jurnal eta kimia e-ISSN: 2807-7938 .
dan p-ISSN: 2807-7962 .
Volume 6.
Number 1.
May 2026 http://ejurnal.
id/index.
php/jbk Study of the Crystal Structure of CaO/SiOCC.
MgO/SiOCC, and CaOAe MgO/SiOCC Catalysts Andreas Venans Nahak1*.
Kasimir Sarifudin2.
Lolita A.
Parera3 Department of Chemistry Education.
Faculty of Teacher Training and Education.
Universitas Nusa Cendana *e-mail correspondence: andreasvenansnahak@gmail.
ARTICLE INFO
Article history:
Received:
31 March 2026 Revised:
10 May 2026 Accepted:
16 May 2026 Keywords:
CaO.
MgO.
SiOCC.
XRD, crystal structure, catalyst License:
Attribution-Share Alike 4.
International (CC-BY-SA 4.
ABSTRACT
This study aims to analyze the crystal structure characteristics and phase composition of the CaO/SiO2.
MgO/SiO2, and CaO-MgO/SiO2 catalysts, and to synthesize SiO2 from Ende Flores Natural Zeolite using the hydrothermal and solgel methods.
CaO was synthesized from Kupang NTT hard water lime deposits, refluxed with HCl, and titrated with Na2CO3, then calcined at 1000 AC to obtain CaO.
MgO was synthesized from MgCO3 calcined at 800 AC.
The synthesis of each type of catalyst.
CaO/SiO2.
MgO/SiO2, and CaO-MgO/SiO2, was carried out using the impregnation method.
The XRD characterization results show that, in SiO 2, the tridymite phase with a triclinic crystal structure is formed.
CaO forms the Lime phase with a cubic crystal structure, while the MgO catalyst shows the Periclase phase and also has a cubic crystal structure.
The CaO/SiO 2 catalyst forms a single phase, namely Larnite (Ca2SiO.
, with a monoclinic crystal structure.
The MgO/SiO2 catalyst formed three phases, namely the dominant Periclase phase (MgO) with a cubic crystal structure, the Olivine phase (Mg2SiO.
with an orthorhombic crystal structure, and the Tridymite phase (SiO.
with a cubic crystal The CaO-MgO/SiO2 catalyst forms two phases, namely the dominant phase Olivine (Mg2SiO.
with an orthorhombic crystal structure and the Portlandite phase (CaH2O.
with a trigonal crystal structure.
How to cite: Nahak.
Sarifudin.
Parera.
Study of the Crystal Structure of CaO/SiO2.
MgO/SiO2, and CaO-MgO/SiO2 Catalysts, 6.
, 96-109.
https://doi.
org/10.
35508/jbk.
INTRODUCTION
Catalysts play a crucial role in chemical reactions, as they are compounds capable of accelerating reaction rates without undergoing permanent chemical changes .
Catalysts function by providing active sites that can adsorb reactants and reduce activation energy, thereby enabling reactions to proceed more rapidly.
Due to their essential function, the application of catalysts has become a fundamental requirement in various industrial processes.
In general, catalysts are classified into two categories: homogeneous and heterogeneous catalysts.
Homogeneous catalysts offer the advantage of effective interaction with reactants.
however, they present significant challenges in product separation .
Consequently, heterogeneous catalysts have emerged as a more effective alternative because they can be easily separated from the reaction products and reused .
CaO and MgO-based catalysts are among the most widely developed heterogeneous basic catalysts due to their abundant availability, low cost, and relatively high catalytic activity.
CaO exhibits strong basicity, making it highly effective for transesterification reactions, whereas MgO demonstrates superior thermal stability despite having lower basic strength than CaO.
However, the direct application of CaO and MgO still faces a major limitation, namely the leaching of Ca Page | 96 Nahak et al: Study of the Crystal Structure of CaO/SiO2.
and MgAA ions from the solid phase into the liquid phase during the reaction process .
This phenomenon is caused by interactions between the catalyst and alcohols, such as methanol, which can partially dissolve the active phase.
As a result, the number of active sites decreases, catalyst deactivation occurs, and biodiesel yield is reduced .
Furthermore, leaching may transform the catalytic system into a semi-homogeneous system, thereby diminishing the inherent advantages of heterogeneous catalysts.
To address this limitation, one widely explored approach is the impregnation of catalysts onto supporting materials .
