ADSORBED HYDROGEN EFFECT ON THE ADSORPTION AND REACTIVITY OF N-2 MOLECULES ON RU/MGO AND RU-CS+/MGO - HYDROGEN DIPOLE EFFECT ENHANCED BY DOPED CS+

The effects of adsorbed hydrogen on the N-2 adsorption and N-2 isotope displacement rate on Ru/MgO and Ru-Cs+/MgO were investigated by FTIR. The H-2 was found to be adsorbed dissociatively on on-top sites [1880w(sh), 1801w(sh), and 1717s cm(-1)], bridging sites [1550w and 1330w cm(-1)], and threefold sites [1120m and 933m cm(-1)] on Ru/MgO, and similarly on three kinds of adsorption sites on Ru-Cs+/MgO. The bridging hydrogen on Ru/MgO was thermally more stable than the other two. Molecular N-2 could be adsorbed as an on-top form on Ru. By the small amount of preadsorbed H(a) [(a)/Ru-surf=14%], the N-2 isotope displacement rate N-15(2)(a)-->N-14(2)(a) in N-14(2) On Ru/MgO was largely reduced to 12%, and the reduction on Ru-Cs+/MgO was more serious (to 4%). The main factors of these reductions were interpreted as direct repulsion of H(a) and N-2 on Ru/MgO and Ru-hydride dipole effect enhanced by doped Cs+ on Ru-Cs+/MgO. The common factors in N-2 displacement reaction and the catalysis from N-2 are discussed in terms of the hydrogen effect.