Copper zinc oxide catalysts .5. Preparation, structure and thermal properties of a zinc copper maleate precursor Cu0.06Zn0.94C4H2.2H(2)O

A new Cu-Zn bimetallic precursor Cu0.06Zn0.94C4O4H2 . 2H(2)O useful as a model catalyst for methanolation of syngas was prepared and identified. It crystallises in the monoclinic space group Cc with cell parameters a = 5.725(1), b = 16.251(2), c = 6.825(1) Angstrom, beta = 90.72(1)degrees, Z = 4. The structure analysis shows a two-dimensional polymeric structure with layers containing metal atoms interconnected by tridentate maleate anions. The smallest ring in the layer contains 18 atoms among which are three metal atoms. These metal atoms are connected by two maleate ligands through the opposite carboxylic groups and the ring is completed by one syn-anti carboxylate bridge Zn-O-C-O-Zn. The metal atom is five-co-ordinated in the MO2O3 form through three oxygen atoms from three different maleate anions and two terminal water ligands. The packing of the structure is stabilised by intra-and inter-layer hydrogen bonds. Thermal decomposition begins with dehydration (75-170 degrees C) followed by decomposition of the maleate anions (190-635 degrees C). As final phases, zincite ZnO (major) and tenorite CuO (minor) were identified.