Terephthalic acid (TPA) 100-21-0
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Terephthalic acid is an organic compound with the chemical formula C6H4(COOH)2. The colorless solid is a commodity chemical primarily used as a precursor to the polyester PET used to make clothing and plastic bottles. Millions of tons are produced every year. It is one of three isomeric phthalic acids.
| describe | Terephthalic acid is an organic compound with the chemical formula C6H4 ( COOH) 2 . The colorless solid is a commodity chemical primarily used as a precursor to the polyester PET used to make clothing and plastic bottles. Millions of tons are produced every year. It is one of three isomeric phthalic acids. |
| chemical properties | Terephthalic acid is a white crystalline solid. It is easily soluble in alkaline solution, slightly soluble in hot ethanol, and insoluble in water, ether, glacial acetic acid and chloroform. Therefore, until around 1970, most of the crude terephthalic acid was converted into dimethyl ester for purification. It sublimates when heated. |
| history | Terephthalic acid came to attention around 1940 from the work of Winfield and Dickson in England. Early work by Carothers and colleagues in the United States established the feasibility of producing high molecular weight linear polyesters by reacting diacids with diols, but they used aliphatic diacids and diols. These made polyesters are not suitable for spinning into fibers. Winfield and Dickson discovered that symmetric aromatic diacids produced high-melting, crystalline, and fiber-forming materials; polyethylene terephthalate (PET) has since become the most produced synthetic fiber. |
| application | 1,4-phthalic acid is mainly used in the production of polyethylene terephthalate. It also produces the plasticizer dioctyl phthalate (DOTP) and polyester plasticizers. 1,4-phthalic acid undergoes a condensation reaction with polyols to prepare polyester plasticizers with diethylene glycol, triethylene glycol, glycerol, propylene glycol, butylene glycol, etc. |
| use | Terephthalic acid (TPA) is a benzene polycarboxylic acid with potential antihemorrhagic properties. It is a high-tonnage chemical used extensively in the production of synthetic materials, particularly polyester fibers (polyethylene terephthalate). |
| Prepare | The main commercial route to terephthalic acid suitable for direct preparation of polyethylene terephthalate starts from p-xylene:
Paraxylene is primarily obtained from petroleum sources and is a product of the fractionation of reformed naphtha. Oxidation takes place in the liquid phase. Typically, air is passed into a solution of p-xylene acetic acid at about 200°C. In the presence of a catalyst system containing cobalt and manganese salts and a source of bromide ions, the pressure is 2MPa (20 atmospheres). The terephthalic acid produced contains only small amounts of impurities (mainly p-carboxybenzaldehyde) and can be easily removed. The acid is dissolved in water at about 2500 e and 5 MPa (50 atmospheres) and treated with hydrogen (converting the aldehyde to p-toluic acid). The solution was then cooled to 100°C? Pure terephthalic acid crystals. |
| definition | ChEBI: Terephthalic acid is a phthalic acid with carboxyl groups in the 1 and 4 positions. One of three possible isomers of phthalic acid, the others being phthalic acid and isophthalic acid. It is the conjugate acid of terephthalate (1-). |
| synthesis | Benzoic acid, phthalic acid and other benzenecarboxylic acids in the form of alkali metal salts constitute the starting material. In the first step, the alkali metal salt (usually potassium) is converted to terephthalate when heated to temperatures above 350 °C (662 °F). A dry potassium salt (benzoic acid or phthalic acid or isophthalic acid) is heated in anhydrous form in the presence of an inert atmosphere (CO2) and a catalyst (usually cadmium benzoate, cadmium phthalate) to about 420 °C (788 °F), oxides or carbonates). Corresponding zinc compounds have also been used as catalysts. In the next step, the reaction product was dissolved in water and terephthalic acid was precipitated with dilute sulfuric acid. The yield of terephthalic acid ranges from 95% to 98%. |
| application | In fact, the worldwide supply of terephthalic acid and dimethyl terephthalate is consumed as a precursor to polyethylene terephthalate (PET). World production in 1970 was approximately 1.75 million tons. By 2006, the global demand for purified terephthalic acid (PTA) had exceeded 30 million tons. The demand for terephthalic acid is small but still important in the production of polybutylene terephthalate and several other engineering polymers. |
