Alkane activation at low temperature on sulfated zirconia

硫酸化氧化锆的低温烷烃活化

• 批准号: 5253584
• 负责人: Professor Dr. Johannes A. Lercher
• 金额: --
• 依托单位: Lehrstuhl für Technische Chemie II
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2000
• 资助国家: 德国
• 起止时间: 1999-12-31 至 2007-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5253584?language=en
• 关键词: Alkane; activation; low; temperature; sulfated

Sulfated zirconia is a very active catalyst for light alkane isomerization. However, the chemistry occurring at the catalyst surface is still under controversy. The projekt aims to obtain formation on alkane activation steps at the surface of sulfated zirconia and samples prepared bay partners in the consortium (Leipzig University) are tested. In situ characterization techniques including temperature programmed desorption (TPD)/reaction, microcalorimetry and in situ IR spectroscopy, are used to study the initial steps of n-butane activation mechanism. N-butane isomerization and hydroisomerization under various experimental conditions including isitope labeling studies with doubly 13C labeled and deuterated n-butane.The apparent activation energy of n-butane isomerization on sulfated zirconia calculated using microcalorimetry is 43 KJ/mol, which led us to conclude that the reaction can occur at room temperature. A decrease of the inducing period and an icrease of the reaction rates for n-butane isomerization are observed by increasing the isobutene/n-butane ratio in the mixture leading to the conclusion that surface intermediates formed by adsoption of iso-butane are involved in the reaction. The formation of C8 hydrocarbon molecules observed by in situ FTIR and the miscellaneous distribution of products observed during reactions using labeled n-butane imply that n-butane isomerization occurs on sulfated zirconia via a bimolecular mechanism. The n-butane isomerization step is suspected to involve a redox activity of the sulfated zirconia support, which is supported by (i), the formation of mono-sulfuric species an the disappearance of bi-sulfuric species observed simultaneously to the formation of C8 molecules an (ii) n-butene and water desorption observed by n-butane TPD. The potential role of a redox chemistry route in the initial step of hydrocarbon activation on sulfated zirconia focuses our attention. In particularly, the transformations and the nature Auf the surface species, i.e., reactant species as well as support surface, has to be clarified using in situ techniques such as FTIR and RAMAN spectroscopy.

硫酸化氧化锆是一种活性很高的轻质烷烃异构化催化剂。然而，在催化剂表面发生的化学反应仍然存在争议。该项目的目的是获得在硫酸化氧化锆表面的烷烃活化步骤的形成，并对财团（莱比锡大学）中的海湾合作伙伴制备的样品进行测试。采用程序升温脱附（TPD）/反应、微量热和原位红外光谱等原位表征技术，研究了正丁烷活化机理的初始步骤。在各种实验条件下，包括用氘代和双13 C标记的正丁烷进行的同位素标记研究，用微量热法计算了正丁烷在硫酸化氧化锆上的异构化反应的表观活化能为43 KJ/mol，表明该反应可以在室温下进行。随着混合物中异丁烯/正丁烷比例的增加，正丁烷异构化反应的诱导期缩短，反应速率加快，表明异丁烷吸附形成的表面中间体参与了反应。通过原位FTIR观察到的C8烃分子的形成和在使用标记的正丁烷的反应过程中观察到的产物的杂项分布意味着正丁烷异构化通过双分子机制发生在硫酸化氧化锆上。正丁烷异构化步骤被怀疑涉及硫酸化氧化锆载体的氧化还原活性，其由（i）与C8分子的形成同时观察到的单硫酸物质的形成和双硫酸物质的消失以及（ii）通过正丁烷TPD观察到的正丁烯和水解吸来支持。氧化还原化学途径在硫酸化氧化锆上烃活化的初始步骤中的潜在作用引起了我们的注意。特别是，表面物种的转化和性质，即，反应物种类以及载体表面，必须使用原位技术如FTIR和拉曼光谱进行澄清。