Si, Mn ve Cu ELEMENTLERİNİN PROMOTÖR OLARAK DEMİR BAZLI FİSCHER-TROPSCH KATALİZÖRÜNE VE REAKSİYONUNA ETKİSİ

Abstract

Fischer–Tropsch (FT) sentezi, sentez gazından (CO + H₂) sıvı hidrokarbonlar üretimini sağlayan ve sürdürülebilir enerji sistemleri açısından büyük öneme sahip bir katalitik süreçtir. Bu reaksiyonda kullanılan katalizörlerin yapısal ve kimyasal özellikleri, reaksiyon verimliliği ve ürün seçiciliğini doğrudan etkilemektedir. Özellikle demir bazlı katalizörler, düşük maliyetleri, yüksek CO dönüşüm oranları ve faz esnekliği sayesinde öne çıkmakta; ancak indirgenebilirlik, kararlılık ve istenmeyen metan oluşumu gibi sınırlayıcı etkilere sahiptir. Bu çalışmada, söz konusu sorunların giderilmesi ve katalizör performansının iyileştirilmesi amacıyla silisyum (Si), mangan (Mn) ve bakır (Cu) promotörlerinin demir tabanlı FT katalizörlerinin kimyasal ve fiziksel özellikleri, indirgenme davranışları ve katalitik performansları üzerindeki etkileri araştırılmıştır. Demir esaslı FT katalizörleri bazik ortamda çöktürme yöntemiyle sentezlenmiş; elde edilen numuneler yüzey alanı (BET), X-ışını toz difraktometrisi (XRD), sıcaklık programlı indirgeme (TPR), infrared spektroskopisi (IR) ve taramalı elektron mikroskobu (SEM) analizleriyle karakterize edilmiştir. Bulgulara göre, Si ilavesi katalizörün yüzey alanını önemli ölçüde artırmakta; ancak kalsinasyon sonrasında kristal faz oluşumunu engelleyerek indirgenebilirliği düşük amorf bir yapı meydana getirmektedir. Mn katkısı yüzey alanında belirgin bir değişime neden olmamakla birlikte katalitik aktiviteyi anlamlı düzeyde artırmakta; ıslak emdirme yöntemiyle eklenen Cu promotörü ise indirgenebilirliği artırarak metal faz oluşumunu kolaylaştırmaktadır. Ayrıca potasyum (K) elementi, FT reaksiyonlarında metan oluşumunu bastırmak amacıyla yaygın olarak kullanılmakta olup, bu çalışmada da metan üretimini azaltmak için tüm sentezlenen katalizörlerde sabit miktarda potasyum içeriği korunmuştur.

Keywords

• Fischer-Tropsch
• katalizör
• promotör
• yüzey alanı (BET)

EFFECT OF Si, Mn and Cu AS PROMOTER ON IRON BASED FISCHER-TROPSCH CATALYST AND REACTION

Abstract

The Fischer–Tropsch (FT) synthesis is a catalytic process that enables the conversion of synthesis gas (CO + H₂) into liquid hydrocarbons and holds great significance for sustainable energy systems. The structural and chemical properties of the catalysts used in this reaction directly influence reaction efficiency and product selectivity. In particular, iron-based catalysts stand out due to their low cost, high CO conversion rates, and flexible phase behavior; however, issues such as reducibility, stability, and undesired methane formation can limit their performance. In this study, to address these challenges and enhance catalytic performance, the effects of silicon (Si), manganese (Mn), and copper (Cu) promoters on the chemical and physical properties, reduction behavior, and catalytic performance of iron-based FT catalysts were investigated. The iron catalysts were synthesized under basic conditions using the precipitation method, and the resulting samples were characterized by Brunauer–Emmett–Teller (BET) surface area analysis, X-ray diffraction (XRD), temperature-programmed reduction (TPR), infrared spectroscopy (IR), and scanning electron microscopy (SEM). The results revealed that the addition of Si significantly increases the catalyst surface area but, after calcination, inhibits the formation of crystalline phases, leading to a less reducible amorphous structure. The addition of Mn does not cause a significant change in surface area but notably enhances catalytic activity, while Cu, introduced via the wet impregnation method, promotes the reduction process and facilitates the formation of metallic phases. Additionally, potassium (K) is commonly used in FT reactions to suppress methane formation, and in this study, a constant amount of potassium was included in all synthesized catalysts to minimize methane production.

Keywords

• Fischer-Tropsch
• catalyst
• promotor
• surface area (BET)

References

1. 1. Steynberg AP, Dry M. Studies in Surface Science And Catalysis. Elsevier Science & Technology Books; 2004.
2. 2. Gül ÖF. Biyokütle ve Kömür Karışımlarından Sıvı Yakıt Üretimi. 2. In: Ulusal Enerji Verimliliği Formu. 2011:1-29.
3. 3. Âmin M, Usman M, Kella T, Khan WU, Khan IA, Lee KH. Issues and challenges of Fischer–Tropsch synthesis catalysts. Front Chem. 2024;12, Article 1462503.
4. 4. Quek XY, Pestman R, Santen RA, Hensen EJM. Structure sensitivity in the ruthenium nanoparticle catalyzed aqueous-phase Fischer–Tropsch reaction. Catal Sci Technol. 2014;4:3510-3523.
5. 5. Liu Y, Chen JF., Zhang Y. The effect of pore size or iron particle size on the formation of light olefins in Fischer–Tropsch synthesis. RSC Adv. 2015;5:29002-29007.
6. 6. Smit E, Weckhuysen BM. Therenaissance of iron-based Fischer-Tropsch synthesis: on the multifaced catalyst deactivation behaviour. Chem Soc Rev. 2008;37:2758-2781.
7. 7. Tavares M, Westphalen G, Almeida JM, Romano PN, Sousa-Aguiar EF. Modified Fischer-Tropsch synthesis: A review of highly selective catalysts for yielding olefins and higher hydrocarbons. Front Nanotechnol. 2022;4.
8. 8. Rao VUS, Stiegel GJ, Cinquegrane GJ, Srivastava RD. Iron-based catalysts for slurry-phase Fischer-Tropsch process. Techn Rev Fuel Proc Techn. 1992;30:83-107.

