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Rajak, et al.

temperatures are frequently required for nanocatalysts to several reaction cycles is essential, and methods for
function, which raises the energy and cost requirements. improving catalyst performance have been put forth.
More economical and energy-efficient techniques are The experiments in Table 8 examine using catalysts
required to improve the recovery and repurposing of in a number of different reaction phases (three to ten
nanocatalysts, which can address present challenges in cycles), both with and without in-cycle reactivation
biodiesel production. treatments. During the fourth and fifth phases, some
studies indicate that the production of biodiesel only
9. Prospects of biomass-derived catalysts slightly decreases, staying at 90%. However, in some
situations, after the third cycle, there are notable drops
Novel approaches, such as solid-state fermentation in catalytic activity, which results in a yield loss of more
with solid whole-cell biological catalysts, have raised than 10%. Karmakar et al. for instance, found that
431
significant interest. This technique permits the direct use yield had stabilized at about 80% from the third to the
of crude fermented solids as biocatalysts by supporting tenth cycle but had decreased by 8% after the second
minimum microorganism growth on substrates, such as cycle. In addition, Reshad et al. observed that yields
432
agro-industrial waste. Complex lipase purification and in the first cycle fell short of 90%. With no change in
immobilization procedures are no longer required with performance from the first to the fourth cycles, the
this method. 423 catalysts did, however, show encouraging potential for
Hydro-esterification, which focuses on feedstocks reuse.
with high levels of FFAs and water, is another exciting A number of catalysts have been shown in several
advancement. This process consists of two steps: experiments to retain their reactivation procedures,
first, glycerol and FFAs are produced by hydrolyzing which are not required for stability and catalytic
mono- and triacylglycerols, and second, the FFAs are performance. To produce biodiesel from C. inophyllum
separated and esterified to create biodiesel. Researchers oil, Olatundun et al., for example, looked at the
433
424
have put forward methods, including solvent usage, repurposing of a catalyst based on cocoa pod husk
gradual methanol introduction, or continual glycerol ash. Centrifugation was employed to separate the
elimination using solvent extraction or dialysis, to catalyst from the biodiesel and glycerol once the
overcome methanol inhibition in enzymatic processes. In transesterification reaction was finished, and it was then
addition, a viable solution for this problem is recombinant reused without any further washing or heat/chemical
DNA technology. Furthermore, to decrease catalyst treatment. Notably, biodiesel yields were above 98%
425
inhibition and shorten reaction durations, continuous for three consecutive cycles, suggesting that there was
systems have been designed that utilize near-critical no discernible decrease in catalytic activity. In a similar
carbon dioxide as the reaction medium. 426 vein, catalysts made from Moringa oleifera leaf ash
The transformation of glycerol, an esterification demonstrated a biodiesel production of over 85% in the
by-product, into syngas represents an additional area first cycle, but by the third cycle, the output had dropped
of potential. Several techniques have been investigated by 30%, and the catalyst had darkened. This implies
for this purpose, such as supercritical water reforming, deactivation due to surface pollution, which probably
aqueous-phase transforming, and auto-thermal reduces the quantity of active servers. It was proposed
reforming. 427-430 Despite their continued high cost, the that high-temperature regeneration (over 500°C) was
usage of lipase methyl and ethyl acetate is growing as necessary after each cycle to restart the catalyst.
alcohol replacements in the manufacture of biodiesel. The repurposing of catalysts made from walnut
By preventing the synthesis of glycerol, this method shell ash, despite the use of heat during cycles, was
434
makes downstream separation and recovery easier and examined by Foroutan et al. They discovered that
produces triacetin, a higher-value product, which lowers there was a significant drop in FAME content (from
manufacturing costs. over 95% to about 30%) in the absence of reactivation.
Following 2 h of recalculation at 800°C, the catalyst
10. Recovered and utilized catalysts resumed its activity, and for four cycles, the reaction
yield surpassed 90%. On the other hand, the recalcined
The ability of heterogeneous catalysts to be recovered catalyst underwent structural alterations and a
and reused is one of their main benefits in the synthesis significant decrease in specific surface area. According
of biodiesel since it drastically reduces production costs. to them thermal reactivation also reduced the catalyst’s
However, maintaining catalyst stability throughout surface area, basicity, and acidity, which resulted in

Volume 22 Issue 5 (2025) 30 doi: 10.36922/AJWEP025130095