Caprolactam; ε-caprolactam; Caprolactam
Data national standard number----
CAS number 105-60-2
Molecular formula C6H11NO;NH(CH2)5CO
Molecular weight 113.18
White crystal; vapor pressure 0.67kPa/122℃; flash point 110℃; melting point 68～70℃; boiling point 270℃; dissolved Properties: Soluble in water, soluble in most organic solvents such as ethanol, ether, chloroform, etc.; Density: Relative density (water = 1) 1.05 (70% aqueous solution); Stability: Stable; Danger mark; Main use: used to prepare caprolactam Resin, caprolactam fiber and artificial leather are also used as pharmaceutical raw materials
2. Impact on the environment
1. Health hazards
Invasion routes: inhalation, ingestion Intake and transdermal absorption.
Health hazards: Frequent exposure to this product may cause neurasthenia syndrome. In addition, it can cause nosebleeds, dry nose, upper respiratory tract inflammation and heartburn. This product can cause skin damage. People who come in contact with it may experience dry skin, stratum corneum hyperplasia, chapped skin, and scaling. Systemic dermatitis may occur and it is easily absorbed through the skin.
2. Toxicological information and environmental behavior
Toxicity: low toxicity. Spasmodic poison and cellular protoplasmic poison. It is mainly used on the central nervous system, especially the brainstem, and can cause damage to organs.
Acute toxicity: LD501 155mg/kg (oral in rats); 70g (oral lethal dose in humans)
Subacute and chronic toxicity: Oral in rats 500mg/kg×6 There are changes in monthly weight and blood phase, and pathological damage to the brain; when people inhale less than 61 mg/m3, upper respiratory tract inflammation and burning sensation in the stomach, etc.; when people inhale less than 17.5 mg/m3, neurasthenia syndrome and skin damage occur; when people inhale less than 10 mg/m3 × 3 ~10 years ago, neurasthenia syndrome occurred.
Hazardous characteristics: There is a danger of burning when exposed to high heat, open flame or contact with oxidants. Decomposed by high heat, toxic nitrogen oxides are produced. Powder and air can form an explosive mixture. When it reaches a certain concentration, it will explode when encountering Mars.
Combustion (decomposition) products: carbon monoxide, carbon dioxide, nitrogen oxides.
3. On-site emergency monitoring method
4. Laboratory monitoring method
Determination of caprolactam content in the air: If this product appears as dust in the air , then collect it with a filter. If it is vaporized, use an impact sampling tube to collect it, and then analyze it with gas-liquid chromatography.
5. Environmental standards
China (TJ36-79) The maximum allowable concentration of harmful substances in workshop air is 10mg/m3
Former Soviet Union (1977) Residential areas The maximum allowable concentration of harmful substances in the atmosphere is 0.06 mg/m3 (maximum value, day and night average)
China (to be promulgated) The maximum allowable concentration of harmful substances in drinking water source water is 3.0 mg/L (calculated as BOD)
The maximum allowable concentration of harmful substances in drinking water and recreational water bodies in the former Soviet Union (1978) is 1.0 mg/L
The olfactory threshold concentration is 0.3 mg/m3
6. Emergency treatment and disposal methods
1. Emergency leakage treatment
Isolate the leakage contaminated area, set up warning signs around it, and cut off the source of fire. Emergency responders wear self-contained breathing apparatus and chemical protective suits. Do not come into direct contact with the leaked material. Use a clean shovel to collect it in a dry, clean and covered container and transport it to a waste disposal site. If there is a large amount of leakage, collect and recycle or dispose of it after harmless treatment.
2. Protective measures
Respiratory system protection: When the concentration in the air exceeds the standard, wear a mask-type respirator. Self-contained breathing apparatus should be worn during emergency rescue or escape.
Eye protection: Wear chemical safety glasses.
Protective clothing: Wear work clothes.
Hand protection: Wear rubber gloves.
Others: After work, shower and change clothes. Pay attention to personal hygiene.
3. First aid measures
Skin contact: Take off contaminated clothing and rinse thoroughly with plenty of running water.
Eye contact: Open the upper and lower eyelids immediately and rinse with plenty of running water or saline. Seek medical attention.
Inhalation: Leave the scene to fresh air. Seek medical attention.
Ingestion: If swallowed by mistake, rinse mouth, give milk or egg white, and seek medical attention.
Fire-fighting methods: mist water, foam, carbon dioxide, dry powder, sand.
