Showing papers on "Transesterification published in 1999"
TL;DR: In this article, the transesterification reaction is aected by molar ratio of glycerides to alcohol, catalysts, reaction temperature, reaction time and free fatty acids and water content of oils or fats.
4,902 citations
TL;DR: In this paper, the molar ratio of alcohol, reaction temperature, reaction time, water content, and free fatty acids were investigated to determine the best strategy for producing biodiesel.
Abstract: Vegetable oils and animal fats can be transesterified to biodiesel for use as an alternative diesel fuel.
Conversion of low cost feedstocks such as used frying oils is complicated if the oils contain large amounts of free fatty
acids that will form soaps with alkaline catalysts. The soaps can prevent separation of the biodiesel from the glycerin
fraction. Alternative processes are available that use an acid catalyst. The objective of this study was to investigate the
effect of process variables on acid-catalyzed transesterification. The molar ratio of alcohol, reaction temperature, catalyst
amount, reaction time, water content, and free fatty acids were investigated to determine the best strategy for producing
biodiesel. Food grade soybean oil was used to prepare esters using excess methanol and sulfuric acid as a catalyst. To
compare the effect of different alcohol types on ester formation, methanol, ethanol, 2-propanol, and n-butanol were
compared. The American Oil Chemists’ Society Method Ca 14-56 was used to measure the biodiesel’s total glycerin
amount as an indicator of the completeness of the reaction. It was found that acid catalysis can provide high conversion
rates but much longer times are required than for alkaline catalysts. The acid catalyst also requires the concentration of
water to be less than 0.5%, which is about the same as is required for alkaline catalysts. Water formed by the
esterification of free fatty acids limited their presence in the oil to 5%.
774 citations
TL;DR: In this paper, the transesterification of rapeseed oil by methyl alcohol can be catalysed effectively by basic alkaline-earth metal compounds: calcium oxide, calcium methoxide and barium hydroxide.
528 citations
TL;DR: In this article, the degradation of enzymatic activity was attributed to the formation of an hydrophilic hindrance around the enzyme resulting in diffusion limitations of the hydrophobic substrate from the organic phase to the enzyme.
233 citations
TL;DR: In this article, a study was made of the reaction of transesterification of Cynara cardunculus L. oil by means of methanol, using sodium hydroxide, potassium hydroxides, and sodium methoxide as catalysts.
Abstract: A study was made of the reaction of transesterification of Cynara cardunculus L. oil by means of methanol, using sodium hydroxide, potassium hydroxide, and sodium methoxide as catalysts. The objective of the work was to characterize the methyl esters for use as biodiesels in internal combustion motors. The operation variables used were methanol concentration (5−21 wt %), catalyst concentration (0.1−1 wt %), and temperature (25−60 °C). The evolution of the process was followed by gas chromatography, determining the concentration of the methyl esters at different reaction times. The biodiesel was characterized by determining its density, viscosity, high heating value, cetane index, cloud and pour points, Ramsbottom carbon residue, characteristics of distillation, and flash and combustion points according to ISO norms. The biodiesel with the best properties was obtained using 15% methanol, sodium methoxide as catalyst (1%), and 60 °C temperature. This biodiesel has very similar properties to those of diesel ...
157 citations
TL;DR: In this article, the transesterification reaction which yields the methyl esters can be monitored for completion by near-infrared (NIR) spectroscopy using a fiber-optic probe.
Abstract: Vegetable oil esters, particularly methyl esters, are being explored and used as alternative diesel fuel (biodiesel). The transesterification reaction which yields the methyl esters can be monitored for completion by near-infrared (NIR) spectroscopy using a fiber-optic probe. Although the NIR method is less sensitive than gas chromatography (GC) for quantifying minor components, by correlation with existing GC or other analytical data, biodiesel fuel quality can be assessed through the NIR method. The NIR method is easier and faster to use than GC.
