Ethylene glycol, esterification with

Ethylene glycol esterification of BHET is driven to completion by heating and removal of the water formed. PET is also formed using the same chemistry starting with dimethyl terephthalate [120-61-6] and ethylene glycol to form BHET also using an antimony oxide catalyst. 

The OH functionality on cholesterol (Choi) can be used directly for the esterification with COOH end-functionalized polymers, by the aid of dicyclohexylcar-bodiimide (DCC) and DMAP (Scheme 14) [114]. Star-shaped and linear poly (ethylene glycol) (PEG) with terminal Cfiol entities have been prepared, and used... 

Polymerisation of a diol with a dicarboxybe acid is exemplified by the production of a polyester from ethylene glycol and terephthabc acid either by direct esterification or by a catalysed ester-interchange reaction. The resulting polyester (Terylene) is used for the manufacture of fibres and fabrics, and has high tensile strength and resibency its structure is probably ... 

Oxalic acid produced from syngas can be esteiified (eq. 20) and reduced with hydrogen to form ethylene glycol with recovery of the esterification alcohol (eq. 21). Hydrogenation requires a copper catalyst giving 100% conversion with selectivities to ethylene glycol of 95% (15). 

Chemical Properties. Neopentyl glycol can undergo typical glycol reactions such as esterification (qv), etherification, condensation, and oxidation. When basic kinetic studies of the esterification rate were carried out for neopentyl glycol, the absolute esterification rate of neopentyl glycol with / -butyric acid was approximately 20 times that of ethylene glycol with / -butyric acid (7). 

The most important derivatives of the carboxyl group are formed by esterification with monohydric or polyhydric alcohols. Typical alcohols used iaclude methyl alcohol, ethylene glycol, glycerol, and pentaerythritol. These rosia esters have a wide range of softening poiats and compatibiUties. 

Eatty acid ethoxylates are used extensively in the textile industry as emulsifiers for processing oils, antistatic agents (qv), softeners, and fiber lubricants, and as detergents in scouring operations. They also find appHcation as emulsifiers in cosmetic preparations and pesticide formulations. Eatty acid ethoxylates are manufactured either by alkaH-catalyzed reaction of fatty acids with ethylene oxide or by acid-catalyzed esterification of fatty acids with preformed poly(ethylene glycol). Deodorization steps are commonly incorporated into the manufacturing process. 

On the basis of bulk production (10), poly(ethylene terephthalate) manufacture is the most important ester producing process. This polymer is produced by either the direct esterification of terephthaHc acid and ethylene glycol, or by the transesterification of dimethyl terephthalate with ethylene glycol. In 1990, poly(ethylene terephthalate) manufacture exceeded 3.47 x 10 t/yr (see Polyesters). Dimethyl terephthalate is produced by the direct esterification of terephthaHc acid and methanol. 

Polyesters are the most important class of synthetic fibers. In general, polyesters are produced by an esterification reaction of a diol and a diacid. Carothers (1930) was the first to try to synthesize a polyester fiber by reacting an aliphatic diacid with a diol. The polymers were not suitable because of their low melting points. However, he was successful in preparing the first synthetic fiber (nylon 66). In 1946, Whinfield and Dickson prepared the first polyester polymer by using terephthalic acid (an aromatic diacid) and ethylene glycol. 

Using excess ethylene glycol is the usual practice because it drives the equilihrium to near completion and terminates the acid end groups. This results in a polymer with terminal -OH. When the free acid is used (esterification), the reaction is self catalyzed. However, an acid catalyst is used to compensate for the decrease in terephthalic acid as the esterification nears completion. In addition to the catalyst and terminator, other additives are used such as color improvers and dulling agents. For example, PET is delustred hy the addition of titanium dioxide. 

PET is the polyester of terephthalic acid and ethylene glycol. Polyesters are prepared by either direct esterification or transesterification reactions. In the direct esterification process, terephthalic acid is reacted with ethylene glycol to produce PET and water as a by-product. Transesterification involves the reaction of dimethyl terephthalate (DMT) with ethylene glycol in the presence of a catalyst (usually a metal carboxylate) to form bis(hydroxyethyl)terephthalate (BHET) and methyl alcohol as a by-product. In the second step of transesterification, BHET... 

