Synthesis Of Nitrogen-doped Porous Carbon Materials And Their Applications In Methyl Orange Adsorption And Transesterification Reaction

Porous carbon materials, having great advantages, like large specific surface area, abundant pore structure, heat-resistant and acid/base resistant, are widely used in the field of catalysis, adsorption and biology science. The introduction of nitrogen or other heterogeneous elements in carbon materials can further adjust their structure, surface chemical properties and electronic conductivity, thus bringing much wider application of these materials. At present, it is a very significant to design and prepare novel nitrogen doped porous carbon materials for the application in some important process of adsorption and catalytic reaction.In this work, a series of nitrogen-doped mesoporous carbon materials(NMC) with different nitrogen contents were prepared by sol–gel method. The structure and surface properties of these materials were studied by means of various characterization methods, and the adsorption behaviors of NMC materials for methyl orange(MO) were investigated. Moreover, NMC was also used as support to prepare FeOx/NMC catalysts for the application in the transesterification of diethyl carbonate with dimethyl carbonate.NMC materials with different nitrogen contents(from 9.1 to 11.3 wt.%) can be obtained by directly carbonizing sol-gel composites containing citric acid, sucrose, urea, ammonia and aluminum phosphate. The resultant NMC materials have high surface areas(from 659 m2/g to 912 m2/g), abundant pore structures as well as large number of oxygen-containing and nitrogen-containing groups.The adsorption behaviors of NMC materials for anionic dye methyl orange(MO) fit excellent for the Langmuir isothermal adsorption equation. All the materials exhibited high adsorption capacity for MO at room temperature. Their adsorption capacity can be adjusted by changing the nitrogen contents of the initial sol-gel composites. Moreover, treating the NMC material at higher temperature can significantly improve the adsorption capacity for MO. According to the results of characterization, the main features of NMC materials, like large pore size and abundant basic nitrogen-containing groups on the surface, should be related to the excellent adsorption property for MO.By using NMC as support and Fe(NO)3 as source of iron, a few FeOx/NMC catalysts were prepared, and their catalytic properties for the transesterification of diethyl carbonate with dimethyl carbonate were studied. The FeOx/NMC catalysts showed excellent catalytic activity and stability for the reaction, much better than other carbon materials supported FeOx catalysts, including carbon nanotubes and activated carbon. The presence of functional groups on the surface of NMC material should be beneficial for the high dispersion of iron oxides. The co-existence of basic center(nitrogen containing functional groups) and adjacent acidic center(iron species) on the surface of FeOx/NMC catalyst can form acid-base pairs, which can play a synergistic catalytic role in the activation of reactants to produce ethyl methyl carbonate.