Available online at website: https://journal.bcrec.id/index.php/bcrec

Bulletin of Chemical Reaction Engineering & Catalysis, 19 (3) 2024, 372-383
Research Article

Exploring Alkali Hydroxide Influence on Calcium Titanate
Formation for Application in Biodiesel Catalysts
Ratchadaporn Puntharod*, Kittikarnkorn Onsomsuay, Pusit Pookmanee, Jaturon
Kumchompoo
Department of Chemistry, Faculty of Science, Maejo University, Chiang Mai, 50290, Thailand.
Received: 12th June 2024; Revised: 18th July 2024; Accepted: 19th July 2024
Available online: 22th July 2024; Published regularly: October 2024

Abstract
Biodiesel has been recognized as the most widely utilized biofuel around the world due to its significant role in reducing
the consumption of crude oil and lowering environmental pollution levels. By serving as a renewable alternative to
fossil fuels, bioethanol helps decrease greenhouse gas emissions and contributes to a more sustainable energy future.
Traditionally, alkali hydroxides like NaOH and KOH have been mainstays in biodiesel synthesis. However, their
overuse can lead to unwanted byproducts and operational complexities. Since calcium titanate can occur at a strong
base condition, it presents an alternative avenue worth exploring. In this study, we investigate the influence of alkali
hydroxides, namely LiOH, NaOH, and KOH, on the formation of calcium titanate through hydrothermal methods, with
varying heating times. We aim to understand how different hydroxides affect the synthesis process and the resultant
properties of calcium titanate. We delve into the vibrational properties of Ca−O−Ti and Ti−O bonds using Fourier
Transform Infra Red (FTIR) spectroscopy, confirming the presence of calcium titanate (JCPDS No.42-0423) through Xray Diffractometry (XRD). This thorough characterization provides insight into the structural integrity and composition
of the synthesized materials. Moreover, Scanning Electron Microscopy (SEM) reveals the intriguing cube-like
morphology of calcium titanate, offering visual evidence of its unique structure. The fatty acid methyl ester
impressively show that calcium titanate synthesized in 7 M NaOH and KOH solutions, heated for 24 h, emerges as a
promising biodiesel catalyst. We observe fatty acid methyl ester provides the percentages of 63.67% and 90.02%,
respectively, indicating the catalytic efficacy of these materials in biodiesel production. These findings not only
contribute to the understanding of calcium titanate synthesis but also pave the way for a sustainable future in biodiesel
production by introducing efficient and eco-friendly catalysts.
Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC
BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Keywords: CaTiO3; alkali hydroxide; biodiesel catalyst; transesterification; hydrothermal
How to Cite: R. Puntharod, K. Onsomsuay, P. Pookmanee, J. Kumchompoo (2024). Exploring Alkali Hydroxide
Influence on Calcium Titanate Formation for Application in Biodiesel Catalysts. Bulletin of Chemical Reaction
Engineering & Catalysis, 19 (3), 372-383 (doi: 10.9767/bcrec.20165)
Permalink/DOI: https://doi.org/10.9767/bcrec.20165

1. Introduction
Titanate-based
materials
have
found
widespread application across various domains.
For instance, titanate nanotubes have been
utilized in photocatalytic water decontamination
[1], while calcium copper titanates (CaCu 3Ti4O12)
serve in resonators, capacitors, and sensors [2].
The spinel lithium titanate (Li4Ti5O12) has
garnered attention for its role in energy storage
* Corresponding Author.
Email: ratchadaporn_p@mju.ac.th (R. Puntharod);
Telp: +66-53-873850-1, Fax: +66-53-873950

devices [3], and the emergence of ferroelectric
properties in ATiO3 compounds (where A = Ca, Sr,
Ba) has been investigated [4]. A particularly
intriguing application of titanate complexes lies in
biodiesel catalysis. Nanotubular sodium titanate
(Na2Ti3O7.nH2O) has demonstrated remarkable
efficiency, yielding up to 100% biodiesel [5].
Likewise, strontium titanate perovskite has
shown promise as a heterogeneous catalyst, with
reusability observed for up to six cycles and a 79%
yield of fatty acid methyl ester [6]. Additionally,
sodium titanate variants (Na2Ti3O7 and

