| HS Code | 115387 |
| Chemical Composition | SiO2·Al2O3 (hydrated silica-alumina) |
| Appearance | white powder, beads, or granules |
| Form | amorphous solid |
| Specific Surface Area | 200–600 m²/g |
| Pore Volume | 0.3–0.8 cm³/g |
| Bulk Density | 400–800 kg/m³ |
| Particle Size | 0.5–5 mm (typical granules) |
| Ph Aqueous Slurry | 4–8 |
| Thermal Stability | stable up to 500–600 °C |
| Water Adsorption Capacity | up to 40% by weight at high relative humidity |
| Acid Site Type | Lewis and Brønsted acid sites |
| Regeneration Method | thermally regenerable at 150–300 °C |
As an accredited Silica Alumina Gel factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Silica alumina gel packaged in sealed 25 kg polyethylene-lined fiber drums, with moisture barrier, labeled for safe handling and storage. |
| Container Loading (20′ FCL) | Silica alumina gel packed in sealed bags on pallets, securely loaded into 20′ container, protected from moisture. |
| Shipping | Silica Alumina Gel ships in sealed, moisture-proof drums or bags to prevent adsorption. Ensure packaging is durable and labeled for non-hazardous material. Store away from strong oxidizers and excessive humidity during transit. Provide documentation for safe handling, spill cleanup, and disposal per local regulations. |
| Storage | Store Silica Alumina Gel in a tightly sealed, airtight container in a cool, dry area. Protect it from moisture, humidity, and direct sunlight, as it absorbs water readily. Keep away from incompatible chemicals and contaminants. Reseal immediately after use to preserve its adsorption capacity and ensure effective performance. |
| Shelf Life | Silica alumina gel has a typical shelf life of 2–5 years when stored sealed in a cool, dry place. |
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Silica Alumina Gel is an amorphous co-precipitated porous solid supplied as spherical beads, extrudate, or irregular granules. The material is not a post-formation blend of silica gel and activated alumina; aluminum is incorporated into the siloxane network during gelation, producing a mixed oxide with both silanol hydrogen-bonding sites and bridging acid sites. Commercial grades are commonly designated by model strings such as SAG-<Al2O3 wt%>/<bead diameter in mm>, and the alumina content is the primary variable controlling acid-site concentration. For a bead-form grade containing 13 wt% Al2O3 and 2.5 mm nominal diameter, representative physical values are BET surface area 450–550 m²/g by ISO 9277:2010, total pore volume 0.55–0.70 cm³/g by ISO 15901-1:2016, packed bulk density 620–680 kg/m³, and single-bead crush strength 80–120 N by ASTM D4179-22. Higher alumina grades, such as 20 wt% Al2O3, displace part of the neutral silanol surface with acid sites and are therefore selected for acid-gas or basic nitrogen removal rather than maximum water capacity.
| Property | Typical range for bead grades | Test method or condition |
|---|---|---|
| Al2O3 content | 5–25 wt% | X-ray fluorescence or wet chemical assay |
| BET surface area | 350–650 m²/g | ISO 9277:2010 |
| Total pore volume | 0.35–0.80 cm³/g | ISO 15901-1:2016 |
| Dominant mesopore diameter | 45–120 Å | N2 desorption BJH |
| Packed bulk density | 480–780 kg/m³ | dried graduated cylinder |
| Single-bead crush strength | 60–150 N | ASTM D4179-22 |
| Particle size range | 1.5–6.0 mm | ISO 3310-1:2016 |
| Loss on drying at 300 °C | ≤1.0 wt% | forced-air oven |
Ammonia temperature-programmed desorption of the 13 wt% Al2O3 grade exhibits a broad desorption band between 150 °C and 350 °C, corresponding to weak and moderate acid sites. Pyridine adsorption IR resolves Brønsted and Lewis acid bands near 1540 cm⁻¹ and 1450 cm⁻¹, respectively. Acid-site density is commonly reported as 0.1–0.3 mmol NH₃/g for 13 wt% Al2O3 and 0.2–0.5 mmol NH₃/g for 20 wt% Al2O3, with measured values dependent on calcination temperature and residual sodium oxide content. This surface acidity is the principal performance distinction relative to silica gel, which has essentially no bridging acidity and therefore displays low affinity for ammonia, light amines, or chloride species.
For a bead grade with 13 wt% Al2O3, water adsorption at 25 °C and 50% relative humidity is generally 30–38 wt% dry basis, slightly below the 35–40 wt% typical of high-density silica gel under the same condition. At 20% RH, capacity falls to 18–25 wt%; at 80% RH, the value reaches 40–48 wt%. The material follows an IUPAC Type IV isotherm with mesopore capillary condensation, and the hysteresis loop is associated with the 45–120 Å mesopore fraction. In a twin-tower adiabatic dryer, the bed height-to-diameter ratio is held between 2:1 and 4:1, and superficial gas velocity is limited to 0.2–0.4 m/s to reduce attrition and bed movement. For cracked gas or LPG containing 5–10 vol% C3+ co-adsorbates, the effective water breakthrough capacity can be 20–40% lower than in clean humid air, and pilot isotherm data are required to set the cycle time.
