The pyrolysis products were grouped according to their chemical structure into the following classes: (i) aliphatic compounds (homologous scries of n-alkanes and n-alkenes, and branched alkencs), (ii) lignin-derived methoxyphenols, (iii) phenols, (iv) monocyclic aromatic compounds (MAHs), (v) polycyclic aromatic hydrocarbons (PAHs), (vi) N-containing compounds, (vii) carbohydrate-derived pyrolysis products, and (viii) unidentified compounds.
1991), or more frequently interpreted as analytical artefacts because of evidence of their formation during pyrolysis of aliphatic compounds through cyclisation and aromatisation (Saiz-Jimenez 1994/?).
In sample S2, KMn[O.sub.4] oxidation (MN-2) (with a smaller decrease of OC, 1.3 mg [g.sup.-1]) caused a strong decline in carbohydrate products (from 31.5% of TQPA in NO-2 to 17.4% in MN-2) and an increase in aliphatic pyrolysis products (sum of n-alkanes, n-alkenes and other aliphatic compounds from 5.3% in NO-2 to 23.1% in MN-2).
It is not possible (according to the available knowledge) to eliminate the formation of PAH in the obtained oil without elimination or decreasing the aromatization processes via secondary reactions through either a Diels-Alder type reaction or selective cracking of aliphatic compounds resulting in selective concentration of aromatic compounds.
* The formation of aromatics via secondary reactions during pyrolysis has been attributed to Diels-Alder type reactions or to gas-phase cracking of aliphatic compounds resulting in selective concentration of aromatic compounds.