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首页> 外文期刊>Chemistry: A European journal >Understanding the solvent effect on the catalytic oxidation of 1,4-butanediol in methanol over Au/TiO _2 catalyst: NMR diffusion and relaxation studies
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Understanding the solvent effect on the catalytic oxidation of 1,4-butanediol in methanol over Au/TiO _2 catalyst: NMR diffusion and relaxation studies

机译：了解溶剂对Au / TiO _2催化剂上甲醇中1,4-丁二醇催化氧化的溶剂影响：NMR扩散和弛豫研究

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The effect of water on the catalytic oxidation of 1,4-butanediol in methanol over Au/TiO _2 has been investigated by catalytic reaction studies and NMR diffusion and relaxation studies. The addition of water to the dry catalytic system led to a decrease of both conversion and selectivity towards dimethyl succinate. Pulsed-field gradient (PFG)-NMR spectroscopy was used to assess the effect of water addition on the effective self-diffusivity of the reactant within the catalyst. NMR relaxation studies were also carried out to probe the strength of surface interaction of the reactant in the absence and presence of water. PFG-NMR studies revealed that the addition of water to the initial system, although increasing the dilution of the system, leads to a significant decrease of effective diffusion rate of the reactant within the catalyst. From T _1 and T _2 relaxation measurements it was possible to infer the strength of surface interaction of the reactant with the catalyst surface. The addition of water was found to inhibit the adsorption of the reactant over the catalyst surface, with the T _1/T _2 ratio of 1,4-butanediol decreasing significantly when water was added. The results overall suggest that both the decrease of diffusion rate and adsorption strength of the reactant within the catalyst, due to water addition, limits the access of reactant molecules to the catalytic sites, which results in a decrease of reaction rate and conversion.
机译：通过催化反应研究和NMR扩散和弛豫研究，研究了水对甲醇中1,4-丁二醇在Au / TiO _2上的催化氧化的影响。向干催化体系中添加水导致转化率和对琥珀酸二甲酯的选择性降低。脉冲场梯度（PFG）-NMR光谱用于评估加水对催化剂内反应物有效自扩散性的影响。还进行了NMR弛豫研究，以探讨在不存在和存在水的情况下反应物表面相互作用的强度。 PFG-NMR研究表明，向初始体系中添加水虽然会增加体系的稀释度，但会导致反应物在催化剂中的有效扩散速率大大降低。从T _1和T _2弛豫测量可以推断出反应物与催化剂表面的表面相互作用强度。发现添加水抑制了反应物在催化剂表面上的吸附，并且当添加水时1，4-丁二醇的T _1 / T _2比明显降低。总体结果表明，由于加水，催化剂中反应物的扩散速率和吸附强度的降低都限制了反应物分子进入催化部位，这导致反应速率和转化率降低。

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