Synthesis and Characterization of Zeolite-Y from Bularafa Diatomaceous Earth for Catalytic Cracking of Liquid Paraffin

439 Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 439-448 p ISSN: 2635-3342; e ISSN: 2635-3350 Original Research Article Synthesis and Characterization of Zeolite-Y from Bularafa Diatomaceous Earth for Catalytic Cracking of Liquid Paraffin *1Mohammed, H.I., 1Aji, M.M., 2Mohammed, B.F. and 1Pius M.U. 1Department of Chemical Engineering, University of Maiduguri, Maiduguri, Nigeria. 2Department of Chemistry, University of Maiduguri, Maiduguri, Nigeria. *[email protected] http://doi.org/10.5281/zenodo.18061446 ARTICLE INFORMATION ABSTRACT Article history: Received 04 Sep. 2025 Revised 09 Oct. 2025 Accepted 10 Oct. 2025 Available online 30 Dec. 2025 The compelling need to develop zeolites locally from the available abundant resource and test their performance is rooted in the need for local content development and the high cost of importation. This study presents the synthesis and characterization of zeolite-Y from Bularafa Diatomaceous Earth (BDE) for the conversion of liquid paraffin to fuels and petrochemicals. The Bularafa Diatomaceous Earth was characterized using X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD), and zeolite was synthesized via hydrothermal route at 150 ℃ for 8 hours. The zeolite was characterized using nitrogen adsorption-desorption analysis, X-Ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR) and thermogravimetric analysis (TGA).The performance of the zeolite was evaluated for conversion of liquid paraffin to fuel or petrochemical feedstock in downdraft fixed bed reactor. The outcome indicates that BDE is rich in silica small fraction of alumina, and has a tridymite crystal phase. The product from hydrothermal crystallization was confirmed to be zeolite-Y with impurities. The BET multi point specific surface area, pore diameter were 178.3 m2/g and 1.54 to 5.88 nm, respectively. The zeolite was stable over a temperature range of 30 to 700 ℃. The zeolite was selective towards aromatics formation, yielding 54%. The zeolite-derived BDE is effective in the conversion of liquid paraffin to aromatics. Further improvement is needed to improve the selectivity of the zeolite for a specific product. © 2025 RJEES. All rights reserved. Keywords: Catalyst Catalytic cracking Diatomaceous earth Synthesis Zeolite 1. INTRODUCTION Despite the maturity of research in the synthesis of zeolites and their application in petroleum refining and petrochemicals applications, the need to exploit alternative cheaper materials for zeolites and evaluate their performance in refinery operations for local content development is imperative. 440 H.I. Mohammed et al. / Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 439-448 Advancements in catalyst development locally will contribute to energy sustainability. Zeolites are being synthesized from pro analytical silicate and aluminate precursor, which makes it very expensive (Krisnandi et al., 2019). Efforts to reduce costs have triggered investigation into usage of natural aluminosilicate mineral deposits. Several sources of silica and alumina have been reported (Czuma, Franus, Zabierowski, and Zare, 2019; Ghasemi and Vajheh, 2014;; Sri Rahayu et al., 2018). These are kaolin clay , diatomite, and ash (Klunk et al., 2019). The source and structure of silica strongly affect the crystal size and crystallinity of the final product (Alipour et al., 2014). Silica sources, formed from the mono-Si structural unit, for instance, SiO2, crystallized faster than silica sources, contain a network of Si structural units (Mohammed et al., 2023). Kaolin is rich in silica and alumina but in its natural form does not react, unless activated via thermal treatment at very high temperature of above 550 oC. The activation of kaolinite results in elimination of structural water and formation of metakaolin (Sri Rahayu et al., 2018). The process involves high energy consumptions, which might add cost to production of zeolite form the precursor. In addition, kaolin has silica/alumina ratio, approximately 1 to 4 (Garcia-Valles et al., 2020), this might require addition of silica for synthesis of high silica zeolites. On the other hand, diatomaceous earth is very rich in silica (70 to 90%) and alumina (2 to 13%) and does not require such treatments and externally sourced silica for it to be used in synthesis of high silica zeolite (Danil de Namor et al., 2012) . Aguilar-Mamani et al. (2014) compared synthesis of zeolite from kaolin and diatomite. They reported that use of leached diatomaceous earth allowed higher yield of zeolite crystals within comparable synthesis times. Li et al., (2015) synthesized zeolite hydrothermally from commercial diatomaceous in the presence of tetra-propyl ammonium bromide as structural directing agent. They reported that specific surface area of 223 m2 g-1 obtained and the catalyst was effective in catalytic cracking of vacuum gas oil to butylene and propylene. The products indicate perhaps β-scission that involves the breaking of carbon-carbon bonds directly, leading to smaller molecules of higher value. There are abundant diatomite in Bularafa, Gujba Local Government Area, Yobe State, Nigeria (Otitodun et al., 2015) unexploited due to lack of scientific and technical data. This study focuses on utilization of the Bularafa Diatomaceous Earth (BDE) in the synthesis of zeolite Y for catalytic cracking of liquid paraffin to fuel grade hydrocarbons. 