Showing papers on "Transesterification published in 1984"

Variables affecting the yields of fatty esters from transesterified vegetable oils

Abstract: Transesterification reaction variables that affect yield and purity of the product esters from cottonseed, peanut, soybean and sunflower oils include molar ratio of alcohol to vegetable oil, type of catalyst (alkaline vs acidic), temperature and degree of refinement of the vegetable oil. With alkaline catalysts (either sodium hydroxide or methoxide), temperatures of 60 C or higher, molar ratios of at least 6 to 1 and with fully refined oils, conversion to methyl, ethyl and butyl esters was essentially complete in 1 hr. At moderate temperatures (32 C), vegetable oils were 99% transesterified in ca. 4 hr with an alkaline catalyst. Transesterification by acid catalysis was much slower than by alkali catalysis. Although the crude oils could be transesterified, ester yields were reduced because of gums and extraneous material present in the crude oils.

Enzymatic catalysis in organic media at 100 degrees C

Abstract: Porcine pancreatic lipase catalyzes the transesterification reaction between tributyrin and various primary and secondary alcohols in a 99 percent organic medium. Upon further dehydration, the enzyme becomes extremely thermostable. Not only can the dry lipase withstand heating at 100 degrees C for many hours, but it exhibits a high catalytic activity at that temperature. Reduction in water content also alters the substrate specificity of the lipase: in contrast to its wet counterpart, the dry enzyme does not react with bulky tertiary alcohols.

Rapeseed oil transesterification by heterogeneous catalysis

Abstract: Methyl fatty esters derived from vegetable oils are a promising fuel for direct injection diesel engines. This study’s purpose was to identify a heterogeneous catalyst to selectively produce methyl fatty esters from low erucic rapeseed oil. Most experiments were at atmospheric pressure and approximately the corresponding boiling point temperature of the mixture, 60–63 C. However, the catalytic activity of an anion exchange resin was tested at 200 C and 68 atm (1000 psig) and at 91 C and 9.2 atm (135 psig). All samples were analyzed by thin layer chromatography with samples from the elevated temperature and pressure experiments also analyzed by mass spectroscopy. The most promising catalyst examined was CaO·MgO. The activities of the catalysts CaO and ZnO appear to be enhanced with the addition of MgO, therefore the transesterification reaction mechanism may be, in this instance, bifunctional. The anion exchange resin catalyst at 200 C and 68 atm generated substantial amounts of both methyl fatty esters and straight-chain hydrocarbons, even though these reactions did not go to completion. At 91 C and 9.2 atm the cracking also occurred but at a substantially reduced rate, and no transesterification was noted.

Comparison of different strategies for the lipase-catalyzed preparative resolution of racemic acids and alcohols: Asymmetric hydrolysis, esterification, and transesterification.

Abstract: Lipase from Candida cylindracea has been found to be a highly stereospecific catalyst suitable for preparative resolution of racemic acids and alcohols. Using (R, S)-2-(p-chlorophenoxy) propionic acid (whose R isomer is a herbicide) and (R, S)-sec-butanol (a versatile synthon) as model compounds, three alternative approaches to lipase-catalyzed resolutions-asymmetric hydrolysis, esterification, and transesterification-have been compared. Enzymatic esterification in biphasic systems has been ruled out for preparative resolutions because addition of the acids lowers the pH of the aqueous phase thereby greatly reducing the efficiency of the procedure. Both enzymatic hydrolysis and biphasic transesterification afforded resolution of the racemates on a gram scale. From the standpoint of productivity, ease of product separation, and the amount of steps required, lipasecatalyzed asymmetric hydrolysis has been judged to be superior for the practical resolution of racemic acids, and lipase-catalyzed asymmetric transesterification to be the method of choice for the practical resolution of racemic alcohols.

Synthesis of higher polyol fatty acid polyesters using high soap:polyol ratios

Abstract: An improved solvent-free transesterification process for producing higher polyol fatty acid polyesters is disclosed. In this process a mixture of a polyol, a fatty acid methyl, 2-methoxy ethyl or benzyl ester, an alkali metal fatty acid soap, and a basic catalyst, having a molar ratio of soap:polyol of from about 0.6:1 to about 1:1, preferably from about 0.75:1 to about 1:1, is heated to form a homogeneous melt. To this melt is subsequently added excess fatty acid methyl, 2-methoxy ethyl or benzyl ester, yielding the desired polyol fatty acid polyesters.

Process for the production of fatty acid esters of short-chain aliphatic alcohols from fats and/or oils containing free fatty acids

Abstract: For the production of fatty acid esters of short-chain, aliphatic alcohols by the catalytic transesterification of natural fats and/or oils containing free fatty acids (oil phase) with the corresponding monoalcohols, the oil phase is subjected to preliminary esterification with the monoalcohols in the presence of acidic esterification catalysts at temperatures no higher than 120° C. and under pressures no higher than 5 bars and in the presence of a liquid entraining agent substantially immiscible with the oil phase, after which the reaction product is separated into an entraining agent phase containing the acidic catalyst and water of reaction and the treated oil phase, the oil phase is then subjected to transesterification while the acidic catalyst-containing entraining agent phase is returned, after at least partial drying, to the preliminary esterification stage. By this process, fats and/or oils with acid numbers of up to 60 can be processed in the preliminary esterification stage to give an oil phase having a low acid number.

