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Rajak, et al.

such as landfilling and cement production. Dolomite’s More than 13 different metal oxides have been
catalytic efficacy is increased when it is calcined, giving investigated in the production of biodiesel by
it a larger surface area than when it is uncalcined in transesterification. These oxides include calcium,
nature. The application of calcined dolomite as a catalyst barium, magnesium, and lanthanum oxides. The findings
has been the subject of several studies. 227,228 The range imply that catalysts derived from calcium exhibit higher
of reported FAME transformation yields using dolomite catalytic activity within this procedure. Since CaO is
is 92% to 99%. Furthermore, structural modifications readily available, inexpensive, and has a lower toxicity
to dolomite by hydrating and dehydrating have been than other catalysts, it is particularly preferred for the
investigated and shown to boost FAME transformation production of biodiesel. 238,239
yields from93% to 97.4%. 229,230
4.2. Calcination application
4. Methods of catalyst preparation One method that is frequently used to create catalysts
from biomass is calcination. By applying heat without
Heterogeneous catalysis in transesterification involves the presence of air or oxygen, biomass is broken
three separate phases: a solid catalyst and two down into smaller components. Temperatures for
240
immiscible liquids (methanol and oil). This makes the the calcination process usually range from 300°C
process complicated, and side reactions, such as the to 1,000°C, depending on the type of material used.
neutralization of FFAs with glycerol and methyl esters, Carbon dioxide gas is released as molecules, such as
may also occur throughout the process. 231-233 CaCO break down into CaO during this procedure.
3
Numerous techniques for creating solid catalysts for The solid base catalysts made from biomass, created
transesterification have been discussed in the literature. using calcination, for the manufacture of biodiesel
These consist of impregnation, heat treatment, physical by transesterification are summarized in Table 7. The
mixing, and hydrothermal synthesis. The specific particular feedstocks utilized, the types of biomass
physical and chemical characteristics required for the employed, the reaction conditions, and the related
final catalyst determine the selection of the synthesis references are all listed in the table. A key factor in
method to be used. 234 defining the surface shape of the CaO catalyst is the
calcination temperature. Many waste materials, such
4.1. Catalyst selection as shells, are originally non-porous; however, during
Metal oxides are Lewis acidic and Brønsted basic calcination, pores form on their surfaces, which can
because they are composed of negatively charged anions significantly impact the final catalyst’s surface area. The
and positively charged metal cations. These properties calcination temperature changes the distribution and
make metal oxides essential for the transesterification intensity of active sites, impacting a catalyst’s catalytic
procedure, methanolysis of oils, which produces activity. Numerous investigations, including those
241
biodiesel. Methanol binds to metal oxides in large conducted by researchers, have examined the impact of
quantities, where the O-H link can be broken to produce calcination on catalyst production. 242-244
hydrogen cations and methoxide anions. Table 7 presents the elemental composition of
Catalyst preparation techniques have been studied in various solid base catalysts derived from agricultural
the literature. In the synthesis of biodiesel, for instance, and organic wastes through calcination processes.
it has been discovered that adding a small quantity of The data reveal significant variations in alkali and
water increases the catalytic action of CaO. Oxygen alkaline earth metal contents, which are crucial for
235
on the catalytic surface releases hydrogen ions in the catalytic activity in transesterification reactions.
presence of water, forming hydroxide ions. These Potassium emerges as the predominant component
hydroxide ions then release hydrogen ions from in most catalysts, particularly in Musa spp. peduncle
methoxide anions, which serve as the crucial catalytic (68.37%) and Carica papaya stem (56.71%), while
species in the transesterification process. According calcium shows notable concentrations in Tectona
236
to noteworthy research, methanol adsorption is a crucial grandis leaves (30.28%) and S. indicum (33.80%).
rate-determining step in processes combining MgO and The calcination conditions (500 – 900°C for 2 – 4 h)
lanthanum(III) oxide. Higher basicity catalysts, such significantly influence the final catalyst composition,
as barium oxide, CaO, and strontium oxide, have a with higher temperatures generally enhancing metal
rate-determining step that is connected to the surface oxide formation. Sweet potato leaves calcined at 900°C
reaction. 237 contain 65.45% potassium, whereas Moringa leaves

Volume 22 Issue 5 (2025) 18 doi: 10.36922/AJWEP025130095