2. MATERIALS AND METHODS 2.1. Acquisition and Preparation of Diatomaceous Earth The diatomaceous earth sample was obtained from the mining site at Bularafa. Gujba Local Government Area, Yobe State. The sample was milled and sieved. The powder that passed through a 150 micron sieve were collected, dried and stored in desiccator for subsequent characterization and zeolite synthesis. 2.2. Characterization of Bularafa Diatomite Bularafa diatomaceous earth was characterized to provide a comprehensive understanding of clay properties, enabling its effective use in zeolite synthesis. The diatomite sample was acquired from the mining site and characterized using PANalytical/Rigaku software diffractometer using X-ray diffraction spectroscopy (XRD)to reveal mineralogical phases. The oxide composition of the metals was determined using Geological Calibration Oxide in Air method in X-ray florescence (XRF)to provide information on elemental oxide composition. 2.3. Preparation of the Zeolite Catalysts Predetermined quantity of Bularafa diatomite was dissolved in highly concentrated sodium hydroxide solution and the pH was adjusted in the range of 11 to 12. Thereafter, structural directing agent such as tetrapropyl ammonium bromide, TPABr, was added and stirred for 30 minutes. The gel formed was transferred to pressurized Teflon-coated stainless-steel autoclave.and placed in oven for 8 hours at 150˚C. The content of the autoclave was filtered and washed with deionized water until the filtrate is neutral. The crystal was calcined at 550 oC for 6 hours to remove the organic template then refluxed with 1 M of ammonia solution at 90 oC for two hours and dried in oven, and stored in desiccator for characterizations and catalytic cracking experiments. 441 H.I. Mohammed et al. / Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 439-448 2.4. Characterization of the Prepared Powder Several methods were used to examine the properties of the zeolite-based catalyst, synthesised from Bularafa diattomite. The surface area and pore distribution were determined using nitrogen adsorption-desorption tests on the NOVAQuantachrome version 11.03. The surface function and fingerprints were examined using Fourier transform infrared (FTIR) spectroscopy on a PerkinElmer Spectrum 100. The crystal structure and phase were ascertained on a PANalytical/Rigaku software diffractometer using X-ray diffraction spectroscopy (XRD), and thermal stability was determined using a thermogravimetric analysis (TGA) on a PerkinElmer TGA analyzer. 2.5. Catalytic Cracking Experiments The synthesized Zeolite Y was used for catalytic cracking of liquid paraffin in a fixed bed reactor catalyst testing rig presented in Figure 1. The liquid paraffin was injected into the vaporizer and the vapour phase flow into the catalyst bed, contacted with the zeolite catalysts and the cracking reactions occur. The reaction products flows out and condensed, collected and store for characterizations. Figure 1: Catalysts testing apparatus for catalytic cracking of liquid paraffin 2.6. Characterization of Liquid Paraffin and the Cracked Products The Gas Chromatography Mass Spectrometer (GC-MS) and Fourier Transform Infra-red were used to characterized the feedstock and catalytic cracking products. This is to ascertain the composition of the liquid paraffin prior to catalytic cracking experiments. Similarly, the catalytic cracking products were examined to determine the dominant compound and evaluate the activity and selectivity of the catalysts. 3. RESULTS AND DISCUSSION 3.1. Crystallography and Chemical Composition of Bularafa Diatomaceous Earth The XRD pattern of the sample obtained from Bularafa is presented in Figure 2. The broad peak centered around 20-25o (CuKα radiation) indicates amorphous silica. This distinguished the sample from the quartz that peaks are sharp. The results confirmed that the sample obtained from Bularafa is diatomaceous earth (Yunusa et al., 2020). 