| Lignin is one of the main components of woody biomass.As a natural aromatic polymer,it has great potential in the production of phenolic compounds.Due to the complex three-dimensional network structure and chemical heterogeneity of lignin,its high value application has been restricted,and it has been directly discharged as a by-product of the pulp and paper industry,causing serious waste of resources and environmental pollution.Acid-catalyzed depolymerization of lignin is one of the ways to achieve efficient and comprehensive utilization of lignin.Preparation of solid acid catalyst with good thermal stability and high catalytic activity is an important factor to achieve high conversion of lignin.In this paper,solid acid catalysts were prepared and used in lignin depolymerization experiments to explore the optimum process conditions.Co/m-SEP catalysts with different loadings were prepared by precipitation method,using inductively coupled plasma optical emission spectroscopy?ICP-OES?,scanning electron microscopy-X-ray energy spectroscopy?SEM-EDS?,N2isothermal adsorption and desorption,etc.The catalyst was subjected to characterization analysis.The lignin was depolymerized in a high pressure reactor,and the effects of catalyst loading and reaction temperature on the liquefaction rate of lignin were investigated.The results show that the porous structure of the support is basically unchanged after the introduction of the active metal,and the catalyst pore size is the largest when the loading is 10%.15%Co/m-SEP showed the strongest reactivity to lignin catalytic depolymerization,and its conversion rate reached 74.85%.The temperature has a significant effect on the depolymerization of lignin,and the optimum reaction temperature is 260°C.Preparation of super-solid acid Co-S2O82-/m-SEP catalyst by impregnation method using modified sepiolite as carrier,using X-ray diffraction?XRD?,NH3temperature programmed desorption?NH3-TPD?,Fourier transform Characterization of the catalyst by means of characterization such as infrared spectroscopy?FT-IR?.The lignin was depolymerized in methanol solvent to investigate the effect of active metal Co and acid ion S2O82-load and phenol on the liquefaction rate of lignin.The experimental results show that the introduction of S2O82-can significantly improve the acid strength of the sample,and the 5%Co-15%S2O82-/m-SEP catalyst can catalyze the depolymerization of lignin.Phenol as a blocking agent can stabilize the reaction intermediate,alleviate the phenomenon of repolymerization and reduce the formation of coke.Excess phenol will repolymerize with the reaction intermediate,and the liquefaction rate of lignin will decrease.When the amount of phenol is added and the reaction solvent When methanol is the same,the lignin coke rate is the lowest.The catalyst preparation method has obvious influence on its microcrystalline structure and acid strength.The preparation methods of PM-Co/m-SEP and IM-Co/m-SEP were respectively prepared by precipitation method and impregnation method.And used in lignin catalytic depolymerization experiments.The structure indicates that the catalyst prepared by the precipitation method has a large specific surface area and pore volume,and the catalyst prepared by the impregnation-calcination method has a larger pore diameter,a stronger acid strength,and a stronger reactivity to lignin depolymerization.Figure 28 table 9 reference 85... |
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