150 citations
TL;DR: This study shows that the use of two-solvent mixtures may become a feasible alternative for the synthesis of sucrose esters, allowing to exploit the catalytic potential of lipases.
Abstract: The enzymatic synthesis of 6-O-lauroylsucrose and 6-O-palmitoylsucrose was performed by transesterification of sucrose with the corresponding vinyl esters in a medium constituted by two solvents. More specifically, the acylation was carried out in 2-methyl-2-butanol (tert-amyl alcohol) containing a low percentage (not higher than 20%) of dimethyl sulfoxide. Several lipases were able to catalyze the transesterification, but that from Humicola lanuginosa (adsorbed on diatomaceous earth) was particularly useful. We optimized the synthesis of 6-O-lauroylsucrose varying the percentage and nature of the cosolvent, the molar ratio sucrose/vinyl laurate, the nature of bulk solvent and the enzyme content. Under the best conditions (2-methyl-2-butanol/DMSO 4:1 v/v), a sucrose conversion of 70% to 6-O-lauroylsucrose was achieved in 24 h using 50 mg biocatalyst/mL. As a side process, a low percentage (<5% in 24 h) of the initial sucrose is converted into the diesters 6,1'-di-O-lauroylsucrose and 6,6'-di-O-lauroylsucrose. The above methodology was also extended to the synthesis of 6-O-palmitoylsucrose. The acylation process was even faster, giving rise to an 80% conversion to monoester in 48 h using 25 mg biocatalyst/mL. This study shows that the use of two-solvent mixtures may become a feasible alternative for the synthesis of sucrose esters, allowing to exploit the catalytic potential of lipases.
145 citations
TL;DR: In this article, a method to predict the surface tension of biodiesel fuels based on the fatty acid composition is presented. But the results show that the differences in surface tension between biodiesel types are not the main cause of the reported differences in engine tests.
Abstract: The emergence of biodiesel fuels as diesel fuel substitutes has led to several studies on their properties. Surface tension, which plays a role in atomization, has lacked attention compared to other properties. This paper presents a method to predict the surface tension of biodiesel fuels based on the fatty acid composition. Several binary, ternary, and quaternary mixtures of fatty acid ethyl ester gas chromatographic (GC) standards were prepared, and we found that a mass-average equation predicted the surface tension of these mixtures within ±3.5% of their measured values. Six complex mixtures of fatty acid methyl ester GC standards that simulated typical oils used as biodiesel fuels were also prepared. For these complex mixtures the predicted surface tensions of the mixtures, calculated from a mass-average equation, were 2–6% higher than the measured values. A mass-average equation was developed in which we used a weighted surface tension for the individual components, and we found that this method predicted the surface tension of the simulated oils within ±4.5% of their measured values. Five natural vegetable oils were used to produce biodiesel fuels by the transesterification process. The predicted surface tensions of these fuels were all within ±3.5% of their measured values. The surface tensions of 15 biodiesel types were then predicted, based on their fatty acid composition as published in the literature. These results show that the differences in surface tension between biodiesel types are not the main cause of the reported differences in engine tests.
124 citations
TL;DR: In this article, the chemical changes that occur during heating of rapeseed oil, especially the formation of polymers, were investigated, and the amount of polymeric fatty acid methyl esters had a negative influence on fuel characteristics.
Abstract: Fatty acid methyl esters are well established as an alternative fuel called “biodiesel.” For economic reasons, used frying oil is an interesting alternative feedstock for biodiesel production. The chemical changes that occur during heating of rapeseed oil, especially the formation of polymers, were investigated. Heated rapeseed oil samples were transesterified with methanol and analyzed by size-exclusion chromatography. During heating, the amount of polymers in the starting oil increased up to 15 wt%, but only up to 5 wt% in the transesterified samples. So during transesterification, dimeric and trimeric triglycerides in the starting oil were mainly converted into monomeric and dimeric fatty acid methyl esters. The amount of polymeric fatty acid methyl esters had a negative influence on fuel characteristics. After 6 h of heating, the amount of Conradson carbon residue and after 16 h the viscosity exceeded that of the existing specifications for biodiesel. Therefore, the amount of polymers in waste oil is a good indicator for the suitability for biodiesel production.
