Showing papers on "Transesterification published in 1995"

1H nuclear magnetic resonance determination of the yield of the transesterification of rapeseed oil with methanol

Abstract: The formation of fatty acid methyl esters by transesterification with methanol can be monitored by1H nuclear magnetic resonance spectroscopy; this accurate determination is simpler than chromatographic methods

Chemoselective catalytic oxidation of glycerol with air on platinum metals

Abstract: The transesterification of triglycerides extracted from oilseeds to obtain biodiesel fuel yields up to 14% by weight of glycerol as by-product. The liquid-phase oxidation of glycerol with air on platinum catalysts was investigated to prepare valuable oxidation products such as glyceric acid or dihydroxyacetone. The effect of the pH (pH range 2–11) and of different metal catalysts was studied. The selectivity to glyceric acid can be as high as 70% at 100% conversion on Pd/C at pH 11. On Pt/C catalyst, glyceric acid was still the main product (55% selectivity); but the deposition of bismuth on platinum particles orientates the selectivity towards the oxidation of the secondary hydroxyl group to yield dihydroxyacetone with a selectivity of 50% at 70% conversion.

Alkylguanidines as catalysts for the transesterification of rapeseed oil

Abstract: The transesterification of rapeseed oil with methanol has been studied in the presence of eight substituted cyclic and acyclic guanidines and compared with unsubstituted guanidine. The catalytic activity of the guanidines depends mainly on their intrinsic base strength. With a long alkyl chain on the guanidine, no lipophilic effect is observed. The best catalyst found is commercial 1,5,7-triazabicyclo[4.4.0] dec-5-ene which, when used at 1 mol%, produces a 90% yield of methyl esters with 1 h of reaction time.

Ethanolysis of rapeseed oil: Quantitation of ethyl esters, mono‐, di‐, and triglycerides and glycerol by high‐performance size‐exclusion chromatography

Abstract: High-performance size-exclusion chromatography (HPSEC) was used to evaluate the influence of different variables affecting the transesterification of rapeseed oil (RSO) with anhydrous ethanol and sodium ethoxide as catalyst. The effect of temperature, ethanol/RSO molar ratio, catalyst concentration, and time can be interpreted by observing the variations of the reaction medium composition. HPSEC has made the quantitation of ethyl esters, mono-, di-, and triglycerides and glycerol possible. The best results for laboratory-scale reactions were obtained at 80°C with a 6:1 molar ratio of EtOH/RSO and 1% of NaOEt by weight of RSO.

Enzymatic transesterification of palm olein with nonspecific and 1,3-specific lipases.

Abstract: The enzymatic transesterification of palm olein was conducted in a low-moisture medium with nonspecific and 1,3-specific lipases from microbial sources. The enzymes were first immobilized on Celite, lyophilized for 4 h and then added to a reaction medium that consisted of 10% (wt/vol) palm olein in water-saturated hexane. The catalytic performance of the enzymes was evaluated by determining the changes in triglyceride (TG) composition and concentrations by reverse-phase high-performance liquid chromatography (HPLC) and the formation of free fatty acids by titration. Studies with lipase fromCandida rugosa showed that the degree of hydrolysis was reduced by drying the immobilized preparation and that the best drying time was 4 h. In all cases, the transesterification process resulted in the formation of PPP, a TG initially undetected in the oil, and increases in the concentrations of OOO (1.3–2.1-fold), OOL (1.7–4.5-fold), and OLL (1.7–4.3-fold), where P, O, and L are palmitic, oleic, and linoleic acids, respectively. SOS (where S is stearic acid), another TG not detected in the oil, was synthesized byRhizomucor miehei andPseudomonas lipases, with the latter producing more of this TG. There was a corresponding decrease in the concentrations of POP, PLP, POO, and POL. PPP concentration ranged from 1.9% (w/w) forMucor javanicus lipase to 6.2% (w/w) forPseudomonas lipase after 24 h. The greatest degree and fastest rate of change were caused byPseudomonas lipase, followed by the enzymes fromR. miehei andAspergillus niger. The effects of transesterification and hydrolysis of palm olein by the various lipases resulted in changes in the overall degree of saturation of the triglyceride components. There seems to be no clear correlation between the enzyme positional specificity and the products formed. Possible mechanisms for the formation of PPP, OOL, OLL, OOO, and SOS are discussed.

Biocatalytic synthesis of acrylates in organic solvents and supercritical fluids: III. Does carbon dioxide covalently modify enzymes?

