Upgrading of Bio-oil over Bifunctional Catalysts in Supercritical Monoalcohols

In this paper, bio-oil from fast pyrolysis of Pinus sylvestris L. was upgraded over supported noble metal catalysts in supercritical monoalcohols under a hydrogen atmosphere. Esterification, cracking (both alcoholysis and hydrolysis), hydrogenation, along with acetalization, isomerization, and other reactions were combined during the upgrading process. The product analysis showed that processing in ethanol over Pt/SO42-/ZrO2/SBA-15 had a good upgrading performance. The removal of acids and aldehydes and the decrease of ketones, phenols, sugars, and polycyclic aromatic hydrocarbons were achieved. Meanwhile, esters became dominant in upgraded oil. The effects of solvents, noble metal catalysts, and catalyst supports had been briefly discussed. Pretreatment tests suggested that the presented upgrading process can be applied to the whole bio-oil without fractionation. As a result, an effective solvent recovery and a post-water-removal process will be required for the application of upgraded oil.