Preparation Of Ruthenium-based Catalyst And Its Catalytic Performance For Selective Hydrogenolysis Of Glycerol

The transformation of glycerol to propanediols(1,3-propanediol and 1,2-propanediol)is not only economic efficiency but significance in scientific investigation.Glycerol is the simplest polyol among all polyols,which is the ideal model for exploring the determining factors in influencing the selectivities in the selective hydrolysis of polyols.Ruthenium(Ru)-based catalysts have the highest catalytic activity for the hydrogenolysis of glycerol,but their drawback is that their ability to catalyze the cleavage of C-C bond is too strong,leading to a low selectivity of propanediols.It is still a big challenge to obtain high selectivity for the propanediols from glycerol over the Ru-based catalysts.The target of this thesis is to suppress the ability of Ru in catalyzing the cleavage of C-C bonds and to improve the selectivity of propanediols through modifying the interaction between metal and support as well as the interaction between metals.The "unprotected" Ru colloids are used as the precursor for the catalysts,and two kinds of Ru-based catalysts including Ru/ZSM-5 and Cu(Ni)-Ru/C bimetallic catalysts.Over two kinds of catalysts are used to investigate the reaction pathways and influencing factors on the catalytic reactions from glycerol to 1,3-propanediol and 1,2-propanediol.The main work of the thesis includes:(1)The preparation of Ru/ZSM-5 catalyst and its selective hydrogenolysis performance for glycerolRu/ZSM-5 catalysts were obtained by adsorption method with Ru colloids solution as the precursor and acid as the media,and the catalytic performance of Ru/ZSM-5 was investigated.the structure of the catalysts was characterized by HRTEM,STEM,SEM,XRD,XRF,NH3-TPD,Py-FTIR and 27 Al MAS NMR,and the results revealed that Ru nanoparticles were well supported on the ZSM-5 supports,and that the skeleton structure of ZSM-5 didn't evidently change but the acidity of the supports was modified.The results over the catalytic performance revealed that the silicon-aluminum ratio and surface acidic properties of ZSM-5 as well as the ratio of Ru/total acidic sites and catalytic reaction parameters have important impact on the selectivity of 1,3-propanediol.As the silicon-aluminum ratio is 70,aicd treatment time is 18 h and the Ru/acid sites ratio is 14.9,the selectivity of 1,3-PDO can reach 47%at the glycerol conversion of 18%.The addition of chloride ions can inhibit the hydrogenolysis of 1,3-propanediol,thereby improving its selectivity.Glycerol was converted to 1,3-propanediol on the acid-treaed Ru/ZSM-5 through the"Dehydration-Hydrogenation" route.The good synergy between the dehydration performance of ZSM-5(70)and the hydrogenation performance of Ru is the key factor to obtain high selectivity to 1,3-propanediol from glycerol.(2)The preparation of M-Ru bimetallic catalyst and its selective hydrogenolysis performance for glycerolThe bimetallic catalysts(M-Ru/C and Ru-M/C)with Ru as the active component were prepared with Ru colloids solution as the precursor,M(Cu or Ni)as the doped metal,and activated carbon as the support.The structure of the catalyst was characterized by HRTEM,AC-HAADF-STEM,H2-TPD and other characterization methods,revealing that the obtained catalysts are composed of Cu or Ni single atoms and Ru colloids;the added Cu and Ni single atoms greatly altered the hydrogen adsorptive behaviors.The catalytic results revealed that the selectivity of 1,2-PDO great2ly increased as a result of the addition of Cu or Ni single atoms.The selectivity of 1,2-PDO increased from 18%over Ru/C to 87%over Cu-Ru/C and 81%over Ni-Ru/C.The investigation on the reaction mechanism revealed that the electronic structure and geometric structure of Ru were modified with Cu or Ni single atoms,and the C-C cleavage was suppressed,and thus the selectivity of 1,2-PDO was improved.For the catalytic reaction over Cu-Ru/C,the higher hydrogen pressure led to lower conversion of glycerol as the pressure of hydrogen is higher than 1MPa,indicating that the dehydrogenation of glycerol is the rate-determining step in the "Dehydro-Dehydration-Hydrogenation" route.