CO吸附和加氢反应过程的原位高压MAS NMR研究

摘要/Abstract

摘要：

应用原位变温高压MAS核磁共振技术，对比研究了CO在不同Rh基催化剂上的吸附和加氢反应过程. ²⁹Si MAS NMR研究结果表明：Rh基催化剂中加入金属助剂后，载体Silicate-1上的表面硅羟基减少，助剂金属与硅羟基作用锚锭在载体表面.¹³C MAS NMR研究结果表明：当引入CO/H2混合气后，在Rh/Silicate-1催化剂上只能观测到气相CO、线式吸附CO和孪式吸附CO的快速交换信号；而在Rh-Mn/Silicate-1和Rh-Mn-Li/Silicate-1催化剂上，还观测到了倾斜式吸附的CO共振信号，表明助剂Mn或Mn-Li的加入促进了CO的吸附. 随着反应温度升高，CO/H₂在Rh/Silicate-1催化剂上转化生成CO^₂，进一步升高温度会有CH₄生成；而CO/H₂在RhMnLi/Silicate-1催化剂上反应活性更高，在较低的温度下就会转化生成CO₂，但未观测到甲烷的生成. ¹H MAS NMR 谱显示，反应后载体Silicate-1上硅羟基的量会减少，表明CO与载体部分表面硅羟基反应生成了CO₂.

关键词: 核磁共振(NMR), 原位高压固体核磁共振, CO吸附, CO加氢反应, Rh基催化剂

Abstract:

The adsorption and hydrogenation processes of CO on Rh-based catalyst were studied by in situ high-pressure (HP) MAS NMR techniques under batch-like conditions. ²⁹Si MAS NMR spectra showed that the silanol concentrations of the support Silicate-1 were reduced after impregnation of metal species. After introduction of ¹³CO/H₂ below 200 ℃, only the average exchanged signal of CO between gaseous CO, linearly adsorbed CO and dicarbonyl adsorbed CO was observed on Rh/Silicate-1; while the titled adsorbed CO appeared on Rh-Mn/Silicate-1 or Rh-Mn-Li/Silicate-1. So, the addition of Mn or MnLi could enhance the CO adsorption. Under batchlike condition, high-pressure ¹³C MAS NMR showed that the CO/H₂ reactants could only be converted to CO₂and CH₄ on Rh/Silicate-1, while only CO2 appeared on Rh-Mn-Li/Silicate-1 at relatively lower temperatures. Meanwhile, ¹H MAS NMR showed the obvious decrease of silanol groups after reaction that indicated CO could react with silanol groups to produce CO₂.

Key words: NMR, In situ high-pressure MAS NMR, CO adsorption, CO hydrogenation, Rh-based catalyst

中图分类号:

O482.53

徐舒涛, 张维萍, 兰喜杰, 韩秀文, 包信和. CO吸附和加氢反应过程的原位高压MAS NMR研究[J]. 波谱学杂志, 2010, 27(2): 141-149.

XU Shu-Tao, ZHANG Wei-Ping, LAN Xi-Jie, HAN Xiu-Wen, BAO Xin-He. An In situ High-Pressure MAS NMR Study of the Adsorption and Hydrogenation Processes of CO[J]. Chinese Journal of Magnetic Resonance, 2010, 27(2): 141-149.

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