/pdf/the-surface-chemistry-of-amorphous-silica-zhuravlev-model-4kfs2lx66q.pdf

The surface chemistry of amorphous silica. Zhuravlev model

The review is a summary and analysis of the data characterizing CO adsorption on surface cationic sites of oxides including supported materials and microporous and mesoporous materials. The contributions of various types of CO bonding to the IR frequency shifts of carbon-bonded molecules are analyzed, namely, the increase of the CO stretching frequency in cases of electrostatic and σ bonding and the decrease of the frequency with π bonding. Polycarbonyls, bridging CO, oxygen-bonded CO, and tilted CO are also considered. The main part of the review is a collection of the experimental results characterizing carbonyls of individual metal ions. The spectral behavior of CO bonded to metal atoms is also assessed in the cases when the metal ions are easily reduced to metal (Cu, Ag, Au, Pd, or Pt) or cationic carbonyls are produced after CO adsorption on supported metals (Ru, Rh, Ir, and Os). The interaction of CO with surface OH groups is also considered. It is demonstrated that IR spectroscopy of adsorbed CO is an efficient methodology to characterize cationic surface sites in terms of their nature, oxidation states, coordination environment and coordinative unsaturation, and location at faces, edges or corners of microcrystallites. When applied to materials with surface hydroxyl groups CO undergoes hydrogen bonding and information can be collected on the proton acid strength.

Characterization of oxide surfaces and zeolites by carbon monoxide as an IR probe molecule

Silica Surface Features and Their Role in the Adsorption of Biomolecules: Computational Modeling and Experiments / Albert Rimola;Dominique Costa;Mariona Sodupe;Jean-François Lambert;Piero Ugliengo. In: CHEMICAL REVIEWS. ISSN 0009-2665. STAMPA. 113:6(2013), pp. 4216-4313. Original Citation: Silica Surface Features and Their Role in the Adsorption of Biomolecules: Computational Modeling and Experiments

/pdf/silica-surface-features-and-their-role-in-the-adsorption-of-2hhuc04ksj.pdf

Silica Surface Features and Their Role in the Adsorption of Biomolecules: Computational Modeling and Experiments

Chemistry of zirconia and its use in chromatography

This critical review describes the reactivity of heterogeneous catalysts from the point of view of four simple, but essential for Chemistry, molecules (namely dihydrogen, carbon monoxide, nitrogen monoxide and ethylene) that are considered as probes or as reactants in combination with “in situ” controlled temperature and pressure Infrared spectroscopy. The fundamental properties of H2, CO, NO and C2H4 are shortly described in order to justify their different behaviour in respect of isolated sites in different environments, extended surfaces, clusters, crystalline or amorphous materials. The description is given by considering some “key studies” and trying to evidence similarities and differences among surfaces and probes (572 references).

/pdf/probing-the-surfaces-of-heterogeneous-catalysts-by-in-situ-2mmpzxpkqu.pdf

Probing the surfaces of heterogeneous catalysts by in situ IR spectroscopy

The reactivity of oxides with water vapor

The reactivity of oxides with water vapor Solid State Ionics

Microcrystalline La2O3 outgassed at 873 K has a UV absorption edge centred at ca. 250 nm on which absorption ascribable to surface states is superimposed. This latter absorption is diminished by CO2 adsorption, which produces surface carbonate. UV reflectance and IR results with CO are correlated to show that CO adsorption on the outgassed oxide occurs with rapid formation of carbonite CO22– ions, accompanied at room temperature by a slow reaction forming reduced oligomeric (CO)n2– anions and carbonate CO32–. The reaction stages have been resolved by extending the UV and IR measurements to low temperatures. CO22–, identified by UV absorption at 340 nm and IR bands at 1390 and 987 cm–1, is the only process occurring at 90 K. As the temperature is increased, the ketenic dimer anion C2O32– is formed, characterized by a UV band at 300 nm and IR bands at 2075 and 1367 cm–1. The onward disproportionation producing reduced oligomers and carbonates gives a complex IR spectrum in the 1700–1000 cm–1 range. The bands due to the oligomers are readily discriminated by their sensitivity to oxygen. The discussion illustrates that UV and IR spectroscopy afford a powerful combination in defining and understanding the stages involved in the adsorption and reaction of CO on lanthanum oxide. The nature and extent of the reactivity towards CO shows that the basicity of La2O3 is not as great as that of the alkaline-earth-metal oxides.

UV reflectance and FTIR spectroscopic studies of CO adsorption and reaction on lanthanum oxide

Heterogeneity of V2O5/Al2O3 as studied by water vapour adsorption microcalorimetry

The heat evolved during the adsorption and oligomerization of CO on outgassed CaO and MgO has been determined with a heat-flow calorimeter. The chemisorbed complexes formed include highly-conjugated (CO)
 n
 2
 anions which impart colour to the oxides. The reaction of these complexes with oxygen has been quantified calorimetrically and correlated with changes observed spectroscopically.

Michael Bailes

Papers

The reactivity of oxides with water vapor

The reactivity of oxides with water vapor Solid State Ionics

UV reflectance and FTIR spectroscopic studies of CO adsorption and reaction on lanthanum oxide

Heterogeneity of V2O5/Al2O3 as studied by water vapour adsorption microcalorimetry

The reaction of oxygen with CO complexes on calcium oxide and magnesium oxide