Construction And Catalytic Performance Of Cellulose-Based/Transition Metal Catalysts

A series of cellulose-based heterogeneous nanocatalysts were prepared by loading transition metals by a simple method,using green and resource-rich cellulose as the precursor,and the microstructure and catalytic performance of the synthesized series of nanocatalysts were comprehensively evaluated.This thesis consists of three main parts:First,a highly dispersed cellulose-based palladium(Pd)nanocatalyst(Cellulose-Pd)was prepared with cellulose as a precursor.Various characterization results showed that Pd nanoparticles(NPs)were uniformly distributed in cellulose nanoporous microspheres,with an average particle size of about 2.75 nm.In the Suzuki coupling reaction,the Cellulose-Pd catalyst exhibited excellent catalytic activity,substrate applicability and cyclability at a Pd of only 0.047 mol%.Second,because the hydroxyl group in the cellulose chain is relatively single with the metal,the metal loading rate is low,or the metal anchorage is not strong,which reduces the catalytic performance.To solve this problem,chitosan is doped in cellulose to obtain cellulose-doped chitosan nanofiber microspheres.A cellulose-doped chitosan/ruthenium nanofibrillike catalyst(Ru@N-Cellulose)was prepared by impregnation loading the transition metal ruthenium.SEM,HR-TEM,FTIR,XRD,Raman,XPS and other methods were used to characterize the structure of a series of catalysts obtained at different calcination temperatures,and the ICP results showed that the metal loading increased significantly(1.5～5.7 wt%)after the introduction of doping N.Compared with the supported catalysts with different calcination temperatures,the results show that the catalyst Ru@N-Cellulose-250 obtained by calcination temperature of 250 °C has significantly better catalytic performance than that obtained by other calcination temperature.The optimal Ru@N-Cellulose-250 catalyst was applied to the N-methylation reaction of amines,which realized the Nmethylation reaction between methanol and amine compounds under relatively mild conditions,and showed good catalytic effect regardless of whether the substituent was an electron-absorbing group or an electrongiving group,and the substrate range was wide(19 substrates),and the catalyst structure did not change significantly after five cycles.Third,in order to use cheap metals instead of precious metal Ru to achieve efficient N-alkylation reaction,cellulose-doped chitosan/manganese catalyst(Mn@Cellulose/Chitosan-800)is obtained by using cellulose-doped chitosan/manganese microspheres as the carrier and impregnation method to load cheap metal manganese.The structure of the catalyst was characterized and applied to the N-alkylation reaction of amines(aniline and benzyl alcohol)to explore its catalytic activity,substrate suitability and cycle stability.The results show that under the optimal reaction conditions,the return of the target product can reach more than 95% when the reaction temperature is 120 °C and the reaction time is36 h.The substrate has good applicability,and the target product yield is still above 85% after repeated use for 5 times.