can be used as an intermediate in the synthesis of many drugs.In this study,metal-organic frameworks（HKUST-1）were synthesized firstly by using the hydrothermal method in order to remove 4-NP pollutants effectively.And then using HKUST-1 as a precursor,a new copper/carbon porous composite material（Cu/C-PC）was prepared under high-temperature pyrolysis.Their catalytic activities for the reduction of 4-NP and the structure-activity relationship were explored systematically.The detailed research contents are as follows:1. Metal-organic frameworks HKUST-1 were synthesized by the hydrothermal method and applied to the catalytic reduction of 4-NP.The morphological structure and chemical composition of HKUST-1 were explored through Scanning Electron Microscope（SEM）,Energy Dispersive Spectrometer（EDS）,X-ray diffraction（XRD）,Fourier transform infrared（FT-IR）spectroscopy and X-ray photoelectron spectroscopy（XPS）.The results of characterization indicated that the synthesized product was a sky-blue crystal with regular morphology and great crystal structure.It was composed of carbon,oxygen,copper and nitrogen,and contained various functional groups,such as Cu-O,-COO-,O-H and C-H.These results indicated that HKUST-1 had been synthesized successfully.After that,the catalytic performance of HKUST-1 for the reduction of 4-NP was investigated in detail.4-NP was reduced completely to 4-AP in 6 minutes with the presence of 0.2 mg HKUST-1and Na BH₄.According to the pseudo first-order kinetic equation,the apparent rate constant K_appof catalytic reaction was calculated to be 0.00709 s^-1.In addition,HKUST-1 was applied to remove 4-NP in tap water and fish samples.2. The Cu/C-PC catalysts were prepared through in-situ high-temperature pyrolysis of HKUST-1 under nitrogen atmosphere.The catalysts were characterized by SEM,XRD,XPS,EDS,FT-IR and so on.The results showed that Cu/C-PC was composed of a porous carbon skeleton and copper metal/copper oxide nanoparticles,and its oxygen content was much lower than that of HKUST-1.According to the XRD pattern,the relative content of Cu and Cu₂O in catalysts was calculated as 72.6%and 27.4 wt%,respectively.FT-IR spectroscopy indicated that the peak at 721 cm^-1corresponding to the C-H vibration in the1,3,5-trisubstituted benzene ring disappeared after pyrolysis,proving the successful pyrolysis of organic molecules in HKUST-1.The specific surface area and the total pore volume of Cu/C-PC catalysts were 196.7 m²/g and 0.22 cm³/g,respectively.In addition,the catalytic activity and stability of catalysts were investigated.99%of 4-NP was reduced to4-AP within 150 s with the catalysis of Cu/C-PC.The K_app,which was calculated on the basis of the pseudo first-order kinetic equation,was 0.0267 s^-1.Moreover,the reduction of4-NP by the catalyst could complete within 3 minutes till the fifth cycle.Its half-life and K_appwere 28.67 s and 0.0211 s^-1,respectively.This result further indicated the excellent catalytic activity and reusability of the Cu/C-PC.Furthermore,the catalytic activities of4-NP in tap water and honey were tested in order to verify the application ability of Cu/C-PC in actual samples.3. In order to further explore the catalytic mechanism of Cu/C-PC,the catalytic performance of Cu/C-PC-AW catalysts,Cu nanoparticles,Cu₂O nanoparticles,and Cu O nanoparticles were investigated.The Cu/C-PC-AW was porous carbon skeleton,which can be obtained by washing Cu/C-PC with Fe Cl₃and HCl.The results showed that Cu/C-PC-AW had hardly any catalytic activity;Cu,Cu₂O and Cu O nanoparticles showed good catalytic activity for 4-NP.Their K_appwere 0.0181 s^-1,0.0063 s^-1and 0.0069 s^-1,respectively.Therefore,the order was the catalytic activity of Cu/C-PC>the catalytic activity of Cu nanoparticles>the catalytic activity of Cu₂O/Cu O nanoparticles.As the content of Cu element in Cu/C-PC is much higher than that of Cu oxide,the catalytic mechanism of Cu/C-PC can be speculated that Cu in the catalyst makes a significant contribution to the reduction of 4-NP;at the same time,the synergistic effect between the highly active Cu/Cu oxide and porous carbon framework enhances the catalytic activity of Cu/C-PC,making Cu/C-PC reduce 4-NP pollutants efficiently.