Titania-supported cobalt and nickel bimetallic catalysts for carbon dioxide reforming of methane

Titania-supported cobalt and nickel bimetallic catalysts were investigated for CO₂ reforming of methane to synthesis gas at 1023 K under ambient pressure. Bimetallic Co-Ni/TiO₂ catalysts with an appropriate Co/Ni ratio showed highly stable activities without carbon deposition. Whereas the monometallic Co/TiO₂ catalyst deactivated rapidly because of the oxidation of metal, 10 mol% substitution of nickel for cobalt suppressed the oxidation of metal, providing a high catalytic stability. However, the catalysts with excess nickel content (>80 mol%) underwent carbon formation. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses revealed that a homogeneous alloy of cobalt and nickel was formed from bulk to the surface by the H₂ reduction, and the alloy was stable during reforming. The advantages of the bimetallic catalysts are high resistance to undesirable metal oxidation and coking, through the control of reactions between CH₄ and CO₂.