Magneto-chemical characteristics of copper-cobalt catalysts

Transition metals copper and cobalt play vital roles in the conversion of syngas (CO+H₂) to liquid fuels. Catalytic studies reveal that product selectivity is governed by intermetallic ratios and method of preparation. Perturbations in metallic charge distribution and morphological changes in metal crystallites could influence both catalytic and magnetic behavior of the catalyst. To examine the correlations between catalytic and magnetic properties, we investigated the zero-field NMR and magnetization character of a series of supported and unsupported Cu-Co catalysts in the range 0.2<Cu/Co<8.0. Significant shifts of NMR lines of cobalt occur in samples for Cu/Co>1, indicating strong interactions between Cu and Co. Chromia serves as a neutral support inhibiting inter-metallic interactions, while titania supported catalysts exhibit strong metal-support interaction (SMSI). Cu-Co-Cr₂O₃ catalysts show three distinct regions of magnetization character similar to the three regions of selectivity. Magnetic moment of the composite is very low for Cu/Co<1.5 (hydrocarbons), appreciably increases for 1.5<Cu/Co<5.0 (mixed alcohols), and drops again when Cu/Co>5.0 (methanols)