...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Catalysis science & technology >The influence of solvent composition on the coordination environment of the Co/Mn/Br based para-xylene oxidation catalyst as revealed by EPR and ESEEM spectroscopy
【24h】

The influence of solvent composition on the coordination environment of the Co/Mn/Br based para-xylene oxidation catalyst as revealed by EPR and ESEEM spectroscopy

机译：The influence of solvent composition on the coordination environment of the Co/Mn/Br based para-xylene oxidation catalyst as revealed by EPR and ESEEM spectroscopy

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相关主题

摘要

The industrially important para-xylene oxidation reaction, based on a Co/Mn/Br catalyst, operates in a water/acetic acid (H2O/AcOH) solvent system. The correct H2O/AcOH ratio of the solvent is crucial in controlling the reaction yields and selectivities. However, the influence of this variable solvent system on the catalyst structure and coordination environment is not well understood. Using UV-vis spectroscopy, we observed the formation of tetrahedral Co~(2+) species when the solvent composition was below 10 wt% H2O. These were considered to be tetrahedral Co~(2+) species with either 2 or 3 coordinating Br-ligands. The pronounced CW EPR linewidth changes observed in the Mn~(2+) signals revealed a strong correlation on the solvent H2O content. Detailed analysis revealed that these variations in the linewidth were attributed to the changing coordination sphere around the Mn~(2+) centres, with a maximum linewidth occurring at 8-10 wt% H2O. The narrow linewidths below 8 wt% H2O were found to result from substitution of H2O/AcOH ligands by Br, whereas above 8 wt% H2O a further narrowing of the linewidth was actually caused by greater amounts of H2O coordination. To confirm this, 3-pulse ESEEM measurements on the Mn~(2+) were conducted in the solvent compositions corresponding to 3, 8, 13.7 and 20 wt% H2O. The results showed a marked change in the number (n) of coordinated H2O molecules (ranging from n = 0, 0, 1.0 to 4.0 respectively for the 3-20 wt% H2O content). For the first time, these findings provide a crucial insight into the relationship between solvent composition and catalyst structure in this industrially important catalytic reaction.
机译：工业上重要的对二甲苯氧化反应,基于有限公司/ Mn / Br催化剂,运作在水/醋酸(H2O /乙酸)溶剂系统。正确的水/乙酸溶剂的比例收益率和控制反应的关键选择性。催化剂结构变量溶剂系统和协调环境并不好理解。观察到的形成四面体有限公司~ (2 +)物种时,溶剂成分低于10wt % H2O。公司~(2 +)物种与2或3协调Br-ligands。改变观察Mn ~(2 +)信号显示很强的相关性在溶剂水含量。详细的分析显示,这些变化线宽的变化协调球体周围的Mn ~(2 +)中心,最大线宽发生8 - 10 wt %H2O。发现的结果替换H2O /乙酸配体通过Br,而高于8 wt % H2O进一步收窄的线宽是造成的大量的水协调。这个,3-pulse ESEEM测量在Mn ~ (2 +)在溶剂成分进行了吗13.7对应3 8和20 wt % H2O。结果显示显著变化(n)数量协调的水分子(从n = 0,0, 1.0到4.0分别为3 - wt % H2O内容)。提供一个洞察的关系至关重要溶剂组成和催化剂之间在这个工业结构很重要催化反应。

著录项

获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号