Study On The Catalytic Depolymerization Of Lignin And Model Substances By Ni-Ce/BC

The worldwide fossil energy dilemma and the environmental pollution caused by fossil fuel combustion have prompted the development of alternative sustainable energy sources.As the only naturally occurring renewable aromatic biopolymer,the conversion of lignin into liquid fuels and high value-added fine chemicals to alleviate the energy crisis is considered a proven strategy by many researchers.However,due to its complex lignin structure,the obtained lignin depolymerization products are complex and diverse,failing to achieve enrichment of several or one class of substances,thus making its further utilization difficult.Therefore,there is an urgent need for an effective catalyst that can take into account the efficiency of lignin catalytic depolymerization while achieving enrichment of the depolymerized products.Based on the efficient exploitation of lignin,this study designed and prepared biomass-derived carbon-loaded Ni and Ce catalysts,which successfully realized the efficient targeted catalytic conversion of lignin and explored the conformational relationships of the catalysts,as follows.（1）A series of Ni-Ce/BC catalysts were designed and prepared to construct a synergistic catalytic mechanism between metal interfacial sites and acidic sites.By coupling the aqueous-phase glycerol reaction system,under the optimal reaction conditions（280℃,4 h）,the lignin was converted efficiently,obtaining a liquid product yield of 59.02%and achieving high selectivity for guaiacol and 4-alkyl guaiacol with yields of 128.39 and 136.28 mg/g lignin,respectively.Analytical techniques such as N₂adsorption-desorption,XRD,Raman,HRTEM,XPS,EPR,FT-IR,NH₃-TPD and Py-IR were used to elucidate the microscopic fine structural properties of the catalysts（pore structure,crystal phase composition,microstructure,surface chemical valence,acid distribution,etc.）,and the influence of the catalysts on the structural evolution of lignin was revealed by GC-MS and 2D-HSQC NMR of the obtained monomer product distribution.The effects of process conditions（temperature,time,solvent）on the lignin depolymerization properties were also investigated.（2）In addition,2-phenoxy-1-phenylethanol was used as theβ-O-4 bond model compound,and the kinetic analysis revealed that the synergistic effect of O_V and BAS on the 3Ni-Ce/BC catalyst significantly reduced the bond dissociation energy and apparent activation energy of theβ-O-4 bond.The conversion pathways of the dimeric model compounds were also deduced in conjunction with the product distribution,and this was used as a basis to rationalize the possible catalytic depolymerization mechanism of lignin.Figure[35]Table[7]Reference[113]...