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En France, le régime d'indemnisation des catastrophes naturelles couvre depuis 1982 les principaux périls naturels (inondations, sécheresses géotechniques, tremblements de terre, submersions marines et cyclones dans les territoires d'Outre-Mer). Le groupe CCR (Caisse Centre de Réassurance) est un réassureur public, au cœur de ce dispositif, proposant une couverture illimitée aux assureurs avec garantie de l'État. Ainsi, CCR dispose d'une base de données presque exhaustive des données assurantielles à l'adresse et les restitutions sont effectuées à l'échelle communale. CCR développe depuis de nombreuses années des modèles d'exposition aux risques pour fournir une estimation rapide des dommages assurés notamment après la survenance d'un événement. Les indicateurs et analyses assurantielles telles que le coût moyen par sinistre, le ratio sinistres à primes S/P ont démontré que le ruissellement urbain a pour conséquence une sinistralité élevée en termes de montant de dommages. Dans leur ensemble, les inondations représentent 55 % de la sinistralité depuis 1982. Les sinistres consécutifs à des ruissellements représentent 22 % de la sinistralité totale en France pour la période 1995–2019. En termes de coût moyen, un sinistre en zone de ruissellement se situe aux alentours de 8 k€. À l'échelle d'un bassin versant urbanisé, les sinistres liés au ruissellement représentent 78 % de la sinistralité totale. Cet article propose une analyse détaillée des données et des indicateurs utilisés pour estimer la sinistralité due au ruissellement. Une compréhension fine de ces données permet d'anticiper et de garantir la solvabilité et pérennité du régime Cat Nat français.

En France, le régime d'indemnisation des catastrophes naturelles couvre depuis 1982 les principaux périls naturels (inondations, sécheresses géotechniques, tremblements de terre, submersions marines et cyclones dans les territoires d'Outre-Mer). Le groupe CCR (Caisse Centre de Réassurance) est un réassureur public, au cœur de ce dispositif, proposant une couverture illimitée aux assureurs avec garantie de l'État. Ainsi, CCR dispose d'une base de données presque exhaustive des données assurantielles à l'adresse et les restitutions sont effectuées à l'échelle communale. CCR développe depuis de nombreuses années des modèles d'exposition aux risques pour fournir une estimation rapide des dommages assurés notamment après la survenance d'un événement. Les indicateurs et analyses assurantielles telles que le coût moyen par sinistre, le ratio sinistres à primes S/P ont démontré que le ruissellement urbain a pour conséquence une sinistralité élevée en termes de montant de dommages. Dans leur ensemble, les inondations représentent 55 % de la sinistralité depuis 1982. Les sinistres consécutifs à des ruissellements représentent 22 % de la sinistralité totale en France pour la période 1995–2019. En termes de coût moyen, un sinistre en zone de ruissellement se situe aux alentours de 8 k€. À l'échelle d'un bassin versant urbanisé, les sinistres liés au ruissellement représentent 78 % de la sinistralité totale. Cet article propose une analyse détaillée des données et des indicateurs utilisés pour estimer la sinistralité due au ruissellement. Une compréhension fine de ces données permet d'anticiper et de garantir la solvabilité et pérennité du régime Cat Nat français.

Alkaline-earth phosphates efficient in the dehydration of lactic acid to acrylic acid were previously shown to contain a surface mono/dihydrogen phosphate amorphous layer composed of M2+cations and both P═O and POH groups. In this work, acidic properties of such a layer were determined combining Fourier transform infrared (FTIR) spectra achieved at the dehydrated state and under water vapor and density functional theory (DFT) simulations of nondefective and defective MPOH structure. The FTIR spectra of adsorbed pyridine and lutidine revealed the presence of moderate Lewis acid sites (LAS) and of POH groups interacting by H-bonding without significant protonation. DFT calculations were key to interpret FTIR spectra after adsorption of NH3: when solely adsorbed, NH3interacts with the LAS on both the nondefective surface and the defective surface, whereas the POH for which H points up toward the gas phase are reoriented downward. Brønsted acid sites (BAS) were shown to form under water vapor. This phenomenon was shown by DFT to arise from a more acidic character of HPO42–species for the nondefective surface and casual formation of nondefective surface leading to higher amount of H2PO4–species, which are more acidic BAS.

Combining neutron diffraction and classical molecular simulations, we describe the cation migration and associated structural changes taking place in a Ni-exchanged NaY faujasite zeolite upon stepwise dehydration from room temperature up to 400 °C. The cation redistribution between sites and the related framework deformations taking place upon water removal are identified and quantified. Neutron diffraction allows monitoring the zeolite structure, the average cation location and the water content, whereas molecular modeling provides insights into the correlations between the positions of cations and water molecules. Importantly, we demonstrate that the migration of Ni2+toward highly confined sites upon dehydration is the driving force behind deformation of the hexagonal prisms. The present work illustrates the relevance of combining these two experimental and theoretical approaches to clarify the complex interplay between cation hydration, cation location, and framework deformation. It also underlines the importance to capture the flexibility of the framework in molecular simulation of hydrated zeolite in particular when multivalent ions are involved.