Silica (SiOCC) is one of the most commonly used supports because of its high thermal stability, large surface area, and porous structure, which enables uniform dispersion of the active phase.
In addition, the presence of silanol groups on the SiOCC surface facilitates interactions between the support and the catalyst, thereby strengthening metalAeoxide bonding and reducing the likelihood of leaching .
Thus, the role of SiOCC extends beyond merely serving as a physical support.
it also enhances the chemical stability and active-site distribution of the catalyst.
Although numerous studies have reported the application of CaO/SiOCC and MgO/SiOCC catalysts, comprehensive comparative studies involving these systems alongside the CaOAe MgO/SiOCC catalyst system remain limited.
Several studies have indicated that the combination of CaO and MgO may improve catalytic performance through a synergistic effect, integrating the high basicity of CaO with the thermal stability of MgO .
Moreover.
CaOAeMgO-based catalysts have been reported to exhibit superior catalytic activity compared with single-component catalysts due to interactions between the active phases that enhance reaction efficiency .
However, the relationships among crystal structure, phase distribution, and catalyst stability within this system remain insufficiently understood, highlighting the need for further Characterization of the crystal structure of catalysts is an important aspect in identifying crystalline phases, composition, and lattice parameters associated with the physical and chemical properties of catalysts.
This analysis is commonly conducted using X-ray diffraction (XRD) .
Through crystal structure characterization, the relationships among atomic arrangement, phase distribution, and crystallite size with catalytic activity and stability can be elucidated .
Such information is essential for optimizing catalyst performance, particularly in improving stability and minimizing leaching.
Therefore, this study aims to investigate the crystal structures of CaO/SiOCC.
MgO/SiOCC, and CaOAeMgO/SiOCC catalysts.
One of the objectives of this research is to provide insights into the crystal structural characteristics of these materials.
RESEARCH METHODS
Time and Location of the Study This study was conducted from February to June 2025 at the Chemistry Education Laboratory.
Faculty of Teacher Training and Education.
Universitas Nusa Cendana.
The characterization analysis using X-ray diffraction (XRD) was carried out at the Center for Minerals and Advanced Materials.
Universitas Negeri Malang.
Research Instruments and Materials The equipment used in this study included glassware, a thermometer, a 200-mesh sieve, a porcelain mortar, an oven, stainless steel plates, a desiccator, a reflux flask, an Ohaus balance, an oven column, a magnetic stirrer, filter paper, a digital balance (Denve.
, a water pump, a calcination and reduction reactor, an analytical balance, a Buchner funnel, a stopwatch, a pressure cooker, a smart mixer, a hot plate, aluminum foil, screw clamps, titration apparatus, and an X-ray Page | 97 Jurnal eta Kimia.
Vol.
May .
, page 96-109 :https://doi.
org/10.
35508/jbk.
diffraction (XRD) instrument.
The XRD instrument consisted of three main components: an Xray source, a sample holder/goniometer, and an XRD detector.
Experimental Design The diffractograms obtained from the XRD analysis were processed using Match! software version 4.
3 to examine the crystal structure of the catalyst materials.
The analysis included determining the crystal systems, lattice parameters, and phase composition of each catalyst material: CaO.
MgO.
CaO/SiOCC.
MgO/SiOCC, and CaOAeMgO/SiOCC.
Experimental Procedure Treatment of Natural Zeolite from Ende.
Flores (ZAEF) Natural zeolite from Ende.
Flores, was sorted, and light green-colored zeolite samples were selected.
The selected zeolite was washed, crushed into fine particles, passed through a 200mesh sieve, and weighed to obtain 500 g of sample.
The zeolite was then immersed in deionized water and stirred with a glass rod for 30 minutes at room temperature, followed by standing for 2 Subsequently, the filtrate was separated from the sediment.
The zeolite was then subjected to hydrothermal treatment.
ZAEF was placed in a pressure cooker and mixed with deionized water.
The zeolite suspension was heated at 100 AC for approximately 3 hours and then allowed to stand for 24 hours.
The hydrothermally treated ZAEF was filtered and transferred into a plastic container.
Deionized water was added until the container was half full, and the mixture was stirred with a glass rod for 1 hour.
After stirring, the ZAEF was allowed to stand for 24 hours.
This cleaning procedure was repeated using the same treatment until the ZAEF became clean and exhibited a bright green color.
Finally, the treated ZAEF was dried in an oven at 120 AC for 6 hours to obtain purified natural zeolite from Ende.
Flores.
