Homogeneous Catalytic Hydrogenation of Bio-Oil and Related Model Aldehydes with RuCl2(PPh3)3

A homogeneous RuCl2(PPh3)(3) catalyst was prepared for the hydrogenation of bio-oil to improve its stability and fuel quality. Experiments were first performed on three model aldehydes of acetaldehyde, furfural and vanillin selected to represent the linear aldehydes, oxygen heterocyclic aldehydes and aromatic aldehydes in bio-oil. The results demonstrated the high hydrogenation capability of this homogeneous catalyst under mild conditions (55-90 degrees C, 1.3-3.3 MPa). The highest conversion of the three model aldehydes was over 90 %. Furfural and acetaldehyde were singly converted to furfuryl alcohol and ethanol after hydrogenation, while vanillin was mainly converted to vanillin alcohol, together with a small amount of 2-methoxy-4-methylphenol and 2-methoxyphenol. Further experiments were conducted on a bio-oil fraction extracted by ethyl acetate and on the whole bio-oil at 70 degrees C and 3.3MPa. Most of the aldehydes were transformed to the corresponding alcohols, and some ketones and compounds with C-C double bond were converted to more stable compounds.