In this study we report on a ZnxZryOzmixed oxide type catalyst capable of converting a syngas-derived C2+ mixed oxygenate feedstock to isobutene-rich olefins. Aqueous model feed comprising of ethanol, acetaldehyde, acetic acid, ethyl acetate, methanol, and propanol was used as representative liquid product derived from a Rh-based mixed oxygenate synthesis catalyst. Greater than 50% carbon yield to C3–C5mixed olefins was demonstrated when operating at 400–450 °C and 1 atm. In order to rationalize formation of the products observed feed components were individually evaluated. Major constituents of the feed mixture (ethanol, acetaldehyde, acetic acid, and ethyl acetate) were found to produce isobutene-rich olefins. C–C coupling was also demonstrated for propanol feedstock – a minor constituent of the mixed oxygenate feed – producing branched C6olefins, revealing scalability to alcohols higher than ethanol following an analogous reaction pathway. Using ethanol and propanol feed mixtures, cross-coupling reactions produced mixtures of C4, C5, and C6branched olefins. The presence of H2in the feed was found to facilitate hydrogenation of the ketone intermediates, thus producing straight chain olefins as byproducts. While activity loss from coking is observed complete catalyst regeneration is achieved by employing mild oxidation. For conversion of the mixed oxygenate feed a Zr/Zn ratio of 2.5 and a reaction temperature of 450 °C provides the best balance of stability, activity, and selectivity. X-ray diffraction and scanning transmission electron microscopy analysis reveals the presence of primarily cubic phase ZrO2and a minor amount of the monoclinic phase, with ZnO being highly dispersed in the lattice. The presence of ZnO appears to stabilize the cubic phase resulting in less monoclinic phase as the ZnO concentration increases. Infrared spectroscopy shows the mixed oxide acid sites are characterized as primarily Lewis type acidity. The direct relationship between isobutene production and the ratio of basic/acidic sites was demonstrated. An optimized balance of active sites for isobutene production from acetone was obtained with a basic/acidic site ratio of ∼2. This technology for the conversion of aqueous mixtures of C2+ mixed oxygenates provides significant advantages over other presently studied catalysts in that its unique properties permit the utilization of a variety of feeds in a consistently selective manner.

A CoSiBEA zeolite was obtained by a postsynthesis method which consisted of a treatment of tetraethylammonium BEA zeolite with nitric acid in the first step and introduction of Co ions into the vacant T atom sites of the SiBEA zeolite by reaction of aqueous Co(NO3)2solution with silanol groups. The introduction of Co into SiBEA zeolite as a isolated mononuclear Co(II) was evidenced by XRD, FTIR, diffuse reflectance UV–vis, and XPS. Brønsted and Lewis acidity of HAlBEA, SiBEA, and CoSiBEA zeolites were investigated by FTIR spectroscopy using pyridine as the probe molecule. Reducibility of cobalt in CoSiBEA zeolites was investigated by temperature-programmed reduction of H2. Dispersion of metallic cobalt nanoparticles was determined by transmission electron microscopy.

A MoSiBEA zeolite has been prepared by a two-step postsynthesis procedure that consists of first creating the vacant T-atom sites with associated silanol groups by treatment of TEABEA zeolite with nitric acid and then incorporating Mo ions into the vacant T-atom sites by solid-state ion exchange at 773 K using molybdenum(II) acetate. The incorporation of Mo ions into the vacant T-atom sites of the framework of SiBEA zeolite as isolated mononuclear Mo(VI) species was evidenced by the combined use of XRD and FTIR, NMR, and diffuse reflectance UV–visible spectroscopies. The consumption of OH groups was monitored by FTIR spectroscopy. The reducibility of Mo was investigated by TPR and EPR spectroscopy. The size of very small well-dispersed Mo(0) nanoparticles formed upon treatment of MoSiBEA between 298 and 1240 K in hydrogen stream (5% H2/Ar) was measured by TEM.

We explore the reactivity of inorganic monophosphate ions (Pi) and 5′-adenosine monophosphate (AMP), adsorbed onto amorphous silica separately or together. This question has relevance for prebiotic chemistry scenarios and, more generally, for biomedical applications involving biomolecule adsorption. XRD, TGA, and 31P and 29Si NMR results show that inorganic phosphate ions deposited on silica condense to polyphosphates at considerably lower temperatures than in bulk KH2PO4. In the same temperature range, AMP adsorbed alone undergoes dismutation reactions, yielding adenosine, ADP, and ATP; in this case, the effect of the silica surface is not obvious. When AMP and Pi are coadsorbed on silica at high loadings (5–10%), AMP dismutation and phosphorylation by Pi both occur, allowing the formation of ADP and ATP. The latter result clearly shows the ability of silica surfaces to promote the formation of molecules generally considered as “high-energy” compounds and opens the way to further research on the effect of mineral surfaces for nucleotide synthesis and ribose stabilization.

We report here on the adsorption and deposition of l-glutamic acid (Glu) on an amorphous silica and its subsequent thermal transformations. When adsorbed from aqueous solutions, Glu only has a low affinity for the silica surface but at high concentrations the adsorbed molecules serve as nuclei for the formation of small glutamic acid crystallites. As long as the Glu loading remains inferior to a saturation limit (about 0.5 molecule nm–2), the thermal behavior of adsorbed Glu is significantly different from that of bulk glutamic acid. Two successive condensation steps are observed upon mild thermal activation, and their products have been identified by a combination of techniques including thermogravimetry, in situ IR, solid-state NMR, and ESI-MS. The first step at about 120 °C is a lactam ring closure quantitatively yielding pyroglutamic acid in a first-order reaction. The second step, at 150 °C, probably results in the formation of a highly activated tricyclic imide, PyroGluDKP, and is easily reversible in the presence of water. These reactions have implications for prebiotic peptide formation and for synthetic chemistry.

Evidence is shown of the appearance of Brønsted acidic sites in WO_x/ZrO₂ at a given W loading and of a direct correlation between the abundance of ‘strong’ Brønsted acidic sites in these catalysts and propan-2-ol decomposition activity.