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Subject: search.filters.subject.Zeolite X

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    Higher alcohol production from ethanol over occluded [Mg4(OH)4]4+ clusters in MgO/KNaX
    (2022-02-25)
    Yotkkham, Nattapol
    ;
    Choojun, Kittisak
    ;
    Promchana, Pratya
    ;
    Fan, Xiaolei
    ;
    Sooknoi, Tawan
    Conversion of ethanol to higher alcohols was studied over MgO/KNaX, prepared by ion exchange with Mg(OAc)<inf>2</inf>, followed by KOH washing. The catalysts were characterized by XRF, XRD, SEM, BET, <sup>27</sup>Al MAS NMR, EXAFS, NH<inf>3</inf>- and CO<inf>2</inf>-TPD. All catalysts showing MgO nanopetals and aggregates on the external surface, contained occluded [Mg<inf>4</inf>(OH)<inf>4</inf>]<sup>4+</sup> clusters in the zeolite cavities, providing medium basic (M<inf>b</inf>) and acid (M<inf>a</inf>) sites. Ethanol conversion and higher alcohols selectivity (up to 78%) increased with M<inf>b</inf>/M<inf>a</inf> ratio due to the increase in both MgO (4–6 wt%) and K (14.7–17.3 wt%) loadings. Decreasing occluded [Mg<inf>4</inf>(OH)<inf>4</inf>]<sup>4+</sup> clusters and/or increasing MgO aggregates led to the lower conversion and yields of higher alcohols. The essential role of the occluded [Mg<inf>4</inf>(OH)<inf>4</inf>]<sup>4+</sup> clusters in producing higher alcohols was verified by the reactions using various control catalysts. The MgO/KNaX showed high stability even after steaming at 380 °C, as well as being regenerated by calcination (450 °C in air).
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    Synthesis of zeolite x from bentonite via hydrothermal method
    (2020-01-01)
    Srilai, Suphada
    ;
    Tanwongwan, Worapak
    ;
    Onpecth, Kobchai
    ;
    Wongkitikun, Thanapat
    ;
    Panpiemrasda, Kollayut
    Zeolite X were successfully synthesized from bentonite from Lopburi province, in Thailand using the two-step of hydrothermal method under optimum condition without calcination. The first step of hydrothermal were obtained at 200 ℃ for 3 h to remove unreacted impurity minerals such as quartz and muscovite. The secondary step of hydrothermal were obtained at 90 ℃ for 120 h for synthesis of zeolite X. The characterization of zeolite X were examined by x-ray diffraction (XRD), scanning electron microscopy (SEM), and infrared spectroscopy (FT-IR), respectively. The crystal structure of product was determined as zeolite X by XRD. The morphology of SEM images for zeolite X is octahedral shape. FTIR spectra are in accordance with the other characterization results.
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    Influence of crystallization time for synthesis of zeolite a and zeolite x from natural kaolin
    (2019-01-01)
    Srilai, Suphada
    ;
    Tanwongwan, Worapak
    ;
    Onpecth, Kobchai
    ;
    Wongkitikun, Thanapat
    ;
    Panomsuwan, Gasidit
    Zeolite A and zeolite X were successfully synthesized from natural kaolin from Lampang province using calcination and a two-step hydrothermal method. First, metakaolin was obtained by calcining the kaolin at 700 °C for 2 h. Hydrothermal experiments can be separated into two types, being high temperature and short time or lower temperature long time. For high temperature hydrothermal treatment, metakaolin was mixed with NaOH to form hydrous sodium aluminosilicate. This was dissolved in dilute HCl. After filtration, the pH was adjusted with deionized water to pH = 7. This formed an amorphous aluminosilicate gel. For low temperature and longtime hydrothermal treatment aluminosilicate gel was mixed with NaOH to form zeolite A and zeolite X. The optimum condition for the first step in the synthesis of zeolite A is high temperature and short time of hydrothermal treatment with NaOH 8 M at 200 °C for 3 hours. This is followed by low temperature and longtime of hydrothermal treatment with NaOH 1 M carried out at 90 °C for 72 hours. The optimum conditions for the first step of synthesis of zeolite X is the high temperature, short time hydrothermal treatment with NaOH 8 M at 200 °C for 3 hours and low temperature, longtime hydrothermal treatment with NaOH 1 M at 90 °C for 120 hours. The characterizations of zeolite A and zeolite X were carried out by x-ray diffraction (XRD), scanning electron microscopy (SEM), and infrared spectroscopy (FT-IR).