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Bulletin of Chemical Reaction Engineering & Catalysis, 19 (3), 2024, 373
Na2Ti6O13) have been utilized in the conversion of
vegetable oil to biodiesel [7]. The advantages of
CaTiO3 likely include its catalytic activity and
selectivity in the transesterification reaction for
biodiesel production. Using a factorial design
allows researchers to systematically vary
synthesis parameters and optimize the catalyst's
properties. CaTiO3 may offer advantages such as
high
stability,
efficiency
in
converting
triglycerides to biodiesel, and potentially lower
cost compared to other catalysts.
Calcium titanate (CaTiO3), characterized by
its perovskite structure, has emerged as a
versatile material with wide-ranging applications.
It serves as an electrode material for
electrochemical
urea
sensing
[8]
and
demonstrates efficacy in the photocatalytic
degradation of methylene blue, as well as in
biodiesel catalysis [9]. In the biodiesel production
landscape, alkali hydroxides, like NaOH and
KOH, are commonly employed as homogeneous
catalysts, albeit with the drawback of
necessitating additional steps and expenses for
neutralization [10,11]. Heterogeneous catalysts
present an attractive alternative, promising cost
reduction and yields exceeding 90% [12].
Among the various alternative fuels that are
available, those derived from naturally harmless
vegetables emerge as the most preferable and
advantageous option, due to their potential to
serve as an effective and sustainable energy
source. In particular, waste cooking oil stands out
as a remarkably promising and viable candidate
for contributing to the enhancement of
sustainability efforts, the improvement of energy
efficiency, and, perhaps most crucially, the
preservation of energy resources for future
generations. This is because, when repurposed,
waste cooking oil can be transformed into a
renewable energy source that not only helps to
reduce environmental impact but also supports
long-term energy conservation goals. Herein lies
the appeal of CaTiO3 as a biodiesel catalyst.
Utilized in transesterification reactions, CaTiO 3
offers distinct advantages, notably its facile
separation from the reactants, enhancing process
efficiency and scalability. Synthesizing calcium
titanate as a heterogeneous biodiesel catalyst
offers a spectrum of methods, each tailored to
specific reactants and applications. Green
synthesis, utilizing leaf extracts [13], alongside
techniques like sol-gel-hydrothermal synthesis
[14], solid-state reaction [15], and spray pyrolysis
[16], exemplify the diverse approaches available.
The choice of synthesis method hinges upon
various factors. Notably, the influence of alkali
hydroxides, comprising alkali metals and
hydroxide ions, cannot be overlooked [17,18].
Dong et al. [19] elucidated the pivotal role of
sodium hydroxide in calcium titanate formation,

as its occurrence is favored under strong base
conditions. For instance, Dong et al. [20]
demonstrated the solvothermal synthesis of
calcium titanate at 180 °C, employing calcium
chloride dihydrate and titanium tetrabutoxide as
precursors, with pH adjustment to 12 using 7 M
sodium hydroxide [20].
In 2020, our research group successfully
synthesized silicate compounds from LiOH and
KOH to produce lithium silicate (Li2SiO3) and
potassium
silicate
(K2SiO3)
using
the
hydrothermal microwave method. These silicates
can serve as heterogeneous biodiesel catalysts.
The results indicate that K2SiO3 represents the
optimal alkali silicate for achieving a high weight
percentage of fatty acid methyl esters (FAME),
approximately 88.40% [21]. In this research, we
investigated the effects of various alkali
hydroxides on the synthesis of CaTiO3. The
research delved into the impact of alkali
hydroxides lithium hydroxide, sodium hydroxide,
and potassium hydroxide on the formation of
calcium titanate. Utilizing calcium carbonate and
titanium dioxide as precursors, calcium titanate
synthesis via the hydrothermal method was
chosen for its ability to yield highly crystalline
products. Characterization of the synthesized
materials was conducted using Fourier transform
infrared
spectroscopy,
scanning
electron
microscopy,
and
X-ray
diffractometry.
Subsequently, the synthesized calcium titanate
was evaluated for its catalytic efficacy in the
transesterification
reaction
for
biodiesel
production.
2. Materials and Methods
2.1 Preparation of Calcium Titanate
The experiment involved dissolving 3.00 g of
calcium carbonate (CaCO3, Unilab, 97.55%) and
2.40 g of titanium dioxide (TiO2, Loba, 98%) in 3
ml of concentrated nitric acid (HNO 3, RCI
Labscan 65%) each. Both solutions were heated
and stirred with a magnetic bar until
homogeneous.
Subsequently,
the
calcium
carbonate solution was slowly added dropwise to
the titanium dioxide solution. The resulting
mixture was then adjusted to a volume of 12 mL
using deionized water and heated further.
Following this, each solution was gradually mixed
with 15 mL of 7 M lithium hydroxide (LiOH,
Fisher Chemical, 100%), sodium hydroxide
(NaOH, Fisher Chemical, 97%), and potassium
hydroxide (KOH, Qrec, 85%). The resulting
mixture was transferred to a Teflon tube and
heated at 180 °C in a hot air oven for 18 and 24 h.
The filtered product was then heated at 90 °C
for 6 h. Finally, the solid product was
characterized using Fourier transform infrared
spectroscopy, scanning electron microscopy, and

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Bulletin of Chemical Reaction Engineering & Catalysis, 19 (3), 2024, 374
X-ray diffractometry. The fatty acid methyl ester
(FAME)
represents
the
efficiency
and
effectiveness of biodiesel production. The free
fatty acid methyl ester was carried out by gas
chromatography-mass
spectrometry
with
standard carbon C17.
2.2 Characterization of Calcium Titanate
The solid products were characterized by
Fourier transform infrared spectroscopy (FTIR),
scanning electron microscopy (SEM), and X-ray

B = base from CaTiO3 under various alkali hydroxide
Scheme 1. Reaction
esterification reaction.

mechanism

of

trans-

diffractometry (XRD). FTIR: The infrared spectra
were measured on Perkin Elmer model Spectrum
RXI with KBr preparation. The spectra were
collected over the range of wavenumber 4,000-400
cm−1 with 16 scanning and resolution at 4 cm−1.
SEM: The morphology and aggregate of particles
were examined by JEOL model JEM-6335. XRD:
The structures of samples were identified by using
Cu-Kα radiation and XRD pattern on Philips
model X'Pert MPD.
2.3 Transesterification Reaction of Biodiesel
The 100 mL of palm oil was mixed with 25 mL
of methanol in a round bottom bottle with reflux
apparatus for a transesterification reaction
(Scheme 1). The 1.5 g of calcium titanate was
added and heated to the mixture at 60-70 °C for 3
h. The mixture was poured into the separating
funnel and let stand until the separation appeared
then the mixture was filtrated. The warm water
was added to the oil fraction in a ratio of 1:1
volume by volume and was stirred for 30 min.
The methyl ester in biodiesel was determined
by gas chromatography (Agilent model 7890A)
with HP-5 MS 0.25 mm × 30 m × 0.25 µm. The
carrier gas was helium. The inlet temperature
was 230 °C with column flow was 1.5 mL/min. The
injector type was splitless and injection volume
was 1.0 µL. The split ratio was 50:1. The standard
of fatty acid methyl ester was used C17 (Sigma

Figure 1. FTIR spectra of products synthesized in the condition of 7 M (a) LiOH, NaOH, and KOH at 180
°C for 18 h and (b) LiOH, NaOH and KOH at 180 °C for 24 h.
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Bulletin of Chemical Reaction Engineering & Catalysis, 19 (3), 2024, 375
Aldrich). The viscosity at 40 °C was measured by
capillary (Cannon) with a constant equal to 0.958
cSt/s.
The yield of biodiesel from palm oil was
determined by Equation (1) [22,23].

Yield of biodiesel =

weight of biodiesel
 100 (1)
weight of palm oil

The percentage of fatty acid methyl ester was
calculated in Equation (2) [24].

C=

(  A ) − A  C  V  100%
EI

AEI

EI

EI

m

(2)

Where, C is %FAME, A is area peak of C16-C24,
AEI is area peak of C17 methyl ester, CEI is area
peak of C17 methyl ester(mg/mL), VEI is volume of
C17 methyl ester, and m is weight of biodiesel
(mg).
3. Results and Discussion
3.1. Characterizations of CaTiO3
The vibration of the metal-ligand mode was
studied using Fourier transform infrared
spectroscopy (FTIR). Figure 1(a) depicts the FTIR
spectra results of the 7 M alkali hydroxide

a

a

1µm

b

b

1µm

c

c

1µm

Figure 2. The product morphology was
synthesized in (a) 7 M LiOH (b) 7 M NaOH and (c)
7 M KOH at 180 °C for 18 h and schematics of
morphology shapes from (a1) 7 M LiOH (b1) 7 M
NaOH and (c1) KOH.

