Chemically speaking, ethylene oxide is the simplest of cyclic ethers, also known as epoxides. Its importance in various industries is evidenced by the annual production volume of this chemical compound. It is used primarily as an intermediate in the production of industrial chemicals such as ethylene glycol, as a fumigant in certain agricultural products, and as a sterilising agent for medical equipment and consumables. Ethylene oxide derivatives also have numerous applications.
Characteristics and properties
Ethylene oxide is a colourless gas with a distinct odour. Below 10°C it is a liquid. Its structure contains two carbon atoms, four hydrogen atoms and one oxygen atom. The molecule of this compound takes the form of a triangle. Considering such a specific molecular structure, ethylene oxide is classified into the group of cyclic ethers, commonly known as epoxides. The compound is a gas that is easily soluble in water. It is reactive, meaning that it reacts very easily with other chemical compounds. Ethylene oxide vapours are highly toxic. It is one of the compounds for which the maximum permissible concentrations in the air that are safe for humans are determined. Moreover, liquid ethylene oxide causes severe burns in the presence of moisture. You should also remember that mixtures of ethylene oxide vapours with air are explosive in a wide range of concentrations from 3 to 100 percent.
Ethylene oxide is obtained through a direct oxidation reaction of ethylene. Ethylene is the simplest unsaturated hydrocarbon, classified as an alkene. Its molecule is made up of two carbon atoms joined by a double bond and four hydrogen atoms. The double bond is very unstable and can easily be broken. That is precisely why molecules containing double or triple bonds in their structure are much more prone to reacting with other chemical compounds, compared for example to alkanes, in which all atoms are linked to each other by single sigma bonds. This makes ethylene readily react with the oxygen molecule. Under specific reaction conditions, the double bond in ethylene is broken and the compound takes an oxygen atom, without giving up its hydrogen atoms. In order for this process to occur with the required efficiency on an industrial scale, it is necessary to use a silver-platinum catalyst. The reaction that produces ethylene oxide is a high-temperature process as it occurs in the temperature range of 200°C to 300°C. You can also obtain ethylene oxide by reacting ethylene with chlorine and water.
Applications
A small volume of industrially produced ethylene oxide is used for sterilisation, fumigation and insect control. For this application, the product is used in gaseous form, also in combination with other substances (as a gaseous mixture), such as nitrogen, carbon dioxide or dichlorofluoromethane. Ethylene oxide is used for sterilising medical equipment, packaging, food, medicines, museum exhibits, books and many other things. There are many advantages to the sterilisation process using ethylene oxide. First of all, it is very effective because of the high molecular stability of ethylene oxide molecules. This, in turn, translates into a deeper and more effective penetration of the material to be sterilised. It is important to note that it is effective at low temperatures. This helps to prevent thermal degradation of the sterilised products. In addition, although ethylene oxide vapours are toxic, products sterilised with this compound are not hazardous to their users.
Ethylene oxide is an important raw material with a broad range of applications in chemical processing. It is used to produce ethanolamines and fatty alcohol ethoxylates, among others. However, is it mostly used for the production of ethylene glycols, as a result of a reaction of ethylene oxide first with a proton and then with a water molecule. Ethylene oxide derivatives are also industrially important. They are used in natural gas purification in order to reduce the corrosion of components used in oil and gas processing and in oil well reclamation. Ethylene oxide is one of the ingredients in substances supporting oil production and it protects finished goods from freezing, which results in more efficient energy transformation.
Ethylene oxide and its derivatives are also important in agriculture. They are used to produce a broad range of active substances and inert ingredients used in insecticides, pesticides and herbicides. Each of these ingredients addresses the specific needs of agricultural production, helping to protect crops and increase crop yield. In agricultural crop processing, emulsifiers based on ethylene oxide are used to improve the separation of the oil phase from the aqueous phase, for instance in the extraction of corn oil in the bioethanol production process. The oil can then be used in animal feed or for biodiesel production. Ethylene oxide is also used for the production of industrial starch from agricultural produce, which is a versatile raw material used in many industries, including paper adhesives. At veterinary clinics, ethylene oxide is used for sterilising medical devices, procedure packs, trays and surgical instruments.
Poly(ethylene oxide)
Ethylene oxide readily undergoes a polymerisation reaction that results with macromolecules demonstrating some specific properties. Depending on the method and molecular weight of the polymer obtained, the resulting substances have differing properties and applications. High-molecular-weight ethylene oxide polymers are obtained in the form of powder or fine granules through a suspension polymerization process in the presence of catalysts. Their degree of crystallization ranges from 92% to 95%. Poly(ethylene oxide) has a flexible, waxy structure. Its melting point ranges from 65°C to 70°C. In liquid form, the polymer demonstrates unlimited water solubility. This is related to the identical sizes of the repeat units (mers) in the chain, as well as their propensity to form hydrogen bonds.
Poly(ethylene oxide) is very popular in many industries. The polymer can be easily processed by extrusion, injection moulding, embossing or calendering. Materials made from poly(ethylene oxide), such as threads and films, are characterised by high tensile strength and flexibility. However, at a high humidity (exceeding even 90%), these properties deteriorate significantly. Poly(ethylene oxide) is resistant to oils and greases. High-molecular-weight ethylene oxide has good coagulation and flocculation properties. It also demonstrates the capacity to reduce the hydrodynamic resistance of aqueous solutions.
The ethylene oxide polymer is primarily used in the textile industry, where it is used to make fabrics. In the paint and varnish industry, it is a substrate with thickening properties used for the production of emulsion paints. It has become widely popular in the food industry. Poly(ethylene oxide) is contained in food packaging.