Ex-situ catalytic fast pyrolysis of biomass over HZSM-5 in a two-stage fluidized-bed/fixed-bed combination reactor

Ex-situ and in-situ catalytic fast pyrolysis (CFP) of biomass over HZSM-5 were compared in a two-stage fluidized-bed/fixed-bed combination reactor. Ex-situ CFP gave a similar carbon yield of aromatics + olefins (similar to 20%) with in-situ CFP but produced much more olefins (10.3% vs. 5.8%) and less char + coke (42.7% vs. 48.4%). The effects of weight hourly space velocity (WHSV), carrier gas flow rate, pyrolysis temperature and catalysis temperature on product distribution in ex-situ CFP were further studied. The maximum carbon yield of aromatics + olefins (21.7%) was obtained at pyrolysis temperature of 550 degrees C and catalysis temperature of 600 degrees C with the highest carrier gas flow rate (1.2 L/min) and WHSV of 1.33 h(-1). Obviously less coke was generated at higher pyrolysis temperature. When catalysis temperature increased to 700 degrees C, ethylene and benzene carbon selectivities boosted to 79.4% and 60.5%, respectively. (C) 2017 Elsevier Ltd. All rights reserved.