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1.
Hydrogen production using a thermochemical cycle
Jurij Avsec, Urška Novosel, Dušan Strušnik, 2022, original scientific article

Abstract: Sustainable methods of clean fuel production are needed throughout the world due to depleting oil reserves and the need to reduce carbon dioxide emissions. The technology based on fuel cells for electricity production or the transport sector has already been developed. However, a key missing element is a large-scale method of hydrogen production. The copper-chlorine (CuCI) combined thermochemical cycle is a promising thermochemical cycle that can produce large amounts of cheap hydrogen. A particularly promising part of this process is its use in combination with nuclear or thermal power plants. This paper focuses on a CuCl cycle and describes the models used to calculate thermodynamic and transport properties. This paper discusses the mathematical model for computing the thermodynamic properties for pure HCl and CuCl2. The mathematical model developed for the solid phase takes into account vibrations of atoms in molecules and intermolecular forces. This mathematical model can be used for the calculation of the thermodynamic properties of polyatomic crystals on the basis of the Einstein and Debye equations. The authors of this paper developed the model in the low temperature and high temperature region. All the analytical data have been compared with some experimental results and show a relatively good match. For the solid phase, the authors developed a model to calculate thermal conductivity based on electron and phonon contributions.
Keywords: thermodynamics, energy, hydrogen production, solid phase, fluid phase
Published in DKUM: 30.10.2023; Views: 315; Downloads: 5
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2.
Weakly coupled analysis of a blade in multiphase mixing vessel
Matej Vesenjak, Zoran Ren, Matjaž Hriberšek, 2004, other scientific articles

Abstract: Two or more physical systems frequently interact with each other, where the independent solution of one system is impossible without a simultaneous solution of the others. An obvious coupled system is that of a dynamic fluid-structure interaction. š8đ In this paper a computational analysis of thefluid-structure interaction in a mixing vessel is presented. In mixing vessels the fluid can have a significant influence on the deformation of blades during mixing, depending on speed of mixing blades and fluid viscosity.For this purpose a computational weakly coupled analysis has been performed to determine the multiphase fluid influences on the mixing vessel structure. The multiphase fluid field in the mixing vessel was first analyzed with the computational fluid dynamics (CFD) code CFX. The results in the form of pressure were then applied to the blade model, which was the analysed with the structural code MSC.visualNastran forWindows, which is based on the finiteelement method (FEM).
Keywords: fluid mechanics, solid mechanics, coupled problems, computational analysis, two-phase fluid, mixing blade, pressure distribution, finite volume method, finite element method
Published in DKUM: 01.06.2012; Views: 1803; Downloads: 92
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3.
4-vinylbenzyl chloride based porous spherical polymer supports derived from water-in-oil-in-water emulsion
Dejan Štefanec, Peter Krajnc, 2005, original scientific article

Abstract: 4-Vinylbenzyl chloride (VBC) based water-in-oil-in-water emulsions with 85% pore volume and 70% VBC in organic phase were prepared and polymerised by free radical polymerisation. Porous spherical particles of diameters between 50 and 150 m were obtained and their morphological structure and reactivity studied by FTIR spectroscopy, elemental analysis, optical microscopy, scanning electron microscopy and mercury intrusion porosimetry. Strong influence of the suspension stabiliser, namely poly(N-vinylpyrrolidone) (PVP), on the particle form was found. Diameters of spherical polymers particles depend on the PVP concentration, being larger with the lower concentration of PVP. Reactivity of novel supports was demonstrated by the reactions with piperidine, piperazine, tris(hydroxymethyl)methylamine and tris(2-aminoethyl)amine, all yielding corresponding amine derivatives.
Keywords: multiple emulsions, polymer supports, 4-vinylbenzyl chloride, solid phase synthesis, solid phase synthesis, high internal phase emulsions
Published in DKUM: 01.06.2012; Views: 2093; Downloads: 45
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4.
PolyHIPE supports in batch and flow-through Suzuki cross-coupling reactions
Jane F. Brown, Peter Krajnc, Neil R. Cameron, 2005, original scientific article

