Switching Selectivity in the Hydrogen Transfer Reduction of Furfural

Supported Cu catalysts and bare inorganic oxides have been tested in the reduction of furfural to furfuryl alcohol under hydrogen transfer reaction conditions by using butanol as a donor. Bare oxides like zirconia and alumina were found to be more active than the corresponding supported catalysts and in particular high surface Zirconia gave a quantitative transformation of the aldehyde into alcohol in 2,5 h at 140 degrees C according to a pure Meerwein-Ponndorf-Verley mechanism. Competitive dehydrogenation of the alcohol formed on the surface of Cu catalysts strongly reduces their activity although selectivity to alcohols on zirconia and alumina supported catalysts keeps very high. On the other hand catalysts with a well-defined Lewis acid character such as highly dispersed Zirconia on Silica allowed to obtain up to 64% yield in 2-butyl-furfuryl-ether under the same conditions.