PREPARATION OF ALUMINA-SUPPORTED CUCO CATALYSTS FROM CYANIDE COMPLEXES AND THEIR PERFORMANCE IN CO HYDROGENATION

Alumina-supported CuCo catalysts were prepared in several impregnation conditions by free adsorption from solutions of various cyanide compl exes. The species in the impregnating solutions and the kinetics and e xtent of the adsorption of metal complexes were determined by UV-visib le spectrometry. A simple electrostatic model is used to explain the i ncorporation of metal complexes as a function of their nature and the impregnation conditions. After impregnation, samples were dried and re duced under hydrogen flow at 673 K with no intermediate calcination st ep. Infrared spectra of CO chemisorbed on reduced samples showed that CO is coordinated mainly to Cu interacting with Co atoms. The reductio n to metallic copper and partial reduction of Co3+/Co2+ ions occur in parallel on H-2-reduced samples, as evidenced by X-ray photoelectron s pectroscopy and X-ray induced Cu-LMN Auger emission. Quantitative Cu(C o)/Al atomic ratios in reduced catalysts also revealed that copper and cobalt exposure strongly depends on the precursor used in the prepara tion. The catalysts were tested in CO hydrogenation at 553-593 K under CO:H-2 1:1 at 0.8 MPa and the product distribution described by an An derson-Shultz-Flory kinetics. Ex-cyanide catalysts showed a slightly h igher alcohol production than tie conventionally prepared bimetallics. Moreover, for the ex-cyanide catalysts, the promoter effect of potass ium produced an increase in both, higher alcohol synthesis and the ole fin/paraffin ratio. (C) 1998 Elsevier Science.