Preparation and catalysis of amorphous CoNiB and polymer-stabilized CoNiB catalysts for hydrogenation of unsaturated aldehydes

Abstract

The CoNiB and PVP-stabilized CoNiB catalysts were prepared by chemical reduction with NaBH 4 . They were significantly more active than NiB and CoB in the hydrogenation of furfural , crotonaldehyde and citral. The most active catalyst PVP(2)-CoNiB(0.5) could selectively hydrogenate citral to citronellal at a low reaction temperature of 30 °C, with a good citronellal selectivity of about 86%. CoNiB and polymer polyvinylpyrrolidone (PVP)-stabilized CoNiB (PVP-CoNiB) catalysts were prepared by chemical reduction with NaBH 4 . They were characterized and examined for their catalysis in the hydrogenation of unsaturated aldehydes. CoNiB and PVP-CoNiB catalysts were characterized by X-ray diffraction as amorphous structures and by transmission electron microscopy as having particle sizes in the range 3.5–7 nm – smaller than those of NiB (7–15 nm) and CoB (5–10 nm). CoNiB catalysts were significantly more active than NiB and CoB in the hydrogenations of furfural, crotonaldehyde and citral, and the PVP-CoNiB catalysts were significantly more active than CoNiB. The catalytic properties of CoNiB and PVP-CoNiB catalysts during the selective hydrogenations of crotonaldehyde and citral were similar to those of NiB, but different from those of CoB. The conjugated C C bonds in crotonaldehyde and citral were preferentially reduced to form butyraldehyde and citronellal. PVP-CoNiB could hydrogenate citral to citronellal at a low reaction temperature of 30 °C.