Abstract: We have previously demonstrated that the activity of the lipase (Candida cylindracea) catalyzed transesterification reaction between methylmethacrylate and 2-ethylhexanol in supercritical carbon dioxide is comparatively low. In this article, we have investigated the same reaction in supercritical carbon dioxide with a special emphasis on determining the extent of any interaction between the enzyme and carbon dioxide. Transesterification reaction rates in hexane and supercritical carbon dioxide are compared at different temperatures. In supercritical carbon dioxide, temperature was found to have no significant effect on reaction rate in the range of 40 degrees to 55 degrees C. Above 55 degrees C, however, the reaction rate increased significantly as a function of temperature. It appears that carbon dioxide forms reversible complexes with the free amine groups on the surface of the enzyme. Direct evidence of modification was obtained using mass spectroscopy to detect the extent of modification of a pure protein. The kinetics of the reaction have been studied in hexane, and they obey a ping-pong bi-bi mechanism with inhibition by 2-ethylhexanol. The effect of bubbling carbon dioxide and/or fluoroform on the reaction rate in hexane at different temperatures suggests that the enzyme undergoes shear inactivation in hexane. (c) 1995 John Wiley & Sons, Inc.

Do organic solvents affect the catalytic properties of lipase? Intrinsic kinetic parameters of lipases in ester hydrolysis and formation in various organic solvents

Abstract: When it is assumed that organic solvents do not interfere with the binding process nor with the catalytic mechanism, the contribution of substrate-solvent interactions to enzyme kinetics can be accounted for by just replacing substrate concentrations in the equations by thermodynamic activities. It appears from the transformation that only the affinity parameters (K(m), K(sp)) are affected by this. Thus, in theory, the values of these corrected, intrinsic parameters (K(m) (int), k(sp) (int)) and the maximal rate (V(1)) should be equal for all media. This was tested for hydrolysis, transesterification, and esterification reactions catalyzed by pig pancreas lipase and Pseudomonas cepacia lipase in various organic solvents. Correction was carried out via experimentally determined activity coefficients for the substrates in these solvents or, if not feasible, from values in data bases. However, although the kinetic performances of each enzyme in the solvents became much more similar after correction, differences still remained. Analysis of the enzyme suspensions revealed massive particles, which explains the low activity of enzymes in organic solvents. However, no correlation was found between estimates of the amount of catalytically available enzyme (present at the surface of suspended particles or immobilized on beads) and the maximal rates observed. Moreover, the solvents had similar effects on the intrinsic parameters of suspended and immobilized enzyme. The possible causes for the effects of the solvents on the catalytic performance of the enzymes, remaining after correction for solvent-substrate interactions and the amount of participating enzyme, are discussed with respect to the premises on which the correction method is based. (c) 1995 John Wiley & Sons, Inc.

Effects of fatty acid derivatives on the ignition quality and cold flow of diesel fuel

Abstract: The biodiesel that is considered as a possible substitute or extender of conventional automotive diesel fuel is commonly composed of fatty acid methyl esters that are prepared from the glycerides in vegetable oils by transesterification with methanol. This form of biodiesel is compatible with diesel fuel but offers no improvement in its ignition quality. This work describes the results of a series of experiments aimed at assessing other common fatty acid derivatives that could provide the desired biofuel component and, at the same time, improve the performance of the fuel. It was found that tertiary fatty amines and amides are significantly more effective than methyl esters in enhancing the ignition quality of the finished diesel fuel without having any negative effect on its cold flow properties.

Transesterification processes for vegetable oils: A simple control method of methyl ester content

Abstract: One of the main problems in the study or industrial application of transesterification processes for vegetable oils is how to measure the methyl ester content. In this work, a quick analytical method was developed for assessing the methyl ester content of purified “fuel grade” transesterification products by applying a simple correlation with viscosity. The correlation was tested on a wide range of samples with various methyl ester contents; the results were in agreement with the values measured by gas-chromatographic analysis. In a defined range of weight fractions the correlation allows for the determination of the methyl ester content of purified transesterification products by a single viscosity measurement. This method is especially suitable for process control purposes as it determines the methyl ester content quickly and simply.

