preparation method
Chlorohydrin method
The reaction is divided into two steps. The first step is to introduce ethylene and chlorine into water to produce chloroethanol. The second step is that chloroethanol reacts with alkali (usually lime milk) to produce ethylene oxide. [7]
Ethylene hypochlorous acid produces chloroethanol, which is saponified with calcium hydroxide to produce crude ethylene oxide, and then fractionated to produce ethylene oxide. The reaction formula and process flow are as follows.
In China, ethylene oxide was first produced by chlorohydrination of traditional ethanol. In 1970s, China began to introduce ethylene oxide/ethylene glycol co-production equipment to produce ethylene glycol, a polyester raw material.
hydrocarbylation
It can be divided into air method and oxygen method. The former uses air as oxidant, while the latter uses oxygen with concentration greater than 95% (volume ratio) as oxidant. In addition, oxygen-enriched air can also be used as oxidant. The industrial production process of oxidation method is divided into three parts: reaction, ethylene oxide recovery and ethylene oxide refining.
Almost all ethylene oxide industrial production facilities in the world adopt direct oxidation of ethylene with silver as catalyst. Global EO production technology is mainly monopolized by Shell (British-Dutch joint venture), American SD (scientific design company) and American UCC. In addition, there are Japanese catalyst companies, American Dow Chemical Company and German Hess Company with EO production technology.
Main applications
Ethylene oxide is a toxic carcinogen, which was previously used to make fungicides. Ethylene oxide is flammable and explosive, difficult to transport for a long distance, and has a strong regional character. Widely used in washing, pharmaceutical, printing and dyeing industries. It can be used as initiator of cleaning agent in chemical related industries.
Ethylene oxide has bactericidal effect, does not corrode metals, has no residual odor, and can kill bacteria (and its endospore), molds and fungi, so it can be used as a gas disinfectant to disinfect some articles and materials that cannot tolerate high-temperature disinfection. Lloyd Hall, an American chemist, obtained a patent for the sterilization and preservation of perfume with ethylene oxide in 1938. This method is still in use today. Ethylene oxide is also widely used to disinfect medical supplies, such as bandages, sutures and surgical instruments.
It is mainly used to make other solvents (such as fibrin dissolving agent, etc.). ), diluent, nonionic surfactant, synthetic detergent, antifreeze, disinfectant, toughening agent and plasticizer. Water-soluble resin (its ethylene oxide content is about 75%) can be synthesized by hydroxyethyl cellulose. It can also be used as fumigant, coating thickener, emulsifier, adhesive and paper sizing agent. [8]
Usually, the mixture of ethylene oxide and carbon dioxide (the ratio of the two is 90: 10) or the mixture of ethylene oxide and dichlorodifluoromethane is used, which is mainly used for disinfection of hospitals and precision instruments. Ethylene oxide fumigant is often used to preserve grain and food. For example, dried egg powder is often decomposed by bacteria during storage. Fumigation with ethylene oxide can prevent deterioration, but the chemical composition of egg powder, including amino acids, is not affected.
Ethylene oxide can easily react with acid, so it can be added to some substances as an antacid, thus reducing the acidity of these substances or not producing acidity for a long time. For example, in the production of chlorinated butyl rubber, if ethylene oxide is added to the solution of isobutylene and isoprene polymer before chlorination, the finished product can be completely washed without alkali and water.