Full-text Article (Subscribers only)
Full-text article (197 kB)
(subscribers only)

Buy article on-line and get access immediately
Buy article on-line for £11.75
(get immediate access)

Search
Search

Go Back

Eur. J. Mass Spectrom. 6, 39 - 48 (2000)

Structural features of large molecular mass material in coal-derived liquids: catalytic hydrocracking of the pyridine-insoluble fraction of a coal-tar pitch

V. Begon, C. Islas, M.J. Lazaro, I. Suelves, A.A. Herod,* D.R. Dugwell and R. Kandiyoti
Department of Chemical Engineering and Chemical Technology, Imperial College (University of London), Prince Consort Road, London SW7 2BY, UK

ABSTRACT:
The pyridine-insoluble fraction of a coal-tar pitch has been catalytically hydrocracked. The starting sample contained no material that could be observed by gas chromatography/mass spectrometry (GC/MS) or by heated-probe mass spectrometry. The aim of the study was to generate structural information on this narrow cut of large-molecular-mass material, which consisted mainly of compounds boiling above 450°C. A much broader boiling-point distribution was found for hydrocracked products; evidence from all analytical techniques used (size-exclusion chromatography, UV-fluorescence spectroscopy and heated-probe mass spectrometry) indicated a significant reduction of the molecular mass range. A wide variety of aromatic groups was identified in hydrocracked products by heated-probe mass spectrometry, ranging from phenanthrene (m/z 178) to beyond dibenzocoronene (m/z 400). Ions corresponding to alkyl (m/z 43, 57, 71 and 85) and alkenyl groups (m/z 41, 55, 69 and 83) were detected. The results reflect the ability of the hydrocracking process to cleave bonds within large pitch molecules, releasing the structural units which form the molecules. The structure of the original pyridine-insoluble material may thus be seen as a series of aromatic groups linked by short bridges or small groups, but with some longer aliphatic bridges (C12 and C17) as shown by pyrolysis-GC/MS. Clearly, some molecular species were reduced in mass but still lay above the range of detection by heated-probe mass spectrometry and could not be identified. Although the extent to which large polycyclic aromatic entities themselves have been cracked (or otherwise reduced to smaller polycyclic aromatic groups) cannot be quantitatively discerned from the present data, the hydrocracking of isolated fractions of intractable coal-derived material appears to offer a useful method for probing their structural features.

Keywords: coal liquids, large molecules, hydrocracking, characterisation, heated-probe mass spectrometry

You can now buy this paper on-line in PDF format; it costs only £11.75. Just click on the BUY on-line button. You can pay on-line through a secure server and get access immediately.


© IM Publications
Any problems? E-mail .