1. Lipase-catalyzed transesterification of (R,S)-1-phenylethanol in SC $CO_2$ and in SC $CO_2$/ionic liquid systemsMuzafera 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: 2147; Prenosov: 175
 Celotno besedilo (446,49 KB)
Gradivo ima več datotek! Več... |
2. Enzyme-catalyzed acylation of (R,S)-1-phenylethanol in 1-butyl-3-methylimidazolium based ionic liquidsMuzafera 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: 2081; Prenosov: 127
Celotno besedilo (271,40 KB)
Gradivo ima več datotek! Več... |
3. Preparation of enantiomers using high pressure technologiesPaul Thorey, 2010, doktorska disertacija Opis: The study of two different methods of obtaining chiral alcohols is proposed herein.
The requirement of the relatively new paradigm of green chemistry associated with clean
technologies such as biocatalysis or non-conventional solvents, dense gases, was
focused at. Indeed, the two methods of production of chiral alcohols were:
- the conversion of acetophenone into (R)-1-phenylethanol in dense gases
catalysed by Lactobacillus brevis alcohol dehydrogenase and its
coenzyme, NADP/H;
- the resolution of (±)-trans-1,2-cyclohexanediol by cocrystal formation with
tartaric acid followed by supercritical extraction.
In both cases high enantiopurities were achieved (ee>99%).
Ključne besede: High-pressure technologies, enantiomers, green chemistry, R-1-phenylethanol, Lactobacillus brevis, alcohol dehydrogenase, NADP, liquid propane, enzyme deactivation, resolution, trans-1, 2-cyclohexanediol, tartaric acid, cocrystal, supercritical carbon dioxide, extraction, X-ray diffraction, differential scanning calorimetry
Objavljeno v DKUM: 02.02.2011; Ogledov: 2788; Prenosov: 130
Celotno besedilo (6,25 MB) |
