Synthesis And Application Of Mesoporous Carbon-manganese Oxides Nanocomposites

Manganese atoms have different oxidation states, and can form different oxides,these manganese oxides can be applied in the catalytic reaction, adsorption, ionexchange，electrochemistry, magnetic materials, etc. Ordered mesoporous materialshave received much attention in recent years because of its large surface area andadjustable pore diameter. In this paper, we have prepared highly ordered mesoporousC-MnO composite materials and graphitization mesoporous oxidationmanganese-carbon composite materials with high surface area, using the solventvolatilization induced self-assembly method, three block copolymer F127as template,then the materials were used in catalytic performance test, and show good catalyticactivity.The thesis is composed of three chapters. The ifrst chapter is a literature review,including development and research status of manganese oxides, catalytic wetoxidation catalysts and graphitic carbon.The second chapter presents synthesis of heterogeneous coordinativelyunsaturated manganese monoxide-containing mesoporous carbon catalyst （C-MnO）.The catalysts exhibit high catalytic activity in wet oxidization of phenol （almostcomplete mineralization with an initial concentration of50mg/L at atmosphericpressure）, and stability （20times reuse without obvious activity loss and metalleaching） which take more advantages than most developed heterogeneous Fentoncatalysts. The one-pot surfactant self-assembly approach is used for the synthesis ofthe mesoporous C-MnO catalysts. Small-angle XRD，N₂sorption and TEM resultsreveal that the catalysts have the ordered2D hexagonal mesostructure, high surfaceareas （530-552m²/g），uniform pore sizes （3.3-5A nm）, large pore volumes （0.34-0.44cm³/g）； and MnO nanoparticles （sizes below12nm） are well dispersed insidecarbon pore walls with high crystallinity. The wide-angle XRD pattern reveals thepresence of cubic rock salt structure MnO, and the Mn尺-edge XAFS spectra confirms the low chemical valence and the coordination unsaturated state of Mn, Thehigh activity and stability of C-MnO catalysts maybe related to the mesostructure,carbon pore wall, and more important, the confined undercoordinative MnOnanoparticles.In Chapter3, synthesis of the partically graphitic ordered mesoporouscarbon-manganese oxides composites with high surface area is described. Three blockcopolymer F127is used as template, low-polymerized phenolic resin as carbonsources, manganese oxides as metal catalyst and silica as an additive. Through thesolvent volatilization induced self-assembly method, under low temperature, graphiticmesoporous carbon-manganese oxides composite materials with high surface areahave been synthesised. Small-angle XRD, N₂sorption and TEM results reveal that thecatalysts have the ordered2D hexagonal mesostructure, high surface areas （1014-1384m²/g），uniform pore sizes （5.4—5.8nm），large pore volumes （0.88-1.15cm³/g） which raise the utilization rate of the hole in the material. TEM results alsodemostrate that mesoporous carbon appears graphitized. Wide-angle XRD patternsdemonstrate that the presence of manganese oxides catalyst and silica additive leadto a marked enhancement of graphitic ordering in the frameworks of orderedmesoporous carbons. Raman spectra provides evidences on the increased content ofgraphiti2c sp carbon structure. Compared to different content of manganese in thecomposite materials, manganese oxides really play a part in carbon graphitization.