Poly(Ionic Liquid)s Supported N-Heterocyclic Carbene Ruthenium Complex For Hydrogenation

Poly(ionic liquid)s(PILs)refer to a subclass of polymer containing ionic liquid(IL)structure on the repeating polymer backbones units.PILs have the properties of mechanical stability and structure versatility which derived from the IL monomer structure with the structural designability,and can be designed into porous PILs catalysts on the basis of our needs,so as to achieve high catalytic performance and recycling performance.Ruthenium carbene complex is an efficient homogeneous catalyst,but it is hard to separate from the reaction system and recycle.According to the features that imidazolium ionic liquid can be acted as a ligand,this dissertation focus on synthesizing a kind of poly(ionic liquid)supported ruthenium carbene complex catalyst with good performance in catalysis,and apply the catalyst in transfer hydrogenation of acetophenone and hydrogenation of methyl benzoate.The main works are as follows:1.A concise introduction of ionic liquid and synthesis of metal carbene complex and an overview of background of poly(ionic liquid)s and their applications and synthesis,and the researching advances for the transfer hydrogenation of acetophenone and hydrogenation of methyl benzoate2.A ruthenium complex monomer was synthesized by transmetallization method using an imidazolium ionic liquid containing dual styryl groups as raw material.The ruthenium complex monomer was used to prepared poly(ionic liquid)supported N-heterocyclic carbene ruthenium complex(PIL-Ru-1 and PIL-Ru-2)by self-polymerization or copolymerization with divinylbenzene(DVB).Both the structures and properties of the polymers were characterized by 13C MAS NMR spectra,FT-IR spectra,X-ray photoelectron spectroscopy(XPS),N2-adsorption-desorption,transmission electron microscopy(TEM),thermogravimetric analysis(TG),inductive coupled plasma emission spectroscopy(ICP-AES)and elemental analysis.It is proved that the synthesized poly(ionic liquid)supported N-heterocyclic carbene ruthenium complex is a kind of catalyst with good thermal stability and high specific surface area3.The catalytic performance of heterogeneous catalysts PIL-Ru-1 and PIL-Ru-2 and homogeneous catalyst Ru complex monomer in transfer hydrogenation of acetophenone were studied systematically,and PIL-Ru-1 was proved the highest catalytic activity catalyst among the tested catalysts.The effect of reaction time,reaction temperature and type and amount of catalyst on the transfer hydrogenation had been investigated systemically when using PIL-Ru-1 as catalyst.It was found that 2.5 mol%PIL-Ru-1 could efficiently catalyze the transfer hydrogenation with refluxing isopropanol in 6 h,and the yield of phenylethyl alcohol could reach 99%.Under optimized reaction conditions,the catalyst PIL-Ru-1 had good generalities to different substrates,and the yields reached 83-99%.The mechanism of transfer hydrogenation reaction was preliminarily explored by using in situ 1H NMR,and it was found that Ru-H species might be the catalytic activity center.The deactivation mechanism of the catalysts was studied and it was found that ruthenium nanoparticles formed on the surface of the catalysts4.The catalytic performance of hydrogenation of methyl benzoate catalyzed by poly(ionic liquid)supported ruthenium complex PIL-Ru-1 was studied.The PIL-Ru-1 was proved a better selective hydrogenation of benzene rings in methyl benzoate performance on the premise of keeping C=O stable.It was found that the yield of the methyl cyclohexanecarboxylate was 92%with PIL-Ru-1 as catalyst in optimal conditions(0.4 mol%PIL-Ru-1,130?,6 h).The recycling performance of the catalyst was also investigated,and it was found that the catalyst had good recycling performance that activity of the catalyst remained basically unchanged after 4 cycles.And the active center of the catalyst was the ruthenium nanoparticles generated in situ during the hydrogenation through the 13C NMR and TEM.