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

H-1 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 socialite 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 313 K, 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 CH4 proceeds on Ag-n-Y. ZO(-)Ag(n)(+) + CH4 --> Ag-n-H + ZO(delta-)CH(3)(delta+) The reaction of CH4 with C2H4 proceeded to give C3H6 on Ag-n-Y at 673 K. These results demonstrate that methane is easily activated on Ag-Y. (C) 2002 Elsevier Science B.V All rights reserved.