EXAFS Studies on Supported Nickel System Bimetallic Catalysts

EXAFS is used to investigating the structures of nickel system bimetallic catalysts in prepared proccess, oxidized and reduced catalysts. The results show that the coordination environment of nickel atom in Ni / SiO₂（OX） and Ni/ SiO₂（RE） catalysts are similar to that in NiO powder and Ni foil respectively. In the Ni-Cr/ SiO₂（OX） and Ni-Fe / SiO₂（OX） catalysts, the coordination number in second shell of nicket atom is drastically decreased, from 12 to 5 compering with NiO powder, it is interpreted as that Ni oxide form NiCrO₄ or NiFe₂O₄ with Cr or Fe oxide and NiO particles are high dispersivcd. The first shell coordination number of Ni atom in reduced bimetallic catalysts of alloy type is 3～5 biger than that in Ni-metal oxide type catalysts. Cr₂O₃ oxide and A1₂O₃ support can retard Ni particles to become larger during reduction. The Ni coordination number of reduced catalysts on Al₂O₃ support is 2～3 smaller than that on SiO₂ support. The EXAFS results of Ni-Zn/SiO₂ and Ni-Zn/Al₂O₃ catalysts are nearly the same as that of Ni / SiO₂ and Ni / Al₂O₃.