Tuesday, 27 December 2016

Molecular Sieve Adsorbents for Effective CO2 Removal

What are Molecular Sieve Adsorbents?

When we think of adsorbents, the first thing that comes to mind is Silica Gel. This, however, is not the only adsorbent being used by companies to remove moisture from closed spaces. Molecular Sieve Adsorbents are high-quality desiccants, which are equally effective in maintaining optimum humidity levels. Molecular Sieve Adsorbents are basically crystalline alumino-silicates, commonly known as zeolites.

They are manufactured in such a manner that they have a porous crystalline structure. These pores can re-adsorb water or other polar molecules. With the help of strong ionic forces or electrostatic fields (which are due to the presence of cations such as sodium, calcium and potassium) and with enormous internal surface area of around 1‘000 m2 /g, molecular sieves can take in a large amount of water or other compounds. If the fluid, which is to be adsorbed is a polar compound, it can be adsorbed with high loading, even during very low concentrations of the contaminants. Molecular sieves adsorbents are therefore capable of removing many gas or liquid impurities to very low levels (ppm or less). Another popular positive factor about Molecular Sieve Adsorbents is that they can separate gases or liquids by molecular size or polarity. This is largely made possible by the fact that the pore openings of the Molecular Sieve Adsorbents have the same size as a wide range of products. As the water molecule size is smaller than the Molecular Sieve Adsorbents size, they will be easily absorbed thus maintaining optimum moisture levels.

Molecular Sieve Adsorbents for Carbon Dioxide Adsorption

One may think that Molecular Sieve Adsorbents are only used for water vapour adsorption. That is, however, not the only thing it is used for. Molecular Sieve Adsorbents are utilized for adsorption of other compounds as well. One of them is Carbon Dioxide. Molecular Sieve for CarbonDioxide removal is very common among companies.

For obtaining an adsorbent with typical molecular sieve properties one makes use of thermal processing of granulated carbonaceous material at temperatures of 970-980 degree Celsius. This is usually done in the presence of gases to prevent the oxidation of the carbon material. At temperatures of around −196° C, the adsorption takes place in its micro-pores, whereas nitrogen and argon are taken in at the same temperature at the surface of transitional pores and macro-pores only.

It is mainly oil and natural gas companies, which make use of Molecular Sieve Adsorbents to remove carbon dioxide. It is mainly used to remove CO2 from stream cracked gas, Liquid Petroleum Gas and different atmospheric gases. Mainly, Molecular Sieve 3A and 4A is preferred for the above mentioned purposes.

There are many reasons why Adsorbents 3A and 4A are widely used for carbon dioxide removal. The first being these adsorbents have a high and very rapid adsorption rate. Another factor is that molecular sieve adsorbents are known to have a consistent adsorption speed and have a higher contamination resistance. All these factors make Molecular Sieve adsorbents the ideal substance for removing carbon dioxide from oil and natural gas industries. 

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