Synthesis, Characterization And Catalytic Application Of Metal-Carbon Materials

Preparation of porous carbon materials using organic sol-gel process has recently received considerable attention. In this dissertation, a series of metal-containing carbon (M-C) xerogels or aerogels have been prepared via the direct addition of a soluble metal salt to the initial organic mixture followed by polycondensation, drying and carbonization. Catalysis for NO reduction and hydrazine decomposition by these M-C xerogels have been investigated for the first time, and the decay in activity of M-C with time on stream has been discussed. The following results have been obtained:Cu-C and Co-C xerogels were prepared by sol-gel polycondensation of phenol and formaldehyde catalyzed by Cu(NO3)2 and Co(NO3)2. N₂ adsorption and TG-Mass results showed that the textural properties of M-C xerogels depended on the metal ion introduced. As a result, the Cu-C xerogel has microporous structure and the Co-C xerogel has mesoporous structure. Both XRD and TEM revealed that the metal particles were highly dispersed into the carbon matrix, and they were in amorphous nature and buried in carbon matrix partly. In absence of O₂ in the feed stream, both the Cu-C and Co-C exhibited high activities towards NO reduction by carbon. In particular, their stabilities are much superior to those of the Cu/C and Co/C catalysts which were prepared by traditional impregnation method. Ir-C xerogel was prepared by sol-gel polycondensation of resorcinol and formaldehyde catalyzed by H2IrCl6. N₂ adsorption, SEM, TEM, XRD and TG-Mass results showed that Ir-C xerogel was microporous structure. After 1000oC carbonization, the Ir metal particles, with an average size of 1-3 nm, was highly dispersed into the carbon matrix. NO reduction tests demonstrated that in spite ofhigher activity and stability of the Ir-C than Ir/C, the deactivation of Ir-C under the presence of oxygen was inevitable due to the burning-off of the carbon matrix, even with CO as the reducing agent. On the other hand, the high activity and stability of the Ir-C for catalytic decomposition of hydrazine strongly suggested that this material would perform better in a reducing atmosphere than in an oxidizing one.By the similar method to that for Ir-C, various transition metal (Cu, Co, Ni, Fe)-carbon xerogels were successfully prepared. Cu-C is microporous, while the other three M-C xerogels are mesoporous structure. In particular, Ni-C xerogel presents the unique nanotubular structure. Catalytic tests for hydrazine decomposition demonstrated that the activity of the three mesoporous M-C xerogels followed the order of Co-C > Fe-C > Ni-C. And both the activity and selectivity towards H2 production of the M-C were higher than those of the M/C counterparts.