Solvent inhibition in the liquid-phase catalytic oxidation of 1,4-butanediol: understanding the catalyst behaviour from NMR relaxation time measurements
Solvent inhibition in the liquid-phase catalytic oxidation of 1,4-butanediol: understanding the catalyst behaviour from NMR relaxation time measurements
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DOI：
10.1039/c6cy01458e
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发表时间：
2016-01-01
影响因子：
5
通讯作者：
Gladden, Lynn F.
中科院分区：
文献类型：
--
作者：
D'Agostino, Carmine;Feaviour, Mark R.;Gladden, Lynn F.
将催化反应研究和核磁共振弛豫时间测量进行了比较，研究了反应物和溶剂的竞争吸附对催化转化的影响。选择的反应是在不同负载金属催化剂上对1，4-丁二醇在甲醇中的好氧催化氧化。由核磁共振T-1/T-2比值，其中T-1为纵向自旋弛豫时间，T-2为横向自旋弛豫时间，确定了反应物和溶剂在不同催化表面的相对亲和力。与反应物相比，活性最低的催化剂对溶剂具有优先的表面亲和力。相反，与溶剂相比，活性最高的催化剂对反应物具有更好的表面亲和力。值得注意的是，对于1，4-丁二醇的氧化完全无效的Ru/SiO_2对1，4-丁二醇(反应物)的T-1/T-2比率(表面亲和力)低于对“弱相互作用”烷烃的T-1/T-2比率，这表明对二醇官能团的表面亲和力很差。这些结果直接证明了在液相氧化反应中，吸附物-吸附剂相互作用对催化剂活性的重要性，并表明溶剂的竞争吸附在这些反应中起着重要的作用。这项工作表明，核磁共振弛豫时间分析是比较液体在多孔催化剂上的吸附的有效方法，为不同化学物种在催化剂表面的亲和力提供了有价值的信息。此外，结果表明，核磁共振弛豫时间的测量不仅可以用来指导特定催化剂使用的溶剂的选择，而且还可以用来指导催化剂本身的选择。结果表明，该方法可以用来预测催化剂的行为，从而改进多相催化过程的设计和优化。
Catalytic reaction studies and nuclear magnetic resonance (NMR) relaxation time measurements have been compared to study the influence of competitive adsorption of reactant and solvent on catalytic conversion. The reaction chosen is the aerobic catalytic oxidation of 1,4-butanediol in methanol over different supported-metal catalysts. From the NMR T-1/T-2 ratio, where T-1 is the longitudinal and T-2 the transverse spin relaxation time, the relative affinity of reactant and solvent for different catalytic surfaces is determined. The catalysts with the lowest activity show a preferential surface affinity for the solvent compared to the reactant. Conversely, the catalyst with the highest activity shows a preferential surface affinity for the reactant compared to the solvent. Significantly, Ru/SiO2, which is totally inactive for the oxidation of 1,4-butanediol, exhibited a lower T-1/T-2 ratio (surface affinity) for 1,4-butanediol (reactant) than for a "weakly-interacting" alkane, indicating a very poor surface affinity for the diol functionality. The results provide direct evidence of the importance of the adsorbate-adsorbent interactions on catalyst activity in liquid-phase oxidations and indicate that the competitive adsorption of the solvent plays an important role in these reactions. This work demonstrates that NMR relaxation time analysis is a powerful method for comparing adsorption of liquids in porous catalysts, providing valuable information on the affinity of different chemical species for a catalyst surface. Moreover, the results demonstrate that NMR relaxation time measurements can be used not only to guide selection of solvent for use with a specific catalyst, but also selection of the catalyst itself. The results suggest that this method may be used to predict catalyst behaviour, enabling improved design and optimisation of heterogeneous catalytic processes.