Blends of poly(ethylene terephthalate) and a polyarylate before and after transesterification

Abstract: Blends of poly(ethylene terephthalate) (PET) and a copolyester of bisphenol A–terephthaloylisophthaloyl (PAr) (2:1:1) have been studied both before and after transesterification. The physical blends exhibit phase separation in their amorphous states: a pure PET phase and a mixed PAr-rich phase. In spite of this phase separation, PET crystallinity in blends, normalized to PET fraction, surprisingly goes through a maximum at 25% PAr content. The transesterfied copolymers are noncrystallizable and exhibit a single Tg between those of starting polymers, PET and PAr.

Process for the preparation of sterically hindered hydroxyphenylcarboxylic acid esters

Abstract: Process for the preparation of sterically hindered hydroxyphenylcarboxylic acid esters Abstract If the transesterification of esters of the formula II with alcohols of the formula III A-(OH)m is catalysed by successive treatment with catalytic amounts a) of an organometallic compound of a metal of the fourth main group or the fourth sub-group of the periodic system and b) of an acid earth, compounds of the formula I are obtained in virtually quantitative yield and the products thus obtained contain no troublesome by-products and do not have to be additionally purified and the products are useful stabilizators for example for poly-mers, oils and the like.

Reaction method for transesterifying fats and oils

Abstract: A two-step reaction method for the transesterification of fats and oils, comprising hydrolyzing fats and oils to produce diglycerides by reacting said fats or oils with lipase; esterifying said digylcerides and to produce triglycerides by reacting said diglycerides with at least one fatty acid.

Cholesterol ester formation by transesterification of chlorambucil: a novel pathway in drug metabolism.

Abstract: (1984). Cholesterol ester formation by transesterification of chlorambucil: A novel pathway in drug metabolism. Xenobiotica: Vol. 14, No. 7, pp. 569-574.

Process for the continuous production of polybutylene terephthalate of high molecular weight

Abstract: Continuous multistep, economical, energy-saving process for making polybutylene terephthalate in which the butanediol-1,4 used to transesterify dimethyl terephthalate is supplied from the condensed vapors volatilized during the precondensation and polycondensation steps of the process. These vapors, which contain low-soluble esters of terephthalic acid as well as butanediol, are condensed by contact with fresh butanediol, and volatilized butanediol containing the esters is recycled to the initial transesterification stage for reaction with dimethyl terephthalate. No additional butanediol is required for the reaction.

Optimization of the transesterification stage of polyethylene terephthalate reactors

Abstract: The tranesterification step of the polyethylene terephthalate (PET) formation consists of several side reactions in addition to the main ester interchange, transesterification, and polycondensation reactions. The side reactions considered in this work are acid end group, acetaldehyde, diethylene glycol, water, and vinyl end group formations. The objective function of the batch esterinterchange reactor is assumed to consist of maximizing the conversion and simultaneously minimizing the formation of side products. The control vector iteration procedure has been used to optimize the esterinterchange reactor and the temperature-time profile that gives the best performance has been found. It is found that the reactor should be operated at a high temperature initially to obtain high conversion of dimethyl terephthalate (DMT) first, but then it should be lowered to reduce the formation of side products.

An immoblized lipase preparation and use thereof

Abstract: An immobilized lipase preparation obtainable by contacting an aqueous solution of a microbial lipase with a weak anion exchange resin at specified conditions in regard to pH and contact time, whereafter the preparation is isolated and dried. The preparation can be used for continuous transesterification of fats without solvents or other expensive auxiliary agents.

Aspects of the Chemistry of Poly(ethylene Terephthalate). III. Transesterification of Dimethyl Terephthalate with Ethylene Glycol in the Presence of Various Catalytic Systems

Abstract: The transesterification of dimethyl terephthalate has been studied by measuring the amount of methanol formed as a function of time. The influence of various catalytic systems was investigated with regard to the nature and concentration of the metal ion and temperature. The order of decreasing activity was found to be Pb, Zn, Mn, Sn, Sb, Ti, and mixtures of Zn plus Pb and Zn plus Sb were found to be synergistic. The postulate that there is a correlation between the metal oxygen bond and the activity of the catalyst is discussed.

Process for the production of polyester copolymers

Abstract: The invention is a process for esterifying organic dicarboxylic acid and diol at elevated temperatures and thereafter transesterifying the esterification product in the presence of a diol and a diester at elevated temperatures thereafter polymerizing the transesterification product in a condensation stage to form a polycondensed copolyester having an intrinsic viscosity from .2 to .9.