Lipase biocatalysis in the production of esters

Abstract: Lipase biocatalysis was investigated as a tool for the production of butyl oleate and rapeseed oil 2-ethyl-1-hexyl ester by esterification and transesterification, respectively. We screened 25 commercially available lipases and found that butyl oleate was produced at high yields from oleic acid and 1-butanol by lipases fromCandida rugosa, Chromobacterium viscosum, Rhizomucor miehei, and Pseudomonas fluorescens. The initial water content of the system, lipase quantity, and the molar ratio of 1-butanol to oleic acid were important factors in influencing the ester yield. In general, no ester was formed without the addition of water. The exception wasCh. viscosum lipase, which yielded 98% of ester in 12 h with 1-butanol excess without additional water. The addition of 3.2% water increased the initial rate of reaction. With an oleic acid excess and only 0.3% lipase,C. rugosa andR. miehei lipases yielded 94 and 100% esters with initial water contents of 3.2 and 14%, respectively. Lipase-catalyzed alcoholysis of low-erucic acid rapeseed oil and 2-ethyl-1-hexanol without additional organic solvent also was studied in stirred batch reactors. In this case,C. rugosa lipase was the best biocatalyst with an optimal 2-ethyl-1-hexanol to rapeseed oil molar ratio of 2.8, a minimum of 1.0% added water, and 37°C. An increase in temperature up to 55°C increased the rate of reaction but did not affect the final ester yield. The enzyme was inactivated at 60°C. Under optimal conditions, the ester yield increased from 88% in 7 h to nearly complete conversion in 1 h when the lipase content was increased from 0.3 to 14.6%. In a 2-kg small pilot scale, up to 90% conversion (97% of theoretical) was obtained in 8 h at 37°C with 3.4% lipase in the presence of Amberlite XAD-7 resin with 3% added water.

Two-step process for the preparation of a (co)polycarbonate by transesterification

Abstract: A process for the preparation of a (co)polycarbonate having an excellent hue, heat resistance, residence to hydrolysis and impact resistance by transesterification with the use of an aparatuses of a low price. In the first step, a dihydroxy compound is reacted with a carbonic diester in a reactor having a surface area contacting the dihydroxy compound and the carbonic diester, a made of a material containing iron in an amount of 20% by weight or less, to give a prepolymer and, in the second step, melt-polycondensing the prepolymer in a reactor other than the reactor used in the first step.

Resolution of racemic flurbiprofen by lipase-mediated esterification in organic solvent

Abstract: Resolution of rac-flurbiprofen, 2-fluoro-α-methyl-[1,1′-biphenyl]-4-acetic acid (1), by biocatalytic methodologies has been studied. Enzymatic hydrolysis of rac-flurbiprofen methyl ester (2) in aqueous-organic medium gave poor results. Transesterification of the same ester mediated by immobilized lipase from Candida antarctica (Novozym® 435) in organic solvent proceeded with good enantiomeric excess but the isolation of the product required chromatographic separation and therefore was unsuitable for large scale preparation. Direct esterification of 1 with methanol in acetonitrile promoted by Novozym® 435 proved to be the best method since it gave, via a twofold kinetic resolution, S-flurbiprofen with excellent enantiomeric excess. The R-flurbiprofen methyl ester formed in the reaction can be converted into the starting rac-flurbiprofen by alkaline hydrolysis or, alternatively, into R-flurbiprofen by hydrolysis with acid.

A process for preparing copolyesters

Abstract: The present invention relates to a process for preparing copolyesters which involves two steps. The first step is a diol interchange step, and the second step is a polycondensation step. More specifically, the process involves (I) reacting in the presence of a polycondensation catalyst a dihydroxy terephthalate-containing compound having formula (1) wherein n is 1 to 10 and at least 99 % of the end groups are ethylene glycol moieties; and 0.01 to 10 moles, based on moles of the dihydroxy terephthalate-containing compound, of a diol, and (II) polycondensing the reaction product of Step (I) to form a copolyester while excess diol is removed until desired molecular weight is obtained. This process does not include a transesterification of a dialkyl ester reaction or an esterification reaction which are usually used to produce copolyesters. Moreover, this process allows for polyethylene terephthalate and copolyesters prepared therefrom to be produced on an integrated production line.

Candida antarctica lipase B catalysed kinetic resolutions: Substrate structure requirements for the preparation of enantiomerically enriched secondary alcanols

Abstract: The lipase B of the Candida antarctica yeast displays high enantioselectivity in transesterification reactions with chiral secondary alcohols in non-aqueous media. This was exploited to resolve a series of racemates structurally related to 2-octanol, namely 3-hydroxy-1-undecyne, 3-hydroxy-1-nonene, 3-nonanol, 1-chloro-2-octanol, 2-methyl-3-nonanol, 2,2-dimethyl-3-nonanol. The substrates were designed to probe the alcohol binding part of the active site of the lipase. The first four racemates could be resolved to produce compounds of high enantiomeric purity. A lipase catalysed transesterification of 1-chloro-2-octanol was observed. 2-Methyl-3-nonanol and 2,2-dimethyl-3-nonanol did not form any detectable amounts of product ester. The kinetic resolutions of the alcohols were performed with S-ethyl thiooctanoate as the acyl donor.

