Structural formula
| Business number | 0131 |
|---|---|
| Molecular formula | CH2O |
| Molecular weight | 30.03 |
| label |
formalin, Formic aldehyde, methylene oxide, Methyl aldehyd, Methylene oxide, Formalin, Formallydehyde, Methanal solution, Oxymethylene, Dormol, pesticide intermediates, Aliphatic aldehydes, ketones and their derivatives, organic compounds |
Numbering system
CAS number:50-00-0
MDL number:MFCD00003274
EINECS number:200-001-8
RTECS number:LP8925000
BRN number:1209228
PubChem number:24894976
Physical property data
1. Characteristics: A colorless gas with a strong irritating and suffocating odor.
2. Relative density of steam (g/mL, air=1): 1.081-1.085
3. Relative density (g/mL, water=1): 0.82
4.Refractive index (nD20): 1.3755-1.3775
5. Flash point (℃): 56 (gas); 83 (37% aqueous solution, closed cup)
6. Boiling point (℃): -19.5 (gas); 98 (37% aqueous solution)
7. Melting point (℃): -92
8. Auto-ignition temperature (℃): 430
9. Vapor pressure (KPa,-57.3℃): 13.33
10. Explosion limit (V/V): 7%~73% in air
11. Logarithmic value (logP) of oil-water (octanol/water) partition coefficient: 0.35
12. Critical temperature (ºC): 137.2~141.2
13. Critical pressure (MPa): 6.784~6.637
14. Viscosity (mPa·s,-20ºC): 0.242
15. Lower explosion limit (%, V/V): 7.0
16. Explosion upper limit (%, V/V): 73
17. Solubility: Easily soluble in water and ether. The aqueous solution concentration can reach up to 55%. It can be freely miscible with water, ethanol and acetone. It can be gradually oxidized into formic acid in the air and is a strong reducing agent. Its vapor forms an explosive mixture with air, which can cause combustion and explosion when exposed to open flames or high heat. In general products, 10% to 12% methanol is added as an inhibitor, otherwise polymerization will occur.
18. Gas phase standard combustion heat (enthalpy) (kJ·mol-1): -570.77
19. Gas phase standard claims heat (enthalpy) (kJ·mol-1): -108.57
20. Gas phase standard entropy (J·mol-1·K-1): 218.76
21. Gas phase standard formation free energy (kJ·mol-1): -102.5
22. Gas phase standard hot melt (J·mol-1·K-1): 35.39
Toxicological data
1. Acute toxicity: LD50800mg/kg (rat oral), 2700mg/kg (rabbit transdermal); LC50590mg/m3 (rat inhalation);
People inhaling 60 ~ 120 mg/m3 will cause bronchitis and serious lung damage;
If a person inhales 12~24mg/m3, the mucosa of the nose and throat will be severely burned, with tears and coughing; if a person takes 10~20ml orally, it will cause death.
2. Subacute and chronic toxicity: Rats inhaled 50~70mg/m3, 1 hour/day, 3 days/week, 35 weeks, and hyperplasia and biochemical changes of tracheal and bronchial basal cells were found;
People who inhale 20~70mg/m3 for a long time will suffer from loss of appetite, weight loss, weakness, headache, and insomnia;
People who inhale 12mg/m3 for long-term exposure will experience drowsiness, weakness, headache, finger tremors, and vision loss.
3. Mutagenicity: Microbial mutagenicity: Salmonella typhimurium 4mg/L. Mammalian somatic mutations: human lymphocytes 130umol/L. Sister chromosome exchange: 37 pph in human lymphocytes.
4. Reproductive toxicity: The lowest oral toxic dose in rats (TDL0): 200mg/kg (1 day, male), has an impact on sperm survival. The lowest toxic concentration for rats to inhale (TCL0): 12ug/m3, 24 hours (pregnancy day 1 to 22), causing biochemical and metabolic changes in newborn rats.
5. Carcinogenicity: IARC carcinogenicity comment: positive in animals; unclear in humans.
6. Formaldehyde is highly irritating to the eyes, respiratory tract and skin. Exposure to formaldehyde vapor can cause conjunctivitis, keratitis, rhinitis, bronchitis, etc. Laryngeal spasm, glottis edema, pneumonia, and pulmonary edema occur mainly. It has primary irritation and sensitization effects on the skin. Can cause dermatitis. Concentrated solutions can cause coagulative necrosis of the skin. Oral administration burns the mouth and digestive tract, and may cause gastrointestinal perforation, shock, and liver and kidney damage. Long-term exposure to low concentrations of formaldehyde may cause mild eye and upper respiratory tract irritation, dry and chapped skin. The maximum allowable concentration of toxic substances in the air in the workplace is 0.5mg/m3.
