Rozafia, Ade Irma (2026) Granulasi Basah Katalis SiO2 Dari Lumpur Geotermal Terimpregnasi Nikel Untuk Metanasi CO2. Doctoral thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Lumpur geotermal merupakan limbah padat yang berpotensi dimanfaatkan sebagai sumber silika untuk pembuatan material mesopori dan penyangga katalis. Penelitian ini bertujuan memurnikan silika dari lumpur geotermal, sintesis MCM-41 pada berbagai variasi kondisi hidrotermal, impregnasi nikel pada MCM-41, serta mengevaluasi pengaruh urutan impregnasi dan granulasi terhadap karakteristik katalis berbentuk granul. Pemurnian lumpur geotermal dilakukan melalui pemisahan magnetik dan pelindian asam, sedangkan MCM-41 disintesis menggunakan CTAB sebagai pengarah struktur pada suhu hidrotermal 100, 120, dan 150 °C selama 12, 24, dan 48 jam. Nikel diembankan melalui metode impregnasi dengan variasi kandungan 5, 10, dan 15 wt.%. Granul dibentuk menggunakan natrium alginat 4% dan pengikatan silang dengan CaCl₂ melalui dua urutan proses, yaitu granulasi serbuk Ni/MCM-41 dan impregnasi Ni setelah pembentukan granul MCM-41. Kombinasi pemisahan magnetik dan pelindian meningkatkan kandungan SiO2 menjadi 95,2 wt.% serta menurunkan Fe2O3 dari 9,82 menjadi 2,60 wt.%, tanpa mengubah karakter amorf silika. Pola XRD sudut rendah MCM-41 menunjukkan refleksi (100), (110), dan (200), yang mengonfirmasi terbentuknya susunan kanal mesopori heksagonal. Kondisi 100 °C selama 24 jam menghasilkan luas permukaan BET tertinggi sebesar 1.037,91 m2/g, volume pori total 0,9337 cm3/g, volume mesopori 0,9282 cm3/g, dan diameter pori rata-rata 3,7353 nm. Sampel 120°C selama 48 jam memberikan volume mesopori sebesar 0,9676 cm3/g dan diameter pori 4,4261 nm, sedangkan kondisi 150 °C selama 12 jam menghasilkan luas permukaan 801,60 m2/g, volume pori total 1,0330 cm3/g, dan diameter pori 5,1540 nm. Citra TEM memperlihatkan kanal periodik berbentuk garis sejajar dan pola menyerupai sarang lebah, yang mendukung terbentuknya struktur MCM-41.
Impregnasi nikel menghasilkan fase NiO yang ditunjukkan oleh refleksi pada 2θ sekitar 37°, 43°, dan 63°. Spektrum XPS menunjukkan bahwa nikel pada material terkalsinasi terutama berada sebagai Ni2+, termasuk spesies NiO dan Ni yang berinteraksi dengan silika. Ni/MCM-41 memiliki luas permukaan 501,30 m2/g dan volume pori 0,52775 cm3/g, sehingga mesoporositas masih dipertahankan meskipun sebagian pori tertutup oleh spesies nikel. HRTEM menunjukkan jarak periodik antarkanal sekitar 4,12 nm, sedangkan pemetaan STEM-EDS memperlihatkan distribusi Ni yang luas pada matriks silika dengan beberapa pengayaan lokal. Pembentukan granul menurunkan luas permukaan dan volume pori secara signifikan. Granul Ni/MCM-41 yang diperoleh melalui pencampuran langsung katalis dengan alginat hanya memiliki luas permukaan 2,8956 m2/g dan volume pori 0,007687 cm3/g. Sebaliknya, granul MCM-41/Ni yang dibentuk terlebih dahulu sebelum impregnasi nikel menghasilkan luas permukaan 24,5978 m2/g dan volume pori 0,145581 cm3/g. Uji metanasi CO2 menggunakan granul Ni/MCM-41 dan MCM-41/Ni pada suhu 300°C dan tekanan 140 kPa menghasilkan konversi CO2 sebesar 7 dan 10%. Katalis tersebut menunjukkan selektivitas terhadap CH4 dan CO masing-masing sebesar 22 dan 43% dan 57 dan 38%.
