Fabrication Of Copper Catalyst Confined In Carbon Material And Its Catalytic Performance In Dimethyl Carbonate Synthesis

Nanotechnology as well as the combination of nanotechnology and catalysis have been considered as an opportunity for the development of catalytic science. Nano-catalys is based on the confinement effect have potential application value in many fields, for instant, the catalytic process can be controlled efficiently and the stability of nanopartic les in catalysis can be well improved. Core-shell nanostructure, especially the yolk-shell nanocomposite with a distinct cavity produces a spatially confined effect through encapsulation, serving a dual function for stabilizing the nanoparticles and simultaneously fully exposing the active sites. So it has captured much attention to designing such nanocomposites, however, most of synthetic methods are tedious in the previous reports.Mesoporous materials possess several unique properties, including high-specific surface area and uniform pore size, which contribute to stabilize the guest constitute with high dispersion. In this work, direct carbonation of organic-inorganic framework is used to modify the property of carbon surface, which can yield mesoporous silica-carbon nanocomposites. The confinement of the mesochannel space and the synergistic role from hybrid silica and the carbon nature of the framework lead to the formation of well-dispersed Cu nanoparticles, which will offer a good opportunity for practical application in DMC synthesis. To be specific, the work includes the following aspects.1. Carbon-based yolk-shell hybrid materials(Cu@Carbon) have been successfully synthes ized using copper-oleate complex and phenolic resin monomers as raw materials through a one-step co-pyrolysis method. The variation of synthetic parameters, such as the ammonia amount, the hydrothermal temperature, may pose an effect on the structure of Cu@Carbon material. In detail, Cu@Carbon was finally obtained through hydrothermal reaction forming the polymer intermediate followed by calcination utilizing 2,4-Dihydroxybenzoic acid and formaldehyd as the carbon precursor, ammonia as the catalyst and copper-oleate both as the soft template and the copper precursor. Comprehensive characterizations reveal that the special oleate bilayer structure belonging to Cu-oleate played a crucial role and triple efficacy for the whole process, serving as a chelating agent to form an organometallic precursor, a capping agent to prevent metal nanoparticles from conglobation as well as a soft template to produce a cavity. The resultant Cu@Carbon nanocomposite exhibits a promising catalytic properties towards DMC systhesis.2. Based on the resemblance of the preparation for metal-oleate complex, it is expected to synthesize carbon-based yolk-shell nanocomposites with different core species. When zinc-oleate and nickel-oleate were selected as the organic-metallic compound, ZnO@Carbon and NiO@Carbon nanorattles can be successfully obtained through the identical method to Cu@Carbon. The resulting composites were 500 and 400 nm in diameter, respectively, possessing good thermal stability and high specific surface.3. When compared with Cu/MC, the Cu/MSC catlayst, prepared using hybrid mesoporous silica-carbon nanocomposites as support, possesses higher Cu dispersion and better stability. After the successive five runs, the catalytic activity of Cu/MSC changes scarcely. The hybrid nature of MSC carrier positively impact the structure of carbon surface, so that the copper ions may be selectively adsorbed on the surface of silica and interact with it, while the carbon plays a role to separate them, thus enhancing the Cu dispersion.