Methanation of the carbon supports of ruthenium ammonia synthesis catalysts: A review

A Mesoporous Carbon‐Supported and Cs‐promoted Ru Catalyst with Enhanced Activity and Stability for Sustainable Ammonia Synthesis

“…Recently, Tsyrul'nikov et al indicated that the deactivation of the carbon-supported Ru catalysts for ammonia synthesis is strongly associated with the sintering of Ru particles, which is caused by hydrogen dissociation over the metallic Ru active sites, spillover of protons to the RuÀC interfaces, and, subsequently, the methanation of the carbon supports. [19] The present study shows that the CsÀRu/MPC catalyst with small Ru particles confined to the interior of the mesoporous structure is able to catalyze ammonia synthesis in a relatively low-temperature region where the methanation side reaction is limited. In contrast, the low activity of the CsÀRu/AC catalyst for ammonia synthesis presumably arises from the sintering of the Ru particles, which are caused by the methanation side reaction during the ammonia synthesis.…”

“…This reduction condition is similar to that of the ammonia synthesis. [19] The present study shows that the CsÀRu/MPC catalyst with small Ru particles confined to the interior of the mesoporous structure is able to catalyze ammonia synthesis in a relatively low-temperature region where the methanation side reaction is limited. The results imply that the decrease in the activity of the prepared CsÀRu catalysts caused by the sintering during the ammonia synthesis is influenced not only by the reaction temperature but also by the reducing atmosphere formed during ammonia synthesis, particularly for the CsÀRu/AC.…”

Active and stable Fe-based catalyst, mechanism, and key role of alkali promoters in ammonia synthesis

“…Interestingly, the reduction of iron occurs together with incomplete hydrogenation of the carbon support to form methane. [53][54][55] This methanation process of the carbon support results in a considerable weight loss of the sample, corresponding decrease of the carbon content (55-60 wt. %) and an increase in the iron content while providing mesoporosity to the final material (pore size > 2 nm).…”

“…Therefore, the introduction of alkali metal partially prevents the carbon from interacting with active hydrogen. [54] Note that the weight loss observed during the H 2 treatment leads to a 2 to 3 fold increase in the promoter content compared to the original content (Table 1). Notably, after the catalytic reaction, there were no significant changes observed in the alkali content in the catalysts (Table 1), suggesting that during the catalytic reaction, the alkali oxide (Cs 2 O and K 2 O) remains stable.…”

Strong Interaction of Ruthenium Species with Graphite Structure for the Self-Dispersion of Ru under Solvent-Free Conditions

“…One of the key challenges of carbon-supported Ru catalysts for ammonia synthesis is that Ru catalyzes the methanation of carbon support resulting in the gradual degradation of catalyst. 11 Graphite is well accepted to be more inert in this regard. As presented in Figure 2b, formation of methane for HSAG-supported catalysts commences at temperatures above 450 °C, which is far higher than that of an activated carbonsupported catalyst.…”