Study On The Catalytic Oxidation Of 1,2-propanediol To Lactic Acid Over Au/HAP,CuPd And CuPdAu Nano?metal

Since mankind enter the 21st century,science and technology have made great progress.Meanwhile,the traditional petrochemical energy has been greatly consumed,finding an alternative energy has become an urgent problem for scientists all over the world to solve.Biomass energy is considered as one of the solutions to the above problems.In recent years,biodiesel technology has been vigorously developed to alleviate the energy problem.At the same time,it has a serious excess capacity of polyhydroxy alcohol,which accounts for 10%of the total product.Glycerol is a chemical with high development and application value among its byproducts.Glycerol is readily hydrolyzed to obtain 1,2?propanediol.In addition,the production capacity of dimethyl carbonate in the joint production of 1,2?propanediol is seriously excessive,resulting in the oversupply of 1,2?propanediol.Therefore,It is of great significance to rationally develop the downstream products of 1,2?propanediol,which is conducive to the sustainable development of biomass energy.In this paper,Au/HAP,Cu Pd and Cu Pd Au composite catalysts were prepared by different catalyst preparation methods.The structure?activity relationship of the structure of mono,binary and ternary nano?catalyst structures on the catalytic oxidation of 1,2?propylene glycol to carboxylic acid was studied,and the change rule of the catalytic activity was discussed under different reaction conditions.On this basis,the separation of lactic acid from glycerol was studied.The specific research results are as follows:Au⁰ nano?metal catalyst supported on hydroxyapatite nanorods（Au_x/HAP）was prepared by wet chemical reduction method.Metal Au⁰ nanoparticles are well dispersed on the surface of HAP nanorods.The crystal growth of metallic Au⁰nanoparticles was inhibited by basic HAP nanorods.Au_x/HAP catalysts exhibited high catalytic activity for the oxidation of 1,2?propanediol to lactic acid and acetic acid under gaseous oxygen at a lower reaction temperature（60℃）.Under the conditions of 60℃,0.1mo L·L^?1,1,2?propanediol,0.3 mo L·L^?1 Na OH,0.0762g catalyst and 1.0 MPa O₂ pressure,the conversion of 1,2?propanediol reached 100%,and the selectivity of lactic acid reached 85.6%.However,the conversion rate of Au⁰nanoparticles is only 26.1%,and hydroxyapatite has no catalytic activity.Nano?bimetallic Cu Pd_x prepared by wet chemical reduction method was used as catalyst to catalyze the oxidation of 1,2?propylene glycol to fatty acids.Pd and Cu nanoparticles in bimetallic Cu Pd_x nanoparticles have a tendency of alloying.The catalytic activity of bimetallic Cu Pd_x nanoparticles is enhanced by the interaction between Pd nanoparticles and Cu nanoparticles.Total selectivity of oxidation products of 1,2?propanediol was above 99%when the conversion of 1,2?propanediol was 85.9%in alkaline aqueous solution catalyzed by bimetallic nano Cu Pd₇ at the reaction temperature of 100℃for 3h.Taking Cu Pd₇ catalyst as an example,the empirical power function reaction kinetics equation simulating the catalytic reaction shows that the activation energy of the reaction is 29.4 k J mol^?1,which indicates that the bimetrial Cu Pd₇ nanoparticles have a high catalytic activity in the oxidation reaction of 1,2?propanediol with gaseous oxygen.The ternary Cu Pd Au metal catalyst was prepared by wet chemical reduction method with copper nitrate,auric chloride and palladium nitrate as precursors and polyvinyl pyrrolidone as modifier.The ternary Cu Pd Au nanometer metal is composed of Cu nanoparticles with an average particle size of 40 nm,Pd nanoparticles with an average particle size of 5 nm and Au nanoparticles with an average particle size of10nm.XRD and XPS show that Cu,Pd and Au have alloying tendency.In the oxidation of 1,2?propanediol with gaseous O₂ as oxidant and Cu Pd Au as catalyst,the conversion rate of 1,2?propanediol reached 95.9%and the selectivity of lactic acid reached 80.5%in the sodium hydroxide solution at 80^oC for 4 hours.The ternary metal catalyst with low Au and Pd content can effectively improve the conversion of1,2?propanediol and selectivity of lactic acid.