AbstractThe upgrading of bio‐oil, obtained by fast pyrolysis of maple wood, was studied over HZSM‐5 in a fixed bed micro‐reactor operated at atmospheric pressure and in the temperature range 330‐425°C. The objective of upgrading was to maximize the amount of organic distillate product with a high yield of aromatic hydrocarbons. A maximum organic distillate of 38 wt.% of bio‐oil, which represented 28.6 wt.% of wood, was obtained at 370°C. The yield of aromatic hydrocarbons was 19.9 wt.% of wood. Above 400°C, nearly 50 wt.% of the bio‐oil was converted to coke and char. The conversion of non‐volatile components of the bio‐oil (pitch) to volatiles was at a maximum of 68 wt. % at 370°C. However, when the bio‐oil was co‐processed with tetralin, the maximum conversion of non‐volatiles increased to 86 wt.% at 410°C and the amounts of coke and char decreased. The yield of aromatic hydrocarbons also decreased to a maximum of 10.3 wt. % of wood. The role of tetralin was mainly as a diluent and not a