Showing papers on "Transesterification published in 1990"
TL;DR: In this article, the microalgae are used to extract storage lipids in large quantitites and thrive in saline waters, and these lipids can then be converted into usable fuel.
Abstract: Microalgae are unique photosynthetic organisms that are known to accumulate storage lipids in large quantitites and thrive in saline waters. Before these storage lipids can be used, they must be extracted from the microalgae and converted into usable fuel. Transesterification of lipids produces fatty acid methyl esters that can be used as a diesel fuel substitute.
231 citations
TL;DR: In this article, the extent of transesterification reactions was calculated on the basis of the analysis of the methine carbon signal in the polymer 13C NMR spectra, and three groups of initiators can be distinguished in view of their influence on transesterion.
Abstract: Racemic lactide was polymerized with various initiators containing Zn and Al, and the structures of the obtained polymers were determined by means of 13C NMR spectroscopy. The extent of transesterification reactions was calculated on the basis of the analysis of the methine carbon signal in the polymer 13C NMR spectra. Three groups of initiators can be distinguished in view of their influence on transesterification: ZnCl2 exhibits the strongest transesterification activity, ZnEt2 and ZnEt2/Al(OiPr)3 are among those of medium activity, and Al(acac)3 does not show transesterification activity at all.
171 citations
TL;DR: The results presented here demonstrate the absolute necessity to consider the polarity of every substrate, because of its ability to modify the water partition between the solid phase (enzyme preparation) and the liquid phase (substrate and product), which results in drastic changes in enzyme activity.
Abstract: The reaction rate of two lipase-catalysed reactions, esterification and transesterification, were studied in a liquid/solid two-phase system in order to investigate the effect of water partition between the enzyme preparation and the liquid phase composed of only the reactants, i.e. without the conventional solvents.
Lipase from Candida cylindracea was used for these studies. The enzyme was inactive in dehydrated systems. In the case of monoester synthesis, the reaction rate increased with increasing water activity. The reaction rates of the non-specific C. cylindracea lipase-catalysed reactions were very sensitive to the nature of the substrates in this unusual system. For instance, the transesterification reaction rate of ethyl propionate was 48 times higher with nonanol than heptanol in the case of dehydrated substrates, but only 2.2 times higher in the case of watersaturated substrates. The results presented here demonstrate the absolute necessity to consider the polarity of every substrate, because of its ability to modify the water partition between the solid phase (enzyme preparation) and the liquid phase (substrate and product), which results in drastic changes in enzyme activity.
Contrary to esterification, which is known to be activated by the water produced, the rate of transesterification remained constant at the beginning of the reaction. However, when transesterification and esterification were carried out in the same liquid phase, the transesterification reaction rate was controlled by the water produced by the concomitant esterification. Activation effects of the water molecules produced during the enzymatic reaction were of exactly the same order of magnitude for both reactions.
97 citations
TL;DR: The results of the rate measurements suggest that the primary role of the support materials is the activation of the enzymes and the increase in substrate concentration at reaction sites, and that the enzymes maintain their native conformations in these low-water organic solvents.
86 citations
TL;DR: The lipase immobilized on EP-400 polyethylene was found to be effective in transesterification using tributyrin or triacetin as acyl donors with l-menthol as acceptor and enhanced in the presence of Amberlite IR 47 Anion exchange resin (OH form).
78 citations
TL;DR: In this article, the authors investigated the lipase-catalyzed transesterification of tributyrin with various alcohols in a heterogeneous system using powdered enzyme suspended in numerous organic solvents.
65 citations
TL;DR: In this paper, the influence of transesterification on the miscibility of binary blends of poly(ethylene terephthalate) and poly(bisphenol-A carbonate) was investigated.
Abstract: A study has been made of the influence of transesterification on the miscibility in binary blends of poly(ethylene terephthalate) and poly(bisphenol-A carbonate). The blends were melt mixed in the range 260–300°C and studied by differential scanning calorimetry, dynamic mechanic analysis, and by Fourier transform infrared spectrometry. It was found that copolymer produced by a transesterification reaction can enhance the miscibility of this system. The new compositions were uniquely identified by FTIR. Gel permeation chromatography showed that molecular weight decreases were not the origin of miscibility. The ester exchange reaction itself was found to be initiated by the residual catalyst in the commercial polymers selected for study. This has been shown by the absence of reaction after polymer purification by solution and reprecipitation prior to melt mixing.
