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Heterogeneous catalysts for biodiesel production

increase lipase stability for biodiesel production, albeit instance, demonstrated a surface area of 200 m /g and a
2
they are not covered in depth here. 97,98 Furthermore, the pore volume of 0.61 cm /g. This led to a 98% biodiesel
3
problems with other heterogeneous catalysts, such as output with a methanol-to-oil ratio of 20:1 and a
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high energy consumption, high manufacturing costs, catalyst loading of 1%. The use of lipases in conjunction
and complicated operating procedures, are lessened by with nanocatalysts has also been investigated in several
the enzymes. 99 hybrid studies. 112-115
Numerous techniques, such as co-precipitation,
2.5. Nanocatalysts as heterogeneous catalysts impregnation, gas condensation, chemical vapor
The increased efficiency of nanocatalysts over deposition, electrochemical deposition, vacuum
traditional catalysts has drawn a lot of interest in deposition, evaporation, microwave combustion,
biodiesel production. The two types of nanoparticles conventional hydrothermal processes, microwave-
employed for enzyme immobilization are magnetic and assisted hydrothermal and solvothermal methods, sol-
non-magnetic. Materials that are not magnetic include gel techniques, and self-propagating high-temperature
silica, polystyrene, chitosan, and polylactic acid. These synthesis, can be used to create nanocatalysts. 38,116
materials are further separated into synthetic renewable However, before these methods can be employed to
resources, which are used to make chemicals and produce biodiesel, they must be properly characterized
biopolymers. Silica is a frequently used framework as catalysts. An overview of the various nanocatalysts
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for immobilizing enzymes due to its outstanding utilized in the production of biodiesel is given in
mechanical qualities, high thermal and chemical Table 3, along with information on their input sources
resistance, low cost, non-toxicity, and good adaptability. and reaction parameters.
The adsorption capabilities of silica are also enhanced Table 3 presents a comprehensive overview
by its large surface area and porosity, which lessen of various nanocatalysts employed in biodiesel
diffusion limitations. In addition to noble metals, production from diverse feedstocks, highlighting their
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such as gold and silver, organic nanoparticles, such as reaction conditions and yields. For instance, Cs/Al/
metal oxides (such as zirconia, titania, and alumina) Fe O catalysts utilized methanol at a 14:1 molar ratio,
4
2
also function well as nanocatalysts. These substances 58°C for 2 h, achieving biodiesel yields ranging from
are well-known for their superior adsorption properties, 88% to 95% when applied to sunflower oil. Similarly,
high stability, and strong mechanical properties. Ca/γ/Al O catalysts processed corn oil with methanol
3
2
Under varying reaction conditions, the nano-metals in at a 12:1 molar ratio, 65°C for 5 h, resulting in yields
this category support distinct types of enzymes while between 34.64% and 87.89%. Cr/Ca/γ-Al O catalysts
3
2
remaining inert during the process. 102,103 used methanol at an 18:1 molar ratio, 65°C for 3 h,
The inability to separate non-magnetic nanoparticles achieving yields from 78.29% to 92.79% when applied
from the reaction product, a process that typically to cooking oil. MgO/MgAl O catalysts, both untreated
2
3
requires high-speed centrifugation, poses a significant and plasma-treated, processed sunflower oil with
challenge for their reuse, despite their excellent methanol at a 12:1 molar ratio, 110°C for 3 h, with a
dispersion in reaction solutions. One way to overcome yield between 79.30% and 96.50%. KOH/Fe O @Al O
2
4
3
3
this limitation is by attaching magnetic oxides, such catalysts employed methanol at a 12:1 molar ratio, 110°C
as magnetite to enzyme molecules, which facilitates for 4 h, achieving yields from 88.40% to 98.80% with
catalyst recovery. 104,105 Magnetite iron oxide is beneficial canola oil. CaO/CuFe O catalysts utilized methanol at
4
2
due to its large surface area, biological compatibility, a 15:1 molar ratio, 70°C for 4 h, resulting in a 94.52%
non-toxic nature, and hydroxyl groups that enable strong yield with chicken fat as the feedstock. 25%MoO /B-
3
covalent bonds with enzymes. Carbon nanotubes, 106-108 ZSM-5 catalysts processed oleic acid with methanol
nanofibers, and nanocomposites are other significant at a 20:1 molar ratio, 160°C for 6 h, achieving yields
109
110
nanoparticles that have been researched. between 93% and 98%. The significant advancements
Nanocatalysts provide many advantages, including in nanocatalyst development for biodiesel production
superior reusability, large surface area, higher stability, offer efficient and sustainable alternatives to traditional
greater catalytic activity, improved resistance to methods. The variation in yields across different
saponification, and effective surface-to-volume catalysts and feedstocks highlights the importance of
proportions. The properties increase enzyme loading optimizing reaction conditions to maximize biodiesel
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and reduce diffusion constraints. In an evaluation of production efficiency. The use of nanocatalysts not only
biodiesel synthesis, sodium titanate nanotubes, for enhances the catalytic activity but also facilitates the

Volume 22 Issue 5 (2025) 7 doi: 10.36922/AJWEP025130095