Showing papers on "Transesterification published in 2001"

Biodiesel production from oils and fats with high free fatty acids

Abstract: Biodiesel is an alternative fuel for diesel engines consisting of the alkyl monoesters of fatty acids from vegetableoils or animal fats. Most of the biodiesel that is currently made uses soybean oil, methanol, and an alkaline catalyst. The highvalue of soybean oil as a food product makes production of a costeffective fuel very challenging. However, there are largeamounts of lowcost oils and fats such as restaurant waste and animal fats that could be converted to biodiesel. The problemwith processing these low cost oils and fats is that they often contain large amounts of free fatty acids (FFA) that cannot beconverted to biodiesel using an alkaline catalyst. In this study, a technique is described to reduce the free fatty acids contentof these feedstocks using an acidcatalyzed pretreatment to esterify the free fatty acids before transesterifying the triglycerideswith an alkaline catalyst to complete the reaction. Initial process development was performed with synthetic mixturescontaining 20% and 40% free fatty acids, prepared using palmitic acid. Process parameters such as the molar ratio of alcohol,type of alcohol, acid catalyst amount, reaction time, and free fatty acids level were investigated to determine the best strategyfor converting the free fatty acids to usable esters. The work showed that the acid level of the high free fatty acids feedstockscould be reduced to less than 1% with a 2step pretreatment reaction. The reaction mixture was allowed to settle betweensteps so that the watercontaining alcohol phase could be removed. The 2step pretreatment reaction was demonstrated withactual feedstocks, including yellow grease with 12% free fatty acids and brown grease with 33% free fatty acids. After reducingthe acid levels of these feedstocks to less than 1%, the transesterification reaction was completed with an alkaline catalystto produce fuelgrade biodiesel.

Production of biodiesel fuel from triglycerides and alcohol using immobilized lipase

Abstract: Transesterification reaction was performed using triglycerides and short-chain alcohol by immobilized lipase in non-aqueous conditions. The long-chain fatty acid ester, which is the product of this reaction, can be used as a diesel fuel that does not produce sulfur oxide and minimize the soot particulate. Immobilized Pseudomonas fluorescens lipase showed the highest activity in this reaction. Immobilization of lipase was carried out using porous kaolinite particle as a carrier. When methanol and ethanol were used as alcohol, organic solvent like 1,4-dioxane was required. The reaction could be performed in absence of solvent when 1-propanol and 1-butanol were used as short-chain alcohol. The activity of immobilized lipase was highly increased in comparison with free lipase because its activity sites became more effective. Immobilized enzyme could be repeatedly used without troublesome method of separation and the decrease in its activity was not largely observed.

New Paradigms for Organic Catalysts: The First Organocatalytic Living Polymerization

Abstract: A metal-free approach to the living ring-opening polymerization (ROP, shown schematically) of lactide has been developed using strongly basic amines such as 4-(dimethylamino)pyridine as transesterification catalysts. These organic catalysts must be used in combination with a nucleophile such as an alcohol, which is the actual initiating species.

Stabilization of alpha-chymotrypsin by ionic liquids in transesterification reactions.

Abstract: Five different ionic liquids, based on dialkylimidazolium and quaternary ammonium cations associated with perfluorinated and bis (trifluoromethyl) sulfonyl amide anions, were used as reaction media to synthesize N-acetyl-L-tyrosine propyl ester by transesterification with alpha-chymotrypsin at 2% (v/v) water content at 50 degrees C. The synthetic activity was reduced by the increase in alkyl chains length of cations and by increases in anion size, which was related to the decrease in polarity. Incubation of the enzyme (with and without substrate) in ionic liquids exhibited first-order deactivation kinetics at 50 degrees C, allowing determination of deactivation rate constants and half-life times (1-3 h). Ionic liquids showed a clear relative stabilization effect on the enzyme, which was improved by increased chain length of the alkyl substituents on the imidazolium ring cations and the anion size. This effect was 10-times enhanced by the presence of substrate. For example, 1-butyl-3-methylimidazolium hexafluorophosphate increased the alpha-chymotrypsin half-life by 200 times in the presence of substrate with respect to the 1-propanol medium. These results show that ionic liquids are excellent enzyme-stabilizing agents and reaction media for clean biocatalysis in non-conventional conditions.

Analytical methods used in the production and fuel quality assessment of biodiesel.

Abstract: Biodiesel, an alternative diesel fuel derived from vegetable oil, animal fats, or waste vegetable oils, is obtained by reacting the oil or fat with an alcohol (transesterification) in the presence of a basic catalyst to give the corresponding mono-alkyl esters. Two major categories of methods besides other miscellaneous ones have been reported in the literature for assessing biodiesel fuel quality and/or monitoring the transesterification reaction by which biodiesel is produced. The two major categories comprise chromatographic and spectroscopic methods. This article considers the various methods in each category, including advantages and drawbacks, and offers suggestions on selection of appropriate methods.

