Highly selective production of light aromatics from lignin through integrated approach of the torrefaction deoxygenation pretreatment and the dual-catalyst catalytic fast pyrolysis using Nb modified γ-Al2O3 and HZSM-5

•Torrefaction pretreatment and catalytic pyrolysis were employed to produce aromatics.•Torrefaction deoxygenation mechanism of lignin was established.•Oxygen was removed by the cleavage of ether alkyl bond and other oxygenated groups.•Incorporation of Nb metal on Al2O3 could further improve the yield of aromatics.•Synergistic effect between the Nb modified Al2O3 and the zeolite was established.