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Pseudo Boehmite Alumina Content 70 75 — What It Actually Is (And What It Is Not)

The Al 2 O 3 content on a pseudo boehmite Certificate of Analysis is the single number that decides whether a grade can be used for FCC catalyst, hydroprocessing, three-way catalyst washcoat, or battery separator coating. This guide walks through what 70%, 75% and 80% Al 2 O 3 actually mean at the molecular level, how each grade is made, how they perform in real catalyst plants, the XRF / BET / PSD / peptization / attrition numbers you should expect, and the cost-per-kg-of-Al 2 O 3 trade-off that drives the final selection.

If you buy, specify, or sell pseudo boehmite for catalyst, ceramic, or battery applications, the Al 2 O 3 number on the Certificate of Analysis is the line that determines the price, the application fit, and almost every downstream processing choice. A 70% Al 2 O 3 grade and an 80% Al 2 O 3 grade are the same chemical compound (gamma-AlOOH·nH 2 O) but they behave like different products in the catalyst plant. The difference is the amount of water still trapped inside the powder, the amount of impurity carried with that water, and the energy and care that went into drying the product in the first place.

The Al 2 O 3 number is also a fast proxy for three other properties that take longer to test: surface area (BET), pore volume, and peptization index. A 70% grade typically has 240 to 320 m 2 /g BET and a peptization index above 96%. An 80% grade typically has 180 to 240 m 2 /g BET and a peptization index above 92%. Once you understand this triple correlation — Al 2 O 3 up, surface area down, peptization down — the rest of the specification logic is straightforward.

The next sections walk through the chemistry, the manufacturing routes that produce each grade, the property differences, the per-application selection logic, the cost analysis, and the lab methods you should use to verify the Al 2 O 3 number on a CoA. By the end you should be able to read a pseudo boehmite Certificate of Analysis and pick the right grade for your application in under five minutes.

Pseudo boehmite is aluminum oxyhydroxide with the nominal formula AlOOH·nH 2 O, where n typically runs between 0.08 and 0.62. The orthorhombic structure is the same as true boehmite, but with much smaller crystallite size (3 to 10 nm) and 1.5 to 2.5 layers of interlayer water. If you remove every molecule of water and every impurity, the residue is pure Al 2 O 3 with the molecular weight 101.96 g/mol, and the theoretical Al 2 O 3 content of an infinitely dry, infinitely pure pseudo boehmite is exactly 85.0 wt%.

No commercial pseudo boehmite reaches 85% Al 2 O 3 . The three reasons are practical, not theoretical. First, the spray-drying process that produces the powder cannot remove the last 0.5 to 1.5 percentage points of structural water without driving the dryer inlet temperature above 400 °C, which begins to sinter the smallest pores and kill the peptization index. Second, the powder picks up 2 to 4 wt% of adsorbed moisture from the atmosphere within hours of leaving the dryer; sealed bags only slow this, they do not stop it. Third, even the cleanest Ziegler-route powder carries 50 to 200 ppm of Na 2 O, SiO 2 , Fe 2 O 3 , and CaO as residual impurities from the precipitation chemistry. A "perfectly dry, perfectly pure" pseudo boehmite in a sealed bag on a loading dock is a 80 to 82% Al 2 O 3 product.

Loss on ignition (LOI) is the inverse of the Al 2 O 3 number for pseudo boehmite, because the only things that leave the sample at 1000 to 1200 °C are water and a small amount of CO 2 . The mass balance is essentially:

Pseudo Boehmite Alumina Content 70 75 — The Hidden Defect / Failure Mode

For a 70% Al 2 O 3 grade, LOI is 28 to 32% and the impurity residue is 1 to 2%. For a 75% grade, LOI is 23 to 27% and impurity residue is 0.5 to 1.0%. For an 80% grade, LOI is 18 to 22% and impurity residue is 0.2 to 0.5%. Most catalyst plants also measure LOI at 300 °C and 1000 °C separately to distinguish surface adsorbed water (LOI-300, typically 5 to 10% for a 70% grade) from structural boehmite water (driven off between 300 and 550 °C) and from any residual carbonate or organic residue (driven off above 550 °C).

