Synthesis of Biodiesel from Tall Oil Fatty Acids by Homogeneous and Heterogeneous Catalysis

Gideon Lawer-Yolar,Emmanuel Atta-Obeng,Benjamin Dawson-Andoh

doi:10.3390/suschem2010012

Gideon Lawer-Yolar, Emmanuel Atta-Obeng + Show 1 more

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https://doi.org/10.3390/suschem2010012

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Abstract

This study compared the yield of biodiesel produced from tall oil fatty acids (TOFA) via (i) homogeneous catalyst (sulfuric acid) and (ii) a heterogeneous catalyst (Amberlyst® BD20, together with Ambersep BD 19 (Midcontinental Chemical Co., Olathe, KS, USA)® using a batch reactor. The effect of operation conditions including temperature, catalyst concentration, methanol: oil ratio and reaction time on esterification yield were investigated. Gas chromatographic data showed that the major fatty acids present in the TOFA are oleic acid (C18:1n9) and linoleic acid (C18:2n6). Homogenous catalysis yielded 96.76% biodiesel compared to 90.24% for heterogeneous catalysis. Optimized conditions for homogenous catalysis were at a catalyst concentration of 0.5 w/w%, 15:1 methanol: oil mass ratio at 55 °C for 60 min. FTIR results also showed that the homogeneous catalyst yielded a more complete reaction toward biodiesel production in a shorter time (60 min) compared to the heterogeneous catalyst (4.7 h). For heterogeneous catalysis, the highest yield and the lowest acid value were achieved after a second recycling because the reactants were not fully in contact with the catalyst during the first recycling. The catalyst did not show a reduction in catalytic activity even after the fourth recycling. However, the acid value was higher than that for ASTM standards for biodiesel.

Highlights

The continuous depletion of fossil fuels coupled with their negative impact on the environment has necessitated the search for alternate energy sources with lower environmental footprint
The present study describes a comparison between two different catalysts used for Tall Oil Fatty Acid (TOFA) esterification
Fourier transform infrared spectroscopy (FTIR) spectroscopy was used to monitor the progress of biodiesel synthesis from tall oil fatty acids using homogeneous catalyst, and heterogeneous catalyst (Amberlyst BD 20, from Dow Chemicals)

Summary

Introduction

The continuous depletion of fossil fuels coupled with their negative impact on the environment has necessitated the search for alternate energy sources with lower environmental footprint. Mostly the methyl and ethyl esters of fatty acids, is currently the subject of much attention because it is a clean, renewable and biodegradable source of energy [1]. Crude tall oil (CTO), the third largest chemical by-product of the pulp and paper industry, is an ideal feedstock for biodiesel production [2]. CTO can be distilled to make TOFA, a mixture of nearly pure free fatty acids (FFA). The global market for TOFA is expected to reach USD 1 billion in 2020 [3]. As the demand for naturally derived fatty acid-based biofuel increases, there needs to be sustained research focused on newer sources of biodiesel as well as improvements in their conversion processes

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