Development of Raney cobalt catalysts for the hydrogenation of squalene type compounds

Raney (TM) cobalt catalysts were synthesized from an aluminum-cobalt alloy by leaching with sodium hydroxide solution at similar to 41 and 100 A degrees C with and without the addition of ammonium molybdate. For the products synthesized at 100 A degrees C, the surface areas of the catalysts were lower and the pore sizes were correspondingly larger. The surface areas were higher and average pore openings smaller when molybdate was included in the preparation. The X-ray diffraction measurements indicated that the Mo promoted catalysts have smaller average crystallite size than the unpromoted ones. The SEM micrographs confirmed that the surface morphology at low temperature synthesis is finer than at higher temperature. The NEXAFS spectra showed the ratio of elemental cobalt to cobalt oxide on the surface increases during the addition of molybdenum precursor, suggesting the Mo addition stabilizes the metallic cobalt from coarsening. The NEXAFS spectra also suggested that the cobalt oxide causes the blocking of small pores. Molybdenum(IV) species act by adsorption on the surface of the catalysts inhibiting the dissolution of the cobalt and subsequent re-precipitation as an oxide. Catalytic testing was conducted using squalene as a model compound for bio-oil from the algae Botryococcus braunii. A better hydrogenation yield is achieved when Raney (TM) cobalt catalyst is modified with molybdenum.