FTIR Study of Adsorbed Nitrogen and hydrogen on Ruthenium Catalyst for Next Generation Ammonia Synthesis

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Iron catalysts suffer from ammonia poisoning, because of which one-pass conversion is controlled to keep the low value. Ruthenium was started to be used as a second generation ammonia catalyst because it has an advantage not to be poisoned by ammonia, however it has a disadvantage of hydrogen poisoning. The active ruthenium catalyst developed under 1 atom test some times are not active under the industrial high pressure condition because of the strong hydrogen poisoning. The purpose of this work is to develop a Ru-catalyst which does not adsorb hydrogen strongly and to check the adsorption behavior of hydrogen and nitrogen by FTIR technique.1) Various Ru catalysts were synthesized from Ru_3 (CO)_<12>, various supports (MgO,CeO_2, A.C., Al_2O_3, etc.), and various promoters (CsOH,BaO,etc.). Ru cluster composed by six Ru atoms including one N atom at the center was also synthesized and supported on MgO.2) The structure of Ru Cluster was analyzed by EXAFS,XPS,XRD,TEM,etc.The size of cluster and average co-ordination number was calculated.3) Two types of adsorbed hydrogen (on-top and bridge) atom were observed by FTIR.Two types were observed on Ru/MgO,but on Ru/CeO_2 mainly on-top hydrogen was observed.4) Ammonia synthesis and kinetics were studied. Hydrogen poisoning was strong in Ru/MgO but weak on Ru/CeO_2. Ru/CeO_2 was found to become highly active when it was treated by hydrogen at 873K.