Selective synthesis of isobutanol by means of the Guerbet reaction - Part 1. Methanol/n-propanol condensation by using copper based catalytic systems

The synthesis of isobutanol ((BuOH)-Bu-i) from mixtures of methanol (MeOH) and n-propanol (PrOH), via the Guerbet reaction, has been studied. Heterogeneous copper based catalytic systems, in combination with soluble sodium methoxide (MeONa) as basic component, were employed. In particular, copper-Raney and copper chromite were tested as metal components. The effect of the relative amount of MeONa with respect to the copper component as well as of PrOH was investigated. The influence of reaction parameters such as temperature, reaction environment (type of gas and its pressure) and composition of the MeOH/PrOH mixture used as feed was also evaluated. In all cases, independently from the type of copper derivative used, the selectivity to (BuOH)-Bu-i was nearly complete. Moreover, an increase of the temperature in the 180-220degreesC range caused a remarkable improvement of PrOH conversion and productivity to (BuOH)-Bu-i. The replacement of H-2 atmosphere by N-2 caused a significant improvement of catalyst productivity. When the experiments were performed under CO/H-2 atmosphere the catalyst activity was similar to that obtained under H-2. The catalysts based on copper chromite showed, under the same reaction conditions, higher activities (about one order of magnitude) as compared with those obtained by using copper-Raney based catalysts. (C) 2002 Elsevier Science B.V. All rights reserved.