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Geothermal sludge is a solid waste with considerable potential as a silica source for producing mesoporous materials and catalyst supports. This study aimed to purify silica from geothermal sludge, synthesize MCM-41 under various hydrothermal conditions, incorporate nickel into MCM-41, and evaluate the effect of the impregnation–granulation sequence on the characteristics of granular catalysts. Geothermal sludge was purified through magnetic separation followed by acid leaching. MCM-41 was synthesized using cetyltrimethylammonium bromide (CTAB) as the structure-directing agent at hydrothermal temperatures of 100, 120, and 150 °C for 12, 24, and 48 h. Nickel was introduced using the impregnation method at loadings of 5, 10, and 15 wt.%. Granules were prepared using 4% sodium alginate as the cross-linking agent through two different preparation sequences: granulation of Ni/MCM-41 powder and nickel impregnation after the formation of MCM-41 granules. The combination of magnetic separation and acid leaching increased the SiO₂ content to 95.2 wt.% and decreased the Fe2O3 content from 9.82 to 2.60 wt.% without altering the amorphous nature of the silica. Low-angle XRD patterns of the synthesized MCM-41 exhibited the (100), (110), and (200) reflections, confirming the formation of a two-dimensional hexagonal mesopore arrangement. The sample synthesized at 100 °C for 24 h exhibited the highest BET surface area of 1,037.91 m2/g, with a total pore volume of 0.9337 cm3/g, a mesopore volume of 0.9282 cm3/g, and an average pore diameter of 3.7353 nm. The sample synthesized at 120 °C for 48 h exhibited a mesopore volume of 0.9676 cm3/g and a pore diameter of 4.4261 nm, whereas the sample synthesized at 150 °C for 12 h showed a surface area of 801.60 m2/g, a total pore volume of 1.0330 cm3/g, and a pore diameter of 5.1540 nm. TEM images revealed periodic channels appearing as parallel fringes and honeycomb-like arrangements, further confirming the formation of the MCM-41 structure.
Nickel impregnation produced a NiO phase, as indicated by reflections at 2θ values of approximately 37°, 43°, and 63°. XPS analysis showed that nickel in the calcined material was predominantly present as Ni2+, including NiO species and nickel species strongly interacting with the silica support. The Ni/MCM-41 catalyst retained a BET surface area of 501.30 m2/g and a total pore volume of 0.52775 cm3/g, indicating that the mesoporous structure remained accessible despite partial pore occupation by nickel species. HRTEM analysis showed an interchannel periodic distance of approximately 4.12 nm, while STEM-EDS elemental mapping revealed a broad distribution of nickel throughout the silica matrix, although several regions of local nickel enrichment were also observed. Granulation substantially decreased the surface area and pore volume of the catalysts. Ni/MCM-41 granules prepared by directly mixing the catalyst powder with sodium alginate exhibited a surface area of only 2.8956 m2/g and a total pore volume of 0.007687 cm3/g. In contrast, MCM-41/Ni granules prepared by forming the MCM-41 granules before nickel impregnation exhibited a surface area of 24.5978 m2/g and a total pore volume of 0.145581 cm3/g. CO2 methanation tests using Ni/MCM-41 and MCM-41/Ni granules at 300 °C and 140 kPa resulted in CO2 conversions of 7% and 10%, respectively. The Ni/MCM-41 granules exhibited CH4 and CO selectivity of 22% and 43%, respectively, whereas the MCM-41/Ni granules achieved corresponding selectivity of 57% and 38%.
| Item Type: | Thesis (Doctoral) |
|---|---|
| Uncontrolled Keywords: | lumpur geotermal; metanasi CO2; katalis berbasis Nikel; granulasi,geothermal sludge; CO2 methanation; Nickel-based catalyst; granulation |
| Subjects: | Q Science > QD Chemistry > QD471 Chemical compounds - Structure and formulas Q Science > QD Chemistry > QD501 Catalysis. Catalysts. |
| Divisions: | Faculty of Science and Data Analytics (SCIENTICS) > Chemistry > 47001-(S3) PhD Thesis |
| Depositing User: | Ade Irma Rozafia |
| Date Deposited: | 05 Aug 2026 05:45 |
| Last Modified: | 05 Aug 2026 05:45 |
| URI: | http://repository.its.ac.id/id/eprint/144055 |
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