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Magnesium silicates combining acidic and basic surface properties are known to be interesting as heterogeneous catalysts. Nevertheless, their catalytic performances are highly dependent on the synthesis method used. In this study, a series of magnesium silicates was synthesized for the first time using a coprecipitation method with a micromixer. It is first shown that changes in synthesis/precipitation pH led to magnesium silicates with different Mg/Si ratios: the higher the synthesis pH, the higher the Mg/Si ratio. Moreover, prepared silicates with a final Mg/Si ratio greater than 0.7, thus prepared at high pH, exhibit negligible specific surface area, whereas relatively high values (>180 m2/g) have been obtained for lower Mg/Si ratios. A set of experimental characterization data obtained by N2 physisorption, SEM, XRD, TGA-DTA as well as Raman and 29Si NMR spectroscopies are presented and discussed. They show the existence of two distinct families with a similar Magnesium Silicate Hydrate (MSH) phase, but they reveal different aggregation states and textural properties. Finally, the surface acid–base reactivity of the co-precipitated magnesium silicates was determined using the model reaction of 2-methylbut-3-yn-2-ol (MBOH) conversion. The results obtained suggest that it is possible to prepare silicates with a wide range of surface acid–base properties, from purely basic solids to those with both acidic and basic properties, by adjusting the final Mg/Si ratio via the control of the synthesis parameters. [ABSTRACT FROM AUTHOR]

Orange carotenoid protein (OCP) is a photochromic carotenoprotein involved in the photoprotection of cyanobacteria. It is activated by blue-green light to a red form OCPR capable of dissipating the excess of energy of the cyanobacterial photosynthetic light-harvesting systems. Activation to OCPR can also be achieved in the dark. In the present work, activation by pH changes of two different OCPs—containing echinenone or canthaxanthin as carotenoids—is investigated in different conditions. A particular emphasis is put on OCP encapsulated in SBA-15 mesoporous silica nanoparticles. It is known that in these hybrid systems, under appropriate conditions, OCP remains photoactive. Here, we show that when immobilised in SBA-15, the OCP visible spectrum is sensitive to pH changes, but such a colorimetric response is very different from the one observed for OCP in solution. In both cases (SBA-15 matrices and solutions), pH-induced colour changes are related either by orange-to-red OCP activation, or by carotenoid loss from the denatured protein. Of particular interest is the response of OCP in SBA-15 matrices, where a sudden change in the Vis absorption spectrum and in colour is observed for pH changing from 2 to 3 (in the case of canthaxanthin-binding OCP in SBA-15: λMAX shifts from 454 to 508 nm) and for pH changing from 3 to 4 (in the case of echinenone-binding OCP in SBA-15: λMAX shifts from 445 to 505 nm). The effect of temperature on OCP absorption spectrum and colour (in SBA-15 matrices) has also been investigated and found to be highly dependent on the properties of the used mesoporous silica matrix. Finally, we also show that simultaneous encapsulation in selected surface-functionalised SBA-15 nanoparticles of appropriate fluorophores makes it possible to develop OCP-based pH-sensitive fluorescent systems. This work therefore represents a proof of principle that OCP immobilised in mesoporous silica is a promising system in the development of colorimetric and fluorometric pH and temperature sensors. [ABSTRACT FROM AUTHOR]

This study describes the use of novel Cu/ZnO/ZnAl2O4/PAAH (PAAH=polyacrylic acid) hybrid nanomaterials for glycerol hydrogenolysis. Their elaboration by sol‐gel process either in one step or in two steps allowed to modulate their structural properties in terms of specific surface area, Lewis acidity, sizes and dispersion of copper nanoparticles. The presence of PAAH and aluminium during the synthesis particularly showed benefits in terms of dispersion and metal‐support interaction. The characterization of the catalyst surfaces in composition and size of the copper nanoparticles allowed to establish structure‐reactivity relationships. Their optimization allowed to reach remarkable conversions up to 96 % with selectivity towards 1,2‐propanediol of 83 %. A recyclability study also showed a possible reuse of these catalysts after a reactivation step. [ABSTRACT FROM AUTHOR]

