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Comprehensive Overview of Carbon Molecular Sieves
Carbon molecular sieve is a new type of adsorbent developed in the 1970s. It is an excellent non-polar carbon material. Nitrogen-generating carbon molecular sieves (Carbon Molecular Sieves, CMS) are used for separating air to enrich nitrogen. They employ a normal-temperature and low-pressure nitrogen generation process, which offers advantages such as lower investment costs, faster nitrogen production speed, and lower nitrogen costs compared to the traditional cryogenic high-pressure nitrogen generation process. Therefore, it is the preferred adsorbent for pressure swing adsorption (P.S.A for short) air separation for nitrogen enrichment in the engineering field. This type of nitrogen is widely used in the chemical industry, petroleum and natural gas industry, electronics industry, food industry, coal industry, pharmaceutical industry, cable industry, metal heat treatment, transportation, storage, and other sectors.
In addition to its widespread applications, carbon molecular sieves have garnered attention for their environmental benefits and energy efficiency. Unlike traditional methods of nitrogen generation that often involve significant energy consumption and carbon emissions, CMS technology operates under milder conditions, reducing the overall carbon footprint associated with nitrogen production. The ability to generate nitrogen on-site also minimizes the need for transportation and storage of nitrogen gas, further contributing to a more sustainable industrial process. As industries increasingly prioritize green technologies and practices, the adoption of carbon molecular sieves is likely to rise. Moreover, ongoing research and development are focused on enhancing the performance of these materials, such as improving their adsorption capacities and selectivity for nitrogen over other gases. Innovations in the synthesis and modification of CMS could lead to even more efficient and cost-effective solutions for nitrogen generation, catering to the evolving needs of various sectors. As the demand for high-purity nitrogen continues to grow, especially in advanced manufacturing and the production of high-value chemicals, carbon molecular sieves are poised to play a pivotal role in meeting these requirements while aligning with global sustainability goals.
Carbon Molecular Sieve (CMS)
Foreign Name: carbon molecular sieve
Main Component: Elemental carbon
In the 1950s, with the wave of the Industrial Revolution, the application of carbon materials became increasingly widespread. Among them, the application field of activated carbon for PSA nitrogen generation expanded most rapidly, evolving from initial impurity filtration to the separation of different components. Meanwhile, with technological advancements, human processing capabilities for materials became stronger, leading to the emergence of carbon molecular sieves.
Carbon molecular sieves have a black columnar solid appearance. Due to the presence of a large number of micropores with a diameter of 4 angstroms, these micropores exhibit a strong instant affinity for oxygen molecules and can be used to separate oxygen and nitrogen in the air. In industry, nitrogen is produced using pressure swing adsorption (PSA) units. Carbon molecular sieves offer high nitrogen production capacity, high nitrogen recovery rates, and long service lives, making them suitable for various types of PSA nitrogen generators and the preferred product for such equipment.
Carbon molecular sieve-based air separation for nitrogen generation has been widely applied in industries such as petrochemicals, metal heat treatment, electronics manufacturing, and food preservation.
Working Principle
Carbon molecular sieves achieve the separation of oxygen and nitrogen by utilizing their sieving characteristics. During the adsorption of impurity gases by the molecular sieve, macropores and mesopores only serve as channels, transporting the adsorbed molecules to micropores and sub-micropores, which are the actual adsorption volumes. As shown in the preceding diagram, carbon molecular sieves contain a large number of micropores that allow molecules with small kinetic dimensions to rapidly diffuse into the pores while restricting the entry of larger-diameter molecules. Due to differences in the relative diffusion rates of gas molecules of different sizes, the components of gas mixtures can be effectively separated. Therefore, during the manufacturing of carbon molecular sieves, the internal micropore distribution should be in the range of 0.28–0.38 nm based on molecular size. Within this micropore size range, oxygen can rapidly diffuse through the micropore openings into the pores, while nitrogen has difficulty passing through, thereby achieving oxygen-nitrogen separation. The micropore size is the basis for carbon molecular sieves to separate oxygen and nitrogen. If the pore size is too large, both oxygen and nitrogen molecules can easily enter the micropores, rendering separation ineffective. Conversely, if the pore size is too small, neither oxygen nor nitrogen can enter, also making separation impossible.
