La2Ce2O7 supported ruthenium as a robust catalyst for ammonia synthesis

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 degrees C, 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 degrees C, GHSV of 10000 h(-1) and pressure of 10 MPa. The rate-determining step of ammonia synthesis, dissociation of N-2 is significantly facilitated by the strong metal-support 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 N-2. Consequently, high activity is achieved. (C) 2019 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.