Over the past several years, cerium oxide and CeO2-containing materials have come under intense scrutiny as catalysts and as structural and electronic promoters of heterogeneous catalytic reactions. Recent developments regarding the characterization of ceria and CeO2-containing catalysts are critically reviewed with a special focus towards catalyst interaction with small molecules such as hydrogen, carbon monoxide, oxygen, and nitric oxide. Relevant catalytic and technological applications such as the use of ceria in automotive exhaust emission control and in the formulation of SO x reduction catalysts is described. A survey of the use of CeO2-containing materials as oxidation and reduction catalysts is also presented.

Catalytic Properties of Ceria and CeO2-Containing Materials

http://www1.udel.edu/chem/polenova/PDF/Polyoxometalates/POMs_Catalysis_NMR_ChemRev1998.pdf

Catalysis by Heteropoly Acids and Multicomponent Polyoxometalates in Liquid-Phase Reactions

https://web.iitd.ac.in/~arunku/files/CEL311_Y13/Adsorption%20Theory%20to%20practice_Dabrowski.pdf

Adsorption — from theory to practice

ion from a primary OH group of glyc-erol. 223,231 A similar mechanism was proposed manyyears ago for alcohol oxidation on Pt/C, involving asecond step, the transfer of a hydride ion to the Ptsurface (Scheme 11). 8,87,237 We consider it more feasible that the rate-deter-mining step is the cleavage of the C-H bond at theR-carbon atom. A similar mechanism is now generallyaccepted for Au electrodes (Scheme 12). 238 Despite thestructural differences between Au nanoparticles andan extended Au electrode surface, there are alsosimilarities, such as the critical role of aqueousalkaline medium and the absence of deactivation dueto decomposition products (CO and C x H y frag-ments). 239,240 An important question is the nature of active siteson Au nanoparticles. Electrooxidation of ethanol onAu nanoparticles supported on glassy carbon re-quired the partial coverage of Au surface by oxides. 241 Another analogy might be the model proposed for COoxidation. 219,242,243 According to this suggestion, theactive site consists of an ensemble of metallic Auatoms and a cationic Au

Oxidation of Alcohols with Molecular Oxygen on Solid Catalysts

The infrared spectral performance of the N x O y species observed on oxide surfaces [N2O, NO−, NO, (NO)2, N2O3, NO+, NO2 − (different nitro and nitrito anions), NO2, N2O4, N2O5, NO2, and NO3 − (bridged, bidentate, and monodentate nitrates)] is considered. The spectra of related compounds (N2, H-, and C-containing nitrogen oxo species, C─N species, NH x species) are also briefly discussed. Some guidelines for spectral identification of N x O y adspecies are proposed and the transformation of the nitrogen oxo species on catalyst surfaces are regarded.

Identification of Neutral and Charged N x O y Surface Species by IR Spectroscopy

Tetrachloromethane (TCM) has been decomposed under methane oxidation conditions on calcium hydroxyapatite (CaHAp). Although TCM is stable at 773 K in the absence of a catalyst, it is completely decomposed at the same temperature in the presence of CaHAp. The preponderance of the chlorine resulting from the decomposition appears as methyl chloride and hydrogen chloride with the remainder trapped in CaHAp. During the decomposition the CaHAp was initially converted to calcium chlorapatite and ultimately to calcium chloride with concomitant changes in the selectivities but not the conversion of TCM. The decomposition of TCM is strongly influenced by the PO 4 groups and the oxidation of methane by the OH groups in CaHAp.

Decomposition of tetrachloromethane on calcium hydroxyapatite under methane oxidation conditions

The oxidation of iodide to iodine on boron phosphate

The oxidation of propane on nonstoichiometric calcium hydroxyapatites has been investigated in the presence and absence of tetrachloromethane (TCM) at 723 K. In the absence of TCM, the principal products were CO and CO 2 and the selectivity to propylene was found to depend on the stoichiometry. On addition of TCM to the feedstream, it was generally observed that the conversion of propane and the selectivity to CO 2 decreased with increasing time-on-stream, while the selectivity to propylene increased. Both the conversion and selectivities were dependent upon the partial pressure of TCM in the feedstream, the stoichiometry and time-on-stream. The role of chlorinated species is discussed.

The oxidation of propane on nonstoichiometric calcium hydroxyapatites in the presence and absence of tetrachloromethane

Oxidative coupling of methane over thallium based silica supported catalysts

The oxidative coupling of methane has been studied on Mg, Ca, Sr and Ba sulphate. The conversions and selectivities are found to be dependent on the nature of the cation and to be approximately correlated with their electronegativities, thus implying that the C-H bond scission in CH4, at least with these catalysts, is heterolytic, is rate determining, and further, that the formation of C2+ hydrocarbons is dependent, among other factors, on the concentration of methyl radicals.

John B. Moffat

Papers

Decomposition of tetrachloromethane on calcium hydroxyapatite under methane oxidation conditions

The oxidation of iodide to iodine on boron phosphate

The oxidation of propane on nonstoichiometric calcium hydroxyapatites in the presence and absence of tetrachloromethane

Oxidative coupling of methane over thallium based silica supported catalysts

Cation effects in the oxidative dehydrogenation of methane on sulphates