Abstract

CAMPANELLA, A.  and  BALTANAS, M. A.. Degradation of the oxirane ring of epoxidized vegetable oils in liquid-liquid systems: II. Reactivity with solvated acetic and peracetic acids. Lat. Am. appl. res. [online]. 2005, vol.35, n.3, pp.211-216. ISSN 0327-0793.

The impact of the main process variables (agitation, pH, temperature, concentration levels) on the degradation of the oxirane ring of epoxidized soybean oil (ESO) by attack by solvated acetic and peracetic acids in two-phase (polar-organic) systems when a homogeneous acid catalyst is used, is analyzed in detail. The first degradation reaction is first order with respect to the epoxide concentration and second order with respect to the solvated acetic acid [k_AA(70^oC) = 4.27 ± 0.12 × 10^-5 l² mol^-2 min^-1; Ea_AA = 12.9 ± 0.64 kcal mol^-1]. The degradation increases notoriusly the lower the pH of the reacting media is; the increase is directly proportional to the concentration of protons, as is usually found in homogeneous catalysis (for very low pHs the reaction is almost instantaneous). Likewise, the degradation reaction with peracetic acid is first order with respect to the epoxide [k_PAA(70^oC) = 4.31 ± 10^-4 l² mol^-2 min^-1; Ea_PAA = 10.6 ± 0.38 kcal mol^-1] and it also increases linearly with proton concentration. Although the specific attack on the ring by the peracid is almost 10 fold harsher, acetic acid is constantly being regenerated during the industrial process, so that its concentration is always far larger than that of peracetic acid. Thus, under process conditions the degradation of the oxirane ring is mostly caused by the carboxylic acid.

Keywords : Epoxidized Soybean; Degradation of Oxiranes; Solvated Acetic Acid; Peracetic Acid.

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