Characterization of Zeolites by XRD, SEM, FTIR Analysis and BET Method and Determination of Surface Acidic Properties of Thermal Treated Zeolites

Abstract

The surface characteristics of the zeolites need to be known for their effective use especially, as ion exchanger, catalyst, and adsorbent. In this study, the morphological, mineralogical and surface properties of zeolites were investigated by some instrumental analyses such as X-ray diffraction pattern (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) methods. FTIR spectra proved the presence of silanol and bridged hydroxyls on the zeolite surface. The pore properties including surface area, pore volume, pore size distribution, and average pore diameter of the zeolites were determined by N2 adsorption at 77 K using the BET t-plot and density functional theory (DFT) methods. The pore size distribution showed that the zeolites include both micro and mesopores. The specific surface area of zeolites with different SiO2/Al2O3 ratios decreased as the Si/Al ratio increased. XRD Method was used to examine the crystal structures of zeolites and SEM was used to examine the particle structures. Surface acidity of heat activated zeolites was determined using two different methods. Information about the total amount of acid sites on the zeolites was provided by the n-Butylamine titration method. and FTIR spectra provided information about surface acidity.

Keywords

• Zeolites
• Instrumental characterization
• DRIFT Spectroscopy
• Bronsted and Lewis acidity
• Si/Al ratio

XRD, SEM, FTIR Analizleri ve BET Yöntemiyle Zeolitlerin Karakterizasyonu ve Isıl İşlem Görmüş Zeolitlerin Yüzey Asidik Özelliklerinin Belirlenmesi

Abstract

Zeolitlerin özellikle iyon değiştirici, katalizör ve adsorban olarak etkin kullanımları için yüzey özelliklerinin bilinmesi gerekmektedir. Bu çalışmada zeolitlerin morfolojik, mineralojik ve yüzey özellikleri, X-ışını kırınım deseni (XRD), Taramalı Elektron Mikroskobu (SEM), Fourier Dönüşümlü Kızılötesi Spektroskopisi (FTIR) ve Brunauer-Emmett-Teller (BET) yöntemlerinin birlikte kullanıldığı enstrümantal analiz teknikleriyle incelenmiştir. FTIR spektrumlarından, zeolit yüzeylerinde silanol ve hidroksil köprülerinin varlığı kanıtlanmıştır. Zeolitlerin yüzey alanı, gözenek hacmi, gözenek boyut dağılımı ve ortalama gözenek çapı dâhil gözenek özellikleri, BET t-plot ve yoğunluk fonksiyonel teorisi (DFT) yöntemleri kullanılarak 77 K'de N2 adsorpsiyonu ile belirlenmiştir. Gözenek boyut dağılımı, zeolitlerin hem mikro hem de mezo gözenekler içerdiğini göstermiştir. Farklı SiO2/Al2O3 oranlarına sahip zeolitlerin, Si/Al oranı arttıkça özgül yüzey alanında azalma gözlenmiştir. Isıl aktivasyona uğratılmış zeolitlerin yüzey asitlikleri farklı iki yöntem kullanılarak belirlenmiştir. n-Bütilamin titrasyon yöntemiyle zeolitler üzerindeki asit bölgelerinin toplam miktarı ve FTIR spektrumlarından, yüzey asitlikleri hakkında bilgi sağlanmıştır.

Keywords

• Zeolitler
• Enstrümantal karakterizasyon
• DRIFT Spektroskopisi
• Bronsted ve Lewis asitliği
• Si/Al oranı

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