A Theoretical Study Of The CO₂ Reforming Of CH₄

It is insteresting to transform the CH4 and CO2 to the high value compounds, because of their low price and abundant storage. The CO2 reforming of CH4 is extensively used in the energy transference and the Fischer-Tropsch synthesis, it is an important route to utilize the natural gas. A theoretical investigation is performed on the mechanism of the CO2 thermal reforming of CH4, the supporting effect to the catalytic properties and the catalytic mechanism.Theoretical calculations have been used to investigate the thermal CO2 reforming of CH4, It is found that the first step is the CH4 dissociation into CH3 and H radicals for the chain initiation reaction. The continuing reforming reaction is the reaction of CH3 with CO2, which leads the formation of CH3O radical and one of the principal products, CO. Further degradation of CH3O via one or two step gives also CO as product. The produced hydrogen radical from the whole processes gives another principal product, H2. The CHxO reaction path is more favored than the CHx alternative.The effect of supports to the catalytic properties of Ni/MgO is investigated. It is found that the metals are inclined to form nucleus on cationic vacancies first, then they grow on the nucleus rather than form new one on regular sites and anionic vacancies. However, this is only reasonable at high temperatures, because the adsorption is controlled by kinetics at low temperatures. The supporting of Ni on MgO(001) surface is accompanied by the large charge transference and the magnetic quenching, this may change the catalytic properties of Ni catalyst.The catalysis of the four metals (Ni, Pt, Rh and Ru) of the initial steps is calculated. Taking on account of the geometrical structure, it is found that the Pt is the most virtual one to the CH4 dissociation. The higher Gibbs free energetic barrier of the CO2 dissociation than CH4 dissociation indicates the uncompetitive of the CO2 dissociation. It is also found that the CHs is preferred to react with O atom, this accounts for the main reaction path of CHXO mechanism, rather than CB, mechanism.