442 H.I. Mohammed et al. / Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 439-448 The quantitative composition shows substantial quantity of diatomite. The results further confirm that the sample is diatomaceous earth. The XRF results for the sample obtained from Bularafa is presented in Table 1. The sample is rich in silica and alumina. Silica and alumina are key constituents required for a sample to serve as a precursor for zeolite preparation (Indira and Abhitha, 2022; Maciver et al., 2020). Table 3 compares the chemical composition of the Burafa diatomaceous earth to Tabris Diatomaceous earth (Mahani and Kazemeini, 2003) . The Bularafa diatomaceous earth is high in silica and low in alumina and can be used for synthesis of various zeolites of interest. Figure 2: XRD Pattern of Bularafa diatomaceous earth Table 1: Chemical composition of Bularafa diatomaceous earth Metal oxides Composition (wt%) This study Mahani and Kazemeini, (2003) SiO2 75.316 76.390 Al2O3 1.769 8.470 Na2O 5.44 0.360 K2O 0.137 1.180 MgO 1.460 0.210 CaO 0.511 0.660 Fe2O3 5.968 2.260 TiO2 0.246 0.080 MoO3 0.572 - SrO 4.817 - SnO2 1.023 - Bi2O3 0.723 - Nb2O5 0.520 - Figure 3 depicts the XRD pattern for zeolite synthesised from Bularafa Diatomaceous Earth. The diffraction pattern is different from that exhibited by diatomaceous earth, the feedstock. This indicates phase transformation of the feedstock, from amorphous to crystalline material. The material exhibited a diffraction pattern with primary peaks between 6.2, 11.9, 15.7, 18.7, 20.4,23.7, 27.1 and 31.4 corresponding to the described diffraction pattern for zeolite-Y, indicating that zeolite-Y was synthesized (Bahgaat et al., 2020; Ernest et al., 2019). The Fourier Transform Infra-red (FTIR) spectra of the material is presented in Figure 4. The smoothness of the spectrum indicates a three-dimensional framework. The variation in dipole moment regarding distance and the interaction of unit cells with their surroundings caused the change in intensity and band. The presence of two or more peaks indicates the presence of crystals. The internal vibration of the tetrahedral Si-O-Al 0 200 400 600 800 1000 1200 1400 1600 010 20 30 40 50 60 70 Intensity 2θ (o) 443 H.I. Mohammed et al. / Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 439-448 asymmetric stretching is shown by the first peak at 808-1237 cm-1. The peaks at 700 to 800 cm-1 conforms to symmetrical stretch of Si-O or Al-O bonds, vibration from the framework of the zeolite-Y, causes the second peak at 700 cm-1 (Safitri et al., 2020). This relates to a characteristic property of zeolite with a threedimensional framework in which two tetrahedral shared oxygen molecules (Mujiyanti et al., 2021). The vibration of external linkages in unit cells resulted in the peak around 650 cm-1 band. The 1050-1150 cm-1 band corresponds to a pore opening (Gackowski and Datka, 2020). These functional groups and fingerprints are essential for catalyzing the cracking reaction. Figure 3: XRD pattern of zeolite derived from Bularafa diatomaceous earth Figure 4: FTIR of zeolite-Y The thermogravimetric analysis (TGA) of the zeolite is presented in Figure 5. The TG shows no weight loss over a temperature range of 30 to 700 oC. This indicates the stability of the zeolite at high temperature. This shows that the zeolite is stable the reaction temperatures of the catalytic cracking operations. The Dubinin –Ashtokov plot of pore volume against pore diameter of the zeolite is presented in Figure 6. The pore diameter ranges from 1.54 to 5.88 nm , showing heterogeinity nature of the pores. The pore diameter of up to 2 nm is classified as microporous, while above 2 to 50 is mesoporous (Schlumberger and Thommes, 2021). A maximum pore volume of 0.06 cm³/g is a relatively modest value, suggesting a material 0 500 1000 1500 2000 2500 3000 3500 4000 010 20 30 40 50 60 70 Intensity 2θ 0 20 40 60 80 100 120 140 40080012001600200024002800320036004000 Intensity Wavenumber (cm-1) 444 H.I. Mohammed et al. / Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 439-448 with a moderate degree of porosity. This value indicates that the material possesses a network of small pores. This information, combined with the pore size distribution, is critical for applications of catalysis, such as catalytic cracking. The structure of this zeolite will enhance adsorption of wide range hydrocarbon molecules in the feedstock into the catalyst during reaction process. This selective diffusion of range hydrocarbon molecule is crucial for controlling the cracking process and maximizing the yield of desired products. The zeolite is hierarchical, and excellent in overcoming diffusion limitations during heavy oil cracking applications (Li et al., 2015). Figure 5: TGA of zeolite synthesized from diatomaceous earth Figure 6: Pore size distribution of the zeolite-Y Furthermore, Table 2 presents the surface area, pore diameter, and adsorption energy of the zeolite. The surface area is essential in catalyzing chemical reactions. The surface area of the zeolite obtained is 178.3 m2/g. this lower than the results obtained by Li et al., (2015). This might be due to high purity of commercial diatomaceous earth compared to the one used in this study. -20 0 20 40 60 80 100 120 0 200 400 600 800 Weight loss (%) Temperature (°C) Weight % Deriv. Weight %/min 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 02468 Pore volume (cm3/g) Pore