Synthesis and characterization of pure phase zeolite 4A from coal fly ash
Synthesis and characterization of pure phase zeolite 4A from coal fly ash
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DOI：
10.1016/j.jclepro.2019.02.066
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发表时间：
2019-05-10
影响因子：
11.1
通讯作者：
Munir, Shahid
中科院分区：
文献类型：
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作者：
Iqbal, Asifa;Sattar, Hamed;Munir, Shahid
本研究旨在从巴基斯坦旁遮普省Nishat电厂的粉煤灰合成纯相4A沸石。粉煤灰（FA）的分析表明，由于其Si/Al摩尔比接近2，其可用于生产低硅酸盐型沸石，特别是沸石4A。目前的研究强调的诱导时间（之前和之后的结晶）的粉煤灰提取物的Si-Al-Na物种，从粉煤灰中提取。诱导时间有助于在合成过程中催化初级和次级凝胶形成，导致具有高结晶度和小晶粒尺寸的单相的受控形成。通过使用各种分析技术对合成的4A沸石进行物理化学研究，与商业4A沸石进行比较，证明了所提出的工艺是合理的。X射线衍射（XRD）分析证实合成的4A沸石只有一个晶相，并且与具有75%结晶度的参比沸石相比具有82%结晶度的小晶粒尺寸。傅里叶变换红外光谱（FTIR）光谱通过表明存在具有相同峰高和峰宽的相同结构单元，揭示了合成沸石和参比沸石的结构方面。通过扫描电子显微镜（SEM）的形态分析表明，合成沸石晶体具有明确的立方形状。通过Brunauer-Emmett-Teller（BET）的表面积分析表明，合成的沸石具有122 m2/g的表面积，比36.3m2/g的参比沸石高3倍。还发现合成的沸石具有比参比沸石更小的粒度。通过从25至800 ℃温度的非等温热重分析-差热分析（TGA-DTA）热谱图研究了两种沸石的热稳定性比较，发现两种样品在800 ℃下是稳定的。(C)2019爱思唯尔有限公司版权所有。
This study was aimed at the synthesis of pure phase zeolite 4A from coal fly ash sourced from Nishat power plant in the Punjab province of Pakistan. Analysis of fly ash (FA) demonstrated that it can be used to produce low silicate type zeolites specifically zeolite 4A due to its Si/Al molar ratio of similar to 2. The current investigation emphasized on the addition of induction time (before and after crystallization) to the fly ash extract of Si-Al-Na species that was extracted from fly ash. The induction time helped in catalysing primary and secondary gel formation during the synthesis leading to controlled formation of single phase with high crystallinity and small crystallite size. The physiochemical investigations of synthetic zeolite 4A by using various analytical techniques made the proposed process justified on comparison with commercial zeolite 4A. The X-Ray Diffraction (XRD) analysis for synthesize zeolite 4A confirmed only one crystallographic phase and small crystallite size with 82% crystallinity compared to reference zeolite with 75% crystallinity. Fourier-Transform Infrared spectroscopy (FTIR) spectra revealed the structural aspects of synthesis and reference zeolite by indicating the presence of identical structural units with same height and width of peaks. Morphological analysis by Scanning Electron Microscope (SEM) showed a well-defined cubic shape of synthesis zeolitic crystals. Surface area analyses by Brunauer -Emmett-Teller (BET) showed that synthesized zeolite possessed 122 m(2)/g surface area that is 3 times higher than reference zeolite of 36.3 m(2)/g. The synthesized zeolite was also found to have smaller particle size than reference zeolite. Thermal stability comparison of both zeolites was studied by nonisothermal Thermo Gravimetric Analysis-Differential Thermal Analysis (TGA-DTA) thermograms from 25 to 800 degrees C temperature and both the samples were found to be stable at 800 degrees C. (C) 2019 Elsevier Ltd. All rights reserved.