Transesterification of rapeseed oil in the presence of basic zeolites and related solid catalysts

Abstract: The transesterification of rapeseed oil with methanol was performed by reflux of methanol over cesium-exchanged NaX faujasites, mixed magnesium-aluminum oxides, magnesium oxide, and barium hydroxide for different methanol-to-oil ratios. Over cesium-exchanged NaX faujasites and mixed magnesium-aluminum oxides, a long reaction time and a high methanol-to-oil ratio are required to achieve both high oil conversion and high yields in methyl esters. However, over a 300 m2/g magnesium oxide, methanol-to-oil ratios and reaction times are significantly reduced to obtain both high oil conversion and high yield in the methyl esters, particularly when the hydroxide precursor is calcined at 823 K. Finally, preliminary results with other basic solids such as barium hydroxide have shown a very high activity and a very high yield in esters. This catalyst is particularly effective since, for a methanol-to-oil ratio of 6, at reflux of methanol and after a reaction time of only 1 h, the oil conversion is about 80% with a nearly quantitative ester molar fraction.

Calcium carbonate catalyzed alcoholysis of fats and oils

Abstract: Several alcoholysis catalysts, known to be effective for reactions between simple alcohols and soybean oil, were evaluated and found to be ineffective toward alcoholysis of ethylene glycol with soybean oil under traditional reaction conditions An initial survey of alternative catalysts revealed that organometallic tin complexes were effective but unsatisfactory due to toxicity and difficulty in recovering the catalyst Satisfactory performance for several alcoholysis reactions was achieved with calcium carbonate catalysts even though at higher temperatures, typically greater than 200°C Higher reaction temperatures are not considered to be a problem for flow reactors where heat exchangers can be readily used to minimize energy costs Free fatty acids were esterified by the calcium carbonate and did not appear to inhibit the catalyst Reaction times of 18 min provided essentially complete conversion No decrease in the activity of calcium carbonate was observed after weeks of utilization The robust structure is suitable for use in packed-bed reactors The catalyst used for the flow reactors was pulverized limestone Limestone from two locations was tested and found to be effective Catalyst removal requires only a screening process at the reactor discharge

Methyl Esterification of Free Fatty Acids of Rapeseed Oil as Treated in Supercritical Methanol

Abstract: Commercially available crude oils and fats contain on average 0.5-3% free fatty acids. These free fatty acids are known to react with the alkaline catalyst and form saponified products during transesterification reactions for biodiesel fuel production in the conventional commercial process. Purification of the products therefore becomes necessary after the reaction. In addition, it causes a longer production process and increases the production costs. For this aspect, supercritical methanol method without using any catalyst is evaluated in this work for reaction of free fatty acids. As a result, complete conversion is achieved for saturated fatty acids to methyl esters at temperatures above 400°C, whereas for unsaturated fatty acids, lower temperature of 350°C is appropriate, and higher temperature resulted in a degradation of the products. Consequently, a conversion of free fatty acids to methyl esters is highest, over 95%, when treated at 350°C. Fortunately, this temperature treatment is also most appropriate for transesterification of triglycerides. Thus, the overall conversion process of rapeseed oil to methyl esters is concluded to be adequate at 350°C. This finding supports the superiority of supercritical methanol method on biodiesel fuel production, compared with the conventional method, in which the production process becomes much simpler and increases the total yield due to the methyl esters produced from free fatty acids.

Glycerol transesterification with methyl stearate over solid basic catalysts. I. Relationship between activity and basicity

Abstract: The preparation of monoglycerides from fatty acids or fatty methyl esters and glycerol can be carried out in the presence of acid or basic catalysts. The use of solid basic catalysts could limit secondary reactions leading to product degradation. A comparison of several basic solids (MgO, CeO2, La2O3 and ZnO) has shown that the more significant the intrinsic basicity is, the more active the catalyst is. In order to increase the performance of these solids, several methods have been used for the preparation of MgO and CeO2. MgO prepared by hydration followed by calcination of a commercial raw material is the most active catalyst.

