Home – Home – Jornals – Chemistry for Sustainable Development 2018 number 4

The composition and thermal behaviour of the ethanol lignins isolated by means of extraction with organic solvents from the wood biomass of the coniferous and deciduous trees were studied by means of nonisothermal thermogravimetric (TG/DTG, DSC) analysis, FTIR spectroscopy, elemental analysis, scanning electron microscopy (SEM). Comparative analysis of the IR spectra of initial lignin and lignin treated thermally at 200 °C provides evidence that they have identical structural and groups composition. The initial temperature of abies lignin decomposition (252 °C) is higher by approximately 10 °C than that for aspen wood. It was established that prevailing decomposition of abies lignin in argon proceeds within the temperature range 337-427 °C: the highest rate of destruction is -2.9 %/min, the maximal decomposition is observed at 400 °C. Aspen lignin undergoes intense decomposition within a lower temperature range (327-400 °С) with the maximal rate of mass loss-3.1 %/min at 378 °C. The data of IR spectra of the products of abies lignin decomposition at 400 °С provide evidence of the substantial degree of lignin polymer decomposition with the possible formation of the derivatives of quaiacol and substitute4d phenol compounds. The completion of lignin thermal destruction at 800 °C is accompanied by the formation of carbon residues with the yield of 34 % from aspen lignin and 37 % from abies lignin. The appearance of carbonized particles in the structure of the material (starting from 240 oC) and further intensification of the formation of carbon matrix with an increase in pyrolysis temperature to 600 oC were confirmed by means of SEM. The maximal rates of aspen lignin decomposition were discovered to be higher than those of abies lignin within all conventional temperature ranges.