solutions at 180 °C for 18 h. The vibrations of the
Ti−O bond and Ca−O−Ti were not clear due to
broad bands. To enable a more detailed and
focused observation of the magnified spectral
data, we will specifically direct our attention to
the
Ti−O
vibrational
band
region
at
approximately 442 cm−1, as illustrated in Figure
1(b). In this detailed spectral analysis, we note
that the Ti−O vibrational mode of the CaTiO3
sample, which was synthesized using the 18 h
hydrothermal method, is characterized by a broad
peak. This broad peak is indicative of the presence
of excess moisture contamination, which is further
corroborated by the observation of an additional
prominent peak located around 3500 cm−1. This
peak at 3500 cm−1 can be attributed to the
vibrational modes associated with water
molecules, reflecting the residual moisture in the
sample and highlighting the need for meticulous
control of experimental conditions to mitigate
such contamination effects.
In Figure 1(c), when the heating time was
extended to 24 h, the Ti−O stretching band
occurred at 454 and 444 cm−1 in 7 M NaOH and
KOH, respectively. The bands at 556 and 551 cm−1
were assigned to the Ti−O−Ti bridge stretching in
7 M LiOH and NaOH, respectively. Additionally,
bands at 1635 and 1636 cm−1 were attributed to
O−H bands in hydroxyls and water surfaces on the
CaTiO3 [25]. All conditions exhibited a band at
1385 cm−1, assigned to N−O stretching of HNO3
[26], which was used as the solution to dissolve
CaCO3 and TiO2, the starting materials. The
stretching and bending of the Ca−O−Ti bond in
calcium titanate appeared under 7 M KOH at 564
cm−1 [27]. To gain a deeper understanding of the
effects of hydrothermal treatment time on the
vibrational characteristics of the synthesized
materials, a detailed analysis of the magnified
FTIR spectra will be conducted. Specifically
focusing on the vibrational range from 900 to 400
cm−1 as shown in Figure 1(d). Within this spectral
range, we will examine the intensity and
characteristics of the vibrational modes associated
with the Ca−Ti−O and Ti−O bonds. Notably, for
samples treated with KOH as the base during the
24 h hydrothermal process, we observe the
presence of strong and distinct absorption bands
at 554 cm−1 and 442 cm−1, which are indicative of
the characteristic vibrational modes of Ca−Ti−O.
In contrast, when using LiOH and NaOH as the
base under identical hydrothermal conditions, the
spectra reveal broad and overlapping bands
corresponding to two different types of vibrational
modes. This observation suggests that KOH is
particularly effective in promoting the formation
of CaTiO3 during a 24 h hydrothermal treatment,
whereas LiOH and NaOH do not achieve the same
degree of specificity in generating these
vibrational features, highlighting KOH superior

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Bulletin of Chemical Reaction Engineering & Catalysis, 19 (3), 2024, 376
role in inducing the formation of CaTiO3 under the
studied conditions.
The morphology study, conducted using
scanning electron microscopy (SEM), depicted the

a

a

1µm

b

b

1µm

c

c

1µm

Figure 3. The product morphology was
synthesized in (a) 7 M LiOH (b) 7 M NaOH and (c)
7 M KOH at 180 °C for 24 h and schematics of
morphology shapes from (a1) 7 M LiOH (b1) 7 M
NaOH and (c1) KOH.

products synthesized under 7 M alkali hydroxide
at 180 °C for 18 h. In Figure 2(a), rectangular bars
with various sizes and crystal shapes are
observed, while the corresponding schematic is
shown in Figure 2(a1). Figure 3(b) exhibits a
coherent shape, resembling a mixture of spherical
and rectangular structures, with the morphology
scheme represented in Figure 2(b1). In Figure 3(c),
the products are predominantly grouped in a
round shape with a cube-like appearance.
Furthermore, to gain a deeper understanding of
the morphology of all samples, the morphology
graphics are depicted in Figure 2(c1).
Similarly, the morphological analysis of the
products synthesized for 24 h, as depicted in
Figure 3(a), reveals the formation of a mixture
resembling a long rectangular shape, contrasting
with the observations from the previous synthesis
period, as illustrated further in Figure 3(a 1).
However, in Figure 3(b), a notable change in
shape is observed, resembling a cubic box mixed
with rectangular bars, as depicted more clearly in
the scheme represented in Figure 3(b1). Figure
3(c) shows a product with an unchanged shape,
yet exhibiting clearer particle edges and corners,
as clearly presented in Figure 3(c1). The results
from the SEM suggest that the synthesized
product was calcium titanate, consistent with the
findings of Li et al. [27] and Ernawati et al. [9].
The morphology of all products exhibits various
shapes and sizes, influenced by different alkali
hydroxides and synthesis times. Specifically, the
morphology observed in the synthesized product

Figure 4. The plot of pH of alkali hydroxide and morphology size from hydrothermal synthesize (a) 18 h,
(b) 24 h and (c) the relationship of the atomics size of alkali hydroxide and reactivity of the catalyst.
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Bulletin of Chemical Reaction Engineering & Catalysis, 19 (3), 2024, 377
after 24 h of synthesis represents a distinct
morphology reminiscent of clear single crystals.
This observation corresponds with the FTIR
results shown in Figure 1, which indicate strong
vibrational modes of Ca−Ti−O in the synthesized
products.

