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Carbon Molecular Sieve
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  • the types of carbon molecular sieve
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Carbon Molecular Sieve Manufacturer

  • Leaders in the innovation of CMS
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Your Reliable Carbon Molecular Sieve Manufacturer

SWT is known worldwide for having the top-rated carbon molecular sieves. So, whichever application that you may have that requires the use of the carbon molecular sieve (CMS), we are here to assist you to find the correct one. SWT is also good at ensuring the CMS meets the quality needs that you have always wanted. 

SWT is still a top driver in innovations around the use of CMS. As such, we can adapt our carbon molecular sieve production to newer technology always. Of course, having new technology would ensure that the resultant product works as expected. 

Considering that carbon molecular sieves are commonly used in nitrogen production, you should definitely consider what SWT makes. We always test these sieves randomly to check their performance. Such quality checks are vital for ensuring you can always conduct better nitrogen production among other applications of CMSs. 

Our company is continually making the CMS better through research and development. When research does not stop, you are assured of newer and better carbon molecular sieves. For this reason, you can always find more people using SWT for their needs. You too could be one of them and we are ready to help you further. Talk to SWT right now for more details.

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Carbon Molecular Sieve: The Best for Gas Separation


There are multiple types of adsorbents in the market. Sometimes you would get even confused about which is the best. It is only when you read more that you can have the right information about the adsorbent. One such adsorbent is the carbon molecular sieve (CMS). It may be still newer than other adsorbents, but it has generally captured the attention of many industries. This guide looks at it in more detail to identify why it is the best carbon molecular sieve. 

What is a Carbon Molecular Sieve?

activated carbon

The carbon molecular sieve or CMS is seen as the best adsorbent to use in the pressure swing adsorption process. This is the process that is used to separate nitrogen from air. Make sure that you do not confuse carbon molecular sieve from the activated carbon. Yes, activated carbon can still be used as adsorbents. The biggest differences between these two would the pore distribution and the overall surface area. 

One thing that makes the carbon molecular sieve a popular choice should be its pore size. The pore sizes are mostly in the range 3 to 5A. So, they should be able to adsorb several molecule types depending on whare the carbon molecular sieve is used. 

Also, having a wider surface area makes it good at adsorbing different contaminants in a process. The surface area ranges from 250 to 400 m2/g. As for the volume, it is from 0.15 to 0.25cm3/g. As you can see, it should be good for multiple uses in an industry. 

How is a Carbon Molecular Sieve Made?

CMS production

The carbon molecular sieves have found many commercial uses recently. It is for this reason that manufacturers would be seeking the best sources of materials to make the carbon molecular sieves. For commercial use, SWT uses coal and coconut shells. These materials would then go through various processes including oxidation and carbonization. This is then followed by pyrolysis or steam activation. 

The steam activation is when the pores are activated thus leading to the carbon molecular sieve. At this point, the carbon molecular sieves are generally good for hydrogen purification. When the pyrolysis method is used, you end up with carbon deposits too on the sieves. As a result, you now have narrower pore sizes in the carbon molecular sieves. Remember that the carbon molecular sieves will have different pore sizes and it is based on which method you are using to make the carbon molecular sieve. 

There are more recent developments that show carbon molecular sieves can also be made using inorganic oxides in combination with supported metals. The main objective of such a method is to combine the already known molecular sieving performance of carbon with the physical features of inorganic oxides to form one composite structure. An example is having a carbon molecular sieve modified copper then being used for removal of oxygen selectively at temperatures lower than 200 degrees C. Remember that at higher temperatures, the oxygen would be adsorbed only in trace amounts. 

It is understandable if you do not know all the CMS sieves in the market. It is why SWT is here to help you identify the best carbon molecular sieve for your application. 

What are the Carbon Molecular Sieves Properties?

carbon molecular sieve properties

Carbon molecular sieves can have many properties that help it in doing its functions. Here are the top properties to help you have an idea what you would be using. 

