Abstract
Ethyl ester production from palm fatty acid distillate (PFAD) with ethanol in the presence of sulfuric acid and potassium hydroxide was performed in a continuous three-step process using the ultrasound clamps and an ultrasonic probe. The ultimate goal was to produce biodiesel from the PFAD. In the first and second esterification steps, 16 units of a 400 W ultrasound clamp (20 kHz) were attached 100-m apart along each tubular reactor. In the third transesterification step, a 1000-W ultrasonic homogenizer (18 kHz) was used in a 100-mL continuous reactor. A composite central design of experiments and the response surface methodology (RSM) were used to develop predictive models and identify the optimal conditions of each step based on the purities of ethyl ester. The optimal conditions in the first step were 46.1 vol.% ethanol, 1.4 vol.% sulfuric acid, and purity 66.68 wt.% ethyl ester. In the second step, the optimized conditions were 57 vol.% ethanol, and 2.1 vol.% sulfuric acid, purity 95.32 wt.% ethyl ester. The final transesterification step was carried out with 14.6 vol.% ethanol and 3.9 gKOH L−1. As a result, a final ethyl ester purity of 98.15 wt.% was achieved in the biodiesel using the three-step process.
Highlights
A by-product of the production of refined palm oil (RPO) is a low-cost product known as palm fatty acid distillate (PFAD) [1]
A 5-m-long helical static mixer (HSM) was installed to mix the PFAD, ethanol, and sulfuric acid; subsequently, the mixture flowed through the US tubular reactor
The results show that the ethyl ester purity sharply increased as the ethanol loading was varied between 35 and 57 vol.%, and the ethyl ester purity increased significantly when more than 57 vol.% ethanol was used in the reaction
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. A by-product of the production of refined palm oil (RPO) is a low-cost product known as palm fatty acid distillate (PFAD) [1]. PFAD is not edible and is commonly used as a feedstock for the production of soap, animal feed, and oleochemical products [2]. Vitamin E, which has a high market value, is extracted commercially from PFAD, so it can be used as a feedstock for health foods and in the pharmaceutical industry [3]
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