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By: William R. Betz, Michael J. Keeler, Michael D. Buchanan, Reporter US Volume 33.2

What is a “Specialty Carbon Adsorbent”?
A graphic depicting a spherical particle is shown in Figure 1. Controlling pore composition is very important as it determines the adsorption and desorption characteristics of the particle. There are three types of pores relevant to carbon adsorbents. A macropore has a >500 Å diameter, a mesopore has a 20–500 Å diameter, and a micropore has a <20 Å diameter.

Figure 1. Spherical Particle

Unlike non-specific, low-tech carbon black and activated carbon adsorbents, our specialty carbon adsorbents are highly engineered materials, many manufactured from highly pure synthetic polymers. They can be designed with:

  • The shape we want, either spherical or granular
  • No pores, or more/less of any pore type to serve a specific purpose
  • Tapered pores (from macro to meso to micro) which increase thermodynamic and kinetic efficiency
  • A through-pore or closed-pore structure, which influences microporous strength and kinetic effectiveness
  • Surface pH adjustments, as low as 2.5 to as high as 10.5

Today, we make over 30 different specialty carbon adsorbents, including Carbon Molecular Sieve (CMS), Spherical Graphitized Polymer Carbon (SGPC), and Graphitized Carbon Black (GCB) adsorbents. Any modifications (activation, oxidation, graphitization, surface pH adjustment, etc.) are accomplished through physical means, not chemical means.

Scalable Adsorbents
Sixteen of our specialty carbon adsorbents are scalable, signifying we can produce large amounts (>1,000 kg annually) of these adsorbents in 20/40, 20/45, or 30/45 mesh. Included are some of our Carboxen®, Graphsphere™, and Carbotrap® adsorbents. The physical characteristics for each of our scalable specialty carbon adsorbents can be found in Table 1.

If you are investigating a specialty carbon adsorbent for a purification or recovery application, we recommend you focus on the sixteen that are scalable to ensure we can meet your demand if you require a large quantity. Suitable uses in the petrochemical, pharmaceutical, food and beverage, environmental, and other industries include:

  • Purification applications – An interference removal technique is used to remove an impurity or impurities from a gas or liquid stream, such as the purification of industrial gases/solvents, effluent streams, or raw materials.
  • Recovery applications – A bind and elute technique is employed to first capture a compound or compounds from a gas or liquid, and then to recover the compound or compounds. Recovery can be through thermal or solvent desorption. An example is the recovery of a synthesized compound from a reaction mixture.


Table 1. Physical Characteristics and Available Particle Sizes of our Scalable Specialty Carbon Adsorbents

Carbon Adsorbent Sampler Kits
Choosing the right adsorbent or combination of adsorbents can be difficult: 1) must choose one or more to retain specific analyte(s), 2) may be equally important to release analyte(s) during desorption. We offer five convenient sampler kits, which allow a cost-effective way to evaluate several of our specialty carbon adsorbents. Two of these kits contain only scalable adsorbents:

  • CMS/SGPC Kit II (Cat. No. 13369-U) contains 5 g each of nine adsorbents, all in 20/45 mesh (Carboxen 563, Carboxen 564, Carboxen 569, Carboxen 572, Carboxen 1005, Carboxen 1032, Carboxen 1033, Carboxen 1034, and Graphsphere 2017)
  • 20/40 GCB Kit (Cat. No. 13027-U) contains 5 g each of five adsorbents, all in 20/40 mesh (Carbotrap B, Carbotrap C, Carbotrap F, Carbotrap X, and Carbotrap Y)

Custom Capabilities
If you do not find an adsorbent which meets your needs, let us know what the sample is (describe the gas or liquid), what you want to remove, and if you need to recover it afterwards. Our R&D group will investigate whether an existing adsorbent is appropriate or if a new adsorbent needs to be developed. To inquire about a custom specialty carbon adsorbent, please email

Once you find a stock or custom adsorbent that serves your purpose, we will work with you to either make your device for you, or to supply you loose adsorbent (in an ampul, bottle, pail, or drum). Additionally, we will continue to work with you as you implement the adsorbent into your process.

Featured Products
Description Package Size Cat. No.
Carbon Adsorbent Sampler Kits
CMS/SGPC Kit II Kit of 9 bottles 13369-U
20/40 GCB Kit Kit of 5 bottles 13027-U
Carboxen – Carbon Molecular Sieve (CMS) Adsorbents
20/45 Carboxen 563 10 g 10263
20/45 Carboxen 564 10 g 10264
20/45 Carboxen 564 144 ampules of 290 mg 11324-U
20/45 Carboxen 569 10 g 10269
20/45 Carboxen 569 500 g 11048-U
20/45 Carboxen 572 10 g 11072-U
Carbotrap – Graphitized Carbon Black (GCB) Adsorbents
20/40 Carbotrap B 10 g 20287
20/40 Carbotrap B 144 ampules of 190 mg 11325-U
20/40 Carbotrap C 10 g 20309
20/40 Carbotrap C 500 g 11047-U
20/40 Carbotrap X 10 g 10435-U
20/40 Carbotrap Y 10 g 10460-U

Carboxen, and Carbotrap are registered trademarks of Signa-Aldrich Co. LLC
Graphsphere is a trademark of Sigma-Aldrich Co. LLC

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