Study On Activity Of Solid Carbon Catalyst To Decompose Methane To Clean Hydrogen In A Fluidized-bed Reactor

Activated carbon (AC), carbon black (CB) and carbon nanotube (CNT) was employed to catalyze methane decomposition to produce COx-free hydrogen and solid carbon in a fluidized-bed reactor. Fourier transformation infrared (FTIR), chemical quantitative titration, and x-ray diffraction (XRD) were used to study the influence of the treatment processes in concentrated nitric acid (HNO₃) and the supporting of a little amount of metal particles on the surface properties and the bulk texture of AC, CB and CNT to improve their activity in the reaction. The results showed that there was no marked change for the bulk texture of AC, CB and CNT in the treatment processes. And a large number of oxygen-containing groups, such as carboxyl and hydroxyl, could be formed on the surface of AC and CB after treatment in HNO₃, however, no such influence on that of CNT. At high temperatures, the above oxygen-containing surface groups decomposed to form the corresponding defect sites to catalyze methane decomposition. Compared with that of fresh AC and CB, the activity of them after treatment in HNO₃ was increased clearly.By comparison, AC treated with supporting Ni or Co metal particles by ion-exchange process had a better activity than that by dry impregnation process owing to the stronger interaction of metal particles with carbon atom of AC of the former. The support of Ni, Co, Pd-Ni and Pd-Co on CB could effectively increase the initial activity of fresh CB, however, the activity was decreased when Ni was supported on CNT by dry impregnation process.SEM and the temperature-programmed oxidation in air showed that carbon formed on AC and CB in the decomposition of methane was dependent on the formation conditions and was very different from AC and CB and may be assigned to poorly crystallized graphite. The amount of adsorption of Pb²⁺ and Ca²⁺ in the solution on AC with this carbon was higher than that on fresh AC.