64 citations
TL;DR: Proper procedures for the preparation of XAD-8 immobilized lipoprotein lipase and the resolution of secondary alcohols of synthetic value in organic solvents using this immobilized enzyme have been developed.
59 citations
58 citations
TL;DR: Acrylate monoesters were synthesized on a preparative scale by the regioselective enzymatic transesterification of a range of diols dissolved in ethyl acrylate using a commercial lipase fromchromobacteriumviscosum.
Abstract: Acrylate monoesters were synthesized on a preparative scale by the regioselective enzymatic transesterification of a range of diols dissolved in ethyl acrylate using a commercial lipase fromChromobacteriumviscosum.
57 citations
01 Jan 1990
TL;DR: The acyl migration was not observed in the enantioselective transesterification of meso-1,3-diols in neutral organic solvents and a mechanism of the migration has been proposed to proceed through a six-member ring transition that accounts for the experimental results.
Abstract: In the enantioselective hydrolysis of the di-O-acetyl derivatives of meso-1,3-diol catalyzed by lipases, racemization of the monoacetate products occurs due to non-enzymatic general base-catalyzed acyl migration. The rate of acyl migration increases with increase of pH and buffer concentration. A mechanism of the migration has been proposed to proceed through a six-member ring transition that accounts for the experimental results. The acyl migration, however, was not observed in the enantioselective transesterification of meso-1,3-diols in neutral organic solvents.
TL;DR: Lipases were used as catalysts in the synthesis of “all‐trans” polyester oligomers in organic solvents and the alkoxy leaving group of the ester fumarate was found to be responsible for the rate of transesterification.
Abstract: Lipases were used as catalysts in the synthesis of “all-trans” polyester oligomers in organic solvents. Esters of fumaric acid and 1,4-butane diol served as the substrates in the enzyme-catalyzed polytransesterification. No isomerization of the double bond was found under the mild conditions of enzymatic catalysis used by us, as opposed to the extensive isomerization found during chemical polycondensation. The alkoxy leaving group of the ester fumarate was found to be responsible for the rate of transesterification. Low (Mw ≃ 600–800) and high (Mw = 1250) molecular weight alkyds were synthesized depending on whether tetrahedrofuran or acetonitrile, respectively, was used as the solvent.
TL;DR: Lipase-catalyzed transesterification of 2-methyl-1,3-propanediol 1 in chloroform affords enantiomerically pure (S)-(−)-acetate 2, from which the (R)-(+)-silyl ethers 4a-b can be efficiently prepared (>98% ee).
TL;DR: The 50-fold increase in the rate of synthesis of benzyloxycarbonyl-l-serine- l-phenylalanine amide which was observed when PEG-subtilisin was used instead of immobilized or powdered enzyme, suggested that a higher flexibility of the polypeptide chain modified by the covalent attachment of a number of soluble PEG moieties occurred in organic solvents.
Abstract: Subtilisin from Bacillus subtilis was modified with polyethylene glycol (PEG), or adsorbed either on celite or porous glass, or directly used as a suspended powder to catalyse peptide synthesis and transesterification reactions in organic solvents. The rather low yield of peptide synthesis probably resulted from the enzyme tendency to catalyse hydrolysis and transesterification side reactions. The kinetics of transesterification catalysed by PEG-subtilisin was consistent with a ping-pong mechanism modified by a hydrolytic branch. Initial rates of transesterification were found to be dependent on alcohol and organic base concentrations in the reaction mixture. The high affinity of benzyloxycarbonyl-l-serine-methyl ester for the enzyme indicated that a change in substrate specificity of subtilisin occurred in organic phase. The 50-fold increase in the rate of synthesis of benzyloxycarbonyl-l-serine-l-phenylalanine amide which was observed when PEG-subtilisin was used instead of immobilized or powdered enzyme, suggested that a higher flexibility of the polypeptide chain modified by the covalent attachment of a number of soluble PEG moieties occurred in organic solvents. This also resulted in a lower stability of PEG-subtilisin at high temperature.
Patent•
15 Mar 1990
TL;DR: A process for the production of terephthalate diesters having the following formula (I) is described in this article, which is particularly useful for recycling scrap polyester products.
