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A series of transition metal ion-doped TiO2composites were prepared by polyethyleneimine-assisted solvent-free self-assembly. Due to the similar electronegativity and ionic radius of Ti and Zr ions, the introduction of Zr element to TiO2can effectively improve its surface acidity and introduce more defect sites on the TiO2framework. As-fabricated Zr-doped TiO2nanocomposite exhibits the formation of Zr–Ti bond, strong surface acidity, connected mesoporous channels, and relatively high crystallinity. These remarkable properties contribute to its adsorption–oxidation–desulfurization capacity toward thiophene-type sulfides, which can remove 500 × 10‒6dibenzothiophene from the model fuel within 100 min at low reaction temperatures. The polymer-induced self-assembly method can reduce organic solvent usage, pollutant emissions, and energy consumption, which provides an efficient and practical way to prepare porous metal oxide-based catalysts in future.

Ce 0.9Pr 0.1O 2-δ, Ce 0.95Cu 0.05O 2-δ, and Ce 0.9Pr 0.05Cu 0.05O 2-δmixed oxides and pure CeO 2were prepared with a sol−gel method and were characterized by XRD, in situ Raman, and in situ DRIFTS techniques. The XRD results confirmed the formation of Ce−Pr−O solid solution. The Raman results indicated that a higher concentration of oxygen vacancies was obtained on the Pr-doped samples compared to the Ce 0.95Cu 0.05O 2-δand pure CeO 2samples. Surface chemical states of the Ce 0.9Pr 0.1O 2-δand Ce 0.9Pr 0.05Cu 0.05O 2-δmixed oxides were determined by in situ Raman spectroscopy, which indicated that the surfaces of the two mixed oxides were both close to oxidation state during the reaction, despite of the presence of reducing reactant CO in the gas mixture. The in situ DRIFTS results evidenced the chemisorption of CO in the Cu-containing samples. The catalysts were tested for CO oxidation, and it was found that the enhanced reactivity was closely related to the higher concentrations of the oxygen vacancies and the chemisorbed CO in the catalysts, due to the fact that the oxygen vacancies provide activation centers for O 2and the Cu +ions provide chemisorption sites for CO.

A Ce0.9Pr0.1O2-solid solution was prepared by a sol−gel method. Changes in microstructure of the solid solution under different atmospheres (O2, He, and H2) and temperatures were characterized by an in situ X-ray diffraction (XRD) technique. Raman peaks at 460 cm-1ascribed to the F2gvibration mode of CeO2in the fluorite structure and at 570 cm-1ascribed to oxygen vacancies in the solid solution were studied by in situ Raman spectroscopy using 785- and 514-nm excitation laser lines, providing bulk and surface information, respectively. With a 785-nm laser line, the A570/A460ratio reflecting the oxygen vacancies concentration increased under O2and He while it first increased and then decreased under H2with increasing temperature. With a 514-nm excitation laser line, the A570/A460ratio decreased with increasing temperature under all atmospheres. The growth of the A570/A460ratio under the 785-nm laser line was due to the positive effects of high temperature and high concentration of oxygen vacancies and the negative effect of reduction of the sample under reducing atmospheres (He and H2), while the decline in the A570/A460ratio under 514 nm was due to the dominant negative effect of the migration of surface Pr from surface to bulk during the heating process.

The phase transformation of γ-Al2O3 at high temperatures was characterized using X-ray diffraction (XRD) and fluorescence techniques. The results of a comparative fluorescence spectroscopic study of commercial and pure Al2O3 show that with laser excitation at 632.8 and 514.5 nm the absorption bands at 683.8 and 686.7 nm (R-line luminescence) are attributed to the presence of Cr3+ ions in octahedral coordination in a θ-Al2O3 environment. The other two bands at 692.8 and 694.4 nm (R2 and R1 lines) are attributed to Cr3+ fluorescence in an α-Al2O3 environment. Compared with XRD measurements, fluorescence spectroscopy has a higher sensitivity for identification of phase transformations in θ-Al2O3 and α-Al2O3. According to the different absorptions of Al2O3 with two laser excitations, the laser excitation at 514.5 nm is found to be more sensitive at the surface region while the laser excitation at 632.8 nm supplies information about the bulk. The fluorescence spectra together with UV–visible diffuse reflectance spectra and XRD patterns indicate that the γ-Al2O3 starts transforming to θ-Al2O3 and α-Al2O3 simultaneously at 800 °C. However, the θ-Al2O3 and α-Al2O3 compositions of the surface region and the bulk are different. The α-Al2O3 content at the surface region is higher than that in the bulk. The γ-Al2O3 sample transforms to α-Al2O3 completely at 1250 °C. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)