The characterization of South Moravian lignite in its natural and treated forms using thermal degradation methods

Abstract

Thermal degradation experiments were performed on South Moravian lignite in its natural and treated forms primarily to investigate the changes taking place during pyrolysis, and, secondarily, to determine the structural characteristics of lignite using thermal degradation methods The lignite was treated by extraction with chloroform, demineralization, and the remineralization or sorption of calcium ions on the demineralized lignite. The analysis of pyrolysis products was performed in solid and gaseous states using FTIR analysis and the thermogravimetric technique coupled with FTIR (TG-FTIR). Experiments were complemented by thermochemolysis with tetramethylammonium hydroxide (TMAH). South Moravian lignite was characterized by the bimodal distribution of saturated fatty acids, with two maxima at n-C16 and at n-C28, and the dominance of guaiacyl units indicating a gymnosperm origin. FTIR analysis of the examined sample set showed that lignite contains different functional groups with various thermal stabilities degrading to the evolution of gases such as H2O, CO, CO2 and CH4. Precursors of the gaseous products generated and an analysis of functional groups in the samples are discussed in the paper. The results show that treatments of lignite may be reflected in their thermal behaviors during pyrolysis.