Using silver exchange to achieve high uptake and selectivity for propylene/ propane separation in zeolite Y

Adsorptive separation of propylene and propane, an important step of polypropylene production, is more energy-efficient than distillation. However, the challenge lies in the design of an adsorbent which exhibits both high selectivity and uptake. Herein, we hypothesise that enhancing the propylene affinity of the adsorption sites while keeping a suitable pore size can address this challenge. To do so, we performed silver exchange of a commercial zeolite Y, thereby making the adsorbent design easily scalable. We characterised the adsorbent using analytical, spectroscopic and imaging tools, tested its equilibrium and dynamic sorption properties using volumetric and gravimetric techniques and compared its performance to those of state-of-the-art adsorbents as well as other silver-functionalised adsorbents. The silver-exchanged zeolite Y (Ag-Y) exhibited one of the best selectivity vs uptake performances reported so far. Ag-Y also displayed fast adsorption kinetics and reversible propylene sorption, making it a promising new benchmark for propylene/propane separation. Synchrotron-based pair distribution function analyses identified the silver cations’ location which confirmed that the silver sites are easily accessible to the adsorbates. This aspect can, in part, explain the propylene/propane separation performance observed. The overall design strategy proposed here to enhance sorption site affinity and maintain pore size could be extended to other adsorbents and support the deployment of adsorption technology for propylene/propane separation

Effect of surface functionalization on the moisture stability and sorption properties of porous boron nitride

Porous boron nitride (BN) is a promising adsorbent owing to its high surface area and porosity, as well as thermal and oxidative stability. It has been explored in the past decade for applications in gas and liquid separations, such as CO2 capture and water cleaning. However, the material has displayed hydrolytic instability. Owing to the presence of moisture in most industrial settings, whether it is for storage or cyclic adsorption processes, ensuring the moisture stability of an adsorbent is crucial. While this topic has been researched for other adsorbents such as zeolites and metal organic frameworks (MOFs), little is known on controlling the hydrolytic stability of porous BN. In this study, we propose a method to enhance porous BN's hydrolytic stability via surface functionalization using a fluoroalkylsilane. We explored two different routes of functionalization: (i) functionalization of porous BN powder followed by pelletization (route 1) and (ii) coating of porous BN pellets with fluoroalkylsilane (route 2). Spectroscopic, analytical and imaging techniques confirmed the functionalization process qualitatively and quantitatively. We subjected the functionalized samples to moisture exposure at 54% RH (similar to common storage conditions) and 92% RH (similar to flue gas stream conditions with high moisture content), and characterized them to probe their resistance to moisture. We also investigated their equilibrium and kinetic sorption properties in the context of CO2/N2 separation. Both routes produced materials with enhanced moisture stability. However, we noted differences between both functionalization routes. Route 2 produced a sample with a higher grafting yield and hydrophobic nature, and therefore better resistance to moisture exposure than route 1. From a sorption point of view, despite reduced porosity, the functionalized samples maintain reasonable CO2 uptakes. The functionalization led to changes in the textural features of the samples, which caused differences in the mass transfer. This work shows that functionalization could be used to protect porous BN upon moisture exposure

Stroke Thrombus Segmentation on SWAN with Multi-Directional U-Nets

International audienceThe thrombus causing a stroke can be seen on the susceptibility weighted angiography (SWAN) magnetic resonance imaging (MRI) sequence. But it is very small and hard to detect by humans. Up to date the thrombus is identified by trained human experts. But as stroke needs quick treatment, an automatic detection of the thrombus would be useful to speed up the diagnosis of acute stroke. We propose a method for automatic thrombus detection from SWAN using three separate U-Nets which work on the axial, coronal and sagittal planes

Vibrational dynamics in molecular condensed phases with the CLIO free electron laser

International audienc

Hemispherectomy - a Further Modification Using Omentum Vascularized Free Flaps

This report describes the authors' technique designed to further prevent the late complications of hemispherectomy. A vascularized omental free flap is used to fill the extradural dead space left following the procedure advocated by Adams. This procedure may provide further stability to the residual brain and reduce infective complications

Devenir des elevages allaitants specialises de Midi-Pyrenees a l'horizon 2000 Premiers effets de la reforme de la PAC sur le revenu a l'echeance 1995, elements prospectifs 1995-2000

SIGLEAvailable from INIST (FR), Document Supply Serviceunder shelf-number : RP 14456 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc