Study of the Thermochemical Properties of Ethanol Lignins from Abies and Aspen Wood
The functional composition and thermochemical properties of the lignins isolated by ethanol extraction of fir and aspen wood were studied by the non-isothermal thermogravimetric analysis, FTIR spectroscopy, elemental analysis, and scanning electron microscopy. The peculiarities of thermal destruction of these two Types of lignin in inert (argon) and oxidizing (air) media were revealed. The maximum rates of decomposition of ethanol lignins from fir and aspen wood in an inert medium are reached at 400 and 377.6 °C, respectively. The thermal degradation of aspen lignin in air medium is accompanied by the appearance of two maxima at 275 and 355 °C, and of fir lignin - one maximum at 402 °C. The comparison of thermochemical properties of aspen wood and isolated from wood the ethanol lignin and cellulose was made. It was shown that the temperatures corresponding to the highest rates of thermal decomposition of aspen wood, cellulose and lignin in an inert medium are 363.4, 333.7 and 377.6 °C, respectively. In all temperature range, the thermal decomposition of aspen lignin, both in the inert and air medium proceeded at the higher rates of mass loss than that of fir lignin.