Search results for "SEPARATION"
showing 10 items of 865 documents
Gas Selective Ultrathin Organic Covalent Networks Synthesized by iPECVD: Does the Central Metal Ion Matter?
2017
The potential of porphyrin-derived metal organic covalent networks (OCN) thin films on light gas separations has been recently demonstrated. However, whether or not the central metal ion of the porphyrin plays a key role on separation performance has yet to be elucidated. Here, one metal-free and three metal-containing (zinc(II), manganese(III), and cobalt(II)) porphyrin-derived OCN thin films are successfully deposited on various substrates via an easily scalable initiated plasma-enhanced chemical vapor deposition approach. Among these four porphyrin-derived OCN thin films exhibiting superior light gas separation performances, three of them are synthesized for the first time. The gas perme…
The first operating thermolytic reverse electrodialysis heat engine
2020
Abstract Thermolytic reverse electrodialysis heat engine (t-RED HE) has been recently proposed as a technology for converting low-temperature waste heat into electricity. The construction and operation of the first world lab-scale prototype unit are reported. The system consists of: (i) a reverse electrodialysis unit where, the concentration gradient between two solutions of thermolytic salts is converted into electricity and (ii) a thermally-driven regeneration unit where low-temperature heat is used to restore the initial conditions of the two feed streams. Regeneration is based on a degradation process of salts into gaseous ammonia and carbon dioxide, which can be removed almost entirely…
PBI mixed matrix hollow fiber membrane: Influence of ZIF-8 filler over H2/CO2 separation performance at high temperature and pressure
2020
High performance and commercially attractive mixed-matrix membranes were developed for H2/CO2 separation via a scalable hollow fiber spinning process. Thin (~300 nm) and defect-free selective layers were successfully created with a uniform distribution of the nanosized (~60 nm) zeolitic-imidazole framework (ZIF-8) filler within the polymer (polybenzimidazole, PBI) matrix. These membranes were able to operate at high temperature (150 °C) and pressure (up to 30 bar) process conditions required in treatment of pre-combustion and syngas process gas streams. Compared with neat PBI hollow fibers, filler incorporation into the polymer matrix leads to a strong increase in H2 permeance from 65 GPU t…
Performance of a polypropylene membrane contactor for the recovery of dissolved methane from anaerobic effluents: Mass transfer evaluation, long-term…
2018
Abstract A polypropylene membrane contactor was used for the recovery of dissolved methane from an anaerobic reactor effluent. Effect of operational parameters, operation mode and fouling on long-term operation was studied using vacuum pressure or N 2 as sweep gas. Results were analyzed based on the mass transfer estimations. Lower performance was observed in the shell-side mode due to the lower liquid velocity and the probable channeling. Membrane pore wetting was observed with the increase in Q L in the vacuum-pressure mode. This was confirmed with mass transfer resistance analysis, resulting in an estimated wetted pore fraction of between 0.25 and 0.53. The highest removal efficiencies w…
Enhanced power-conversion efficiency in organic solar cells incorporating copolymeric phase-separation modulators
2018
A new class of copolymers containing oligothiophene moieties with different lengths and fullerene units have been designed and prepared by an easy and inexpensive one-step synthetic approach. The incorporation of small quantities of these copolymers into bulk heterojunction (BHJ) solar cells with donor regioregular polythiophene (P3HT) and an acceptor fullerene derivate (PCBM) results in good control of the phase separation process without further affecting the BHJ optoelectronic properties. Indeed, under thermal annealing these copolymers allow the modulation of the growth of domains whose size depends on the length of the copolymer repetitive units. Domain size on the same length scale as…
Control of flow separation using electromagnetic forces
2003
Introduction If a fluid is electrically conductive, its flow may be controlled using electromagnetic forces. Meanwhile, this technique is a recognized tool even on an industrial scale for handling highly conductive materials like liquid metals. However, also fluids of low electrical conductivity as considered in the present study, like sea--water and other electrolytes, permit electromagnetic flow control. Experimental results on the prevention of flow separation by means of a streamwise, wall parallel Lorentz force acting on the suction side of inclined flat plates and hydrofoils will be presented. Force Configuration The stripwise arrangement of permanent magnets and electrodes of alterna…
Efficient Gas Separation and Transport Mechanism in Rare Hemilabile Metal–Organic Framework
2019
Understanding/visualizing the established interactions between gases and adsorbents is mandatory to implement better performance materials in adsorption/separation processes. Here we report the unique behavior of a rare example of a hemilabile chiral three-dimensional metal–organic framework (MOF) with an unprecedented qtz-e-type topology, with formula CuII2(S,S)-hismox·5H2O (1) (hismox = bis[(S)-histidine]oxalyl diamide). 1 exhibits a continuous and reversible breathing behavior, based on the hemilability of carboxylate groups from l-histidine. In situ powder (PXRD) and single crystal X-ray diffraction (SCXRD) using synchrotron radiation allowed us to unveil the crystal structures of four …
Gas Transport in Mixed Matrix Membranes: Two Methods for Time Lag Determination
2020
The most widely used method to measure the transport properties of dense polymeric membranes is the time lag method in a constant volume/pressure increase instrument. Although simple and quick, this method provides only relatively superficial, averaged data of the permeability, diffusivity, and solubility of gas or vapor species in the membrane. The present manuscript discusses a more sophisticated computational method to determine the transport properties on the basis of a fit of the entire permeation curve, including the transient period. The traditional tangent method and the fitting procedure were compared for the transport of six light gases (H2, He, O2, N2, CH4, and CO2) and ethane an…
Molecular structure and multi-body potential of mean force in silica-polystyrene nanocomposites
2018
We perform a systematic application of the hybrid particle-field molecular dynamics technique [Milano et al, J. Chem. Phys. 2009, 130, 214106] to study interfacial properties and potential of mean force (PMF) for separating nanoparticles (NPs) in a melt. Specifically, we consider Silica NPs bare or grafted with Polystyrene chains, aiming to shed light on the interactions among free and grafted chains affecting the dispersion of NPs in the nanocomposite. The proposed hybrid models show good performances in catching the local structure of the chains, and in particular their density profiles, documenting the existence of the "wet-brush-to-dry-brush" transition. By using these models, the PMF b…
Glovebox atmosphere detritiation process using gas separation membranes.
2003
Abstract The use of gas separation membranes in atmospheric detritiation systems has been studied. The main advantage of this new process is to reduce the number and/or the size of the equipment in comparison to conventional tritium removal systems. Owing to the constraints linked to tritium handling, the separation performances of several commercial hollow fiber organic membranes have been analyzed, under various operating conditions, with hydrogen/nitrogen or deuterium/nitrogen mixtures. The experiments are performed with small quantities of hydrogen or deuterium (5000 ppm). The experimental results allow to evaluate the separation efficiency of these membranes and to determine the approp…