With an annual loss averaging 580 M€ between 1990 and 2014, floods are the main natural catastrophe (Nat Cat) risk for the French Nat Cat compensation scheme. As part of its role in this scheme, the Caisse Centrale de Réassurance (CCR) offers state guaranteed reinsurance programs and has been modelling the risk of flooding since 2003. This model is based on the traditional valuation approach of direct tangible costs which pairs a physical model with exposure through damage curves. CCR wishes now to widen the studied damage scope to insured and noninsured economic costs and has been collaborating with the SAF research laboratory from the Institute of Financial and Insurance Sciences (ISFA) since 2014. CCR’s model has been used to estimate the insured direct damage to residential and non-residential properties and it is now being developed to include damage to vehicles, agriculture and network infrastructures. Research is also being carried out to take into account business interruptions and indirect losses using an Input-Output model. This article describes the undergoing work on model development to estimate the damage to agriculture.

The development of the acidity and the relationship between acidity, catalytic activity, and the surface structure for niobium oxide supported on zirconia is investigated for a series of solids. The catalysts were active for 2-propanol dehydration only above a threshold in Nb loading.

An investigation was conducted to know the relationship between the acidity, catalytic activity and surface structure for tungsten oxide supported in zirconia for a series of solids prepared by an equilibrium adsorption on monoclinic zirconia. Infrared spectroscopy of adsorbed probe molecules (2,6-dimethylpyridine and CO) was used to study the acidity and it was correlated with that of the formation of relatively strong bronsted acid sites.

High surface area phosphated-modified zirconia was prepared by adding phosphoric acid to zirconium hydroxide (0–3.8 P atoms nm −2 ). Up to 0.8 P atoms nm −2 , phosphate species are present mainly as monolayer of pyrophosphate ( P 2 O 7 4 − ) whereas for larger loading of phosphorus, 3D blocks of orthophosphate HP O 4 2 − are formed. The formation of these phosphate species leads to marked changes in the acid-base and catalytic properties of the oxides. When major PO x species are pyrophosphate (0–0.8 P atoms nm −2 ), basicity and Lewis acidity of zirconia decreased. In parallel, Brønsted acidic sites with weak (bidentate zirconia OH in the vicinity of P atom) and moderate (OH associated with pyrophosphate species) acidic strength are created. By contrast, orthophosphate species that mostly devellopps when larger amount of phosphate is introduced (>0.8 P atoms nm −2 ), generates stronger Brønsted acid sites (OH associated with orthophosphate phase). The correlation between the amount of these Brønsted acid sites and the rate of propene formation points out that the development of orthophosphate species on zirconia is a key factor to make this catalyst very active for propanol dehydration into propene. [ABSTRACT FROM AUTHOR]

Abstract: A series of WOx/TiO2 catalysts containing between 0.6 and 3.4Wat./nm2 was prepared by pore volume impregnation using ammonium metatungstate solution on crystallized TiO2. Characterization of the solids by X-ray diffraction, Raman and infrared spectroscopy indicated that the W phase was present essentially as a surface W species. The results also suggested an increased degree of condensation of the W phase with increasing W surface density. The most condensed W species was characterized by a ν(Wion at 1017cm−1. The IR or Raman bands attributed to specific surface species of the solids were correlated with the abundance of relatively strong Brønsted acid sites and isopropanol dehydration activity. A direct correlation was observed between propene formation rate and the area of the band at 1017cm−1, attributed to the most condensed W species. Furthermore, the abundance of this species appeared to be directly related to that of Brønsted acid sites capable of retaining 2,6-dimethyl pyridine (lutidine) following desorption at 573K. The behavior of the WOx/TiO2 system was compared with that reported for the corresponding WOx/ZrO2 solids. Higher intrinsic activity (activity per W atom) was observed for WOx/TiO2 system. [Copyright &y& Elsevier]

