Effect of small amount of Pt, Pd and Ru promoters on the characteristics and performance of Co/SiO2 catalyst, which was prepared from the mixture of cobalt nitrate and cobalt acetate, was investigated in the hydroformylation of 1-hexene. It was found that the addition of small amount of a noble metal to the supported cobalt catalyst led into great improvement of catalyst activity for hydroformylation of 1-hexene. The 1-hexene conversion as high as 89.7% and oxygenate products selectivity of 88.9% were obtained after reaction of 2 h over Pd promoted CO/SiO2 catalyst. The increasing of reduction degree, the minimizing of cobalt particle size and the enhancement of carbonyl and linear CO adsorption were responsible for the improved performance of the catalyst. (C) 2002 Elsevier Science Ltd. All rights reserved.