Effective Way to Remove Water through Desiccant Molecular Sieves

The most effective way to remove water is to run the solvent slowly through a column of the molecular sieves but, usually to remove most water; dried sieves are just positioned into the bulk solvent container (about 5%-10% by volume). Molecular sieves are available in market in the form of beads, pellets & powder.

They have a long list of advantages including of - their consistently high adsorption speed. They offer higher contamination resistance. They also have stronger crushing strength. Their increasing cyclic times which provide an extended product life are also an added advantage.

Typical application areas are: cracked gas drying, drying of highly polar compounds, such as methanol and ethanol, drying of unsaturated hydrocarbons, drying of liquid alcohol, drying of refrigerants, static, (non-regenerative) dehydration of insulating glass units. 3a molecular sieve can absorb unintended moisture, so put them in an air tight container until ready for use to avoid adsorption.

Molecular Sieve 3A Ethanol for Drying

 Molecular sieve 3a is an alkali metal alumina-silicate. It is of type 3A that means it is the potassium form of the type a crystal structure; it contains the effective pore opening of about 3 angstroms (0.3nm). This opening is large enough to allow the moisture inside it, but excludes molecules such as unsaturated hydrocarbons (unsaturated hydrocarbons can potentially form polymers) and this maximizes lifetime when dehydrating such molecules.

These molecular sieves are typically zeolite compounds, these compounds effectively adsorb water and have carefully controlled pore sizes. Both the solvent and the water will adsorb strongly to the molecular sieve surfaces. Smaller water molecules get access to the large surface area within the pores, so that they are successfully removed from the solvent. We can see from the table mentioned below that the water (1.93A) will enter the 3A pore size while acetone (3.08A) will mostly be excluded. Water will occupy the large surface area inside the pores and therefore be removed.  But if the solvent also enter the pores, it would struggle with water for the surface area and the removal of water becomes impossible. So Type 3A molecular sieve is effectively suitable for drying ethanol, methanol, or acetone. But type 4A sieve can fail to do the same since the pore size does not exclude these solvents.

Elements of Ethanol Dehydration Process using 3A Molecular Sieves

Ethanol Drying is basically a process for removing water molecules or something equivalent to water molecules from any substance. Ethanol is drying to obtain ethylene and water when it is heated with catalyst of concentrated sulfuric acid. The ethane gas produced is collected over water and tests are done. This is to find out the typical properties possessed by the unsaturated hydrocarbon. For the dehydration of ethanol one likely product is ethane. In industry this term basically means removing water or moisture from the solution of ethanol which is a result of fragmentation. However, one of the most important dehydration is the dehydration of alcohol from phenyl ethanol.

In the process of ethanol dehydration using molecular sieves 3A Zeolite molecular sieves is used to absorb the water content from ethanol. This absorbent is crystalline form of amino silicates. It has a unique structure which allows crystallized water to be removed and end the end left is a porous crystalline structure. If a polar compound fluid has to be absorbed it can easily be absorbed with the help of low concentration fluid. Molecular sieves have strong absorptive force which allows it to easily remove impurities from gasses or liquids. Having strong ionic forces which is a result of the presence of cations like calcium, sodium and potassium.

Molecular Sieves for Ethanol Dehydration

Before understanding the process of ethanol drying with the help of molecular sieves it is important to understand what is a molecular sieve. It is that material which is used for absorption and has selective properties. These properties are important for the purpose of separating different mixture. It depends on the type of mixture that which size and shape of molecular sieves has to be used. Molecular sieves can be used in any form that is in pelleted, beaded or in powdered form. Molecular sieves are a result of the composition of three dimensional material that is micro porous material, macro porous material and meso porous material. A single bead of molecular sieves is made with the blend of all the three. Molecular sieves are used as absorbents for various other industrial applications. According to the requirement and size molecular sieves are of various types that is 13x, 3A, 4A and 5A. So, now with the help of these efficient absorbents it is now possible to extract moisture from oils to gasses. This is the most reliable source of moisture absorbent in oil and electronic industry.

