Dehydration of alcohol on molecular sieves
Dehydration of alcohol is a crucial step in the production of bioethanol. It involves the removal of water from ethanol or other alcohols to obtain concentrated anhydrous alcohol. This process is essential for obtaining highly dehydrated alcohol, which finds applications in various industries such as pharmaceuticals, perfumes, food production, and energy. Let’s delve deeper into the process of industrial alcohol dehydration.
There are several methods employed for the dehydration of ethyl alcohol, including azeotropic distillation, molecular sieve adsorption, and membrane evaporation.
Among these methods, molecular sieve technology stands out as an advanced and energy-efficient dehydration technique. Recently, there has been a growing interest in using zeolites for dehydration, particularly in the context of biofuels. The absolute dehydration of bioethanol using molecular sieves follows a specific procedure: an overheated mixture of ethanol vapor and water is passed through a layer of zeolite, which is a porous material with meticulously controlled pore sizes.
The smaller water molecules, due to their size and polarity, are trapped within the pores through electrostatic forces. Meanwhile, larger ethanol molecules pass through the molecular sieves without being retained. As a result, anhydrous ethanol is produced. It is important to note that dehydrated alcohol has high hygroscopicity and requires careful sealing of containers during storage.
The method of obtaining dehydrated alcohol using zeolites is mainly applicable for large-scale production.
Molecular sieves are micro-porous materials with a characteristic three-dimensional lattice structure known as synthetic zeolites. Due to the crystalline nature of zeolites, the pores of this complex framework have a uniform size with cages typically ranging from 3 to 10 angstroms (A). Depending on the pore size, they can selectively adsorb molecules of a specific size, known as the “molecular sieve” effect.