121 citations
TL;DR: In this article, a regression equation obtained by a modified central composite design of RSM predicted optimal reaction conditions of 38.4°C, 2.47 h, 13.7 wt% lipase (PS-30), and a mole ratio of grease to ethanol of 1:6.6.
Abstract: Previous research suggested that ethyl esters derived from recycled restaurant grease might be a potential source of biodiesel. Accordingly, response surface methodology (RSM) was employed to optimize reaction parameters—temperature, time, level of lipase, mole ratio of reactants—in the PS-30 lipase-catalyzed transesterification reaction of grease to ethyl esters using 95% ethanol. The regression equation obtained by a modified central composite design of RSM predicted optimal reaction conditions of 38.4°C, 2.47 h, 13.7 wt% lipase (PS-30), and a mole ratio of grease to ethanol of 1:6.6. Under these conditions the predicted optimal percentage ethyl ester yield was 85.4%. Subsequent experiments using the predicted parameter combinations indicated a trend where experimental percentage yields of ethyl ester were consistently lower than predicted values. In an effort to improve the experimental yield of esters, a second portion of PS-30 lipase was added without success; however, the addition of 5% SP435 one hour after the start of the initial reaction increased the yield of esters to >96%. Neither lipase PS-30 nor lipase SP435 alone, however, gave the RSM-predicted yield of ethyl esters.
112 citations
TL;DR: In this article, a series of Al, Ti, Zn and Zr compounds were evaluated as intramolecular transesterification catalysts for the thermal depolymerization reaction of poly(L-lactic acid) oligomer resulting in LL-lactide.
Abstract: A series of Al, Ti, Zn and Zr compounds, ie., their metal alkoxides, organic acid and enolate salts, halid and oxide, were evaluated as intramolecular transesterification catalysts for the thermal depolymerization reaction of poly(L-lactic acid) oligomer resulting in LL-lactide, meso-lactide and DD-lactide by gas chromatography using a β-cyclodexstrin chiral stationary phase capillary column. The activity of the intramolecular transesterification compared with that of stannous 2-ethylhexanoate was in the following order: Sn>Zn>Zr>Ti>Al.
TL;DR: In this article, a macrocyclic additive, methylβ-cyclodextrin (MβCD), was introduced to simultaneously enhance the activity and enantioselectivity of dehydrated subtilisin Carlsberg suspended in neat organic solvents.
Abstract: The use of enzymes in organic solvents to introduce chirality to a number of relevant organic compounds has been well documented. However, there are still major drawbacks in such applications, in particular the frequently much lower enzyme activity under nonaqueous conditions. In addition, the reaction outcome (substrate enantioselectivity and reaction rates) cannot be accurately predicted. To overcome these limitations, herein we introduce methyl-β-cyclodextrin (MβCD) as a new macrocyclic additive to simultaneously enhance the activity and enantioselectivity of dehydrated subtilisin Carlsberg suspended in neat organic solvents. MβCD was efficient in dramatically increasing the activity and significantly improving the enantioselectivity of subtilisin in co-lyophilizates when compared to the powder lyophilized from buffer alone. The initial rate determined for the transesterification between sec-phenethyl alcohol and vinyl butyrate increased by up to 164-fold and the enantioselectivity could be doubled. In...
Patent•
15 Apr 1999TL;DR: In this paper, an organic titanium compound, a complexing agent, a phosphorus source, a solvent, and optionally a cocatalyst, a process for preparing the composition and use thereof in esterification, transesterification, polymerisation or combinations thereof.
