Solvent effect and reactivity trend in the aerobic oxidation of 1,3-propanediols over gold supported on titania: NMR diffusion and relaxation studies.
Solvent effect and reactivity trend in the aerobic oxidation of 1,3-propanediols over gold supported on titania: NMR diffusion and relaxation studies.
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DOI：
10.1002/chem.201300502
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发表时间：
2013-08
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影响因子：
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通讯作者：
C. D'agostino;Tatyana Kotionova;J. Mitchell;Peter J. Miedziak;D. Knight;S. Taylor;G. Hutchings;L. Gladden;M. Mantle
中科院分区：
文献类型：
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作者：
C. D'agostino;Tatyana Kotionova;J. Mitchell;Peter J. Miedziak;D. Knight;S. Taylor;G. Hutchings;L. Gladden;M. Mantle
在最近的工作中，据报道，溶剂组成的变化，确切地说是水的添加，由于反应物的扩散和吸附性质的变化，显著抑制了Au/TiO 2催化剂在甲醇中的1，4-丁二醇的有氧氧化中的催化活性。为了了解水对甲醇中二醇氧化的抑制机理是否普遍有效，研究了溶剂对1，3-丙二醇及其两种甲基取代同系物2-甲基-1，3-丙二醇和2，2-二甲基-1，3-丙二醇的好氧催化氧化的影响，本文采用常规催化反应监测与脉冲场梯度核磁共振（PFG-NMR）相结合的方法，研究了Au/TiO 2催化剂上的扩散和NMR弛豫时间测量。当水存在于初始二醇/甲醇混合物中时，二醇转化率显著较低。还观察到二醇组内的反应性趋势。结合NMR扩散和弛豫时间测量表明，分子扩散，特别是二醇吸附的相对强度，是在确定的转化率的重要因素。这些结果突出了NMR扩散和弛豫技术作为催化材料的新型非侵入性表征工具，补充了传统的反应数据。
In recent work, it was reported that changes in solvent composition, precisely the addition of water, significantly inhibits the catalytic activity of Au/TiO2 catalyst in the aerobic oxidation of 1,4-butanediol in methanol due to changes in diffusion and adsorption properties of the reactant. In order to understand whether the inhibition mechanism of water on diol oxidation in methanol is generally valid, the solvent effect on the aerobic catalytic oxidation of 1,3-propanediol and its two methyl-substituted homologues, 2-methyl-1,3-propanediol and 2,2-dimethyl-1,3-propanediol, over a Au/TiO2 catalyst has been studied here using conventional catalytic reaction monitoring in combination with pulsed-field gradient nuclear magnetic resonance (PFG-NMR) diffusion and NMR relaxation time measurements. Diol conversion is significantly lower when water is present in the initial diol/methanol mixture. A reactivity trend within the group of diols was also observed. Combined NMR diffusion and relaxation time measurements suggest that molecular diffusion and, in particular, the relative strength of diol adsorption, are important factors in determining the conversion. These results highlight NMR diffusion and relaxation techniques as novel, non-invasive characterisation tools for catalytic materials, which complement conventional reaction data.