Preparation And Catalytic Hydrogenation Performance Of Pd Supported Magnetic Catalysts

Catalytic hydrogenation has been widely used in the chemical industry,petrochemical and other fields.With the development of green chemical industry,higher requirements are put forward for the recovery and reuse of catalysts.Therefore,the research based on superparamagnetic nanocatalysts has received much attention.Magnetic nano-catalyst is one of new type catalysts with magnetic recovery and high activity due to its magnetic response.In this thesis,Fe₃O₄@Si O₂/APTS@Pd,Fe₃O₄@PDA-TA@Pd,Fe₃O₄@PDA-TA@Ce O₂-Pd and Fe₃O₄@PDA-TA@Ni-Pd supported magnetic hydrogenation nanocatalysts were prepared and characterized by XRD,FT-IR,SEM-EDS,TEM,VSM,XPS and ICP.Using nitrile rubber and lignin as hydrogenation substrates,the effects of structure,content and active metal state of supported catalysts on catalytic activity were studied.The specific researches are as follows:1.Fe₃O₄@Si O₂/APTS@Pd and Fe₃O₄@PDA-TA@Pd magnetic hydrogenation nanocatalysts were synthesized.The loading amount of Pd was 2.7 wt%.The particle size ranges of 2.7wt%,particles loaded with Pd were 70～130 nm and 100～160 nm,respectively.The magnetic core Fe₃O₄ particles prepared by sol-gel method have superparamagnetism with saturation magnetization of 73 emu/g,and the nanoparticles are tightly coated by Si O₂ and PDA films with a thickness of 16 nm and 7.5 nm,respectively,with core-shell structure.XPS analysis showed that the amino groups of Pd and silane coupling agent（APTS）in Fe₃O₄@Si O₂/APTS@Pd were bound by chemical bonds,while the amino groups of Pd and o-phenolic hydroxyl groups of tannic acid in Fe₃O₄@PDA-TA@Pd were bound by chemical bonds.2.Fe₃O₄@PDA-TA@Ce O₂-Pd were prepared through a layer-by-layer synthetic strategy,the loading amounts of Ce and Pd were 1.5%and 3.2%,respectively.The particle size was 80～150 nm,and the overall particle morphology was cauliflower-shaped,and the Pd nanoparticles were well dispersed under the promotion of Ce O₂.XPS analysis showed that there are high-energy oxygen vacancies in the Ce O₂nanocrystalline structure,and there is a high ionic Pd species(Pdⁿ⁺)in the Pd spectrum,and there was a strong interaction between carrier and metal between Ce O₂ and Pd.The metal loading of Fe₃O₄@PDA-TA@Ni-Pd,Ni and Pd prepared by impregnation reduction method was 8.2 wt%and 9.7 wt%,respectively,The diameter of the microspheres is between 100 and 160 nm;Pd could be uniformly dispersed on the surface of the catalyst,while Ni showed aggregation phenomenon;XPS analysis showed that there were Pdⁿ⁺and Niⁿ⁺species in the catalyst,indicating that there was interaction between metal and carrier.3.Both Fe₃O₄@Si O₂/APTS@Pd and Fe₃O₄@PDA-TA@Pd have better catalytic effects in the hydrogenation of nitrile rubber,and hydrogenated rubbers with hydrogenation degrees of 95%and 97%were obtained respectively,in which the magnetic core modified by polydopamine-tannic acid catalyst,Pd has good stability,which was attributed to the fact that the amino and phenolic hydroxyl groups on the carrier can anchor and stabilize the active metal.Under the action of external magnetic field,the magnetic catalyst can be recycled.4.Fe₃O₄@PDA-TA@Ce O₂-Pd and Fe₃O₄@PDA-TA@Ni-Pd were used in the hydrogenolysis of benzyl phenyl ether（BPE）,a lignin model compound,and the reaction temperature had a more significant effect on its hydrogenation activity.Under the condition of hydrogen pressure 1.5 Mpa and 100℃,the conversion of BPE in Fe₃O₄@PDA-TA@Ce O₂-Pd was 33.2%,and the selectivity of toluene and phenol was42.6%and 15.3%,respectively.When the temperature was 180℃,the conversion of BPE was increased to 72.4%,and the selectivity of the two main products was 53.5%and 15.3%,respectively.When the temperature rises to 210℃,BPE was completely converted,in which phenol was hydrogenated to cyclohexanol,and the conversion of toluene and cyclohexanol was 43.4%and 44.7%respectively.The hydrogenolysis of lignin catalyzed by Fe₃O₄@PDA-TA@Ni-Pd showed that the conversion of BPE reached 100%,and the conversion of toluene,cyclohexanol and methylcyclohexane was 18.8%,42.7%and 37.8%respectively under hydrogen pressure of 1.5 MPa,210℃and 1h,indicating that the addition of Ni in Pd promoted the hydrogenation of toluene and phenol to cyclohexanol and methylcyclohexane.There are 41 pictures,11 tables and 172 references in this thesis.