Study of CeO2-ZrO2 solid solution promoters modified by Nd

An external layer containing Nd3+ to inhibit the sintering of the nanosized CeO2-ZrO2 solid solution was suggested. During calcination of this kind of double layer materials at 500 similar to 850 degreesC part of the Nd3+ dif fuses into the lattice of CeO2-ZrO2 and the rest remains on the external su rface of the nanosized CeO2-ZrO2. Then the segregation of Nd3+ on the surfa ce is resulted. It may prevent from moving of the crystal bound and growing up of the crystal grain, thereby alleviate the sintering of the nanosized CeO2-ZrO2 particles and improve the catalytic performance of the catalysts containing this kind of promoters.; Two methods were used to dope the ions of Nd3+ into the CeO2-ZrO2 solid solution. For the first route, the ultrafi ne CeO2-ZrO2 was impregnated with neodymium. nitrate and neodymium-zirconiu m. nitrate sol to form the protection layer, Nd2O3 and Nd0.1Zr0.9O2, respec tively. For the second route, the homogeneous ultrafine solid solution of C e0.65Zr0.25Nd0.10O2 Was prepared by the modified sol-gel method. The, surfa ce area and oxygen storage capacity of all the samples at 200 degreesC were measured, and some samples were characterized by XRD and H-2-TPR. It was s howed that the samples which were modified by the first route possess highe r ability to resist the sintering than those modified by the second one, an d the optimum Nd content is 7%. The TWCs (three-way catalysts) containing l ow content of precious metals (Pt, Pd and Rh) were also prepared. The suppo rts were prepared by mixing gamma -Al2O3 with the CeO2-ZrO2 solid solutions or with the modified CeO2-ZrO2 containing Nd3+. It was showed that the lig ht-off temperatures of all the fresh TWCs containing (Ce-Zr-Nd)O-2 reduced by 20 similar to 30 degreesC than those of the TWCs with the unmodified sup ports. However, the improvement of the light-off temperatures is not obviou s for the aged TWCs (calcined at 850 degreesC for 2 h) with modified suppor ts containing Nd3+.