Guerbet condensation of methanol with n-propanol to isobutyl alcohol over heterogeneous copper chromite/Mg-Al mixed oxides catalysts

The synthesis of isobutyl alcohol ((BuOH)-Bu-i) from methanol (MeOH) and n-propanol (PrOH) through the Guerbet condensation has been studied at 200 degreesC and under inert atmosphere (3.0 MPa of N-2) using a two-component heterogeneous catalytic system based on pre-activated copper chromite and Mg-Al mixed oxides deriving from hydrotalcite-type (HT) precursors with different Mg/Al ratios. All the investigated catalysts displayed a significant activity, with an almost complete selectivity to TuOH. Unlike the copper chromite/soluble sodium methoxide system, the catalysts were tolerant of the co-produced water and did not display any appreciable deactivation during the course of the reaction. The catalyst productivity was found to increase by reducing the Mg/Al ratio in the heterogeneous base, according to the increase of the fraction of medium-strong and strong basic sites which favour the aldol condensation between the aldehydes derived from MeOH and PrOH. (C) 2004 Elsevier B.V. All rights reserved.