Modification of cerium oxide with different dopants and synthesis methods
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Examensarbete för masterexamen
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Cerium oxide has many applications as a reducible oxide. In this paper, different
dopants (Sm, Fe, Pt, and Rh) and synthetic methods were used to modify ceria
to obtain metal-doped ceria with high specific surface area and high homogeneity.
For different synthesis methods, different parameters that may have affect on the
specific surface area were also investigated. The synthesized oxides were characterized
employing N2-physisorption, XRD, etc. to compare the surface area, crystal
structure, and purity. The results showed that different synthesis methods have the
greatest influence on the specific surface area, and the co-precipitation method is
better than the citric acid method or the modified Pechini method in synthesizing
oxides with high specific surface area. In the co-precipitation method, the choice of
precipitant also played a role. Among the precipitants tested in this project (ammonia,
urea and sodium hydroxide), sodium hydroxide performs best in getting high
surface area. Citric acid and Modified Pechini method performed better in obtaining
more homogeneous samples.
Two typical doped ceria synthesised by sodium hydroxide method were selected as
carriers (Ce0.8Sm0.2O1.9, Ce0.8Fe0.2O1.9), and the catalysts were prepared by supporting
metal Rh. The catalysts were characterized by N2-physisorption and COchemisorption
to get the information about specific surface area and metal dispersion
and size. Finally, the performance of the catalysts in the CO2 methanation reaction
was tested and compared with Rh/ceria catalysts with Rh weight percentage of 1,
2, 3 wt.% and doped Rh cerium oxides with Rh content of 0.5, 2.5, 5.5 wt.%.
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Ämne/nyckelord
Cerium Oxide, Dopant, Co-precipitation, Citric Acid Method, Modified Pechini Method, CO2 Hydrogenation