B. Azambre

IR study of adsorption and decomposition of propan-2-ol on carbon and carbon-supported catalysts

The aim of this research is to get information on the character of the interactions between propan-2-ol on the one hand and carbons which differs in the chemical structure of their surfaces or carbon-supported metal catalysts (Pt, Ag, Cu, Ni) on the other hand. The adsorption and decomposition of propan-2-ol were investigated with in situ infrared spectroscopy. Parallel to the FTIR studies, catalytic tests were performed in a fixed bed flow reactor. Prior to impregnation the unoxidized carbon sample exhibits very low catalytic activity in the propan-2-ol decomposition while the oxidized surface of carbon, especially of a metal containing carbon, effectively promotes the propan-2-ol decomposition. Although both dehydrogenation and dehydration processes take place simultaneously, our data indicate that the decomposition of propan-2-ol proceeds mainly through dehydrogenation.

Contributions of surface and bulk heterogeneities to the NO oxidation activities of ceria–zirconia catalysts with composition Ce0.76Zr0.24O2 prepared by different methods

The study of the catalytic activity towards NO oxidation to NO(2) was approached by using ceria-zirconia mixed oxides with the same nominal composition (Ce(0.76)Zr(0.24)O(2)) but prepared by different routes of synthesis: coprecipitation, solid combustion synthesis with urea, citrate complexation route, reversed microemulsion and template synthesis. The characterisation of the catalysts was performed by N(2) adsorption at -196 °C, XRD, Raman Spectroscopy, H(2)-TPR and XPS in order to ascertain the relationships between their catalytic activities and their bulk and surface properties. The results showed that the preparation method is critical for the physico-chemical properties of the mixed oxides, exhibiting very different BET surface areas, crystalline phase/s contributions and bulk oxygen mobility. The distribution of Ce and Zr on the surface with regard to the bulk is very much influenced by the preparation method as well. The NO(2) production from NO oxidation was shown to be mostly correlated with the Ce/Zr surface atomic ratio and the proportion of Ce(4+) (presumably in a doped cubic phase) in the uppermost layers.

IR study of the adsorption and decomposition of methanol on carbon surfaces and carbon-supported catalysts

Interactions between methanol and the carbon-supported catalysts have been investigated by in situ infrared spectroscopy. The pure, nonoxidized carbon itself is unreactive in decomposition of methanol. FTIR spectra showed that methanol adsorbed molecularly on oxidized carbon surface dissociated upon heating. Methoxy species generated by dissociative methanol adsorbed on oxidized carbon surface decompose to formaldehyde. The methanol decomposition leaves adsorbed methoxide, formaldehyde and CO on the surface of oxidized carbon containing Cu. IR spectroscopic results indicate the difference in the catalytic functions of Cu and Ni in dehydrogenation of methanol.

Evaluation of Silver Zeolites Sorbents Toward Their Ability to Promote Stable CH3I Storage as AgI Precipitates

In this study, up to 13 different silver zeolites sorbents were prepared by repeated ion exchange from their parent structures (FAU X and Y, MOR, *BEA, MFI, FER), characterized, and evaluated for their ability to capture methyl iodide in the context of a nuclear severe accident. A novel methodology was implemented to establish structure-activity relationships between sorbent properties and iodine trapping stability. After saturation of the zeolite bed with CH3I during a dynamic breakthrough experiment at 100 °C, a two-step quantitative desorption method was elaborated with the aim to quantify separately the CH3I fractions trapped by physisorption, chemisorption, or reacted as AgI precipitates. Besides, an analysis of the mechanisms involved in CH3I sorption and decomposition processes was also carried out. Overall, Ag/Y zeolites displayed the highest fractions trapped as stable AgI precipitates, thanks to the presence of high amounts of dispersed silver species at accessible locations in the large supercages, and their low sodium content.