Unravelling water effects on solid acid catalysts: Case study of TiO2/SiO2 as a catalyst for the dehydration of isobutanol
Unravelling water effects on solid acid catalysts: Case study of TiO2/SiO2 as a catalyst for the dehydration of isobutanol
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DOI：
10.1016/j.jcat.2016.12.007
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发表时间：
2017-04-01
影响因子：
7.3
通讯作者：
Loridant, S.
中科院分区：
文献类型：
--
作者：
Buniazet, Z.;Couble, J.;Loridant, S.
对水对固体酸催化剂的影响的理解是开发通过生物醇脱水产生烯烃的有效过程的关键问题。在这项工作中，水对异丁醇对线性烯烃的气相转化的TIO2/SIO2催化剂的影响已被阐明，这是首次使用原位酸度测量，该测量是通过流动的NH3探针和水蒸气在吸附下在吸附的水蒸气中实现的原位酸度测量值反应温度范围内的平衡。这种化合物通过将二氧化钛嫁接到介孔二氧化硅上，包含呈散布的TiO2无定形簇，该簇由Ti-O-SI链接锚定，导致催化活性高于TIO2和SIO2。他们仅产生脱水产物，其中30％是线性丁烯。此外，无论接触时间如何，通过将水加入进料，它们的活性得到了显着改善。酸度测量表明，在450度处激活后TiO2/SiO2混合氧化物主要是刘易斯类型的。但是，原位FTIR酸度测量表明，将H2O添加到NH3/HE气体混合物中对Lewis遗址的数量没有影响布朗斯特弱地点在其他地点形成。由于平衡的变化，根据温度和H2O部分压力的变化，这种形成对应于Ti-O-SI键的水解，产生OH酸性基团并在水蒸气下增强催化活性。这项工作中使用的新型酸度测量类型看起来很强大，可以应用于其他酸性异质催化剂。 （c）2016 Elsevier Inc.保留所有权利。
The understanding of water effects on solid acid catalysts is a key issue in developing efficient processes to produce olefins by bio-alcohols dehydration. In this work, the effects of water on TiO2/SiO2 catalysts for the gas phase conversion of isobutanol into linear olefins have been unraveled, using for the first time in situ acidity measurements achieved with a flowing NH3 probe and water vapor containing gas mixtures at adsorption equilibrium in the temperature range of the reaction. Such compounds, prepared by grafting titania onto mesoporous silica, contain well-dispersed TiO2 amorphous clusters anchored by Ti-O-Si linkages, leading to much higher catalytic activity than TiO2 and SiO2. They yielded only dehydration products, among which 30% were linear butenes. Furthermore, their activity was significantly improved by addition of water into the feed, whatever the contact time. Acidity measurements indicated that TiO2/SiO2 mixed oxides were mostly of Lewis type after activation at 450 degrees C. However, in situ FTIR acidity measurements showed that addition of H2O to NH3/He gas mixture has no influence on the number of Lewis sites, while weak Bronsted sites were formed on other sites. This formation, due to a shift of equilibrium depending on both the temperature and the H2O partial pressure, corresponds to the hydrolysis of Ti-O-Si bonds, generating OH acidic groups and enhancing catalytic activity under water vapor. The novel type of acidity measurements used in this work appear powerful and can be applied to other acidic heterogeneous catalysts. (C) 2016 Elsevier Inc. All rights reserved.