Influence of high temperature treatments under net oxidizing and reducing conditions on the oxygen storage and buffering properties of a Ce0.68Zr0.32O2 mixed oxide

Preparation of CexZr1−xO2 (x=0.75, 0.62) solid solution and its application in Pd-only three-way catalysts

“…It was noticed that both CZ75 and CZ62 showed lower total H 2 uptake after calcination at 900 8C for 6 h in our experiments. It indicates that the treatment condition can influence the reduction properties of Ce x Zr 1Àx O 2 dramatically, which is in agreement with the results of Vidal et al [22].…”

“…Vidal et al [22] have found that the oxygen storage capacity of Ce 0.68 Zr 0.32 O 2 can be improved after being aged in H 2 , and OSC increases significantly with increasing the treatment temperature. Nagai et al [24] have reported that the surface area of Ce 0.5 Zr 0.5 O 2 decreases from 89 to 1 m 2 /g after severe reduction treatment, however its OSC increases from 9.9 to 1500 mmol-O/m 2 .…”

Sol–Gel Synthesis of Tunable Cerium Titanate Materials

“…Assuming the same considerations stated above, we can estimate that the percentage of paramagnetic Ce 3+ centres in the samples treated at 1000 °C/3 h H 2 (not shown) is about 20%, which leads to a formula of Ce 2 Ti 2 O 7.8 . Nevertheless, the observed roomtemperature χmT product for samples treated at 1200 °C/H2 for 3 and 6 h is 0.53 and 0.58 cm 3 mol -1 K, respectively, which is somewhat higher than the previously cited value of 0.52 cm 3 mol -1 K. [51,52] These results could be understood by considering that all the cerium is in the trivalent state and that there is some additional contribution due to the presence of small amounts of titanium also in the trivalent state. In an approximate analysis, by considering the d1 configuration of Ti 3+ and the expected spin-only contribution to paramagnetism, we could estimate a percentage of 2 and 16% of trivalent titanium in those samples, which leads to compositions of Ce 2 Ti 2 O 6.98 and Ce 2 Ti 2 O 6.84 , respectively.…”

“…From the EPR data we can assume that paramagnetism is due only to Ce 3+ and hence the decrease of the χ m .T product when lowering the temperature is easily understood by the depopulation of the higher energy Kramer's doublets arising from the crystal field splitting of the ground state of the lanthanide ion, 2 F 5/2 , as observed in most of Ce(III) compounds. [49] Nevertheless, the observed χ m .T product at room temperature is lower than that expected for the free ion of 0.79 or the observed in Ce 2 O 3 of 0.52 cm 3 mol -1 K. [51,52] That last value has been used by several authors [50][51][52][53] According to the obtained results it was concluded that N 2 /glucose atmosphere is not reductive enough to avoid the oxidation of Ce(III). Thus, a more energetic reductor agent such as H 2 was tested.…”

Effect of mileage on the deactivation of vehicle-aged three-way catalysts

“…The results concerning the effect of thermal aging on the amount of Ce 4+ that can be reduced in TPR experiments are controversial: no effect or a depletion of the amount of Ce 4+ that can be reduced have been both reported in thermally aged Ce-Zr mixed oxide [22,26,27,[36][37][38].…”