Silicalite-1 Zeolite
Silicalite-1 is the all-silica form of the MFI framework — a zeolite with essentially no framework aluminium and therefore no acid sites and no hydrophilicity. Its purely siliceous framework makes it strongly hydrophobic and organophilic: it preferentially adsorbs non-polar organic molecules over water, which underlies its use in VOC adsorption, membrane separation, and organosilane synthesis support.
What is Silicalite-1?
Silicalite-1 has the same MFI framework as ZSM-5, but with silicon occupying essentially all framework T-sites (SiO₂/Al₂O₃ typically > 2000). The absence of framework aluminium eliminates the Brønsted acid sites and charge-balancing cations that make aluminosilicate zeolites hydrophilic. The result is a hydrophobic, thermally stable molecular sieve with 10-MR channels (5.1-5.6 Å).
Key Properties
| Property | Silicalite-1 |
|---|---|
| Framework | MFI (all-silica) |
| SiO₂/Al₂O₃ | > 2000 (essentially Al-free) |
| Pore size | 5.1-5.6 Å (10-MR) |
| Acidity | None (no framework Al) |
| Hydrophobicity | Very strong |
| Thermal stability | > 800 °C |
| Typical BET | 300-400 m²/g |
Applications
| Application | Why Silicalite-1 |
|---|---|
| VOC adsorption | Strong hydrophobicity — adsorbs organics over water in humid streams |
| Membrane separation | Hydrophobic MFI membranes for pervaporation and organic/water separation |
| Organosilane synthesis support | Minimal catalytic activity — no unwanted acid-catalysed side reactions |
| Trace organic removal | Adsorption from wet streams without acid-site interference |
| Template for Ti/other substitutions | Parent framework for isomorphous substitution (e.g., TS-1) |
Silicalite-1 vs ZSM-5 for VOC
| Property | Silicalite-1 | ZSM-5 (high SAR) |
|---|---|---|
| Hydrophobicity | Maximum | Very high at Si/Al > 300 |
| Acid sites | None | Sparse at high SAR |
| Catalytic side reactions | None | Minimal |
| Cost | Higher | Lower |
For VOC abatement where catalytic activity must be strictly excluded — or where maximum hydrophobicity is required — Silicalite-1 is the appropriate choice; for general VOC adsorption, high-silica ZSM-5 is the cost-effective standard. See the VOC removal solution hub for selection guidance. When requesting a sample, specify your application (adsorption, membrane, or support) and required particle size/form.
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