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FRAGILE EARTH: Geological Processes from Global to Local Scales and Associated Hazards (4-7 September 2011)

Paper No. 16
Presentation Time: 08:30-18:00

A PYROLYTIC STUDY OF GAS GENERATION FROM LIGNITES: GEOCHEMICAL CHARACTERISATION OF ORGANIC MATTER


HEIM, Sabine1, KROOSS, Bernhard M.1 and LITTKE, Ralf2, (1)Lehrstuhl für Geologie, Geochemie und Lagerstätten des Erdöls und der Kohle, RWTH Aachen University, Lochnerstrasse 4-20, Aachen, 52056, Germany, (2)Lehrstuhl für Geologie, Geochemie und Lagerstätten des Erdöls und der Kohle, RWTH Aachen University, Lochnerstrasse 4-20, Aachen, 52056, heim@lek.rwth-aachen.de

Lignite samples from different regions, depositional environments and facies types were selected to investigate the petrography and geochemistry of low rank sedimentary organic matter. In continuation of previous research, this study attempted to assess the fate of nitrogen within the sedimentary nitrogen cycle, and evaluate qualitative and quantitative aspects of the thermal N2 generation from different nitrogen-containing precursor entities.

In a first screening phase, open system non-isothermal pyrolysis experiments were performed for a systematic comparison of gas liberation processes. Generation rates of N2 and CH4, shapes and intensities of pyrolytic peaks were found to represent sensitive indicators of the chemical composition of sedimentary organic matter.

Pyrograms of peat as well as higher rank coals reflect the increase in thermal maturity and the associated changes in chemical composition of the organic matter from predominantly low to higher thermal stability. The positions and shapes of pyrolytic N2 generation peaks are related to the chemical conversion processes. Thermally less stable nitrogen precursors as well as some thermally stable precursor structures are present in peat. With increasing maturation, only the thermally more stable structures survive.

Quite unexpectedly the pyrograms of lignites do not match the N2 liberation trends observed for peat to higher rank hard coal but show distinct discontinuities. Obviously, the structure of nitrogen precursors in lignites is severely altered as compared to the peats. Furthermore there are also significant differences between the different lignite deposits. Thus, the liberation pattern and the chemical composition appear to be strongly influenced by the depositional environment and/or low-temperature thermal conversion processes in sedimentary basins.

Future investigations on the chemical composition of the nitrogen-containing organic matter will comprise step-wise off line pyrolysis with subsequent GC/MS analysis of the volatile products in order to elucidate the changes in chemical composition of organic nitrogen-containing compounds.

Session No. 31--Booth# 22

T4. Energy Resources in Sedimentary Basins (Posters)
Tuesday, 6 September 2011: 08:30-18:00
Poster Hall P4 (D183, Thomas Mann Halle, 1st floor) (Ludwig-Maximilians-Universität München)
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