Study On Hydrolysis Of Biomass Derived Carbohydrates To Prepare Platform Compounds Catalyzed By Magnetic Carbon-Based Solid Acid

At present,the development and utilization of renewable energy has received widespread attention.Lignocellulosic biomass,as a renewable and resource-rich carbon source,was considered to be a promising renewable resource with the potential to produce high value-added chemicals.The heterogeneous acid catalysts have the advantages of high catalytic activity,good selectivity and environmental friendliness compared with the commercial homogeneous acid catalyst.Among them,carbon based solid acid has attracted much attention due to its wide source,economic and environmental protection,which is of great guiding significance for the green and efficient production of biomass platform compounds.Furfural(FF)and levulinic acid(LA),as important platform compounds for the hydrolysis and utilization of biomass,are widely used in the fields of energy,chemical industry and medicine.Biomass hydrothermal depolymerization to produce reducing sugars and then platform compounds is a hot topic in biorefining.How to achieve green and efficient production of platform compounds is a key issue that requires in-depth research.In this paper,Based on the research of self-made magnetic carbon-based solid acid(MMCSA)pretreatment hydrolysis and sugar production,the research on MMCSA catalytic hydrolysis of biomass-derived sugars to produce platform compounds was carried out.The effect and mechanism of MMCSA catalytic hydrolysis of xylose to furfural were analyzed and discussed intensively by adjusting different catalytic reaction systems and using density functional theory to calculate possible reaction pathways for furfural production,and the recycling,reuse and regeneration of MMCSA were discussed.The conditions of levulinic acid production by catalyzing the hydrolysis of glucose by MMCSA were optimized.Firstly,the process conditions of MMCSA catalytic hydrolysis of xylose to furfural were optimized under the pure water solvent system and the methyl isobutyl ketone(MIBK)/ water two-phase solvent system,and the optimal furfural production conditions were: 0.1625 g xylose,0.5g MMCSA,10 m L H2 O,40m L methyl isobutyl ketone(MIBK),reaction temperature 190 °C and reaction time 10 min.Under these conditions,the yield of furfural is best at 79.04%,and the conversion of xylose and selectivity to furfural are 99.45% and 79.14%,respectively.Secondly,the theoretical research on the reaction process under the optimal conditions for furfural production were carried out,and analyzed the main reaction pathways in the process of producing furfural from xylose by MMCSA through density functional theory calculation(DFT).The results showed that the MMCSA was separated from the reaction solution by a magnet and reused five times after the reaction,and the catalytic activity decreased significantly.The recycled MMCSA can be regenerated by concentrated sulfuric acid(98 wt%),which is comparable to the initial result catalyzed by MMCSA.Acid-base titration experiments were performed on MMCSA used five times,and acidic groups such as-SO3 H,-OH,-COOH were quantitatively determined.It was inferred that the shedding of-SO3 H was the main reason for the decline in furfural yield.At the same time,the unknown products of the reaction process were analyzed using high-performance liquid chromatography(LC-MS),and the conversion paths of xylose and furfural in the water-MIBK system were deduced.In addition,DFT calculations were performed using Gaussian software using a continuous polarization implicit solvent model(PCM).The results show that-SO3 H catalyzes the lowest free energy of activation of the furfural formation pathway,which also indicates that-SO3 H has the strongest catalytic activity in the entire system and plays a major catalytic role in the reaction.Based on the efficient conversion of xylose to furfural by adjusting the process conditions,the ability were explored,which the hydrolysis of glucose to produce levulinic acid catalyzed by MMCSA.The Orthogonal experiments were used to optimize the production parameters of levulinic acid,and the optimal process conditions for MMCSA to catalyze the hydrolysis of glucose were as follows: reaction temperature 200 °C,reaction time 2h,catalyst addition amount 1.5g,glucose addition amount 1.2g,amount of water added is 40 m L,and the optimal yield of levulinic acid is 33.18%.