Effect of La2O3 on Ru/CeO2-La2O3 Catalyst for Ammonia Synthesis

Abstract

A series of CeO 2 -La 2 O 3 supported ruthenium catalysts were prepared by co-precipitation method and the as-obtained samples were characterized by N 2 physisorption, X-ray diffraction, CO chemisorption, H 2 -TPR, H 2 -TPD and XPS. The activity test shows that ammonia concentration of the catalyst with 10% La is 13.9% at 10 MPa, 10,000 h -1 , 450°C, which is 17% higher than that of Ru/CeO 2 . La doping can improve the activity of Ru-ceria catalyst for ammonia synthesis by facilitating the reduction of oxygen which subsists in the cerium oxide surface. In addition, it can be realized that the test of catalyst stability proves the stability performance of Ru/CeO 2 -La 2 O 3 catalyst within the reaction time of 55 h.

Highly stable, mesoporous mixed lanthanum–cerium oxides with tailored structure and reducibility

“…The mesoporous character of the materials is confirmed by BET, as seen in the typical type IV isotherms with H2 hysteresis shown in Figure 2 (top, a and b). The surface area of the lanthana is close to 60 100 m 2 /g after calcination at 450 °C (see Table 1), well in excess of previously reported surface areas of less than 30 m 2 /g 30,31 . XRD shows that the sample is largely amorphous after calcination at 450 °C (Figure 2 (Table 1), which can be attributed to the small particle size attributed to agglomerates of spheres with roughly uniform size, resulting in narrow pore size distributions 34 .…”

Hydrogen production by steam reforming of ethanol over Co3O4/La2O3/CeO2 catalysts synthesized by one-step polymerization method

“…Luo et al [58] also studied the reduction of Ce(La)O x solid solutions and found that the reduction of surface capping oxygen of ceria is located at intervals of 250-400 • C and the bulk oxygen of ceria is located at 450-700 • C. Similar findings were reported by Li et al [28] for Ni/CeO 2 -La 2 O 3 and Cu/CeO 2 -La 2 O 3 catalysts. The difference in the reduction temperature of these supports in comparison with the support of the present paper may be related to the preparation method.…”

“…3a shows the TPR profile of the CeO 2 , Ce 4 La, Ce 8 La and Ce 12 La supports, where it can be observed that the reduction peak located at 550 • C in CeO 2 (peak related to surface-capping oxygen of CeO 2 ) is shifted to lower temperature, after addition of La 2 O 3 . This finding suggests that this displacement is due to the solid solution Ce(La)O x formed [58,61,28].…”

“…In the profiles of Fig. 4 is clear that the major part of Ce is as Ce 4+ , only little peaks related to Ce 3+ can be observed (v 1 3 and u 1 3 ), owing to the low resolution of the Ce 3d spectra [58,63]. Moreover, the peak located at 916.8 eV (name as u 3 4 , related to Ce 4+ ) present in sample CoCe, shifted slightly to lower energy values (916.3 eV) in samples containing La (Fig.…”

“…The TPR profile for pure CeO 2 shows two characteristic peaks which correspond to the reduction of ceria (H 2 + 2CeO 2 → Ce 2 O 3 + H 2 O) in different environments (Fig. 3a) [55][56][57][58]. The first peak is around 550 • C, related to the reduction of the surface-capping oxygen of CeO 2 , and the second at 890 • C is related to the reduction of bulk oxygen of CeO 2 , both reductions correspond to non-stoichiometric CeO 2−x .…”