Applied Catalysis B: Environmental, Vol.106, No.3-4, 460-468, 2011
2.8NiO-H1.8Ni0.6(OH)MoO4-Novel nanocomposite material for the reactive adsorption of sulfur-containing molecules at moderate temperature
It has been found that a poorly crystalline green precipitate that forms in boiling ammonia solution of Ni(NO3)(2) and (NH4)(6)Mo7O24 yields on annealing a Ni-rich material (Ni/Mo=3.4) containing slit shaped mesopores and exhibiting the BET surface area of 230 m(2)/g. Characterization of the material by TGA, XRD, TEM. SEM, and EXAFS allowed to determine that it is a nanocomposite consisting of Ni-Mo (hydro)oxide layers H1.8Ni0.6(OH)MoO4 which are pillared by NiO nanoparticles (D=3 nm). The structure of the layers appears to be similar to that found in the previously described crystalline molybdate (NH4)HNi2(OH)(2)(MoO4)(2) prepared in the similar conditions. The obtained nanocomposite 2.8NiO-H1.8Ni0.6(OH)MoO4 can be completely reduced in H-2 flow at 300 degrees C yielding unsupported Ni3.4Mo bimetallic nanoparticles (D = 3.6 nm) which are stable towards sintering. The material shows remarkable activity in a moderate temperature reactive adsorption of thiophene: at 300 degrees C the rate of its sulfidation in the presence of thiophene is an order of magnitude higher than that of conventional Ni/ZnO sorbent. Such increase of activity is attributed to formation (after partial sulfidation) of the mixed Ni-Mo-S phase, which is known to be highly active in catalytic hydrodesulfurization of sulfur-containing molecules. Also, due to its open structure the nanocomposite reacts rapidly and completely with H2S even at 200 degrees C, while only the surface sulfidation is observed for ZnO nanoparticles under the same conditions. (C) 2011 Elsevier B.V. All rights reserved.