Synthesis of SiOCC A total of 250 g of purified ZAEF was refluxed with 750 mL of 8 M NaOH solution for 24 hours, followed by filtration to obtain a sodium silicate solution.
The filtrate was then titrated with 2 M HCl to pH 7 under continuous stirring using a magnetic stirrer until a white precipitate The resulting white gel was aged at room temperature for 24 hours, then filtered and washed four times with 500 mL of deionized water to remove chloride salts, as confirmed by testing with 1% AgNOCE solution.
The neutral precipitate was separated by filtration using Whatman No.
42 filter paper.
The resulting solid was dried at 110 AC for 12 hours until a constant mass was achieved.
After cooling, the solid was weighed and ground into fine powder.
The silica powder was subsequently calcined at 1000 AC for 6 hours.
The calcined silica was then cooled, weighed, and finely ground using a porcelain mortar.
The prepared silica was used as the support material for CaO and MgO Synthesis of CaO Hard-water lime originating from Kupang.
East Nusa Tenggara, was collected, boiled, and washed with deionized water under stirring using a magnetic stirrer.
The material was then dried in an oven until completely dry.
The cleaned lime was sieved through a 140Ae200 mesh sieve.
total of 100 g of the sieved material was weighed using a digital balance and refluxed with 500 mL of 3 M HCl solution while continuously stirred with a magnetic stirrer until complete dissolution Page | 98 Nahak et al: Study of the Crystal Structure of CaO/SiO2.
The resulting solution was filtered and subsequently titrated with 1.
2 M NacOCE solution until the reaction was complete, resulting in the formation of CaCOCE precipitate.
The precipitate was separated from the solution and washed with deionized water until free from ClA ions.
The precipitate was then dried in an oven at 60 AC for 6 hours.
The dried CaCOCE solid was calcined at 1000 AC for 6 hours to obtain a CaO catalyst.
The prepared CaO catalyst was weighed and stored in a tightly sealed container until further use.
Synthesis of MgO A total of 200 g of MgCOCE was weighed and calcined at 800 AC for 6 hours.
After cooling, the resulting MgO was weighed, placed in a sealed container, and stored for further use.
Synthesis of CaO/SiOCC The CaO/SiOCC-15% catalyst was prepared by gradually adding 21.
25 g of CaO into 250 mL of deionized water to form a Ca(OH)CC suspension.
The catalyst composition consisted of 85% CaO and 15% SiOCC.
Subsequently, 3.
75 g of SiOCC was added to the suspension, and the mixture was continuously stirred using a magnetic stirrer at 400 rpm for 4 hours.
The suspension was then subjected to ultrasonic treatment for 3 hours, with intermittent manual stirring every 10 minutes.
After ultrasonic treatment, the mixture was allowed to stand for 24 hours to facilitate the deposition of Ca(OH)CC onto the SiOCC support.
The water solvent was removed by drying the suspension in an oven at 110 AC for 24 hours until completely dry.
The resulting powder was then calcined at 900 AC for 6 hours.
After cooling, the prepared catalyst was stored in a tightly sealed container for further use.
Synthesis of MgO/SiOCC The MgO/SiOCC catalyst was prepared by gradually adding 21.
25 g of MgO into 250 mL of deionized water to form an Mg(OH)CC suspension.
The catalyst composition consisted of 85% MgO and 15% SiOCC.
Subsequently, 3.
75 g of SiOCC was added to the suspension, and the mixture was continuously stirred using a magnetic stirrer at 400 rpm for 4 hours.
The suspension was then subjected to ultrasonic treatment for 3 hours, with intermittent manual stirring every 10 minutes.
After ultrasonic treatment, the mixture was allowed to stand for 24 hours to facilitate the deposition of Mg(OH)CC onto the SiOCC support.
The water solvent was subsequently removed by drying the suspension in an oven at 110 AC for 24 hours until completely dry.
The resulting powder was then calcined at 900 AC for 6 hours.
After cooling, the prepared catalyst was stored in a tightly sealed container for further use.
Synthesis of CaOAeMgO/SiOCC The CaOAeMgO/SiOCC catalyst was prepared by gradually adding 10.
625 g of MgO and 625 g of CaO into 250 mL of deionized water to form Mg(OH)CC and Ca(OH)CC suspensions.
The catalyst composition consisted of 42.
5% MgO, 42.
5% CaO, and 15% SiOCC.
Subsequently, 3.