Process including depolymerization in polyester reactor for recycling polyester materials

Abstract: Previously used poly(ethylene terephthalate) polyester materials and copolymers thereof, and in particular postconsumer polyester materials, are depolymerized and repolymerized to produce bottle grade polymer containing up to 75% of the previously used material. The process involves the solubilization and depolymerization of the previously used polyester material in a transesterification and/or polymerization mixture containing dimethylterephthalate, ethylene glycol and transesterification products thereof.

Transesterification of soy lecithin by lipase and phospholipase

Abstract: Soy lecithin was modified by enzymatic transesterification in a solvent-free system. 1,3-SpecificRhizomucor miehei lipase was found to be efficient in the transesterification with lauric acid and oleic acid, where oleic acid was more incorporated into soy lecithin. Phospholipase A2 incorporated lauric acid hardly at all, but it hydrolyzed lecithin efficiently. The mixture of lipase and phospholipase A2 (1:1, w/w) incorporated lauric acid to the same extent as did 1,3-specific lipase alone at the same total enzyme concentration. The main fatty acids replaced were palmitic and linoleic acids by 1,3-specific lipase and its mixture with phospholipase A2, and linoleic and linolenic acids by phospholipase A2 alone, suggesting an improved oxidative stability of the resulting product. Hydrolysis could not be prevented, but it could be regulated by incubation time and by enzyme dosage. The minimal water content for significant incorporation of lauric acid into lecithin was below 0.5% of the weight of the reaction mixture.

Enzymatic synthesis of polyglycerol-fatty acid esters in a solvent-free system

Abstract: The enzymatic transesterification of fatty acid methyl esters from vegetable oil and polyglycerol has been successfully performed in the presence of Lipozyme without any solvent. The optimal conditions to obtain a mixture with lipophilic tensioactive properties were found to be a molar ratio of fatty acid methyl esters and polyglycerol of 1.33:1 at 60°C. Evaporation of the methanol produced in this reaction increased the yield of the reaction. Moreover, for this reaction, adsorption of the polyol on silica gel prior to the transesterification allowed the completion of the reaction and improved the kinetic properties. Hydrophile-lipophile balance and surface activity of the polyglycerol esters were measured to determine the emulsifying properties of these molecules.

New Polymer Syntheses. 78. Star-Shaped and Hyperbranched Polyesters by Polycondensation of Trimethylsilyl 3,5-Diacetoxybenzoate

Abstract: 3,5-Diacetoxybenzoic acid and its trimethylsilyl ester were polycondensed in bulk at various temperatures to optimize the reaction conditions. Whereas polycondensations of the free acid above 250 °C resulted in partial cross-linking, the silylated monomer yielded perfectly soluble hyperbranched polyesters even at 280 °C. Addition of Ti(OPr) 4 as a transesterification catalyst gave lower molecular weights. 1 H NMR spectroscopy indicates a degree of branching around 0.5 regardless of the reaction conditions. GPC measurements revealed M w /M n ratios > 5 and weight-average molecular weights (M w ) up to 700 x 10 3 . Copolycondensations with acetylated Bisphenol-P yielded star-shaped hyperbranched polyesters. Their molecular weight can be varied by the feed ratios of monomer and comonomer. 1 H NMR spectroscopy allowed the determination of their average degrees of polymerization. Further star-shaped polyesters with dendritic star arms were prepared by polycondensations of silylated 3,5-diacetoxybenzoic acid with acetylated tetraphenols.

Production of polycarbonate

Abstract: PURPOSE: To efficiently obtain a polycarbonate excellent in hue and heat and hydrolytic resistances by adding an acidic compound to a part before a prescribed vent port in a vented type extruder, kneading the resultant mixture, then introducing water thereinto and continuously removing volatile matter from the polycarbonate. CONSTITUTION: To (A) a polycarbonate obtained by carrying out the polycondensation of a carbonic diester with a dihydroxyaryl compound in the presence of a transesterification catalyst [e.g. an alkali(alkaline earth) metal compound, a basic boron compound, a basic phosphorus compound, a basic ammonium compound or an amine compound], (B) an acidic compound [e.g. an inorganic acid, a carboxylic acid (ester), sulfonic acid (ester) or sulfinic acid (ester)] is added in the part before a vent port nearest to a resin feed port in a vented type extruder, they are kneaded and to the resultant mixture water is introduced and volatile matter is continuously removed. Thereby, the objective polycarbonate is obtained. The amount of introduced water is 0.1-10wt.% based on the amount of the extruded resin based on one stage. COPYRIGHT: (C)1996,JPO

Comparison of direct esterification and transesterification of fructose by Candida antartica lipase