A Pilot Plant to Produce Biodiesel from High Free Fatty Acid Feedstocks

Abstract: Biodiesel is an alternative diesel fuel consisting of the alkyl monoesters of fatty acids from vegetable oils or animal fats. Currently, most biodiesel is made from soybean oil, methanol, and an alkaline catalyst. However, there are large amounts of fats and oils that are unsuitable for human consumption that could be converted to biodiesel at lower cost. The problem with processing these waste oils is that they often contain large amounts of free fatty acids that cannot be converted to biodiesel using an alkaline catalyst. These free fatty acids react with the alkaline catalyst to produce soaps that inhibit the separation of the biodiesel, glycerin, and wash water. Previous research has developed a process for pretreating these high free fatty acid feedstocks using acid catalysts which do not form soaps. The objective of this study was to construct a pilot plant to produce biodiesel from a wide variety of feedstocks including those with high free fatty acids. A 190-liter batch pilot plant has been built which can process high free fatty acid feedstocks using an acid-catalyzed pretreatment followed by an alkaline-catalyzed transesterification. Case studies of pilot plant-scale production of biodiesel from soybean oil, yellow grease with 9% free fatty acids, and brown grease with 40% free fatty acids are presented. The effect of varying the reaction parameters is discussed and the separation and washing processes are described. Estimates of the fuel cost using different feedstocks are also provided.

Synthesis and enzymatic degradation of high molecular weight aliphatic polyesters

Abstract: The aliphatic polyesters with high molecular weight have been prepared according to two methods. First is the synthesis of the polyesters by polycondensation of dimethyl succinate (DMS) with 1,4-butanediol (BD) using various metal alkoxides as a catalyst. Among the metal alkoxides used, titanium tetraisopropoxide [Ti(OiPr)4] gave the best results (highest molecular weight and yield). Thus, we have prepared aliphatic polyesters using a variety combinations of diesters [MeOOC—(CH2)x—COOMe, x = 2–8] with BD by the catalysis of Ti(OiPr)4. The polyesters with high number-average molecular weight (Mn> 35,000), except dimethyl adipate (DMA, x = 4)/BD polyester (Mn= 26,900), were obtained in high yield. The melting temperatures (Tm) of polyesters were relatively low (43.4–66.8°C) except that (115.6°C) of the DMS/BD polyester. Second is the synthesis of high molecular weight polyesters by chain extension reaction of lower molecular weight (Mn= 15,900–26,000) polyesters using hexamethylene diisocyanate (HDI) as a chain extender. The Mn values of chain-extended polyesters consequently increased more than two times (Mn= 34,700–56,000). The thermal properties of polyesters hardly changed before and after chain extension. Enzymatic degradations of the polyesters were performed using three different enzymes (cholesterol esterase, lipase B, and Rhizopus delemar lipase) before chain extension. The enzymatic degradability varied depending on both thermal properties of polyesters [melting temperature and heat of fusion (crystallinity)] and the substrate specificity of enzymes, but it was the following order: cholesterol esterase > lipase B > R. delemar lipase. The 1H-NMR spectrum of water-soluble degraded products of the polyester indicated that the polyester was degraded into a condensation product of diol with diester in a monomer form. The enzymatic degradation of chain extended polyesters was slightly smaller than that before chain extension, but proceeded steadily. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 340–347, 2001

Fatty Acid Steryl, Stanyl, and Steroid Esters by Esterification and Transesterification in Vacuo Using Candida rugosa Lipase as Catalyst

Abstract: Sterols (sitosterol, cholesterol, stigmasterol, ergosterol, and 7-dehydrocholesterol) and sitostanol have been converted in high to near-quantitative yields to the corresponding long-chain acyl esters via esterification with fatty acids or transesterification with methyl esters of fatty acids or triacylglycerols using lipase from Candida rugosa as biocatalyst in vacuo (20−40 mbar) at 40 °C. Neither organic solvent nor water is added in these reactions. Under similar conditions, cholesterol has been converted to cholesteryl butyrate and steroids (5α-pregnan-3β-ol-20-one or 5-pregnen-3β-ol-20-one) have been converted to their propionic acid esters, both in moderate to high yields, via transesterification with tributyrin and tripropionin, respectively. Reaction parameters studied in esterification include the temperature and the molar ratio of the substrates as well as the amount and reuse properties of the C. rugosa lipase. Lipases from porcine pancreas, Rhizopus arrhizus, and Chromobacterium viscosum are q...