75 g of SiOCC was added to the mixed suspension, and the mixture was continuously stirred using a magnetic stirrer at 400 rpm for 4 hours.
The suspension was then subjected to ultrasonic treatment for 3 hours, with intermittent manual stirring every 10 minutes.
After ultrasonic treatment, the mixture was allowed to stand for 24 hours to facilitate the deposition of the hydroxide precipitates onto the SiOCC support.
The water solvent was removed by drying the suspension in an oven at 110 AC for 24 hours until completely dry.
The resulting powder was then calcined at 900 AC for 6 hours.
After cooling, the prepared catalyst was stored in a tightly sealed container and was ready for characterization.
Page | 99 Jurnal eta Kimia.
Vol.
May .
, page 96-109 :https://doi.
org/10.
35508/jbk.
RESULTS AND DISCUSSION
Catalyst Characterization Using X-Ray Diffraction (XRD) Catalyst characterization using X-ray diffraction (XRD) was conducted to determine the crystal structure of the catalysts, including crystalline phases and phase composition, crystal system, and lattice parameters.
XRD analysis was performed on catalyst samples with different SiOCC compositions.
The analysis was carried out by placing the catalyst samples in the sample holder and irradiating them with X-rays over a 2 scanning range of 10AAe90A, using a copper (C.
X-ray source with a KCA wavelength of 1.
54 yI .
The resulting data were presented as diffractograms showing the relationship between the diffraction angle .
and X-ray intensity.
Figure 1.
Diffractograms of .
SiOCC, .
CaO, .
MgO, .
CaO/SiOCC, .
MgO/SiOCC, and .
CaOAeMgO/SiOCC.
SiO2 The XRD diffractogram of the SiOCC catalyst is presented in Figure 2.
The X-ray diffraction (XRD) analysis revealed that the mineral phase present in the SiOCC sample was identified as This phase corresponds to silicon dioxide (SiOCC), commonly known as silica, as referenced in the ICSD database.
Diffraction peaks were detected at 2 angles of 21.
76A and 21.
corresponding to the crystal plane orientations of .
, respectively.
Based on the analysis performed using Match! Software version 4, the tridymite phase was identified as having a triclinic crystal system with lattice parameters of a = 9.
9320 yI, b = 17.
2160 yI, and c = 81.
8640 yI, with lattice angles of = = = 90A.
The phase exhibited a calculated density of 2.
28100 g/cmA.
Page | 100 Nahak et al: Study of the Crystal Structure of CaO/SiO2.
Figure 2.
XRD diffractogram of SiOCC.
The formation of the tridymite phase in the SiOCC sample indicates that the silica material underwent a structural transformation from an amorphous phase to a more ordered crystalline Tridymite generally forms under high-temperature conditions, suggesting that the synthesis process or thermal treatment applied was sufficient to promote the recrystallization of the silica structure.
These findings are consistent with previous studies reporting that the formation of the tridymite phase is strongly influenced by high temperature, holding time, and the initial crystallinity of the material .
Those studies demonstrated that increasing synthesis temperature directly enhances tridymite crystal growth, as identified through XRD analysis.
addition, other studies have reported that tridymite is a high-temperature stable polymorph of SiOCC, commonly observed in materials subjected to extreme thermal treatment.
This has been described in studies on silica-based refractory materials, where the presence of tridymite was detected after heating at temperatures ranging from 900 to 1500 AC using XRD analysis .
The formation of the tridymite phase has important implications for the catalytic properties of the material, particularly in terms of improved thermal stability and structural Crystalline phases such as tridymite generally exhibit higher stability than amorphous phases, making the catalyst more resistant to high temperatures during catalytic reactions.
However, increased crystallinity may also result in a reduction in specific surface area, as the structure becomes more ordered and densely packed, potentially decreasing the number of available active sites.
Based on the diffraction pattern obtained, the characteristic SiOCC peaks were detected at 2 values of 21.
76A and 21.
82A, corresponding to the .
crystal planes, respectively.
The very small angular difference between these two peaks suggests a possible peak shift, which may indicate slight changes in lattice parameters or the presence of internal strain within the tridymite crystal structure.
This shift may have been induced by the synthesis process or thermal treatment, which could have triggered structural reorganization within the silica crystal framework, resulting in minor changes in interplanar spacing.
CaO The XRD diffractogram of the CaO catalyst is presented in Figure 3.
The X-ray diffraction (XRD) analysis revealed that the mineral phase present in the CaO sample was identified as the lime phase.
