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A series of porous CeO 2 –CrO x mixed oxides are synthesized using different precipitants (NaOH, NH 4 OH, (NH 4 ) 2 CO 3 and urea) and evaluated for deep oxidation of various chlorinated VOCs (CH 2 Cl 2 , C 2 HCl 3 , C 2 H 4 Cl 2 and C 6 H 5 Cl). The results show that all these materials represent porous structures and small particle sizes (2–8 nm). Part of Cr element can go into the lattice of CeO 2 , resulting in the formation of Ce–Cr–O mixed oxide. Compared with pure CeO 2 and Cr 2 O 3 , the amount of Cr 6+ species and oxygen vacancies in CeO 2 –CrO x mixed oxides are significantly increased, due to the strong interaction between CeO 2 and CrO x . Thus, all the CeO 2 –CrO x mixed oxides exhibit high catalytic activity and good durability for deep oxidation of chlorinated VOCs, especially the CeO 2 –CrO x prepared using (NH 4 ) 2 CO 3 as precipitant. Moreover, only slight chlorinated byproducts are detected in the process of chlorinated VOCs oxidation, and the surface accumulation of coke and Cl species as well as the loss of Cr element is slight during the long-term reaction at 265 °C, indicating that these CeO 2 –CrO x materials possess interesting fundamental result, deserving more research before conclusion on practical value. [ABSTRACT FROM AUTHOR]

(Ce,Cr) x O 2 /MO y (M = Ti, V, Nb, Mo, W, La, respectively) mixed oxides are synthesized by deposition-precipitation method, and evaluated for total oxidation of gaseous 1,2-dichloroethane, a typical chlorinated organic pollutant. The characterization results show that there exists strong metal-support interaction or synergistic effect between (Ce,Cr) x O 2 and MO y . The catalytic performances of these catalysts can be related to the nature of each MO y support, the crystal structure and composition, the surface elements distribution and the diverse redox properties of (Ce,Cr) x O 2 /MO y . The improved redox property, as well as the increased content of Ce 3+ and Cr 6+ species on the surface can enhance the catalytic performances of the catalysts. Especially, (Ce,Cr) x O 2 /Nb 2 O 5 exhibits the best catalytic performance. (Ce,Cr) x O 2 /Nb 2 O 5 also represents high durability for 1,2-dichloroethane oxidation during the long-term continuous test. Moreover, though the presence of water or benzene in the reaction system slightly suppresses 1,2-dichloroethane oxidation, the catalytic activity can be recovered by the cut of water, while a little deactivation is found if benzene is removed away, since coke has been deposited on the catalyst surface by the combustion of benzene. [ABSTRACT FROM AUTHOR]

Cerium-transition metal mixed oxides (4Ce1M, M = V, Cr, Mn, Fe, Co, Ni and Cu) were prepared by coprecipitation method and investigated for deep oxidation of four chlorinated VOCs with quite different molecule structures. 4Ce1M catalysts show mesoporous structures with larger specific surface area and pore volume, and some metal ions can go into the lattice of fluorite, which contributes to improving the stability of the active components. The redox properties of 4Ce1M catalysts are significantly promoted due to the strong interaction between CeO 2 and MO x , which facilitates the destruction of the reactants and byproducts at lower temperature in the process of CVOCs oxidation. Especially, 4Ce1Cr catalyst exhibits the best catalytic activity and selectivity, mainly due to the formation of Cr 6+ species with strong oxidizing ability. 4Ce1Cr also represents good durability for DCE destruction during the 100 h continuous test, and the chemical adsorbed Cl species on the surface can be removed above 325 °C. Moreover, the presence of water or non-chlorinated VOCs can slightly decrease the conversion of chlorinated VOCs at lower temperature due to the competitive adsorption for active sites, while promote at higher temperature (above 300 °C) because of the contribution to removing Cl species away from the surface. [ABSTRACT FROM AUTHOR]