To better understand how the type of alkali
hydroxide used, and the duration of the
hydrothermal process affect the size and
morphology of the CaTiO3 crystals, the data is
presented in Figures 4(a) and 4(b). Figure 4(a)
shows a graph that plots the pH of various alkali

Figure 5. The XRD diffraction of calcium titanate in 7 M from (a) LiOH, (b) NaOH and (c) KOH.
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Bulletin of Chemical Reaction Engineering & Catalysis, 19 (3), 2024, 378
hydroxide solutions against the morphology size of
CaTiO3 crystals synthesized under hydrothermal
conditions for 24 h. The data from this plot
demonstrates that an increase in pH correlates
with a decrease in the morphology size of the
CaTiO3. Additionally, the results indicate that, for
the 24 h hydrothermal synthesis, the crystal size
of the CaTiO3 product synthesized using LiOH is
notably larger compared to those produced with
NaOH and KOH about 1.2, 0.9 and 0.8 µm,
respectively. This difference is attributed to the
presence of moisture and residue during crystal
formation, which affects the final morphology of
the CaTiO3 product.
In Figure 4(b), the morphology size of CaTiO3
observed at 18 h of hydrothermal treatment shows
a trend similar trend to that seen at 24 h, but with
a notable increase in the size of the crystals and
not closer alignment of sizes across different alkali
hydroxides. This observation suggests that
extending the hydrothermal treatment time
allows for continued crystal growth, resulting in
larger crystals and reducing the variability in size
among samples synthesized with different alkali
hydroxides. This size enhancement can be
attributed to the combined effects of increased pH
values and prolonged hydrothermal treatment
time, which together promote more effective
crystallization processes. As a result, the average
crystal sizes are 2.3 µm for LiOH, 0.8 µm for
NaOH, and 0.7 µm for KOH, reflecting how
different alkali hydroxides influence the final
crystal size under these conditions.
The effects of different types of alkali
hydroxides on the size of the CaTiO3 crystals can
be attributed to variations in atomic size and pH
values. A high pH value facilitates the formation
of metal ions and hydroxide anions more quickly,
which in turn affects the crystallization process.
Additionally, the rates at which different alkali
hydroxides ionize are influenced by the atomic
sizes of Li, Na, and K. Alkali hydroxides with
larger atomic radii, such as KOH, can lose
electrons from their valence shell more easily,
which enhances their catalytic performance. This
phenomenon is illustrated in Figure 4(c), where
the varying effectiveness of different alkali
hydroxides as catalysts is shown to correlate with
their atomic radii and ionization rates [28].
From the XRD pattern of calcium titanate at
7 M concentration of LiOH it is found that the
hydrothermal process at 24 h will give a higher
purity phase CaTiO3 product than at 18 h as
shown in Figure 5(a). However, when the 2θ range
is increased to 25°-30° in Figure 5(b), a diffraction
peak corresponding to the by-product phase
CaTi2O4(OH)2 at 27.05° is observed in samples
from both 18 h and 24 h. This observation
indicates that LiOH is not suitable for the
effective growth formation of CaTiO3. The same as