Molecular Sieve for Ethanol Dehydration Explored

Now a days  most of the countries are facing a great problem in the production of anhydrous ethanol due to the great efforts directed to use biofuels and diminishment in pollution and environmental problems of fossil fuels, So because of this many countries arising this issue as their main problems. Usually the extraction of anhydrous alcohol production comprises three main steps: fermentation distillation and dehydration. The ethanol quantity will be determined purely based on the last step that is the final dehydration step which depends on the operating conditions and the technology used.

 

It was found to be more time consuming and costly, because of this a new catalyst called molecular sieve beads is introduced for the production of anhydrous ethanol. Absolute alcohol is an important product required by industry. Many countries depends the production of high standard alcohol for their economic uplifting.

As per IS specification alcohol should be nearly 100% pure or water free alcohol. Rectified spirit, which is 94.68% alcohol, and the rest contained with water is currently available in market. Practically it is not possible to remain the water content from the rectified spirit by straight distillation as the compound; ethyl alcohol forms a constant boiling mixture with water at this stage to form a product known as azeotrope. Therefore special extraction process is needed for the removal of water for the manufacture of absolute alcohol. So the manufactures of absolute alcohol or for the dehydration of the alcohol we use molecular sieve process.

Molecular Sieves are used in Desiccant Packets

Another important desiccant is molecular sieves. These are also available in form of granules but are assumed to be little less effective than silica gel. It is used to absorb moisture. Next is activated carbon. These are the odor absorbing specialist. The last one is clay. It is also used for absorbing odor as well as some amount of moisture. Although, clay is not used widely! Reason is that once a bag of clay has fully absorbed moisture it has to be changed immediately as it starts to leak water droplets. And absolutely fails to trap moisture inside. Still it is considered as the cheapest way for absorbing moisture.

Many people use a single desiccant at a time but as per the requirement a combination of more than one desiccant can also be used. Suppose, using silica gel and activated carbon in a same packet can help you to get rid of moisture and odor at the same time. As the product does not release any toxins it is safe to use with eatable items. These desiccants are mostly used at the time of packaging of dry food items, shoe boxes, vitamins medicines and many more.

Molecular Sieves have different properties compare to silica gel!

The properties of molecular sieves are very different with that of silica gel in a number of ways. Molecular gel has the capacity to absorb moisture from the environment more quickly that silica gel. It can reduce the moisture to much lower level than that of silica gel because silica gel only works in an extremely dry environment. One more feature which only molecular sieves possess is that it has the ability to separate gasses or liquids based on it molecular size. These crystalline, metal alumina silicates have 3 dimensional network of interconnected silica. Hydrated water can also be easily separated from the network by heating which produces equal cavities which help in absorbing molecules of specific size. Specifically we can use a 4 to 8 mesh size sieve for gaseous applications as it has very small molecular size.

Different properties of Molecular Sieves!

People usually confuse silica gel beads with molecular sieves. Molecular sieves have absolutely different properties as that of silica gel. These small opaque pinkish colored beads are synthetically produced. They are highly porous crystalline beads which are made up of metal alumina silicate. Depending on the name of the variant, they have internal cavities of different size. The cavities are linked by window openings of different diameters. The diameters are measured in Angstroms or A. Absorption occurs only to those substances which have molecular size smaller than the window openings of these desiccants. Substances with larger molecular sizes will be excluded from absorption. This makes molecular sieves ideal for absorption of water and gaseous particles this is because molecules of both water and gas are very small. Molecular sieves helps to absorb contaminants from water as well as gas and reduce the contamination to very low level.

Molecular Sieves are effective to remove moisture from Liquid!

Molecular sieves are excellent desiccants and are very effective in removing moisture from liquid, semi-liquid or gaseous substances. They are said to be even more effective than silica gel or activated alumina. The reason for their popularity is their crystalline composition which helps to create more moisture free products. Molecular sieves prove to be very useful in many cryogenic operations because this process requires gases to be converted into liquid form and in the process even a minute amount of water has to be extracted out in order to avoid freezing. According to the requirement you have different variants bases on its molecular size. As the molecular size increases it gets more surface area to absorb humidity. The variants available are 3A, 4A, 4A indicating molecular sieves, 5A and 13X.