Upgrading of biomass pyrolysis vapors over 20 wt.% Na2CO3/gamma-Al2O3 catalyst was studied in a lab-scale fix-bed reactor at 500 degrees C. Characterization of the catalyst using SEM and XRD has shown that sodium carbonate is well-dispersed on the support gamma-Al2O3. TGA and Na-23 MAS NMR suggested the formation of new hydrated sodium phase, which is likely responsible for the high activity of the catalyst. Catalytic oil has much lower oxygen content (12.3 wt.%) compared to non-catalytic oil (42.1 wt.%). This comes together with a tremendous increase in the energy density (37 compared to 19 MJ kg(-1)). Decarboxylation of carboxylic acids was favoured on the catalyst, resulting to an oil almost neutral (TAN = 3.8 mg KOH/g oil and pH = 6.5). However, the mentioned decarboxylation resulted in the formation of carbonyls, which correlates to low stability of the oil. Catalytic pyrolysis results in a bio-oil which resembles a fossil fuel oil in its properties. (C) 2013 Elsevier Ltd. All rights reserved.