Measures to reduce hydrogen inhibition

Urabe K et considered that when ammonia exists on Ru-K/AC, part of K will transform to the amino or imide compounds. In the presence of hydrogen, part of K will transform to the hydrides which decreases the ability of supplying 

Prom experiments of hydrogen adsorption at room temperature, Aika et al. found that when the molar ratio of Sm/Ru was 10, the adsorption amount of hydrogen will reduce to 1/3 of the origin, which indicates that there is a very strong interaction between ruthenium and lanthanide oxides. The chemisorption amount of hydrogen is not reduced obviously following the addition of CsOH on ruthenium surface. For example, when Sm/Ru =10.0, the H/Ru ratio will decrease to 0.18, while Cs/Ru = 10.1, the H/Ru ratio is 0.45. 

Catalysts Ammonia synthesis reaction s Isotope equilibrium reaction of dinitrogen  

The d-characteristic (50%) of ruthenium is the strongest among the transition metals, and that of Ni, Co are about 40%. Therefore, the hydrogen poison of ruthenium is more obvious and more serious than that of Ni and Co. The d-characteristic of metal is reduced by alloyed catalyst in above ethylene hydrogenation, therefore the hydrogen inhibition is eliminated. In the alloy composed by Cu(x) and Ni (1-x), the vacancy of d orbit is 0.6—x when x 0.6 and 0 when x 0.6, respectively. According to the valence principle of Pauling, Hall has calculated the d-characteristic of Cu-Ni alloy as shown in Table 6.49. 

It can be seen from these figures that the change of activity of A301 iron catalyst is very little with H2/N2 ratio, while it is obvious on Ru catalyst. At 400°C, the activity of Ru catalyst increases with the decreasing of H2/N2 ratio when it is higher than 1.5 and decrease when H2/N2 ratio is lower than 1.5 (Fig. 6.66). Here, the activity is above 22% on ruthenium catalyst and the equilibrium ammonia concentration is about 25% at H2/N2 = 3. At the same time, equilibrium ammonia concentration also decreases with the decrease of H2/N2 ratio. Therefore, the effect of change of H2/N2 ratio is not too obvious. For iron catalysts, the activity does not change with the decrease of H2/N2 ratio until H2/N2 ratio is lower than 0.67 at 400°C. 

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