Abstract
A series of La-promoted Ru/zeolite X catalysts (∼2 wt% Ru) was examined in the ammonia synthesis reaction at 20.7 atm total pressure. Results were compared with those reported previously for analogous Ba-promoted Ru/zeolites. Exchange of the zeolite cations with La3+ formed an Ru catalyst (Ru/LaX) that was superior to one exchanged with Ba2+ (Ru/BaX). Incorporation of La3+ and Ba2+ beyond ion-exchange capacity improved the turnover frequency on Ru/LaX and Ru/BaX, respectively. However, an La-promoted sample proved to be the most active. Interestingly, all of the La-containing catalysts exhibited a weak dependence of the rate on H2 whereas the Ba-loaded samples were strongly inhibited by the reactant. These results suggest that an appropriate choice of promoter might overcome the well-known inhibition on Ru catalysts by H2 without sacrificing high reactivity.
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Siporin, S.E., McClaine, B.C., Anderson, S.L. et al. Lanthanum Promotion of Ru/Zeolite X Catalysts for Ammonia Synthesis. Catalysis Letters 81, 265–269 (2002). https://doi.org/10.1023/A:1016501811975
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DOI: https://doi.org/10.1023/A:1016501811975