The 5 to 8 percentage point spread between a 70% grade and an 80% grade is mostly interlayer water and physically adsorbed water. The crystallite structure of the two grades is essentially the same — same orthorhombic AlOOH layers, same 3 to 10 nm crystallite size — but the 80% grade has been dried at a higher temperature for a longer time, which collapses the largest inter-particle pores and removes water that was trapped between the boehmite layers. This is why the 80% grade has lower surface area than the 70% grade even though both have the same chemistry: the extra drying has sintered the smallest pores, lowering BET by 30 to 80 m 2 /g.

Pseudo Boehmite Alumina Content 70 75 — Measured Numbers Across Grades

Fluid catalytic cracking (FCC) is the largest single market for pseudo boehmite, accounting for roughly 60% of global consumption. The reason is the unique peptization behavior of pseudo boehmite: when stirred with dilute (0.5 to 1.0 wt%) nitric or hydrochloric acid, the powder converts almost completely into a transparent, low-viscosity colloidal alumina sol. This sol coats the zeolite (USY or ZSM-5) and the kaolin matrix clay, and during spray drying it glues the components into a mechanically robust 60 to 75 micron microsphere.

For the FCC binder role, the 70% Al 2 O 3 grade is the industry default, used by essentially every merchant FCC catalyst manufacturer. The reasons are economic and technical at the same time:

Property PB-70 (Low grade) PB-75 (Standard grade) PB-80 (High-purity grade)
Al2O3 content 65 to 72 wt% 72 to 77 wt% 77 to 80 wt%
LOI at 1000 °C 28 to 32 wt% 23 to 27 wt% 18 to 22 wt%
Na2O (typical max) 0.05 to 0.10% 0.02 to 0.05% 0.005 to 0.02%
Fe2O3 (typical max) 0.02 to 0.04% 0.01 to 0.02% 0.005 to 0.01%
SO4 (typical max) 1.0 to 2.0% 0.5 to 1.0% 0.2 to 0.5%
BET surface area 240 to 320 m2/g 220 to 280 m2/g 180 to 240 m2/g
Pore volume (BJH) 0.40 to 0.55 mL/g 0.35 to 0.50 mL/g 0.30 to 0.45 mL/g
D50 (laser diffraction) 30 to 60 micron 30 to 50 micron 20 to 40 micron
Peptization index 96 to 99% 95 to 98% 92 to 96%
Loose bulk density 0.40 to 0.55 g/cm3 0.50 to 0.65 g/cm3 0.60 to 0.80 g/cm3

Industry-typical values are based on Q1 2025 COA distribution data across 12 activated-alumina suppliers (internal compilation). Your specific application may need tighter or looser limits — always do a 50 kg trial-and-place test before committing to a 20 t shipment.

Where Pseudo Boehmite Alumina Content 70 75 Earns Its Premium — Core Chemistry

TWC washcoat requires the cleanest pseudo boehmite grade available: 78 to 80% Al 2 O 3 , with Na 2 O below 0.01%, SiO 2 below 0.01%, Fe 2 O 3 below 0.005%, and sulfate below 0.3%. The reason is the extraordinary sensitivity of precious metal catalysts to sodium and iron poisoning. Platinum-group metals dispersed on a high-surface-area support can be deactivated by as little as 50 to 100 ppm of sodium in the support. Sodium migrates to the active metal sites during high-temperature operation (800 to 1000 °C in TWC service) and forms stable Na-Pt or Na-Pd oxides that are catalytically inactive. Iron is similarly damaging: it forms Fe-Pt or Fe-Pd alloys that block hydrogen and oxygen dissociation. Even 50 ppm of sodium in the finished TWC can raise the light-off temperature for CO oxidation by 30 to 60 °C and cut precious metal efficiency by 30 to 50%.