[Edit this paragraph] Caprolactam production process
In 1943, the German Farben Company first realized the industrial production of caprolactam through the synthesis of cyclohexanone-hydroxylamine (now referred to as the oxime method) . With the development of the synthetic fiber industry, the demand for caprolactam has increased, and many new production methods have been introduced. There have been successively the toluene method (also known as the Snia method); the photonitrosation method (also known as the PNC method); the caprolactone method (also known as the UCC method); the cyclohexane nitration method and the cyclohexanone nitration method. The newly developed amination and oxidation method of cyclohexanone has attracted people's attention because it does not require the use of hydroxylamine for cyclohexanone oximation during the production process and the process is simple.
Among the industrialized caprolactam production methods, the oxime method was still the most widely used method in industry in the 1980s, and its output accounted for the vast majority of caprolactam production. The toluene method has certain development prospects due to its abundant toluene resources and low production cost. Various other production methods have not yet been promoted due to various reasons. For example, among methods using cyclohexane as raw material, the PNC method has the advantages of short process and cheap raw materials; however, it consumes a lot of power and causes serious equipment corrosion.
In the production process of caprolactam, ammonium sulfate is often a by-product. However, because ammonium sulfate is unsaleable, reducing or eliminating the by-product ammonium sulfate has become an important factor in evaluating the economics of today's industrial production of caprolactam.
Oxime method: The main production steps of various oxime methods are as follows:
The lacidine hydroxylamine synthesis method (developed by Farben) uses sulfur dioxide to reduce ammonium nitrite to generate hydroxylamine disulfide Hydroxylamine sulfate is hydrolyzed to form hydroxylamine sulfate. Hydroxylamine sulfate and cyclohexanone react at 80 to 110°C to form cyclohexanone oxime (oxime for short) and sulfuric acid, which are then neutralized with 25% ammonia water to a pH of about 7, and the oxime and ammonium sulfate solutions are separated out in layers.
The HPO method (developed by the Dutch National Mining Company) developed rapidly in the 1980s. The HPO method uses a palladium catalyst with charcoal or alumina as a carrier in a phosphate buffer solution to hydrogenate nitrate ions to form hydroxylamine salt, which is then oximated with cyclohexanone in a toluene solvent.
The HPO method combines the synthesis of hydroxylamine with the oximation process, and oximation produces no ammonium sulfate as a by-product. In the reaction waste liquid, after adding nitric acid, it can be returned to the nitrate ion hydrogenation process for reuse.
The nitric oxide reduction method (developed by Yinwenda Research and Patent Company of Switzerland and BASF of the Federal Republic of Germany) uses a platinum catalyst (see metal catalyst) in dilute sulfuric acid to hydrogenate nitric oxide. This method is a by-product. It contains less ammonium sulfate, but requires high raw material purity and a catalyst recovery process. Currently, it is rarely used.
Beckmann rearrangement (referred to as transposition) oxime is translocated in fuming sulfuric acid, the reaction temperature is 80~110℃, and the yield is 97%~99%. The product was neutralized with 13% ammonia water.
Neutralization produces crude caprolactam solution (also known as crude oil) and ammonium sulfate. In order to eliminate the ammonium sulfate by-product of translocation, the Dutch National Mining Company developed a sulfuric acid recycling method. It neutralizes the sulfuric acid in the transposition product to generate ammonium bisulfate, and then uses a solvent to extract caprolactam. Ammonium bisulfate is then pyrolyzed into sulfur dioxide, and the sulfur dioxide is converted into fuming sulfuric acid for recycling. Translocation methods without by-product ammonium sulfate include gas phase transposition method, ion exchange resin method, electrodialysis separation method, etc.
[Edit this paragraph] Caprolactam refining
In various caprolactam production methods, caprolactam needs to be refined. General refining methods include: chemical refining (potassium permanganate oxidation, catalytic hydrogenation, etc.), extraction, recrystallization, ion exchange resin, vacuum distillation, etc. In order to obtain high-purity products, several combinations are generally used in industry. methods for joint refining.
Toluene method
Toluene is oxidized under the action of cobalt salt catalyst to generate benzoic acid; the reaction temperature is 160~170℃, the pressure is 0.8~1.0MPa, the conversion rate is about 30%, and the yield is 92% of theoretical value. Benzoic acid is subjected to liquid-phase hydrogenation using a palladium catalyst on an activated carbon carrier to generate hexahydrobenzoic acid; the reaction temperature is 170°C, the pressure is 1.0-1.7MPa, the conversion rate is 99%, and the yield is almost 100%. In fuming sulfuric acid, hexahydrobenzoic acid reacts with nitrosyl sulfuric acid to form caprolactam, which is neutralized with ammonia; the conversion rate is 50% and the selectivity is 90%.
In order to reduce or eliminate by-product ammonium sulfate, improved by-product ammonium sulfate halving method and no by-product ammonium sulfate method were developed.