Optimization and Kinetic Studies on Biodiesel Conversion from Chlorella vulgaris Microalgae Using Pyrrolidinium-Based Ionic Liquids as a Catalyst

Noorhafizah Hasanudin,Asiah Nusaibah Masri,Noraini Abd Ghani,Ninna Sakina Azman,Nurhusna Aisyah Rosdi,Asyraf Hanim Ab Rahim

doi:10.3390/catal12030277

Noorhafizah Hasanudin, Asiah Nusaibah Masri + Show 4 more

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https://doi.org/10.3390/catal12030277

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Abstract

This study describes the potential conversion of dried microalgae. Chlorella vulgaris (C. vulgaris) into fatty acid methyl ester (FAME) using the direct transesterification (DT) method and using ionic liquids (ILs) as a catalyst. In this work, the performance of monocationic IL, namely 1-butyl-1-methylpyrrolidinium bromide (IL 1), and dicationic IL, namely 1,4-bis(1-methylpyrrolidinium-1-yl) butane dibromide (IL 2), as catalysts was compared for DT of C. vulgaris under microwave irradiation. The results revealed that IL 2 showed a better performance in catalyzing the DT reaction by producing 87.9 mg/g% of FAME, while the use of IL 1 led to 74.3 mg/g% of FAME under optimum conditions. The kinetic study for direct transesterification of C. vulgaris showed that the reaction followed a first order kinetic reaction where the activation energies were calculated to be 22.2499 kJ mol−1 and 22.0413 kJ mol−1 for IL 1 and IL 2, respectively.

Highlights

Biodiesel production from microalgae is one of the most significant alternative energy sources
The NMR spectroscopy for both ionic liquids (ILs) were presented in Supplementary Materials (Figures S1–S4)
We combined two environmentally benign methods, which were the use of microwave and ionic liquids (ILs), to assist the direct transesterification (DT) of microalgae to fatty acid methyl ester (FAME)

Summary

Introduction

Biodiesel production from microalgae is one of the most significant alternative energy sources. Microalgae offer the use of non-arable land for cultivation and grow rapidly throughout the year. It makes them a perfect substitute for liquid fossil fuels with respect to the cost, renewability and environmental concerns. The conversion of microalgae into biodiesel typically includes the dehydration of algae, lipid extraction, transesterification reaction catalyzed by homogenous acid or base catalysts and a purification process. There are some limitations in their use as a catalyst in transesterification, such as lower thermal stability of the biocatalyst, lower reaction rate and high enzyme cost [5]. It is sensible to explore more economic and feasible approaches for biodiesel production in respect to process route and the type of catalyst

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