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Rajak, et al.

earth oxides in transesterification processes, with and quality. Advancements in catalyst development,
particular attention to the effects of oxides of calcium, such as the use of biomass-derived heterogeneous
magnesium, strontium, and barium that have been treated catalysts, aim to improve the efficiency and sustainability
at elevated temperatures for reactions between 500°C of FAME production, thereby contributing to more
and 1,050°C. 291,292 In using methanol to transesterify cost-effective and environmentally friendly biodiesel
vegetable oil under reflux circumstances, CaO has production methods. In essence, the review likely
been identified as an efficient catalyst. 293-295 These explores how biomass-derived heterogeneous catalysts
investigations show that CaO’s fundamental features can improve the efficiency, sustainability, and economic
enable it to speed up transesterification processes viability of FAME production, which is the foundation
mainly through a nucleophilic mechanism. of biodiesel synthesis. Both the chemical and physical
Other compounds, such as calcium hydroxide, characteristics of the distinct fatty acid esters in
CaCO , MgO, and barium hydroxide have also been biodiesel dictate its qualities. Thus, the ultimate product
3
shown to exhibit comparable behavior, demonstrating is largely determined by the solvent employed, the
the well-documented nucleophilicity of CaO, which feedstock’s molecular structure, and its content.
increases its susceptibility to nucleophilic assaults. Significant research has been conducted over the past
Higher calcination temperatures (270°C) have been 20 years to find catalysts that produce certain FAME
demonstrated to activate more sites, especially for profiles and attributes. 301-304 Although catalysts’ effects
MgO. Research showed that strontium oxide catalysts, on yield have been well investigated, it is still not
which were produced by thermal decomposition at known how they affect the qualitative characteristics
1,200°C, had lengthy catalytic lifetimes and unusually of biodiesel. 305,306 Consequently, the comprehension of
high FAME yields, with the ability to be reused for up catalyst activity under dynamic reaction settings remains
to 10 cycles. Due to its economic viability, strontium a challenge for researchers. In addition, the literature
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oxide is a promising catalyst that might lower the cost emphasizes various heterogeneous solid catalysts for
of producing biodiesel. acids and bases utilized in transesterification, such
as salts supported on hydrotalcites, zeolite, alumina,
5.1. Impact of base-and acid-catalyzed reactions on alkali metals, hydroxides, and alkaline earth metal
methyl esters of fatty acid production oxides. The transesterification of vegetable oils using
The abundance of acid and basic sites (or surfaces) of both solid base catalysts has been extensively studied, with
types of catalysts has a major impact on their catalytic various reaction parameters reported in the literature.
activity and selectivity. However, there are difficulties As an example, high reactivity was demonstrated at low
in determining these densities throughout the process temperatures by potassium iodide, potassium fluoride,
of transesterification. Compared to acid catalysts, solid and potassium nitrate catalysts based on alumina, as
base catalysts are often recognized for their greater salt reactions supported aluminum-oxygen-potassium
reactivity and quicker reaction rates. Despite these groups or K O species to generate basic sites. By
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308
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benefits, base catalysts are extremely vulnerable to FFAs ionizing sodium or potassium during transesterification,
and water. Base catalysts need minimal FFA feedstocks Na/NaOH/γ-Al O and K/KOH/γ-Al O catalysts also
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to prevent catalyst deactivation and guarantee effective created strong base sites. Nonetheless, leaching was
309
biodiesel production. On the other hand, for catalysts shown to be a problem, suggesting chemical instability
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made of solid acid to provide FAME yields that are under the circumstances of the reaction. However,
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acceptable, greater reaction temperatures and catalyst calcium nitrate/aluminum oxide showed good efficiency
loadings are necessary, despite being able to tolerate of conversion and stability during transesterification,
high water and FFA concentrations. 299,300 making it a viable catalyst for the manufacture of
Methyl esters of fatty acids are produced through biodiesel in the future. 311
the transesterification of triglycerides, and the use of
biomass-derived heterogeneous catalysts is a significant 5.2. Impact of solid catalysts on transesterification
area of research aimed at enhancing the sustainability reactions
and cost-effectiveness of this process. The production of The interplay between acidic and basic sites determines
FAME is directly linked to biodiesel synthesis, as FAME a material’s acidity. A solid acid catalyst must be
constitutes the bulk of biodiesel’s composition. This capable of proton donation or transfer for it to interact
relationship underscores the importance of optimizing with surface anions with regard to Brønsted acidity.
FAME production processes to enhance biodiesel yield Furthermore, when interacting with base molecules on

Volume 22 Issue 5 (2025) 22 doi: 10.36922/AJWEP025130095