Abstract: As part of ongoing research efforts to discover alternative support materials to polymer beads for use in polymer-supported synthesis, particularly under flow-through conditions, this work involves the synthesis of PolyHIPE (High Internal Phase Emulsion) polymer monoliths. PolyHIPEs containing high loadings of chloromethyl groups were efficiently prepared by the direct copolymerization of 4-vinylbenzyl chloride and divinylbenzene monomers. The 'Merrifield' PolyHIPE proved to be an excellent support for batch and flow-through Suzuki cross-coupling reactions. A remarkably high yield of pure biaryl product was obtained using the PolyHIPE support in cubic form and utilizing an electron-rich boronic acid. In comparison to polymer beads, this material was found to be a much more efficient support in both batch and continuous flow modes. PolyHIPE converted a greater amount of chloromethyl groups into biaryl product under identical reaction conditions. It is suggested that the absence of channelling with PolyHIPE monoliths gives better performance under flow-through conditions than permanently porous beads.
Keywords: polymer supports, polymer monoliths, emulsion polymerisation, solid-phase synthesis, cross-coupling reactions
Published in DKUM: 01.06.2012; Views: 2315; Downloads: 101
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5.
Atrazine removal by covalent bonding to piperazine functionalized PolyHIPEs
Irena Pulko, Mitja Kolar, Peter Krajnc, 2007, original scientific article

Abstract: The removal of atrazine from water by a solid phase extraction technique usinginsoluble polymers is described. Porous crosslinked polymers bearing piperazine moieties were prepared in a one step reaction from the precursor 4-nitrophenylacrylate incorporating polymers (PolyHIPE type prepared by the polymerization of the continuous phase of a high internal phase emulsion and polymer beads prepared by suspension polymerization). Polymers were applied tosequester atrazine from aqueous solutions with a concentration of 33 ppb andirreversible covalent bonding to the polymers was achieved. GC/MS/MS was used to monitor the dynamics of atrazine uptake and it was found that almost complete removal of atrazine was acomplished with an excess of polymer after 48 hours at room temperature. For comparison, polymer beads of identical chemistry but lower porosity were also used and showed significantly slower action (near complete removal after 72 hours).
Keywords: polymer supports, polymer scavengers, monoliths, emulsion polymerisation, solid-phase synthesis
Published in DKUM: 31.05.2012; Views: 2507; Downloads: 103
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6.
Aryl acrylate porous functional polymer supports from water-in-oil-in-water multiple emulsions
Dejan Štefanec, Peter Krajnc, 2007, original scientific article

Abstract: Porous functional polymer supports are a class of material of wide interest due to the possibility of immobilising reactive species. A simplified procedure was applied for the preparation of porous polymer supports using a water-in-oil-in-water multiple emulsion. The primary emulsion was a high internal phase emulsion, having a volume fraction of water phase up to 95%. Two reactive acrylates, namely 4-nitrophenyl acrylate and 2,4,6-trichlorophenyl acrylate, were (separately) incorporated in the oil phase in order to obtain porous reactive polymer supports. Both acrylates were crosslinked with either divinylbenzene or ethylene glycol dimethacrylate, and beads of size ca 60 m were obtained after the polymerisation of droplets suspended into the secondary aqueous phase. In the case of 4-nitrophenyl acrylate and divinylbenzene as a crosslinker, particles with a star shape, the core being ca 60 m in diameter and the arms ca 180 m in length, were obtained. The polymers were functionalised with morpholine, tris(2-aminoethyl)amine, piperidine or piperazine yielding supports with loadings of reactive groups of between 2.6 and 6.6 mmol g-1. The results show that multiple emulsions can be precursors for porous polymer preparation.
Keywords: multiple emulzije, polimerni nosilci, HIPE, organska sinteza na trdni fazi, polimerni lovilci, emulzija z visokim deležem notranje faze, aril akrilati, multiple emulsions, polymer supports, HIPE, solid phase organic synthesis, polymer supported scavengers, high internal phase emulsions, arylacrylates
Published in DKUM: 31.05.2012; Views: 2810; Downloads: 114
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