Catalysis in biodiesel production—a review

Abstract

Catalysts play a significant role in transesterification of vegetable oils. Currently, chemical and biological catalysts are being investigated, and both have their inherent merits and demerits. In large-scale applications, these catalysts are expected to be cost effective and environmentally friendly. If the catalyst is homogeneous in its physical form it is more effective than is the heterogeneous catalyst, but its separation from the mixture is a major issue. Some of the heterogeneous catalysts suffer leaching in harsh reaction conditions. Of late, nanocatalysts that demonstrate high efficiency are being studed. Nanoparticles are used in biological catalysts as solid carriers for lipase immobilization. Lipase immobilized on magnetic nanoparticles has proved to be a versatile biocatalyst for biodiesel production. This article reviews the role of various catalytic systems commonly used in the transesterification reaction of oils in biodiesel generation.

Effectiveness of biogenic waste‐derived heterogeneous catalysts and feedstock hybridization techniques in biodiesel production

“…Homogenous acid catalysts commonly used are sulfuric, phosphoric, hydrochloric, and sulfonic acids. They operate at slow reaction rates and high operating conditions 36, 65 . They are insensitive to water and to the high FFA content of the oil, and can be applied for both esterification and transesterification processes with high amounts of alcohols 60 .…”

“…Moreover, the challenge holds on the higher cost of the long‐chain alcohols, high temperatures to dissolve the alkaline catalyst, retention of wash water, which links to the formation of azeotropes, creating difficulties in separation of unreacted alcohols from the reaction mixture. Their reactivities are lower than short‐chained alcohols 65 . The higher alcohols are usually sensitive to water contamination and are also reported to be of less frequent use, which is a result of the steric hindrance effect 65, 107 .…”

“…Their reactivities are lower than short‐chained alcohols 65 . The higher alcohols are usually sensitive to water contamination and are also reported to be of less frequent use, which is a result of the steric hindrance effect 65, 107 . In the transesterification reaction, excess alcohol shifts the reaction towards completion and favors the formation of esters.…”

Batch to batch variation study for biodiesel production by hydrothermal carbon catalyst: preparation, characterization and its application

“…Biodiesel is obtained through transesterification process which is a simple process for conversion of fats and oils into respective esters. However, there are few factors affecting the transesterification process, for example; humidity, reaction temperature, mixing speed, type of catalyst, type of alcohol, reaction time and alcohol: oil molar ratio [5][6][7][8]. In the transesterification reaction, three types of catalysts are generally used, i.e.…”

“…homogeneous or heterogeneous catalysts and biocatalysts [9]. Likewise, NaOH or KOH or sulfuric acid is used for the preparation of biodiesel as homogeneous catalyst [8]. Nonetheless, homogeneous catalysts have many limitations such as equipment corrosion and handling of the waste product obtained after the neutralization.…”