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Nano sodalite as solid base catalyst for knoevenagel condensation reaction

机译:纳米方钠石为knoevenagel缩合反应的固体基础催化剂

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摘要

Sodalite is a type of zeolite with ultramicroporesize and has high thermal stability. Sodalite with nanosized particle with increased in external surface area offers great attractive possibilities to explore their potential utilization. In this study, nanosized sodalite with low Si/Al ratio was synthesized and used as base catalyst in Knoevenagel condensation reaction. The synthesis was performed using fumed silica in the alkali medium with molar ratio of 19Na2O:4SiO2:1Al2O3:190H2O at various temperature and time of crystallization. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Field emission scanning electron microscopy (FESEM). Results showed that, pure nanosodalite crystals with average crystal size of 40 to 80 nm have been successfully been synthesized during 5 hours of heating at 60 °C under static condition. Pure microsized sodalite was obtained when the synthesis temperature was increased to 90 °C. Basicity measurement using CO2 as probe molecule and monitored by FTIR revealed the presence of basic site with the appearance of vibration band at 1430 cm- 1. The catalytic activities of the nano and micro-sodalite were evaluated for base catalyzed reactions via Knoevenagel condensation between benzaldehyde and malononitrile producing benzylidenemalononitrile as the only product. The results showed that both nano- and micro-sodalite catalysts were active for the reaction where the conversion of benzaldehyde for the nanosodalite(S8) and microsodalite (S15) was 92.% and 88.7%, respectively. Based on the GC analysis, all the catalyst are found to give 100 % of product selectivity to the main product benzylidenemalononitrile.
机译:方钠石是一种具有超微孔尺寸的沸石,具有很高的热稳定性。具有增加外表面积的纳米级颗粒的方钠石提供了探索其潜在利用的巨大诱人可能性。本研究合成了低Si / Al比的纳米方钠石,并用作Knoevenagel缩合反应的基础催化剂。使用气相法二氧化硅在碱性介质中进行合成,合成温度和时间分别为19Na2O:4SiO2:1Al2O3:190H2O。通过X射线衍射(XRD),傅立叶变换红外光谱(FTIR)和场发射扫描电子显微镜(FESEM)对样品进行表征。结果表明,在静态条件下于60°C加热5小时,已成功合成了平均晶体大小为40至80 nm的纯纳米苏打石晶体。当合成温度提高到90°C时,获得纯的超细方钠石。使用CO2作为探针分子进行碱性测量并通过FTIR监测,发现存在碱性位点,并在1430 cm-1处出现了振动带。通过苯甲醛之间的Knoevenagel缩合,评估了纳米苏打石和微苏打石的催化活性。丙二腈是唯一的产品,可生产亚苄基丙二腈。结果表明,纳米苏打石和微苏打石催化剂对反应均具有活性,其中苯甲醛对纳米苏打石(S8)和微苏打石(S15)的转化率分别为92.%和88.7%。根据GC分析,发现所有催化剂对主要产物亚苄基丙二腈的产物选择性为100%。

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    Teow Bee Khuan;

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  • 年度 2010
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  • 原文格式 PDF
  • 正文语种 en
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