New Synthetic Method And Application Of Palladium Nanocatalyst

Heterogeneous catalysis palys vital roles in bulk chemical synthesis and petrochemical manufacture and so on.As part of heterogeneous catalysis,nanocatalysis has attracted more and more attentions due to its high suface area and numerous active sites on the surface,which makes the nanocatalysts are highly reactive.The reactivity of nanocatalysts are related to its structure,composition,sharp,size and the support.For nanoparticles,the smaller size,the higher proportion of atoms on the surface,resulted in low coordination number and high free surface energy of atoms on the surface.These properties make the surface atoms tend to coordinate with other atoms to lower the free surface energy,therefore the surface atoms are reactive.Thus,synthesize small-sized nanocatalysts might be important.One of the strategies to synthesize small nanoparticle is to use high surface area solid support.This strategy need the nanoparticles highly dispersed on the support's surface to avoid the potential aggragation.These nanocatalysts usually have high reactivity but poor stability and recyclability.Another protocol is using the capping agents to stable the nanopaticles,while these nanocatalysts usually have lower reactivity.In this way,using organic porous cage as template to synthesize nanocatalysts might be able to avoid those drawbacks.In this dissertation,we start from the synthetic strategies about using soild support and capping agenets,and summarized the advantages and disadvantages of the two strategies.We also analyze the advantages to using organic porous cage to synthesize nanocatalyst.The main results of the paper are as follows:1.By using organic porous cage as template,we synthesized small-sized Pd nanoparticles(1.3 nm)through low temperature reduction.And the Pd NPs showed excellent stability,after kept in glovebox for eight months and redispersion,the size still kept the same.Notably,we confirmed that the Pd NPs might be inside the cage rather than anchored on the cage surface by ligand exchange experiment and the comparsion with other N-containing ligands synthesized nanoparticles.Notably,the nanocatalyst showed excellent selectivity in the hydrogenation of alkynes by using only 0.01 mol%catalyst under room temperature.2.By using PdNPs@cage as precursor,we support the Pd NPs on porous silica,and remove organic molecules by calcination.The supported Pd catalyst was reactive in the hydrogenation of N-containing heterocycles,and the construction of N-methylamine compounds by using paraformaldehyde as methylation reagent.The hydrogenation of N-containing heterocycles is challenging,the N-containing heterocycles have stong resonance stability,and the reactant and the reduced products can posion the catalysts,resulted in decresing reactivity.3.It should be noted that I spent 2 years in Argonne National Laboratory(USA)from 2015-2017.Utill then,I started the research about nanocatalysis.Before that,I was focused on radical trifluoromethylation reactions,and I also described some of my findings in chapter 4.In a radical reaction,the radical initiator triggerd the reaction.The mostly used radical initiators are transition metals and/or oxidants,mediators,peroxides.In chapter 4,we using the low concentration peroxide generated by NMP and O2 as radical initiator,realized the generation of CF3 radical by using CF3SO2Na as CF3 source.We also realized the synthesis of ?-trifluoromethyl alcohols by using alkenes as radical acceptor.This work might provide some new ideas for radical initiation.