Showing papers on "Transesterification published in 2002"

Biodiesel Fuels from Vegetable Oils: Transesterification of Cynara cardunculus L. Oils with Ethanol

Abstract: A study was made of the transesterification reaction of Cynara cardunculus L. oil by means of ethanol, using sodium hydroxide and potassium hydroxide as catalysts. The objective of the work was to ...

An alkali–catalyzed transesterification process for high free fatty acid waste oils

Abstract: Vegetable oil used for deep–frying processes becomes a contaminating waste product after use. It represents a problem for disposal and for wastewater systems. Among the possibilities for recycling of used vegetable oil, conversion into biofuel is very interesting and promising. In this work, a comparison between biofuels from waste vegetable oils from several countries was carried out. The raw materials used were the most common waste oils from Brazil (palm oil and hydrogenated fat), Spain (olive oil), and Germany (mixture of several vegetable oils). The transesterification process was carried out in two steps, using a stoichiometric amount of methanol and the necessary amount of KOH, supplemented with the exact amount of KOH to neutralize acidity. Both reactions were completed in 30 min. The temperature was in the range of 40 ³ C to 60 ³ C. Several parameters were analyzed, including density, viscosity, water content, and energy content. Results revealed that free fatty acid (FFA) content is a key parameter for determining the viability of the waste vegetable oil transesterification process. To carry the reaction to completion, an FFA value lower than 3% is needed; the higher the acidity of the oil, the smaller the conversion efficiency. Both excess as well as insufficient amount of catalyst may cause soap production. All methyl esters had adequate density values, but slightly higher viscosity values, which could contribute to incomplete combustion. Results showed that higher heat values (HHV) were 14% lower for biodiesel samples than for diesel fuel, which can be tolerated. Finally, we conclude that the two–step transesterification process (without any costly purification step) is an economic method for biofuel production using the waste vegetable oils tested.

Characterization and degradation behavior of poly(butylene adipate-co-terephthalate)s

Abstract: Random copolyesters based on 1,4-butanediol and different ratios between adipic and terephthalic units were synthesized from thermal polycondensation of the appropriate mixture of monomers or by melt transesterification of the mixture of homopolymers. 1H NMR spectroscopy makes feasible the study of the average block lengths of polymers once synthesized and after degradation in different media. Calorimetric data are reported, including those referred to the study of isothermal and nonisothermal crystallizations. Degradability of samples was evaluated by different methods including NMR and thermal analysis, evaluation of molecular weight by gel permeation chromatography or from intrinsic viscosity measures, scanning electron micrographs, and changes in mechanical properties. Distilled water at 70 °C acidic conditions provided by a pH 2.3 aqueous medium and enzymatic media containing lipases from Pseudomonas cepacia or Candida cylindracea were considered in this study. The degradability of the studied copolyesters strongly depends on the terephthalate content and the degradation media. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4141–4157, 2002

Effect of oxidation under accelerated conditions on fuel properties of methyl soyate (biodiesel)

Abstract: Biodiesel derived from transesterification of soybean oil and methanol is an attractive alternative fuel for combustion in direct-injection compression ignition (diesel) engines. During long-term storage, oxidation due to contact with air (autoxidation) presents a legitimate concern with respect to maintaining fuel quality of biodiesel. This work examines the effects of oxidation under controlled accelerated conditions on fuel properties of methyl soyate (SME). SME samples from four separate sources with varying storage histories were oxidized at elevated temperature under a 0.5 standard cm3/min air purge and with continuous stirring. Results showed that reaction time significantly affects kinematic viscosity (ν). With respect to increasing reaction temperature, ν, acid value (AV), PV, and specific gravity (SG) increased significantly, whereas cold flow properties were minimally affected for temperatures up to 150°C. Antioxidants TBHQ and α-tocopherol showed beneficial effects on retarding oxidative degradation of SME under conditions of this study. Results indicated that ν and AV have the best potential as parameters for timely and easy monitoring of biodiesel fuel quality during storage.

