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/La0.7Sr0.3AlO3−δ catalyst revealed that 5 wt% Ni/La0.7Sr0.3AlO3−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/La0.7Sr0.3AlO3−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 H218O on Ni/La0.7Sr0.3AlO3−δ, Ni/Sr/LaAlO3, and Ni/LaAlO3 at reaction temperature of 873 K, the formation of 18O-products was observed only on Ni/La0.7Sr0.3AlO3−δ catalyst derived from redox between the lattice oxygen in the perovskite and water. Lattice oxygen in the La0.7Sr0.3AlO3−δ support worked as active oxygen species to enhance its catalytic nature.

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► Steam reforming of toluene as a model of aromatic hydrocarbon for hydrogen production.
► Ni/La0.7Sr0.3AlO3−δ catalyst showed very high activity and stability, low coke-formation.
► Substituting Sr had a strong promotion effect, but impregnating Sr showed no promotion effect.
► Transient response tests using isotope revealed the lattice oxygen played an important role.