Ecological data
1. Metabolism and degradation: The main source of formaldehyde pollution in the environment is wastewater and waste gas discharged from industries such as organic synthesis, chemical industry, synthetic fibers, dyes, wood processing, and paint making. The degradation of certain organic compounds in the environment also produces formaldehyde. For example, the degradation products of vinyl chloride also contain formaldehyde. Since formaldehyde has strong reducing properties, it can be oxidized to formic acid in the presence of oxidizing substances. For example, formaldehyde entering the water environment can be oxidized and decomposed by saprophytic bacteria, thus consuming dissolved oxygen in the water. The further decomposition products of formic acid are carbon dioxide and water. Formaldehyde entering the environment is gradually diluted, oxidized and degraded under the combined effects of physics, chemistry and biology. The oxidative degradation process of formaldehyde is as follows: 2HCHO+O2—2HCOOH 2HCOOH+O2—2H2O+2CO2
2. Residue and accumulation: According to data, the formaldehyde content adsorbed in the soil of industrial enterprise areas can reach 180-720mg/kg dry soil. Soil pollution can lead to groundwater pollution, and the formaldehyde content in the water can be 10-20 times higher than that in the topsoil.
Formaldehyde is quite stable in the environment. When the formaldehyde concentration in water is 5 mg/L (20°C), observation results show that it can remain constant within 5 days. When the concentration of formaldehyde in water is <20 mg/L, it can be degraded and digested by domesticated microorganisms in the aeration tank. When the content is 100mg/L, it can inhibit the oxidation of organic matter by microorganisms. When the formaldehyde content in the water is 500mg/L, all biological oxygen consumption processes are stopped and microorganisms in the water are killed.
3. Migration and transformation: Because formaldehyde has a low boiling point and is easily soluble in water, it mainly enters the environment through atmospheric and water emissions. For untreated gas from a factory that produces formaldehyde, when the emission height is 18 meters, the formaldehyde content in air samples 250-500 meters away from the factory is above 0.035 mg/m3. At a distance of 1,000 meters, the concentration of formaldehyde in the atmosphere is below the olfactory threshold. The concentration of formaldehyde in the atmosphere around companies that use formaldehyde as a tanning agent to produce plastics is below the olfactory threshold. The formaldehyde concentration in the atmosphere around a company that uses formaldehyde as a tanning agent to produce plastics is 0.012mg/m3 within 100 meters from the factory; 15 of the 36 samples at 200 meters have concentrations lower than 0.012mg/m3; and 400 meters away are all lower than 0.012 mg/m3.
The formaldehyde content discharged in industrial wastewater varies greatly depending on the industry. The formaldehyde wastewater with the highest concentration is the upper tar wastewater from the production of phenolic resin, which contains up to 2.5% formaldehyde.
4. Hazardous characteristics: Its vapor and air form an explosive mixture, which can cause combustion and explosion when exposed to open flames or high heat. If exposed to high heat, the internal pressure of the container will increase and there is a risk of cracking and explosion.
Combustion (decomposition) products: carbon monoxide, carbon dioxide.
Molecular structure data
1. Molar refractive index: 6.53
2. Molar volume (cm3/mol): 43.8
3. Isotonic specific volume (90.2K): 82.6
4. Surface tension (dyne/cm): 12.6
5. Dipole moment (D): 2.33168 (1D=3.33×10-30C·m)
6. Polarizability (10-24cm3): 2.59
Compute chemical data
1. Reference value for hydrophobic parameter calculation (XlogP): 1.2
2. Number of hydrogen bond donors: 0
3. Number of hydrogen bond acceptors: 1
4. Number of rotatable chemical bonds: 0
5. Number of tautomers: None
6. Topological molecules��Plastic surface area 17.1
7. Number of heavy atoms: 2
8. Surface charge: 0
9. Complexity: 2
10. Number of isotope atoms: 0
11. Determine the number of atomic stereocenters: 0
12. Number of uncertain atomic stereocenters: 0
13. Determine the number of stereocenters of chemical bonds: 0
14. Number of uncertain chemical bond stereocenters: 0
15. Number of covalent bond units: 1
Properties and stability
1. Formaldehyde is the simplest aldehyde. It is usually classified as a saturated monoaldehyde, but it is equivalent to a dihydric aldehyde. In the reaction with a weak oxidizing agent, each mole of HCHO can reduce up to 4 mol of Ag or 2 mol of cuprous oxide, which is twice the reducing power of acetaldehyde, so formaldehyde is like a dihydric aldehyde. Industrial products are usually 40% (containing 8% methanol) aqueous solution, commonly known as formalin. Pure formaldehyde gas can liquefy into liquid at -19°C. It can be miscible with non-polar solvents (such as toluene, ether, chloroform, ethyl acetate, etc.) in any proportion at lower temperatures. Its solubility decreases as the temperature increases. Formaldehyde can burn, and its vapor and air can form explosive mixtures.
