Efficient selective hydrogenation of cinnamaldehyde over zeolite supported cobalt catalysts in water

Rapid and efficient selective hydrogenation of cinnamaldehyde to cinnamyl alcohol was achieved over ZSM-5 supported cobalt catalysts in water. The conversion of cinnamaldehyde in water system is nearly two times of ethanol system under the same reaction conditions. The selectivity to cinnamyl alcohol was maintained at ~78 % when the conversion of cinnamaldehyde is below 95 % over the best catalyst. The catalytic performance of the Co/ZSM-5 catalyst was highly dependent upon the Co loading. The selectivity to cinnamyl alcohol dropped to ~40 % when the Co loading was higher than 20 wt%, which indicated that such reaction could be structure sensitive. It is expected that lower Co loading should correlate with smaller “fcc structured” Co particle, which favors the formation of cinnamyl alcohol. Finally, we mention that the use of water as the solvent can avoid the formation of acetal (by-product), which is frequently observed when using ethanol as the solvent; in addition, the solvent water can be reused successfully.