carbon dioxide

Carbon dioxide, a kind of carbon-oxygen compound, with the chemical formula CO2, is a colorless, odorless, or colorless and odorless gas with a slightly sour taste in its aqueous solution under normal temperature and pressure. It is also a common greenhouse gas and a component of air. one. In terms of physical properties, carbon dioxide has a melting point of -56.6°C (527kPa) and a boiling point of -78.5°C. The density is higher than that of air (under standard conditions), and it is soluble in water. In terms of chemical properties, carbon dioxide is chemically inactive and has high thermal stability (only 1.8% decomposition at 2000°C), incombustible, and generally does not support combustion. It is an acidic oxide with the generality of an acidic oxide. Because it reacts with water to produce carbonic acid, it is an anhydride of carbonic acid.

Carbon dioxide is mainly used in refrigerating perishable food (solid), as refrigerant (liquid), manufacturing carbonized soft drinks (gaseous) and solvent for homogeneous reaction (supercritical state), etc.

High-purity carbon dioxide is mainly used in the electronics industry, medical research and clinical diagnosis, carbon dioxide lasers, calibration gas for testing instruments and the preparation of other special mixed gas, and it is used as a regulator in polyethylene polymerization.

Solid carbon dioxide is widely used in refrigerating dairy products, meat, frozen food and other foods that are perishable in transit. It is used as a refrigerant in many industrial processes, such as crushing heat-sensitive materials, rubber polishing, metal cold processing, and shrinking assembly of mechanical parts , Vacuum cold trap, etc.

Gaseous carbon dioxide is used for carbonized soft drinks, pH control in water treatment processes, chemical processing, food preservation, inert protection in chemical and food processing, welding gas, plant growth stimulant, used in hardening molds and cores and used in casting Pneumatic devices are also used as a diluent for sterilization gas (ie, a mixture of ethylene oxide and carbon dioxide is used as a sterilization, insecticide, and fumigant. It is widely used in the sterilization of medical appliances, packaging materials, clothing, fur, bedding, etc. , Bone meal disinfection, fumigation of warehouses, factories, cultural relics, books).

Liquid carbon dioxide is used as a refrigerant, low-temperature tests of aircraft, missiles and electronic components, to improve oil well recovery, rubber polishing and chemical reaction control, and can also be used as a fire extinguishing agent.

Supercritical carbon dioxide can be used as a solvent to dissolve non-polar, non-ionic and low molecular weight compounds, so it is widely used in homogeneous reactions.