Tetrahydrofuran, referred to as THF, is a liquid with an ether smell at room temperature. The molecular formula is (CH2)4O. Molecular weight 72.10. Melting point -108.5℃, boiling point 66℃, relative density d420 0.8892, refractive index nD25 1.4073, viscosity (2℃) 0.53mPa·s, flash point -17.2℃ (closed type), fire point 321℃. Soluble in water, alcohol, ketone, ether and hydrocarbon. Tetrahydrofuran can also generate peroxide after being left for a long time, so it needs to be checked and handled before use. To avoid explosions caused by peroxides, distillation should be carried out in the presence of reducing agents. Industrially, furan is catalytically hydrogenated to prepare 1,4-epoxybutane, so it is also called tetrahydrofuran. It is a widely used solvent with good solubility in organic synthesis. It is also a raw material for the synthesis of nylon, butadiene, adipic acid, adiponitrile, hexamethylenediamine, etc.
Tetrahydrofuran is a compound that has long been known. It was first produced by the furfural method using furfural as the raw material, and later changed to the Rapa method using acetylene as the raw material. The purpose of THF is to use it to resins, organic Good solubility, rapid diffusibility and evaporation of compounds and inorganic compounds, or used as synthetic raw materials; or used in coatings, adhesives, printing inks, film forming, low-temperature detergents, extraction solvents, synthetic raw materials, odors agents, etc. Its main demand is to be used as a solvent, and polyurethane and vinyl chloride artificial leather surface coating solutions account for most of the usage. An example of its use as a synthetic raw material is as a raw material for polytetramethylene glycol (PTMG). Polyurethane resin can be produced from the latter. Tetrahydrothiophene, produced by the reaction of THF and hydrogen sulfide, is used as an odorant for city gas.
Uses of Tetrahydrofuran
Tetrahydrofuran is used in Grignard reactions, polymerization reactions, reduction reactions with lithium aluminum hydride, and condensation Excellent solvent in reactions and esterification reactions. It has a fast dissolution speed and good penetration and diffusion properties on the surface and interior of the resin, so it is widely used. Use it to dissolve polyvinyl chloride, polyvinylidene chloride and other copolymers to obtain a low-viscosity solution, which can be used in the manufacture of surface protective coatings, adhesives and films. It can also be used for the preparation of inks and paint stripping. Agents, extraction agents and artificial leather surface treatment agents, etc. In the presence of zinc chloride, it reacts with acid or acid chloride to easily open the ring and generate 1,4-butanediol and 1,4-dichlorobutane. Heating with hydrogen chloride gas can produce 4-chloro-1-butanol. Tetrahydrofuran can also be used as a raw material for the synthesis of butadiene, nylon, polybutylene glycol ether, γ-butyrolactone, polyvinylpyrrolidone, tetrahydrothiophene, etc.
1. Raw materials for spandex synthesis reaction
THF itself can be polycondensed (ring-opening repolymerization initiated by cations) into polytetramethylene ether glycol (PTMEG), also known as tetrahydrofuran homopolyether. PTMEG is combined with toluene diisocyanate (TDI) to make a special rubber with wear resistance, oil resistance, low temperature performance and high strength; it is made with dimethyl terephthalate and 1,4-butanediol to make block polyether polyester elasticity Material. PTMEG with a relative molecular mass of 2000 and p-methylene bis (4-phenyl) diisocyanate (MDI) are used to make polyurethane elastic fibers (spandex, SPANDEX fibers), special rubber and some special-purpose coatings.
The most important use of THF is to produce PTMEG. According to rough statistics, more than 80% of the world’s THF is used to produce PTMEG, and PTMEG is mainly used to produce elastic spandex fiber.
2. Solvent with excellent performance
THF is especially suitable for dissolving PVC, polyvinylidene chloride and butylaniline. It is widely used as a solvent for surface coatings, anti-corrosion coatings, printing inks, tapes and film coatings. When electroplating aluminum liquid, the thickness and brightness of the aluminum layer can be controlled arbitrarily. Tape coating, PVC surface coating, cleaning PVC reactor, removing PVC film, cellophane coating, plastic printing ink, thermoplastic polyurethane coating, adhesive solvent, THF tetrahydrofuran is commonly used in surface coatings, protective coatings, Inks, extractants and surface treatments for synthetic leather.
3. Used as a raw material for organic synthesis in pharmaceuticals and other industries, for the production of tetrahydrothiophene, 1.4-dichloroethane, 2.3-dichlorotetrahydrofuran, valerolactone, butyrolactone and pyrrolidone, etc. In the pharmaceutical industry, THF is used to synthesize Kebiqing, rifumycin, progesterone and some hormone drugs. THF is treated with hydrogen sulfide to form tetrahydrothiophenol, which can be used as an odorant (identification additive) in fuel gas and is also the main solvent in the pharmaceutical industry.
