Comparative Evaluation of Catalytic Systems for Soybean Oil Epoxidation Based on Physicochemical Properties and Process Performance

Abstract

Epoxidized soybean oil (ESBO) is a valuable bio-based intermediate for plasticizers, adhesives, and biocomposites, yet the influence of catalytic system selection on its physicochemical properties remains insufficiently benchmarked under standardized conditions. This study comparatively evaluated three catalytic epoxidation systems for soybean oil (SBO); (i) 85% formic acid (FA) with 35% hydrogen peroxide (H 2 O 2 ), (ii) FA combined with sulfuric acid (H 2 SO 4 ) and H 2 O 2 , and (iii) glacial acetic acid (AA) with H 2 O 2 , under identical reaction conditions (65 °C, 600 rpm, H 2 O 2 loading of 2 mol/mol of C=C, 50 min addition time ( t add ), and 6 h stirring ( t str ), for a total reaction time ( t ) of 6.8 h). The resulting epoxidized products (ESBO1, ESBO2, and ESBO3, respectively) were characterized for oxirane oxygen content (OOC), iodine value (IV), acid value (AV), viscosity ( η ), density ( ρ ), color, and conversion of unsaturation ( X SBO ). The AA system (ESBO3) achieved the highest OOC (6.8 wt%), the lowest IV (1.91 ± 0.01 g/100 g) and AV (0.60 ± 0.01 mg KOH/g), the highest η (332 ± 1 cP) and ρ (0.996 ± 0.001 g/mL), and the lightest product color, corresponding to an X SBO of 98.53% within 6.8 h. In contrast, the FA-only system (ESBO1) exhibited the lowest OOC (3.5 wt%) and the highest IV (8.65 ± 0.01 g/100 g) and AV (0.87 ± 0.01 mg KOH/g), while the mixed FA/ H 2 O 2 system (ESBO2) showed intermediate performance (OOC 5.8 wt%; IV 3.12 ± 0.01 g/100 g). These results, which are comparable to or exceed literature benchmarks (OOC 6.2–7.45 wt%; X SBO 95.2–98.53% at t of 2.3–10.42 h), indicate that AA system provides a superior balance of epoxidation efficiency, product stability, and t relative to FA systems, and represents the most promising catalytic procedure for the epoxidation of SBO under the tested conditions.

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