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Heterogeneous catalysts for biodiesel production

Another study examined Brassica nigra plant ash’s transesterification for biodiesel production. These
catalytic activity for transesterifying different vegetable catalysts, primarily composed of metal oxides, such as
oils. High catalytic performance was established by CaO, MgO, and K O, have demonstrated significant
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the calcined plant waste ash catalyst, which produced catalytic activity, offering a sustainable alternative to
biodiesel yields of up to 98.87%. According to Kordi conventional homogeneous catalysts. Tamarind fruit
et al., the catalyst’s high concentrations of calcium shell ash, containing CaO, MgO, and K O, achieved a
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(26.04 wt%) and potassium (56.13 wt%) as carbonates biodiesel yield of 96.2% from Parinari curatellifolia
and oxides were responsible for its success. In an seed oil under a 9:1 methanol-to-oil ratio and 5%
investigation on microwave-assisted transesterification catalyst load at 60°C for 2 h. Similarly, pineapple leaf
of soybean oil, zirconium dioxide-supported bamboo ash, rich in alkaline and alkaline earth metals, produced
leaf ash produced an ideal biodiesel yield of 92.75%. over 98% yield from soybean oil with a 40:1 methanol-
Another interesting catalyst generated from biomass to-oil ratio, 4% catalyst loading, and a 30-min reaction
ash is rice husk ash (RHA). Approximately 200 kg time at 60°C. RHA has been extensively studied for
of rice husk is generated for every ton of rice in rice- its catalytic properties. One study reported a biodiesel
producing nations, such as China and India. When yield of 99.5% from soybean oil using rice husk ash
completely combusted, they yield about 50 kg of as a catalyst under a 24:1 methanol-to-oil ratio, 4%
RHA. RHA could be a potential catalyst or pre-cursor catalyst loading, at 65°C for 3 h. Another study utilized
for amorphous silica since it is mostly made up of sodium silicate derived from RHA, achieving a 97%
silicon dioxide (87 – 99%). 194,195 Biodiesel generation yield from palm oil under a 12:1 methanol-to-oil ratio,
was studied using an RHA-based basic sodium silicate 2.5% catalyst loading, at 65°C for 30 min. Sugarcane
catalyst created by applying NaOH to the calcined ash. bagasse ash, when combined with CaO, has also shown
The catalyst reached a 97% FAME yield in 30 min while promising results. A study demonstrated a 93.8%
operating at optimal conditions, which included a 12:1 biodiesel yield from palm oil using silicon dioxide/
molar ratio of methanol to oil and a 2.5 wt% loading of CaO derived from sugarcane bagasse ash, under a 20:1
catalysts at 65°C. According to Dhawane et al., a methanol-to-oil ratio, 6% catalyst loading, at 65°C for
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lithium-modified RHA catalyst with high activity and 3 h. Wood ash catalysts, both calcined and activated,
basic strength of more than 15 m /g converted 99.5% have been effective in transesterifying Jatropha oil. The
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of the biodiesel at the molar ratio of methanol to oil methyl ester conversion achieved ranged from 97% to
of 24:1 and 4 wt% loading of catalysts at 65°C within 99%, depending on the specific catalyst preparation and
3 h. In addition, to produce heterogeneous catalysts reaction conditions. The potential of biomass-derived
that showed exceptional catalytic action in used frying ash catalysts in biodiesel production, highlighting their
oil transesterification, alkali metal hydroxides were efficiency, sustainability, and cost-effectiveness. The
impregnated onto silica from rice husks. The methyl variability in yields across different studies emphasizes
esters generated by these catalysts ranged from 96.5% the importance of optimizing catalyst preparation
to 98.2% when the following parameters were met: methods and reaction conditions to maximize biodiesel
65°C, a 9:1 methanol-to-oil ratio, 3% catalyst loading, production efficiency.
and an hour reaction period. High yields may be
obtained for up to six consecutive cycles without the 3.4. Carbon-based catalysts
need for reactivation due to the catalysts’ exceptional Biochar, a carbon-rich compound made from biomass,
reusability. 198 is frequently utilized as a catalyst support or to make
The calcined eggshell, which contains CaO, was also carbon-based heterogeneous catalysts. Carbon-based
loaded onto RHA to generate a new heterogeneous base catalysts and rock derived from biomass are not
catalyst. The maximum catalytic activity was shown by typically categorized as biocatalysts. These are materials
this catalyst, which had 30% eggshell loading on RHA created from biomass (plant matter) through processes,
calcined at 800°C. After eight cycles, it maintained more such as pyrolysis or carbonization. They can be used
than 80% efficiency and produced 91.5% biodiesel. as catalysts or catalyst supports in various reactions,
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A comparison of catalysts made of biomass ash from including those related to biofuels, energy production,
various sources and how well they operate in the and chemical processes. Their benefits include a vast
synthesis of biodiesel is tabulated in Table 6. surface area, structural stability, remarkable mechanical
Table 6 presents a comparative analysis of and thermal qualities, and affordability. Carbon-rich
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various biomass-derived ash catalysts utilized in biomass sources, including wood, coconut shells, and

Volume 22 Issue 5 (2025) 15 doi: 10.36922/AJWEP025130095