Synthesis And Hydrogenation Properties Of A Porous Organic Polymer Supported Precious Metal Catalyst

Recently,increasing the utilization rate of precious metals has become a research hotspot in the field of catalysis.Due to the specific structure properties as well as the various characteristics of porous organic polymers,the ultra-fine precious metal-based catalyst from the anchoring of precious metals on porous organic polymers possessed good stability and high dispersion,which led to the good catalytic activity and reusability.Based on above,this paper has carried out the following research:In order to improve the utilization rate of precious metals,combined with the various characteristics of porous organic polymers,the precious metals are supported on porous organic polymers with good structure and properties,and ultra-fine precious metal catalysts with stable properties and high dispersion are obtained,which have recently become a research hotspot in the field of catalysis.Based on this,this paper has carried out the following research:（1）The porous polymer material（PDVB-VP）with mesoporous structure was selected and the PDVB-VP was organically functional modified by ion exchange method to obtain materials PDVB-VP-I and PDVB-VP-NTF₂.The ion exchange reduction method was used to synthesize NMNPs@PDVB-VP-X（X=I,NTF₂）materials,where the metal species were loaded in the aqueous phase.Through a series of characterization analysis,we can find that the target functional group can be successfully modified in the organic skeleton of the original material by ion exchange method,and the method was illustrated to be feasible.（2）Using the ions exchange method to synthesize the PDVB-VP-I and PDVB-VP-NTF₂ materials,the as-synthesized materials were characterized by FT-IR and elemental analysis to demonstrate the successful synthesis.The metal-based catalyst with high loading amount was also obtained by simple ion exchange reduction method,which is illustrated by the results of ICP analysis.Then the characterization of TGA,BET and TEM was used to illustrate the well-stabilized mesoporous structure of the catalyst.We also found that in the Pd@PDVB-VP-NTF₂materials synthesized from Na₂PdCl₄ and PDVB-VP-NTF₂,the size of noble palladium metals was about 2.51 nm.（3）The series of NMNPs@PDVB-VP-NTF₂（NM=Au,Pt,Pd）materials were successfully synthesized,and used in the reduction reaction of p-nitrophenol.The catalytic performance of these three precious metal catalysts were tested,and showed that the performance of Pd-based catalyst was the best.Then the Pd-based catalyst continued to be explored.（4）We synthesized four Pd-based catalysts using different carriers（PDVB-VP-I,PDVB-VP-NTF₂）and different palladium sources（H₂PdCl₄,Na₂PdCl₄）,used in the selective hydrogenation reaction of quinoline and benzaldehyde.It was found that the four Pd-based catalysts possessed good catalytic performance in the quinoline hydrogenation reaction.Among them,the Pd@PDVB-VP-NTF₂ prepared by Na₂PdCl₄ and PDVB-VP-NTF₂ as carrier possessed the best catalytic efficiency.Under the conditions that the catalyst dosage was 15mg,H₂ pressure was at 1atm,reaction temperature and time were at 60^oC and 24 h,the tetrahydroquinoline can be highly selectively converted to 1,2,3,4-tetrahydroquinoline,and the yield was as high as 95%.Moreover,the stability test of the catalyst was carried out via filtration experiment and cycle experiment.The experiment results showed that the catalyst can exist stably in the organic phase,the active species was hard to leach in the reaction,and the catalyst has high catalytic activity after repeated use for 5 times.In the benzaldehyde hydrogenation reaction,the Pd@PDVB-VP-NTF₂（Na₂PdCl₄）possessed excellent catalytic performance.The reaction was carried out under the isopropanol was solvent（also was hydrogen source）,the KOH provided alkaline environment at 80^oC for 5 h in air atmosphere.The yield of benzaldehyde was as high as 90%when benzaldehyde was converted to benzyl alcohol with high efficiency.Therefore,we believe that the functional modification of the materials via ions exchange played an important role in regulating the metal dispersion and particle size under the metal loading system.The mesoporous structure materials were selected to increase the contact probability between the catalyst and the reactant molecules,therefore creating more active sites as well as providing a good space environment for the catalytic reaction.Therefore,we believed that the synthesized metal-based catalyst possessed high structural stability.