OPEN ACCESS
Journal of Multidisciplinary Applied Natural Science Vol.
5 No.
https://doi.
org/10.
47352/jmans.
Research Article The Effect of MgO Loads on Catalytic Activity of MgO/SiO2 in Coconut Oil Transesterification Kamisah Delilawati Pandiangan.
Wasinton Simanjuntak*.
Ilim Ilim.
Diska Indah Alista, and Erika Noviana Received : October 15, 2024 Revised : December 11, 2024 Accepted : March 12, 2025 Online : April 24, 2025 Abstract This research aims to obtain biodiesel by transesterification of coconut oil with MgO/SiO 2 as a catalyst, with the objective to examine the effect of MgO loads on the performance of the catalysts expressed in terms of oil conversion.
The MgO/SiO 2 composites with different mass ratios of 1:1, 1:2, 1:3, 1:5, and 1:10 were synthesized from Mg(NO .
A6H2O and SiO2 extracted from rice husk silica using sol-gel method and followed by calcination at 800 AC for 6 h.
The produced catalysts were then tested in the transesterification of coconut oil to investigate the effect of catalyst composition, oil to methanol ratios, and reaction times.
The experiments were carried out using a fixed catalyst load of 10% oil .
and at 70 AC.
The catalyst with the highest performance was then characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) to confirm the formation of crystalline MgO/SiO2.
The highest conversion of the transesterification product was analyzed using gas chromatography-mass spectrometry (GC-MS) technique to confirm the biodiesel production.
The XRD diffractogram of the synthesized sample is characterized by the presence of sharp peaks confirming the existence of the sample as crystalline material attributed to the pyroxene-ideal (MgO3S.
The existence of the sample as crystalline material is also supported by the absence of a broad diffraction peak attributed to amorphous rice husk silica, and SEM image of the sample which is characterized by the visible existence of crystalline structure in the forms of platelet prismatic, and tetrahedral shaped structures.
The results demonstrated that the highest conversion .
%) was achieved with the use of MgO/SiO 2 .
as a catalyst, a ratio of oil to methanol of 1:6, and a reaction time of 4 h.
The formation of methyl esters was confirmed by the results of GC-MS analysis.
Keywords MgO/SiO2, sol-gel, catalyst, biodiesel, transesterification INTRODUCTION Research on renewable energy has attracted attention in response to the depletion of fossil fuels and environmental danger as a consequence of their Up to present, biodiesel is the most attractive renewable fuel and has been widely used in several countries in blended forms with petrochemical diesel with gradually increased percentages .
Biodiesel is an attractive renewable fuel compared with fossil diesel.
It has better combustion characteristics, lower viscosity, and higher cetane number .
In addition, biodiesel is nontoxic and biodegradable, therefore more environmentally friendly than fossil diesel.
Biodiesel is produced from various raw materials, either vegetable oils or animal fats, by reacting PublisherAos Note:
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them with simple alcohols, mostly methanol and With the use of methanol, for instance, the biodiesel produced is a mixture of fatty acid methylesters (FAME.
In biodiesel production, free fatty acids contained in the raw materials undergo an esterification reaction while the glycerides undergo However, since the composition of vegetable oils and animal fats is dominated by glycerides, transesterification is much more important than the esterification reaction.
The yield of biodiesel is acknowledged to depend on several factors, with the most influencing being catalyst, oil to alcohol ratio, and reaction time.
Although noncatalytic transesterification is being developed, such as the supercritical technique .
, catalytic transesterification is still the main choice, primarily because the process is simpler and faster than the first one.
The type of catalyst that has been applied since the beginning of the biodiesel industry is homogeneous catalyst, either strong acids such as H2SO4 .
HNO3 .
, and HCl .
or strong bases, primarily NaOH .
and KOH .
Homogenous catalysts are acknowledged to exhibit high performance leading to the production of biodiesel in high yield.
However, apart from this advantageous feature, the use of homogeneous catalyst is constrained by several shortcomings that J.
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Figure 1.
Oil conversions are achieved using catalysts with different compositions.
contribute to production costs.
Strong acids and bases are corrosive chemicals and as a consequence, the biodiesel must be washed with a considerable quantity of water to remove the catalyst, causing a problem to the environment where the wastewater is released.
In addition, reuse of homogeneous catalysts is practically impossible.
In response to the shortcomings of homogeneous catalysts, many works have been continuously devoted to the development of heterogeneous .
catalysts as alternatives.
As a solid, heterogeneous catalyst can be separated from biodiesel simply by filtration therefore no produced wastewater and the catalyst can be reused.
addition, heterogeneous catalyst is not corrosive.
recognition of the advantages they offered, many solids have been explored including, but not limited to, metal oxides .
, supported metal oxides .
and various zeolites .
