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

Öz

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.

Anahtar Kelimeler

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

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

Öz

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.

Anahtar Kelimeler

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

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