Effect of potassium and barium on the stability of a carbon-supported ruthenium catalyst for the synthesis of ammonia

Effect of Ru loading and of Ru precursor in Ru/C catalysts for ammonia synthesis

“…Furthermore, intermediate (ca. 5 wt%) [17,18] and high (8-10 wt%) [3][4][5][6][7][19][20][21][22][23] Ru loading is commonly found in more applicative studies, aiming at better understanding the catalytic behaviour under conditions similar to the industrial ones. Needless to say that, from the latter point of view, the goal is to keep metal loading as low as possible.…”

Ammonia synthesis over Ru/C catalysts with different carbon supports promoted by barium and potassium compounds

“…Various supports, such as active carbon and graphite [2][3][4][5][6][7][8][9], alumina [10][11][12][13], carbon-coated alumina [14,15], magnesia [16][17][18][19], a series of zeolites [20][21][22] and even rare-earth metal oxides [23,24] were used in Ru-based catalysts for the ammonia synthesis. The promoters used are mainly alkali metal, alkaline earth metal, rare earth metal and their oxides or hydroxides.…”

Graphitised carbon as support for Ru/C ammonia synthesis catalyst

“…For this purpose we have developed a methanation test, which consists in monitoring the methane formation during ammonia synthesis at 100 bar upon heating up to 700°C. In our opinion this test seems more exhaustive than that developed by others [28], carried out under atmospheric pressure in hydrogen at 520°C.…”

“…Indeed, there are XPS and UPS evidences that Cs and K form intercalation compounds with graphite when heated in H2 [27], so that carbon can stabilise high alkali loading. Furthermore, these promoters showed a positive effect also on thermal stability of the support [24,28].…”

“…The risk of support degradation by Ru-catalysed methanation under ammonia synthesis conditions has been recently recalled [28]. This phenomenon could have dramatic consequences in industrial reactors, should the catalyst not be sufficiently resistant to methanation.…”