Immobilized lipase‐catalysed production of alkyl esters of restaurant grease as biodiesel

Abstract: Simple alkyl ester derivatives of restaurant grease were prepared using immobilized lipases as biocatalysts. The lipases studied included those of Thermomyces lanuginosa and Candida antarctica supported on granulated silica (gran- T.l. and gran- C.a., respectively), C. antarctica supported on a macroporous acrylic resin (SP435) and Pseudomonas cepacia immobilized within a phyllosilicate sol-gel matrix (IM PS-30). All alcoholysis reactions were carried out in solvent-free media employing a one-step addition of the alcohol to the reaction system. Of the lipases studied, IM PS-30 was found to be the most effective in catalysing the methanolysis and ethanolysis of grease. The processes catalysed by gran- T.l. and gran- C.a. lipases gave poor conversions to esters, and the SP435-catalysed reactions gave intermediate yields of ethyl and methyl esters. Water activity (a(w)) was an important factor in the methanolysis reactions; reaction media with a(w)<0.5 resulted in the highest conversions to methyl esters. Molecular sieves also improved methyl ester yields by as much as 20% in transesterification reactions catalysed by IM PS-30. The immobilized lipases also were evaluated for their ability to produce alkyl esters of grease with several additional normal and branched-chain alcohols.

Enzymatic Biodiesel Production from Sunflower Oil by Candida antarctica Lipase in a Solvent-free System

Abstract: Methanolysis (transesterification with methanol) of sunflower oil by lipase from Candida antarctica (Novozym 435) in a solvent-free system has been studied. Stepwise as well as continuous methanol feeding was applied to avoid strong substrate inhibition. Glycerol was found to cause strong product inhibition on the enzymatic reaction, therefore glycerol removal by dialysis was investigated using a flat sheet membrane module.

Phosphines: Nucleophilic organic catalysts for the controlled ring‐opening polymerization of lactides

Abstract: A new metal-free synthetic approach to the controlled ring-opening polymerization (ROP) of lactide with nucleophilic phosphines as transesterification catalysts is described. P(Bu)3, PhPMe2, Ph2PMe, PPh3, and related phosphines are commercially available, inexpensive catalysts that generate narrowly dispersed polylactides with predictable molecular weights. These organic catalysts must be used in combination with an initiator, such as an alcohol, to generate an alcoholate ester α-end group upon ROP. A likely polymerization pathway is through a monomer-activated mechanism, with minimal active species, facilitating narrow molecular weight distributions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 844–851, 2002; DOI 10.1002/pola.10168

Diesel Fuel from Vegetable Oil via Transesterification and Soap Pyrolysis

Abstract: Transesterifications of 6 vegetable oil samples in supercritical methanol (SC MeOH) were studied without using any catalyst. Methyl esters of vegetable oils have several outstanding advantages among other new-renewable and clean engine fuel alternatives. The variables affecting the methyl ester yielded during the transesterification reaction, such as the molar ratio of alcohol to vegetable oil and reaction temperature, were investigated. Compared to No. 2 diesel fuel, all of the vegetable oils are much more viscous, while methyl esters of vegetable oils are the slightly more viscous. The methyl esters are more volatile than those of the vegetable oils. The soaps obtained from the vegetable oils can be pyrolyzed into hydrocarbon-rich products.

At low water activity alpha-chymotrypsin is more active in an ionic liquid than in non-ionic organic solvents

Abstract: The kinetics of the alpha-chymotrypsin catalysed transesterification of N-acetyl-l-phenylalanine ethyl ester with 1-butanol and the competing hydrolysis were evaluated at fixed water activity in two ionic liquids and two non-ionic organic solvents. In most respects the four solvents behaved similarly. However, at a water activity of 0.33, higher catalytic activity was observed in the ionic liquid, 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide, than in the other solvents, and at a(w)=0.11 catalysis was only observed in this solvent.

Chemoenzymatic synthesis2 of both enantiomers of fluoxetine, tomoxetine and nisoxetine: lipase-catalyzed resolution of 3-aryl-3-hydroxypropanenitriles

Abstract: A facile preparation of (±)-3-hydroxy-3-phenylpropanenitrile has been carried out by ring-opening of styrene oxide with NaCN in aqueous ethanol. Subsequent kinetic resolution of this material via lipase-mediated transesterification gave the S- alcohol and R- acetate in excellent yields and high enantioselectivities, particularly with lipase PS-C ‘Amano’ II. The effect of solvents and immobilization of the lipase has also been investigated. It is interesting to note that the use of immobilized lipase for this transesterification process in hydrophobic solvents (diisopropyl ether, toluene and hexane) enhanced the reaction rate drastically and gave optimal yields with high enantioselectivity (>99%). Moreover, enantiopure 3-hydroxy-3-phenylpropanenitrile products have been converted via enantioconvergent routes into the ( R )- and ( S )-enantiomers of the important anti-depressants fluoxetine, tomoxetine, nisoxetine and norfluoxetine.

