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Furfural, also known as 2-furfuraldehyde, is the same substance as glycoaldehydes. Its scientific name is α-furaldehyde, which is a derivative of hydrogen atom substituted by aldehyde group on furan 2 site. It is originally made from rice bran coheated with dilute acid, so it is called furfural. Furfural is hydrolyzed by pentosan in the presence of acid to produce pentose, which is then dehydrated and cyclized. Production of the main raw materials for corn cobs and other agricultural and sideline products. There are many ways to synthesize them. Furfural is a derivative of furan ring system with active chemical properties. It can be prepared by oxidation, condensation and other reactions, and is widely used in synthetic plastics, medicine, pesticide and other industries.
Furfuryl alcohol is colorless or light yellow transparent liquid; Taste slightly pungent, miscible with water, but unstable in water; It is easily soluble in alcohols, ethers and other organic solvents, but insoluble in paraffin hydrocarbons. Furfuryl alcohol is easy to resinize when it meets acid. When stored in the air, the color becomes darker due to condensation.
Furfuryl alcohol is mainly used to produce furan resin, which can be used as the sand core adhesive for the hot core box of precision casting industry and other organic materials. The furan resin has attracted people's attention for its outstanding corrosion resistance and heat resistance, as well as its common source of raw materials and simple production process. After the mid-1970s, due to the breakthrough of synthesis technology and catalyst application technology, furan resin has been largely overcome the above shortcomings, and it has made great progress in the field of corrosion prevention, and began to be used in the manufacture of corrosion resistant FRP. At present, the application amount of furan resin in the field of anti-corrosion has exceeded the amount of traditional phenolic resin, especially in some high temperature, corrosive environment, it plays a great role.
At present, there are more than 20 kinds of furan resins produced at home and abroad, most of which are directly synthesized from furfural and furfuryl alcohol. Scientific and technical workers in the Soviet Union have done a lot of research work on furfural as the raw material of furan resin, which has been successfully applied in various aspects of the anti-corrosion field, among which the representative product is furfural ketone resin. Furfural and acetone are condensed to furfuryl acetone under the action of alkaline catalyst. Under the action of acid catalyst, the furfuryl acetone and difurfuryl acetone generated by the reaction can be polymerized to obtain brown black viscous liquid resin.
Chemical properties :
Because furfural has aldehyde group and dienyl ether functional group, furfural has the properties of aldehyde, ether, diolefin and other compounds, especially similar to benzaldehyde. Under certain conditions, furfural can undergo the following chemical reactions: Furfural is oxidized to produce maleic acid, maleic anhydride, furfuric acid and furanic acid. In the gas phase, the furfural was oxidized by catalyst to produce dehydrated malic acid. Furfural hydrogenation can produce furfuryl alcohol, tetrahydrofurfuryl alcohol, methyl furan, methyl tetrahydrofuran. Furan can be prepared by decarbonization of furfural steam and water steam with suitable catalyst. Under the action of strong alkali, furfural can produce furfuryl alcohol and sodium furfurate by Conicaro reaction. Furfural can be in the action of fatty acid salt or organic base Bergin reaction, with anhydride condensation to produce furan acrylic acid. Furfural is condensed with phenolic compounds to form thermoplastic resin. Condensation with urea, melamine manufacturing plastics; Furfuryl ketone resin was prepared by condensation with acetone.
The development course
Furfural was first discovered by Doebernier in 1821. Subsequently, the physical and chemical properties and their synthesis methods have been studied deeply. In 1922, Quakeroats Company in the United States first realized the industrialization of furfural, mainly used in the decolorization of wood rosin and lubricating oil refining, realizing the application of furfural in the industrial field; In the 1940s, furfural was widely used in synthetic rubber, medicine, pesticide and other fields. After 1960s, with the development of furfural derivatives, especially the widespread application of furan resin in foundry industry, furfural industry has been greatly promoted.
