Study On Selective Synthesis Of δ-Lactone,Formate And Formamides With CO₂ Catalyzed By Nano Palladium

Using CO2 as an economical C1 source for the synthesis of value-added products and liquid fuels has received considerable attention because CO2 is an abundant,low cost,nontoxic and renewable feedstock.δ-Lactone,formates and formamides have been widely used in the fields of medicine,chemical engineering,and energy.However,there are still some problems in the current synthesis methods of these compounds via conversion of CO2,such as low selectivity,harsh reaction conditions(high temperature and high pressure),complicated catalytic system and tedious synthetic procedures.Therefore,the development of environment-friendly and efficient methods for the synthesis of these compounds under mild conditions has attracted considerable attention.In this dissertation,the conversion of CO2 toδ-lactone,formates and formamides catalyzed by nano palladium catalyst was studied.An efficient method for the selective synthesis of δ-lactone from CO2 and 1,3-butadiene catalyzed was developed by using palladium nanoparticles at 30℃,which were generated in situ in the presence of Pd(acac)2,tetrabutylammonium acetate,and PPh3 as the precatalyst,stabilizer,and reductant/ligand,respectively.The yield of δ-lactone was increased from 60%,which was the highest yield in the current report,to 86%.High conversion of 1,3-butadiene(up to 89%)and excellent selectivity(up to 96%)were also achieved.The reaction mechanism research indicated that palladium nanoparticles(1.90 ± 0.39 nm)were active species.The PdNPore catalysts were prepared from different prealloyed ingots,and structures of PdNPore catalysts were systematically characterized by scanning electron microscopy,transmission electron microscopy,X-ray diffraction and other characterization methods.The Al content in the ingot would affect the structure and catalytic activity of PdNPore.The PdNPore-1 catalyst prepared from Pd10Al90(atomic ratio),exhibited high catalytic activity for CO2 hydrogenation to formate.Formate was obtained with a yield of 86%with 1,8-diazabicyclo[5.4.0]undec-7-ene(DBU)as base.The mechanistic investigation showed that DBU was very important in the catalytic system.The PdNPore-1 was easily recovered and reused ten times without any obvious loss in activity,which was better than commercial palladium catalyst(Pd/C and lindlar catalyst).N-formylation of amines with CO2 catalyzed by unsupported nanoporous palladium catalyst with PhSiH3 as hydrogen source was studied under mild conditions.PdNPore-catalyzed CO2 conversion to form C-N bond enriches the reaction types of CO2 conversion catalyzed by nanoporous palladium catalyst.The corresponding formamides with different functional groups were afforded in 32%-91%yields under the optimized conditions.The reaction proceeded smoothly for primary and secondary amines without any additives under mild conditions.The catalyst was easily recovered from the catalytic system and reused ten times without any obvious loss in activity.The mechanistic investigation showed that the formic acid generated from PhSiH3 and CO2 was the important intermediate.