The promoter of ruthenium catalyst

It is generally considered that the structural factor of ruthenium catalysts is not as important as those of iron-based catalysts, while the electronic factor is the most important one. The catalytic activity of Ru/AC catalyst without promoter is very low. The promoters which can donate electron can remarkably increase the activity of catalyst. The promoters of ruthenium catalysts mainly include alkali metals, alkaline earth metals, rare earth metal oxides and actinide metal compounds. 

Promoter elements Precursor of promoter M/Ru (molar ratio) Activity fj, mol g ) Particle size of Ru (nm) 

Note 1. Precursor of Ru is RuCls 3H2O, AC is not treated by acid. 

The ruthenium catalyst without promoter almost is inactive, and the outlet ammonia concentration of 4% Ru/C catalyst Is only 0.13% under the conditions of 430°C, 10.0MPa and 10,000h For single promoter of Ru/C catalyst with the alkali metal, alkaline earth metal nitrate acts as the precursors of promoter respectively, the alkali metal and alkaline earth metal nitrate can Increase the activity of the ruthenium catalyst In different extent. The order of the Influence, alkali metal nitrates are CsNOs RbNOa KNO3 NaNOa and that of alkali earth metal nitrate is Ba(N03)2 Sr(N03)2 Mg(N03)2 Ca(N03)2. In the selected eight kinds of promoters, Ba(N03)2 and CsNOa are the most effective and the outlet ammonia concentration are 13.38% and 9.89% at 430°C, 10.0MPa and 10,000h respectively. 

The effect of promoter is related with support. For RU-M/AI2O3 catalysts, alkali metal can enhance not only the TOF of the catalyst, but also the dispersion of Ru. And the hydroxide of alkali metal can prevent the poison of H2O or CO. For the RU/AI2O3 catalyst promoted by alkali metal of Cs, Rb and K, the effect of promoter Increases with the decreasing of the electronegativity or the increasing 

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