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 identif ied. It crystallises in the monoclinic space group Cc with cell parame ters 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 polym eric structure with layers containing metal atoms interconnected by tr identate maleate anions. The smallest ring in the layer contains 18 at oms 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 oxyge n atoms from three different maleate anions and two terminal water lig ands. The packing of the structure is stabilised by intra-and inter-la yer hydrogen bonds. Thermal decomposition begins with dehydration (75- 170 degrees C) followed by decomposition of the maleate anions (190-63 5 degrees C). As final phases, zincite ZnO (major) and tenorite CuO (m inor) were identified.