Benzene pyrolysis surface carbon formation, mechanism

Mechanism of Surface Carbon Formation During the Pyrolysis of Benzene in the Presence of Hydrogen... 

The mechanism of carbon formation on polycrystalline Cu foils was studied for the pyrolysis of benzene in the presence of hydrogen. The study was carried out on a microbalance tubular flow reactor at temperatures rapging form 800 to 1050°C. The rate of surface carbon deposition was constant after an initial period during which no appreciable deposition was observed. 

On the basis of the preceding discussion, we proposed the following formation mechanism of OMCs [166], At OOO C, the products of benzene pyrolysis are known to be polycyclic aromatic hydrocarbon species, such as biphenyl, m-, p-, and o-terphenyls, and anthracene [155]. Such species first adsorb on the pore surfaces of SBA-15. Subsequently, further aromatization and carbonization of the adsorbed species takes place to form the first layer of carbon film [167,168], A layer-by-layer stacking then follows to create stacked graphene sheets. Thns, the favored direction of stacked graphene sheets is parallel to the long axis of the nanorods. Carbon deposition in the pores of the mesoporous silica template will stop when the pore size becomes smaller than the kinetic diameter of the benzene... 

Carbon fibers also can be produced by the pyrolytic deposition of hydrocarbon gases. Many hydrocarbon gases, such as methane, naphthalene, and benzene, have been used to produce carbon fibers with deposition temperatures of 1000-1200°C. Dining the pyrolysis process, thin tubes of carbon are first formed on ultra-fine particles. The tubes then grow by a surface diffusion mechanism, and the subsequent high temperature treatment with a temperature up to 2500°C results in the formation of carbon fibers with diameters ranging from 10 run to mote than 100 /im. Carbon fibers produced from hydrocarbon gases often have central hollow cores. 

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