Using infrared spectroscopy, a comparative investigation was carried out of the surface properties of mesoporous aluminas prepared by the carbon templating route and of a commercial alumina PURAL SB. In the hydroxylated state the mesoporous materials bear surface OH groups terminally bonded to an octahedral Al3+ion, which has basic properties. In contrast, the surface of the commercial oxide additionally exposes OH groups which are terminally bonded to a tetrahedral cation. Bridging OH groups are Brønsted acid sites and are present on both oxides. The sites on the reference sample are stronger protonic acid sites than those on the mesoporous oxide. The strongest Brønsted acid sites are triply bridging OH groups, which are relatively more abundant on the reference oxide. Structural protons in the bulk of the oxides are also present on both oxides; they seem to be somewhat more stable in the reference sample. Condensation of basic OH groups with acidic groups at increasing dehydroxylation temperatures creates Lewis acid sites in the form of coordinatively unsaturated (cus) Al3+ions the acid strength of which is higher on the reference material than on the mesoporous oxide. In conclusion, the surface properties of the investigated oxides are strongly dependent on the preparation route and conditions. [ABSTRACT FROM AUTHOR]

A goal of this work was to investigate the influence of the preparation procedure and activation conditions (reduction temperature and reducing medium: pure hydrogen (100% H2) or hydrogen-argon mixture (5% H2-95% Ar)) on the activity of Co-containing BEA zeolites in Fischer–Tropsch synthesis. Therefore, a series of CoBEA zeolites were obtained by a conventional wet impregnation (Co5.0AlBEA) and a two-step postsynthesis preparation procedure involving dealumination and impregnation steps (Co5.0SiBEA). Both types of zeolites were calcined in air at 500 °C for 3 h and then reduced at 500, 800 and 900 °C for 1 h in 100 % H2 and in 5% H2–95% Ar mixture flow. The obtained Red-C-Co5.0AlBEA and Red-C-Co5.0SiBEA catalysts with various physicochemical properties were tested in Fischer–Tropsch reaction. Among the studied catalysts, Red-C-Co5.0SiBEA reduced at 500 °C in pure hydrogen was the most active, presenting selectivity to liquid products of 91% containing mainly C7–C16 n-alkanes and isoalkanes as well as small amount of olefins, with CO conversion of about 11%. The Red-C-Co5.0AlBEA catalysts were not active in the Fischer–Tropsch synthesis. It showed that removal of aluminum from the BEA zeolite in the first step of postsynthesis preparation procedure played a key role in the preparation of efficient catalysts for Fischer–Tropsch synthesis. An increase of the reduction temperature from 500 to 800 and 900 °C resulted in two times lower CO conversion and a drop of the selectivity towards liquid products (up to 62%–88%). The identified main liquid products were n-alkanes and isoalkanes. The higher activity of Red-C-Co5.0SiBEA catalysts can be assigned to good dispersion of cobalt nanoparticles and thus a smaller cobalt nanoparticles size than in the case of Red-C-Co5.0AlBEA catalyst. [ABSTRACT FROM AUTHOR]

Additional porosity, such as meso- and macropores, was introduced in zeolite extrudates with the intention intuit of improving the effective diffusivity of the catalysts. The samples were characterized in depth by nitrogen adsorption-desorption, mercury intrusion porosimetry, ammonia temperature programmed desorption and adsorption of pyridine followed by infrared spectroscopy. The results revealed no significant change in the acidity but an increase of the pore volume. According to significant improvement in the effective diffusivity, the samples were tested in the methanol-to-hydrocarbons reaction. The catalytic stability was greatly enhanced with an increase in the pore volume, demonstrating a relation between effective diffusivity and resistance to deactivation by coke formation. Further experiments also revealed a higher toluene adsorption capacity and a raise in the breakthrough time over the most porous samples due to better accessibility of toluene molecules into the active sites of the zeolite. [ABSTRACT FROM AUTHOR]

Highlights: [•] Pd mesoporous silica and aluminosilica were prepared for DeNO x by CH4 in the presence of O2. [•] Incipient wetness impregnation led to small PdO nanoparticles inside the mesopores of SBA-15. [•] PdO particles were located on the external surface of support in the case of palladium nitrate precursor. [•] Pd–SBA–Imp is the best catalyst for deNO x in comparison with Pd–Al–SBA–IMP. [ABSTRACT FROM AUTHOR]

