Industrial preparation terephthalic acid

A similar oxidation is employed industrially for the preparation of the terephthalic acid used in the production of polyester fibers. Approximately 5 million tons per year of p-xylene are oxidized, using air as the oxidant and Co(lll) salts as catalyst. 

POLYESTER FIBERS. The principal characteristics of these fibers are described in the endy on Fibers. Polyester fibers are defined as synthetic fibers containing at least 80% of a long-chain polymer compound of an ester of a dihydric alcohol and terephthalic acid. T he first polyester fiber to be commercialized was prepared from the ester in which the dihydric alcohol was ethylene glycol this fiber is the material used in the largest quantity bv the textile industry. For some other commercial uses, the ester 1,4-dimethyldicyclohexyl terephthalate is also used... 

The nomenclature of esters is relatively simple, because it is similar to the nomenclature of salts. For instance, the ester obtained from methanol and ethanoic acid (acetic acid) is called methyl ethanoate (methyl acetate). Esters are compounds that comprise a large number of structures depending on what the alcohol and acid components are. Esters with a small molecular mass are volatile substances, in most cases with a pleasant odor. For instance, butyl acetate is responsible for the odor of apples. In nature, some esters serve as pheromones for insects, for example isoamyl acetate which attracts butterflies. Other kinds of esters can be large molecules as for instanee waxes and fats where both the alcohol and the acid components can be long-ehained or eomplicated structures. These natural esters will be diseussed in the ehapter on lipids. In industry, esters are used in the fabrication of polymeric fibers for textile materials and plastic materials for various uses. The most common material is polyethylene terephthalate (PET), the ester prepared from terephthalic acid and ethylene glycol. 

The amoxidation of propylene is an important industrial process of acrylonitrile synthesis. One of the methods of acrylonitrile synthesis involves the reaction of propylene with ammonia and oxygen in the presence of a heterogeneous catalyst (bismuth molybdate containing compounds of Ni, Co, Fe, Sn, etc.) " " see equation (13.249). The amoxidation process is also carried out in the case of other compounds, for instance, 3-methylpyridine and / -xylene, which allows the preparation of nicotinic and terephthalic acids, respectively, after hydrolysis of the nitriles. 

For example, the polyamide prepared from the condensation of terephthalic acid with a mixture of 2,2,4- and 2,4,4-trimethylhexamethylenediamines (PA6-3-T) was developed at W.R. Grace and Company, later produced under license by Dynamit Nobel AG, and currently available from Evonik Industries... 

The PEE preparation by polycondensation of terephthalic acid (TA), BD, and PTMEG has been given little attention by the industry. The situation is similar to the case of the preparation of PBT by a TA process in which the formation of tetrahydrofuran (THE) by cyclization is a serious problem [133,155]. This situation can be schematically summarized as follows (Schemes 6 8) ... 

Methyl benzoate, [93-58-3], CTfCOOCI Ig, bp, 198—200°C at 101.3 kPa d [ , 1.094 n], 1.5205. Insoluble in water, this is a colorless, transparent liquid solidifying at about 15°C. Methyl benzoate is prepared by the direct esterification of benzoic acid and methanol. It is used in the fragrance industry and in the production of other benzoate esters (via transesterification). A technical-grade methyl benzoate is available as a by-product in the manufacture of dimethyl terephthalate [120-61 -6]. 

The saturated polyesters that find conunercial applications are mostly linear, except for some specially prepared branched polymers used in the preparation of polyurethanes. The linear polyesters became commercially important materials early in this century and still find many uses in industry. The earliest studies reported condensations of ethylene, trimethylene, hexamethylene, and de-camethylene glycols with malonic, succinic, adipic, sebacic, and orthophthalic acids. Later studies showed that such condensations yield high molecular weight compounds. Nevertheless, these polyesters exhibit poor hydrolytic stability and are generally low-melting. Subsequently, however, it was found that aromatic dicarboxylic acids yield polymers with high melting points, and poly(ethylene terephthalate), which melts at 265 C, is now an important commercial material. 

P, and Pivsa-Art, S. (2011) Preparation of polymer blends between poly (L-lactic acid), poly (butylene succinate-co-adipate) and poly (butylene adipate-co-terephthalate) for blow film industrial application. Energy Procedia, 9, 581-588. 

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