GC/MS Characterization of Liquids Generated from Low-Temperature Pyrolysis of Wood

Conventional pyrolysis of beech wood has been carried out for heating temperatures in the range600-900 K, reproducing conditions of interest in countercurrent fixed-bed gasification. The yieldsof liquids (water and tars) increase with the heating temperature from about 40 to 55% of drywood mass, confirming results previously obtained with a laboratory-scale gasifier. Apart fromqualitative identification of 90 species, GC/MS techniques have been applied to quantify 40-43% of tars (40 species, with major contributions from acetic acid, hydroxypropanone, hydroxyacetaldehyde,levoglucosan, formic acid, syringol, and 2-furaldehyde). Decomposition of holocelluloseleads to the formation of furan derivatives and carbohydrates, with a temperaturedominatedselectivity toward hydroxyacetaldehyde against levoglucosan. Syringols and guaiacols,originating from primary degradation of lignin, present a maximum for heating temperaturesof about 750-800 K whereas, owing to secondary degradation, phenols continuously increase.A comparison is also provided with fast pyrolysis liquids obtained from four commercial plants.