Preparation of alumina-supported CuCo catalysts from cyanide complexes and their performance in CO hydrogenation Original Research Article

Alumina-supported CuCo catalysts were prepared in several impregnation conditions by free adsorption from solutions of various cyanide complexes. The species in the impregnating solutions and the kinetics and extent of the adsorption of metal complexes were determined by UV-visible spectrometry. A simple electrostatic model is used to explain the incorporation of metal complexes as a function of their nature and the impregnation conditions. After impregnation, samples were dried and reduced under hydrogen flow at 673 K with no intermediate calcination step. Infrared spectra of CO chemisorbed on reduced samples showed that CO is coordinated mainly to Cu interacting with Co atoms. The reduction to metallic copper and partial reduction of Co3+/Co2+ ions occur in parallel on H2-reduced samples, as evidenced by X-ray photoelectron spectroscopy and X-ray induced CuLMN Auger emission. Quantitative Cu(Co)/Al atomic ratios in reduced catalysts also revealed that copper and cobalt exposure strongly depends on the precursor used in the preparation. The catalysts were tested in CO hydrogenation at 553–593 K under CO : H2 1 : 1 at 0.8 MPa and the product distribution described by an Anderson–Shultz–Flory kinetics. Ex-cyanide catalysts showed a slightly higher alcohol production than the conventionally prepared bimetallics. Moreover, for the ex-cyanide catalysts, the promoter effect of potassium produced an increase in both, higher alcohol synthesis and the olefin/paraffin ratio.