Ammonia synthesis over ruthenium catalysts supported on high surface area MgO and MgO-Al2O3 systems

作者：Szmigiel D; Rarog Pilecka W; Miskiewicz E; Glinski M; Kielak M; Kaszkur M; Kowalczyk Z^*

来源：Applied Catalysis A: General , 2004, 273(1-2): 105-112.

DOI：10.1016/j.apcata.2004.06.020

• ammonia synthesis
• ruthenium catalysts
• promotion with barium
• magnesia
• magnesium-aluminum spinel
• magnesia-alumina supports

Ruthenium catalysts (5-15 wt.%) deposited on the high surface area magnesia (S-BET = 94 m(2)/g), magnesium-aluminum spinel (96 m(2)/g) and magnesia-alumina mixture (Mg:Al = 1:2 molar ratio, 65 m2/g) were characterized by the chemisorption techniques and tested in NH3 synthesis. The chemisorption experiments (02, CO) have shown that ruthenium is highly dispersed (FE = 60-95%), even if the Rut loading is high (similar to 15 wt.%). The catalytic properties (TOF) of small ruthenium particles supported on Mg-Al spinel (the most effective unpromoted systems) proved to be only slightly, by 40%, more advantageous in NH3 synthesis at 400 degreesC and 63 bar than the properties of particles supported on MgO-Al2O3 mixture (the least active system), TOF over the former being roughly independent of the Ru crystallite size (1.0-1.5 nm). In contrast, the activities of the Ba-doped samples differed significantly, i.e. the TOF values (63 or 90 bar, 400 degreesC over optimally promoted Ba-Ru/MgO were by four to eight times higher than those over Ba-Ru/Mg-Al spinel and by 30 times higher than over Ba-Ru/MgO-Al2O3 mixture. The effect of the support on the Ba promotion is discussed. Under comparable conditions (400 degreesC, 63 bar, 8.5% NH3 and 400 degreesC, 90bar, 11% NH3), the Ba-Ru/MgO catalyst (10 wt.% Ru) was by several times more active than multipromoted fused iron, the comparison being based on the volumetric reaction rates.

• 出版日期2004-10-8