According to the ICSD database, this phase corresponds to calcium oxide (CaO).
Diffraction peaks were observed at 2 values of 32.
24A, 32.
32A, 37.
39A, 37.
49A, and 53.
corresponding to the crystal plane orientations of .
, .
, .
, .
, and .
, respectively.
Based on the analysis performed using Match! Software version 4, the lime phase was identified Page | 101 Jurnal eta Kimia.
Vol.
May .
, page 96-109 :https://doi.
org/10.
35508/jbk.
as having a cubic crystal system with lattice parameters of a = b = c = 4.
8110 yI and lattice angles of = = = 90A.
The phase exhibited a calculated density of 2.
92700 g/cmA.
Figure 3.
XRD diffractogram of CaO.
The identification of the lime phase (CaO) in the sample indicates that the material successfully underwent an effective calcination process, during which precursor compounds such as CaCOCE were decomposed into CaO.
The appearance of sharp diffraction peaks suggests that the resulting CaO possesses a high degree of crystallinity with a stable cubic crystal structure, indicating that the thermal treatment applied was sufficient to optimally form the catalytically active phase.
These findings are consistent with previous studies reporting that calcined CaO exhibits characteristic diffraction patterns associated with a cubic crystal structure, with crystallinity increasing as calcination temperature rises .
In addition, other studies have demonstrated that the crystalline characteristics of CaO, including crystal size and diffraction peak intensity, are strongly influenced by thermal treatment conditions and play a significant role in determining the material properties .
The formation of the CaO phase has important implications for the catalytic properties of the material, particularly in terms of enhanced basicity and catalytic activity.
CaO is a heterogeneous basic catalyst containing active OAA ion sites that facilitate catalytic reactions.
well-defined crystalline structure contributes to improved thermal stability.
however, excessive crystal growth may reduce the specific surface area, thereby decreasing the number of accessible active sites.
Based on the diffraction pattern, characteristic CaO peaks were observed at 2 values of 24A and 32.
32A, as well as 37.
39A and 37.
49A, corresponding to the .
, .
, .
, and .
crystal planes, respectively.
The close proximity of these diffraction peaks may indicate subtle variations in lattice parameters or the presence of internal strain within the CaO crystal structure.
Such variations may arise from non-uniform calcination conditions, which can lead to slight lattice distortions within the crystalline framework.
MgO The XRD diffractogram of the MgO catalyst is presented in Figure 4.
The X-ray diffraction (XRD) analysis revealed that the mineral phase present in the MgO sample was identified as the periclase phase.
According to the ICSD database, this phase corresponds to magnesium oxide (MgO).
Diffraction peaks were detected at 2 values of 36.
91A, 37.
00A, 42.
89A, 43.
00A, and 62.
corresponding to the crystal plane orientations of .
, .
, .
, .
, and .
, respectively.
Page | 102 Nahak et al: Study of the Crystal Structure of CaO/SiO2.
Based on the analysis performed using Match! Software version 4, the periclase phase was identified as having a cubic crystal system with lattice parameters of a = b = c = 4.
2160 yI and lattice angles of = = = 90A.
The phase exhibited a calculated density of 3.
57200 g/cmA.
Figure 4.
XRD diffractogram of MgO.
The formation of the periclase phase (MgO) indicates that the material underwent an effective calcination or thermal treatment process, resulting in the formation of a stable crystalline MgO structure.
This phase represents the most thermodynamically stable crystalline form of magnesium oxide at elevated temperatures, and its presence indicates the successful transformation of the precursor into a pure oxide phase .
These findings are consistent with previous studies reporting that MgO typically crystallizes in a cubic periclase structure, characterized by prominent diffraction peaks associated with the .
, .
, and .
crystal planes, which commonly appear at 2 values in the ranges of approximately 36AAe43A and 62A .
The formation of the periclase phase has important implications for the catalytic properties of the material, particularly in terms of enhanced basicity, as MgO is widely recognized as a strong heterogeneous basic catalyst.
The stable cubic crystal structure also contributes to improved thermal stability and provides active surface sites that play a significant role in catalytic reactions, particularly those involving base-catalyzed mechanisms such as transesterification .
Based on the diffraction pattern, characteristic MgO .
peaks were observed at 2 values of 36.
91A and 37.
00A, as well as 42.
89A and 43.
00A, corresponding to the .
, .
, .
, and .
crystal planes, respectively.
