Search results for "SELECTIVITY"
showing 10 items of 1148 documents
Cation influence in adsorptive propane/propylene separation in ZIF-8 (SOD) topology
2019
Separation of propylene/propane is one of the most challenging and energy consuming processes in the chemical industry. Propylene demand is increasing and a 99.5% purity is required for industrial purposes. Adsorption based solutions are the most promising alternatives to improve the economical/energetic efficiency of the process. Zeolitic Imidazolate Frameworks (ZIFs) combine the desired characteristics from both MOFs and zeolites: tunability and flexibility from metal organic frameworks, and exceptional thermal and chemical stability from zeolites. In order to enlighten the role of the cation in the sodalite ZIF-8 framework for propane/propylene separation, dynamic breakthrough measuremen…
Inverse-voltammetric determination of bismuth in biomaterials with computer assisted peak evaluation
1988
The inverse-voltammetric determination of low bismuth concentrations in a 1 mol/l HCl as supporting electrolyte was investigated with regard to optimal working conditions. New and old types of mercury-drop electrodes and mercury-film electrodes were compared concerning their sensibility, selectivity and interferences. With both electrodes the determination of 0.1 μg/l to 0.01 μg/l bismuth is possible. The influence of a large excess of copper and antimony on the inverse-voltammetric determination of bismuth was studied in detail.
Xenon Recovery by DD3R Zeolite Membranes: Application in Anaesthetics.
2019
Xe is only produced by cryogenic distillation of air, and its availability is limited by the extremely low abundance. Therefore, Xe recovery after usage is the only way to guarantee sufficient supply and broad application. Herein we demonstrate DD3R zeolite as a benchmark membrane material for CO2 /Xe separation. The CO2 permeance after an optimized membrane synthesis is one order magnitude higher than for conventional membranes and is less susceptible to water vapour. The overall membrane performance is dominated by diffusivity selectivity of CO2 over Xe in DD3R zeolite membranes, whereby rigidity of the zeolite structure plays a key role. For relevant anaesthetic composition ( 320 h). Thi…
Control of catalytic properties of ZSM-5 made by fast and template- free synthesis.
1989
Abstract The fast template-free synthesis of ZSM-5 was accomplished in both static and stirred autoclaves employing sodiumwaterglass.silica hydrogel and pyrogenic silicas as silica sources. Highly pure crystalline ZSM-5 was obtained in the sodiumwaterglass reaction system in the stirred autoclaves without seeds within 3 hours. Addition of 2% (w/w) of seeds reduced the reaction time to 2 hours. The catalytic activity and shape selectivity of the H-ZSM-5, tested by the disproportionation of ethylbenzene, was found to be largely controlled by the synthesis parameters and by the posttreatments. The homogeneous aluminum distribution across the crystals achieved by this synthetis route resulted i…
Tuning Selectivities in Gas Separation Membranes Based on Polymer-Grafted Nanoparticles
2020
Polymer membranes are critical to many sustainability applications that require the size-based separation of gas mixtures. Despite their ubiquity, there is a continuing need to selectively affect the transport of different mixture components while enhancing mechanical strength and hindering aging. Polymer-grafted nanoparticles (GNPs) have recently been explored in the context of gas separations. Membranes made from pure GNPs have higher gas permeability and lower selectivity relative to the neat polymer because they have increased mean free volume. Going beyond this ability to manipulate the mean free volume by grafting chains to a nanoparticle, the conceptual advance of the present work is…
Enhancement of D 2 /H 2 Selectivity in Zeolite A through Partial Na–K Exchange: Single-Gas and Coadsorption Studies at 45–77 K
2020
International audience; We report D2/H2 adsorption selectivities under cryogenic temperatures (45-77 K) in Na and K-Na exchanged zeolites A (LTA structural code) measured by co-adsorption technique. These values are systematically compared with Ideal Adsorbed Solution Theory (IAST) predictions based on the single gas adsorption isotherms. For NaA zeolite the evolution of the selectivity as a function of total pressure and gas mixture composition at 77 K shows ideal behavior. In contrast, as temperature decreases, D2/H2 selectivity rises exponentially and its values can no longer be predicted by IAST. We found that in these conditions the evolution of the selectivity can be described by a si…
CO2 reduction by C3N4-TiO2 Nafion photocatalytic membrane reactor as a promising environmental pathway to solar fuels
2019
Abstract We investigated CO2 photocatalytic reduction coupling, for the first time in literature, the assets offered by the continuous operating mode using C3N4-TiO2 photo-catalyst embedded in a dense Nafion matrix. The reactor performance was analyzed under UV–vis light in terms of productivity, selectivity and converted carbon. Reaction pressure was specifically investigated for its effect as a “driver” in determining reactor performance, modulating products removal from the reaction volume. In addition, the membrane reactor performance was explored as a function of H2O/CO2 feed molar ratio and contact time. The higher feed pressure (5 bar) led to a lesser MeOH production and a greater am…
Solvent driven formation of silver embedded resorcinarene nanorods
2012
Silver complexes of resorcinarene bis-crown-5 were observed to arrange into nanorods of 2.4 nm in diameter. The left- and right-handed isomers of the inherently chiral resorcinarene host are separated into their own entity in the self-assembly process with the periphery of the nanorods consisting of silver cations included in the cavity.
Catalytic and photocatalytic epoxidation of limonene: Using mesoporous silica nanoparticles as functional support for a Janus-like approach
2020
Abstract Mesoporous silica nanoparticles (MSN) were used as a platform to design novel active materials for the catalytic and photocatalytic epoxidation of limonene. Binary systems comprised of TiO2 and MSN were used for the catalytic reaction when doped with manganese, and for the photocatalytic reaction when functionalised with hexadecyl chains or imidazolinyl groups. All of the MSN based systems were synthesized by condensation in emulsion. A thorough characterization of the powders has been performed by means of Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES), X-ray diffraction (XRD), FT-IR, Raman and EPR Spectroscopy, Fluorescence and diffuse reflectance UV–vis (DR…
Superior Fischer-Tropsch performance of uniform cobalt nanoparticles deposited into mesoporous SiC
2020
Electrochemically-derived well-crystalline mesoporous silicon carbide (pSiC) was used as a host for cobalt nanoparticles to demonstrate superior catalytic performance during the CO hydrogenation according to Fischer-Tropsch. Colloidal Co nanoparticles (9 ± 0.4 nm) were prepared independently using colloidal recipes before incorporating them into pSiC and, for comparison purposes, into commercially available silica (Davisil) as well as foam-like MCF-17 supports. The Co/pSiC catalyst demonstrated the highest (per unit mass) catalytic activity of 117 µmol.g(CO)-1.g-1(Co).s-1 at 220 °C which was larger by about one order of magnitude as compared to both silica supported cobalt catalysts. Furthe…