Corning (France)

Abstract Aluminosilicate glasses are widely used in everyday applications and can be seen as building blocks of modern technology, from display screens to glass‐ceramics. However, due to their high viscosities, gas bubbles can only be removed from aluminosilicate melts at high temperatures, leading to significant energy costs. This fining process can be improved with the use of multivalent oxides such as SnO 2 . In this study, extended x‐ray absorption fine structure (EXAFS) and Raman spectroscopy were used to determine the local environment surrounding Sn(II) and Sn(IV) ions in a sodium aluminosilicate glass. In situ XANES spectroscopy enabled the quantification of Sn redox state at high temperature, allowing for the determination of thermodynamic parameters governing the Sn reduction. Our results show that Sn(IV) is octahedrally coordinated and linked to network‐forming tetrahedra through corner‐sharing, whereas Sn(II) is in a lower coordination number. Comparing the modeled behavior of Sn with that of Fe and Ce, it appears that SnO 2 is a suitable fining agent for aluminosilicate glasses as it undergoes reduction when the viscosity is sufficiently low for bubbles to escape the melt. Conversely, the use of CeO 2 leads to substantial gas release at higher viscosities, resulting in foam formation within the glass.

Herein we report the efficient synthesis of β-aminoketones via addition of a vinyl Grignard reagent into amides followed by trapping of the vinyl ketone intermediate with the magnesium-amide by-product. The reaction was successfully translated from a batch process into continuous flow mode to increase its efficiency, safety and scalability. Different set-ups were evaluated to minimize/overcome clogging issues arising from magnesium salt precipitates. Ultimately, the resulting β-aminoketones were obtained in high yields and productivities with residence times of less than 90 seconds at elevated temperatures of 50 °C. Importantly, the β-aminoketone products are valuable building blocks that can be unmasked to reactive vinyl ketones via a Cope elimination process.

A continuous flow approach for the aerobic photo-oxidation of benzylic substrates to ketone and aldehyde products is presented. The resulting process exploits UV-A LEDs (375 nm) in combination with a Corning AFR reactor that ensures effective gas-liquid mixing and leads to short residence times of 1 min. A variety of benzylic substrates are converted to their corresponding carbonyl products, and scalability is demonstrated to produce multigram quantities of products within a few hours. Overall, this continuous flow approach offers several improvements over alternative oxidation methods due to the combined use of air as an oxidant and SAS (sodium anthraquinone-2 sulfonate) as a water-soluble photocatalyst. The use of greener and safer conditions together with process intensification principles renders this flow approach attractive for further industrial applications.

Au sein de l’industrie verrière, connaître la composition et l’état structural des verres est un enjeu important pour le contrôle qualité sur les sites de production ou encore la recherche et le développement de nouveaux produits. Dans ce chapitre, nous décrirons brièvement différentes méthodes pouvant être utilisées par l’industrie verrière pour obtenir des informations structurales, chimiques, ou encore sur la composition des infondus ou le degré d’oxydation des éléments multivalents influençant les propriétés optiques des produits finis.

Les articles en verre ont intégré depuis quelques siècles un ensemble très vaste d’objets qui composent aujourd’hui notre quotidien. Leur comportement au contact de solutions aqueuses ou d’atmosphères humides a été étudié par le biais de nombreuses recherches pour des domaines d’application très variés, allant des verres de conditionnement dans le domaine nucléaire aux verres utilisés dans les arts de la table, la cosmétique, les produits pharmaceutiques, l’optique, le médical ou encore le patrimoine. Cet état de l’art décrit les principales étapes et mécanismes d’altération ainsi que leurs conséquences sur l’évolution des propriétés du matériau au cours de son vieillissement. L’influence des principaux paramètres intrinsèques (composition chimique et structure vitreuse) et environnementaux (composition du milieu, pH, température, humidité relative) sur la cinétique d’altération est présentée. Enfin, les tests normalisés permettant de quantifier l’altération sont répertoriés ainsi que les techniques de caractérisation adéquates à l’analyse des couches d’altération.

Highly efficient and chemoselective singlet oxygen oxidation of unprotected methionine was performed in water using a continuous mesofluidic reactor. Sustainable process engineering and conditions were combined to maximize process efficiency and atom economy, with virtually no waste generation and safe operating conditions. Three water-soluble metal-free photosensitizers [Rose Bengal, Methylene Blue, and tetrakis(4-carboxyphenyl)porphyrin] were assessed. The best results were obtained with Rose Bengal (0.1 mol %) at room temperature under white light irradiation and a slight excess of oxygen. Process and reaction parameters were monitored in real-time with in-line NMR. Other classical organic substrates (α-terpinene and citronellol) were oxidized under similar conditions with excellent performances.

Development of a scalable continuous-flow process towards enrichedthreo-methylphenidate (Ritalin) hydrochloride.

The influence of zirconium as a nucleating agent on the congruent crystallization and relevant physical properties of a supercooled calcium aluminosilicate melt of a composition close to CaAl2SiO6 has been investigated up to 6 mol% ZrO2. Zirconium marginally affects rheological and structural properties, decreasing the viscosity of the Zr‐free melt by no more than 0.25 log unit and, as observed by Raman spectroscopy, not changing significantly the polymerization state of the material. Whereas the Zr‐free melt crystallizes congruently and heterogeneously from the sample surface to yield yoshiokaite, a stuffed derivative of the nepheline structure, addition of zirconia promotes instead bulk crystallization of tetragonal ZrO2 and then of yoshiokaite. The latter process takes place in two stages: dissolved Zr first promotes homogeneous precipitation of zirconia before yoshiokaite crystallizes congruently from a Zr‐depleted volume of melt around zirconia precipitates. This process makes zirconium, and probably other poorly soluble oxides, valuable to control congruent crystallization in silicate glass‐ceramics. From the recorded thermograms, an enthalpy of crystallization of 40 and 46 kJ/mol has been determined at 1060 and 1140 K, respectively, for CaAl2SiO6 yoshiokaite, a very low value that is likely due to the extensive atomic disorder of crystals precipitating at high degrees of supercooling.

Diazomethane is a valuable derivatizing agent but very difficult to handle for large-scale chemical transformations. We report here the base-induced decomposition of N-methyl-N-nitrosourea under continuous-flow conditions that enables the production up to 19 mol d–1 of diazomethane, at a total flow rate of 53 mL min–1.

The authors report an ambient-pressure differential scanning calorimetric study of a calcium metaphosphate glass that has been isostatically compressed slightly above its glass transition temperature and was frozen-in under pressure. It is shown that the enthalpy overshoot of the calorimetric glass transition is enhanced by this treatment. This enhancement is associated with a decrease in the apparent fictive temperature TfA that is determined using the enthalpy-matching approach. The origin of this correlation is discussed.