Besides the type of catalyst, other factors transesterification are catalyst composition, oil to alcohol ratio, and reaction time .
With respect to the role of these factors, in this study transesterification of coconut oil with methanol for biodiesel production was investigated using MgO supported on rice husk silica (MgO/SiO.
with different compositions .
ass rati.
of 1:1, 1:2, 1:3, 1:5, and 1:10 as catalyst.
A number of experiments were conducted to evaluate the effect of catalyst compositions, oil to alcohol ratios, and reaction time on the reaction yield.
The synthesis and application of MgO/SiO2 composites with a considerably wide range of compositions explored in this research provides an opportunity to gain more detailed insight into the role of composition in determining the performance of the synthesized MgO/SiO2 catalyst, is a new approach which has not been extensively explored in detail in previous To ensure whether the MgO/SiO2 composite has been successfully formed as expected, the catalyst with the highest performance was then characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM).
Table 1.
Several examples of composite catalysts and their compositions used in biodiesel production.
No.
Catalyst Mass ratio Raw material Reference TiO2/SiO2 Waste cooking oil CaO/SiO2 Coconut oil ZnO/-zeolite Waste cooking oil MgO/SiO2 Rubber seed oil Li/NaY zeolite Castor oil Multidiscip.
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Figure 2.
The experimental results demonstrating the effect of oil to methanol ratios on oil conversion.
MATERIALS AND METHODS
Materials Rice husk (RH) was obtained from a local source .
ice milling company in Natar.
South Lampun.
, coconut oil was purchased from local market in Bandar Lampung, analytical grade nitric acid (HNO.
, sodium hydroxide (NaOH), magnesium (Mg(NO.
A6H2O), methanol (CH3OH) were purchased from Merck.
Methods Extraction of RH Silica Alkaline extraction using 1.
5% NaOH solution was applied to obtain rice husk silica.
The typical experiment was run by boiling the mixture of 50 g of husk and 600 mL of NaOH solution for 30 min and then left overnight at room temperature.
The mixture was then subjected to filtration to collect the filtrate containing silica .
ilica so.
The sol was slowly neutralized using 10% HNO3 until silica gel was formed and allowed to stand for 24 h for aging The silica gel was washed with warm water to remove organics that dissolved during the extraction step.
The gel was oven-dried at 110 AC for 24 h to obtain solid silica.
Finally, the silica was ground into powder and sieved using a 200 mesh sieve to obtain silica powder.
Catalyst Preparation and Characterization In this work, five MgO/SiO2 samples with the MgO to SiO2 mass ratio of 1:1.
1:2.
1:3.
1:5, and 1:10 were prepared using sol-gel process adopting the method described in Pandiangan et al.
The first step was the preparation of raw materials, by dissolving the silica in a 1.
5% NaOH solution .
olution A), and Mg(NO.
A6H2O in distilled water .
olution B).
Both solutions were then mixed slowly under stirring to ensure the homogeneity of the mixture, followed by acidification of the mixture using 10% HNO3 until the gel was formed.
The gel formed was then filtered and dried in an oven at 110 AC for 24 h.
The dry MgO/SiO2 samples were ground into powder and then calcined at 800 AC for 6 h.
Table 2.
The effect of oil to methanol ratio on conversion of different vegetable oils into biodiesel.
No.
Vegetable oil
Oil to methanol ratio
Oil conversion (%) Reference Sunflower oil
Waste cooking oil
1:15
Rubber seed oil
1:12
Ricinus communis oil Castor oil Multidiscip.
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Figure 3.
The experimental results show the effect of reaction time on oil conversion.
Catalyst characterization was carried out using the XRD technique on Empyrean-type PANalytical equipment, scanning the sample over a 2 angle in the range of 5Oe50A with a counting time of 8 s/step.
The CarlZeiss/Evo MA 10 type apparatus was used for SEM analysis.
Characterization of the sample was limited to these two techniques because the main purpose is to obtain information regarding the structure and microstructure of the sample since these two properties have been acknowledged to play the most important role in governing the performance of a catalyst.
However, the contribution of other physical characteristics including surface area, surface chemical composition, and basicity, should also be In this respect, these characteristics should be tajen into account in the future works.
Transesterification Reaction Transesterification was carried out in a transesterification reactor consisting of a 500 mL round bottom flask equipped with a reflux condenser, immersed in a water bath placed on a hotplate magnetic stirrer.
The first series of experiments were conducted to study the effect of catalyst compositions as a way to select the catalyst with the highest performance to be used for the rest of the experiments aimed to investigate the effect of raw material composition .
il to methanol ratio.
and reaction time.
The experiment was carried out at 70 AC for 4 h using 25 mL of coconut oil, 100 mL of methanol, and 2.
5 g of catalyst.
