The kinetic model of formation of nanofibrous carbon from CH4–H2 mixture over a high-loaded nickel catalyst with consideration for the catalyst deactivation

A mathematical model is suggested for the process of formation of nanofibrous carbon from the mixture of methane and hydrogen over a high-loaded nickel catalyst (90 wt.% Ni–Al2O3) to describe the observed process kinetics involving the catalyst deactivation. The experimental kinetic data obtained at hydrogen volume fraction of 0–40%, 490–590 °C and atmospheric pressure are analyzed to suggest the formula for calculation of the maximal rate of the carbon formation and the equation of the catalyst deactivation. The suggested kinetic model relates to the mechanism when the cleavage of the first hydrogen atom from a methane molecule adsorbed on the catalyst surface is the rate-limiting stage. The model is appropriate for the qualitative and quantitative description of the process under consideration. The calculations in terms of the model are exemplified with synthesis of nanofibrous carbon in an isothermal perfect-mixing reactor at a constant methane consumption. The calculated results agree well with the experimental data.