Transient kinetics of toluene interaction with V/Ti-oxides in anaerobic conditions
Transient kinetics of toluene interaction with V/Ti-oxides in anaerobic conditions
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DOI：
10.1016/j.cej.2004.12.025
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发表时间：
2005-03
影响因子：
15.1
通讯作者：
D. A. Bulushev;E. A. Ivanov;S. Reshetnikov;L. Kiwi-Minsker;A. Renken
中科院分区：
文献类型：
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作者：
D. A. Bulushev;E. A. Ivanov;S. Reshetnikov;L. Kiwi-Minsker;A. Renken
用瞬态响应技术研究了523- 673 K温度下甲苯与含钾锐钛矿-二氧化钛负载的VOx单层（0.35，0.62，0.75和3.7）催化剂的相互作用。在脱水条件下的FT-拉曼光谱用于确定氧化钒的状态。在氧化钒覆盖率小于单层的情况下，发现了K扰动（1020 cm-1）和K掺杂（990 cm-1）的单体氧化钒物种以及“非晶”KVO 3（960- 940 cm-1）。块状V2 O 5（994 cm-1）仅在3.7 ML V/TiO 2催化剂中作为主要物质存在。苯甲醛（BA），总氧化产物和表面含碳物种的甲苯相互作用的主要产物。提出的反应网络包括五个步骤和两种类型的氧位点。BA和CO2的生成均随钒浓度的增加而增加。前者主要是由亲核晶格氧参与的单层氧化钒物种。后者以及表面含碳物种的主要部分的形成增加得更陡峭的依赖，可能是从亲电氧丰富的聚合氧化钒物种和V2 O 5。所进行的动力学建模令人满意地描述了BA，CO2和甲苯与预氧化的0.35-0.75 ML V/TiO 2催化剂的甲苯相互作用过程中获得的响应曲线。在3.7 ML V/TiO 2催化剂中存在大量V2 O 5似乎提供了一些反应机理的变化，需要修改反应方案。
Toluene interaction with the catalysts consisting of 0.35, 0.62, 0.75 and 3.7 monolayers (ML) of VOxsupported on anatase–titania, containing potassium, was studied by transient response techniques at 523–673K. FT-Raman spectroscopy under dehydrated conditions was used to determine the state of vanadia. K-perturbed (1020cm−1) and K-doped (990cm−1) monomeric vanadia species as well as “amorphous” KVO3(960–940cm−1) were found at vanadia coverage less than a monolayer. Bulk V2O5(994cm−1) was present only in the 3.7 ML V/TiO2catalyst as a dominant species. Benzaldehyde (BA), total oxidation products and surface carbon-containing species were the main products of the toluene interaction. The proposed reaction network involves five steps and two types of oxygen sites. Both the BA and CO2formation increased with the concentration of vanadia. The former is determined mainly by nucleophilic-lattice oxygen that is involved in the monolayer vanadia species. The latter as well as the formation of the main part of surface carbon-containing species increased much more steeply being dependent, probably, from electrophilic oxygen abundant in polymerised vanadia species and V2O5. The performed kinetic modelling satisfactorily describes the response curves of BA, CO2and toluene obtained during the toluene interaction with the pre-oxidised 0.35–0.75 ML V/TiO2catalysts. The presence of bulk V2O5in the 3.7 ML V/TiO2catalyst seems to provide some change in the reaction mechanism demanding a modification of the reaction scheme.