  • Can work for separation processes and as a catalyst

Yes, CMS does not just work as an adsorbent, but it can still work as a catalyst in different projects. In recent years, more efforts have been directed towards its separation performance. It is why you would find it a good choice in the PSA application. However, the catalyst support research is still ongoing. 

  • Better stability at higher temperatures

If you are looking at carbon molecular sieves, chances are you have heard of zeolites. These are also used in making molecular sieves, but there are some differences between the two. Studies show that the carbon molecular sieves are generally more stable while working at higher temperatures. Other properties that make them better than zeolites are that they are inert to basic and acidic media and are less hydrophilic.

  • Narrow pore distribution 

CMS will have more of uniformly sized pore sizes. The pore size would vary from as low as 3A up to 12A in some cases. However, compared to activated carbon, the pore size distribution is wider. Thanks to the narrow variation of the pore size, CMS will favor better diffusion of the small molecules while at the same time inhibit the penetration of the larger particles. 

We must note that the carbon molecular sieve will have a slit shaped type of pore structure. Such a pore structure is vital for kinetic separation and also achieving adsorption equilibrium. 

  • Made of amorphous materials 

It is quite hard to study the pore structure of carbon molecular sieves that have a pore size of below 5A. Normally, X-ray diffraction would be used to compare the pore structure to the other molecular sieves. But it is hard to ascertain the pore structurer at this point. 

SWT uses adsorption isotherms to help in probing the molecules to identify more information on the size of a pore, the surface area, the volume, and separation capacity. When we have this information, it is possible to recommend the carbon molecular sieve for specific applications such as the removal of nitrogen from the air among others. 

What is the Difference Between Selective Adsorption and Kinetic Separation in Carbon Molecular Sieves?

carbon-molecular-sieve selective adsorption

The two main methods used by carbon molecular sieves for gas separation are selective adsorption and kinetic separation. 

In the kinetic separation method, it is mostly based on the kinetic diffusion of gas based on the constrictions of the pores’ apertures. The diameters of the pores would act as bottle necks so that specific molecules are adsorbed during the air separation process. A good example is when you are doing an air separation, the oxygen molecules would have smaller diameters than those of nitrogen molecules. It is why the oxygen molecules would be adsorbed leaving the nitrogen ones. 

As for the selective adsorption, the separation is based on the Van der Waals forces that would be between the gas species and the carbonaceous substrate. 

SWT will have a support team to explain everything correctly to you so that you can only pick the best carbon molecular sieve and use it correctly. 

How do Carbon Molecular Sieves Compare to Activated Alumina and Activated Carbon?

CMS vs zeolite

The carbon molecular sieve will be a top choice for various processes that require adsorbents. Since it is a non-polar adsorbent, it will continually have some several applications in different industries. Most of the time, it would be vital in the gas processing sector. So, how does it compare to activated alumina and activated carbon?

  • Activated alumina

Activated alumina material is manufactured by dehydroxylating aluminum hydroxide. The result of this process is that you end up with a highly porous product. It also has quite a significant surface area. Sometimes it can get to over 200 m2/g. Because of this amazing surface area, the product would be good as a desiccant. You can still find it being used as a filter for arsenic, fluoride, and selenium mostly in drinking water. 

What you may not know is that it would also be an SRU catalyst or support material in some processes. So, it is generally a versatile material. 

The activated alumina would mostly be used in adsorbing gases and liquids and it will not change its form. It will work like any other desiccant. Here is where when air passed through it, the moisture is trapped meaning that the air the emerges is dried out. The same applies to liquid sources. The activated alumina will not soften or fall apart. 

The activated alumina can be restored to its former adsorbing efficiency by drying it. This means heating the activated alumina up to 316 degrees Celsius. You can think of regenerating the activated alumina like you do with other molecular sieves. 

Some of the popular applications are HDPE purification, monomer treatment, dehydration of liquid and gas streams, etc. 

  • Activated carbon

You will come across activated carbon more often when searching for carbon molecular sieves. People often confuse these two. However, you should know that they are different each having proper applications. 

