SCR Uygulamaları için Oksalik Asit İşlemi ile Kordiyerit Yapının Yüzey Alanının İyileştirilmesi

Kordiyerit (2Al2O3-5SiO2-2MgO) seçici katalitik indirgeyici (SCR) uygulamalarında katalitik nanopartiküllerin egzoz borusu üzerinde konumlandırılmasını sağlayan ana taşıyıcı yapıdır. Bu yapıya daha fazla katalitik nanopartikül yüklenebilmesi için asit işlemi ile modifiye edilmesi gerekmektedir. Çalışmamızda bu yapılar 2 ve 4 saatlik sürelerde farklı oksalik asit oranları ile muamele edilmiştir. Asitle muamele edilmiş kordiyerit yapıların yüzey alanları Brunauer, Emmet ve Teller (BET) analizi ile ölçülmüş ve taramalı elektron mikroskobu-enerji dağılımlı X-ışını spektroskopisi (SEM-EDS) analizi ile morfolojik olarak incelenmiştir. BET analiz sonucuna göre bu yapıların yüzey alanı ölçümleri 163,601 m2/g’a ulaşmıştır. Elde edilen bu değer, işlem görmemiş kordiyeritin yüzey alanından yaklaşık 327 kat daha fazladır. SEM analizi sonucunda bu yapıların yüzeyindeki alüminyum (Al) ve magnezyum (Mg) elementlerinin yüzdesi azalırken, silikonun (Si) yüzdesi artmıştır. Yüksek yüzey alanının nedeni, kordiyerit yüzeyinden Al ve Mg iyonlarının uzaklaştırılması nedeniyle saf amorf silikanın oluşmasıdır. Böylece, kordiyerit yüzeyi üzerinde katalitik nanoparçacıkların daha fazla kaplanmasına izin verilebilir. Bu çalışmanın sonucunda çözeltinin asit miktarının ve asitle muamele süresinin kordiyerit yüzey alanını arttırdığı söylenebilir.

Anahtar Kelimeler:

Kordiyerit, Oksalik asit, Kimyasal aşındırma işlemi, BET, SEM

Enhancement of Surface Area of Cordierite Structure by Oxalic Acid Treatment for SCR Applications

Cordierite (2Al2O3-5SiO2-2MgO) is the main carrier structure that enables the positioning of catalytic nanoparticles on the exhaust pipe in the selective catalytic reduction (SCR) applications. In order to be loaded more catalytic nanoparticles into this structure, it must be modified by acid treatment. In our study, these structures were treated with the different oxalic acid ratios for 2 and 4 hours. Brunauer, Emmet and Teller (BET) analysis were employed to measure the surface areas of acid-treated cordierite structures and scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS) analysis was used to examine morphological structures of them. In consideration of BET analysis result, the surface area measurements of these structures reached up to 163.601 m2/g. The obtained value was about 327 times greater than the surface area of no treatment cordierite. In result of the SEM analysis, while the percentage of aluminum (Al) and magnesium (Mg) elements on the surface of these structures decreased, that of silicon (Si) increased. The reason of the high surface area is the formation of the pure amorphous silica due to the removal of Al and Mg ions from the surface of the cordierite. Thus, further coating of the catalytic nanoparticles on the cordierite surface could be allowed. As a result of this study, it could be said that the acid amount of the solution and the acid treatment duration enhances the surface area of the cordierite.

Keywords:

Cordierite, Oxalic acid, Chemical etching process, BET, SEM,

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