Alternative Diesel Fuels from Vegetable Oils and Animal Fats

Abstract: Publisher Summary This chapter reviews competing technologies for converting vegetable oils and animal fats into diesel fuel besides biodiesel. Aside from transesterification to produce biodiesel, microemulsion/co-solvent blending and hydroprocessing (deoxygenation) appear to be the two most promising approaches for converting vegetable oils and fats into alternative diesel fuels. Microemulsion or co-solvent blend hybrid fuels is a relatively low-cost conversion process since it requires little more than the mixing of individual components at ambient temperature. Transesterification generally requires a slightly elevated temperature; a minimum reaction time, depending on catalyst; and several product separation and washing steps to prepare the biodiesel for distribution. Similarly, hydroprocessing generally requires elevated temperature and hydrogen pressure; a minimum reaction time, depending on catalyst; condensation; and the fractionation of liquid products. Although hydroprocessing and transesterification may be economically competitive with each other, it is unlikely either approach will compare favorably with hybrid fuel formulation. Other advantages favoring hybrid fuel formulation over transesterification or hydroprocessing include adaptability to large-scale continuous flow processing equipment, no catalysts to recover or re-generate, no excess alcohol, no by- or co-products, and no product separation/fractionation steps. All compounds, including amphiphiles used in hybrid fuel formulations, may be derived from renewable agricultural feedstocks. Another disadvantage for hydroprocessing is the likelihood that it has an unfavorable energy balance. Life cycle analyses for biodiesel generally indicate that it gives back more than three times the energy required to produce it resulting in a net positive energy balance.

Biodiesel from rapeseed oil, methanol and KOH. 2. Composition of solution of KOH in methanol as reaction partner of oil

Abstract: The composition of the solutions of solid KOH in methanol has been measured by means of determinating the content of water in the equilibrium mixture. The dependence of the equilibrium reaction extent ξ 1 and the concentration equilibrium constant Kc on the ratio of the initial amounts of methanol and KOH containing 0.164 and 16.27 wt-% of water are determined and theoretically described. The concentration of CH 3 O ions can be calculated with these results. This value is very important for the course of the alkaline catalyzed methanolysis of rapeseed oil to biodiesel, because the methoxide ions are the true catalyst of such a transesterification. La composition des solutions de KOH solide dans le methanol et l'eau dans le melange a l'equilibre ont ete determines. La concentration de CH3O - est calculee. cette valeur est importante dans la methanolyse alcaline de l'huile de colza, les ions methoxide etant les catalyseurs de la transesterification.

Polyester and polycarbonate synthesis by in vitro enzyme catalysis.

Abstract: Enzyme technology has significantly expanded in scope and impact over the past 10 years to include organic transformations in non-traditional environments. This is in part due to an increased understanding and capability of using enzyme catalysis in a wide variety of organic solvents, at interfaces, and at high temperatures and pressures. This review focuses on a relatively new but rapidly expanding research activity where in vitro enzyme catalysis is used for the synthesis of non-natural polyesters and polycarbonates. The inclination to use of enzymes for polymer synthesis has been fueled by a desire to carry out these reactions in the absence of heavy metals, at lower temperatures, and with increased selectivity. Aspects of this work that include enzyme-catalyzed step-growth condensation reactions, chain-growth ring-opening polymerizations, and corresponding transesterification of macromolecular substrates are discussed.

Polyesters by lipase-catalyzed polycondensation of unsaturated and epoxidized long-chain α,ω-dicarboxylic acid methyl esters with diols

Abstract: Long-chain, symmetrically unsaturated α,ω-dicarboxylic acid methyl esters (C18, C20, C26) were obtained by the catalytic metathetical condensation of 9-decenoic, 10-undecenoic, and 13-tetradecenoic acid methyl esters, respectively, with the homogeneous Grubbs catalyst bis(tricyclohexyl phosphine) benzylidene ruthenium dichloride dissolved in methylene chloride. The dicarboxylic acid esters were epoxidized chemoenzymatically with H2O2/methyl acetate with Novozym 435®, an immobilized lipase B from Candida antarctica. Polyesters from symmetrically unsaturated or epoxidized α,ω-dicarboxylic acid methyl esters with 1,3-propanediol or 1,4-butanediol, respectively, were achieved by enzymatic polycondensation with the same biocatalyst applied. With 1,3-propanediol as a substrate, the linear unsaturated and epoxidized polyesters had molecular weights of 1950–3300 g/mol and melting points of 47–75 °C, whereas with 1,4-butanediol as a substrate, the resulting polyesters showed higher molecular weights, 7900–11,600 g/mol, with similar melting points of 55–74 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1601–1609, 2001

Method of preparing lower alkyl fatty acids esters and in particular biodiesel

Abstract: The present invention relates to a technique for enhancing the activity of an immobilized lipase, and a technique for regenerating a deactivated immobilized lipase, in which an alcohol with a carbon atom number not less than three is used to swell and/or clean said immobilized lipase. Said immobilized lipase is particularly useful in a method of preparing biodiesel by transesterification of triglycerides and a lower alcohol.