The 80% Al 2 O 3 grade is also the right surface area for TWC washcoat: 180 to 240 m 2 /g is high enough to give 5 to 15 wt% dispersion of the precious metals but not so high that the precious metals sinter rapidly at high operating temperature. The 70% grade (240 to 320 m 2 /g) would give a slightly higher initial precious metal dispersion but the precious metals would sinter 30 to 50% faster, reducing long-term TWC durability. The 80% grade is the only practical choice for TWC, and the extra cost (60 to 110% over the 70% grade) is justified because the washcoat is only 5 to 15 wt% of the finished catalyst and the precious metals are far more expensive than the pseudo boehmite itself.

Al2O3 + H2O -> AlO(OH) + Al(OH)3 (boehmite/gibbsite hydration)

The hydration/dehydration balance between gibbsite, boehmite, and alpha-alumina governs the surface chemistry, pore structure, and mechanical strength of the finished bead. Industrial calcination at 400-600 C produces gamma-Al2O3 with 200-350 m^2/g BET; above 1100 C the transition to alpha-Al2O3 collapses the pore network and BET drops below 5 m^2/g.

Almost all 80% Al 2 O 3 pseudo boehmite for TWC is made by the Ziegler aluminum alkoxide hydrolysis route, because the sodium aluminate route cannot consistently achieve Na 2 O below 0.02% even with multi-stage washing. The Ziegler route gives Na 2 O below 0.005% reliably and is the industry standard for all major TWC washcoat applications in North America, Europe, and Japan.

Pseudo Boehmite Alumina Content 70 75 — Dosing Across Service Conditions

Activated alumina (gamma-Al 2 O 3 ) for adsorbent and desiccant applications is typically made by calcining pseudo boehmite at 450 to 600 °C for 2 to 4 hours. The pseudo boehmite grade choice depends on the target activated alumina grade. For high-surface-area desiccants (300 to 380 m 2 /g BET, used in compressed air drying and gas drying), the 70% Al 2 O 3 pseudo boehmite is the standard starting material. For lower-surface-area catalyst supports (180 to 250 m 2 /g), the 75% or 80% grade is used because the activated alumina will be further sintered in the calciner anyway.

In technical ceramics — alumina substrates, aluminum nitride, zirconia toughened alumina, and similar high-purity formulations — pseudo boehmite is used as a sintering aid and green-body binder. The 75% Al 2 O 3 grade is the standard specification because the ceramic manufacturer wants tighter control over the impurity profile than the 70% grade provides, but does not need the 80% grade's extra cost. Sodium above 0.05% in the binder is a particular problem for alumina substrates used in electronics, where sodium migration can cause dielectric breakdown.

FCC binder specification PB-70 grade PB-75 grade (alt) PB-80 grade (rarely used)
Cost per kg of Al2O3 Baseline (1.0x) 1.15 to 1.20x 1.70 to 2.20x
Microsphere attrition index 1.2 to 1.8 wt%/hr 1.4 to 2.0 wt%/hr 1.8 to 2.6 wt%/hr
Slurry viscosity at 35% solids 180 to 280 cP 220 to 340 cP 320 to 500 cP
Bulk density of finished microsphere 0.78 to 0.85 g/cm3 0.80 to 0.88 g/cm3 0.85 to 0.92 g/cm3

Hydration Kinetics, Set Control, and Working Time

When a pseudo boehmite supplier sends a CoA, the following six questions reveal the analytical competence of the lab and the quality of the product:

The cost of pseudo boehmite is usually quoted per metric ton of powder as delivered, but the cost that matters for catalyst economics is the cost per kg of contained Al 2 O 3 . The two numbers are not the same: a ton of 80% Al 2 O 3 contains 800 kg of Al 2 O 3 , while a ton of 70% contains only 700 kg, so a higher per-ton price for the 80% grade partly reflects the higher Al 2 O 3 content.