calcium titanate synthesized from NaOH at the
hydrothermal process at 24 h will give the CaTiO3
phase with higher purity than the 18 h found
phase of CaTi2O4(OH)2 as shown in Figure 5(c).
But in the case of the KOH based substrate in
Figure. Figure 5(d) shows that in the 2θ range of
25°-30°, the diffraction pattern reveals the
presence of the by-product phase CaTi2O4(OH)2 at
18 h of hydrothermal treatment, which is absent
by 24 h. This observation indicates that the byproduct phase forms during the initial stages of
the synthesis but is no longer present at the
extended hydrothermal time, possibly due to the
continued reaction or transformation processes.
In Figure 5(d), it is found that regardless of
the hydrothermal process at 18 or 24 h, only one
phase of CaTiO3 is found. In the 2θ range of 25°30°, as shown in Figure 5(d), the diffraction
pattern does not exhibit the presence of the byproduct phase CaTi2O4(OH)2 at either 18 h or 24 h
of hydrothermal treatment. Due to KOH is strong
base is better than LiOH and NaOH which makes
it easier to react and is better than other bases.
From the XRD results, it is evident that
increasing the hydrothermal synthesis time leads
to higher purity in the product. Furthermore, the
XRD results are complemented by SEM in Figure
3(a1, b1, c1) observations, indicating an increase in
the presence of single crystals of CaTiO3.
When considering the heating time required
for the hydrothermal process it is observed that as
the reaction duration increases the resulting
product exhibits higher purity. The crystallinity
approaching the nanoscale directly influences the
functionality of the catalyst. Based on the results
obtained from FTIR, SEM, and XRD analyses, the
CaTiO3 synthesized under 7 M alkali hydroxide
with heating times of 18 and 24 h continued to be
utilized as biodiesel catalysts.
3.2 Transesterification Reaction by CaTiO3 as
Biodiesel Catalysts
The biodiesel product was prepared through a
transesterification reaction utilizing palm oil
heated at 65-70 °C for 3 h. CaTiO3 synthesized via
the hydrothermal method for 18 and 24 h under 7
M concentrations of LiOH, NaOH, and KOH was
employed as the biodiesel catalyst. The methyl
ester of biodiesel was characterized by FTIR. In
Figure 6(a), FTIR spectrum was shown the band
at 1743 cm−1 assigned to the C=O stretch of the
ester is observed in both palm oil and biodiesel
produced using KOH as a catalyst. In the 1500100 cm−1 range in Figure 6(b) shows that the FTIR
spectra reveal the −CH3 bending vibrations at
1461 cm−1 and 1377 cm−1, C−O stretching
vibrations at 1377 cm−1 and 1117 cm−1, and a
broad peak at 1243 cm−1 for the O−CH3 group
across all palm oil and biodiesel samples.

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Bulletin of Chemical Reaction Engineering & Catalysis, 19 (3), 2024, 379

-CH3

1016

1117
1092

1243

1165

1377

1437

1461

Intensity (a.u.)

725

584

1461

1165

725

1650
1471
1437
1362
1243
1165
1472
1378

1016
882

1743
1743

2671
2853
2671

3008
3008

2853

3471

b

Plam oil
Biodiesel from KOH

Plam oil
Biodiesel from KOH

3471

Intensity (a.u.)

a

both LiOH and KOH show a band for −CH3.
However, the biodiesel product from CaTiO3
under KOH also displays additional peaks at 1377
cm−1 and 1118 cm−1 corresponding to C−O
stretching vibrations. This indicates that the
biodiesel produced from CaTiO3 under KOH has a
more complex structure compared to those
produced with LiOH and NaOH. Overall, the

1377
1362

Figure 6(c) shows the FTIR spectra of
biodiesel produced from CaTiO3 under 18 h of
hydrothermal treatment. The spectrum reveals
that the catalysts LiOH and NaOH primarily
exhibit a broad peak and only a characteristic
peak for −CH3 at 1462 cm−1. When the vibrational
range is magnified to 1500-100 cm−1 in Figure
6(d), it is evident that the biodiesel products from

O‒CH3

C‒O

C‒O

-CH3

3000

2500

c

2000

1000

500 1500

1400

1300

Wavenumber (cm-1)

1100

1000

d

LiOH 18 hours
NaOH 18 hours
KOH 18 hours

C‒O

C‒O

1462

1377

-CH3

2500

e

2000

1462

724

1000

500 1500

1400

1300

1200

1100

2500

2000

1000

f
O‒CH3

C‒O

C‒O C‒O
1117

1170
1170

1117

1197

1270

1197

1270

1362
1362

1466

1435

1466

C=O

1435

Intensity (a.u.)

720
720

‒CH2
-CH‒3

500 1500

Wavenumber (cm-1)

1400

1300

1200

1117

1170

1466

1270

720

847
847

1015

1170
1170
1170

1500

1015

1470
1437
1249
1470
1437
1249

1746
1746

3000
2926
2858

3000

1437
1249

3000
2926
2858
3000
2926
2858

Intensity (a.u.)

3500

1000

Wavenumber (cm-1)
LiOH 18 hours
NaOH 18 hours
KOH 18 hours

LiOH 18 hours
NaOH 18 hours
KOH 18 hours

4000

1500

Wavenumber (cm-1)

1015

3000

1015

3500

1746

4000

1438
1377

1746

1462

Intensity (a.u.)

724

1438
1377

724

LiOH 18 hours
NaOH 18 hours
KOH 18 hours

1746

1200

Wavenumber (cm-1)

1164

1746

3010
2928
2854

Intensity (a.u.)

