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İZOBÜTAN DEHİDROJENASYONU İÇİN Ca-Cr-MCM-41 KATALİZÖRLERİNİN SENTEZİ VE KARAKTERİZASYONU

SYNHTHESIS AND CHARACTERIZATION OF Ca-Cr-MCM-41 CATALYSTS FOR ISOBUTANE DEHYDROGENATION

Journal Name:

  • Gazi Üniversitesi Mühendislik-Mimarlık Fakültesi Dergisi

Publication Year:

  • 2014

Key Words:

Keywords (Original Language):

Author NameUniversity of Author
Abstract (2. Language): 
In this study, the effects of Ca addition to Cr-MCM-41 catalysts on chromate species distribution over the catalyst and the catalyst activity were investigated. Firstly, catalysts were synthesized by impregnation method using different calcium sources (CaCO3, CaCl2, Ca(NO3)2). Monochromates, were known as the most active chromate species for isobutane dehydrogenation, were determined on the synthesized catalysts using CaCO3 salt so this salt was used in the forward studies. After Ca impregnation, a slight increase was observed in the amount of mono- and dichromate located in the structure of the catalysts synthesized by hydrothermal method. It was indicated that monochromate species absent before formed after Ca addition on the catalysts synthesized with impregnation technique. It was shown that in the case of Ca/Cr ratio as 0.65 in the studies conducted at different Ca/Cr (mass/mass) ratios, the peak (380nm) showing O-Cr (VI) bond in monochromate was more intense than the other catalysts from the DR-UV-vis analyzes. As regards the catalyst surface composition was examined, the highest Cr/Si ratio was also determined in that catalyst. The catalytic test studies of the synthesized catalysts according to impregnating and hydrothermal synthesis methods at a Ca/Cr ratio of 0.65 were performed at 873K temperature and at atmospheric pressure. The catalysts become privileged position in terms of isobutene selectivity, because of the products of side reactions were not observed in these tests. Although a significant
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Abstract (Original Language): 
Yürütülen çalışmada, Cr-MCM-41 katalizörlerine Ca eklenmesinin, katalizör üzerindeki kromat türlerinin dağılımına ve katalizör aktifliğine etkileri araştırılmıştır. Çalışmada öncelikle farklı kalsiyum kaynakları (CaCO3, CaCl2, Ca(NO3)2) kullanılarak emdirme yöntemi ile katalizörler sentezlenmiştir. İzobütan dehidrojenasyonunda en aktif kromat türü olarak bilinen monokromatlar, CaCO3 tuzu kullanılarak sentezlenen katalizörde belirlendiğinden çalışmanın ilerleyen bölümlerinde CaCO3 tuzu kullanılmıştır. Hidrotermal yöntemle sentezlenen katalizörlerde Ca emdirilmeden önce yapıda bulunan mono- ve di- kromat miktarlarında azda olsa bir artış gözlenmiştir. Emdirme tekniği ile sentezlenen katalizörlerde ise yapıda olmayan monokromat türlerinin Ca eklemeden sonra yapıda oluştuğu tespit edilmiştir. Farklı Ca/Cr (kütle/kütle) oranlarında yürütülen çalışmalarda Ca/Cr oranının 0,65 olduğu durumda, monokromatlar içindeki O-Cr(VI) bağlarını gösteren pikin (380 nm) diğer katalizörlere göre daha şiddetli olduğu DR-UV-vis analizlerinden görülmüştür. Katalizör yüzey bileşimleri incelendiğinde en yüksek Cr/Si oranı yine bu katalizörde belirlenmiştir. Ca/Cr oranı 0,65 olacak şekilde emdirme ve hidrotermal sentez yöntemlerine göre sentezlenen katalizörlerin katalitik test çalışmaları 873K sıcaklık ve atmosferik basınçta gerçekleştirilmiştir. Bu testlerde yan reaksiyon ürünlerinin gözlenmemesi, katalizörleri izobüten seçiciliği yönünden ayrıcalıklı konuma getirmiştir. Emdirme ile sentezlenmiş katalizör yüzey alanında (Cr-MCM-41-EM) Ca ilavesi ile önemli bir azalış olmasına rağmen izobütan dönüşüm değerlerinin korunması, yapıda oluşan aktif monokromat türleri ile açıklanmıştır.
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