Steam reforming of toluene over perovskite-supported Ni catalysts

Hydrogen production by steam reforming of toluene as a model aromatic hydrocarbon has been investigated with various Ni/perovskite catalysts. Among them, Ni/LaAlO₃ catalyst showed high catalytic activity. Partial substitution of the La site of LaAlO₃ support with other elements (Sr, Ba or Ca) was conducted for the Ni/LaAlO₃ catalyst, and substitution with 30% Sr promoted catalytic activity and selectivity to hydrogen. Optimization for the Ni loading amount over Ni/La_0.7Sr _0.3AlO_3-δ catalyst revealed that 5 wt% Ni/La _0.7Sr_0.3AlO_3-δ had the highest toluene conversion and the smallest amount of carbon deposition. To elucidate the role of doped Sr, the catalytic natures of Sr-substituted catalyst Ni/La _0.7Sr_0.3AlO_3-δ and Sr-supported catalyst Ni/Sr/LaAlO₃ were compared. Results show that Sr-ions should be incorporated in the LaAlO₃ perovskite structure to show high catalytic performance. Based on results of transient response test with H ₂¹⁸O on Ni/La_0.7Sr_0.3AlO _3-δ, Ni/Sr/LaAlO₃, and Ni/LaAlO₃ at reaction temperature of 873 K, the formation of ¹⁸O-products was observed only on Ni/La_0.7Sr_0.3AlO_3-δ catalyst derived from redox between the lattice oxygen in the perovskite and water. Lattice oxygen in the La_0.7Sr_0.3AlO _3-δ support worked as active oxygen species to enhance its catalytic nature.