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High bulk modulus of ionic liquid and effects on performance of hydraulic system
Milan Kambič, Roland Kalb, Tadej Tašner, Darko Lovrec, 2014, izvirni znanstveni članek

Opis: Over recent years ionic liquids have gained in importance, causing a growing number of scientists and engineers to investigate possible applications for these liquids because of their unique physical and chemical properties. Their outstanding advantages such as nonflammable liquid within a broad liquid range, high thermal, mechanical, and chemical stabilities, low solubility for gases, attractive tribological properties (lubrication), and very low compressibility, and so forth, make them more interesting for applications in mechanical engineering, offering great potential for new innovative processes, and also as a novel hydraulic fluid. This paper focuses on the outstanding compressibility properties of ionic liquid EMIM-EtSO4, a very important physical chemically property when IL is used as a hydraulic fluid. This very low compressibility (respectively, very high Bulk modulus), compared to the classical hydraulic mineral oils or the non-flammable HFDU type of hydraulic fluids, opens up new possibilities regarding its usage within hydraulic systems with increased dynamics, respectively, systemsʼ dynamic responses.
Ključne besede: ionic liquids, hydraulic system, high bulk modulus
Objavljeno v DKUM: 15.06.2017; Ogledov: 1301; Prenosov: 383
.pdf Celotno besedilo (1,91 MB)
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Enzymatic esterification of glycerol and stearic acid in non-conventional media
Zsófia Csanádi, Katalin Bélafi-Bakó, Eszter Szentgyörgyi, László Gubicza, Željko Knez, Maja Leitgeb, 2010, izvirni znanstveni članek

Opis: Ionic liquids as trihexyl-tetradecyl-phophonium-dicyanamide (Cyphos 105) and cocosalkyl-pentaethoxi-methyl-ammonium-methosulfate (Ammoeng 100) were applied for the esterification of stearic acid and glycerol using Candida antarctica lipase (Novozyme 435). When only ILs were applied as solvents at 1:15 initial substrate molar ratio the conversion was 76 and 78 % in the case of two kinds of ILs, respectively. Mixed the ILs and supercritical $CO_2$ the conversion reached 79 and 86 %. The conversion was found highest in supercritical $CO_2$, reached 90 %. Moreover formation of glycerol-di-stearate is much lower in the case of ILs comparing with $SCCO_2$.
Ključne besede: glycerol-mono-stearate, Lipase, ionic liquids, supercritical $CO_2$, carbon dioxide
Objavljeno v DKUM: 10.07.2015; Ogledov: 1336; Prenosov: 168
.pdf Celotno besedilo (128,92 KB)
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Lipase-catalyzed transesterification of (R,S)-1-phenylethanol in SC $CO_2$ and in SC $CO_2$/ionic liquid systems
Muzafera Paljevac, Željko Knez, Maja Leitgeb, 2009, izvirni znanstveni članek

Opis: Commercial immobilized lipase B from Candida antarctica (CALB) was successfully applied to catalyzing the transesterification of (R,S)-1-phenylethanol in supercritical carbon dioxide and in supercritical carbon dioxide/ionic liquid biphasic system. Firstly, the variables affecting the performance of CALB in transesterification reactions in supercritical carbon dioxide, such as CALB concentration, temperature and pressure, were studied. An increase in the conversion and in the reaction rate was observed as the CALB/substrate ratio, temperature and pressure, were increased from 4.3 to 19.9, from 40 °C to 80 °C and from 8 MPa to 10 MPa, respectively. Further increase in temperature from 80 °C to 120 °C and pressure from 10 MPa to 30 MPa resulted in lower conversion and lower initial reaction rate. Furthermore, different vinyl esters were used as acyl donors for CALB-catalyzed transesterification of (R,S)-1-phenylethanol in supercritical carbon dioxide. The highest initial reaction rate was attained with vinyl butyrate, although 50% conversion was attained faster when vinyl acetate was used as acyl donor. Secondly, in transesterification of (R,S)-1-phenylethanol, performed in supercritical carbon dioxide/ionic liquid biphasic system, influence of concentration of 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF$_4$] was studied. The addition of 50 mmol (70% w/w reaction mixture) of [bmim][BF$_4$] to the reaction system gave the best result in terms of transesterification rate.
Ključne besede: candida antarctica lipase B, transesterification, (R, S)-1-phenylethanol, ionic liquids, vinyl acetate, supercritical carbon dioxide
Objavljeno v DKUM: 31.05.2012; Ogledov: 2365; Prenosov: 203
.pdf Celotno besedilo (446,49 KB)
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Enzyme-catalyzed acylation of (R,S)-1-phenylethanol in 1-butyl-3-methylimidazolium based ionic liquids
Muzafera Paljevac, Željko Knez, Maja Leitgeb, 2009, izvirni znanstveni članek

Opis: Ionic liquids represent an exciting new class of reaction solvents for catalysis, which have been used successfully for enzyme-catalyzed reactions. In present research, three different ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, and 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl)] amide, were synthesized. They were used as a reaction medium for enzyme-catalyzed acylation of (R,S)-1- phenylethanol with vinyl acetate. Mentioned enzymatic reaction was performed in a batch stirred-tank reactor in order to optimise different reaction parameters (biocatalyst concentration, temperature, ...). The influence of three different immobilized lipases on reaction performance was studied as well. The highest reaction rate and conversion of 49.7% after 5 h of reaction performance was achieved in the case when immobilized lipase Novozym 435 from Candida antarctica was used as a biocatalyst and hydrophilic ionic liquid 1-butyl- 3-methylimidazolium tetrafluoroborate as a solvent. Therefore, the optimization of different reaction parameters on lipase- catalyzed acylation of (R,S)-1-phenylethanol was carried out in 1-butyl-3-methylimidazolium tetrafluoroborate.
Ključne besede: immobilized lipase, acylation, (R, S)-1-phenylethanol, ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate
Objavljeno v DKUM: 31.05.2012; Ogledov: 2287; Prenosov: 150
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