After the completion of the reaction, the sample was allowed to cool to room temperature and then filtered into a separatory funnel, to separate the catalyst.
The sample in the separatory funnel was allowed to settle for 24 h to separate the biodiesel .
pper laye.
from the unreacted oil, and then the biodiesel was The excess of methanol was removed by evaporation and the biodiesel volume was used to calculate the oil conversion, using the following equation 1 .
, where.
V1 is initial volume of oil Figure 4.
Chromatogram of biodiesel obtained using MgO/SiO2 1:5 as a catalyst.
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Table 3.
The components of the transesterification product of coconut oil with methanol.
Peak Retention time .
Molecular Formula Compound Name Relative Percentage (%) C7H14O2 Methyl caproate C9H18O2 Methyl caprylate C11H22O2 Methyl caprate C13H26O2 Methyl laurate C15H30O2 Methyl myristate C17H34O2 Methyl palmitate C19H34O2 Methyl linoleate C19H36O2 Methyl elaidate C19H38O2 Methyl stearate and V2 is the volume of unreacted oil.
Oil converison = V1 Oe V2 x 100% .
The reaction yields obtained with the application of MgO/SiO2 with different compositions were used to choose the best catalyst for the next experiments.
To determine the optimum oil to methanol ratio, experiments were carried out with the ratio of 1:2.
1:3.
1:4.
1:5, and 1:6 for 4 h.
The optimum ratio obtained from these experiments was then applied for the determination of optimum reaction time, in which the experiments at reaction time of 2, 3, 4, 5, and 6 h were run.
The transesterification product obtained from the experiment involving the optimum factors investigated was then analyzed using gas chromatography-mass spectrophotometry (GC-MS) type GM-MS QP-2010S Shimadzu.
The NIST12 Library System Software was used to identify the components of the product.
RESULTS AND DISCUSSIONS
Effect of Catalyst Composition on Oil Conversion As previously mentioned, the MgO/SiO2 with the MgO to SiO2 mass ratio of 1:1.
1:2.
1:3.
1:5,
and 1:10 were prepared and then tested as catalyst for coconut oil transesterification.
The five experiments were run at a fixed oil to methanol ratio of 1:4 and fixed reaction time of 4 h.
The experimental results are compiled in Figure 1.
was found that with the use of a catalyst with a MgO to SiO2 mass ratio of 1:10, practically no oil conversion was achieved.
As displayed by the experimental results in Figure 1, the effect of catalyst compositions on oil conversion is evident in which increased conversions to reach the optimum value of 96% were observed following the change in composition from 1:1 up to 1:5.
These results outline that the MgO to SiO2 ratio of 1:5 is an ideal composition reflecting that the number of MgO molecules as active sites and SiO2 molecules reaction host function synergistically to optimize the oil In the case of the catalyst with the MgO to SiO2 ratio of 1:10, it is most likely that the excessive numbers of SiO2 particles covered the MgO particles, preventing them from effective interaction with the oil molecules.
With respect to the results obtained, the catalyst with MgO to SiO2 ratio of 1:5 was then selected for the rest of the The use of composite catalysts with varied compositions has also been reported in several previous works.
Some examples are shown in Table 1.
Effect of Oil to Methanol Ratios on Oil Conversion The experimental data produced from the experiments with different ratios of oil to methanol as compiled in Figure 2 display quite significant increases in oil conversion following the ratio from 1:2 up to 1:4 but for the last two ratios no significant change was observed.
Concerning these results, the ratio of 1:4 was then considered as the J.
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Figure 5.
Diffractogram of MgO/SiO2 with the ratio of 1:5 and calcined at 800 AC and identified phases.
optimum ratio, with an oil conversion of 98% was In biodiesel production by transesterification, the ratio of oil to methanol is acknowledged as a prominent variable and therefore has been extensively investigated by many workers, showing that the composition of reactants to some extent depends on the types of the feedstocks treated.
The results of previous investigations presented in Table 2 illustrate effect of feedstock composition .
il to methanol rati.
on conversion of several vegetable Some examples of work conducted to investigate the effect of feedstock composition .
il to methanol rati.
on oil conversion are shown in Table 2.
Determination of the Optimum Reaction Time Another factor that has been acknowledged to play very significant role in transesterification of vegetable oils is reaction time.
In appreciation of this variable, the experiments at different durations of time were conducted and the results produced are presented in Figure 3.
The experimental results presented in Figure 3 were obtained from the experiments conducted using the MgO/SiO2 with MgO to SiO2 ratio of 1:5 as a catalyst and at fixed oil to methanol ratio of 1:4.
The results in Figure 3 indicate significant increases in oil conversion achieved from the experiments at 2-h, reaching the optimum value of 98% at 4-h reaction time.
It is also observed that by elongation of reaction time to Figure 6.