Abstract: A process for the production of terephthalate diesters having the following formula (I). ##STR1## Substituents R and R' are the same or different and represent a straight chain, branched or cyclic aliphatic group, an aromatic group, an alkaryl group or an aralkyl group, each group having from 6 to 20 carbon atoms. The process involves reacting a terephthalate polyester with a high molecular weight alcohol or a mixture of high molecular weight alcohols each having from 6 to 20 carbon atoms, in the presence of a catalyst and recovering the desired compound according to formula (I). This process is particularly useful for recycling scrap terephthalate polyester products such as those produced from polyethylene terephthalate (PET), crystallized polyethylene terephthalate (CPET), glycol-modified polyethylene terephthalate copolyester (PETG), polybutylene terephthalate (PBT), polycyclohexanedimethylene terephthalate (PCT), as well as the acid- and glycol-modified copolyesters of PCT, respectively PCTA and PCTG.
Patent•
09 Feb 1990TL;DR: In this paper, the authors present a process for the synthesis of polyol fatty acid esters by reacting a polyol and a fatty acid loweralkyl ester under substantially solvent-free conditions in the presence of a transesterification catalyst and an emulsifier.
Abstract: The present invention pertains to a process for the synthesis of polyol
fatty-acid esters by reacting a polyol and a fatty-acid lower-alkyl ester
under substantially solvent-free conditions in the presence of a
transesterification catalyst and an emulsifier. The process comprises a
continuous initial reaction stage in a first reaction zone wherein a steady-
state conversion is achieved of over 1 % and a further reaction stage in
which the reaction mixture from said first zone is further reacted to the
required polyol fatty-acid esters in one or more subsequent reaction zones.
TL;DR: In this article, the kinetics of the melt transesterification of diphenyl carbonate with 4,4-dihydroxydiphenyl-2,2-propane has been studied in a batch reactor with LiOH · H2O as a catalyst in the temperature range of 150-180°C.
Abstract: The kinetics of the melt transesterification of diphenyl carbonate with 4,4-dihydroxydiphenyl-2,2-propane has been studied in a batch reactor with LiOH · H2O as a catalyst in the temperature range of 150–180°C. The third-order forward and backward rate constants were determined experimentally and a linear dependence of the transesterification rate on the catalyst concentration was observed. The product oligomer concentration distribution has also been measured experimentally and estimated by the molecular species model which describes the progress of the melt transesterification.
TL;DR: Porcine pancreatic lipase-catalysed transesterifications of 2,2,2-trifluoroethyl butyrate with racemic 2-octanol and 1-phenylethanol with Candida cylindracea lipase is active only in the most hydrophobic solvents studied.
Abstract: Porcine pancreatic lipase-catalysed transesterifications of 2,2,2-trifluoroethyl butyrate with racemic 2-octanol and 1-phenylethanol have been studied in different organic solvents. Solvent hydrophobicity (log P -1.1 to 3.3) has only a minor effect on the reaction rate. Independently of the solvent used as the reaction medium, both (R)-2-octyl and (R)-1-phenylethyl butyrates were obtained in high optical purity (ee greater than 90%). Candida cylindracea lipase is active only in the most hydrophobic solvents studied.
TL;DR: In this article, a selective esterification of acetic acid with α olefins and isobutylene was carried out in the presence of cation exchange resins used as catalysts in the temperature range of 10 to 100°C depending on the nature of the olefin used.
TL;DR: In this paper, meso-bis(acetoxymethyl)aziridines of high enantiomeric purity were obtained through enzymatic transesterification of meso-, 3S-, 2R, 3S)-2-Acetoxylmethyl-3-hydroxymethylazirizines.
Patent•
29 Jan 1990
TL;DR: In this paper, the transesterification of polyacrylate alkyl esters with long-chain hydrocarbon and polyoxyalkylene groups was described, which were obtained by free radical polymerization.
Abstract: Polyacrylate esters with long-chain hydrocarbon and polyoxyalkylene groups are disclosed, which are prepared by transesterification of polyacrylate alkyl esters, the alkyl groups of which have 1 to 4 carbon atoms and which were obtained by free radical polymerization, wherein the transesterification is carried out with a mixture of selected alcohols and polyoxyalkylene monools. Compared to products obtained by copolymerization, the transesterification products are largely free of undesirable low molecular weight components, have a narrow molecular weight distribution and exhibit excellent surfactant properties. They are useful especially as W/O emulsifiers for natural and synthetic oils.
