Neutralised mixtures of tall oil-derived fatty acids and resin acids were separately pyrolysed (at 750°C for 20？s) by pyrolysis gas chromatography with mass-selective and flame ionisation detection (Py-GC/MSD/FID) to clarify their thermochemical behaviour. The pyrolysate of fatty acid salts characteristically contained high amounts of unsaturated aliphatic hydrocarbons and minor amounts of monoaromatics, whereas the pyrolysis of resin acid salts mainly resulted in the formation of aromatics with up to three benzene rings and only in very low amounts of aliphatic hydrocarbons. The data obtained are useful when considering the suitability of various tall oil products containing fatty and resin acid fractions for the production of biofuels and chemicals via pyrolysis. 1. Introduction Both fatty acid and resin acid (i.e., tricyclic diterpenoids) components occur in the initial oleoresin fraction of coniferous wood species [1]. In the kraft pulping industry, tall oil soap, containing mainly the sodium salts of these acids, is removed by skimming from the spent cooking liquor “black liquor” during its evaporation before combustion in a recovery furnace to produce energy and recover the inorganic cooking chemicals [2]. Traditionally, the fatty and resin acids are liberated by adding sulphuric acid to yield crude tall oil (CTO, the average yield is in the range of 30 to 50？kg？ton？1 of pulp), which is then purified and fractionated by vacuum distillation. The main fractions and their mass proportions are light oil (10% to 15%), fatty acids (20% to 40%), rosin (25% to 35%), and pitch residue (20% to 30%). Various commercial fatty acid products from tall oil (TOFA) are available [3]. In general, monoenoic oleic (C18:1) and dienoic linoleic (C18:2) acids are common in most TOFA products, although during kraft pulping, the original dienoic and trienoic fatty acids with cis configuration are partly isomerised to acids with conjugated double bonds with mainly cis-trans configuration [4]. On the other hand, during kraft pulping as well as during the acidulation of tall oil soap, a general shift of fatty acid composition towards a lower degree of unsaturation has been reported [5]. The predominating resin acids in commercial tall oil rosin (TOR) are the abietane- and pimarane-type diterpenoids (Figure 1). The principal change in this fraction occurring during kraft pulping is the partial conversion of levopimaric acid into abietic acid. Furthermore, during tall oil distillation, some double-bond isomerisation of both abietane- and pimarane-type acids, disproportionation
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