What is formaldehyde?

It is well known that after buying a new house or building a new house, people will choose to decorate it to make the house more tidy and beautiful. However, during the decoration and for a period of time after the decoration, the house will emit some toxic gases. Among these toxic gases, formaldehyde is the most toxic and can even threaten life. However, many people do not understand formaldehyde. So, what is formaldehyde?

First, what is formaldehyde? Formaldehyde, chemical formula HCHO or CH₂O, molecular weight 30.03, is also known as formic aldehyde. It is colorless, odorless, and irritating to the eyes and nose. The relative density of gas is 1.067 (air = 1), and the density of liquid is 0.815 g/cm³ (-20°C). Melting point -92℃, boiling point -19.5℃. Soluble in water and ethanol. The concentration of the aqueous solution can be as high as 55%, usually 40%, which is called formaldehyde water, commonly known as formalin, a colorless liquid with a pungent odor. It has strong reducing ability, especially in alkaline solution, where its reducing ability is stronger. It can burn, and its vapor can form explosive mixture with air, with explosion limit of 7%-73% (volume). The ignition point is about 300℃. It can be obtained by dehydrogenation or oxidation of methanol under the catalysis of metals such as silver and copper, and can also be separated from the oxidation products of hydrocarbons. It can be used as raw material for phenolic resin, urea-formaldehyde resin, vinylon, hexamethylenetetramine, pentaerythritol, dyes, pesticides and disinfectants, etc. Industrial formaldehyde solution generally contains 37% formaldehyde and 15% methanol, which acts as an inhibitor and has a boiling point of 101°C. On October 27, 2017, the World Health Organization's International Agency for Research on Cancer published a list of carcinogens, listing formaldehyde as a Class 1 carcinogen.

Second, formaldehyde has a wide range of uses and is a popular chemical product with a simple production process and sufficient supply of raw materials. It is the backbone of the methanol downstream product tree. About 30% of the world's methanol is used to produce formaldehyde, with an annual output of about 25 million tons. Formaldehyde solution is a low-concentration aqueous solution. From an economic point of view, it is not convenient to transport long distances, so factories are generally set up near major consumer markets. Import and export trade is also very rare. The main industrial production methods are methanol oxidation and natural gas direct oxidation [2]: 1. Methanol oxidation method: At 600-700°C, methanol, air and water are directly oxidized over a catalyst such as silver, copper or vanadium pentoxide to produce formaldehyde, which is then absorbed by water to obtain a formaldehyde solution:

What is formaldehyde? In the production of clothing fabrics, formaldehyde needs to be added to the auxiliary agents in order to achieve anti-wrinkle, anti-shrinkage, flame retardant and other effects, or to maintain the durability of printing and dyeing, or to improve the feel. Pure cotton textiles are more likely to use formaldehyde printing and dyeing auxiliaries, because pure cotton textiles are prone to wrinkling, and the use of formaldehyde-containing auxiliaries can increase the stiffness of cotton fabrics. Textiles containing formaldehyde will gradually release free formaldehyde during the process of people wearing and using them, which can cause respiratory and skin inflammation through contact with the human respiratory tract and skin, and can also irritate the eyes. Formaldehyde can cause allergies and may 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. The preservative solution, a 35% to 40% formaldehyde aqueous solution, is commonly known as formalin. It has preservative and bactericidal properties and can be used to soak biological specimens, disinfect seeds, etc. However, it can easily make the specimens brittle due to protein denaturation. The main reason why formaldehyde has antiseptic and bactericidal properties is that formaldehyde can react with amino groups on the proteins of organisms (including bacteria).