Ethylene production

Ethylene or ethane is a colorless flammable gas with a weak muscat and sweet smell. Its chemical formula is C2H4. Ethane is the simplest alkene (unsaturated hydrocarbons having one double bond between adjacent carbon atoms). The molar mass is 28.05 g / mol. The melting point is -169.2 ° C, the boiling point is -103.7 ° C. The flash point is -136 ° C, autoignition is +542.8 ° C. In 1680, I.Bercher (German physician and chemist) from wine alcohol when exposed to it with vitriol oil (as sulfuric acid was called at that time ) , ethylene was first produced from ethanol. The structural formula of ethylene in 1860 was established by the Russian chemist A. M. Butlerov as a result of the reaction of methylene iodide with copper. This gas is slightly lighter than air, it is poorly soluble in water, in organic solvents it is good.

The production of ethylene and the study of its properties, which began in the mid-19th century, led today to the fact that ethylene is the most sought-after organic compound. Its world production reached in 2006 more than 109 million tons. Today the production of ethylene continues to develop. By 2010, it produced at least 117 companies in 55 countries. Ethylene is used as a raw material in the production of high and low pressure polyethylenes, sevylene and other polymeric materials obtained by copolymerization with various comonomers. It is also used for the production of ethylbenzene and styrene, ethylene oxide, vinyl chloride, vinyl acetate, acetic acid, ethyl alcohol and ethylene glycol.

What is the reason for the growth of production facilities aimed at obtaining ethylene? Mainly the expansion of the market of polymer materials. Polyethylenes of various types consume more than half of the world's ethylene production. This polymer material is the most widely used plastic in the world. It produces films for various purposes. Linear alpha-olefins obtained by oligomerization (formation of short chains of polymers) are used as precursors, detergents, plasticizers, synthetic lubricants, additives, and as comonomers in the production of polyethylenes. Another important direction of the use of ethylene is its oxidation in order to produce ethylene oxide, which is the main raw material in the production of surfactants and detergents. Ethylene oxide undergoes hydration, resulting in the production of ethylene glycol. It is widely used as an automotive antifreeze.

Today, the production of ethylene is carried out mainly as a result of pyrolysis of straight-run gasoline or a wide fraction of light hydrocarbons. In Russia and the former Soviet republics, there are installations of various capacities built both by domestic (Giprokauchuk, VNIPINeft, Bashgiproftekhnechim) and by foreign technologies (Linde AG). Operating production can be divided into three groups: small capacity (30 and 60 thousand tons of ethylene per year), medium (100 and 200 thousand tons per year) and high (300 and 450 thousand tons of ethylene per year). Now in the world installations with much greater capacity are operated: from 400 to 500 and even to 800 thousand tons of ethylene per year. Such an increase in production allows us to reduce specific material, energy and capital costs.

Ethylene is produced in chemical plants, including a pyrolysis unit, a gas separation plant, and a chemical water treatment plant. Raw materials - gasoline or other light fraction of oil production or oil refining in a mixture with water vapor (to reduce the process of coke formation in furnace pipes). The raw material enters the pyrolysis furnace, where at a temperature of 750 to 900 ° C, pyrogas is formed, consisting of hydrogen and hydrocarbons, in molecules of which is contained from one (methane) to twenty carbon atoms. The heat of the pyrogas is disposed of in special devices, where high-pressure steam is produced from chemically purified water, and the cooled pyrogas enters the pyrolysis (heavy) and pyro-condensate resin separation unit. After that, the pyrogas containing mainly hydrocarbons from C1 to C4 is fed to the turbocharger (the turbines are driven by high-pressure steam), from where it is fed under pressure to the rectifying columns of the gas separation unit. Here, the main products such as ethylene and propylene are produced (its yield is always 2 times less than ethylene), as well as by-products: hydrogen, methane, ethane, propane, butylene-butadiene fraction, pyrolysis light resin or components Motor gasoline.

It is also possible to obtain ethylene by catalytic pyrolysis. On an industrial scale, this method is not implemented, although its tests in our country at one time were carried out not only in laboratory installations, but also in industrial conditions. Its advantage is the possibility of reducing the pyrolysis temperature due to the use of catalysts. As a result of increasing the selectivity of the process, the yield of ethylene and propylene increases compared to thermal pyrolysis, the formation of by-products as well as coke is reduced. Currently, researchers in different countries are working in the direction of finding an effective catalyst and instrumental design process.