Stability investigation of polyPOSS-imide membranes for H2 purification and their application in the steel industry

In the present work, the high-temperature and long-term hydrothermal stability of novel polyPOSS-imide membranes for high-temperature hydrogen separation is investigated. The polyPOSS-imide membranes are found to exhibit an appropriate stability up to 300 C. Above this temperature the membrane selectivity rapidly decreases, which is seemingly related to changes in the molecular structure coupled to silanol condensation forming siloxane groups. Surprisingly, the exposure of the membrane to temperatures of up to 300 C even increases the H2 permeance together with the selective feature of the polyPOSS-imide layer. Subsequently, the long-term hydrothermal stability of the polyPOSS-imide membranes was investigated over a period of close to 1000 h at 250 C exposing the membrane to 10 mol% steam in the feed. An increase in H2/CH4 selectivity was observed upon water addition, and even though a minor drop was noticed over time during the hydrothermal operation, the selectivity exceeds the initial selectivity obtained in the dry feed atmosphere. After the removal of steam from the feed, the performance returns to its original state prior to the exposure to any steam showing appropriate steam stability of the polyPOSS-imide membranes. A conceptual process design and assessment was performed for application of these membranes involving a combination of carbon reuse and electrification of the steel making process with co-production of hydrogen. The results indicate a CO2 avoidance of 14%. The CO2 reduction achieved using renewable electricity in the proposed scheme is a factor 2.76 higher compared to a situation where the same renewable electricity would be fed in the electricity grid.publishedVersio

Comparing amine- and ammonium functionalized silsesquioxanes for large scale synthesis of hybrid polyimide high-temperature gas separation membranes

PolyPOSS-imide membranes are promising for separating H2 from larger molecules (CO2, N2, CH4) at temperatures up to 300 °C. Their fabrication involves two steps: interfacial polymerization of POSS and 6FDA, followed by thermal imidization. This work provides a systematic study of the effects of cations on membrane properties and performance. For this, two distinct POSS molecules were used: functionalized with -NH3+Cl− or, so far unexplored, -NH2. The ammonium groups are partially deprotonated by using three different bases, LiOH, NaOH, and KOH. We demonstrate that the introduced cations affect the film thickness but not the molecular composition of the polyamic acid. All polyamic acids can be imidized, but the cations reduce the imidization kinetics as well as the loss of organic crosslinkers. For flat disc membranes, at 200 °C, the absence of cations results in comparable permeability combined with higher selectivity for H2/N2. This, and the possibility to discard adding a base, motivated a scale-up study of the new POSS. For tubular membranes, much higher ideal and mixed gas selectivities are found than for membranes where NaOH was added. Results indicate that the new route allows more reproducible production of defect free membranes and has potential for larger-scale polyPOSSimide fabrication.publishedVersio

A family of dual-activity glycosyltransferasesphosphorylases mediates mannogen turnover and virulence in Leishmania parasites

Parasitic protists belonging to the genus Leishmania synthesize the non-canonical carbohydrate reserve, mannogen, which is composed of β-1,2-mannan oligosaccharides. Here, we identify a class of dual-activity mannosyltransferase/phosphorylases (MTPs) that catalyze both the sugar nucleotide-dependent biosynthesis and phosphorolytic turnover of mannogen. Structural and phylogenic analysis shows that while the MTPs are structurally related to bacterial mannan phosphorylases, they constitute a distinct family of glycosyltransferases (GT108) that have likely been acquired by horizontal gene transfer from gram-positive bacteria. The seven MTPs catalyze the constitutive synthesis and turnover of mannogen. This metabolic rheostat protects obligate intracellular parasite stages from nutrient excess, and is essential for thermotolerance and parasite infectivity in the mammalian host. Our results suggest that the acquisition and expansion of the MTP family in Leishmania increased the metabolic flexibility of these protists and contributed to their capacity to colonize new host niches

La maladie de Whipple (revue de la littérature à propos d'un cas)

LIMOGES-BU Médecine pharmacie (870852108) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Diode-pumped solid-state picosecond UV coherent source for time-resolved analysis of photobiological processes

International audienc

Dispositif compact pour le façonnage temporel des états de polarisation aux échelles de temps femtosecondes

National audienc

Femtosecond pulse coherent shaping based on liquid crystal 2D spatial light modulator

International audienc

Imagerie polarimétrique endoscopique

National audienc