| production method | Terephthalic acid is produced by the oxidation of paraxylene with oxygen in the air: the reaction proceeds through the paratoluic acid intermediate, which is then oxidized to terephthalic acid. In p-toluic acid, the electron-withdrawing carboxylic acid group deactivates the methyl group, making it only one-tenth as reactive as xylene itself, making the second oxidation more difficult. This commercial process uses acetic acid as solvent and a catalyst consisting of cobalt and manganese salts and a bromide promoter. |
| synthetic references | Chemistry Letters, 15, p. 299, Journal of the American Chemical Society 1986 , 82, p. 14. 2876, 1960 DOI: 10.1021/ja01496a051 Journal of Organic Chemistry, 44, p. 4727, 1979 DOI: 10.1021/jo00393a063 |
| general instructions | White powder. |
| air and water reaction | Insoluble in water. |
| reactive profile | Terephthalic acid is a carboxylic acid. If there is a base that accepts hydrogen ions, terephthalic acid releases hydrogen ions. This "neutralization" generates large amounts of heat and produces water and salt. Carboxylic acids are insoluble in water, but even "insoluble" carboxylic acids can absorb enough water from the air and dissolve sufficiently in terephthalic acid to corrode or dissolve iron, steel, and aluminum parts and containers. May react with cyanide salts to form gaseous hydrogen cyanide. Reacts with cyanide solution to release gaseous hydrogen cyanide. Reactions with diazo compounds, dithiocarbamates, isocyanates, mercaptans, nitrogen compounds and sulfides may produce flammable and/or toxic gases and heat. Reacts with sulfites, nitrites, thiosulfates (generating H2S and SO3), dithionite (SO2) to produce flammable and/or toxic gases and heat. Reaction with carbonates and bicarbonates produces a harmless gas (carbon dioxide), but heat is still produced. It can be oxidized by strong oxidizing agents and reduced by strong reducing agents. These reactions generate heat. May initiate polymerization; may catalyze (increase) the rate of chemical reactions. |
| fire hazard | There are no flash point data for terephthalic acid. Terephthalic acid may be flammable. |
| Flammability and explosiveness | non-flammable |
| Security overview | The intravenous and intraperitoneal routes are moderately toxic. Mildly toxic if swallowed. Irritating to eyes and may explode during preparation. When heated and decomposed, acrid and irritating fumes are released. |
| potential contact | TPA is primarily used in the production of polyethylene terephthalate polymer, which is used to make polyester fibers and films. A mass-produced chemical in the United States. |
| Purification method | The acid is purified by the sodium salt which, after crystallization from water, is reconverted to the acid by acidification with a mineral acid. The solid was filtered off, washed with water and dried in vacuo. S-benzylisothiouronium salt has m 204o (from aq. EtOH). [Beilstein 9 IV 3301. ] |
| Incompatibility | Flammable; dust may form explosive mixtures with air. Carboxyl compounds react with all bases, inorganic and organic (i.e. amines), releasing large amounts of heat, water and potentially harmful salts. With arsenic compounds (releases hydrogen cyanide gas), diazo compounds, dithiocarbamates, isocyanates, thiols, nitrogen compounds and sulfides (releases heat, toxic and possibly flammable gases), thio Sulfates and dithionites (releasing hydrogen sulfate and sulfur oxides) are incompatible. Incompatible with oxidizing agents (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fire or explosion. Keep away from alkaline substances, strong bases, strong acids, oxo acids, epoxides. |
| waste disposal | The material is dissolved or mixed with a flammable solvent and burned in a chemical incinerator equipped with an afterburner and scrubber. All federal, state and local environmental regulations must be followed. |
| Upstream and downstream product information of terephthalic acid |
| raw material | Acetic acid --> p-xylene -- > bromide -- > cobalt acetate --> manganese triacetate dihydrate --> paraldehyde --> manganese (II) acetate --> 1,1,2, 2-Tetrabromoethane --> 4- formylbenzoic acid--> p -Toluic acid-->terephthalaldehyde -- > 1,4-dibromobenzene --> [4-(hydroxymethyl ) cyclohexyl] methanol |
| Preparation products | Pigment Red 122 --> Triethylene glycol dimethacrylate --> Unsaturated polyester resin --> Dimethyl terephthalate --> Polybutylene terephthalate --> Paraphenylene Diformyl chloride --> Luminol --> Tassah silk fabric finishing agent --> Polyethylene terephthalate --> Dioctyl terephthalate --> Liquid crystal heterocyclic polymer-- > Auxiliary chrome tanning agent --> 1,4-bis(trifluoromethyl)-benzene --> 1,4-bis(pentafluorophenyl)phthalate |
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