Micrographs of the MgO/SiO2 1:5 catalysts at different magnifications: .
1,000y.
5,000y.
10,000y.
15,000y.
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5 and 6 h led to slight decreases in oil conversion, implying that 4 h is the optimum time.
The effect of reaction time on transesterification reaction has also been investigated by other workers .
, showing the existence of variation in optimum reaction time, depending on the feedstock treated, and other reaction variables implemented.
GC-MS Analysis of Transesterification Product To identify the components contained in the transesterification product, the sample was analyzed by GC-MS, and the chromatogram is presented in Figure 4.
Figure 4 indicates that there are nine compounds composing the biodiesel, as listed in Table 3, confirming that the fatty acids contained in the oil have reacted with methanol to produce a mixture of methyl esters.
The main component obtained is methyl laurate which is derived from lauric acid according to the fatty acids the main content in coconut oil .
Characterization of Selected Catalyst The catalyst with the highest activity .
elected catalys.
was then characterized by XRD and SEM The XRD diffractogram of the sample is shown in Figure 5.
The wide band in Figure 5 .
theta = 20Oe30A) is due to the presence of amorphous silica .
and the sharp peaks indicate that a crystalline phase has been formed in the sample.
The XRD pattern was then analyzed using Match Program (Phase Identification from Powder Diffraction Ae Version .
to identify.
With the aid of this phase identification software, it was found that the sample has the molecular formula of MgOSiO2 with pyroxeneideal as the main phase.
The existence of this crystalline phase is affirmed by the peaks at diffraction angles of 2 = 32.
4A, 35.
7A, 36.
5A, and 7A, which are attributed to crystalline MgO.
The XRD results obtained in this study are in agreement with that reported by previous works .
Successful formation of MgOSiO2 is also confirmed by the absence of wide diffraction band in the 2 region of 20Oe30A, which is the characteristic XRD feature of amorphous silica.
The surface morphology of this particular catalyst was analyzed by SEM and the micrographs with different magnifications are presented in Figure 6.
The surface morphology of the MgO/SiO2 1:5 catalysts in Figure 6 shows the presence of particles with a prismatic or tetrahedral form, aggregates, or fibrous collections of thin plates.
the surface, scattered cavities originating from silica were detected.
The surface morphology of the MgO/SiO2 catalyst is more clearly visible under higher magnifications.
As can be observed, in the image with 1,000y magnification, the crystalline phase is not yet clearly visible.
The presence of particles as prismatic or tetrahedral forms, aggregates, or fibrous collections of thin plates can be observed in the image produced with 15,000y CONCLUSIONS The MgO/SiO2 catalyst has been successfully synthesized by a sol-gel technique by varying the MgO to SiO2 mass ratio of 1:1.
1:2.
1:3.
1:5.
1:10.
Thermal treatment by calcination at a temperature of 800 AC for 6 h was found to produce MgO/SiO2, with the main phase being the pyroxene -ideal and amorphous silica phase according to XRD characterization.
The transesterification experiments reveal the significant effect of the ratio of oil to methanol and reaction time on the conversion of the oil into biodiesel.
The highest conversion .
%) was achieved using MgO/SiO2 1:5 as a catalyst with an oil to methanol ratio of 1:4, and reaction time of 4 h.
The formation of biodiesel was confirmed using GC-MS analysis.
AUTHOR INFORMATION
Corresponding Author Wasinton Simanjuntak Ai Department of Chemistry.
Lampung University.
Bandar Lampung-35144 (Indonesi.
org/0000-0001-8152-5084 Email: wasinton.
simanjuntak@fmipa.
Authors Kamisah Delilawati Pandiangan Ai Department of Chemistry.
Lampung University.
Bandar Lampung-35144 (Indonesi.
org/0000-0001-6347-2361 Ilim Ilim Ai Department of Chemistry.
Lampung University.
Bandar Lampung-35144 J.
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(Indonesi.
org/0000-0002-7382-6765 Diska Indah Alista Ai Department of Chemistry.
Lampung University.
Bandar Lampung-35144 (Indonesi.
org/0009-0002-1365-9704 Erika Noviana Ai Department of Chemistry.
Lampung University.
Bandar Lampung-35144 (Indonesi.
org/0009-0008-4876-5033 Author Contributions Conceptualization and Methodology.
and I.
Formal Analysis and Resources.
, and W.
Investigation.
and E.
Data Curation.
and K.
Writing Ae Original Draft Preparation.
and D.
Writing Ae Review & Editing.
and I.
Visualization.
Project Administration.
Conflicts of Interest
The authors declare no conflict of interest
ACKNOWLEDGEMENT
The author would like to thank the University of Lampung, for financial support through the Merdeka Belajar Kampus Merdeka research grant with contract number of 880/UN26.
21/PN/2023.
REFERENCES