The close proximity of these diffraction peaks may suggest subtle variations in lattice parameters or the presence of internal strain within the MgO crystal Such variations may arise from non-uniform calcination conditions or the presence of crystal defects, which could lead to slight lattice distortions in the formed periclase phase.
CaO/SiO2 The XRD diffractogram of the CaO/SiOCC catalyst is presented in Figure 5.
The X-ray diffraction (XRD) analysis revealed that the mineral phase present in the CaO/SiOCC sample consisted of a single phase, identified as larnite.
According to the ICSD database, this phase corresponds to calcium silicate (CaCCSiOCE).
Diffraction peaks were detected at 2 values of 18.
92A, 32.
01A, 33.
20A, and 34.
20A, corresponding to the crystal plane orientations of .
, .
, .
, .
, and .
, respectively.
Based on the analysis performed using Match! software version 4, the larnite phase was identified as having a monoclinic crystal system with lattice parameters of a = 5.
50770 yI, b = 6.
75050 yI, and c = 9.
34080 yI, with lattice angles of = = 90A and = 94.
The phase exhibited a calculated density of 3.
30500 g/cmA.
Page | 103 Jurnal eta Kimia.
Vol.
May .
, page 96-109 :https://doi.
org/10.
35508/jbk.
Figure 5.
XRD diffractogram of CaO/SiOCC.
The formation of the larnite phase (CaCCSiOCE) indicates that chemical interactions occurred between CaO and SiOCC during the synthesis or calcination process, resulting in the formation of a thermally stable calcium silicate compound.
This phase is commonly formed at elevated temperatures through a solid-state reaction between CaO and SiOCC, indicating the successful synthesis of a homogeneous composite material .
These findings are consistent with previous reports indicating that CaCCSiOCE .
exhibits a monoclinic crystal structure with characteristic diffraction peaks within the 2 range of approximately 18AAe35A .
The formation of the larnite phase has important implications for the catalytic properties of the material, particularly through the combination of the basic properties of CaO and the supporting characteristics of SiOCC, resulting in improved thermal stability and a more uniform distribution of active sites.
CaCCSiOCE has also been reported to exhibit favorable catalytic activity in base-catalyzed reactions, such as transesterification, due to the presence of Ca ions that contribute to catalytic activity .
Based on the diffraction pattern, characteristic CaCCSiOCE .
peaks were observed at 2 values of 31.
92A and 32.
01A, as well as 33.
20A and 34.
20A, corresponding to the .
, .
, .
, and .
crystal planes, respectively.
The close proximity of these diffraction peaks may indicate subtle variations in lattice parameters or the presence of internal strain within the CaCCSiOCE crystal Such variations may arise from interactions between CaO and SiOCC during the calcination process, which may not have occurred entirely homogeneously, thereby leading to slight lattice distortions in the formed larnite phase.
MgO/SiO2 The XRD diffractogram of the MgO/SiOCC catalyst is presented in Figure 6.
The X-ray diffraction (XRD) analysis revealed that the mineral phases identified in the MgO/SiOCC sample consisted of three major phases, namely periclase, olivine, and tridymite.
The phase composition analysis indicated that periclase accounted for 50.
6% of the sample, followed by olivine at 48.
and tridymite at 0.
Page | 104 Nahak et al: Study of the Crystal Structure of CaO/SiO2.
Figure 6.
XRD diffractogram of MgO/SiOCC.
The periclase phase, identified in the ICSD database as magnesium oxide (MgO), was detected at 2 values of 36.
74A, 42.
91A, 43.
02A, 62.
27A, and 62.
24A, corresponding to the crystal plane orientations of .
, .
, .
, .
, and .
, respectively.
Based on the analysis performed using Match! software version 4, the periclase phase was identified as having a cubic crystal system with lattice parameters of a = b = c = 4.
2160 yI and lattice angles of = = = 90A, with a calculated density of 3.
57200 g/cmA.
The olivine phase, identified in the ICSD database as magnesium silicate (MgCCSiOCE), was observed at 2 values of 17.
45A, 22.
94A, 23.
96A, 25.
57A, and 25.
63A, corresponding to the crystal plane orientations of .
, .
, .
, .
, and .
, respectively.
Based on the analysis using Match! software version 4, the olivine phase exhibited an orthorhombic crystal system with lattice parameters of a = 4.
7400 yI, b = 10.
1985 yI, and c = 5.
9792 yI, with lattice angles of = = = 90A, and a calculated density of 3.