Here the polymer grows by successive esterification with elimination of water and no termination step. Polymers formed by linking monomers with carboxylic acid groups and those that have alcohol groups are known as polyesters. Polymers of this type are widely used for the manufacture of artificial fibers. For example, the esterification of terephthalic acid with ethylene glycol produces polyethylene terephthalate. 

Furthermore, the role of a poly hydroxy alcohol, like ethylene glycol, seems ambiguous. As mentioned above, it is believed that the presence of ethylene glycol favours esterification of chelates. IR and NMR studies performed in [7] do not present solid proofs of such a belief. Synthetic routines with and without alcohols look the same, and the absence of alcohol seem not to influence the properties of precursors and final products. Some evidence exists enabling one to consider the esterification idea liable to more than one interpretation it has been reported in [4] that the presence of ethylene glycol does not influence the morphology of oxides. 

Krumpolc, M. and Malek, J., Esterification of benzenecarboxylic acids with ethylene glycol, IV. Kinetics of the initial stage of polyesterification of terephthalic acid with ethylene glycol catalyzed by zinc oxide, Makromol. Chem., 171, 69-81 (1973). 

Otton, J. and Ratton, S., Investigation of the formation of polyethylene terephthalate) with model molecules. IV. Catalysis of the esterification of ethylene glycol with benzoic acid and of the condensation of ethylene glycol monobenzoate,J. Polym. Sci., Polym. Chem. Ed., 29, 377-391 (1991). 

Bishydroxyethyl terephthalate (BHET) is the monomer used to make the PET polymer. BHET can be made either by the esterification of terephthalic acid (TPA) with ethylene glycol (EG) ... 

BHET formation is conducted at temperatures of 200 to 250 °C to achieve reasonable reaction rates. The activation energies of the two reactions are of the order of 25 000-30 000 cal/mol [4, 5], The BHET formation is usually conducted under pressure to keep the ethylene glycol in the liquid state. Terephthalic acid is slurried with ethylene glycol for the esterification reaction. Dimethyl terephthalate is dissolved in ethylene glycol and BHET for a liquid-phase transesterification reaction. The synthesis of BHET is driven to this material by the removal of water or methanol. The reactions are reversible at reasonable rates if the concentrations of water or methanol reactants are held high. 

In the case of the esterification of the diacid, the reaction is self-catalyzed as the terephthalic acid acts as its own acid catalyst. The reverse reaction, the formation of TPA and EG from BHET is catalytic with regard to the usual metal oxides used to make PET, but is enhanced by either the presence of hydroxyl groups or protons. In the case of transesterification of dimethyl terephthalate with ethylene glycol, the reaction is catalytic, with a metal oxide needed to bring the reaction rate to commercial potential. The catalysts used to produce BHET are the same as those needed to depolymerize both the polymer to BHET and BHET to its simpler esters. Typically, titanium, manganese and zinc oxides are used for catalysts. 

The important question of comparative value, mentioned earlier in Section 6, now must be considered. The material output of each process per unit of feed is estimated and multiplied by the market price of the material to arrive at a value of product. The output of the methanolysis processes, DMT and EG, are shown as a methanolysis-type product value in Table 16.5. The stoichiometric ratios are adjusted with a presumed 99 % recovery of DMT and 93 % recovery of EG. The output of the hydrolysis processes, TPA and EG, have the stoichiometric ratios adjusted for a presumed 99 % recovery of TPA and 93 % recovery of EG. The glycolysis processes, including methanolysis/BHET hybrid, are valued at 99 % recovery of terephthalic acid, 95 % recovery of ethylene glycol, and a US 0.022/kg esterification credit for making BHET. The EG recovery is higher for glycolysis-type products because of less loss of useful moieties. The three... 

Starting from the commercially available aldehyde (12), styrene (13) was prepared by a straightforward synthetic sequence (Scheme 11.3). Subsequent esterification of the phenol with succinate-derivatized poly(ethylene glycol) monomethyl ether (MeO-PEG) appended the styrene unit to approximately 50% of the free acid groups in (14). The loading in (15) was estimated by 500 MHz NMR spectroscopy to be about 0.1 mmol g . In a final step, the polymer-bound catalyst was ob-... 

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