The activated carbon is mostly made from substances that contain high carbon content. This includes coconut shells, coal, and wood. The raw material a manufacturer chooses will have a huge impact on the performance of the activated carbon material. 

To activate the carbons, there is the need to exposing the carbon to an atmosphere containing carbon dioxide, carbon monoxide, water vapor, and oxygen. Then, the temperatures are raised to be between 300 to 800 degrees Celsius. This would then be followed by quenching the carbon in water or air. At this point, you will have activated carbon that can work as either a catalyst or an adsorbent. 

As adsorbents, activated carbon can be used in removing dyes, contaminants, tastes, or odors. It may be why you find them mostly being used in water decontamination and subsequent purification processes. The same thing is noticeable when seeking to handle discoloration applications. 

It is hard to find the carbon molecular sieve being used in purifying water. So, some applications are based left for activated carbon. 

Zeolite Molecular Sieves Vs. Silica Gel vs. Carbon Molecular Sieve. Which One to Choose?


It is no secret that the carbon molecular sieve would be mostly used in PSA nitrogen system. This is a system that helps in separating the nitrogen from air with the use of carbon molecular sieves. Those who have used the carbon molecular sieve in this process claim that it leads to a high nitrogen purity. This is to a point of 99.9995% nitrogen. So, how would the other adsorbents do? We try to see what the zeolite molecular sieves and silica gel adsorbents can help you achieve. 

  • Zeolite molecular sieves

Sometimes people think that carbon molecular sieves and zeolite molecular sieves fall under the same category. However, that is not true since the zeolite molecular sieves are made from different materials. The best part is that these materials would end up having uniform and unique structures. The pores form after the manufacturing processes are what industries use to re-adsorb the water and many other polar molecules. 

Carbon molecular sieves have a certain range for their pore sizes. That is not what you find with zeolite molecular sieves. They would have specific sizes and thus categorized into different types that way. You can now get options such as 13X, 3A, 5A, and 4A as the types of zeolite molecular sieves. 

Several industrial applications like to use Zeolite molecular sieves because of their high affinity to adsorb water. As such, you can find many applications for it as a drying agent. 

The zeolite molecular sieves are also good for separating multiple compounds having the same polarity. This should make the sieves highly versatile. Well, it is easy to find many people using them to dry polar compounds. 

  • Silica Gel 

Compared to carbon molecular sieves, you may come across silica gel more often than it. Well, silica gel is the most popular desiccant in the market and will have multiple applications. The popular applications are using silica gel as a desiccant and dehydration of gases and as a catalyst too. 

There will be a few types of silica gel in the market. They are type A which is clear pellets. This one works as a catalyst carrier, separator, and adsorbent. The type B on the other hand is translucent and mostly used as liquid adsorbents and perfume carriers. 

Silica gel will not be good at gas separation as carbon molecular sieve. Also, you cannot find it working great at higher temperatures. Thus, more reason to pick carbon molecular sieves. 

How are Carbon Molecular Sieves Used in Nitrogen Production?

CMS for nitrogen production

The carbon molecular sieves play an important role in the nitrogen processing. This is where the carbon molecular sieves are using the pressure swing adsorption or PSA. You would also find the same working great for hydrogen and biogas refinement from the various crude sources. 

We will focus more on how CMS is used for nitrogen production and how the PSA generators work. In basic terms, carbon molecular sieves will operate at the molecular level and when subjected to pressure, they will help remove oxygen molecules from the atmospheric air leaving you with high purity nitrogen. 

When the atmospheric air is pushed through the porous nano-structure of carbon molecular sieves, the oxygen molecules are trapped. Since the nitrogen molecules are larger, they would not be adsorbed in the sieve. Once it gets to a point that the pores are saturated, the CMS would be de-pressured so that the adsorbed oxygen can be released out through the exhaust and back to the adsorbing level again.

So, you can so far see how the carbon molecular sieve would be an important part of a PSA. 

If you own a PSA, there are other a few things you should do to help maintain its operations better. 

