Structural changes in rapeseed oil fatty acids methyl esters during ctalytic
oxidation at temperature 200°C
Polimery 2007, No 9, 658
Rapeseed oil methyl ester (Table 1) was oxidized at temp. 200°C in the presence of cobalt catalyst. Two competitive reactions are going during this process: formation and degradation of peroxides and hydroperoxides being intermediate products (Scheme A). After depletion of the most reactive structures with three or two unsaturated bonds in the material, the reaction of peroxides' decomposition becomes dominant so their concentration in the product decreases. The substrate and product examinations by FT-IR (Fig. 2) and 1H NMR (Table 2) as well as lowering of iodine value (Fig. 1a), confirm the double bonds decay. The content of structures with three, two or one unsaturated bond after 25-hour oxidation decreased about 98, 86 and 25% respectively (Table 3). Composition of volatile products of oxidation (Table 4) (aldehydes, ketones, acids, alkanes and alkenes, lactones and alkylfuranes) confirms the oxidative decomposition of unsaturated fatty acids chains. An increase in molecular weight of about 50% proves the partial oligomerization of substrate molecules (Fig. 1c).
Key words: asphalt fluxes, rapeseed oil methyl ester, catalytic oxidation, products of oxidation, oxidative oligomerization
I. Gaweł, Ł. Niczke, F. Czechowski
Structural changes in rapeseed oil fatty acids methyl esters during ctalytic oxidation at temperature 200°C