Preparation Of Supported Platinum Catalysts Toward Glycerol Oxidation

The output of glycerol is increasing with the massive production of biodiesel.It is meaningful to seek for suitable approaches for the effective utilization of glycerol.The selective oxidation of glycerol is an important way to achieve high value-added products,so it is extremely important to choose appropriate catalytic system to improve catalytic performance.The surface morphology,crystal phase of catalyst particles and composition of support can affect the catalytic behavior of supported catalyst.In this dissertation,aiming at preparing highly active and selective catalysts for glycerol oxidation,we focus on the catalytic performance dependence on the morphology and crystal phase of platinum nanoparticles as well as the composition of support.The main research contents and conclusions are as follow.(1)Carbon nanotubes supported platinum cubes(C-Pt)enclosed by(100)faces,platinum spheres(S-Pt)enclosed by(111)and(100)planes and platinum tetrahedrons(T-Pt)exposing(111)planes have been prepared by sol-immobilization method.The three catalysts have distinct morphologies,similar particle size,the same valence and the same surfactant used in the synthesis.Glycerol oxidation experiments showed that the conversion of glycerol oxidation catalyzed by C-Pt/CNT(51.5%)was significantly higher than those of S-Pt/CNT and T-Pt/CNT.Comparison experiments and DFT calculations show that this may be related to the different adsorption ability for oxygen,glycerol and other products on different surfaces of platinum.Compared with Pt(111),Pt(100)shows much higher adsorption energies for oxygen and glycerol and lower adsorption energies for glyceric acid and dihydroxyacetone.(2)Carbon encapsulated Pt Fe supported on carbon nanotubes with face-centered tetragonal(fct)phase have been prepared through molten salt method.And temperature control which could allow the normal fcc(face centered cubic)structure transformed to fct structure.Glycerol oxidation experiments showed that catalyst with fct phase,treated under 850?,exhibited the best activity(63.5%),which was significantly higher than those of catalyst with fcc phase and single metal catalysts prepared by the same procedure.Other than Pt/CNT,fct-Pt Fe@C/CNT exhibited favorable catalytic stability even after recycling multiple times.(3)The product selectivity to dihydroxyacetone could be promoted by Mn O2 support for platinum catalysts,in particular,this phenomenon could be observed evidently when using ?-Mn O2 as support.Moreover,under the same glycerol oxidation reaction conditions,we completely convert the main product from lactic acid(the selectivity on Au/Ce O2 was 84.1%)to glyceric acid(the selectivity was 92.6%)by adjusting the ratios of ceria and manganese oxide in Mn-Ce solid solution.This might be related to the increase of acid sites of Mn-Ce solid solution with Mn content increasing.Regulation of the proportion of each component can change the target product and increase the catalytic activity,which is important for controlling the product distribution of the glycerol oxidation reaction.