Study On Synthesis And Catalytic Performance Of Copper Loaded On Ordered Mesoporous Carbon

Ordered mesoporous carbon materials (OMCs) have attracted considerable attention for their high surface area, regulated aperture size, unique pore structure and different morphology, which may result in wide applications in the fields of adsorption, separation, catalysis and electrochemistry. Nowadays, mesoporous carbon materials mainly are prepared by catalytic activated method, sol-gel carbonization method and template method. The former two preparation methods exist the problems of easily collapse of porous structure and control difficulty of pore size distribution in the process of preparation. The carbon materials were synthesized by mesoporous molecular sieve as a template, which not only replicate the space structure of template molecular sieve, but also prepare highly ordered pore structure. As considering the comples interaction between metal particles and supports, the ordered mesoporous carbon (OMCs) were employed as supports due to its chemical intertness. Through tuning the texture properties as well as the content of metal precursor and calcination temperature, a series of targeted catalysts between structure and performance. Insummary, we obtained the following results:(1) The textural properties of OMCs were modified to study the influence of physicochemical properties on catalytic performance. The sucrose pyrolyzed more completely at higher temperature, which made the C-C covalent bond stronger, thus the obtained carbon framework was more completely cross-linked and the ordering of CMK-3nanorods arrays improved. Contrary to the increase in surface area and pore volume, the unit cell dimensions of the mesostructure and the average pore size decreased as calcination temperature increased, which was a consequence of silica framework shrinkage during calcinations. In a confined space such as the silica pores, the compressive forces, which appear during the pyrolysis can be transferred to the silica framework, resulting in shrinkage of the structure. As the experiment results show,900℃was the optimal calcination temperature since CMK-3obtained at this temperature had an high surface area and highly ordered mesoporous structure.(2) As considering the comples interation between metal particles and supports, the ordered mesoporous carbon underwent different carbonization temperatures were employed as supports and Cu/CMK-3catalysts were applied in methanol oxidation carbonyl synthesis of dimethyl carbonate. As the experiment results show, the Cu nanocrystallites grew when carbonization temperature below700℃. Thanks to the spatial confinement of mesoporous, the Cu nanoparticles uniformly dispersed inside the CMK-3framework.900℃was the optimal calcination temperature since CMK-3obtained at this temperature and its activity was100.5mg·g-1·h-1.(3) With the increase of Cu species, the catalytic performance of Cu/CMK-3increased gradually. When Cu contents got to12wt.%, the catalyst exhibited a better catalytic activity, and then decreased to87.4mg·g-1·h-1when Cu contents got to18wt.%. As the Cu loading content exceeded18wt.%, Cu nanoparticles in the mesopore of CMK-3became very large and probably destroyed the CMK-3framework.(4) With the increase of calcination temperature, Cu/CMK-3catalyst CuO and carbon materials on the contact interface of oxygen and carbon atoms first produce CO, then oxygen top-down reverse diffusion and react with carbon atoms, the oxygen at high temperature rapid diffusion induced copper atoms rearrangement then migrated to the surface of the carbon materials.