Abstract: This invention relates to a catalyst composition comprising an organic titanium compound, a complexing agent, a phosphorus source,, a solvent, and optionally a cocatalyst, a process for preparing the composition and use thereof in esterification, transesterification, polymerisation or combinations thereof. The complexing agent is selected from hydroxycarboxylic acids and aminocarboxylic acids, or combinations thereof, the phosphorus is selected from phosphonic acid, phosphinic acid, a phospine or combinations thereof. The cocatalyst can be a cobalt/aluminium catalyst, and antimony compound, or combinations thereof; a sulfonic acid may be present. In examples a composition of tetraisopropyl titanate, ethylene glycol, phenylphosphinic acid, p-toluenesulfonic acid and malic acid was used as polycondensation catalyst in the preparation of PET.
TL;DR: In this paper, non-activated β-D(+)-glucose and fatty acids or fatty acid methyl esters (C 8, C 16, C 18 ) with lipase from Candida antarctica B immobilized on polypropylene EP 100.
TL;DR: In this paper, the alkylguanidines were anchored to modified polystyrene or siliceous MCM-41, encapsulated in the supercages of zeolite Y, or entrapped in SiO 2 sol-gel matrices.
Abstract: Transesterification of soybean oil with methanol has been carried out in the presence of heterogenized alkylguanidines as catalysts. The alkylguanidines were anchored to modified polystyrene or siliceous MCM-41, encapsulated in the supercages of zeolite Y, or entrapped in SiO 2 sol-gel matrices. The catalytic activity of these catalysts was compared with that of their homogeneous counterparts, showing that the yields of methyl esters obtained in the homogeneous phase can be obtained with the guanidines anchored to the supports after longer reaction times. The catalysts prepared by immobilization of alkylguanidines in microporous systems showed diffusion restrictions for the vegetable oil as well as the low stability of the inorganic framework.
TL;DR: The results suggest that the Pseudomonas lipase caused a greater randomization and diversification of fatty acids, particularly palmitic acids, in palm stearin with the unsaturated fatty acids from sunflower oil than did R. miehei lipase.
TL;DR: In this article, two samples of a single composition blend of PET and PEN were prepared by solution blending using different solvents such that the hydroxyl end groups in one blend were modified.
TL;DR: It is suggested that MPEG positively influences the porosity of the lipase aggregates in organic media, whereas OPEG and OCT induce tighter aggregates.
TL;DR: In this paper, a nonphosgene process for producing bisphenol-A polycarbonate (PC) was developed through a transesterification between BPA and dimethyl carbonate (DMC) and a melt-polycondensation of the resulting bismethylcarbonate.
Abstract: A novel nonphosgene process for producing bisphenol-A polycarbonate (PC) was developed through a transesterification between bisphenol-A (BPA) and dimethyl carbonate (DMC) and a melt-polycondensation of the resulting bisphenol-A bismethylcarbonate (1). The transesterification was carried out by heating bisphenol A in dimethylcarbonate in the presence of Lewis acid catalysts, removing the by-producing methanol using molecular shieves 4A. Among various catalysts, a combination of (Bu2SnCl)2O and dimethylaminopyridine gave the best results to produce 1 in 22% yield for 48 h. Using a larger amount of the molecular sieves further improved the yield to 80% in 120 h. The resulting 1 was heated under reduced pressure in the presence of titanium catalysts to produce PC in good yields. The resulting PC had high weight average molecular weight (Mw) of 75,000. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2087–2093, 1999
TL;DR: A hybrid subtilisin the solubility of which can be regulated by photoirradiation through coupling with a photoresponsive copolymer that carries spiropyran groups in its side chains is synthesized.
Abstract: We have synthesized a hybrid subtilisin the solubility of which can be regulated by photoirradiation through coupling with a photoresponsive copolymer that carries spiropyran groups in its side chains The copolymer was synthesized by polymerization of methacrylate, methacrylic acid, and spiropyran–carrying methacrylate It was then covalently bonded to the amino groups of subtilisin Carlsberg via its carboxyl groups using a carbodiimide coupling agent The hybrid subtilisin was perfectly soluble in toluene and efficiently catalyzed transesterification After ultraviolet irradiation, the hybrid subtilisin precipitated and was easily and quantitatively recovered by centrifugation Recovered hybrid subtilisin, resolubilized by visible light irradiation, retained its original transesterification activity even after several cycles of precipitation and solubilization
TL;DR: In this article, the authors determined the optimum conditions for the esterification reactions of lactic and glycolic acids with fatty alcohols in the presence of a lipase from Candida antarctica.
