Synthesis And Application Of Nickel And Palladium Catalysts

This article gives an overview of Raney nickel,tartaric acid modified Raney nickel asymmetric catalyst,and synthesis of noble metal nano-structure in mesoporous silicas.Based on the investigation of the literatures,this dissertation was focused on 1) synthesis,characterization of tartaric acid modified Raney nickel (TA-MRNi) catalyst and its application on asymmetric hydrogenation of methyl acetoacetate;2) hydrodedehalogenation of aromatic halid over Raney nickel catalyst; 3) synthesis,characterization and application of Pd and Au nanostructure on chitosan modified SBA-15 mesoporous silica.The main progress and research results have been obtained as follows: 1) enantio-selective hydrogenation of methyl acetoacetate over chirally modified Raney nickel catalyst;A new method of preparing a tartaric acid modified Raney nickel (TA-MRNi-NaBr) catalytic system has been studied.Raney nickel was modified with (R,R)-tartaric acid.Then,methanol,in which an appropriate amount of NaBr dissolved,was used as the hydrogenation reaction medium.This new catalytic system showed high efficiency and high durability in enantio-selective hydrogenation of methyl acetoacetate(MAA).The influence of the important modifying parameter (modifying pH) and reaction variables(solvent type,the types of inorganic salts and their amount,reaction temperature and hydrogen initial pressure) on the hydrogenation rate and optical yield were systematically investigated.The high optical yield of 85%was achieved at pressure(0.6MPa) nearly 17-fold lower than those previously used to achieve such results,and the hydrogenation rate was enhanced significantly.In addition,the improved TA-MRNi-NaBr catalyst showed comparatively high durability.The optical yield could remain about 60%till the eleventh run when 15 mg NaBr was added in every run.For comparison,the conventional TA-NaBr-MRNi catalyst was also prepared.Characterization data confirmed that compared with the conventional TA-NaBr-MRNi catalyst,the improved TA-MRNi-NaBr catalyst had lower weight ratio of Al-Ni,higher total surface area and more acid-corrosion on its surface,which could lead to the high efficiency of the TA-MRNi-NaBr catalytic system.2) hydrodedehalogenation of aromatic halid over Raney nickel catalyst Hydrodechlorination of o-Dichlorobenzene in liquid phase as model over Raney nickel catalyst has been investigated.The influence of different parameters,such as reaction solution,alkali type and the ratio to substrate,Raney nickel type are systematically studied.Using W-4 Raney nickel as catalyst,methanol as the reaction solution,NaOH as the addictive,the ratio of NaOH and Cl is 1.2,the highest efficiency can be achieved on hydrodechlorination of o-Dichlorobenzene.Several different kinds of aromatic halid selected to identify this catalytic system can be extensively used in hydrodedehalogenation.The results showed aromatic bromide is easier to hydrodedehalogenate than aromatic chloride,the substrate with electron donating group are easier to hydrodedehalogenate than electron withdrawing group.In hydrodedehalogenation of nitrochlorobenzene,the hydrogenation of-NO3 to -NH2 and hydrodechlorination of Cl performed at the same time.In addition,1,2,4-trichloro-benzene can be also successfully hydrodechlorinated over this catalytic system.3.Synthesis,characterization of Pd and Au nanostructure on chitosan modified SBA- 15 mesoporous silica.A new procedure for the preparation of Pd and Au nanostructure materials in SBA-15 mesoporous silica is reported.Vd and Au ions can be easily adsorbed within the channels of water-soluble chitosan modified SBA-15(M-Chi-SBA-15).Highly dispersed Pd,Au nanoparticles of～2-3 nm in size are obtained by reducing M-Chi-SBA-15 with NaBH₄.Au nanowires with～6 nm diameter,several hundred nanometers long can be formed by a carefully controlled thermal regime of the Au³⁺-Chi-SBA-15.X-ray diffraction,TEM,HRTEM,ICP-OES,N₂ adsorptiondesorption, XPS,TGA are applied to characterize those materials.4.The application of Pd-chitosan-SBA- 15 catalyst Pd-chi-SBA-15 made from different content of chitosan was applied to the selective hydrogenation of allyl alcohol.The results showed that Pd-9%chi-SBA-15 has the highest selectivity,while Pd-2%chi-SBA-15 has the highest TOF under 1 MPa H2 pressure.The Pd-chi-SBA-15 catalyst is very stable,the hydrogenation activity and selectivity remained in the high level even after 5 times use.Pd-9%chitosan-SBA-15 catalyst was test on the direct synthesis of H₂O₂ from H₂ and O₂,0.42 wt%yield of H₂O₂ can be achieved by using 1.6 N H₃PO₄,6×10-4 M NaBr aqueous ethanol mixture(volume ratio of 1:1) solution,at atmosphere pressure,16℃,4h.