钯—炭催化剂中被吸附氢的NMR研究

~1H NMR STUDY OF THE ADSORBED HYDROGEN IN PALLADIUM-CARBON CATALYSTS

在海棉钯中溶解氢的1H NMR共振峰的高场方向20ppm处,观察到负载在活性灰上的钯催化剂中被吸附氢的一个强共振峰。它的位置随活性炭的品种而异,且与催化剂在加氢反应中的活性有关。但是自旋晶格驰豫时间T1与催化剂活性关系较小。从其位置和强度看,它是催化剂中被吸附氢的一种特殊状态,可能是“溢出氢”。用活性炭载体吸附水的NMR参数讨论了载体的亲水性和催化剂活性的关系。

A 1H resonance peak of the adsorbed hydrogen in palladium-carbon catalysts was observed at the high field side about 20 ppm away from the resonance peak of the dissolved hydrogen in the palladium sponge. Its position varies with the species of the carbon support, and is related to the activity of the palladium-carbon catalyst in hydrogenation reactions. While, the spin lattice relaxation time of the resonance peak does not show any dependency on the activity of the catalyst. It seems to be dependent on the amount of surface acid groups of the support. This resonance implies a special state of the adsorbed hydrogen and can be attributed to the spilled over hydrogen. The activity of the catalyst is discussed with respect to the hydrophobic property of the support by the NMR parameters of water adsorbed on the support.