Comparing Strengths of Surface Interactions for Reactants and Solvents in Porous Catalysts Using Two-Dimensional NMR Relaxation Correlations
Comparing Strengths of Surface Interactions for Reactants and Solvents in Porous Catalysts Using Two-Dimensional NMR Relaxation Correlations
复制标题
DOI：
10.1021/jp811246j
复制
发表时间：
2009-04-23
影响因子：
3.7
通讯作者：
Gladden, Lynn F.
中科院分区：
文献类型：
--
作者：
Weber, Daniel;Mitchell, Jonathan;Gladden, Lynn F.
二维核磁共振（NMR）弛豫时间相关测量已用于观察多孔催化剂颗粒内液体的行为；特别是与二氧化硅负载钌催化剂 (Ru/SiO2) 上的 2-丁酮氢化相关的液体。研究了 2-丁酮的行为，并将其与在该氢化反应中用作溶剂的水和 2-丙醇的行为进行了比较。对于限制在孔隙中的液体，根据 NMR 弛豫时间之比 T-1/T-2，可以推断出每种液体表面相互作用的相对强度。水被认为具有最强的表面相互作用，而2-丁酮具有最弱的表面相互作用。这些结果得到了置换实验的支持，其中一种液体随着时间的推移在催化剂的孔隙空间内取代另一种液体。为了进行比较，还研究了相同液体在氧化铝负载的钯催化剂 (Pd/Al2O3) 中的行为。 Pd/Al2O3 催化剂中表面相互作用强度的变化比 Ru/SiO2 催化剂中更明显。这项工作证明了核磁共振弛豫时间相关实验对含有金属成分的真实催化体系的适用性。从这些测量中，可以推断出有关反应物进入表面吸附位点的信息。
Two-dimensional nuclear magnetic resonance (NMR) relaxation time correlation measurements have been used to observe the behavior of liquids inside porous catalyst pellets; in particular, liquids of relevance to the hydrogenation of 2-butanone over a silica-supported ruthenium catalyst (Ru/SiO2). The behavior of 2-butanone is studied and compared to that of water and 2-propanol, which are used as solvents in this hydrogenation reaction. From the ratio of NMR relaxation times, T-1/T-2, for the liquids confined in the pores, it is possible to infer the relative strengths of the surface interaction for each liquid. Water is seen to have the strongest surface interaction, and 2-butanone has the weakest surface interaction. These results are supported by displacement experiments, in which one liquid replaces the other over time within the pore space of the catalyst. For comparison, the behavior of the same liquids in an alumina-supported palladium catalyst (Pd/Al2O3) was also studied. The variation in the strengths of surface interactions was more pronounced in the Pd/Al2O3 catalyst than in the Ru/SiO2 catalyst. This work demonstrates the applicability of NMR relaxation time correlation experiments to real catalytic systems containing metallic components. From these measurements, information on the access of reactants to surface adsorption sites can be inferred.