Study On Coupling Hydrolyzed Lignocellulose By Magnetic Carbon-Based Solid Acid And Cellulase

The demand for fossil energy is increasing in the current social economy,and the use and exploitation of fossil resources have caused irreversible damage to the ecological environment.In addition,the non-renewability of fossil resources has become the biggest hidden danger of social and economic development.Therefore,the development and utilization of renewable energy has become the focus of attention in all countries of the world.Biomass is the only renewable carbon source on the earth,which can completely or partially replace fossil energy.The research and development of green and efficient conversion technology is a hot spot for researchers.The preparation of reducing sugar by hydrothermal depolymerization of biomass is an important direction of biorefinery,and the realization of green and efficient depolymerization of biomass is the key.Solid acids have the advantages of reusability,high selectivity and environmental friendliness compared to widely used liquid acid catalysts.The carbon-based solid acid prepared from the biomass raw material has the characteristics of wide source and low price,and is of great significance for developing a green safe and effective pretreatment process.In this paper,microcrystalline cellulose and ferric chloride were used as precursors to synthesize a magnetic carbon-based solid acid catalyst(MCSA)by impregnation-carbonization-sulfonation.The characteristics of MCSA,including the type and quantity of functional groups and the loading of magnetic Fe3O4 particles,were characterized by FT-IR,XPS,TEM,VSM,elemental analysis and acid-base titration.Using MCSA as a catalyst,the following studies were carried out:(1)Technical study on MCSA pretreatment of corncob hydrolysis.The pretreatment process parameters were optimized.The optimal pretreatment conditions were 2.5 g corncob,2.5 g catalyst,50 mL H2O,reaction temperature 160? and reaction time 20 min.Under these conditions,the yield of xylose was as high as 88.77%,the removal rates of hemicellulose and lignin were as high as 91.22%and 41.72%,respectively,and the cellulose retention rate was 90.92%.After pretreatment,the MCSA was separated from the material by a magnet and reused.The MCSA maintained high catalytic activity in the five cycles.The pretreated corncob residue was subjected to enzymatic hydrolysis,and the enzyme digestibility of corncob residue reached 94.33%under the enzyme loading of 40 FPU/g for 72h.(2)Study on in situ enzymatic hydrolysis technology.After the pretreatment,the reaction system was cooled and the pH was adjusted to 4.8.At 20 FPU/g enzyme loading,more than 90%enzymatic rate was obtained in only 24 h.After the reaction,the deactivated MCSA was separated and recovered by a magnet and regenerated.The regenerated MCSA still showed high catalytic activity,and its enzymatic hydrolysis rate decreased from 91.71%to 85.27%after five cycles.(3)Optimization of process conditions for sugarcane bagasse hydrolysis by MCSA.The response surface methodology was used to optimize the hydrolysis conditions of bagasse catalyzed by MCSA.The optimal process conditions predicted by regression model are as follows:reaction temperature of 170?,a catalyst loading of 2 g,and a water content of 50 mL.Under the above conditions,the xylose yield reached 91.62%after hydrolysis for 10 min,which was basically consistent with the predicted value of the model.The pretreated bagasse residue was subjected to enzymatic hydrolysis,and the cellulose in the bagasse residue was almost completely hydrolyzed after reacting under the enzyme loading of 40 FPU/g for 72h.In summary,the MCSA prepared in this paper has good catalytic activity,selectivity and reusability in hydrothermal catalytic corncob depolymerization,and the corncob pretreated by MCSA has good enzymatic properties.The magnetic carbon-based solid acid pretreatment coupling enzyme hydrolysis biomass technology developed by the research institute can realize the green and efficient conversion of hemicellulose and cellulose in biomass raw materials.The study significantly reduced water consumption and subsequent wastewater treatment pressure,providing a practical basis for large-scale commercial applications.