Continuous Biodiesel Production from Waste Soybean Oil Using a Nano-Fe3O4 Microwave Catalysis

Ching-Hsing Lin,Chien-Sen Liao,Tai-Ying Chiou,Yi-Tang Chang,Mei-Chou Lai

doi:10.3390/pr9050756

Abstract

In this study, we conducted an efficient microwave-assisted transesterification process combining homogeneous and heterogeneous catalytic phases to produce biodiesel from waste soybean oil. A cylindrical quartz reactor packed with nanoparticles of Fe3O4 as a co-catalyst was applied to improve the reaction. The process was carried out with a methanol-to-oil molar ratio of 6:1, power of 560 W, and residence time of 30 s. The specifications of the biodiesel produced in this study were compared with two standards, i.e., ASTM D6751 and EN 14214. We found that the continuous conversion of waste soybean oil to methyl ester was approximately 95%. The biodiesel showed a higher flash point and a higher carbon residue content than that of both standards, and the viscosity (5.356 mm2/s) and density (898.1 kg/m3) were both at a high level. Compared to a conventional heating plate, the energy consumption was significantly reduced by nearly 93%. It is expected that these findings will provide useful information for green and sustainable processes for the regeneration and reuse of oil.

Highlights

The biodiesel yield via a transesterification reaction depends on many parameters such as the concentration of catalyst, the presence of water and soap formation, the presence of free fatty acids (FFAs), and separation of glycerol [7]
The surface morphology of the Fe3 O4 co-catalyst was analyzed by scanning electron microscopy (SEM), since particle size is an important factor in microwave heating [31,33,35]
We found that the conventional heating plate method at a power of 420 W took 120 min to complete the reaction, whereas the continuous test of the new Fe3 O4 microwave catalytic heating system at a power of 560 W, took only 6 min to reach the same conversion rate, that is, to reach the same conversion rate, the conventional heating plate method consumed 0.84 kWh while the new Fe3 O4 microwave catalytic heating system consumed 0.056 kWh

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Due to the shortage of petroleum products, biodiesel has become more and more attractive as an alternative fuel resource. Transesterification is a well-established chemical reaction whereby vegetable oils and animal fats react with an alcohol to form fatty acid alkyl esters and glycerol [4,5,6]. The biodiesel yield via a transesterification reaction depends on many parameters such as the concentration of catalyst, the presence of water and soap formation, the presence of free fatty acids (FFAs), and separation of glycerol [7]. Transesterification is known as alcoholysis, and methanol and ethanol are the most common alcohols used in the reaction

Methods

Results

Conclusion