Categorization of tars from fast pyrolysis of pure lignocellulosic compounds at high temperature

This study presents how the yields of different tar compounds from pure lignocellulosic compounds respond to the change in temperature and residence time. Experiments were carried out with a drop tube furnace in the temperature range from 800 to 1250 °C. The tar composition was characterized by gas chromatography with a flame ionization detector and mass spectrometry using a dual detector system. Longer residence time and higher heat treatment temperatures increased the soot formation and decreased the tar yields. Soot yields from lignin samples were greater than soot yields from holocellulose pyrolysis. The dominating products in tars from pyrolysis of all lignocellulosic compounds were benzene and toluene. Cellulose and hemicellulose pyrolysis produced greater amount of oxygenates in tars, whereas lignin tar was rich in phenols, polycyclic hydrocarbons and naphthalenes. Simultaneous reduction of tar and soot was achieved by impregnation of lignin from wheat straw with alkali metals. The OPLS-DA model can accurately explain the differences in tar composition based on the experimental mass spectrometry data.The authors gratefully acknowledge financial support from the Kempe Foundations and the Swedish strategic research program Bio4Energy. We are grateful to the plant cell wall and carbohydrate analytical facility at UPSC/SLU, supported by Bio4Energy and TC4F for the GC-MS analysis. The authors acknowledge the facilities and technical support of Dr. Junko Takahashi-Schmidt at Umeå Plant Science Centre. Dr. Flemming Hofmann Larsen and Dr. Soren Talbro Barsberg at University of Copenhagen are acknowledged for the technical support with NMR and FTIR analysis. We acknowledge Raymond Mclnerney from University of Limerick for the article proof-reading.peer-reviewed2021-04-1