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不同类型沸石分子筛的OH振动红外光谱研究
FT-IR Study on the OH Vibration of Different Zeolite Catalysts
【作者】 王清;
【导师】 郭洪臣;
【作者基本信息】 大连理工大学 , 工业催化, 2011, 硕士
【摘要】 本文采用傅里叶变换红外光谱法对不同类型沸石分子筛骨架结构和羟基振动进行了系统研究,着重表征了TS-1的表面硅羟基,并在此基础上研究了样品片厚度、摄谱部位和不同合成批次对TS-1羟基谱图的影响;还研究了晶化时间、硅钛比、碳酸铵加入量、溶剂、氮气气氛保护等不同合成条件对TS-1催化剂羟基振动的影响;另外还研究了水蒸气钝化和高温焙烧对廉价法TS-1骨架结构和羟基分布的影响。得到以下结论:1.不同类型沸石分子筛的骨架结构、羟基振动及羟基酸性有明显的差异。2.TS-1样品量为10.0 mg时制得的样品片厚度比较合适,可得到较好的羟基谱图;样品厚度均匀时,同一合成条件下的样品不同摄谱部位均可得到唯一的羟基谱图。3.廉价法TS-1催化剂表面羟基比较复杂,主要包括表面孤立的硅羟基,孔道内偕生的硅羟基,孔道内末端硅羟基和受氢键干扰的硅羟基;晶化时间为36 h时,廉价法TS-1已经成型,延长晶化时间,骨架结构和硅羟基没有明显变化。4.廉价法TS-1样品的Si/Ti摩尔比从40增加到180的过程中,孔道内末端硅羟基略有减少,内外表面受氢键干扰的硅羟基明显增加;Si/Ti摩尔比从180继续增加到270,对各类羟基没有明显影响,但是硅溶胶中铝、钠杂质含量增加,表面内偕生硅羟基增强,受氢键干扰吸收峰向低波数位移。5.合成过程中随着碳酸铵加入量增加,经典法TS-1外表面孤立硅羟基减少,受氢键干扰的峰向低波数位移;廉价法TS-1孔道内偕生和末端硅羟基逐渐增加,受氢键干扰的硅羟基逐渐减少,(NH4)2CO3/Si摩尔比为1.0后,继续增加,廉价法TS-1羟基吸收峰强度整体下降。6.合成过程中乙酰丙酮加入量和氮气气氛保护使廉价法TS-1样品内外表面受氢键干扰的硅羟基增加,乙酰丙酮加入量还能使其外表面孤立硅羟基增加。7.水蒸气钝化和高温焙烧处理可以改变廉价法TS-1的羟基分布。
【Abstract】 The framework and hydroxyl vibration of different zeolites were summarized by FT-IR in this paper. At the same time, not only the thickness, position and the synthetic batch of TS-1 sample, but also the difference of hydroxyl groups of TS-1 under different synthesis conditions, such as the crystallization time, the molal ratio of silicon to titanium, the content of ammonium carbonate, the solvent of acetyl acetone and nitrogen protection were investigated. Furthermore, the effect of steaming and calcination on the framework structure and hydroxyl groups of low-cost TS-1 catalysts was investigated. The obtained results demonstrated as follows:1. The framework vibration、hydroxyl vibration and acidity of hydroxyl of different forms of zeolites have obvious differences.2. The thickness of TS-1 sample is quite appropriate to obtain preferable spectrogram in OH vibration region when the weight of TS-1 is 10.0 mg. The unique spectrogram could be acquired even if in different part of sample with same thickness and synthesis conditions.3. The low-cost TS-1 catalysts have complicated hydroxyl groups which include isolated hydroxyl groups, geminal hydroxyl groups, terminal hydroxyl groups and hydrogen-bonded hydroxyl groups. After 36 h crystallization, the framework of low-cost TS-1 are formed completely, the framework structure and hydroxyl groups are no longer change as the crystallization time extension.4. Terminal hydroxyl groups decrease while hydrogen-bonded hydroxyl groups increase with the molar ratio of silicon to titanium increasing from 40 to 180 for low-cost TS-1. When the molar ratio of silicon to titanium increasing from 180 to 270, hydroxyl groups don’t change obviously. However, with the increase of aluminum and sodium content, geminal hydroxyl groups increase and the peak which is attributed to hydrogen-bonded hydroxyl groups shift to the lower wave number.5. With the increase of ammonium carbonate content, the peak which is attributed to isolated hydroxyl groups become weaker and the peak which is attributed to hydrogen-bonded hydroxyl groups shift to the lower wave number for classical TS-1. While the geminal hydroxyl groups and terminal hydroxyl groups increase and hydrogen-bonded hydroxyl groups decrease for low-cost TS-1. After the molar ratio of ammonium carbonate to silicon come up to 1.0, with the increase of (NH4)2CO3/Si, the hydroxyl groups of low-cost TS-1 get lessen. 6. Hydrogen-bonded hydroxyl groups increase with the acetyl acetone increase and nitrogen protection while low-cost TS-1 was synthesized. Isolated hydroxyl groups also increase with the acetyl acetone increase.7. The hydroxyl groups of low-cost TS-1 catalysts could be changed by high temperature steam passivation and calcinations.
【Key words】 TS-1 Catalyst; FT-IR; Hydroxyl Group; Framework; Synthesis conditions;