(2023) Chemical Engineering Journal_Advances in synthesis of TiO² nanoparticles and their application to biodiesel production: A review

Obaid Ali Qamar, Farrukh Jamil, Murid Hussain, Sungjun Bae, Abrar Inayat, Noor S Shah, Ammara Waris, Parveen Akhter, Eilhann E. Kwon, Young-Kwon Park

https://doi.org/10.1016/j.cej.2023.141734

Biodiesel is a strategic measure to mitigate greenhouse gas emissions and other negative environmental impacts in line with oxidation of fossil fuels. Alkali-catalysed transesterification is the conventional production protocols in biodiesel production due to its technical reliability in line with low maintenance cost. Nonetheless, alkali-catalysed biodiesel production required to use the refined lipid feedstock due to low tolerance against impurities. TiO₂ NPs have been widely employed as heterogeneous catalysts. Also, the use of TiO₂ NPs could be beneficial because TiO₂ adaptation in production of biodiesel could combine transesterification and esterification into a single process. Nonetheless, the general protocol in TiO₂ NPs synthesis could not circumvent to use hazardous/toxic chemicals leading to serious/acute health and environmental problems. Several studies have demonstrated that green synthesis of TiO₂ NPs using microorganisms and plants as alternate approaches can eliminate the problems associated with conventional methods without sacrificing the exceptional features of these nano materials. Hence, the main objective of this review is to offer fundamental insights and recent advances in green methods for producing TiO₂ NPs driven by various microorganisms and plants extract along with quick summary of physio-chemical methods. In particular, the TiO₂ NPs with reduced sizes (<60 nm) are possible to obtain using cost effective and eco-friendly green synthesis. Moreover, activity of TiO₂ NPs as catalysts and their effect on biodiesel selectivity is discussed using catalytic trans-esterification, esterification, and simultaneous trans-esterification and esterification processes. The combinations of TiO₂ NPs with other metallic and non-metallic materials are very selective and efficient for biodiesel production upto 98 %. This study appeals to research communities for adopting green synthesized TiO₂ NPs as nanocatalysts for eliminating economic and environmental issues.

This work was supported by National Research Foundation of Korea(2021R1A2C3011274).