Effect of catalyst and solvent on the furan ring rearrangement to cyclopentanone

The effect of solvent and Ni, Pt, Pd. Pt-Ru and Ru catalysts on the products distribution has been investigated in the reaction of furfural, furfuryl alcohol and 2-methyl furan under hydrogen pressure of 30-80 bar and at the reaction temperatures of 160-175 degrees C. In water as solvent the main reaction pathway is the rearrangement of furfural and furfuryl alcohol to cyclopentanone. In alcohols, the reaction leading to the furan ring rearrangement does not proceed. The distribution of reaction products is influenced by the furfural concentration and acid-base properties of solvent and supported metal catalyst. The important factor influencing the selectivity of the furan ring rearrangement to cyclopentanone is proposed to be stabilization of carbocation by strong binding on the metal surface and by additional interaction with co-adsorbed water and furfural or furfuryl alcohol. In excess of hydrogen this species is created by the scission of the C-O bond in the alkoxide or hydroxyalkyl intermediates. A plausible reaction mechanism for the furan ring rearrangement was proposed. (C) 2012 Elsevier B.V. All rights reserved.