Characterization of a pyrolysis liquid from a German brown coal by use of negative and positive ion mode electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry and collision-induced dissociation

A pyrolysis oil produced by slow pyrolysis from a German brown coal was analysed using a combination of three mass spectrometric methods. Various compounds of the pyrolysis liquid sample were ionized by electrospray ionization, both in positive (ESI(+)) and negative (ESI(-)) ion mode, and analysed by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). ESI(-)-FT-ICR-MS analyses mainly exhibit oxygen- as well as sulfur-/oxygen-containing compounds in the pyrolysis oil. In contrast, ESI(+)FT-ICR-MS analyses were dominated by nitrogen- and nitrogen-/oxygen-containing species. Structural suggestions were possible by plotting the carbon number (n(c)) vs. the double bond equivalent (DBE). The assigned structures were further examined by applying ESI(-)-FT-ICR-MS with collision-induced dissociation mass spectrometry (CID-MS). The degradation of the pyrolysis oil constituents into their structural building blocks was monitored by varying the collision energy and its influence on the peak number and the median m/z. According to our results, dealkylation and decomposition processes of multiaromatic systems dominated during the CID event. Possible structural building blocks of pyrolysis oil 5500 were found to be polycyclic aromatic ketones and quinones, partially bound to thiophenic structures. It was shown that the developed combination of ESI(+)- and ESI(-)-FT-ICR-MS with ESI(-)-CID-FT-ICR-MS gives the possibility to examine a complex sample, such as a pyrolysis liquid, by investigating its basic chemical backbone. (C) 2017 Elsevier Ltd. All rights reserved.