Figure 9. Pyrolysis mass spectrum of a fungal lipid fraction showing the characteristic ion series of choline-containing phospholipids namely at m/z 58 (C3H8N), 59 (trimethylamine), 71 (N,N-dimethylvinylamine) and 89 (N,N-dimethylaminoethanol; sometimes more pronounced, depending on the sample matrix). Note also typical methylchloride ion signals at m/z 50 and 52. The peaks at m/z 107 and 109 should probably be assigned to N,N-dimethylvinylammoniumchloride. As discussed in the text, the lipid part of the molecule is strongly under-represented in the spectrum. Conditions: sample 10 yg; T 510°C; E ^ 14 eV.

Figure 10. Pyrolysis mass spectrum of a Bj^rkmann lignin, obtained from straw, showing the presence of all three characteristic lignin building blocks in grass lignins. Conditions: sample 10 ug; T 610°C; E 15 eV.

distinguishable, as reported by Meuzelaar et al. (ref. 50). The chemical identities of the main pyrolysis products of lignin have been established by several authors, e.g. using Py-GC-MS techniques (refs. 52, 97).

Soil polymers, e.g. humic acids, as well as geopolymers, e.g. coals and kerogens although not strictly polymers in the sense of having well defined repeating subunits, are another class of macromolecular substances amenable to Py-MS analysis (ref. 52). The more random, highly complex configurations of these substances however, have so far eluded precise structural elucidation. With regard to coal structure, a recent report by the Committee of Chemical Sciences of the National Research Council, The Department of Energy, USA (ref. 98), notes that:

"It -probably will not be possible in the foreseeable future actually to determine the "structure" of coal absolutely in the way we can with, say, organic compounds. Coal is heterogeneous by nature and it varies in structure no less from millimeter to millimeter in the same seam than between coals from different rank formed from different species of plant matter in swamps hundreds or thousands miles apart. The committee believes, however, that it is possible to determine in coals the key structural features that affect utility and reactivity".

As a result, understanding of pyrolysis mechanisms in these materials is highly speculative at most, and chemical interpretation of their pyrolysis-mass spectra is generally confined to the labelling of characteristic ion series as "alkenes", "benzenes", "naphthalenes", "phenols", "pyrroles", etc. (see Section 7.5). Nevertheless, this may provide useful insight into the degree of aromaticity or unsaturation, into the presence of heteroatomic compounds, e.g. sulphur compounds, and into reactivity, e.g. coal conversion behaviour (ref. 99). This information is often not available as easily from conventional techniques.

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Chapter 4

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