THERMAL TREATMENT ON LIGNIN, CELLULOSE AND HEMICELLULOSE IN NITROGEN AND CARBON DIOXIDE

The paper explores the primary products from fast pyrolysis of biomass components: Lignin, Cellulose and Hemicellulose (Xylan). A heated strip reactor was employed at temperatures of 1573 K and 2073 K in N2 and CO2 atmospheres. Volatiles were quenched immediately after volatilization and tar and char were collected for further analysis. Experiments carried out on Hemicellulose at 2073 K did not generate appreciable amounts of tar samples by solidified droplets. Soot and char were recovered only after Lignin pyrolysis at 2073 K in N2. Tars, after acetone extraction, were analysed by gas chromatography-mass spectrometry for quantitative determination of aromatic and aliphatic compounds. The higher molecular weight (MW) fraction, insoluble in acetone, was further dissolved in N-methyl pyrrolidone and analysed by Size Exclusion Chromatography for the evaluation of MW distribution. A large presence of monosaccharide is noticed in the Cellulose and Hemicellulose tars. In the tars produced from Lignin oxo-aromatics compounds are the most abundant species. Higher temperature and the presence of the CO2 favor cracking of heavy tar and formation of oxygenated species. However at 2073 K in N2 also very high MW species (at 3.7*108 u, which corresponds to dimensions of about 100 nm) are recovered in Lignin and Cellulose products. Chars were characterized by Thermogravimetric analysis, Raman spectroscopy and Scanning Electron Microscopy. A distinctively lower reactivity and more ordered structure were observed for the Lignin char prepared at 2073 K in N2, whereas CO2 proved to hinder thermal annealing and also decomposition of mineral matter inside the solid samples.