TL;DR: Free subtilisin Carlsberg catalyzes the ester formation reaction from N-acetylated aromatic amino acids in alcohols containing small amounts of water, and is also an effective catalyst for transesterification of N- acetyl- l -tyrosine methyl ester to ethyl ester.
TL;DR: In this article, a pig liver esterase was used for both hydrolysis and transesterification reactions of methyl and ethyl esters of acrylic and methacrylic acids.
Patent•
03 Apr 1990TL;DR: In this paper, the authors proposed a method for the production of high-purity fatty acid lower-alkyl mono-esters, which comprises a first transesterification step between glycerol fatty acid esters and a lower alcohol, a separation step wherein the reaction product of the esterification step is separated into glycerolic-rich and fatty-acid lower-acid mono-ester rich fractions, and a second estersification step in which all glycerols and fatty acid glycerolesters of the fatty acid triglycerolesters are esterified to the corresponding
Abstract: The invention pertains to the production of high-purity fatty-acid lower-alkyl mono-esters which comprises a first transesterification step between glycerol fatty-acid esters and a lower alcohol, a separation step wherein the reaction product of the esterification step is separated into glycerol-rich and fatty-acid lower-alkyl mono-ester rich fractions, a second esterification step in which all glycerol and fatty-acid glycerolesters of the fatty-acid lower-alkyl mono-ester rich fraction are esterified to the corresponding fatty-acid triglycerolesters, and a recovery step wherein said fatty-acid lower-alkyl mono-esters are recovered.
TL;DR: Transesterification between ethyl butyrate and glycerol using very different lipase preparations in a two-phase system—no extra solvent added—has been investigated and only monobutyrin was produced in all conditions tested.
Abstract: Transesterification between ethyl butyrate and glycerol using very different lipase preparations (native, modified, and immobilized) in a two-phase system—no extra solvent added—has been investigated. Optimal conversion was obtained with the presence of 5% water in the reaction mixture. Only monobutyrin was produced in all conditions tested. The best enzyme preparations were nativeCandida cylindracea lipase,Mucor miehei lipase immobilized on a phenol-formaldehyde exchange resin (Lipozyme™), andC. cylindracea lipase immobilized on Celite.
TL;DR: Porcine pancreatic lipase catalyses the enantioselective transesterification of β, γ-, and δ-hydroxy sulfones with 2,2,2-trichloroethyl butyrate in ethyl ether as discussed by the authors.
Abstract: Porcine pancreatic lipase catalyses the enantioselective transesterification of β, γ-, and δ-hydroxy sulfones with 2,2,2-trichloroethyl butyrate in ethyl ether.
TL;DR: The reactor for synthesis of this tripeptide was efficient and stable because of the use of transesterification and the choice of an appropriate organic solvent and the equilibrium between the water concentration in the reaction solution and that in the resin used for enzyme immobilization depended on the resin and was not affected by the presence of the enzyme immobilized.
Abstract: The tripeptide Z-GlyPheLeuNH2 was continuously synthesized in a high yield from three amino acid derivatives, Z-Gly, PheOMe, and LeuNH2, by immobilized thermolysin (IMT) and immobilized alpha-chymotrypsin (IMC) in an organic solvent, ethyl acetate. The optimal conditions for the synthesis of Z-GlyPheOMe were established theoretically. The yield of Z-GlyPheOMe with IMT in ethyl acetate saturated with buffer was more than 88% after continuous synthesis for 116 hr. The optimal conditions for the synthesis of Z-GlyPheLeuNH2 from Z-GlyPheOMe and LeuNH2 by IMC through transesterification was established in batch reaction experiments. When the concentration of water in the reaction solution was 17-20 microliters/ml, the activity of IMC was highest. The equilibrium between the water concentration in the reaction solution and that in the resin used for enzyme immobilization depended on the resin and was not affected by the presence of the enzyme immobilized. Z-GlyPheLeuNH2 was synthesized from Z-GlyPheOMe and LeuNH2 with a yield of 100%, by continuous reaction for 160 hr. The reactor for synthesis of this tripeptide was efficient and stable because of the use of transesterification and the choice of an appropriate organic solvent. The series plug-flow reactor was successfully operated for 220 hr with a yield of more than 80%. The residual activity of IMT was 94% and that of IMC was 100%.