22700 g/cmA.
The tridymite phase, identified in the ICSD database as silicon dioxide (SiOCC), commonly known as silica, was detected at 2 values of 10.
17A, 21.
67A, 23.
00A, 23.
96A, and 24.
02A, corresponding to the crystal plane orientations of .
, .
, .
, .
, and .
, respectively.
Based on the analysis performed using Match! software version 4, the tridymite phase was identified as having a cubic crystal system with lattice parameters of a = b = c = 20.
97788 yI and lattice angles of = = = 90A, with a calculated density of 1.
03700 g/cmA.
The dominance of the periclase and olivine phases suggests that the interaction between MgO and SiOCC proceeded effectively, resulting in the formation of magnesium silicate (MgCCSiOCE), while residual unreacted MgO remained in the periclase phase.
The presence of the tridymite phase indicates that a small fraction of free SiOCC underwent recrystallization during the calcination process.
The formation of these three phases indicates that relatively complex interactions occurred between MgO and SiOCC during the synthesis process.
The periclase phase suggests that a portion of MgO remained in the form of free oxide, whereas the formation of the olivine phase (MgCCSiOCE) confirms the occurrence of a high-temperature solid-state reaction between MgO and SiOCC, resulting in the formation of thermally stable magnesium silicate.
The presence of the tridymite phase indicates that part of the SiOCC transformed from an amorphous phase to a crystalline phase due to thermal treatment .
These findings are consistent with previous reports indicating that MgO can react with SiOCC at elevated temperatures to form MgCCSiOCE .
, while SiOCC may transform into crystalline phases such as tridymite under similar Page | 105 Jurnal eta Kimia.
Vol.
May .
, page 96-109 :https://doi.
org/10.
35508/jbk.
The formation of these three phases has significant implications for the catalytic properties of the material.
The periclase phase (MgO) serves as an important active basic site in catalytic reactions.
The olivine phase (MgCCSiOCE) contributes to the thermal stability and mechanical strength of the material, although its basicity is generally lower than that of pure MgO.
Meanwhile, the tridymite phase (SiOCC) functions as a support material that may enhance surface area and promote a more uniform distribution of active sites .
Based on the diffraction pattern, characteristic MgO .
peaks were observed at 2 values of 42.
91A and 43.
02A, as well as 62.
24A and 62.
27A, corresponding to the .
, .
, .
, and .
crystal planes, respectively.
Similarly, the MgCCSiOCE .
phase exhibited closely spaced peaks at 2 values of 25.
57A and 25.
63A, corresponding to the .
crystal planes.
The SiOCC .
phase also showed adjacent peaks at 2 values of 23.
96A and 24.
corresponding to the .
crystal planes.
The proximity of these diffraction peaks may suggest subtle variations in lattice parameters or the presence of internal strain within the crystal Such variations may result from interactions between MgO and SiOCC during synthesis and calcination that may not have occurred entirely homogeneously, thereby leading to slight lattice distortions in the formed periclase, olivine, and tridymite phases.
CaO-MgO/SiO2 The X-ray diffraction (XRD) analysis revealed that the mineral phases identified in the CaOAeMgO/SiOCC sample consisted of two phases, namely olivine and portlandite, with phase compositions of 60.
7% and 39.
3%, respectively.
Figure 7.
XRD diffractogram of CaOAeMgO/SiOCC.
The olivine phase, identified in the ICSD database as magnesium silicate (MgCCSiOCE), was detected at 2 values of 22.
90A, 22.
96A, 29.
53A, 32.
33A, and 32.
41A, corresponding to the crystal plane orientations of .
, .
, .
, .
, and .
, respectively.
Based on the analysis performed using Match! software version 4, the olivine phase was identified as having an orthorhombic crystal system with lattice parameters of a = 4.
74900 yI, b = 10.
19850 yI, and c = 5.
97920 yI, with lattice angles of = = = 90A.
The calculated crystal density was 3.
22700 g/cmA.
The portlandite phase, identified in the ICSD database as calcium hydroxide (Ca(OH)CC), was observed at 2 values of 18.
06A, 28.
68A, 34.
08A, 34.
16A, and 36.
63A, corresponding to the crystal plane orientations of .
, .
, .
, .
, and .
, respectively.
Based on the analysis performed using Match! software version 4, the portlandite phase exhibited a trigonal crystal system with lattice parameters of a = b = 3.
59250 yI and c = 4.