1500

1118
1164

3500

1438
1377

4000

1100

1000

Wavenumber (cm-1)

Figure 6. The FTIR spectrum of (a) palm oil and biodiesel by using KOH as catalyst, (b) oil products using
CaTiO3 catalysts under 7 M of alkali hydroxide at 18 h and (c) oil products using CaTiO 3 catalysts under 7
M of alkali hydroxide at 24 h.
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Bulletin of Chemical Reaction Engineering & Catalysis, 19 (3), 2024, 380
performance of the catalysts for transforming
palm oil to methyl ester is relatively low for the 18
h hydrothermal synthesis process.
Figure 6(e) shows the FTIR spectra of
biodiesel produced from the catalyst under 24 h of
hydrothermal synthesis. Compared to the 18 h
synthesis, the 24 h spectra exhibit more distinct
characteristic peaks, indicating a richer profile of
the biodiesel product. However, upon closer
examination, it is observed that the spectrum of
biodiesel from the CaTiO3 under LiOH catalyst
shows a broader peak compared to the spectra
from CaTiO3 under NaOH and KOH. This
indicates that the biodiesel from CaTiO3 under
LiOH has a more complex structure or different
molecular interactions. When the spectra are
magnified in the 1500-1000 cm−1 range, as shown
in Figure 6(f), the characteristic features of the
biodiesel production become more apparent and
allow for a clearer comparison of the effects of
different catalysts.
The FTIR spectra of biodiesel from the
catalyst under LiOH conditions after 24 h of
hydrothermal synthesis show distinct vibrational
peaks at 1466 cm−1 for −CH3, 1170 cm−1 and 1117
cm−1 for C−O, and 1270 cm−1 for O−CH3. In
contrast, the biodiesel products from catalysts
under NaOH and KOH conditions exhibit
additional vibrational features including a peak at
1466 cm−1 for −CH3, 1435 cm−1 for −CH2, 1362
cm−1, 1170 cm−1, and 1117 cm−1 for C−O, 1197 cm−1
for C=O, and 1270 cm−1 for O−CH3. The presence
of these additional peaks in the FTIR spectra
indicates that the biodiesel produced using NaOH
and KOH catalysts has a more complex
composition compared to that produced with
LiOH. Furthermore, the comparison of these
spectra with those from the 18-h hydrothermal
synthesis process demonstrates that the 24 h
synthesis generally results in higher catalyst
performance for the production of biodiesel, as
evidenced by the more diverse range of vibrational
modes observed in the spectra.
Table 1 presents the physical and chemical
properties of the biodiesel products obtained using
CaTiO3 as a catalyst under various conditions.

Specifically, the biodiesel yield using CaTiO3 with
a 7 M LiOH solution was approximately 87% for
an 18 h reaction time and 95% for a 24 h reaction
time. Despite these high yield percentages, the
GC-MS data failed to detect any %FAME which
indicates that the CaTiO3 catalyst under LiOH
conditions
was
not
effective
for
the
transesterification reaction and viscosity are
34.67 cSt and 34.98 cSt. This suggests that while
the reaction conditions resulted in a high volume
of biodiesel, the quality or composition of the
biodiesel did not meet the criteria for successful
transesterification as determined by GC-MS
analysis.
The results for the NaOH-catalyzed biodiesel
production under 18 h and 24 h are shown as
follows the percentage of biodiesel yield was 70%
for 18 h and 78% for 24 h, with corresponding
viscosities of 34.98 cSt and 5.14 cSt, respectively.
Although the %FAME was not detected at 18 h, it
was found to be 63.67% at 24 h. These results
suggest that the longer reaction time improves the
%FAME content in the biodiesel. In comparison,
the high viscosity observed for the biodiesel
produced using CaTiO3 under both LiOH and
NaOH
conditions
indicates
that
the
transesterification reaction was not successful for
biodiesel production, as evidenced by the
inadequate %FAME formation and the high
viscosity of the final product.
Under hydrothermal conditions, the KOHcatalyst demonstrated biodiesel yields of 90%
after 18 h and 93% after 24 h. While %FAME
could not be detected in the biodiesel produced
after 18 h, the 24 h reaction resulted in a high
%FAME content of 90.02%. It corresponds with
viscosities of 32.61 cSt and 4.98 cSt for the 18 h
and 24 h reactions, respectively. This significant
increase in %FAME and the low viscosity of the
biodiesel product after 24 h highlight the
effectiveness of CaTiO3 as a catalyst for the
transesterification reaction when used under
optimal hydrothermal conditions. Thus, the
results indicate that CaTiO3 under these
conditions is a suitable and efficient catalyst for
biodiesel production.

