Mild upgrading of biomass pyrolysis vapors via ex-situ catalytic pyrolysis over an iron-montmorillonite catalyst

•Biomass pyrolysis vapors were upgraded by iron-doped montmorillonite catalysts.•Catalytic upgrading process parameters optimized by Box-Behnken statistical design.•Model equations are developed to predict yields of liquid, gas, and catalyst coke.•Catalytic pyrolysis increases stability of biomass pyrolysis liquids.•Upgraded liquids can be hydrotreated and co-processed with petroleum-derived liquids.