Chemisorption study of hydrogen and methane by ~1H MAS NMR and conversion of methane in the presence of ethylene on Ag-Y zeolite

摘要

~H MAS NMR showed that hydrogen dissociatively adsorbs on Ag-Y and generates acidic protons and silver-hydride species (Ag_n-H). The peak due to Ag_n-H was observed at -0.1 ppm together with peaks due to acidic protons in the supercages (3.9 ppm) and in the sodalite cages (4.7 ppm). The hydrogen chemisorption on Ag-Y is reversible. Thus, the peaks at 3.9 and -0.1 ppm disappeared by evacuating the Ag-Y at 313K, and the intensities of these peaks recovered by re-exposing the evacuated sample to hydrogen at 313 K.Adsorption of methane on Ag-Y at 423 K also gave rise to the peak due to Ag_n-H, indicating that heterolytic dissociation of CH_4 proceeds on Ag_n-Y.The reaction of CH_4 with C_2H_4 proceeded to give C_3H_6 on Ag_n-Y at 673 K. These results demonstrate that methane is easily activated on Ag-Y.