9. 9. Suo H, Wang S, Zhang C, et al. Chemical and structural effects of silica in iron-based Fischer–Tropschsynthesis catalysts. J Catal. 2012;286:111-123.
10. 10. Bukur DB, Lang X, Mukesh D, Zimmerman WH, Rosynek MP, Li C. Binder/supporteffects on the activity and selectivity of iron catalysts in the Fischer-Tropsch synthesis. Ind Eng Chem Res. 1990;29.
11. 11. Rao KN, Kumar A, Sekar R. SO2 promoted alkali metal doped Ag/Al2O3 catalysts for lean NOx reduction in the presence of SO2 and water. Appl Catal B Environ. 2012;119-120:36-45.
12. 12. Yohannes A, Gates I. A century of evolution: Progress and milestones in Fischer–Tropsch synthesis. Coord Chem Rev. 2026;547.
13. 13. Li T, Yang Y, Zhang C, et al. Effect of manganese on an iron-based Fischer-Tropsch synthesis catalyst prepared from ferroussulfate. Fuel. 2007;86:921-928.
14. 14. Jiménez-Vázquez A, Jaimes-López R, Morales-Bautista CM, Pérez-Rodríguez S, Gochi-Ponce Y, Estudillo-Wong LA. Catalytic applications of natural iron oxides and hydroxides: A review. Catalysts. Published online 2025.
15. 15. Jaggi NK, Schwartz LH, Butti JB, Papp H, Baerns M. Phase characterization of iron/manganese fischer-tropsch catalysts. Eff Compos Reduct Cond. 1985;13:347-361.
16. 16. Yang Y, Xiang H, Xu Y, Bai L, Li Y. Effect of potassium promoter on precipitated iron-manganese catalyst for Fischer-Tropsch synthesis. Appl Catal Gen. 2004;266:181-194.
17. 17. Butt JB. Carbide phases on iron-based Fischer-Tropsch synthesis catalysts part II: Some reaction studies. Catal Lett. 1990;7:1-4.
18. 18. Wang C, Wang Q, Sun X, Xu L. CO Hydrogenation to Light Alkenes Over Mn/Fe Catalysts Prepared by Co-precipitation and Sol-gel Methods. Catal Lett. 2005;105:93-101.
19. 19. Grzybek T, Papp H, Baerns M. Fe/Mn oxide catalysts for fischer-tropsch synthesis: Part V XPS surface characterization of calcined and reduced samples. Appl Catal. 1987;29:335-350.
20. 20. Anderson RB. The Fischer-Tropsch Synthesis. Academic Press; 1984.
21. 21. Zhang CH, Yang Y, Tenga BT, et al. Study of an iron-manganese Fischer–Tropsch synthesis catalyst promoted with copper. J Catal. 2006;237:405-415.
22. 22. Li SZ, Krishnamoorthy S, Li AW, Meitzner GD, Iglesia E. Promoted iron-based catalysts for the Fischer-Tropsch synthesis: design, synthesis, site densities, and catalytic properties. J Catal. 2002;206:202-217.
23. 23. Maderuelo-Solera R, Cecilia-Buenestado JA, Vila F, Mariscal R, Maireles-Torres PJ, Moreno-Tost R. Synthesis and Catalytic Activity of Cu-Co/CeO2 Catalysts in the Hydrogenation of Furfural to Pentanediols. Catalysts. 2025;15(9):872.
24. 24. Andrade AL, Souza DM, Pereira MC, Fabris JD, Domingues RZ. Synthesis and characterization of magnetic nano particles coated with silica through a sol-gel approach. Cerâmica. 2009;55.
25. 25. Karakassides MA, Gournis D, Petridis D. An infrared reflectance study of Si-O vibrations in thermally treated alkali-saturated montmorillonites. ClayMinerals. 1999;34:429-438.
26. 26. Vempati RK, Loeppert RH, Burghardt RC. Infrared vibrations of hematite formed from aqueus- and dry-thermal incubation of Si-containing ferrihydrite. Clays Clay Miner. 1990;38:294-298.
27. 27. Zhang C, Teng B, Yang Y, et al. Effect of air-exposure on reduction behavior of a Fe-Mn-Cu-K/SiO2 Fischer-Tropsch synthesis catalyst. J Mol Catal Chem. 2005;239:15-21.
28. 28. Maiti GC, Malessa R, Baerns M. Iron/manganeseoxide catalysts for Fischer-Tropsch synthesis-part I: Structural and textural changes by calcination, reduction and synthesis. Appl Catal Gen. 1983;5:151-170.
29. 29. Malessa R, Baerns M. Iron/manganeseoxide catalysts for Fischer-Tropsch synthesis: for Activity and selectivity. Ind Eng Chem Res. 1988;27:279-283.
30. 30. Feyzi M, Jafari F. Study on iron-manganese catalysts for Fischer-Tropsch synthesis. J Fuel Chem Technol. 2012;40:550-557.