Continuous flow biodiesel production

Abstract: Biodiesel, which consists of the fatty acid esters of simple alcohols, is a potential replacement for a portion of thediesel fuel used in transportation. It is produced from both used (oil that has been utilized for frying and discarded) and newvegetable and animal fats and oils. It has several advantages. Among these advantages are its classification as a renewableresource, its ability to reduce HC, CO, and CO2 exhaust emissions, its nontoxic character, and its biodegradability. One ofthe keys to making biodiesel a viable and profitable energy source is the use of a continuous flow transesterification processto reduce time and cost, thereby increasing production and profit. A continuous flow esterification process for producing biodiesel from rapeseed oil and ethanol was investigated. Theequipment consisted of an oil metering pump, centrifugal mixing pump, ethanol and catalyst metering pump, static mixers,laddertype retention reactor, water injection system, and continuous flow centrifugal separating system. The oil feed ratewas 0.38 L/min that yields about three times the weekly production of the existing batch type transesterification system thatproduces 945 L (250 gal) per batch. It was anticipated that if methanol were used instead of ethanol that the flow rate couldbe considerably increased. The system in its present configuration has met ASTM PS12199 standard for free and total glycerol. The centrifugalseparation resulted in release of excessive alcohol vapors. A vapor recovery and condensing system should be installed. Thislatter system could help further reduce costs of the biodiesel produced by recycling some of the alcohol used.

Enantioselective transesterification of a tertiary alcohol by lipase A from Candida antarctica

Abstract: Chiral tertiary alcohols and their esters represent important flavor compounds and are useful building blocks Unfortunately, they are accepted by only a few lipases/esterases as substrates and enantioselectivity is usually very low We report here a highly enantioselective transesterification of the tertiary alcohol 2-phenylbut-3-yn-2-ol using lipase A from Candida antarctica (CAL-A) Under optimized conditions, the corresponding acetate was obtained with 94%ee at 35% conversion equivalent to an enantioselectivity factor of E=65 In contrast, enantioselective hydrolysis of the racemic acetate was not feasible as this is very prone to autohydrolysis

Synthesis of phosphatidylcholine with defined fatty acid in the sn-1 position by lipase-catalyzed esterification and transesterification reaction.

Abstract: The incorporation of caproic acid in the sn-1 position of phosphatidylcholine (PC) catalyzed by lipase from Rhizopus oryzae was investigated in a water activity-controlled organic medium. The reaction was carried out either as esterification or transesterification. A comparison between these two reaction modes was made with regard to product yield, product purity, reaction time, and byproduct formation as a consequence of acyl migration. The yield in the esterification and transesterification reaction was the same under identical conditions. The highest yield (78%) was obtained at a water activity (a(w)) of 0.11 and a caproic acid concentration of 0.8 M. The reaction time was shorter in the esterification reaction than in the transesterification reaction. The difference in reaction time was especially pronounced at low water activities and high fatty acid concentrations. The loss in yield due to acyl migration and consequent enzymatic side reactions was around 16% under a wide range of conditions. The incorporation of a fatty acid in the sn-1 position of PC proved to be thermodynamically much more favorable than the incorporation of a fatty acid in the sn-2 position.

Procedure to obtain biodiesel fuel with improved properties at low temperature

Abstract: Procedure to generate biodiesel fuels with improved properties at low temperature by the transesterification of triglycerides with alcohols such as methanol or ethanol, optionally in the presence of methyl or ethyl acetates of fatty acids and an inert solvent, to produce methyl or ethyl esters of fatty acids, glycerine and, where appropriate, glycerine triacetate, followed by the separation of crude glycerine that is reacted with aldehydes, ketones and/or acetic acid or methyl or ethyl acetates to produce acetals, glycerine cetals and/or glycerine acetates. The acetals, glycerine cetals and/or glycerine acetates are mixed with methyl or ethyl esters of fatty acids in concentrations of approximately 0.5-20% by weight to obtain a biodiesel with improved properties at low temperatures.

Efficient Lipase-catalyzed Enantioselective Acylation under Reduced Pressure Conditions in an Ionic Liquid Solvent System.

Abstract: Lipase-catalyzed transesterification was demonstrated using methyl esters as acyl donors under reduced pressure in an ionic liquid ([bmim]PF6) solvent system. The transesterification of 5-phenyl-1-penten-3-ol took place smoothly under reduced pressure at 27 hPa at 40 °C when methyl phenylthioacetate was used as acyl donor in [bmim]PF6, and we succeeded in obtaining the corresponding acylated compound in optically pure form; this makes it possible to use lipase repeatedly because there was no drop in the reaction rate despite three repetitions of the process.