Process for production of alkyl silicates from silicon metal

Abstract: Ethyl orthosilicate is produced by contacting silicon metal with a mixture of methanol and ethanol in the presence of a catalytic amount of an alkali metal metal carbonate or bicarbonate at a temperature of at least 130°C. The methyl orthosilicates produced are converted to ethyl orthosilicate by transesterification with ethanol.

Transesterification of dimethyl terephthalate with ethylene glycol

Abstract: For the first time, data are given on the quantitative composition of the transesterification products of dimethyl terephthalate with ethylene glycol at various molar ratios of the starting materials.

Polyoxyalkylenediol-alpha, omega-bisallyl polycarbonate useful as a base for sealants and process for its preparation

Abstract: For preparing polyoxyalkylenediol-α,ω-bisallyl policarbonates, diallyl carbonate is reacted in a first reaction stage with a polyoxyalkylenediol having a mol wt between 400 and 4500 in the presence of a transesterification catalyst at a temperature in the neighborhood of 100° C. and under reduced pressures, whereafter, in a second reaction stage, the product as obtained from the first stage is treated at a temperature between 70° C. and 150° C. under reduced pressures, still in the presence of a transesterification catalyst. By so doing, the chain extension of the bisallyl carbonate of the polyoxyalkylenediol is achieved, whereas the unreacted diallyl carbonate coming from the first stage, and that produced in the second stage, are eliminated, and the final reaction product can thus be collected.

Predominant transesterification reaction catalyzed by immobilized trypsin.

Abstract: Immobilized trypsin covalently attached to cross-linked dextran was prepared. In the presence of high concentrations of primary and secondary alcohols, the transesterification of L-lysine esters catalyzed by the immobilized trypsin was observed to be predominant. In contrast to this, no transesterified product was detected with tertiary butyl alcohol. These reactions were compared with the acid-catalyzed transesterification reactions and the characteristics of the enzymatic reaction are discussed.

Curable compositions for producing polyurethane foams

Abstract: A composition curable by reaction with an organic polyisocyanate to a polymer foam in which the predominant recurring polymer unit is isocyanurate, comprises a halogen­ ated organic blowing agent; a polyester polyol mixture and a polyether polyol having an average hydroxyl functionality of at least 4 comprising the adduct of at least 4 moles of a C₂-C₆ alkylene oxide and an organic compound having at least 4 functional groups reactive with said alkylene oxide. The polyester polyl mixture is prepared by: (a) transesterification, with a glycol of molecular weight from 60 to 400, of a residue remaining after dimethyl terephthalate and methyl p-toluate have been removed from the product of oxidation of p-xylene in the preparation of dimethyl terephthalate; or (b) esterification, with an alkylene oxide selected from ethylene oxide, propylene oxide, butylene oxide, and mix­ tures thereof, of a carboxyl functional residue resulting from the removal of terephthalic acid from the mixture obtained by the oxidation of p-xylene in the preparation of terephtha­ lic acid.

Electrodeposition of resinous compositions curable through a transesterification curing mechanism

Abstract: Coating compositions comprising a polymeric polyol with a polyester crosslinking agent having at least two gamma and/or delta-hydroxyester groups per molecule are disclosed. The compositions, when applied to a substrate and cured in the presence of a transesterification catalyst, give solvent-resistant coatings.

Separation of Methanol from mixtures containing it

Abstract: A substantially anhydrous mixture of methanol with an organic compound with which it forms an azeotrope can be separated by dissolving into the mixture lithium chloride or other suitable salt that forms a complex with methanol so as to form a homogeneous mixture, adding an organic solvent that is miscible with the organic compound but immiscible with the complex and thereby forming a heterogeneous mixture, and separating the phases. The methanol can be recovered from one phase and the organic compound from the other. The organic compound may typically be methyl acrylate or methacrylate, the blend being, for instance, obtainable during the transesterification of methyl (meth)acrylate with an alcohol to form a higher boiling ester such as dimethylaminoethyl (meth)acrylate or 2-ethylhexyl acrylate.

Production of modified polyester

Abstract: PURPOSE:To obtain a basic dye-dyeable modified polyester, by adding a solution containing a bishydroxyethyl ester of a 5-metalosulfoisophthalic acid and a bishydroxyethyl ester of a dicarboxylic acid to ethylene terephthalate and polycondensing the mixture. CONSTITUTION:The purpose modified polyester is obtained by mixing (A) an esterification product obtained by esterifying terephthalic acid with ethylene glycol (EG) at an esterification degree of above 90% and EG/terephthalic acid molar ratio of 1.07-1.4 with (B) an EG solution of 0.5-5mol of a reaction product obtaned by transesterifying a dimethyl 5-metalosulfoisophthalate with EG at a transesterification degree of above 95%, and (C) a bishydroxyethyl ester of a discarboxylic acid in amounts which can satisfy the inequalities (wherein mol- BHET is the number of moles of component C, and mol-SEIS is the number of moles of component B) and polycondensing the mixture.