Preparation of Ni/SiO2 Catalyst by Chemical Fume Thermal Deposition

Ni/SiO2 catalysts were prepared by chemical fume thermal deposition. This preparation proceeded as follows. Nickel-salt/methanol solution was sprayed into a tubular reactor with vaporized SiCl4 and air, and then the mixture was immediately pyrolyzed in a reactor whose temperature was controlled at 1573 K at the hottest point. The apparent diameter of the catalyst produced was estimated by the BET method, and the diameter of NiO, dNiO, x, was measured by XRD. The relationship between dNiO, x and the relative viscosity of sprayed solution, η, was represented by the following equation under the present experimental conditions. dNiO, x=k (η0.45) n where n and k are different for each case; n=1.48, k=19 nm for the [Ni (NO3) 2 /CH3OH+air+SiCl4] system, n=1.48, k=32 nm for the [NiCl2 /CH3 OH + air + SiCl4] system, n=0.64, and k=110 nm both for the [Ni (NO3) 2 CH3OH+air] system and the [NiCl2/ CH3OH+air] system. The apparent growth rate of the catalyst, γap, is proportional to the molar fraction of Ni salt, χ. γap=kapχ The reactivity of the catalyst was examined by the methanation of carbon mono-xide as a model reaction. The results show that the activity (TOF) was one or two magnitudes higher than those of conventionally prepared impregnated catalysts.