The Preparation Of Highly Dispersed And Stable PtCo Bimetallic Catalyst And Its Performance In The Oxidation Of Glycerol

Biodiesel is one of the most common biofuels.Biodiesel production produces a large amount of by-product glycerol.Improving PtCo performance in the catalytic oxidation of glycerol to high value-added chemicals has far-reaching implications for reducing the cost of biodiesel.The structure and catalytic properties of PtCo are closely related to the preparation method.Highly dispersed and highly stable PtCo bimetallic catalysts were prepared by two methods.The structure of the catalyst was characterized by powder X-ray diffraction(XRD),physical adsorption,multi-functional imaging photoelectron spectroscopy(XPS)and field emission transmission electron microscopy(STEM).The formation mechanism of the catalyst and its catalytic activity in the oxidation reaction glycerol were studied.(1)The effects of Co2+ on the size and dispersion of Pt nanoparticles(NPs)in the hydrotalcite(HTs)lattice were investigated.The highly dispersed Pt/Co-HTs nanoclusters were prepared by controlled impregnation method.According to the analysis of a series of characterization methods,the control effect of Co2+ on the size and dispersion of Pt NPs in the hydrotalcite lattice was proved.XPS analysis confirmed the presence of electron transfer between Pt and Co2+ during the formation of Pt nanoparticles,indicating an interaction between PtCo.Another STEM analysis showed that the dispersion of Co2+ affected the size and dispersion of Pt NPs.The dispersion of Co2+ and the strong interaction between Pt and Co2+ are two key factors affecting the dispersion of Pt NPs.The size of Pt NPs in Pt/Co-HTs is significantly smaller than that of Pt NPs prepared by co-impregnation method.The conversion rate of Pt/Co-HTs catalyzed conversion of glycerol is 65%,and the activity is significantly higher than that of PtCo/HTs-C prepared by co-impregnation method.(2)A highly stable Pt@Co-NC catalyst was prepared by high temperature pyrolysis with encapsulating Pt nanoparticles in ZIF-67.The effect of encapsulated Pt NPs on the structure of ZIF-67 was explored.XRD and SEM analysis showed that encapsulation of Pt NPs did not change the structure of ZIF-67.XPS analysis showed that the encapsulated Pt interacted with Co derived from ZIF-67 after high temperature pyrolysis treatment.STEM characterization analysis indicated that Pt forms alloys or twins with Co.The catalytic activity and stability of the catalyst in the oxidation of glycerol were investigated.The activity of Pt@Co-NC catalyzed oxidative glycerol was higher than that of the other three methods(polyol reduction method,redox reaction method and sol-gel method).The conversion of glycerol reached 61%,and the main selective product was glyceraldehyde.The Pt@Co-NC catalyst showed high reusability,and the activity was not decreased after 5 cycles of use.