Regeneration is conducted with dry methane or nitrogen heated to 180–220 °C. Bed outlet gas is cooled to 40 °C before switching back to adsorption. A switch at bed temperatures above 60 °C causes early water breakthrough because adsorption capacity is strongly exothermic and temperature-dependent. At regeneration temperatures above 250 °C, hydrothermal aging becomes measurable: repeated exposure to steam at 250 °C can reduce BET surface area by 5–15% after 500 cycles for the 13 wt% Al2O3 grade, with the exact loss depending on steam partial pressure and aluminum distribution.
| Attribute | Silica gel | Activated alumina | Silica alumina gel |
|---|---|---|---|
| BET surface area | 350–700 m²/g | 250–400 m²/g | 350–650 m²/g |
| Total pore volume | 0.40–1.00 cm³/g | 0.30–0.60 cm³/g | 0.35–0.80 cm³/g |
| Water capacity at 50% RH, 25 °C | 35–40 wt% | 20–25 wt% | 30–38 wt% |
| Regeneration gas temperature | 140–180 °C | 220–320 °C | 180–220 °C |
| Acid-gas and ammonia affinity | low | high | moderate |
| Olefin reactivity above 150 °C | low | higher, can oligomerize | intermediate; pilot testing recommended |
The co-gel does not directly replace silica gel in high-humidity air drying if maximum water removal per adsorption cycle is the controlling parameter, because the steeper high-humidity isotherm of silica gel gives higher capacity at 80% RH. It also does not directly replace activated alumina in chloride or fluoride removal services that demand maximum acid-site concentration and a regeneration source above 250 °C. Silica alumina gel is selected when the feed contains water plus a modest concentration of acidic or basic trace components and when the regeneration system cannot sustain activated-alumina temperatures.
In contrast to 3A or 4A molecular-sieve zeolites, silica alumina gel does not impose a crystalline micropore window of 0.3 nm or 0.4 nm. Its broader mesopore network gives faster intra-particle transport in 2.5–6.0 mm beads and better tolerance to heavy-hydrocarbon fouling, but it cannot perform size-selective water removal in ethanol or olefin streams where 3A zeolite excludes C2+ molecules. For such streams, zeolite-based product remains specified; published data for silica alumina gel in ethanol drying are limited and indicate lower selectivity.
Material handling becomes process-relevant when ambient relative humidity exceeds 60%. Opened drums or supersacks should be charged within 8 h or maintained under dry nitrogen at a -40 °C dew point purge. If liquid water slugs enter the bed, the heat of adsorption can raise outlet gas temperature by 15–30 °C and can crack beads by thermal shock during subsequent regeneration; visual inspection and pressure-drop monitoring are standard after such events. The material should not be used in liquid-phase dehydration of ketones or aldehydes because the acid sites can catalyze aldol condensation above 80 °C. Crush strength after full water saturation is commonly 20–40% lower than the dry crush strength, which is a critical parameter in vessel charging and regeneration design.
In refinery and petrochemical recycle hydrogen loops, chlorides from organic chloride catalyst activation or cracked-gas carryover can be removed together with water if the silica alumina gel is selected with higher aluminum content. A 20 wt% Al2O3 grade in 4.0 mm beads is often evaluated for this dual service because the increased aluminum density raises chloride uptake. Adsorption is favored at temperatures below 50 °C, but conventional thermal regeneration at 220 °C may not fully strip adsorbed chloride; periodic bed replacement or a separate chloride guard layer is often required. Published data for this specific dual-service configuration are limited, and pilot-scale testing is required to establish the chloride breakthrough curve for the exact feed composition. If ammonia is also present, chloride-ammonia interaction can form ammonium chloride deposits in downstream equipment operating below the deposition temperature.
This dual-service application imposes a stricter inlet-temperature boundary than water-only drying. Above 80 °C, competitive adsorption of heavy hydrocarbons can suppress chloride uptake, and olefins may polymerize on acid sites. When diolefins exceed 0.1 mol% in the feed, a guard layer of activated alumina or a lower-acid silica alumina grade is typically placed upstream to limit fouling. Regulatory classification for the unmodified amorphous product typically falls outside dangerous-goods assignment under the UN Model Regulations; the fine-particle fraction remains a dust-control concern and should be handled with process ventilation. Sealed containers stored below 35 °C and 70% RH are typically assigned a shelf life of 24 months from the certificate of analysis date. For potable water or food-contact use, local approvals must be confirmed before product selection.
