III International Conference

PP-II-24pores (the average diameter is 40-80 Å); the sample specific surface area is 7.7 m 2 /g. Ashydrogen is changed by dry nitrogen during decomposition of Mg(NO 3 ) 2 (support I), aportion of thin pores in the MgO decreases and the specific surface area reduces to 0.8 m 2 /g.In supports I and II, nickel is detected by EDX spectra of MgO as spectral lines of weakintensity corresponding to a nickel concentration of ∼ 2 at.%. Intensity of the nickel lines differsfor different parts of MgO, which indicates different degrees of interaction between MgO andNiO from the oxide film during the heating. One may suggest that the contacting particles ofMgO and NiO react upon each other to yield surface solid solutions [1,2] whereas the MgOparticles outlying from the NiO are not transformed and do not contain nickel. TEM data suggestthat after additional reduction (750° o С, Н 2 ) dispersed nickel crystallites (25 – 70 Å) are appearedon the surface of MgO of the support I. For the MgO surface in support II, nickel is observed onlyon the EDX spectra, however, the sample tested in the reaction also exhibits the presence of nickelcrystallites 20–70 Å in size.The methane conversion value of the porous nickel support (fraction is 0.25–0.50 mm,m=0.80 g) is 20 %. After deposition of support MgO, formed in a flow of N 2 (support I) theconversion value increases to 52 % and the deposition of MgO formed in a hydrogen flow(support II) increases - to 65 %. The additional deposition of nickel results in the increase ofconversion. Note that the prepared nickel catalysts on supports I and II are characterized bycomparable conversion values, which is probably associated with neighboring average sizesof the supported nickel particles.9590CH 4conversion, %85807570656055500 5 10 15 20 25 30 35 40 45 50 55 60t, h123Fig. Influence of reaction time on methaneconversion in steam reforming reaction:1 – 7,2% Ni/pNi + 5,0% MgOII (plate,m=3.07g, V=0.7 сm 3 ); 2 - NIAP-18 (fraction0,25–0,5 mm, m=0,80g); 3 – NIAP-18 (1/2 ofgrain, m=1,46 g, V=0,7 сm 3 ).Figure shows the effect of reaction time on the catalytic activity of the supported nickelcatalyst. The catalyst activity was stable during 50 hour tests. From TEM it was shown thatthere are not any carbon deposits in the tested catalyst sample. For the supported catalystcontaining 7.2 wt.% of Ni (plate) the products composition and conversion is close toequilibrium.References1. Y.H. Hu, E. Ruckenstein: Catal. Lett., 36 (1996) 145.2. G.C.Bond, S.P.Sarsam: Appl. Catal.A:, General 38 (1988) 365.207