  1. Step 1: Cost advantage. The 70% grade is 12 to 18% cheaper per kg of Al 2 O 3 than the 75% grade and 50 to 80% cheaper per kg of Al 2 O 3 than the 80% grade. FCC plants use 25 to 35 wt% pseudo boehmite in the slurry, so the binder is one of the largest variable cost items in catalyst manufacture.
  2. Step 2: Higher surface area and peptization. The 70% grade has 240 to 320 m 2 /g BET versus 180 to 240 m 2 /g for the 80% grade, and a peptization index of 96 to 99% versus 92 to 96%. The extra surface area gives more binder contact area per gram, and the higher peptization index gives a more complete sol with fewer un-peptized agglomerates that would act as stress concentrators in the microsphere.
  3. Step 3: Better green strength during spray drying. The 28 to 32% LOI in the 70% grade is actually an advantage during spray drying: as water leaves the forming microsphere, the surface tension of the receding water pulls the boehmite particles together, giving a "green" microsphere strong enough to survive the calciner without cracking. The 80% grade, with only 18 to 22% LOI, has less of this effect and tends to produce slightly weaker green microspheres.
  4. Step 4: Re-slurrying makes the lower Al2O3 content irrelevant. The FCC binder is re-slurried with water anyway, so the 5 to 8 percentage points of extra water in the 70% grade is added to a slurry that is already 65 to 75 wt% water. The water-of-difference is invisible at the catalyst plant.

Procurement Specification — What to Demand on the COA

The Al 2 O 3 number is only half the moisture story. A pseudo boehmite that is 70% Al 2 O 3 and 30% LOI is different from a pseudo boehmite that is 70% Al 2 O 3 and 35% LOI — the second sample has more adsorbed water and a different bulk density. Always specify both Al 2 O 3 and LOI as ranges on the CoA, and check that the sum plus impurity residue is close to 100%.

A BET surface area of 280 m 2 /g measured after outgassing at 110 °C is not the same as 280 m 2 /g measured after outgassing at 300 °C. The first number reflects the pore structure after losing only surface water, while the second number reflects the pore structure after losing structural water from the smallest pores. Always specify the outgassing temperature (typically 200 to 250 °C under vacuum for 2 to 4 hours is the IUPAC reference for pseudo boehmite).

Application Standard grade Why this grade
FCC catalyst binder 70% Al2O3 Lowest cost, highest surface area, highest peptization
Hydroprocessing catalyst extrudate 75% Al2O3 Higher green strength, tighter Na2O spec
Three-way catalyst washcoat 78 to 80% Al2O3 Lowest Na/Fe impurities for precious metal protection
SCR / NH3-SCR washcoat 78 to 80% Al2O3 Lowest alkali for V2O5/WO3 activity
Li-ion battery separator coating 75% Al2O3 Tight Cl spec, intermediate surface area
Activated alumina precursor 70 to 75% Al2O3 Highest surface area for finished desiccant
Specialty ceramic binder 75% Al2O3 Balance of purity and cost for technical ceramics
Refractory castable binder 70% Al2O3 Lowest cost, strongest hydraulic set

Storage, Shelf Life, and Inventory Hygiene

All grades are produced under ISO 9001 quality control, with SGS on-site audits and full Alibaba Trade Assurance. Each shipment includes a Certificate of Analysis with Al 2 O 3 (XRF + gravimetric cross-check), LOI at 300 and 1000 °C, BET surface area, BJH pore volume and pore size distribution, D10 / D50 / D90 by laser diffraction, peptization index, XRF impurity profile (Na 2 O, SiO 2 , Fe 2 O 3 , CaO, MgO, SO 4 , Cl), and bulk density. Standard packaging is 25 kg PE-lined woven PP bags, 500 kg or 1000 kg super-sacks, or custom packaging on request. Lead time is 7 to 15 days for stocked grades and 25 to 35 days for custom grades. FOB / CIF / CFR terms from Qingdao Port (80 km from our factory).

The Al 2 O 3 content on a pseudo boehmite Certificate of Analysis is the weight percent of aluminum oxide equivalent present after calcining the sample to 1200 degrees C and measuring the residue by XRF or gravimetric analysis. Because pseudo boehmite is a hydrated aluminum oxyhydroxide (AlOOH center dot nH2O with n between 0.08 and 0.62), the theoretical Al 2 O 3 content after total dehydration is always 85.0 wt%. Real commercial grades fall in the 65 to 80 wt% Al 2 O 3 range because the product still carries physically adsorbed water, structural interlayer water, and a small amount of impurity. A higher Al 2 O 3 number therefore means less water, lower loss on ignition (LOI), and a more completely dried, higher-purity product. The Al 2 O 3 number is a proxy for three things at once: dryness, purity, and density of the powder.

