| Pyruvic acid,as an important chemical intermediate,plays a very important role in the chemical industry and related fields,such as widely used in chemistry,pharmacy,food,agriculture and environmental protection.At present,the main methods for preparing pyruvate are biotransformation and chemical synthesis.The former mainly has disadvantages such as low conversion rate,high cost,and complicated process.The latter mainly uses lactic acid direct oxidation method and indirect oxidation method at this stage.The raw material lactic acid can be obtained by fermentation of a variety of biomass,and has the characteristics of sufficient yield and low price.Therefore,the catalytic synthesis of pyruvic acid based on lactic acid as a raw material is considered to be a green,environmentally friendly and sustainable synthetic route,which has important value for academic research and industrial application prospects.However,this route still has unsatisfactory catalyst activity,selectivity and stability,and it is urgent to make a comprehensive breakthrough through catalyst design and structure-activity relationship research.For this reason,this article relies on the concept of sustainable development and green chemistry to study the chemical reaction process of lactic acid oxidative dehydrogenation to produce pyruvic acid by means of catalytic conversion.From the aspects of the controllable preparation,characterization,theoretical calculation and catalytic activity test of the catalyst,the structure-activity relationship and reaction mechanism of the oxidative dehydrogenation of lactic acid are studied in an all-round way,and finally provide a theoretical research basis for the preparation of pyruvate from lactic acid.Bimetal oxide systems such as Cu-Co,Fe-Co,Fe-Zr,Fe-Al were synthesized by solvothermal and calcination methods,and their structures were characterized by XRD.The catalytic performance of lactic acid was tested under the conditions of 230 oC,an air flow rate of 3.0 m L/min and a feed rate of 2.0 m L/h of lactic acid with a mass fraction of 10%.The results show that the activity of Fe-Zr and Fe-Al series catalysts is significantly better than that of Cu-Co and Fe-Co catalysts.Due to the introduction of Zr and Al species,it provides acidity to the lactic acid oxidative dehydrogenation reaction,which can enhance the activity of the reaction.The P-modified Fe-Mo-O bimetallic oxide is prepared by hydrothermal synthesis and used to catalyze the oxidative dehydrogenation of lactic acid to prepare pyruvic acid.Modern analytical methods such as XRD,XPS,UV-IS,NH3/CO2-TPD,etc.were used to confirm the catalyst structure and surface properties.The results show that Mo O is highly dispersed on the surface of Fe O catalyst,and the electron transfer of Fe O-Mo O indicates that there is a strong interaction between Fe-Mo-O,which leads to the change of its oxidation properties,and the acid sites on the catalyst surface are obviously more than the basic sites,which plays an important role in the catalytic oxidative dehydrogenation of lactic acid to pyruvate.Experiments show that under this catalytic system,the oxidative dehydrogenation of lactic acid to pyruvate is the main reaction route,and a small amount of side reactions are accompanied,mainly including lactic acid decarbonylation and lactic acid dehydration.At a reaction temperature of 230 oC,the conversion rate of lactic acid can reach 88.7%,while the yield of pyruvic acid is 66.8%.And the catalyst reacted continuously for 60 h,the conversion rate of lactic acid only dropped by about 10%.α-Fe2O3 with different morphologies was synthesized by solvothermal and hydrothermal methods,which were used to catalyze the oxidative dehydrogenation of lactic acid to produce pyruvic acid.Modern analysis and characterization methods such as SEM,HRTEM,XPS were used to confirm the structure and surface properties of the catalyst.The results show that the crystal plane exposed byα-Fe2O3 is affected by the synthesis system medium and precursors,forming four different morphologies（THB,QC,HS,RC）.The catalytic performance of lactic acid was tested at 230 oC,an air flow rate of 3.0 m L/min,and a 10wt%lactic acid feed rate of 2.0 m L/h.The results show thatα-Fe2O3 catalysts with different morphologies exhibit different catalytic activities,and the order of activity is THB<QC<HS<RC.Further correlating activity and crystal planes,it is found that{001}is the active center plane.DFT theoretical calculations show that the adsorption of lactic acid on theα-Fe2O3-（001）crystal plane has a low adsorption energy of-0.39 e V,and the O ofα-OH in lactic acid and the Fe（The atop position）is combined to weaken the O-H bond,which is the most important step in the oxidative dehydrogenation of lactic acid.Under optimized reaction process conditions,the conversion rate of lactic acid and the selectivity of pyruvic acid reached 94.6% and 81.7%,respectively. |
