La₂Ce₂O₇ supported ruthenium as a robust catalyst for ammonia synthesis

Wenfeng Han，Zhi Li，Huazhang Liu

Institute of Industrial Catalysis, Zhejiang University of Technology

摘 要：La₂Ce₂O₇ nanoparticles were prepared by citric acid complexation method followed by calcination at varied temperatures. Then, supported with 4 wt% Ru, they were evaluated as the catalysts for ammonia synthesis under conditions similar with industry. With La₂Ce₂O₇ being calcinated at 700 or 800℃, the experimental results indicate that the Ru/La₂Ce₂O₇ catalyst exhibits much higher ammonia concentration or ammonia synthesis rate than that of Ru/CeO₂ and Ru/La₂O₃. In addition, Ru/La₂Ce₂O₇ possesses high stability under over-heating test. In the absence of any promotor, ammonia concentration of Ru/La₂Ce₂O₇ catalyst approaches 14% at 450℃, GHSV of 10000 h^-1 and pressure of 10 MPa. The rate-determining step of ammonia synthesis, dissociation of N₂ is significantly facilitated by the strong metalesupport interaction（SMSI） between Ru and La₂Ce₂O₇. Due to the interaction, La₂Ce₂O₇ tends to donate electrons to Ru,resulting in the high electron density over the surface of Ru active sites which is favorable for the dissociation of N₂. Consequently, high activity is achieved.

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