Preparation Of Poly(ionic Liquid)s And Its Catalytic Performance For Selective Hydrogrnation

In chemical production,hydrogenation is not only used for refining petroleum products but also for producing fine chemicals.Among them,the research on the hydrogenation of phenylacetylene to styrene and nitrobenzene to aniline and azobenzene has important industrial value.At present,the catalysts used for hydrogenation reaction are mainly supported catalysts.Due to the high surface energy and small particle size of the active centers,aggregation and loss are prone to occur.Based on the above reasons,special supports with the function of modified metal nanoparticles were designed,supported catalysts and metal-free catalysts with rich active sites were prepared,and their catalytic performance in hydrogenation was studied.(1)For the selective hydrogenation of phenylacetylene,in this paper,a series of Pd-PILs catalysts with rich micro-mesoporous structure was constructed by Friedel-Crafts alkylation using Pd-based ionic liquid as the polymer monomer and used for the hydrogenation of phenylacetylene under mild conditions.The experimental results show that the modification of the active center by ionic liquids not only changes the electron density of Pd but also limits the shedding of the active center.In addition,the large specific surface area and rich pore structure in the polymer skeleton are beneficial to the enrichment of small molecule H₂ and the adsorption and separation of reaction substrates.The above structure enables the active center to realize the in-situ reduction at the same time,and the catalyst shows excellent catalytic activity.When the conversion of phenylacetylene reaches more than 95%,the selectivity to styrene achieves 97%.The catalyst can still maintain high activity and selectivity after five consecutive cycles.The modification of active sites and the construction of porous carriers with ionic liquids as precursors provide more possibilities for the design of high-performance supported catalysts.(2)For the selective hydrogenation of nitrobenzene,a series of hypercrosslinked ionic liquid polymers with the porous structure was obtained by Friedel-Crafts alkylation of ionic liquid[Bnmim]Cl as polymerization monomer and flexible cross-linking agent,which were used in the selective hydrogenation of nitrobenzene.The imidazole cation with electron-deficient structure in the catalyst successfully activated the hydrogen source and reaction substrate,which not only realized the complete conversion of nitrobenzene but also achieved high selectivity to aniline through the control of the hydrogen source.When ethanolamine is used as a hydrogen source,nitrobenzene can be hydrogenated even in an inert atmosphere,and the selectivity to aniline can reach 70%.When H₂ is used as a hydrogen source,nitrobenzene can be converted completely,and the selectivity to aniline can reach more than 90%.At the same time,catalysts with different anionic structures have a significant impact on their catalytic performance.And in different hydrogen source atmospheres,the catalyst still maintained stable catalytic activity and selectivity in multiple cycle experiments.This work provides more possibilities for designing hydrogenation catalysts with high catalytic performance with ionic liquids as active centers.