TL;DR: In this paper, the two-step synthesis of diphenyl carbonate (DPC) from dimethyl carbonate and phenol has been compared in liquid phase and gas phase, both over heterogeneous catalysts.
Abstract: The two-step synthesis of diphenyl carbonate (DPC) from dimethyl carbonate (DMC) and phenol has been compared in liquid phase and gas phase, both over heterogeneous catalysts In the first step, equilibrium yields of methyl phenyl carbonate (MPC) in the transesterification of DMC and phenol were very low at low temperatures in the liquid phase although reaction rates were fast This endothermic reaction was more favorable at high temperatures in the gas-phase reaction Titanium oxide catalysts supported on SiO2 or activated carbon were found to be effective in a continuous gas flow reactor In case of the second step, the disproportionation of MPC, selective formation of DPC was not feasible in the gas-phase reaction due to extensive side reactions However, there was no by-product in the liquid-phase reaction over the TiO2/SiO2 catalyst Therefore, our proposed two-step synthesis process consists of the gas-phase transesterification of DMC and phenol followed by the liquid-phase disproportionation of MPC to DPC, both over the TiO2/SiO2 catalyst
TL;DR: In this article, statistical experimental design combined with principal component analysis was used to evaluate interdependence of process variables in enzymatic transesterification of rapeseed oil methyl ester (biodiesel) and trimethylolpropane.
TL;DR: N-Protected peptides undergo clean transesterification without significant racemization, making this methodology potentially very useful.
Abstract: Extremely strong nonionic superbases of the type P(RNCH2CH2)3N catalyze the transesterification of carboxylic acid esters with high selectivity and yields at 25 °C. These bases also catalyze the deacetylation of alcohols under mild conditions in quantitative yields. Using enol acetates as acylating agents, primary and secondary alcohols are efficiently protected as acetates through the action of these catalysts. Substituents such as epoxide, carbamate, acetal, oxazoline, nitro, and alkynyl functionalities are tolerated under the reaction conditions. N-Protected peptides undergo clean transesterification without significant racemization, making this methodology potentially very useful.
TL;DR: Results suggest that enzyme dispersion and/or proper enzyme conformation (favored by interaction with PEG or the hydrophobic Sol-Gel-AK matrix) are essential for the expression of high lipase activity in organic media.
Abstract: The activity of different lipase (from Pseudomonas cepacia) forms, such as crude powder (crude PC), purified and lyophilized with PEG (PEG + PC), covalently linked to PEG (PEG-PC), cross-linked enzyme crystals (CLEC-PC), and immobilized in Sol-Gel-AK (Sol-Gel-AK-PC) was determined, at various water activities (aw), in carbon tetrachloride, benzene and 1,4-dioxane. The reaction of vinyl butyrate with 1-octanol was employed as a model and both transesterification (formation of 1-octyl butyrate) and hydrolysis (formation of butyric acid from vinyl butyrate) rates were determined. Both rates depended on the lipase form, solvent employed, and aw value. Hydrolysis rates always increased as a function of aw, while the optimum of aw for transesterification depended on the enzyme form and nature of the solvent. At proper aw, some lipase forms such as PEG + PC, PEG-PC, and Sol-Gel-AK-PC had a total activity in organic solvents (transesterification plus hydrolysis) which was close to (39 and 48%) or even higher than (130%) that displayed by the same amount of lipase protein in the hydrolysis of tributyrin—one of the substrates most commonly used as standard for the assay of lipase activity—in aqueous buffer. Instead, CLEC-PC and crude PC were much less active in organic solvents (2 and 12%) than in buffer. The results suggest that enzyme dispersion and/or proper enzyme conformation (favored by interaction with PEG or the hydrophobic Sol-Gel-AK matrix) are essential for the expression of high lipase activity in organic media. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 62: 554–561, 1999.
