Energies (Jun 2020)
A Review on Bio-Based Catalysts (Immobilized Enzymes) Used for Biodiesel Production
Abstract
The continuous increase of the world’s population results in an increased demand for energy drastically from the industrial and domestic sectors as well. Moreover, the current public awareness regarding issues such as pollution and overuse of petroleum fuel has resulted in the development of research approaches concerning alternative renewable energy sources. Amongst the various options for renewable energies used in transportation systems, biodiesel is considered the most suitable replacement for fossil-based diesel. In what concerns the industrial application for biodiesel production, homogeneous catalysts such as sodium hydroxide, potassium hydroxide, sulfuric acid, and hydrochloric acid are usually selected, but their removal after reaction could prove to be rather complex and sometimes polluting, resulting in increases on the production costs. Therefore, there is an open field for research on new catalysts regarding biodiesel production, which can comprise heterogeneous catalysts. Apart from that, there are other alternatives to these chemical catalysts. Enzymatic catalysts have also been used in biodiesel production by employing lipases as biocatalysts. For economic reasons, and reusability and recycling, the lipases urged to be immobilized on suitable supports, thus the concept of heterogeneous biocatalysis comes in existence. Just like other heterogeneous catalytic materials, this one also presents similar issues with inefficiency and mass-transfer limitations. A solution to overcome the said limitations can be to consider the use of nanostructures to support enzyme immobilization, thus obtaining new heterogeneous biocatalysts. This review mainly focuses on the application of enzymatic catalysts as well as nano(bio)catalysts in transesterification reaction and their multiple methods of synthesis.
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