Extraction and Characterization of Pequi Seed Oil for Biodiesel Production: A Green Management of Waste to Biofuel Using Ethanol and Heterogeneous Catalysis

Munique Guimarães,Grace Ghesti,Rafael Evaristo,Julio De Macedo

doi:10.21577/0103-5053.20210151

Abstract

This work reports the characterization of a vegetable oil extracted from pequi seeds, an agroindustrial residue, and its biodiesel production using ethanol and heterogeneous catalysis. The pequi seeds showed 40.73 wt.% of extractive content, which represents a large amount of the biomass composition. The crude oil extracted from the pequi seeds with ethanol as solvent presented a high content of free fatty acids (FFAs), mainly oleic (54.14%) and palmitic (36.71%) acids, resulting in an acidity value of 13.8 ± 0.1 mg KOH g-1. The esterification/transesterification process was performed using two ion exchange resins as heterogeneous catalysts, a commercial protonic form (assigned as PR) and a zirconium-exchanged (assigned as PRZr). Conversions of 87.1 and 91.4% were achieved for PR and PRZr as catalysts, respectively, at optimal conditions (1:6 oil-to-alcohol molar ratio, 25 wt.% of catalyst, 100 ºC and 1 h). These results indicated that heterogeneous acid catalysts can be successfully applied in biodiesel production from fatty acidrich oils, such as the one extracted from pequi seeds. Also, a simultaneous process involving both oil extraction and biodiesel production was tested using PRZr as catalyst (25 wt.% of catalyst and 100 ºC), but due to the greater amount of ethanol necessary for the oil extraction (1:16 oil to alcohol mass ratio) the conversion reached only 51.5% after 5 h. For that reason, this work proposes a two stage system for biodiesel production that integrates oil extraction (stage one) and the esterification/transesterification reaction (stage two) to achieve a greener process, waste-to-bioenergy.

Highlights

Integrated biodiesel systems can be used to execute both extraction and transesterification/esterification reactions in two-stages or simultaneously. These systems were already reported in small-scale processes using homogeneous catalysis and Extraction and Characterization of Pequi Seed Oil for Biodiesel Production
The other goals of this work are: (i) the characterization of pequi seeds and its crude oil; (ii) the preparation of a heterogeneous catalysts based on a zirconium-modified resin; (iii) the studied of an integrated approach for biodiesel production using both extraction and transesterification/esterification reactions
Compared to other agroindustrial residues, this value has great potential to be recovered as raw material for the production of biofuels, especially for biodiesel

Summary

Introduction

The use of biomass as eco-friendly fuels can be an efficient alternative to gradually replace fossil fuels and minimize its environmental issues.[1,2,3] Among the most utilized biofuels in the world, biodiesel has gained attention due to its origin, produced from vegetable oils or animal fats as raw materials, resulting in economic and environment benefits.[4,5,6] The biorefinery of unexploited solid wastes from food industrial processes promotes a sustainable biomass management.[7,8,9,10] For example, the use of raw cheap materials with adequate physicochemical properties for transesterification or esterification reactions could result in economically viable biodiesel processes.[11]The cost of biodiesel production is highly associated to the chosen fatty material, since oil extraction (mechanical press and/or solvent) and purification (degumming, deacidification, dephosphorylation, dehydration, etc.) will determine the reactional system used (transesterification or esterification), and the biofuel properties and value. The most common procedure used for biodiesel production (transesterification with methanol and basic homogenous catalysis) requires expensive refine vegetable oils.[12] biofuels from non-food or biomass residues, called 2nd and 3rd generation biodiesel, has gathered attention in terms of process viability and environmental benefits.[13,14] Integrated biodiesel systems can be used to execute both extraction and transesterification/esterification reactions in two-stages or simultaneously.

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