A fluid catalytic cracking (FCC) ZSM-5 based additive was used as a co-catalyst to Y-zeolite based FCC catalysts in the catalytic pyrolysis of hybrid poplar. Different proportions of ZSM5-based FCC additive and FCC catalysts were explored at 475 degrees C and a weight hourly space velocity of 2 h (1) in a 1-stage and a novel 2-stage bench scale bubbling fluidized bed reactor. The ZSM-5 additive in the FCC/ZSM-5 blends resulted in increased organic liquid fraction and decreased coke/char and gas yields. Formation of CO2, CH4, and H-2 gases decreased and the generation of C-5 hydrocarbons increased with increase in the levels of ZSM-5 additive. In comparison to the base FCC catalyst, the FCC/ ZSM-5 hybrid catalysts produced bio-oils with relatively lower viscosities. The addition of ZSM-5 to the FCC catalyst enhanced the formation of aromatic compounds and decreased aliphatic hydrocarbons. Reactor configuration was found to influence the process in terms of product distribution and the physico-chemical properties of the bio-oils. (C) 2013 Elsevier Ltd. All rights reserved.