The raw materials for carbon molecular sieves include coconut shells, coal, and resins. The first step involves processing and pulverizing these materials, followed by blending them with a base material, which primarily serves to increase strength and prevent fragmentation. The second step is activation and pore formation, where an activating agent is introduced at temperatures ranging from 600–1000°C. Common activating agents include water vapor, carbon dioxide, oxygen, and their mixtures. These agents undergo thermal chemical reactions with relatively reactive amorphous carbon atoms to expand the specific surface area and gradually form pores. The activation and pore formation time ranges from 10–60 minutes. The third step is pore structure adjustment, where chemical vapors, such as benzene, are used to deposit on the micropore walls of the carbon molecular sieve to adjust pore size and meet requirements.
Market Analysis
Domestic carbon molecular sieve manufacturers are primarily located in Anhui, Shandong, Jiangsu, and other regions. Domestic molecular sieves have gradually captured a significant market share. However, to grow and strengthen in this industry, it is essential to focus on independent innovation, improve product performance indicators, and break through technological trade barriers.
In the coming years, carbon molecular sieve products will develop towards higher specifications, higher strength, and higher bulk density, while low-specification and low-grade products will be phased out. Air separation equipment will trend towards miniaturization, placing higher demands on the molecular sieve industry. Therefore, by seizing the current favorable opportunities, expanding production, and gradually changing the international and domestic perceptions of low-quality and low-cost Chinese carbon molecular sieves, it is possible to become an industry leader within two to three years.
Domestic Market
The Chinese government places great emphasis on safety in coal mines, oil fields, and oil tankers, mandating the installation of nitrogen generators in these facilities. Additionally, the demands of the electronics and materials industries have further expanded the domestic demand for carbon molecular sieves. According to surveys, the average annual growth rate has exceeded 80% since 2000, indicating a very promising domestic market.
International Market
With the continuous maturation of pressure swing adsorption technology, the application fields of nitrogen generators have broadened, leading to increasing international demand for carbon molecular sieves. Demand in developed countries such as Europe and the United States has been steadily growing each year, while demand in developing countries has surged, doubling annually. Conservatively estimated, the total international demand for carbon molecular sieves exceeded hundreds of thousands of tons in 2023.
Industry Development
According to analyses by international and domestic experts, the carbon molecular sieve industry exhibits the following development trends: First, as the use of pressure swing adsorption nitrogen generators expands, demand for carbon molecular sieves will continue to rise, further promoting industry development. In the coming years, this once-obscure industry will become widely recognized. Second, with increasing application depth, requirements for carbon molecular sieve performance indicators such as nitrogen production capacity, nitrogen recovery rate, bulk density, and compressive strength will become increasingly stringent, making further product performance improvements a major trend in the industry's future development. Third, since carbon molecular sieves are the primary component of pressure swing adsorption nitrogen generators, accounting for over 70% of the total equipment cost, cost reduction will be a crucial factor in promoting industry development. In the coming period, enterprises will continuously explore new materials and processes to achieve the highest performance at the lowest cost.
Two Leaps Forward
Carbon molecular sieves (foreign name: carbon molecular sieves) are novel non-polar adsorbents with the ability to adsorb oxygen molecules from the air under normal-temperature and variable-pressure conditions, enabling the production of nitrogen-rich gas. Their ability to separate air depends on the different diffusion rates or adsorption forces of various gases in the air within the micropores of carbon molecular sieves, or a combination of both effects. PSA air separation for nitrogen generation using carbon molecular sieves is based on this property.
I. Main Product Models
CG-CMS 280
CG-CMS 300
CG-CMS 330
CG-CMS 350
II. Principle of Carbon Molecular Sieve-Based Air Separation for Nitrogen Generation
This product is a carbon-based adsorbent composed of carbon with a porous structure modeled as a disordered stacked carbon structure. Carbon molecular sieves are non-stoichiometric compounds, and their important properties are based on their microporous structure. Their ability to separate air depends on the different diffusion rates or adsorption forces of various gases in the air within the micropores of carbon molecular sieves, or a combination of both effects. Under equilibrium conditions, the adsorption capacities of carbon molecular sieves for oxygen and nitrogen are quite similar. However, oxygen molecules diffuse much faster through the narrow gaps in the micropore system of carbon molecular sieves than nitrogen molecules. Carbon molecular sieve-based air separation for nitrogen generation is based on this property, using the PSA process to separate nitrogen from the air before equilibrium conditions are reached.
Dalian Chuangge Technology Co., Ltd
Richard Han
Doris Zhou
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