Chemical properties: Pure formaldehyde has a strong reducing effect, especially in alkaline solutions. Formaldehyde itself can slowly undergo condensation reactions and is particularly prone to polymerization reactions.
2. It is toxic. Inhaling formaldehyde vapor can cause nausea, rhinitis, bronchitis and conjunctivitis. When formaldehyde solution is accidentally swallowed, the stomach should be lavaged with water immediately, and then 100ml of 3% ammonium carbonate or 15% ammonium acetate should be taken. Formaldehyde can cause burns if it comes into contact with the skin. It should be washed with plenty of water and then washed with soapy water or 3% ammonium bicarbonate solution. The operation site adopts an open workshop with natural ventilation. The maximum allowable concentration in the air is 10*10-6. Operators should wear protective equipment.
3. Exists in tobacco leaves, mainstream smoke, and side stream smoke.
4. Formaldehyde is very easy to polymerize, and different polymers are obtained under different conditions.
5. Make formaldehyde into polymers for easy storage and transportation.
Storage method
1. Formaldehyde is in gaseous state at room temperature and usually appears in the form of aqueous solution.
2. Packed in 200L (53USgal) iron drums lined with anti-corrosion materials, with a net weight of 200~210kg, and transported by car or tanker. Formaldehyde aqueous solution is unstable, and the concentration of formic acid and paraformaldehyde increases with time and is related to temperature. Low-temperature storage can minimize acidity, but in order to prevent polymerization, stabilizers such as methanol or methyl and ethyl cellulose can be added to inhibit polymerization. Store and transport according to regulations on toxic chemicals.
3. Storage temperature 4℃
Synthesis method
Formaldehyde is a popular chemical product with wide range of uses, simple production process and sufficient raw material supply. It is the backbone of the methanol downstream product tree. The world’s annual output is about 25 million tons, and about 30% of the methanol is used to produce formaldehyde. However, formaldehyde is an aqueous solution with a low concentration, which is not convenient for long-distance transportation from an economic point of view. Therefore, factories are generally set up near major consumer markets, and import and export trade is very small. Methanol oxidation method and natural gas direct oxidation method are mainly used in industry:
1. Methanol oxidation method: At 600~700°C, methanol, air and water are directly oxidized through silver catalysts or catalysts such as copper and vitriol pentoxide to generate formaldehyde. The formaldehyde is absorbed with water to obtain a formaldehyde solution:
The overall reaction is exothermic, but 50 to 60% of the formaldehyde is produced through the oxidation reaction, while the remainder is produced through the hydrogen reaction. The by-products are carbon monoxide and carbon dioxide, methyl formate and formic acid. The methanol conversion rate is 80%, and the yield is 85% to 90% based on methanol. This method has mature technology and high yield, and is widely used by domestic and foreign production plants.
2. Natural gas oxidation method: At 600~680°C, the mixture of natural gas and air is directly oxidized through an oxide catalyst of iron, molybdenum, etc. to generate formaldehyde, which is absorbed with water to obtain a formaldehyde solution:
3. It is produced by passing methanol vapor into a copper or silver catalyst at 300°C and dehydrogenating methanol. Formaldehyde gas absorbs water content of 36% to 40%, which is a formaldehyde solution. Distill the commercially available formaldehyde solution to remove impurities, and add methanol to obtain the reagent formaldehyde solution.
4. Dimethyl ether oxidation method: It is produced by using dimethyl ether, a by-product of methanol synthesis using a high-pressure synthesis gas method, as the raw material, and using metal oxides as catalyst oxygen er.
5. Methanol dehydrogenation method: Direct dehydrogenation of methanol can produce anhydrous formaldehyde and produce hydrogen as a by-product. This process is an attractive method for the preparation of formaldehyde. The key to its progress lies in the improvement of process catalyst performance.
