Selective synthesis of 2-ethyl-1-hexanol from n-butanol through the Guerbet reaction by using bifunctional catalysts based on copper or palladium precursors and sodium butoxide

The Guerbet self-condensation of n-butanol (BuOH) to 2-ethyl-1-hexanol (2EH) in the presence of different catalytic systems based on a metal hydrogenating/dehydrogenating component and a base was studied. In particular, homogeneous and heterogeneous palladium derivatives were used at 200degreesC in combination with sodium butoxide (BuONa) as basic component. The effect of reaction parameters, such as BuONa concentration and amount of the metal component were investigated. Turnover numbers (TN) up to 80 mol of 2EH/(mol of Pd x h) were reached. In the case of heterogeneous palladium precursors an extensive leaching into solution was observed. The catalytic system based on completely heterogeneous copper chromite in combination with BuONa was also studied. In this case the effect of reaction parameters, such as the base concentration, the addition of either an ancillary base (MgO) or a dehydrating agent (CaO, molecular sieves) as well as reaction temperature was investigated. TN values up to 22 were obtained working at 280degreesC. In all the experiments a complete selectivity to 2EH was ascertained, independently on the type of the adopted catalytic system and reaction conditions. (C) 2003 Elsevier B.V. All fights reserved.