Читать книгу Liquid Biofuels - Группа авторов - Страница 45

As discussed in the preceding sections, the process intensification can occur in the cavitational reactors through the process of cavitation phenomena, i.e., transient collapse of tiny bubbles due to pressure variation in the liquid media. The various studies published over the last few years have demonstrated the successful application of ultrasound irritation or sonication in process intensification for different chemical processes including biodiesel production. In this section, some critical studies related to process intensification of biodiesel synthesis, especially with the utilization of a heterogeneous catalyst, are presented briefly. Moreover, state-of-the-art reviews focusing on sonication as a tool for process intensification of biodiesel synthesis are discussed as follows. Lam et al. [33] published a comprehensive review on the homogeneous, heterogeneous, and enzymatic catalysts for biodiesel production. The authors discussed various methods for intensifying the transesterification reaction and lowering the heterogeneity of the system through the application of co–solvent method, oscillatory flow reactor system, microwave mixing, and ultrasound-assisted system. Ramachandran et al. [34] reviewed the developments in the heterogeneously catalysed biodiesel the production in presence of ultrasound irradiation. The review concludes that ultrasonic energy emulsifies the reactants to reduce the catalyst requirement, methanol–oil ratio, reaction time, and reaction temperature compared to conventional mechanically agitated systems. Lerin et al. [35] overviewed the ultrasound-assisted enzymatic esterification and transesterification reactions for biodiesel production. The review figured out the advantages of sono-chemical reactors for the production of biodiesel at a commercial scale. Islam et al. [36] had compared various advancements in catalytic and non-catalytic reactions for biodiesel production with the application of ultrasound as a tool for process intensification. The review published by Lourinho and Brito [37] analysed the novel developments in biodiesel production in terms of feedstock selection and process intensification. They discussed different operational aspects of process intensification technologies among ultrasound irradiation, microwave heating, co-solvents, and membrane reactors for economic biodiesel production. Ho et al. [38] summarized the advances in ultrasound-assisted transesterification reaction. The authors critically appraised current technology’s status on the application of ultrasound energy in conjunction with heterogeneous catalysts for biodiesel production. Chuah et al. [3] discussed issues of cleaner intensification technologies in biodiesel production and emphasized application of hydrodynamic cavitational reactors for biodiesel production at large-scale level, over ultrasonic cavitation and conventional mechanical agitation. Gude and Martinez-Guerra [39] assessed the process of intensification in sustainable biodiesel production using a green chemistry approach. They compared the reaction efficiency between the conventional mechanical agitation, microwave, and ultrasound-enhanced biodiesel synthesis.

The literature published on cavitation-assisted biodiesel synthesis can be categorized based on the type of cavitation employed, viz., acoustic cavitation and hydrodynamic cavitation.