Zeolite 13X
[CAS 63231-69-6]

Identification

• Classification: Chemical reagent >> Silane reagent
• Name: Zeolite 13X
• Synonyms: 13X zeolites; Kostrolith 13X; Kostrolith NaMSXK; Linde Mol. Sieve 13X; Linde Molecular Sieve 13X; MS 13X; Mizuka Sieves 13X; Mizuka Sieves 13X488; Mizukalizer 13X; Molecular sieve 13x; Molsiv 13X; Purasiv 628; Purmol 13; Purmol 13X
• CAS Registry Number: 63231-69-6
• EC Number: 613-189-5

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H315-H319-H335
• Safety Statements: P305+P351+P338

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Specific target organ toxicity - single exposure	STOT SE	3	H335
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315

chemBlink Chemical Story

A vessel packed with solid granules can separate gases without turning them into different chemicals. The separation arises because different molecules spend different amounts of time adsorbed inside the solid. Zeolite 13X, CAS 63231-69-6, is an important example of this principle. Its internal framework and charged environment make gas purification a problem of molecular interactions as well as pore access.

13X is commonly supplied as a sodium form of zeolite X, an aluminosilicate with a faujasite-type framework. The framework contains connected internal spaces reached through molecular-scale windows. Its negative framework charge is balanced by cations, and those cations contribute to the way adsorbed molecules interact with the material. An account based only on empty volume would miss much of its adsorption chemistry.

The product designation deserves careful reading. The number in 13X should not be interpreted as a direct measurement of a thirteen-angstrom entrance, nor does it describe the diameter of a visible pellet. It is a material-type designation. Commercial products also differ in shaping, binder content, particle dimensions, and conditioning. A CAS number does not fix every one of these features or specify a universal water loading.

Compared with small-pore 3A molecular sieves, 13X provides access to a broader range of molecules. That can be useful when the target impurity is larger than water, but access alone does not decide what will be retained most strongly. Gas composition, pressure, temperature, and competing adsorbates all matter. A molecular sieve is therefore more than a rigid size filter that sorts every mixture by diameter.

In a 2021 study, Alexander Streb and Marco Mazzotti investigated hydrogen, carbon dioxide, and methane adsorption on zeolite 13X, using equilibrium measurements and breakthrough experiments. Their work examined how these gases behave individually and in mixtures. Carbon dioxide was retained more strongly than the other components under the studied conditions, while hydrogen interacted much more weakly. These differences help explain the material's interest for hydrogen purification.

Equilibrium and breakthrough describe different aspects of the separation. An equilibrium measurement concerns how much gas the material holds at a specified state. A breakthrough experiment follows the gas leaving a packed bed as feed continues to enter. A component initially retained inside the bed can eventually appear at the outlet as the available capacity is consumed. Retention is finite, not permanent disappearance of the impurity.

Water adds another layer. Molecular simulations reported by Joos, Swisher, and Smit in 2013 investigated competition between water and carbon dioxide in zeolite 13X. The work showed why water cannot simply be ignored when interpreting carbon dioxide uptake. A dry-gas result does not automatically predict behavior in a humid mixture, and a calculated result for specified conditions should not be converted into one universal capacity penalty.

Repeated operation requires a way to release adsorbed material and restore useful working capacity. Pressure or temperature changes can contribute to regeneration in adsorption processes, but the complete cycle determines productivity and energy demand. Strong affinity is valuable during capture and can become a burden during release. The largest single uptake measurement is therefore not necessarily the best measure of a practical separation system.

Zeolite 13X illustrates the engineering consequences of reversible molecular attraction. Its usefulness emerges from the combination of framework chemistry, competing guests, and a cycle that repeatedly captures and releases them. Understanding those connections is more informative than treating the granules as a container that simply makes unwanted gases vanish.

References:
1. Sigma-Aldrich. Molecular sieves, 13X, product 208639; CAS 63231-69-6. https://www.sigmaaldrich.com/US/en/product/sigald/208639
2. Streb A, Mazzotti M. Adsorption for efficient low carbon hydrogen production: part 1 - adsorption equilibrium and breakthrough studies for H2/CO2/CH4 on zeolite 13X. Adsorption (2021). https://doi.org/10.1007/s10450-021-00306-y
3. Joos L, Swisher JA, Smit B. Molecular simulation study of competitive adsorption of H2O and CO2 in zeolite 13X. Langmuir (2013). https://doi.org/10.1021/la403824g

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