| 1. |
- Mikkola, Jyri-Pekka, et al.
(författare)
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Ionic liquid-aided carboxymethylation of kraft pulp
- 2010
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Ingår i: International Journal of Chemical Reactor Engineering. - : Bepress. - 1542-6580. ; 8:A102
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Tidskriftsartikel (refereegranskat)abstract
- Different ionic liquids containing the cation such as 1-N-butyl-3-methylimida-zolium (Bmim+) are able to efficiently dissolve cellulose. The ability of ionic liquids to truly dissolve cellulose is significant when cellulose derivatization is attempted. A series of experiments on etherification (carboxymethylation) of cellulose was performed, using both the conventional suspension approach (slurry) with 2-propanol as the principal reaction media and a totally homogenous reaction approach utilizing ionic liquids as a reaction media capable of dissolving cellulose. It was observed that a pre-treatment with the ionic liquid 1-N-butyl-3-methylimidazolium iodide ([Bmim][I]) seems to promote substitution in line with the conventional, heterogeneous suspension process. Under carefully chosen reaction conditions, a higher degree of substitution was obtained when wetting the cellulose with [Bmim][I] prior to classical derivatization than without this pre-treatment. It was also observed that the substitution pattern was changing upon use of the ionic liquid [Bmim][I]. Upon a totally homogenous etherification, it was found that the ionic liquid 1-N-butyl-3-methylimidazolium acetate ([Bmim][oAc]) gave the highest degree of substitution. The product obtained was water-soluble and had a DS (degree of substitution) of 0.59. The substitution pattern of the products obtained from the homogenous reactions follow the same substitution pattern as the products obtained from the conventional suspension process. This indicates that the properties of the products are in line with products prepared via the conventional reaction route.
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| 2. |
- Möller, K.P., et al.
(författare)
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The catalytic evaluation of structured zeolite catalysts
- 2004
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Ingår i: International Journal of Chemical Reactor Engineering. - : Walter de Gruyter GmbH. - 1542-6580. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- ZSM-5 films, with thicknesses between 150 and 2300 nm, supported on 3 mm diameter alumina beads are characterised in terms of their catalytic activity and selectivity for tri-isopropylbenzene cracking and para-xylene isomerisation at 450°C. A reaction-diffusion model adequately represents the experimental data and is used to estimate intrinsic reactivity and diffusion properties of the zeolite films. Results show that the external activity, overall activity and the diffusivity increase with increasing film thickness. The variation in reactivity and diffusivity, when compared to physio-chemical data, are a result of structural defects and non-homogeneities of the zeolite film. The measured diffusivities are within an order of magnitude of those extrapolated from literature. Thick zeolite films have the largest Thiele modulus as the increase in zeolite film thickness dominates over the structural defects. The largest selectivity improvements are observed for thick zeolite films
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| 3. |
- Wang, Haijuan, et al.
(författare)
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Modelling of Physico-Chemical Phenomena between Gas inside a Bubble and Liquid Metal during Injection of Oxidant Gas
- 2010
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Ingår i: International Journal of Chemical Reactor Engineering. - : Walter de Gruyter GmbH. - 1542-6580. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Gas liquid reactors are extensively used in many metallurgical processes involving the refining of liquid metals. In these processes, reactions leading to the oxidation of various solutes in liquid metal often compete with each other, which ultimately determine the liquid metal composition. In the present paper, a model has been proposed to simulate the evolution of solute contents in a metallic melt considering mass transfer of solutes in the melt in the vicinity of the bubble, equilibrium at the gas-metal interface and gas composition evolution in the bubble during its ascent through the melt. The composition of solutes at the metal-gas interface in principle can be altered by changing the injected gas composition.The model was applied to the case of oxygen injection through a lance into liquid steel-containing C and Cr, aiming sufficient decarburization without much oxidation of Cr to the slag. The Cr loss to the slag by oxidation is generally much more than that expected based on equilibrium thermodynamics applied to the bulk metal and gas. The actual Cr loss, as shown by the present model, is determined by the composition of solutes at the metal-gas interface rather than in the bulk. The effect of change of the partial pressure of oxygen in the bubble by replacing oxygen by carbon dioxide in the injected gas and the corresponding evolution of C and Cr contents in the melt was simulated. Some preliminary experiments were conducted to validate the model predictions. The frame work of the model is generic and can be extended to many gas-liquid metal reactors in liquid metal processing.
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| 4. |
- Huang, B. T., et al.
(författare)
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Towards Production of gamma-valerolactone via Hydrogenation of Aqueous Levulinic Acid
- 2015
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Ingår i: International Journal of Chemical Reactor Engineering. - : Walter de Gruyter GmbH. - 1542-6580 .- 2194-5748. ; 13:1, s. 119-127
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis of GVL (gamma-valerolactone) via hydrogenation of aqueous LA (levulinic acid) with H-2 over heterogeneous catalyst (Ru/C) was investigated. In the first part, a study of the influence of various operating conditions was conducted including that of temperature (90-180 degrees C), stirring rate (500-1200 rpm), catalyst loading (0.1-2.0 g), hydrogen pressure (0.4-2.8 MPa) and initial LA concentration (0.5-2 M). In the second part, influence of supercritical CO2 (scCO(2)) on hydrogenation rate and GVL yield were investigated. Hydrogenation of aqueous LA under scCO(2) and under N-2 atmosphere was carried out in batch reactor at 150 degrees C and was compared with the case when no additional gases were present. The result indicated that the use of scCO(2) had no beneficial effect neither in terms of LA conversion nor hydrogenation rate when the amount of hydrogen was relatively low compared to the stoichiometry. This effect was mitigated when more hydrogen was present.
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| 5. |
- Ström, Henrik, 1981, et al.
(författare)
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Behaviour and stability of the two-fluid model for fine-scale simulations of bubbly flow in nuclear reactors
- 2015
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Ingår i: International Journal of Chemical Reactor Engineering. - : Walter de Gruyter GmbH. - 1542-6580 .- 2194-5748. ; 13:4, s. 449-459
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, we formulate a simplistic two-fluid model for bubbly steam-water flow existing between fuel pins in nuclear fuel assemblies. Numerical simulations are performed in periodic 2D domains of varying sizes. The appearance of a non-uniform volume fraction field in the form of meso-scales is investigated and shown to be varying with the bubble loading and the domain size, as well as with the numerical algorithm employed. These findings highlight the difficulties involved in interpreting the occurrence of instabilities in two-fluid simulations of gas-liquid flows, where physical and unphysical instabilities are prone to be confounded. The results obtained in this work therefore contribute to a rigorous foundation in on-going efforts to derive a consistent meso-scale formulation of the traditional two-fluid model for multiphase flows in nuclear reactors.
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