TL;DR: In this article, a kinetic model for the transesterification of a cotton seed oil with ethanol in the presence of water is proposed, and the effect of water content in the reacting mixture on the transterification reaction is studied.
Abstract: A kinetic model for the transesterification of a cotton seed oil with ethanol in the presence of water is proposed. The effect of water content in the reacting mixture on the transesterification reaction is studied. The dependence of the equilibrium constants and reaction rate constants on the water content is presented. Equilibrium was reached within less than 30 min reaction time in all cases. The increase of the water content results in decrease of the conversion level of the oil. By increasing the ethanol/oil ratio the conversion of triglyceride increases and the concentration of mono- and diglyceride in the product mixtures are reduced.
Patent•
02 Dec 1999TL;DR: In this article, a catalyst composition for polyester polyester is described, in which a titanium compound, a complexing agent, hypophosphorous acid or its metal salt, water and optionally a solvent are used.
Abstract: A catalyst composition is disclosed. The composition comprises a titanium compound, a complexing agent, hypophosphorous acid or its metal salt, water and optionally a solvent. The complexing agent can be hydroxycarboxylic acid, alkanolamines, aminocarboxylic acids, or combinations of two or more thereof. The solvent can be water, ethanol, propanol, isopropanol, butanol, ethylene glycol, propylene glycol, isopropylene glycol, butylene glycol, 1-methyl propylene glycol, pentylene glycol, or combinations of two or more thereof. The titanium compound can be combined with a zirconium compound. Also disclosed is a process for using the composition for producing an ester or a polyester. The process comprises contacting a carbonyl compound, in the presence of the composition, with an alcohol under a condition suitable for esterification, transesterification, polymerization, or combinations of two or more thereof.
TL;DR: In this article, the transesterification of methyl benzoate and dimethyl terephthalate with ethylene glycol to 2-hydroxyethyl benzoates and 2 -hydroxy methyl terephate, respectively, was investigated in the presence of various basic zeolites having different basic strengths in the liquid phase at 150°C and 180°C under continuous removal of deliberated methanol.
Abstract: The transesterification of methyl benzoate and dimethyl terephthalate with ethylene glycol to 2-hydroxyethyl benzoate and 2-hydroxyethyl terephthalate, respectively, was investigated in the presence of various basic zeolites having different basic strengths. The reactions were carried out in the liquid phase at 150°C and 180°C under continuous removal of deliberated methanol. The dependence of conversion and selectivity is discussed upon temperature, various reactant/catalyst ratios and the starting material ratio.
TL;DR: In this paper, the gas-phase hydrogenolysis of dimethyl maleate has been studied over copper/zinc oxide catalysts at temperatures between 473 and 513 K in the pressure range from 2 to 35 bar.
Abstract: The gas-phase hydrogenolysis of dimethyl maleate has been studied over copper/zinc oxide catalysts at temperatures between 473 and 513 K in the pressure range from 2 to 35 bar. A Cu/ZnO catalyst with a low copper content of 15 mol % was found to be the most active for the conversion of dimethyl maleate. At very low residence times, significant amounts of dimethyl maleate isomerize to dimethyl fumarate. The reaction then proceeds via the saturated ester, dimethyl succinate, until 1,4-butanediol and γ-butyrolactone are formed together with methanol. Furthermore, the chosen catalyst produces low amounts of tetrahydrofuran and water and only traces of undesirable butanol and CO2. It was found that the production of high amounts of 1,4-butanediol in one step is not possible, because the simultaneous presence of diesters and butanediol gives rise to the formation of a polymeric material via transesterification. Therefore, a two-step process including the complete conversion of dimethyl maleate to γ-butyrolacton...