90500 yI.
The lattice angles were = Page | 106 Nahak et al: Study of the Crystal Structure of CaO/SiO2.
= 90A, while was consistent with the trigonal crystal symmetry.
The calculated crystal density 24400 g/cmA.
The dominance of the olivine phase suggests that a solid-state reaction occurred between MgO and SiOCC, resulting in the formation of thermally stable magnesium silicate.
Meanwhile, the presence of the portlandite phase indicates that residual CaO likely reacted with moisture to form Ca(OH)CC during the cooling process or after calcination.
The formation of the olivine phase confirms that interactions between MgO and SiOCC occurred during the synthesis and calcination processes, leading to the formation of a thermally stable magnesium silicate compound.
In contrast, the formation of the portlandite phase indicates partial hydration of CaO into Ca(OH)CC due to exposure to water vapor or ambient moisture during synthesis or sample storage.
The presence of these two phases suggests that the synthesis process resulted not merely in a physical mixture, but also in chemical transformations among the constituent components of the material.
These findings are consistent with previous reports indicating that the olivine phase commonly forms in MgOAeSiOCC systems following hightemperature thermal treatment, whereas portlandite frequently appears as a result of CaO hydration .
Based on the diffraction pattern, the olivine phase exhibited closely spaced diffraction peaks at 2 values of 22.
90A and 22.
96A, as well as 32.
33A and 32.
41A, corresponding to the .
, .
, .
, and .
crystal planes, respectively.
Meanwhile, the portlandite phase showed adjacent peaks at 2 values of 34.
08A and 34.
16A, corresponding to the .
crystal The close proximity of these diffraction peaks may indicate subtle variations in lattice parameters or the presence of internal strain within the crystal structures .
Such variations may arise from interactions among CaO.
MgO, and SiOCC during synthesis and calcination that may not have occurred entirely homogeneously, thereby leading to slight lattice distortions in the formed olivine and portlandite phases.
Table 1.
XRD analysis data of SiOCC.
CaO.
MgO.
CaO/SiOCC.
MgO/SiOCC, and CaOAeMgO/SiOCC Sample Phase
Crystal
Structure Lattice Parameters SiO2
Tridymite Triclinic c=9,9320 yI
Phase
Composition b=17,21600 yI
c=81,86400 yI
CaO
Lime
Cubic
c=b=c= 4,8110 yI
MgO
Periclase Cubic
c=b=c= 4,21600 yI
CaO/SiO2 Larnite Monoclinic c=5,50770 yI
b=6,75050 yI
c=9,34080 yI
Periclase Cubic
Olivine Orthorhombic MgO/SiO2 c=b=c= 4,21600 yI
50,6%
c=4,74000 yI
48,7%
b=10,19850yI c=5,97920 yI
Tridymite Cubic
c=b=c= 20,97788 yI
0,8%
Page | 107 Jurnal eta Kimia.
Vol.
May .
, page 96-109 Olivine CaOMgO/SiO2 Orthorhombic :https://doi.
org/10.
35508/jbk.
c= 4,74900 yI
60,7%
b=10,19850 yI
c= 5,97920 yI
Portlandite Trigonal c= b=3,59250 yI
39,3%
c= 4,90500 yI
CONCLUSION
Based on the X-ray diffraction (XRD) characterization results, the SiOCC.
CaO.
MgO.
CaO/SiOCC.
MgO/SiOCC, and CaOAeMgO/SiOCC samples successfully formed distinct crystalline phases depending on their composition and synthesis conditions.
The SiOCC sample formed the tridymite phase.
CaO formed the lime phase, and MgO formed the periclase phase, indicating the successful calcination process and the formation of stable crystalline structures.
In the composite materials, the larnite phase was identified in CaO/SiOCC, while olivine, periclase, tridymite, and portlandite phases were detected in MgO/SiOCC and CaOAeMgO/SiOCC, confirming the occurrence of chemical interactions among the oxide components during the synthesis process.
The formed phases significantly influenced the catalytic properties of the materials, particularly in enhancing thermal stability, basicity, and the distribution of active sites.
In addition, the presence of closely spaced diffraction peaks suggests subtle variations in lattice parameters and possible internal crystal strain induced by the synthesis and calcination processes.
Overall, the combination of CaO.
MgO, and SiOCC successfully produced heterogeneous catalytic materials with crystalline characteristics that demonstrate potential for application in base-catalyzed reactions.
REFERENCES