Table 1. The viscosity, the yield of biodiesel and % fatty acid methyl ester (FAME) of oil product by CaTiO 3
as biodiesel catalyst.
CaTiO3 under 7 M of
alkali hydroxide

Heating time of
hydrothermal method (h)

The yield of
biodiesel (%)

Viscosity of
biodiesel (cSt)

% FAME

LiOH
NaOH
KOH
LiOH
NaOH
KOH

18
18
18
24
24
24

87
70
90
95
78
93

34.67
34.98
32.61
33.97
5.14
4.98

63.67
90.02

Copyright © 2024, ISSN 1978-2993

Bulletin of Chemical Reaction Engineering & Catalysis, 19 (3), 2024, 381
The CaTiO3 catalyst proves to be an effective
catalyst for the transesterification reaction under
KOH conditions for 24 h. This effectiveness is
comparable to that of traditional strong bases
such as NaOH and KOH due to the high basicity
of KOH, which facilitates the transesterification
process. However, a significant advantage of using
CaTiO3 is its potential for reuse, which reduces
waste compared to traditional base catalysts.
The reaction steps and overall process for
using CaTiO3 as a catalyst are illustrated in
Figures 7(a) and 7(b), demonstrating both the
efficiency of the transesterification reaction and
the sustainability benefits of the CaTiO3 catalyst.
Table 2 presents a comparison of the catalytic
performance of CaTiO3 under KOH conditions for
24 h with that of other catalysts reported in
previous studies. This comparison demonstrates
that CaTiO3 exhibits high catalytic performance
for the transesterification reaction, showing
superior or comparable results to other catalysts
used for biodiesel production. This finding
highlights a significant new development for
CaTiO3 as an effective and innovative catalyst for
biodiesel synthesis under KOH conditions for 24
h, suggesting its potential for future applications
in biodiesel production.

4. Conclusions
In this study, we have demonstrated the
pivotal role of 7 M concentrations of NaOH and
KOH in achieving optimal synthesis conditions for
calcium titanate via the hydrothermal method at
180°C for 24 hours. The successful formation of
CaTiO3 was confirmed through rigorous analysis
using FTIR and XRD, referencing JCPDS No. 420423. SEM analysis further elucidated the
distinct cube-like morphology of calcium titanate,
suggesting its potential suitability for a wide
range of catalytic applications. Notably, our
investigation revealed a significant difference in
the percentage yields of fatty acid methyl ester
obtained using calcium titanate synthesized with
NaOH (63.67%) compared to KOH (90.02%),
underscoring the critical role of the alkali
hydroxide choice in
optimizing
catalyst
performance.
These findings contribute to the growing body
of knowledge on calcium titanate synthesis and its
application in biodiesel production. The ability to
tailor synthesis conditions to achieve desired
catalytic properties opens avenues for further
research into optimizing biodiesel production
processes. Future studies could explore the
underlying mechanisms influencing catalyst
performance and investigate additional synthesis
parameters to enhance catalytic activity and
selectivity.

a

b

Figure 7. (a) The percentage of FAME by CaTiO3 as biodiesel catalyst. (b) The flow diagram for biodiesel
production from palm oil by using CaTiO3 as a catalyst.
Table 2. Comparison of the percentage of FAME of other materials with previous reports.
Catalyst
Na2Ti3O7
K/TiHT
TS-0
*CaTiO3
*TNT
CaTiO3
*nano tube

Synthesize method
hydrothermal
hydrothermal
sol–gel
sol-gel-hydrothermal
hydrothermal
hydrothermal

% FAME
69.05
65.0
30.0
80.0
83.5
90.0

Type of reaction
transesterification
transesterification
transesterification
transesterification
transesterification
transesterification

Copyright © 2024, ISSN 1978-2993

Reference
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Bulletin of Chemical Reaction Engineering & Catalysis, 19 (3), 2024, 382
Overall, our results highlight the importance
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parameters in achieving efficient catalysts for
biodiesel
production.
By
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our
understanding of calcium titanate synthesis and
its catalytic properties, this study offers valuable
insights for the development of sustainable and
efficient processes in the biodiesel industry.

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Acknowledgment
The authors would like to thank the following
institution for its financial support: Faculty of
Science, Maejo University.
CRediT Author Statement
Conceptualization, writing-review, writingoriginal draft preparation, writing-editing,
visualization;
Ratchadaporn
Puntharod.;
methodology,
Kittikarnkorn
Onsomsuay.;
software, writing-review and editing, Jaturon
Kumchompoo.; conceptualization and formal
analysis, Pusit Pookmanee.
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Copyright © 2024, ISSN 1978-2993