The contribution of surface roughness of nonporous polymeric membranes to their gas separation and mechanical properties was studied in terms of surface free energy. The membranes samples were ...prepared based on glassy polymers with different chain rigidity, namely polysulfone (PSU), cellulose triacetate (CTA), and poly(vinyl alcohol) (PVA). The results were obtained by atomic force and scanning electron microscopy (AFM and SEM) with individual gas permeation, wettability, and mechanical testing. The specific surface free energy (as well as its polar and dispersive components) for the polymers was calculated by the Owens–Wendt method. It was proven that the surface roughness of the polymer membranes affects both energy components; however, the degree of this influence depends on the chemical nature of the corresponding polymer. Moreover, it was assumed that the dispersive energy component is inversely correlated with any gases’ total permeability. In contrast, the polar one is inversely correlated with the permeability by gases with the ability for site-specific interactions. The gas separation results confirmed this assumption. It was also shown that the mechanical properties of the polymer membranes are also influenced by the surface energy, namely, its dispersive component.
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IJS, KILJ, NUK, PNG, UL, UM
A mesoporous silica support was synthesized using the sol-gel method from trichlorosilane. There is a tendency for the specific surface area and the proportion of silica particles mesopores to ...increase during all stages of sol-gel synthesis. It has been shown that the insertion of hexane and toluene, as additional solvents, into the structure-forming polyethylene glycol, makes it possible to regulate the pore size and specific surface area of silica. Silica functionalization was carried out using SILP technology. The activities of the catalytic systems based on polymer and inorganic supports immobilized by imidazole-based ionic liquids during the trichlorosilane disproportionation reaction were compared. There is a tendency for the monosilane yield for catalytic systems based on an inorganic support to increase. We identified the most promising catalyst in terms of monosilane yield and proposed a bifunctional catalyst that exhibited activity in two parallel reactions: trichlorosilane disproportionation and silicon tetrachloride hydrogenation.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The present study continues the development and enhancement of a highly efficient unique hybrid technique-membrane-assisted gas absorption in designing the separation unit, which provides the ...improvement in mass-transfer of a target component during the ammonia capture process from a process loop of the Haber-Bosch technological route. In order to minimize the absorbent volume to membrane area ratio, the special separation cell was designed based on a combination of two types of hollow fiber membranes, dense gas separation membrane and porous pervaporation membrane. The separation performance tests were implemented under two sets of conditions, sweeping the bore (permeate) side of a cell with helium and hydrogen-nitrogen mix. For both cases, the membrane-assisted gas absorption cell demonstrated high separation efficiency, and the ammonia concentration in the permeate was never lower than 81 mol%; meanwhile, under the hydrogen-nitrogen bore sweep conditions, the ammonia concentration in the permeate reached 97.5 mol% in a single-step process. Nevertheless, there is a product purity-recovery rate trade-off, which is a typical issue for separation processes.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
This work explored the zinc nanoparticles obtained by the one-stage induction flow levitation method. A 10 kW tube generator with an operating frequency of 440 kHz was used. The process used 8 mm ...diameter zinc granules (2 g weight) with a purity of 99.9%. Zinc wire was fed to replace the evaporated metal from the granule surface. This method productivity was 30 g/h of nanoparticles. In addition, various methods were used to characterize the resulting nanoparticles: scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-Ray fluorescence analysis (XRF), dynamic light scattering (DLS), porosimetry and inductively coupled plasma atomic emission spectroscopy (ICP-MS). The resulting nanoparticle size, determined by SEM and porosimetry, was 350 nm, while the size of the primary crystallites was 21 nm. The amount of impurities in the resulting nanoparticles did not exceed 1000 ppm.
The present study provides a solvent-free organic synthesis of quaternary ammonium salts: bis(2-hydroxyethyl)dimethylammonium taurate (BHEDMATau) and bis(2-hydroxyethyl)dimethylammonium acetate ...(BHEDMAOAc). These ionic compounds are promising materials for carbon dioxide capture processes, as mono sorbents, supplemental components in the conventional process of chemical absorption, and in the combined membrane approach for improving sorption efficiency. The synthesized compounds were characterized by 1H NMR and FT-IR spectroscopies and elemental analysis. Afterward, the sorption properties of the compounds were evaluated using the inverse gas chromatography (IGC) method, and their thermodynamic parameters were calculated in the temperature range of 303.15–333.15 K. The enthalpy change (∆sH) was less than 80 kJ·mol−1, indicated by the physical nature of sorption and also proved by FT-IR. Henry’s law constant in regard to carbon dioxide at 303.15 K was equal to 4.76 MPa for BHEDMATau, being almost 2.5 lower than for BHEDMAOAc (11.55 MPa). The calculated carbon dioxide sorption capacity for BHEDMATau and BHEDMAOAc amounted to 0.58 and 0.30 mmol·g−1, respectively. The obtained parameters are comparable with the known solid sorbents and ionic liquids used for CO2 capture. However, the synthesized compounds, combining the advantages of both alkanolamines and ionic liquids, contain no fluorine in their structure and thus match the principles of environmental care.
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•Membrane-assisted gas absorption technique was proposed for NH3 capture.•Ammonium thiocyanate-based deep eutectic solvents were tested as absorbents for NH3.•Experimental evaluation ...of membrane-assisted gas separation technique was performed.•High-efficient NH3 recovery was achieved separating ternary H2/N2/NH3 gas mixture.
