Preparation of "intelligent" Pt/Ni/Mg(Al)O catalysts starting from commercial Mg-Al LDHs for daily start-up and shut-down steam reforming of methane

Ni/[Mg_xAl]O (x = 3.5, 1.5 and 0.5) doped with trace amounts of Pt were prepared from Mg-Al layered double hydroxides (LDHs) aiming the "green" preparations of "intelligent" reforming catalysts. Commercial Mg-Al LDHs were used as raw materials. The LDHs were calcined and impregnated with Ni(II) and Pt(IV) nitrates at room temperature. The preparative conditions were optimized to produce an effective catalyst for the daily start-up and shut-down steam reforming of methane. The catalysts exhibited the "intelligent" properties, i.e., self-activation and self-regenerative activity. We conclude that well crystallized Mg(Al)O periclase played an important role in the "intelligent" properties of the Pt/Ni/[Mg_xAl]O catalysts; the periclase acted as an effective Ni reservoir for a reversible reduction-oxidation movement of Ni ions between the outside and the inside of the Mg(Al)O periclase crystals. Surface Ni⁰ was oxidized to Ni²⁺ by steam and incorporated into Mg(Ni²⁺,Al)O periclase, whereas the Ni²⁺ ions in the periclase were reduced to Ni⁰ by the hydrogen spillover forming small Ni⁰ particles on the catalyst surface.