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.