TiO2/4A分子筛复合催化剂的制备及其乙醇脱水制乙烯性能

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	TiO2/4A分子筛复合催化剂的制备及其乙醇脱水制乙烯性能
其他题名	Preparation and catalytic dehydration of ethanol to ethylene of TiO2/4A zeolite composite catalysts
	肖妍艳
导师	李新军
	2009-05-31
学位授予单位	中国科学院广州能源研究所
学位授予地点	广州能源研究所
学位名称	硕士
关键词	Tio2/4a分子筛复合催化剂改性控制掺杂乙醇脱水乙烯
摘要	乙烯是化工生产中一种重要的中间产品，目前乙烯的生产主要来源于石油原料的催化裂解。随着石油资源的日益枯竭以及环境问题的凸显，通过可再生能源生物乙醇来制取乙烯将会成为石油乙烯的潜在的补充供应途径。催化剂在乙醇脱水制取乙烯的工业发展中起着重要作用。本文采用液相沉积法、浸渍和液相沉积联合的方法以及镍离子分步控制掺杂工艺分别制备了TiO2/4A分子筛复合催化剂、铈锰铂改性的4A分子筛/TiO2复合催化剂和镍离子非均匀掺杂的TiO2/4A分子筛复合催化剂。利用SEM、XRD、FTIR、BET、ICP、Pyridine-TPD等测试手段对催化剂的物化性质进行表征；在自制的固定床反应器上测试催化剂催化乙醇脱水制取乙烯的性能；探讨TiO2提高复合催化剂催化性能的机理。结果表明： 1. 液相沉积法制备TiO2/4A分子筛复合催化剂的最优工艺条件为：沉积时间18 h，焙烧温度600 °C，沉积液用量400 ml。 TiO2/4A分子筛复合催化剂与原4A分子筛相比表面总酸性减弱，但却表现出更为优良的催化乙醇脱水制乙烯性能，尤以表面沉积有混合晶相TiO2 (A/R)的复合催化剂性能最佳。 2. 铈、锰、铂改性能进一步促进4A分子筛/TiO2复合催化剂催化乙醇脱水生成乙烯，铈-锰联合改性的复合催化剂的性能最佳。 3. 采用分步控制掺杂工艺制备的镍离子在TiO2中呈非均匀分布的复合催化剂中，其中镍离子表面掺杂的复合催化剂的性能最佳，其最佳掺杂量为1.0%。 4. 结合催化剂催化性能和Pyridine-TPD测试结果，我们认为复合催化剂催化乙醇脱水生成乙烯的性能与其总酸性无关，而是与其有效Lewis酸性密切相关。助剂TiO2对复合催化剂的影响表现在两个方面：（1）物理覆盖一部分表面酸位；（2）吸收4A分子筛上受热激发的电子，从而促进4A分子筛上Lewis酸碱对的有效分离，提高复合催化剂的有效Lewis酸性。铈锰铂改性的4A分子筛/TiO2复合催化剂可能是通过增加氧空穴进一步促进有效Lewis酸性的提高。镍离子表面掺杂的TiO2/4A分子筛复合催化剂可能是由于镍离子在外覆双层TiO2的复合催化剂中的扩散分布形成P-N结，P-N结的存在提高了4A分子筛的有效Lewis酸性。
其他摘要	Ethylene is one of the most important intermediate chemicals. Nowadays, ethylene is conventionally produced by steam-cracking of petroleum. With the depletion of primary energy and the aggravation of environmental crisis, bio-ethanol has attracted more and more attention for ethylene production, and this route is recognized as a potential supplement for ethylene supply in the future. Catalyst plays a key role in the technology of ethanol dehydration to ethylene. TiO2/4A zeolite composite catalysts were prepared by coating TiO2 on 4A zeolite via liquid phase deposition, 4A zeolite/TiO2 composite catalysts were separately doped by Ce, Mn, Ce-Mn and Pt through impregnation method, and the TiO2/4A zeolite composite catalysts doped by Ni with nonuniform distribution were prepared by liquid phase deposition under process control. The catalysts were characterized by SEM, XRD, FTIR, BET, ICP and Pyridine-TPD, the catalytic performance of ethanol dehydration to ethylene of the catalysts was tested on a self-made fixed bed reactor, and the catalytic mechanism how TiO2 enhanced the catalytic performance was discussed. The results show that: 1. The optimal conditions for preparing TiO2/4A zeolite composite catalysts through liquid phase deposition were with 18 h deposition, 600 °C calcination and 400 ml deposition solution. In comparison with 4A zeolite, TiO2/4A zeolite composite catalysts exhibited weak surface acidity but much higher catalytic performance, especially the one with mixed TiO2 (A/R) showed best performance; 2. The 4A zeolite/TiO2 composite catalysts modified by Ce, Mn and Pt further promoted ethanol dehydration to ethylene, and the one modified by Ce-Mn exhibited best catalytic performance; 3. Among the TiO2/4A zeolite composite catalysts controllable doped by Ni with nonuniform distribution, the one with surface doped Ni exhibited best catalytic performance, and the optimal doping amount was 1.0%; 4. Based on the catalytic performance and Pyridine-TPD results of the catalysts, it is suggested that the catalytic performance of the catalysts is consistent with the effective Lewis acidity rather than the total acidity. The coated TiO2 might cause the changes of composite catalysts in two aspects. Physically, TiO2 might cover the surface acidic sites of 4A zeolite. Chemically, TiO2 might accept the thermal-induced electrons from 4A zeolite so as to increase the net Lewis acidity of composite catalysts, and consequently enhanced catalytic performance. The 4A zeolite/TiO2 composite catalysts modified by Ce, Mn and Pt further improved the catalytic performance might due to the increased oxygen vacancies promoted the net Lewis acidity. The TiO2/4A zeolite composite catalyst with surface doped Ni might form P-N junction so as to enhance the net Lewis acidity.
页数	75
语种	中文
文献类型	学位论文
条目标识符	http://ir.giec.ac.cn/handle/344007/4037
专题	中国科学院广州能源研究所
推荐引用方式 GB/T 7714	肖妍艳. TiO2/4A分子筛复合催化剂的制备及其乙醇脱水制乙烯性能[D]. 广州能源研究所. 中国科学院广州能源研究所,2009.

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