COPPER-ZINC OXIDE CATALYST .2. PREPARATION, IR CHARACTERIZATION AND THERMAL-PROPERTIES OF NOVEL BIMETALLIC PRECURSORS

Four new bimetallic model precursors of copper-zinc oxide catalysts fo r methanolization were prepared: Zn(NH3)(2)Cu(CN)(3) (ZCA), [Zn(en)(3) ](6)[Cu-5(CN)(17)]. nH(2)O (n = 8.4) (ZCE3), Zn(en)Cu(CN)(3) (ZCE1) an d [Zn1-xCux(en)] [Cu(CN)(3)] (ZCCE1). The new compounds were character ized by elemental analysis, IR spectroscopy, and thermal analysis unde r dynamic conditions. Thermal stability increases in the order ZCE3 (6 5) < ZCA (120) < ZCE1 or ZCCE1 (155 degrees C). Thermal decomposition in air proceeds via the following steps: dehydration (if water molecul es are present), deamination, redox decomposition of the cyano groups with formation of metallic copper and ZnO, and finally re-oxidation of copper to CuO. In the case of en-containing compounds an unexplained phase transition was observed at 800 degrees C.