Abstract: Two different procedures were used to prepare dealuminated BEA zeolite. The first procedure realized in two steps consisted of first calcination of original tetraethylammonium (TEA) BEA(17) zeolite in air at 823K for 15h to remove organic template and then treatment of as resulted organic-free HAlBEA(17) zeolite with concentrated nitric acid solution for different times to remove part or all Al atoms. Two periods was distinguished in the removal of Al atoms from HAlBEA(17) framework during the first procedure. During initial period (up to 0.08h), the dealumination was very fast and 94% of Al was removed. This period corresponded to the easy removal of extra framework octahedral and framework tetrahedral aluminum from T3-T9 sites. In the second period (from 0.08 to 4h), the dealumination was much slower. It corresponded to a much more difficult removal of framework tetrahedral aluminum from T1 and T2 sites. The second procedure realized in one step consisted of direct treatment of original TEABEA zeolite with concentrated nitric acid solution to remove simultaneously organic template and Al atoms. To obtain partly or totally dealuminated BEA zeolite the treatment time was 0.08 and 4h respectively. The influence of the nitric acid treatment on Al removal, framework composition and acidity of BEA zeolite were investigated by XRD, FTIR and NMR. 2D 27Al 3Q MAS NMR allowed distinguishing two kinds of framework tetrahedral Al atoms (AlTd(2a) and AlTd(2b)) in BEA zeolite which relative amounts depended on the Si/Al ratio. The Brønsted and Lewis acidic centers were evidenced in dealuminated BEA zeolites by FTIR spectra of adsorbed pyridine and CO use as probe molecules. Their relative amounts depended on the degree of dealumination and procedure used for removal Al atoms. [Copyright &y& Elsevier]

Abstract: Two series of V x SiBEA(I) and V x SiBEA(II) zeolites have been prepared by a two-steps postsynthesis method which consists, in the first step, in the dealumination of TEABEA zeolite by two different procedures to obtain SiBEA(I) and SiBEA(II) zeolites and then, in the second step, in contacting the obtained zeolites with an aqueous NH4VO3 solution at pH 2.7. Because the NH4VO3 solution at pH 2.7 predominantly contains mononuclear VO2 + ions, vanadium can be incorporated into SiBEA(I) and SiBEA(II) as framework pseudo-tetrahedral non hydroxylated (SiO)3V(V)roxylated (SiO)2(OH)V(V) by reaction with silanol groups of vacant T-atom sites. Combined use of FTIR, DR UV–vis, 51V NMR, EPR and TPR allows to determine the oxidation state, nature and environment of vanadium in as prepared, calcined, rehydrated, activated and reduced V x SiBEA(I) and V x SiBEA(II) samples. It is shown that the procedure of dealumination has the effect on the properties of the silanol groups of vacant T-atom sites in SiBEA(I) and SiBEA(II) and on the nature and environment of V species in as prepared V x SiBEA(I) and V x SiBEA(II). As evidenced by DR UV–vis and 51V MAS NMR in V x SiBEA(II), vanadium is present only as pseudo-tetrahedral V(V) species, and in contrast in V x SiBEA(I) as pseudo-tetrahedral and octahedral V(V) species. The oxidation state of framework tetrahedral vanadium in V x SiBEA(I) and V x SiBEA(II) easily change upon calcination in oxygen, outgassing at 773K and reducing with hydrogen at high temperature (873K), as shown by EPR. The presence of Brønsted and Lewis acidic centres are evidenced in V x SiBEA(II) by FTIR adsorption investigations of pyridine and CO used as probe molecules. [Copyright &y& Elsevier]

The relationship between the acidity, catalytic activity, and surface structure for tungsten oxide supported on zirconia was investigated for a series of solids prepared by equilibrium adsorption on monoclinic zirconia. The catalysts were active for propanol dehydration only above a threshold in W loading. The acidity was studied by infrared spectroscopy of adsorbed probe molecules (2,6-dimethylpyridine and CO), and the onset of activity was correlated with that of the formation of relatively strong Brønsted acid sites. The variation in the abundance of these sites correlated with the catalytic activity. Lewis sites were present but could not be directly associated with the activity. Raman, IR, and UV spectroscopy results indicated that the active sites were related to polymeric W surface species.