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

Catalytic activity and selectivity of boron phosphate in the decomposition of ethyl alcohol vapor

Hydroxyapatite of approximately stoichiometric composition ( Ca P molar ratio 1.65) evacuated at 600°C and exposed to O2 at room temperature produces ESR spectra with gxx = 2.0013, gyy = 2.0102 and gzz = 2.0160, providing evidence for the formation of O−2. Although the ESR signal attributed to Fs+ centers is observable on both nonstoichiometric apatite ( Ca P molar ratio 1.61) and the stoichiometric form, no change in the ESR signal of the former sample takes place after adsorption of oxygen at room temperature. The formation of O−2 suggests presence of O2− of low coordination in the stoichiometric form.

Formation of radical oxygen species on hydroxyapatite

Methylcyclopentane is ring‐expanded to cyclohexane and cyclohexane is ring‐contracted to methylcyclopentane on 12‐tungstophosphoric acid (HPW) supported on silica and on stoichiometric microporous silver 12‐tungstophosphate. The conversions of the two reactants increase with the loading of HPW on SiO2 while achieving significantly higher values on silver 12‐tungstophosphate which pass through a maximum as the Ag/H+ preparative ratio increases. The ring‐expansion and ring‐contraction processes on the supported HPW and the microporous AgPW are catalyzed by the acidic protons in the solid acid and the residual protons in the silver salt.

Ring-expansion of methylcyclopentane to cyclohexane and ring-contraction of cyclohexane to methylcyclopentane on silica-supported 12-tungstophosphoric acid and stoichiometric and nonstoichiometric microporous silver 12-tungstophosphate

An electron spin resonance study of oxygen radicals on hydroxyapatite

Heteropoly acids with anions of Keggin structure are ionic solids with protons distributed throughout their structure. These protons are often found with hydrogen-bonded water which may block access to incoming sorbates. Although the water can be removed the protons can only be thermally eliminated through the addition of anionic oxygen atoms to form water. Semiempirical (EXH) calculations, temperature-programmed desorption, exchange, and reduction, and infrared photoacoustic spectroscopy, the latter with ammonia and pyridine as probe molecules, have been employed to yield information on the protons and their environment in heteropoly compounds.

John B. Moffat

Papers

Catalytic activity and selectivity of boron phosphate in the decomposition of ethyl alcohol vapor

Formation of radical oxygen species on hydroxyapatite

Ring-expansion of methylcyclopentane to cyclohexane and ring-contraction of cyclohexane to methylcyclopentane on silica-supported 12-tungstophosphoric acid and stoichiometric and nonstoichiometric microporous silver 12-tungstophosphate

An electron spin resonance study of oxygen radicals on hydroxyapatite

Heteropoly Compounds: Solid Acids With Guarded Protons