Furfural is a colorless and transparent oily liquid, also known as furaldehyde, which is generated by the hydrolysis and dehydration of pentosan in plant fiber raw materials. It has a special fragrance. Under the action of light, heat, air oxidation and inorganic acid, the color will quickly change to yellowish-brown and eventually black brown, and it is easy to polymerize and become resinous. Storage should be kept away from light, oxygen removal and sealed. Furfural is partially soluble with water, but also soluble in alcohol, ether, acetic acid and other solvents. The ability to dissolve aromatics, olefin, polar matter and some macromolecular compounds is large, while the ability to dissolve saturated substances such as aliphatic hydrocarbons and high fatty acids is small. Various derivatives can be produced by oxidation, hydrogenation, nitrification, oxidation, decarbonylation, condensation and other reactions. Very similar to the properties of benzaldehyde, benzoin reaction, pulkin reaction and canicharo reaction can occur. Furfural reacts bright red with aniline glacial acetic acid solution, which is often used as a qualitative reactant for furfural.
The quantitative analysis was based on the two properties of aldehyde group and furan ring. In addition to chromatography, there were volumetric methods (hydroxyamine hydrochloride method, tetrabromination method, etc.) and gravimetric methods (phloroglucinol method, barbituric acid method, etc.) for the analysis of finished products. In China, hydroxylamine hydrochloride method was used for the analysis of finished products. Furfural is often used as a solvent for refining petroleum, an important raw material for synthesizing resins, electrical insulating materials, nylon, coatings, etc., and a raw material and reagent for making drugs and a variety of organic synthesis. Mainly used for production of furan derivatives objects (e.g., furfuryl alcohol, four hydrogen furfuryl alcohol, methyl furan, preparing furan through decarbonylation, oxidation of furoic acid and nitrofurans drug, etc.) of the raw material, also used as a separation of saturated aliphatic compounds (such as oil lubricating oil, gasoline, kerosene, and vegetable oil) of unsaturated compounds in selective solvents, petroleum and rosin resin production of solvent, And separation of butadiene and other extractive distillation solvents from C4 distillate. The resins made of furfural and furfuryl alcohol (such as furfuryl alcohol resins, furfuryl ketone resins, etc.) are collectively called furan resins, which are mainly used as foundry resins, grinding wheel adhesives and anticorrosive coatings.
As a raw material for organic synthesis, also used in synthetic resins, varnishes, pesticides, pharmaceuticals, rubber and coatings; Mainly used as industrial solvent, used for making furfuryl alcohol, furfuric acid, tetrahydrofuran, γ-valerolactone, pyrrole, tetrahydropyrrole, etc.; Used as an analytical reagent; Used for tanning face leather. It should be stored in a cool and ventilated warehouse, kept away from sunlight, and kept away from fire. Furfural is the raw material of furfuryl acrylic acid, furfuryl amine fumaric acid, adipic acid, furfuryl alcohol and other intermediates, widely used in the synthesis of pharmaceutical, pesticide, veterinary drugs, dyes, spices, rubber additives, preservatives and other fine chemicals. The largest area of consumption of furfural is as a solvent and raw material for synthetic resins. Used in synthetic resin, can produce furan resin, furfural resin and furfuryl ketone resin and so on. Furfuran resin is also called furfuryl alcohol resin. Furfural is hydrogenated to furfuryl alcohol under high pressure, and furfuryl alcohol is polymerized to get furfuryl alcohol resin. This resin has strong alkaline resistance, high heat resistance and water resistance, can be used as sealant resin cement, anticorrosive lining, binder. Furfural, as a solvent, can selectively extract unsaturated components from petroleum and vegetable oils.
Fragrant components in lubricating oil and diesel oil were extracted by furfural. Improve the quality of these products. In the production of synthetic rubber, butadiene and isoprene were purified by furfural extraction. Furfural can irritate the skin and mucous membranes, and the maximum allowable concentration in the air is 5 parts per million. The oral dose of LD50 was 127mg/kg in rats. ; Flavors for food as permitted in GB 2760 -- 96; Extraction solvent. Mainly used for the preparation of various hot processing flavors, such as bread, hard cream candy, coffee and other flavors. Furfural is an important organic chemical raw materials, can be used to produce maleic anhydride, glycol, furfural alcohol, tetrahydrofuran, can also be used to synthesize furfural resin, furan resin, rubber vulcanization accelerator, rubber and plastic anti-aging agent, preservatives, etc.. It is mainly used in medicine, pesticide, veterinary medicine and food industry