The present study deals with the first complex experimental evaluation of the unique hybrid technique – membrane-assisted gas absorption for NH3 recovery applications. In order to determine the influence of technological parameters and compare different absorbents impact, a special lab-scale test platform was designed and coupled with the specific back-flush-to-vent gas chromatographic technique. The efficiency of ammonia capture was evaluated during the separation of ternary gas mixture consisting of H2, N2 and NH3. The wide range of absorbents and gas separation membranes was screened to determine the potentially efficient combinations of membrane-absorbent systems. As a result, the poly-(vinyltrimethylsilane) (PVTMS) commercially available gas separation membrane covered with deep eutectic solvents (DES) based on ammonium thiocyanate (NH4SCN) combined with glycerol (G), urea (U) and ethylene glycol (EG) was used as a combined system for further evaluation in the NH3 recovery process. It was experimentally defined, that the membrane-assisted gas absorption technique provides efficient recovery of NH3, and its concentration in permeate reach 98.96 vol% in the case of NH4SCN:G. Nevertheless, that DES couldn’t provide stable efficiency in contrast with less-viscosity DESes, such as NH4SCN:U and NH4SCN:EG. It was found that these absorbents allow achieving up to 98.42 and 98.7 vol% of NH3 in permeate.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Distillation/membrane process for high purification of Xe extracted from natural gas.•Experimental data on membrane gas separation for Xe-containing mixtures.•Novel process flowsheets for xenon high ...purification by a hybrid method.•Increased performance of the hybrid process compared to standalone distillation.
High-purity xenon of 6 N purity grade and higher is widely used in electronics, space, and medicine. A hybrid distillation/membrane process for the purification of xenon extracted from natural gas by gas hydrate crystallization is studied experimentally and via simulations. Membrane gas separation data for xenon-containing mixtures is measured for polysulfone membrane and polyetherimide/polyimide blend membrane. Parametric analysis and process optimization are performed in Aspen Plus Dynamics™ for a middle-vessel batch distillation column with an integrated hollow fiber membrane unit implemented via Aspen Custom Modeler™. Removal of higher- and lower-boiling impurities such as ethane, carbon dioxide, propane, methane, and krypton is considered to achieve 6 N and 9 N target purity grades. Hybrid distillation/membrane process flowsheets built with a multi-stream passive heat exchanger with either retentate or permeate being returned to the column are analysed. It is shown that the operating conditions and the configuration of the hybrid process with a membrane separation treatment of heavy impurities fraction can be tailored to achieve up to 30% increase in batch productivity for the considered case studies and improve xenon recovery reaching above 99.8% as compared to standalone batch distillation, which is especially critical for higher purity grades.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The present study deals with a comprehensive experimental evaluation of a unique hybrid method based on gas hydrate crystallisation and membrane gas separation, proposed as an alternative approach to ...Xenon (Xe) recovery from natural gas. The following operational modes were investigated: pressure-dropping mode, the constant pressure mode, continuous mode, continuous membrane-gas hydrate mode. The simulation was performed on a model gas mixture (CH4 (94.85 mol.%)/CO2 (5.00 mol.%)/Xe (0.15 mol.%)), which contains natural gas components, with an addition of a kinetic gas hydrate promoter – sodium dodecyl sulfate (0.30 wt%) at 272.15 and 274.15 K for 4 h in a pilot-scale gas hydrate crystalliser. The most optimal separation mode has been determined for Xe recovery from natural gas. The experimental efficiency has been evaluated based on the gas hydrate distribution coefficients, separation factors, and the gas hydrate recoveries values. The maximum Xe gas hydrate recovery is 93.05% based on the continuous membrane-gas hydrate separation at 272.15 K. The maximum mixture gas hydrate recovery is 40.05% based on the constant pressure separation at 272.15 K. Thus, the choice of the optimal separation mode for Xe recovery from natural gas is determined by the required degree of natural gas purification.
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•Gas hydrate crystallisation as an efficient method for Xe recovery from natural gas.•High-efficient Xe recovery was achieved at separating ternary CH4/CO2/Xe gas mixture.•Role of the membrane in a hybrid process of Xe recovery from natural gas is shown.•Maximum Xe gas hydrate recovery is 93.05% based on the continuous membrane-gas hydrate separation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Nickel(II) complexes with neutral bidentate nitrogen-containing ligands are of great interest as promising precatalysts for the selective oligomerization of ethylene. Complexes of compositions ...0.75LNiCl22•0.25LNiClBr22 and LNiBr23 where L = bis-(3,5-dimethylpyrazol-1-yl)methane have been synthesized and characterized by single crystal X-ray diffraction, IR and 1H NMR spectroscopies and elemental analysis. The 1H NMR spectra of paramagnetic complexes indicate that the structures of these complexes in solution are similar to ones in the solid state. Magnetic susceptibility of the compounds has been investigated and discussed in the context of their structures. Treatment of these complexes with diethylaluminum chloride (DEAC) or ethylaluminum sesquichloride (EASC) generates active catalysts that oligomerize ethylene to yield mostly butenes with activities up to 930 kg(oligomers)·molNi−1·h−1 (DEAC).
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•Two Ni (II) complexes with bis(3,5-dimethylpyrazol-1-yl)methane were synthesized.•Their structures have been determined by X-Ray in crystal and by 1H NMR in solution.•Ni (II) complexes activated with Et2AlCl or Et3Al2Cl3 selectively dimerize ethylene.•The selectivity towards 1-butene was up to 90.5 mol. %.•The maximum of catalytic activity reached 930 kg molNi−1·h−1.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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