Optimization of reaction variables of ultrasound-assisted transesterification of Abelmoscus esculentus seed oil into biodiesel

Abstract

Ultrasound-assisted base-catalyzed transesterification of Abelmoscus esculentus seed oil was optimized for maximum biodiesel yield using Box–Behnken response surface design. Regression analysis of the results gave a robust empirical model with biodiesel yield being a function of catalyst concentration and methanol/oil ratio. In general, irrespective of the change in reaction temperature and time, the biodiesel yield increased with an increase in the catalyst concentration and methanol/oil ratio to the highest levels (> 95%) at a catalyst concentration of 0.70–1.48 % and methanol/oil ratio of 4.8–5.9. Optimal levels of the reaction variables for yields in excess of 97% were found at a moderate catalyst concentration of about 1.076 % and methanol/oil ratio of 5.24:1 when the reaction temperature and time were held at 30 °C and 20 min, respectively. The validation result (97.84 ± 0.17%) agreed with the predicted value of 97.3%. The mild optimal conditions could be linked to the ultrasonication employed for the reaction. Gas Chromatograph/Mass Spectrometer (GC/MS) results showed that the biodiesel was dominated by methyl esters of saturated and monounsaturated fatty acids, with oleic and palmitic acid methyl esters accounting for 79% of the biodiesel. Physicochemical properties of the biodiesel are generally in conformity with international standards for biodiesel, which makes the biodiesel suitable for use in a diesel engine.

Keywords:

• Abelmoscus esculentus
• okra
• biodiesel
• transesterification
• ultrasound

Disclosure statement

No potential conflict of interest was reported by the authors.