Coal characterization by on-line pyrolysis-field ionization mass spectrometry

Summary Pyrolysis-field ionization mass spectrometry (Py-FIMS) was used for the first time to directly characterize Chinese coals and their extracts. The summed mass spectra (about 30 magnetic scans) of four coal samples and the dimethylformamide extracts of two very different coals were registered between 50° and 750°C using linear heating in high vacuum (10^–3 Pa) and approximately 6 min temperature rise time. Utilizing temperature-programmed pyrolysis and FI as soft ionization mode, the spectra displayed almost exclusively molecular ions of the evolved products. The thermograms, i.e. the intensities of the total ion current and selected ions were plotted versus the scan number, heating time and temperature. In general, two maxima in these thermograms were observed, which were different for the coals and reflected their carbon/hydrogen content. Comparing the mass spectra of the low temperature part (first maximum) with summed spectra of the extracts shows an interesting similarity. In contrast, the high temperature part (second maximum) indicates the products of thermo-degradation. The applied method is a fast and convenient tool for the characterization of evolved volatiles and thermal degradation products of coals and coal extracts.

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Kennzeichnung von Kohlen mit direkter Pyrolyse und Feldionisations-Massenspektrometrie