Biodiesel by Transesterification of Rapeseed Oil Using Ultrasound: A Kinetic Study of Base-Catalysed Reactions

José Encinar,Sergio Nogales,Nuria Sánchez,Ana Pardal

doi:10.3390/en11092229

José Encinar, Sergio Nogales + Show 2 more

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https://doi.org/10.3390/en11092229

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Abstract

The objective of this work was to study the acceleration that ultrasound causes in the rate of biodiesel transesterification reactions. The effect of different operating variables, such as ultrasound power, catalyst (KOH) concentration and methanol:oil molar ratio, was studied. The evolution of the process was followed by gas chromatography, determining the concentration of methyl esters at different reaction times. The biodiesel was characterized by its density, viscosity, saponification and iodine values, acidity index, water content, flash and combustion points, cetane index and cold filter plugging point (CFPP), according to EN 14214 standard. High methyl ester yield and fast reaction rates were obtained in short reaction times. Ultrasound power and catalyst concentration had a positive effect on the yield and the reaction rate. The methanol:oil molar ratio also increased the yield of the reaction, but negatively influenced the process rate. The reaction followed a pseudo-first order kinetic model and the rate constants at several temperatures were determined. The activation energy was also determined using the Arrhenius equation. The main conclusion of this work is that the use of ultrasound irradiation did not require any additional heating, which could represent an energy savings for biodiesel manufacture.

Highlights

The future development of world economy makes finding renewable sources of energy that can replace fossil fuels necessary
A lot of different raw materials have been used to obtain biodiesel. Edible vegetable oils such as canola and soybean oil in the USA, palm oil in Malaysia or rapeseed oil in Europe have been used for biodiesel production and found to be good substitutes for diesel
Before starting the study of the influence of variables, prior experiments in order to determine the optimal position of the probe in the reaction medium were carried out. In these experiments the methanol:oil molar ratio was 9:1, the concentration of catalyst (KOH) was 0.7% (w/w) and the power or amplitude of the probe was fixed at 40%

Summary

Introduction

The future development of world economy makes finding renewable sources of energy that can replace fossil fuels necessary. Biodiesel has been a real alternative to fossil fuels used in internal combustion engines [1]. As it is known, biodiesel is a fuel consisting of monoalkyl esters of long-chain fatty acids (FAME) derived from renewable lipid feedstocks, and it is generally produced via transesterification [2,3]. A lot of different raw materials have been used to obtain biodiesel Edible vegetable oils such as canola and soybean oil in the USA, palm oil in Malaysia or rapeseed oil in Europe have been used for biodiesel production and found to be good substitutes for diesel. As rapeseed oil has such a composition, that is the reason why it is frequently used for biodiesel production in Europe

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