1. Introduction
Large-scale AI training clusters, high-performance computing (HPC) and data center GPU cabinets adopt full immersion liquid cooling to achieve ultra-low thermal resistance and uniform temperature control. The widely used dielectric cooling fluids are HFE hydrofluoroethers and PFPE perfluoropolyethers, which feature non-conductivity, low viscosity, high thermal stability and chemical inertness.
During long-cycle circulation, cooling liquid absorbs water vapor from air through micro-seals; water triggers slow hydrolysis of fluorinated molecules to generate trace hydrogen fluoride (HF). Acidic impurities will corrode metal pipelines, damage sealing components and accelerate cooling fluid aging. Meanwhile, tiny organic volatiles from circuit boards and plastic gaskets dissolve into the liquid, deteriorating dielectric performance.
Online continuous purification via molecular sieve fixed beds is the most reliable way to maintain long-term stable operation of AI liquid cooling systems. Appropriate adsorbents can selectively remove moisture and acidic impurities without consuming expensive fluorinated cooling media, realizing cyclic reuse of cooling fluid and lowering overall operation cost of AI computing facilities.
2. Core Purification Challenges of AI Immersion Cooling Fluids
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Strict selective water adsorption requirement
HFE and PFPE are macromolecular fluorinated compounds with large kinetic diameters. The adsorbent must only trap water molecules and avoid adsorbing cooling medium to prevent liquid loss and heat transfer performance attenuation.
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Weak acidic corrosion environment
Trace HF generated by hydrolysis destroys low-silicon A-type molecular sieve frameworks, causing dealumination, pulverization and metal ion leaching that contaminate the cooling loop.
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Ultra-low dust and high mechanical strength demand
Fine powder shed from adsorbents will block micro-channels of cold plates, scratch GPU surfaces and jam precision filter elements, triggering equipment overheating failures.
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Long-cycle continuous operation
Adsorbents need stable cyclic adsorption-desorption performance to support unattended year-round running of AI data centers.
3. Matching Molecular Sieve Grades for AI Liquid Cooling Drying & Purification
3.1 3A Molecular Sieve — Standard Primary Deep Dehydration Adsorbent
3A zeolite has a precise pore size of 3 Å, matching the kinetic diameter of water molecules (2.8 Å), while all fluorinated cooling fluid molecules cannot enter the micropores, achieving 100% selective dehydration without medium loss.
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Core advantages for AI liquid cooling:
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Dehydration depth down to 5–10 ppm residual water, effectively suppressing HF hydrolysis reaction;
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Good compatibility with neutral & weakly acidic fluorinated media, no metal ion dissolution;
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Stable cyclic regeneration performance, reusable dozens of times under standard thermal purge conditions;
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Low abrasion, low dust forming grade avoids blockage of liquid cooling pipeline microstructures.
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Applicable scenarios: All single-component HFE/PFPE immersion cooling circulating loops, primary online drying towers.
3.2 XH-7 / XH-9 Fluorine-Resistant Refrigerant Molecular Sieves — Closed Circulation System Preferred
XH series molecular sieves are specially modified for fluorinated heat transfer media with anti-hydrolysis and anti-HF corrosion skeleton.
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Advantages over ordinary 3A: Higher water adsorption capacity, stronger resistance to long-term trace HF erosion, ultra-low particle wear rate, minimal fine powder generation.
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Applicable scenarios: Large-scale AI cluster closed liquid cooling loops, long-term uninterrupted operation without frequent adsorbent replacement.
3.3 High-Silicon H-ZSM-5 Acid-Resistant Zeolite — High Water Load & Severe Hydrolysis Working Conditions
For cooling systems with poor sealing and high water ingress, high-silicon H-ZSM-5 (SiO₂/Al₂O₃ ≥ 50) is adopted as advanced protective adsorbent. Its high silica-alumina framework resists HF-induced dealumination and pulverization, extending the service life of the purification bed.
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Applicable scenarios: Semi-open immersion cooling cabinets, cooling fluid recovery & regeneration stations.
3.4 Pd90/Pt10 Bimetallic Catalyst — Gas Phase Purification for Nitrogen Blanketing Loop
AI liquid cooling tanks adopt nitrogen inert blanketing to isolate moisture and oxygen. Pd90/Pt10 alumina extruded catalyst matches the molecular sieve tower specification, removing trace oxygen in protective nitrogen to prevent oxidation of circuit components and cooling fluid. Combined with front-end 3A molecular sieve dehydration, it realizes full gas phase purification.