diameter (nm) 445 H.I. Mohammed et al. / Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 439-448 Table 2: Textural characteristics of zeolite--Y Parameters This study Ernest et al. (2019) Specific surface area by multi-point BET (m2/g) 178.3 45.6 Total pore volume by BJH method (cm3/g) 0.10 0.18 BJH mesopore diameter (nm) (Average) 2.14 1.7 DR mesopore diameter (nm) (maximum) 6.93 - DA micropore diameter (nm) (Minimum) 2.76 - DA adsorption energy (kJ/mol) 0.71 - DR adsorption energy (kJ/mol) 4.17 - 3.3. Chemical Composition of the Liquid Paraffin and Products of Catalytic Cracking The FTIR spectrum of the liquid paraffin and the cracked products is shown in Figure 7, and the peaks are presented Table 3. The peaks at 2937, 2914, and 2847 cm⁻¹ are characteristic of alkane C-H stretching vibrations, while peaks at 2937 and 2914 cm⁻¹ correspond to the asymmetric and symmetric stretching of methylene (-CH₂-) groups, respectively (Villamarin-Barriga et al., 2020). The peak at 2847 cm⁻¹ indicates of the symmetric stretching of methyl (-CH₃) groups. The peak at 1446 cm⁻¹ and 1364 cm⁻¹ corresponds to the C-H scissoring (bending) vibration of methylene (-CH₂-) groups and C-H bending vibration in methyl (-CH₃) groups, respectively (Mujiyanti et al., 2021). The peak at 715 cm⁻¹ is characteristic of the rocking motion of a chain of four or more methylene (-CH₂-) groups (Mackie et al., 2016). This further supports the presence of a long, straight aliphatic chain. The presence of straight aliphatic chain might be due to incomplete conversion of the liquid paraffin. The chromatographic composition of the liquid paraffin and the cracked products. The presence and intensity of these peaks strongly suggest a long aliphatic chain. Figure 7: FTIR of liquid paraffin and the cracked product Table 3: Peaks of the FTIR spectrum Wavenumber (cm⁻¹) Vibration type Functional group Inference 2937 and 2914 Asymmetric and Symmetric C-H Stretch Methylene (-CH₂-) Long aliphatic chain 2847 Symmetric C-H Stretch Methyl (-CH₃-) Alkane structure 1446 C-H Scissoring Methylene (-CH₂-) Alkane backbone 1364 C-H Bending Methyl (-CH₃-) Alkane backbone 715 -CH₂Rocking Long Methylene Chain Indicates a long, straight chain 0 50 100 150 200 250 500150025003500 Intensity Wavenumber (cm-1) DZP 446 H.I. Mohammed et al. / Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 439-448 Chromatographic composition of the liquid paraffin is presented in Figure 8. The liquid paraffin comprises pentadecane through to nonacosane, that’s nineteen to 29 carbon chains. The chromatographic composition confirms that the liquid paraffin is a saturated hydrocarbon. The liquid paraffin can be practically served as feedstock for production of fuel grade hydrocarbon liquid via catalytic process. Figure 8: Chemical composition of liquid paraffin Figure 9 shows the composition of products obtained from catalytic processing of liquid paraffin over zeolite synthesized from Bularafa Diatomaceous earth. The products majorly consist of aromatics, small amount of aliphatic and olefinic hydrocarbons. The variations in compositions of liquid paraffin from the reaction products indicate the activity of the catalyst. The aliphatic component, such as nonadecane about 5% is the unconverted liquid paraffin, while tridecane might be product from cracking of the longer chain hydrocarbon. The olefinic compound, 1-decene account about 3%, a typical product of β-scission of carboncarbon bonds. The abundance of aromatics in the processed sample indicates that zeolite is selective towards aromatics compounds. Acidic catalysts such as zeolite-Y facilitate cracking, cyclization and aromatization reactions under high temperature and lower pressure (Gackowski and Datka, 2020; Wei et al., 2025). Figure 9: Chemical composition of the products 4. CONCLUSION The synthesis, characterization of zeolite-Y from Bularafa Diatomaceous earth and subsequent testing for catalytic cracking was accomplished, it was concluded that: 447 H.I. Mohammed et al. / Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 439-448 • Bularafa diatomaceous earth is rich in amorphous silica, thus viable feedstock for zeolite synthesis. • The zeolite Y synthesized has good specific surface area pore size distribution, good for a catalytic cracking operation • The zeolite was effective in conversion of liquid paraffin to aromatics. The catalyst performance of the zeolite can be modified to improve it’s properties. 5. ACKNOWLEDGMENT` The authors wish to acknowledge the financial support by Tertiary Education Trust Fund (TETFund) under Institution-Based Research (IBR) Grant, 2019-2024 cycle. 6. CONFLICT OF INTEREST There is no conflict of interest associated with this work. REFERENCES Aguilar-Mamani, W., García, G., Hedlund, J., and Mouzon, J. (2014). Comparison between leached metakaolin and leached diatomaceous earth as raw materials for the synthesis of ZSM-5. 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