Preparation And Performance Study Of TiO₂-based Photocatalyst For Efficient Catalytic Conversion Of Biomass Sugar Into Lactic Aci

With the wide application of lactic acid,the conversion of carbohydrate to lactic acid has attracted more and more attention.However,current biological and thermochemical conversion methods usually have limited selectivity or poor conditions.On this basis,the development of high selective conversion of glucose to lactic acid at low temperature optical driven system is the main research direction.In this study,the photothermal synergistic N-Ti O₂photothermal catalyst and N-Ti O₂/g-C₃N₄/NiFe-LDH ternary composite photomaterials were designed by modifying the Ti O₂-based photocatalyst,and these photocatalysts were applied to the conversion of biomass sugars into lactic acid.At the same time,in order to study the properties of the prepared materials,a series of characterization of the two photoreaction systems were carried out to explore the photoreaction structure-activity relationship.In addition,the mechanism of lactic acid production by photocatalysis was further discussed based on experimental results and theoretical calculations.This study provides new ideas for the efficient conversion of sugars into sustainable high value-added products and clean energy through the design of novel photocatalysts.The specific contents of the research are as follows:（1）Visible-light-driven prompt and quantitative production of lactic acid from biomass sugars over a N-Ti O₂photothermal catalyst.Using urea as nitrogen and carbon sources,a series of nitrogen/carbon enhanced photothermal synergistic N-Ti O₂photothermal catalysts were designed and synthesized using a simple sol-gel method.Under visible light,high active free radicals（e.g.,h⁺,e^-,·OH and·O₂^-）and photoinduced thermal effects were utilized to facilitate the production of lactic acid from carbohydrates.During the experiment,the activity of the synthesized Ti O₂-based photothermal catalyst was investigated and its catalytic performance was evaluated.Structure-activity analysis was conducted by XRD,AFM,UV-Vis DRS and ESR and so on.Furthermore,the photo-reaction conditions were optimized and the reaction mechanism of lactic acid production from biomass sugars was deduced by theoretical calculation.Visible-light-driven the N-Ti O₂photothermal material to catalyze the quantitative conversion of various biomass monosaccharides into lactic acid（conversion rate and yield close to 100%）under the condition of low temperature（as low as 60℃）and short time（as short as 30 min）,realizing the efficient production of organic acids from renewable biomass under green and mild conditions.（2）Relay photo/thermal catalysis enables efficient cascade upgrading of sugars to lactic acid.On the basis of N-Ti O₂photo-system,in order to reduce the reaction alkalinity and improve the optical efficiency,the heterojunction was further constructed,and the N-Ti O₂/g-C₃N₄/NiFe-LDH ternary photocatalyst with basic properties was prepared by hydrothermal method.Under the condition of high efficiency of lactic acid production,the weak base environment of NiFe-LDH regulating reaction system was used to study the properties of heterojunction composites.The size,specific surface area and spectral response capacity of the photocatalyst were analyzed by characterization methods,such as BET,XPS,PL and EIS and so on.Meanwhile,the structure-activity relationship was discussed,the optimal reaction environment were screened,and the photo-reaction mechanism was further studied.When N-Ti O₂/g-C₃N₄/NiFe-LDH heterojunction was excited by sunlight irradiation,various biomass sugars can be upgraded to lactic acid in water at60℃for a short time（≥15 min）（yield up to 99.0%）.The scale-up experiment and reusability experiment verify the possibility of scale up of the system,and the study aims to open up a new way of environmental protection and efficient catalytic conversion of biomass sugar to produce high-value platform molecular lactic acid.