Effect Of Promoters And Preparing Methods On The Activity Of Ammonia Synthesis And Methanation Of Ru/AC Catalyst

N2 physical adsorption, CO chemisorption , H2 temperature-program desorption, XRD, XPS and XRF were carried out to characterize the properties of the supports and catalysts for ammonia synthesis. And we studied the effect of different reducing agents and reduction methods on the activity of catalysts, the effect of activated carbon support and promoters on the activity and methanation of catalyst.The result showed that the existence of chlorine have more effect on catalyst supported on Al2O3 than that on activated carbon. Using hydrazine hydrate as reducer, it can clear off chlorine which comes from the precursor-RuCl3, avoid the Ru particle sintering under atmosphere, and keep a higher dispersion of Ru. But using hydrogen, lots of chlorine remained on the catalyst, and when catalyst is exposed on the atmosphere, Ru particle is easy to sinter, which result in the reduction of catalyst activity.It was found that the thermal modification of the activated carbon can bring about different degrees of graphitization, but the surface area and porosity decrease dramatically. Oxidative treatment partially recovers the surface area and porosity. The higher the thermal treatment temperature, the lower the activity of the methanation of the activated carbon and the higher the activity of ammonia synthesis, but the more difficult the recovery of the surface area and porosity becomes. So the thermal modification of the activated carbon has a optimal temperature which was about 1800℃.The mechanisms of all kinds of promoters promoted the activity of ammonia synthesis were difference. The alkali metal hydroxides increased the N2 direct dissociation and the alkali earth metal oxides promoted N2 dissociation through hydrogen assisting. The lanthanide oxides promoted the activity by inhibiting the catalyst from hydrogen adsorption. In three kinds of promoters, the alkali earth metal oxides have better function for ammonia synthesis, and the lanthanide oxides have lower function for that.The catalyst activity is related to the electronegativity of the alkali metal hydroxides and the alkali earth metal oxides, the smaller the electronegativity of the promoters, the higher the catalyst activity of ammonia synthesis. Under the reaction condition, KOH can spread and wet the support, which would promote the activity of methanation. BaO and Sm2O3 are in a non-wetting condition, and they exhibit contact angles with support bigger. So they have little effect on the activity of methanation. Because BaO and Sm2O3 covered with some activity sites, the activity of methanation reduced in some degrees.The activity of ammonia synthesis of multi-promoters catalyst was higher that of uni-promoter catalyst. The catalyst exhibited higher activity of ammonia synthesis when it contained KOH and BaO. And the K-promoted catalyst was easy to react with H2 to form methane. In order to get high activity of ammonia synthesis, the catalyst must contain KOH and BaO. And to make the catalyst long-life, the temperature of ammonia synthesis must be under 425℃.