Abstract: Fructose oleates synthesis was performed in a batch reactor by trans- or direct esterification An immobilized lipase from Candida antartica was used When a solvent was used, 65% and 46% of conversion of fructose were obtained by transesterification and direct esterification, respectively These two reactions were also compared in a solvent-free melt Both in molten media and with cosolvent, two isomeric forms of fructose oleates were produced

Low-calorie triglyceride synthesis by lipase-catalyzed esterification of monoglycerides

Abstract: Monoglycerides of erucic acid (C22:1, Δ13), prepared by conventional methods, were reacted with caprylic acid (octanoic acid, C8.0) by using lipases as catalysts with the intention of synthesizing a triglyceride that contains two molecules of caprylic acid and one molecule of erucic acid (caprucin). The reaction was carried out by mixing lipase powder, a small quantity of water, and the reactants in a temperature-controlled stirred batch reactor. Organic solvents or emulsifying agents were not required. When the nonspecific lipase fromPseudomonas cepacia was used, a yield of approximately 37% caprucin was obtained, together with a complex mixture of di- and triglycerides that resulted from the random transesterification of the erucic acid. The fatty acid-specific lipase fromGeotrichum candidum promoted minimal transesterification of erucic acid and resulted in a yield of 75% caprucin and approximately 10% interesterification products. Lipase fromCandida rugosa exhibited a similar, although less pronounced, specificity to that fromG. candidum and promoted more transesterification of erucic acid. Optimum conditions forG. candidum lipase were at 50°C and an initial water content of 5.5%. After the reaction, erucic acid was converted to behenic acid by hydrogenation, thereby converting caprucin into caprenin, a commercially available low-calorie triglyceride.

A study on blends of liquid crystalline copolyesters with polycarbonate. I. Compatibility by transesterification

Abstract: Blends of poly(bisphenol-A carbonate) (PC) and synthesized liquid crystalline poly(oxybenzoate-co-ethylene terephthalate 40/60) (P46) were prepared through meltmixing in a Brabender mixer. The miscibility of the blends at different compositions and blending time was investigated with differential scanning calorimetry. The corresponding morphology of the blends was analyzed with scanning electron microscopy. It was found that for blends containing more than 20% P46 and mixed at 250°C or above the transesterification between PC and P46 took place. This transesterification was confirmed at a blend containing 40% P46 by nuclear magnetic resonance spectroscopy. The transesterification happened first between PC and the ester in the poly(ethylene terephthalate) (PET) block and then between PC and the ester in the polyoxybenzoate (POB) block. At 260°C and after 60 min' blending, the blend containing 30% P46 became an almost compatible system for appearing of a single glass transition temperature. This is also verified by the disappearing of P46 droplets in the PC matrix in the micrographs' observation. After 60 min' of blending, the compatibility of the system can be greatly improved even for the blend containing 40% P46 mixed at 260°C by the micrograph's observation. © 1995 John Wiley & Sons, Inc.

Transesterification Catalyzed by Lanthanoid Tri-2-propoxides

Abstract: The transesterification of esters with alcohols was efficiently catalyzed by Ln(OPri)3. The catalytic activity of Ln(OPri)3 decreased in the following order; La > Nd > Gd > Yb, and was much higher than those of Al(OPri)3 and Ti(OPri)4.

Process for preparing a synthetic ester from a vegetable oil

Abstract: The object of the invention is a process for preparing a synthetic ester from a vegetable oil by a two-stage transesterification process. Further objects of the invention are lubricants containing a synthetic ester prepared by the process according to the invention.

Fatty acid vinyl esters as acylating agents: a new method for the enzymatic synthesis of monoacylglycerols

Abstract: Lipase-catalyzed synthesis of monoacylglycerols (MAG) was performed by transesterification reactions between fatty acid vinyl esters and either glycerol (1) or 1,2-O-isopropylidene-rac-glycerol (2), without solvents or in the presence ofn-pentane. Vinyl decanoate, vinyl laurate, vinyl stearate and vinyl palmitate have been converted to the corresponding monoacylglycerols. As expected for the reaction with1, a mixture of mono-, di- and triacylglycerols was synthesized. The highest concentrations of MAG were achieved with vinyl stearate (30% 2-MAG and 15% 1-MAG). The reactions of fatty acid vinyl esters with the protected glycerol (2) led to the corresponding protected 3-monoacylglycerols with 100% conversion after short reaction times. The subsequent cleavage of these acetonides was performed by four different methods. The fastest cleavage was found with trifluoroacetic acid as catalyst, whereas the highest concentration of MAG (100%) was obtained for the boric acid-catalyzed hydrolysis of the acetonides.