Study On Selective Hydrogenolysis Of Lignin Catalyzed By Highly Dispersed Ru/ZrO₂@C

The changing pace of the world’s energy structure has already stepped into the stage of qualitative change from quantitative accumulation.The rapid development of science and technology has triggered the storm all over the world,and a deep reform of the energy industry is imminent.Biomass,which is the only renewable fixed-carbon resource in nature,has been pouring into people’s vision.The whole-component utilization technology of biomass energy derived from biorefinery enables researchers to find the hope of replacing fossil energy.As a huge part of biomass,lignin is abundant,widely distributed and one of the few renewable aromatic compounds.However,due to the spatial complex structure of lignin and the disordered bonds inside,the utilization of lignin is still a big challenge.As a forceful path to break through of depolymerization technology,hydrogenolysis can converse lignin efficiently and selectively,so it is attracting increasing attention.In this study,a novel and efficient reaction system containing porous carbon composite metal oxides supported highly dispersed ruthenium catalyst（Ru/ZrO₂@C）was designed to catalyze the hydrogenolysis of lignin.The results showed that under the synergistic effect between Ru and the carrier of ZrO₂@C,the p-hydroxycinnamic acid derivative structure and H units in lignin could be selectively converted into 4-ethylphenol,a bulk and high added value petrochemical.And the structure-activity relationships among the active sites,pore structures,acid sites and the catalytic active were explored in depth.The main contents of this dissertation are as follows:（1）The ZrO₂@C was prepared using UiO-66 as the precursor,and the highly dispersed ruthenium catalyst was obtained by wet impregnation and in situ reduction process with the presence of organo-metallic salts.A catalytic system with Ru/ZrO₂@C was constructed and used in the hydrogenolysis of lignin,where the yield of monophenol reached 14.6%and 5.6%,of which was identified as 4-ethylphenol.Furthermore,this catalytic system showed good ability on the inhibition of char formation（the yield of coke was only 3.1%）.The physical and chemical properties of Ru/ZrO₂@C were characterized by TEM,BET,XPS and NH₃-TPD etc.The volcano-type relationship between the ratio of strong acid to moderate acid and the yield of the target products was established.The evolution of lignin was investigated by HSQC NMR and other techniques.It was found that the catalyst had high selectivity for the cleavage of the p CA structure and H units in lignin.（2）To further promote the catalytic activity of Ru/ZrO₂@C catalyst,a second metal was introduced,and the synergistic effect between different metals was investigated.The potential relationship between the specific surface and the yield of bio-char was established.The results demonstrated that the yield of 4-ethylphenol and monophenol was 5.9%and 15.2%,respectively,when the hydrogenolysis of lignin was conducted in the Ni-Ru/ZrO₂@C catalytic system.Importantly,the bio-char could be further inhibited（yield of 2.9%）in the presence of Ni-Ru/ZrO₂@C.In addition,we investigated the structure and formation pathway of the lignin heavy oil containing highly aggregated S units as well.