The effect of vinyl esters on the enantioselectivity of the lipase-catalysed transesterification of alcohols

Abstract: The enantioselectivity of the lipase from Pseudomonas cepacia (PCL) in the transesterification of 2-phenyl-1-propanol 1 was studied using a series of vinyl 3-arylpropanoates as acyl donors. The most enantioselective transesterification reaction of the alcohol was attained by using vinyl 3-( p -iodophenyl)- or 3-( p -trifluoromethylphenyl)propanoates, with enantiomer ratios, E , of 116 and 138, respectively. Vinyl 3-phenylpropanoate was also effective for the resolution of 1 mediated by lipases from P . fluorescens and porcine pancreas and for the PCL-catalysed transesterification of several 2-phenyl-1-alkanols. The enantiomeric resolution of 1 was practically carried out by the first enantioselective transesterification using PCL and vinyl 3-( p -iodophenyl)propanoate to afford ( R )- 1 and then the enantioselective hydrolysis of the resultant ester to afford ( S )- 1 .

Polyesters of ω-unsaturated fatty acid derivatives

Abstract: Unsaturated polyesters, based on ω-unsaturated fatty acid esters from oleochemical resources and petrochemical diols, were synthesized via two different synthetic pathways. 9-decenoic and 10-undecenoic acid methyl ester Ia, b were transesterified with petrochemical diols to produce the a,ω-alkylene di(un)decenoates IIa-d, which were subsequently converted into unsaturated polyesters by acyclic diene metathesis polymerization. A sercening of ten homogeneous and beterogeneous metathesis catalysts was performed, implying optimum results for B 2 O 3 -Re 2 O 7 /Al 2 O 3 -SiO 2 + SnBu 4 . Molecular weights (M w ) up to 100000 g/mol were determined by MALLS-GPC. On the ether hand, C 10 , C 11 and C 14 -ω-unsaturated fatty acid methyl esters Ia-c were metathetically dimerized using homogeneous ruthenium and tungsten carbene complexes at an extremely low catalyst concentration. The resulting symmetrical, internally unsaturated, dicarboxylic acid dimethyl esters IIIa-c were polycondensated in bulk with conventional transesterification catalysts achieving molecular weights (M w ) up to 110000 g/mol. Melting temperatures of 6 to 92°C were determined by DSC.

Response surface modelling of the production of ω-3 polyunsaturated fatty acids-enriched fats by a commercial immobilized lipase

Abstract: The aim of this study was to model the production of fats, enriched with ω-3 polyunsaturated fatty acids (ω-3 PUFA) for nutraceutical purposes, via the response surface methodology. These fats were obtained by transesterification of palm oil stearin (POS) with a concentrate (EPAX 2050TG) of triglycerides enriched with ω-3 PUFA and soybean oil, catalysed by a commercial immobilized Candida antarctica lipase (“Novozym 435”). The initial water activity ( a w ) of the biocatalyst, POS and EPAX 2050TG concentrations, time and temperature showed a significant effect on the transesterification reaction, as well as on the competing reactions of hydrolysis and lipid oxidation. Depending on the factors included, the transesterification reaction was described either by first- or second-order models. The production of free fatty acids, which is ascribed both to the hydrolytic reaction and the mechanism of lipase-catalysed transesterification, showed a second-order dependence on the initial a w of the biocatalyst.

Enzyme‐catalyzed transesterification of vinyl esters on cellulose solids

Abstract: Enzyme-catalyzed transesterification of several cellulose solids in organic media have been investigated Several protease enzymes were made soluble in organic media through ion-paired enzyme–surfactant complexes Subtilisin Carsberg was found to be catalytically active in the transesterification of cellulose with vinyl propionate and vinyl acrylate in anhydrous pyridine The ester carbonyl groups in acylated cellulose derivatives were confirmed by Fourier transform infrared spectroscopy The surfaces of these cellulose derivatives became hydrophobic as demonstrated by increased water-contact angles The enzyme-catalyzed transesterification was confirmed to regioselectively target the primary hydroxyl group of cellulose by reactions on specifically substituted cellulose The cellulose esters from enzyme-catalyzed transesterification could be hydrolyzed partially by the same enzyme in aqueous media, and were thus biodegradable Surface grafting of cellulose acrylate was demonstrated using azobisisobutyronitrile-initiated polymerization of acrylonitrile in dimethylformamide Polyacrylonitrile (PAN)-g-cellulose shows a different thermal behavior from cellulose, homopolymer PAN, and PAN/cellulose blends The grafted PAN on PAN-g-cellulose at a 16% grafting add-on is incapable of cyclization © 2001 John Wiley & Sons, Inc J Polym Sci A: Polym Chem 39: 1931–1939, 2001