6. Mix the vaporized methanol with alkali-washed air and water vapor at a ratio of 1:1.8~2.0:0.8~1.0 (volume ratio), then heat to 115~120°C for reaction. Under the action of silver catalyst Control the reaction temperature at 600~650℃ and the pressure at 0.3~0.5MPa:
After the reaction is completed, the reactants are quenched to 80-85°C, absorbed with water, and then distilled to evaporate the unreacted methanol. The kettle liquid is treated with anion exchange resin, and an appropriate amount of polymerization inhibitor is added to the resulting formaldehyde solution, and stirred to mix. The finished product is obtained.
7. Gaseous formaldehyde automatically polymerizes into cyclic trimerformaldehyde at room temperature.
8. Formaldehyde can easily react with ammonia or ammonium salts to condense into hexamethylenetetramine, which is called methenamine.
Purpose
1. Formaldehyde is an important organic raw material, mainly used in the plastic industry (such as phenolic resin, urea-formaldehyde plastic-electric jade), synthetic fibers (such as synthetic vinylon-polyvinyl formal), leather industry, medicine, and dyes wait. Formalin has bactericidal and antiseptic capabilities and can be used to soak biological specimens. Its dilute solution (0.1-0.5%) can be used to soak seeds and disinfect them in agriculture. Catalytic oxidation is commonly used in industry to produce formaldehyde from methanol. Formaldehyde can produce a silver mirror reaction with the silver ammonia solution, causing a thin layer of metallic silver as bright as a mirror to adhere to the inner wall of the test tube (the combined silver is reduced and formaldehyde is oxidized); it reacts with the newly prepared copper hydroxide suspension to form a red precipitate Cuprous oxide.
2. Formaldehyde is widely used in synthetic resins, surfactants, plastics, rubber, leather, papermaking, dyes, pharmaceuticals, pesticides, photographic films, explosives, building materials, and in disinfection, fumigation and antisepsis processes. When it comes to formaldehyde, it can be said that formaldehyde is a generalist in the chemical industry, but the use of anything must have a limit and a standard. Once the use exceeds the standards and limits, it will bring disadvantages.
1) In the wood industry, it is used to produce urea-formaldehyde resin and phenolic resin. It is produced by mixing formaldehyde and urea in a certain molar ratio.
2) Textile industry The use of formaldehyde is involved in the resin finishing process of clothing. In the production of clothing fabrics, in order to achieve anti-wrinkle, anti-shrinkage, flame retardant and other functions, or to maintain the durability of printing and dyeing, or to improve the feel, formaldehyde needs to be added to the additives. At present, formaldehyde printing and dyeing auxiliaries are mostly used on pure cotton textiles, because pure cotton textiles are prone to wrinkles, and the use of formaldehyde-containing auxiliaries can improve the stiffness of cotton fabrics. Textiles containing formaldehyde will gradually release free formaldehyde when people wear and use it, causing respiratory inflammation and skin inflammation through human respiratory tract and skin contact, and can also cause eye irritation. Formaldehyde can cause allergies and can also induce cancer. Manufacturers use dyeing auxiliaries containing formaldehyde. In particular, some manufacturers use cheap auxiliaries with extremely high formaldehyde content in order to reduce costs, which is very harmful to the human body.
3) Preservative solution Formaldehyde is a substance released by the decomposition of formaldehyde and sodium bisulfite above 60°C. It is colorless, has a pungent smell, and is easily soluble in water. 35% to 40% formaldehyde aqueous solution, commonly known as formalin, has antiseptic and sterilizing properties and can be used to soak biological specimens, sterilize seeds, etc.
The reason formaldehyde has antiseptic and bactericidal properties is mainly because the amino groups on the proteins that make up organisms (including bacteria) can react with formaldehyde.
4) The food industry utilizes the antiseptic properties of formaldehyde and adds it to foods that are difficult to store, such as aquatic products.
3. Used as analytical reagent, such as determination of ammonium salt. Used as thin layer chromatography analysis reagent. Also used as a bactericidal disinfectant. Used in phenolic resin production. Preparation of biological specimens.
4. Formaldehyde is the first generation preservative. It has good killing effect on Staphylococcus, Galmonospora, mold, yeast and other Gram bacteria. However, the economic cost of using formaldehyde as a preservative in liquid detergents is too high, and the smell is irritating and toxic to operators.
5. Used as a reducing agent for electroless copper plating, for analysis of electroplating solutions and preparation of zinc electroplating additives.
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