Refining

Refineries use molecular sieve units to treat various gas and liquid hydrocarbon streams requiring purification to meet product specifications, prevent equipment corrosion and damage, protect catalyst units and prevent freezing in the plant. Processes where the molecular sieve units are found include isomerization units (C4 and C5), hydrogen (PSA and TSA, for catalytic units, general use, recycle streams), alkylation units (HF alkylation), recovery streams (LERU, offgas) and iso-normal separation (C4 and C5).

For general purpose drying, a 3A or 4A sieve is often used depending upon the type and level of olefins in the stream. 5A or 13X molecular sieves are often used for stream purification where removal of sulfur, oxygenates, CO2 and CO is required.

Zeochem’s 13X molecular sieve is typically used to remove sulfur and oxygenate impurities. Isomerization units, which convert straight-chain hydrocarbons to branched-chain hydrocarbons that have higher octane value for gasoline blending or for feed to alkylation units, require an upstream molecular sieve for catalyst protection.

Applications

Refinery Hydrogen

Hydrogen streams are in high demand in most refineries, and although hydrogen is generated in areas of the plant such as catalytic reforming, the demand often outstrips the supply. Hydrotreating and especially deep hydrotreating uses a significant amount of hydrogen, making the drying and purification of produced, recovery and recycle hydrogen an important part of maintaining the hydrogen supply. Hydrogen purification includes pressure swing as well as temperature swing units.

Pressure swing adsorption units consist of several vessels with multiple layers of adsorbents. Typical layers may include activated carbon, activated alumina, silica gel and molecular sieve, which is normally the top bed layer. Zeochem’s family of 5A and 13X molecular sieves are often used for the removal of carbon monoxide and carbon dioxide. Nitrogen and other contaminants can also be removed if needed. The resulting hydrogen product is very pure, often to 4 or 5 significant figures.

Thermal swing adsorption units are typically used on recycle, recovery and various other normally small sources of hydrogen; molecular sieve 3A, 4A and 13X are often used. Zeochem Z3-06 and Z4-04 are used when dehydration is the main goal and performance objectives are met.

Related Products

3A

3A is made by ion-exchanging the sodium in type 4A zeolite with potassium. The 3A molecular sieve will exclude most molecules except water, making it very selective.

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4A

4A is the sodium form of the type A zeolite molecular sieve and is widely used as a general purpose drying agent. Under certain conditions, it can also be used for removal of ammonia, alcohols, carbon dioxide, H2S and other specific molecules.

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5A

5A is the calcium-exchanged form of the type A zeolite molecular sieve and is primarily used for removing carbon dioxide, carbon monoxide, alcohols and other oxygenates, hydrogen sulfide, methyl and ethyl mercaptans, and others.

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13X

Type 13X offers enhanced adsorption properties and the ability to remove impurities too large to be adsorbed by the type A zeolites.

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Activated Alumina

Activated alumina adsorbent is an effective bed-topping layer used as a protective layer, at the inlet of gas-phase molecular sieve beds.

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Custom Solutions

Let our technical service team and its decades of experience guide you through product selection and customize a technical design with proper vessel sizing, regeneration flow and operational sequencing. Our team will help you craft the best adsorbent solution for your isomerization, alkylation, hydrogen, LERU and offgas needs. Our experienced team and quality products will help you run reliably, efficiently and predictably.