Tetrahydrofuran toxicity and hygiene
Tetrahydrofuran is a highly toxic substance. The 24h inhalation LC for mice is 90.2 mg/L; the oral LD for rats is 3.2 to 3.6 mg/kg. Has anesthetic effect. Irritating to eyes and respiratory mucosa. Animal experiments show kidney inflammation and liver damage.
GB 9685-2008 stipulates that (1) the maximum usage amount in paper is 4.0%; in coatings and adhesives, it should be used in appropriate amounts according to production needs; (2) the maximum limit of specific migration level (SML) is 0.6mg /kg.
Health hazards of tetrahydrofuran
It is a flammable liquid with low boiling point and flash point. It is easy to catch fire at room temperature. It must be kept away from fire sources when used. It has an irritating effect on the skin and mucous membranes of the eyes, nose, and tongue. Its vapor is anesthetic. Inhaling high-concentration vapor for a long time can cause dizziness, dizziness, headache, vomiting, etc. when it’s in blood
When the concentration in the solution reaches 160 mg%, it will cause complete anesthesia.
Reaching 300 mg% can cause death. However, the pure product is less toxic than acetone and is one of the least toxic solvents. The maximum allowable concentration in the workplace is 200ppm, and its smell can be smelled when it is greater than 25-50ppm. There is no danger in general use. Should be stored in a cool, ventilated and dry place.
Preparation method:
①Tetrahydrofuran can be produced by using furan as raw material and nickel as catalyst by hydrogenating 80 to 1 barium carbonate at 50°C.
② Use tetrahydrofurfuryl alcohol as raw material, dehydrogenate under the action of catalyst to generate furfural, and then follow method ③ to obtain it.
③ Use furfural as raw material, mix it with water vapor at high temperature, pass through the zinc-chromium-manganese catalyst bed, decarbonylate at ℃, and then hydrogenate at 80-100℃ using nickel as the catalyst , can be obtained.
④ Use acetylene as raw material, add it with formaldehyde to generate 2-butyne-1,4-diol, hydrogenate it to generate 1,4-butanediol, and dehydrate in the presence of sulfuric acid, it can be produced [1]. CH≡CH+2HCHO→HOCH2C≡CCH2OH
HOCH2CH2CH2CH2OH→[1]+H2O
⑤ Use maleic anhydride as raw material and hydrogenate under the action of catalyst to generate butyric anhydride. Continue hydrogenation to be made of.
⑥ Use 1,4-dichloro-2-butene as raw material, hydrolyze it in sodium hydroxide solution to generate 2-butene-1,4-diol, and hydrogenate it under the action of nickel catalyst to generate 1,4-butanediol can be obtained by dehydration in the presence of a dehydrating agent.
⑦ Use 1,3-butadiene, acetic acid and air as raw materials, react under the action of palladium catalyst at 80℃ and 3.0MPa to generate 1,4-diacetyl-2 anhydrous lithium tetraborate -Butene, then hydrogenated under the action of nickel-zinc catalyst at 80°C and 8.11MPa to generate 1,4-diacetylbutane, hydrolyzed to generate 1-hydroxy-4-acetylbutane, and decarboxylated Cyclization can be obtained.
⑧ It can be produced by using 1,4-butanediol as raw material, using heteropoly acid as catalyst, and dehydrating at 120~130℃.
Tetrahydrofuran manufacturers
At present, the main domestic manufacturers of tetrahydrofuran (THF) mainly include BASF China, Dalian Yizheng (DCJ), Shanxi Sanwei, and Sinochem International, PetroChina Qianguo Refinery, etc., and some other PBT factories also produce a part of tetrahydrofuran (THF) by-product. The THF sales indicators of LyondellBasell Industrial Company in the United States and Europe are: purity 99.90%, color (APHA) 10, moisture 0.03%, THF hydroperoxide 0.005%, total impurities 0.05%, oxidation inhibitor 0.025% ~ 0.035 %.
Notes on Tetrahydrofuran
Tetrahydrofuran is a saturated cyclic ether composed of four carbon atoms. Molecular formula C4H8O, colorless and transparent liquid, boiling point 66°C, melting point -108.5°C, relative density 0.889 2 (24/4°C), refractive index 1. 403 3 (20°C). Mixing with air will form explosive gas, with an explosion limit of 2.3 to 11.8. It is miscible with water and compatible with general organic solvents (ethanol, ether, aliphatic hydrocarbons, halogenated hydrocarbons, etc.) and is an excellent solvent. It is usually produced by dehydration of 1,4-butanediol or hydrogenation of furan. Long-term contact with air will cause auto-oxidation and generate explosive peroxides. Before being used as a solvent for chemical reactions, it must be pretreated to remove possible peroxides or antioxidants added to prevent auto-oxidation. Before pretreatment distillation or heating, check whether there is peroxide with 2% acidic potassium iodide solution, wash with a mixed aqueous solution of ferrous sulfate and sulfuric acid, or reflux with lithium aluminum hydride before distilling to remove water and peroxide. substances, antioxidants and other impurities.