Total Cost of Ownership — Why Premium Pays for Itself

LOI (loss on ignition at 1000 to 1200 degrees C) is the inverse side of the Al 2 O 3 number: LOI + Al 2 O 3 + impurity residue = 100%. A 70% Al 2 O 3 grade has LOI of 28 to 32% (mostly structural and adsorbed water plus a small CO2 contribution from residual carbonate). A 75% Al 2 O 3 grade has LOI of 23 to 27%. An 80% Al 2 O 3 grade has LOI of 18 to 22%. Most catalyst plants also measure LOI at 300 degrees C and 1000 degrees C separately to distinguish surface water (driven off below 300 degrees C) from structural water (driven off between 300 and 550 degrees C) and from carbonate or organic residue (driven off above 550 degrees C). A genuine FCC-grade 70% pseudo boehmite should have LOI-300 of 5 to 10%, LOI-1000 of 28 to 32%, and the difference is mostly structural boehmite water plus interlayer water.

Hydroprocessing (HDS, HDN, hydrocracking) catalyst extrudates need 75% Al 2 O 3 grade as the standard specification. The reason: hydroprocessing catalysts are typically trilobe or quadralobe extrudates with 1.0 to 1.6 mm diameter, formed by peptizing pseudo boehmite with a small amount of nitric acid plus a peptizing aid, then extruding, drying, and calcining. The extrudate needs a higher green strength than FCC microspheres, and the 75% grade's lower water content gives a denser, stronger wet mix that extrudes cleanly without cracking. Sodium and iron limits are also tighter for hydroprocessing because the catalysts see hydrogen and sulfur at 300 to 400 degrees C, and residual sodium poisons the Brønsted acid sites. Typical hydroprocessing spec: Al 2 O 3 75 to 78%, Na 2 O below 0.02%, Fe 2 O 3 below 0.015%, SO4 below 0.5%, BET 220 to 280 m2/g, D50 30 to 60 micron, peptization index above 96%.

Grade Per ton of powder (USD) Per kg of contained Al2O3 (USD) Ratio to 70% baseline
PB-70 (FCC grade) 1,200 to 1,500 1.71 to 2.14 1.00x (baseline)
PB-75 (Standard) 1,500 to 1,900 2.00 to 2.53 1.15 to 1.20x
PB-80 (High purity) 2,400 to 3,300 3.00 to 4.13 1.70 to 2.20x
PB-80+ Ziegler (Ultra) 4,500 to 6,500 5.63 to 8.13 2.80 to 3.80x

The math: a 5-10% longer service life plus lower thermal-cycling spalling plus reduced replacement-frequency combine to deliver 12-25% lower TCO over a single cell-stack replacement cycle, even before the safety/insurance argument for eliminating thermal-shock microcracks. The 8-15% raw-material premium pays back 1.5-2.5x over the first cycle.

Industry-typical values are based on Q1 2025 COA distribution data across 12 activated-alumina suppliers (internal compilation). Your specific application may need tighter or looser limits — always do a 50 kg trial-and-place test before committing to a 20 t shipment.

We supply activated alumina, molecular sieve, and alumina-ceramic products as part of a broader specialty adsorbent catalog. The full datasheet for this grade includes additional grain-size distributions, customer-specific blend recommendations, and pilot-plant support. Talk to our technical team if your application has unusual thermal-cycling, mechanical-load, or chemical-feed constraints.

Next Steps — Get a Sample or Talk to Our Engineers

For samples, COAs, or application-specific blend recommendations, reach out to the Aluminaworld technical team. We hold stock of the relevant grade in our Zibo warehouse with same-week dispatch for trial orders, and we can also produce custom recipes for OEMs and EPCs with multi-ton annual demand.

Contact: WhatsApp +86 13325222240 (preferred for fast reply) or email barry@aluminaworld.com. Trial orders ship FOB Qingdao in 7-10 days; full-container shipments in 15-25 days depending on grade and customization.

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