Structure sensitive dissociation of CH4 on Ni/α-Al2O3: Ni nano-scale particles linearly compensate the Ea and ln A for the CH4 pulse kinetics

The intrinsic kinetic information for the dissociation of CH4 on the fresh Ni active sites was studied by pulsing CH4 through Ni/α-Al2O3 catalyst with different Ni particles. After the elimination of the mass and heat transfer, the conversions of CH4 were controlled far below the values of the thermodynamic equilibrium in order to keep the pulse reaction in the kinetic region. The coverage degree of carbon species on Ni active site is kept less than 1 to eliminate the influence of carbon deposition on the dissociation of CH4. The plot of TOFCH4TOFCH4 versus the Ni particle size exhibits a “mountain” shape. The Ea and ln A for the CH4 dissociation are linearly increased with the increase in the Ni particle size, showing the compensation effect in the CH4 dissociation. This work reveals that the CH4 dissociation on fresh Ni active site of Ni particles in Ni/α-Al2O3 catalysts is a structure sensitive reaction.

This work found that the CH4 dissociation on Ni particles is a structure sensitive reaction due to the “mountain” shape of the plot of TOF of CH4 dissociation versus the Ni particle size in the CH4 pulse through the Ni/α-Al2O3. It was also found that Ea and ln A are linear dependence on the Ni particle size of Ni/α-Al2O3 and the presence of the compensation effect in the CH4 dissociation reaction. Figure optionsDownload as PowerPoint slide