Ethylene is a hydrocarbon, a flammable and colorless alkene which is found in gaseous form. Ethylene is obtained from petroleum during the refining process. It can also be synthesized from natural gas and is a byproduct of the refining process. Ethylene is used in the manufacture of several chemicals and is also often used as an anesthetic.
Commercially, ethylene is produced by a procedure known as steam cracking. This is a procedure in which groups of hydrocarbons are heated to a point where they break into by products like olefins, propylene and ethylene. The primary hydrocarbons used to commercially manufacture ethylene are gas oil and naphtha.
Steam cracking is a procedure which is carried out in a furnace under high temperatures and unusually high pressure. Sometimes, catalysts may be added to obtain specific by products. As the heat and pressure are increased, the hydrocarbons break into smaller molecules and deposit at exit chambers constructed at different levels in the furnace. In the past several decades, there have been no major technological advances as far as furnace design and cracking technology is concerned.
Modern Commercial Methods
To increase the production of ethylene, advanced olefins are used as catalysts in the cracking process. Though the basic method of breaking down the hydrocarbon molecules remains the same, adding the catalysts allow the cracking to occur at lower temperatures, therefore saving energy. This method increases production of ethylene, while reducing the energy needs by 20 percent and decreasing the carbon emissions.
The cracking of olefins and the entire interconversion process are being researched to boost the outputs. Currently, C4 to C8 olefins are cracked along with pyrolysis gasoline to convert them into ethylene. However, research is continuing to find a better catalytic process which could lower the carbon emissions to a minimum and also enhance the control over the cracking process.
Very meager quantities of ethylene can also be obtained from the streams found in oil refineries. However, the ethylene produced in this manner is extremely dilute. Coal gasification is another method through which small quantities of ethylene can be manufactured. This process is known as the Fisher-Tropsch process and is commonly used in South Africa.