Ethanol and its production
Nokuthula NchabelengWhat is ethanol? Ethanol is an organic compound classed under alcohols. It is also known as ethyl alcohol, alcohol, or grain alcohol. Its formula is C2 H6O or more commonly C2H5OH where the -OH (hydroxyl group) identies it as an alcohol. It is a clear, volatile, and colourless liquid with a characteristic odour and high ammability. Ethanol is a product of plant fermentation and can also be produced via ethylene hydration. Ethanol has a range of applications: in the medical eld it is a common antiseptic and disinfectant; it is one of the most used organic chemicals in industrial and consumer products and it is also a fuel source.
Production Processes There are two main types of ethanol – natural ethanol and synthetic ethanol. Chemically, they are indistinguishable; they are rather distinguished by their production method. Natural ethanol can be produced from sugar and starchy materials via fermentation with microorganisms such as yeast. When sugarcane is used, a sugar-rich juice is obtained from crushed cane stalks. The juice is then fermented in a tank with yeast. The liquid product formed by the fermentation is then distilled to 92 – 95 % purity. Further separation processes are then employed to obtain the required purity of ethanol. The overall process is illustrated in Figure 1.
Figure 1: Overview of the production of natural ethanol from sugarcane [Rahman, PKSM and Gunn, R (2017) Processing of Bioethanol from Lignocellulosic Biomass, Advances in Biofeedstocks and Biofuels
Figure 2: Direct hydration of ethylene [Mohsenzadeh, A, Zamani and A, Taherzadeh, MJ (2017) Bioethylene Production from Ethanol: A Review and Techno-economical Evaluation, ChemBioEng Reviews 4(2)].The rst reported synthetic preparation of ethanol was in the 1800s. During this period, a method employing acid-catalysed hydration – similar to that used today in industry – was developed. Today, synthetic ethanol can de produced through either direct or indirect hydration of ethylene. Catalytic direct ethylene hydration comprises of three steps: reaction, recovery, and purication. During the process, a stream of ethylene and steam is preheated and then passed over an acidic catalyst in a packed bed reactor. The remaining reagents are removed from the product mixture in a separator then scrubbed with water to dissolve the ethanol. The two streams formed are then fed to the hydrogenator and purier where acetaldehyde is converted to ethanol and ethanol is concentrated respectively. Figure 2 illustrates a simple diagram of the process of direct hydration of ethylene. iSolvents provides a range of synthetic and natural ethanol products each suited to a variety of applications. Should you require any assistance in your product selection process – we are happy to help.