Carbon-Based Catalysts for Biodiesel Production—A Review

Jack Clohessy,Witold Kwapinski

doi:10.3390/app10030918

Abstract

In recent years, a new class of superior heterogeneous acid catalyst for biodiesel production has emerged. These catalysts offer advantages over their predecessors such as high surface area, elevated acid site density, enhanced catalyst activity, good operation stability and relevant economic affordability in an environmentally friendly frame. This review was concerned with carbon-based solid acid (CBAS) catalysts derived from both carbohydrate and pyrolysis products. A series of CBASs with various origins such as D-glucose, sucrose, starch, cellulose and vegetable oil asphalt, converted to char and sulphonated, have been explored as potential heterogeneous catalysts. Catalyst preparation and synthesis methods were briefly summarized. Catalyst characterization and performance for biofuels related reactions were elucidated, identifying potential research applications. Three catalysts in particular were identified as having potential for industrial application and requiring further research.

Highlights

There has been a spike in interest in fossil fuel alternatives in recent years due to growing concerns regarding the environmental impact of fossil fuel usage
According to the report by the IPCC [1], human-induced global warming reached approximately 1 ◦ C above pre industrial levels in 2017. Among these alternatives is biodiesel, a substitute for traditional petrochemical diesel, that is composed of fatty acid methyl esters (FAMEs) and can be used in diesel compression engines without modification [2,3]
Homogenous acid catalysis is insensitive to free fatty acids (FFAs) content and has the potential to carry out simultaneous esterification and transesterification

Summary

Introduction

There has been a spike in interest in fossil fuel alternatives in recent years due to growing concerns regarding the environmental impact of fossil fuel usage. Second-generation biodiesel production utilises lower-cost inedible feedstock or waste cooking oils, and these lower-grade plant oils and waste oils often have elevated FFA and water content, making homogeneous base catalysis an economically unfavourable process [11,19]. Homogenous acid catalysis is insensitive to FFA content and has the potential to carry out simultaneous esterification and transesterification. Despite this distinct advantage, homogeneous acid catalysis presents the same separation issues as homogeneous base catalysis. Heterogeneous acid catalysis is a promising alternative to conventional biodiesel production due to the simplistic and environmentally friendly nature of the process and the simultaneous promotion of both esterification and transesterification [37,38,39]. This review will focus on the different types of CBASs currently being researched, preparation methods, and classification as catalysts and effectiveness in terms of both esterification and transesterification

Carbohydrate Precursors

Biomass Precursors

Method B

Economic and Operating Condition Assessment

Findings

Conclusions