Production of vegetable oil-based biofuels—Thermochemical behavior of fatty acid sodium salts during pyrolysis

To develop an advanced pyrolysis process for various biomass-derived feedstocks and improve product quality and yield, in-depth investigations into the reaction mechanisms are needed. This paper reports on pyrolysis experiments (Py-GC/MSD and FID) with model compounds including the sodium salts of stearic (C18), oleic (C18:1), and linoleic (C18:2) acids principally obtained from alkaline hydrolysis of vegetable oils. Of the parameters studied – temperature (450–750 °C), time (20 s and 80 s), and the degree of unsaturation (i.e., saturated and mono- and dienoic C18-hydrocarbon chains) – the latter had the most significant effect on the formation of volatile compounds detected in pyrolysates. The results indicated that in the case of sodium stearate, a homologous series of alkenes and alkanes was formed, whereas the pyrolysis of sodium oleate resulted mainly in aromatics, alkenes, and alkanes. In contrast, the most abundant liquefiable volatile products obtained from sodium linolate were aromatics and oxygen-containing compounds. In each case, an increase in temperature and time generally increased the quantity of products formed.