Selective Hydrogenation of Unsaturated Aldehydes with the CoC12-Modified Raney, Cobalt Catalyst

Abstract

(E)- and (Z) -3, 7-dimethy1-2, 6-octadien-l-ol ((E)- and (Z) -[1]) and 3, 7-dimethy1-6octen-1-ol were preferentially obtained respectively by hydrogenations of citral [2], which is a mixture of (E)- and (Z) -3, 7-dimethy1-2, 6-octadienal, and of citronellal [3]in the presence of the CoCl₂-modified Raney Co catalyst at 30-65°C under atmospheric pressure. When the hydrogenation of [2] was stopped at the consumption of 0.3 mol of hydrogen, more than 92% of the product was a mixture of (E)- and (Z) -[1]. The best selection (99%)was observed when 1-propanol was used as a solvent. The rates of hydrogenations of [2]and [3] were dependent on the sort of solvent. The effect of the solvent on the efficiency of hydrogenation rate was observed in the following order; methanol>ethanol>1-propanol>2-propanol.