The size dependence of activities and selectivities in the hydrogenation of cyclopropane (CP) was studied on the precisely controlled and measured ruthenium clusters of nanometer size supported on NaY zeolite over reaction temperature from 200 K to 240 K. The hydrogenolysis of ethane was also studied over reaction temperature from 423 K to 473 K with the same method as CP hydrogenation.
The existence of ruthenium metal clusters in t zeolite supercage was proved by $^{129}Xe$ NMR and the cluster size (number of atoms) was determined by the xenon adsorption method.
For the clusters of between 20 and 200-atom size, the activity for ethane hydrogenolysis decreased as the cluster size decreased. However, the activity for CP hydrogenation to propane increased as the cluster size decreased from 55-atoms to 2-atoms. At the temperature close to 200 K, the fragmentation of CP into methane was dominant. This reaction did not occur in the metal clusters on the external surface of zeolite crystal. The selectivity for propane increased as the reaction temperature became close to 240 K. The selectivities were remained constant with the change of cluster size.
The activation energies for CP hydrogenation and ethane hydrogenolysis were almost constant for different cluster size, which indicates that the reaction paths were same for all different size clusters.
