Take You to Know Urotropine
Urotropine, also known as hexamethylenetetramine, is a polycyclic heterocyclic compound with similar structure to adamantane, and the molecular formula is c6h12n4. Urotropine is a white crystal, which can be prepared by the reaction of formaldehyde and ammonia. The molecule contains four mutually fused triazane rings. It is limited soluble in water and easily soluble in most organic solvents.
Urotropine is widely used. It can be used as raw materials for organic synthesis, analytical chemical reagents, antibiotics and fuels, and also has many uses in chemical production. Urotropine reacts with fuming nitric acid to produce highly explosive “cyclone explosive” RDX.
Table of Urotropine
What is urotropine?
Urotropine, also known as hexamethylenetetramine, is a white crystalline or crystalline powder with luster. It tastes sweet at first and then bitter, and has a stimulating effect on the skin. Heating is easy to sublime and decompose, flammable, soluble in water, insoluble in ether, aromatic hydrocarbons, etc. It can treat urinary tract infections and can be hydrolyzed into hippuric acid and formaldehyde under the condition of acidic urine (pH about 6.5). Almost all bacteria and fungi are sensitive to the non-specific antibacterial effect of formaldehyde produced after hydrolysis of this product.
Its main uses are: it can be used as a curing agent for resins and plastics, as a vulcanization accelerator (accelerator H) for rubber, as an anti-shrinkage agent for textiles, and in the preparation of fungicides and explosives. In medicinal use, it can be decomposed into acid urine after oral administration to produce formaldehyde, which has a bactericidal effect, and is used for mild urinary tract infections; Mixed with caustic soda and sodium phenate, it is used as phosgene absorber for gas masks. Urotropine is also a commonly used corrosion inhibitor for slowing the corrosion of metal materials. At present, it is still used as an industrial product and an antibacterial drug.
Why is urotropine added to food?
The role of urotropine illegally added to food is somewhat similar to that of hanging white cubes. The main reason is that urotropine will decompose under weak acid conditions to produce formaldehyde. In the middle, it will have the effects of whitening, fresh-keeping, increasing taste, and anti-corrosion. The use of urotropine in combination with acidic solutions such as dilute sulfuric acid, hydrochloric acid, etc., can cover up the appearance of poor quality food.
For example, the qualified yuba is light yellow, the protein is fibrous, and you can see traces of fibrous tissue against the light; if you pinch it, the quality of the fragile yuba is better; take a few pieces of yuba and soak them in warm water until they become soft and soft. The soaked water is light yellow and not turbid, that is, high-quality yuba. Otherwise, it may be suspected that illegal additives such as urotropine have been added. Fans and aquatic products are the same, if the color is too white, or there is a pungent odor, it is possible that urotropine has been added.
What are the dangers of urotropine？
Urotropine itself is a low toxicity class and can be taken as a drug. However, under acidic conditions, it can decompose formaldehyde, which easily reacts with receptors of various chemical structures in the body, such as condensation with amino compounds, addition to sulfhydryl compounds, and denaturation of proteins. Formaldehyde can also be reduced to alcohol in the body, so it can show the toxicological effect of methanol. It can damage the kidneys, liver, central nervous system, immune function and digestive system of the human body.
At present, my country has the industry standard SN/T2226-2008 “Detection Method for Urotropine Residues in Imported and Exported Foods of Animal Origin by Liquid Chromatography-Mass Spectrometry/Mass Spectrometry”, but it is still necessary to develop hexamethylenetetramine in food detection method. “China Quality News”.
The production process of formaldehyde ammoniated urotropine
The invention relates to a process for producing urotropine by ammoniation of formaldehyde.
In the prior art, the scientific name of urotropine is hexamethylenetetramine, the molecular formula is (CH2)6N4, the molecular weight M=140.19, and it is a white crystalline powder, which is widely used in the pharmaceutical industry, pesticide raw materials, high-energy fuels, and phenolic resin curing. The production process is to heat formaldehyde and ammonia water to vaporize, condense, and crystallize. The disadvantage is that it can only be synthesized from high-quality formaldehyde as raw materials, and can only be synthesized in large professional chemical plants. Production, if a small enterprise uses formaldehyde and ammonia water as raw materials to produce, it cannot be sold because the cost is too high. In the user units using urotropine, formaldehyde is often stored and deteriorated into waste formaldehyde, which has no use value and pollutes the environment.
The object of the present invention is to provide a production process for preparing urotropine by ammoniation of formaldehyde with waste formaldehyde as the main raw material and low production cost in view of the above deficiencies.
The present invention is achieved in this way: the production process of formaldehyde ammoniated urotropine is to obtain urotropine white crystals by condensation reaction, filtration, decolorization, vacuum concentration and drying of a prescribed amount of waste formaldehyde and ammonia water in a reaction kettle . The proportion of formaldehyde and ammonia water is 1:0.38-0.8.
In the present invention, waste formaldehyde is used as the main raw material, and vacuum concentration is adopted. Because formaldehyde and ammonia water are condensed by ammoniation reaction in the liquid phase under normal pressure, the crystallization conditions cannot be reached, and dehydration under normal pressure needs to be heated to above 100 °C, which will partially decompose the formed urotropine, so The water can only be evaporated under low temperature conditions, so the vacuum concentration process is selected to reduce the boiling point of water under negative pressure, and the evaporation speed is fast, which meets the crystallization conditions.
The advantages of the invention are that waste formaldehyde is used as raw material, waste is turned into treasure, product cost is reduced, and environmental protection is beneficial. Waste formaldehyde is 200 yuan per ton, while standard formaldehyde is 1,300 yuan per ton, so that the expired formaldehyde can be reused. Second, the vacuum concentration process is adopted to reduce the boiling point of water, which ensures the formation of the effective components of urotropine, reduces energy consumption, and improves production efficiency.
Formaldehyde ammoniated urotropine production technology
- Condensation reaction: take 2.0 tons of waste formaldehyde (content is 65%), put it into the reaction kettle, add 1.0 tons of ammonia water under stirring, add slight heat and keep it under the condition of not exceeding 40 ℃, the reaction time is 180-200 minutes, keep The pH value of the reaction solution is in the range of 8-9.5, and finally the feed solution is put into the middle tank.
- Filtration and decolorization: After the condensation reaction, carefully observe if there is any precipitation in the reaction solution. After the reaction is terminated, it should be filtered while hot to remove insoluble impurities. Yellow oil often appears in the reaction solution, and then use bone charcoal or activated carbon to decolorize and filter.
- Evaporation, concentration and dehydration: The feed liquid is pumped into the evaporation pot from the intermediate tank for evaporation, dehydration and concentration until the content of urotropine in the feed liquid reaches 40%.
- Vacuum concentration: continue to dehydrate the feed liquid in the reaction kettle at 150mmHg, 60-70 ℃ vacuum, stop heating when urotropine is supersaturated in the feed liquid and stop stirring and stand for cooling crystallization when the temperature is lowered to 30 ℃.
- Drying: After the crystallization is completed, put the urotropine in a centrifuge to separate and dry.
- Drying: Put the dried urotropine in a desiccator, and dry it at 70-80°C and 150mmHg, and finally obtain a finished product of about 500Kg.