  • Watch out for the recommended operation and maintenance times. Most of the PSA plants are designed to run with needed any attention. Once the plant gets to the full capacity of adsorption, it will then do the desorption. However, you can always watch it to ensure it is working as you want. Of course, follow the planned maintenance schedules to help keep the molecular sieves in the right working conditions. 
  • Also look at safety aspects of the plant while operating it. Always ensure that the PSA plant is operating within moderate pressures and temperatures too. This would largely help in ensuring that you avoid too much pressure that may lead to accidents. Take your time to read the product manual so that you use it well. 
  • You could also consider building a shed or shelter for your PSA. Sometimes the severe ambient conditions can lead to damage. So, keep the PSA from direct rain or sunlight. So, install it in area with a closed shelter. 

Always look at the recommended timeline for carbon molecular sieves in a PSA. If you find that the quality of nitrogen is no longer as you wish, then consider changing the molecular sieves. 

What is the Carbon Molecular Sieve Production Process Like?

Carbon-Molecular-Sieve sample

The carbon molecular sieve production might vary from one manufacturer to another, but the SWT method is as follows. 

  • Carbonization 

During this process, there is carbonizing of the raw materials which are coconut shells in this case. This process will involve the use of pyrolysis conditions while also working under an inert atmosphere. The pyrolysis conditions will experience several things happening including free radicals, aromatic rings, and bridge bonds get decomposed. What follows is the polycondensation reaction which will now lead to the formation of carbon pores. 

Other things that happen under this section is the expansion and shrinkage of the pore sizes. 

Other than using coconut shells, you can use other options such as apricot kernel shell and peach kernel shell for this part. 

  • Extruding and kneading strips

A ball mill is then used in this process. The work of the ball mill will be to grind the material to the required particle size. Sometimes there is the use of polyethylene glycol as the auxiliary agent, water, and a phenol resin as the binder. This is done using a certain ratio that would lead to a certain consistency. The mixture is then extruded as strips from a pellet making machine. 

The importance of kneading is to ensure that the carbonized material can maintain viscosity and also help in the extrusion process making it easier. 

  • Granulation 

After the kneading is done, now it is time for granulation. The extruded molding will be dried and then sent to be broken into the desired size of particles. The granulation process is an important one. It helps in ensuring that the particles are uniform. The uniform particles would make it easier for the activation process. Also, this uniformity is important for the grading of carbon molecular sieves ensuring that your sieves also have consistent performance. 

  • More carbonization 

The carbon molecular sieve will then undergo more carbonization. This will include placing the dried granules through further pyrolysis conditions. Just like before, there would be breaking and decomposition of free radicals, bridge bonds, and so much more behind the scenes. This process is done under constant temperature, heating rate, and time. So, expect the right consistency whenever using such types of carbon molecular sieves later. 

  • Activation 

Of course, there is the need for activation if the carbon molecular sieves are going to work great. During this process, the sieves are heated slowly under active conditions so as to further improve the surface area of carbon molecular sieve. The process is also vital for developing the pore structure of these sieves. 

In case there were any blocked or closed pores, they will be reponed during this process. That is how you will now end up with a carbon molecular sieve having high adsorption rate. 

  • Pore size adjustment 

The pore size adjustment is achieved through the use of carbon deposit method. There is the use of hydrocarbons plus polymer compounds that work as pore plugging agents which end up plugging some of the holes thus adjusting the size of the pores. 

  • Pore diameter adjustment 

The carbon molecular sieves will have several options as the diameter for the pores. You can still use carbon deposit method to help in the adjustment of the pores. You will still be using the polymer compounds and hydrocarbons just like the other method mentioned above. During gas activation, the carbon deposits will get into the pores thus adjusting their sizes. 

The method of production above is what SWT uses. You can get other methods depending on where you are buying the carbon molecular sieve. So, inquire more about the brand so that you buy the best carbon molecular sieves. 



The carbon molecular sieves will be important based on what you are handling. If you are in the nitrogen production sector, such a sieve would be idea. We always recommend that you get it from recommended brands such as SWT if you hope to get the best outcomes. Here are SWT we are ready to work on your order today. Let us know if you are interested. 


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