Molecular sieves

ENERGY AND CHEMICALS

Siliporite^® is an excellent choice for cracked gas units for drying olefins before the cold section.
Natural gas is produced under wet conditions and must be dried to protect downstream equipment, using a temperature swing adsorption (TSA) process. 

MEDICAL AND PHARMACEUTICAL

Siliporite^® is the benchmark solution for preserving the integrity of medicines in pharmaceutical packaging, effectively protecting them from moisture and degradation.

PU CASE

Siliporite plays a key role in polyurethane (PU) systems by removing residual moisture in isocyanates and polyols. Moisture control is critical to ensure proper curing, prevent foam defects, and enhance the durability of CASE (Coatings, Adhesives, Sealants, and Elastomers)

INDUSTRIAL GASES

The Airsiev^® range is widely used for the production and purification of industrial gases such as oxygen and hydrogen. Molecular sieves are used for their nitrogen and oxygen separation properties in PSA/VSA processes, for their drying and CO2 adsorption capabilities in air pre-purification in ASUs, and for their purification properties in hydrogen production.

CONSTRUCTION

Molecular sieves are used in coatings to prevent bubble formation during formulation. Siliporite^® molecular sieves for construction, in beads or powder form, are used to adsorb condensation between glass panes.

SUSTAINABLE SOLUTIONS

Siliporite^® sustainable solutions contribute to energy efficiency and the reduction of greenhouse gas emissions, particularly in gas purification and CO2 capture.

Siliporite^® molecular sieves contribute to four key UN Sustainable Development Goals:

• SDG 3 – Good Health and Well-being: by enabling clean oxygen production and protecting pharmaceuticals from moisture. 
• SDG 7 – Affordable and Clean Energy: by optimizing gas purification in hydrogen and natural gas processes.
• SDG 11 – Sustainable Cities and Communities: through solutions that improve air quality and energy efficiency.
• SDG 12 – Responsible Consumption and Production: by promoting durable, regenerable materials with long service life.

1. What is a molecular sieve?

A molecular sieve, frequently called "mol sieve" is a microporous material, usually made from zeolites, modified silicas or activated carbons, with precisely controlled pore sizes. These pores allow molecules to be sorted according to their diameter and their polarity, acting as a selective filter at the molecular level.

2. What is the history of zeolites ?

Discovered in 1756 by Axel Fredrik Cronstedt—who called them “boiling stones” because of the bubbles they release when heated—natural zeolites were first used for drying and filtration.

In the 1950s, synthetic zeolites (types A, X, Y, ZSM-5, etc.) were developed, offering controlled pore size and composition. These materials quickly transformed the industry, particularly for catalytic cracking and air gas separation.

3. How does molecular sieve separation work?

 Separation is achieved by molecular exclusion or inclusion. Molecules smaller than the pore size penetrate and remain trapped, while larger molecules are excluded. This mechanical selectivity guarantees separation based on the size and polarity of the molecules.

4. What are the main difference between 3A, 4A, 5A and 13X molecular sieves?

• 3Å molecular sieves (Type A, K-form)

Cation-exchanged 4Å zeolite (K⁺) with an effective opening of approximately 3Å. Only molecules smaller than ~3Å (water, NH₃) are adsorbed. Ideal for drying light alcohols (methanol, ethanol) without removing the solvent. Regeneration at 250–300 °C under vacuum or dry gas.

• 4Å molecular sieves (Type A, Na-form)

Sodium aluminosilicate with pores of ~4Å. Adsorbs water, oxygen, nitrogen, and linear hydrocarbons up to C₆, while excluding slightly larger molecules (e.g., longer-chain alcohols). Versatile use as a desiccant for air, industrial gases, solvents. Regenerated at 300–350°C under dry purge.

• 5Å molecular sieves (Type A, Ca-form)

Calcium-exchanged A-zeolite with pores of approximately 5Å. Adsorbs molecules ≤5Å, including CO₂, H₂S, NH₃, and linear or branched hydrocarbons up to C₆–C₇. Prized for natural gas purification (CO₂/H₂S removal) and gas dehydration. Regenerated at ~350°C under dry gas.

• 13X molecular sieves (Type X, Na-form)

Sodium X-zeolite (FAU) with pores of approximately 8 Å (opening ~10 Å). Very high capacity for CO₂, H₂O, H₂S and even aromatics or large organics. Used for volume separation (CO₂ from syngas or biogas), air separation (N₂/O₂), and drying of petrochemical solvents.