DISPERAL
DISPAL
High-Purity Dispersible
Alumina Hydrates
Sasol Performance Chemicals
High-Purity Dispersible Alumina Hydrates Content
Content
About Us..........................................................................3
1. Alumina Production Process.........................................4
2. DISPERAL/DISPAL.........................................................5
2.1 High-Purity Dispersible Boehmites................................................................. 5
2.2 Features of Sasol Dispersible Boehmites........................................................ 5
2.3 Advantages of DISPERAL and DISPAL.............................................................. 6
2.4 How to Disperse and Use Disperal and Dispal................................................. 7
2.5 Water Dispersible Boehmite............................................................................ 7
2.6 Acid Dispersible Boehmite............................................................................... 8
2.7 Neutral to Alkaline Dispersible Boehmites...................................................... 8
2.8 Rheology........................................................................................................... 8
2.9 Solvent Dispersible Boehmites........................................................................ 9
3. Technical Data............................................................10
3.1 Water Dispersible Boehmites.........................................................................10
3.2 Acid Dispersible Boehmites............................................................................10
3.3 Surface Modified Boehmites..........................................................................10
4. Product Information...................................................12
4.1 Storage and Transfer......................................................................................12
4.2 Safety and Handling.......................................................................................12
4.3 Technical Support...........................................................................................12
5. Certifications..............................................................12
6. Analytical Methods.....................................................14
6.1 Crystallite Size.................................................................................................14
6.2 Dispersed Particle Size...................................................................................14
6.3 Dispersibility of Boehmite Powder................................................................14
6.4 Surface Area....................................................................................................14
6.5 Trace Element Analysis...................................................................................14
6.6 Pore Volume and Pore Size Distribution........................................................14
2
High-Purity Dispersible Alumina Hydrates About Us
About Us
Sasol Performance Chemicals develops and markets a broad portfolio
of organic and inorganic commodity and specialty chemicals and
comprises three key business divisions: Organics, Advanced Materials
and Wax. Our offices in 18 countries serve customers around the world
with a multifaceted portfolio of state-of-the-art chemical products and
solutions for a wide range of applications and industries.
Surfactants, surfactant intermediates, fatty alcohols, linear alkyl benzene (LAB), short-chain
linear alpha olefins, mineral oil-based and synthetic paraffin waxes, high-purity and ultra-high-
purity alumina as well as high-quality carbon solutions form the basis of our key product range.
As individual as the industrial applications they serve, the tailor-made solutions offered by
our products create real business value for customers. Ongoing research activities result in a
continuous stream of innovative product concepts that help our customers position themselves
successfully in future markets.
Our products are used in countless applications in our daily lives to add value, security and
comfort. Typical examples include detergents, cleaning agents, personal care, construction,
paints, inks and coatings, metalworking and lubricants, hot-melt adhesives, bitumen
modification and catalyst support for automotive catalysts and refineries as well as other
specialty applications including oil and gas recovery, agriculture, plastic stabilization, and
polymer production. Every day, our researchers explore ways to improve our products and
develop innovations that improve the quality of people’s lives.
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High-Purity Dispersible Alumina Hydrates Production of Aluminas
1. Alumina Production Process
Sasol Inorganics produces high- and ultra-high-purity aluminas primarily through snythetic
aluminum alkoxide processing routes. The alumina is produced either as co-product with
synthetic linear alcohols (Ziegler method) or directly from aluminum metal (on-purpose route).
Several production steps must be completed to produce the different alumina-based
products. In the first step, an aqueous intermediate (alumina slurry) is produced, which is
further tailored in the subsequent processing steps to obtain the various products sold on
the market. These can be alumina hydrates, calcined aluminas and doped versions thereof.
Hydrolysis Drying/calcining facilities
Alumina
Spray drying
hydrates
Ziegler
SIEVING
Calcined SIFTING Slurry ± 400
Calcining BAGGING specifications processing aluminas
TAM Alumina
Drum drying
hydrates
Figure 1: Schematic for the alumina manufacturing process
4
High-Purity Dispersible Alumina Hydrates DISPERAL/DISPAL
2. DISPERAL/DISPAL
2.1 High-Purity Dispersible Boehmites
DISPERAL and DISPAL are the trademarks for the high-purity, highly dispersible boehmite
powders and sols/dispersions manufactured by Sasol in Brunsbüttel, Germany, and in
Lake Charles, Louisiana, USA. These boehmites, which are nano-sized in the dispersed
phase, exhibit a unique combination of purity, consistency and dispersibility that make
them excellent materials for use in colloidal applications. The Sasol range of dispersible
boehmites has traditionally been used in applications such as sol-gel ceramics, catalysis,
refractory materials, rheology control and surface frictionizing.
Other applications include surface coating as well as paint detackification, polymer-
additives and functional fillers.
2.2 Features of Sasol Dispersible Boehmites
The unique product characteristics of Sasol dispersible boehmites can lead to many
advantages for use in different systems. Some key features are:
• The high purity boehmites are produced under careful control to yield products with
consistent quality and reliable performance.
• The powders are highly dispersible. Low-viscosity nano-sized particle sols can be prepared
at room temperature in 10 to 30 minutes with concentrations of 10–40 wt.% AlOOH.
• The boehmites are versatile. They can be employed under a variety of application
conditions, including low or high pH and low or high shear.
• Sasol also offers boehmites which are dispersible in polar and non-polar organic media.
Figure 2:
Translucent to opaque boehmite sols,
each with a concentration of
10 wt.% AlOOH
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High-Purity Dispersible Alumina Hydrates DISPERAL/DISPAL
2.3 Advantages of DISPERAL and DISPAL
Sasol pioneered processes utilizing alkoxide chemistry to convert primary aluminium metal
into synthetic boehmite of exceptional purity. Unlike other alumina manufacturing processes
that start with less pure materials, Sasol’s processes yield aluminas with significantly lower
levels of common impurities such as iron, sodium and silica (table 2). Additionally, our 50
years of experience, in combination with other proprietary production techniques, allow us
to produce highly dispersible boehmites with a wide range of physical properties such as
dispersed particle size (figure 3) resulting in translucent to opaque dispersions (figure 2).
Thus, our customers are not limited in their thinking for possible uses for the aluminas.
Table 1
Chemical purity of
DISPERAL and DISPAL
boehmite powders
Impurity ppm (typical)
Na2O <20
Fe2O3 50–100
SiO2 50–120
Figure 3:
Dispersed particle size distributions
of selected products 20 nm 40 nm 75 nm 150 nm 300 nm
10 100 1000 nm
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High-Purity Dispersible Alumina Hydrates DISPERAL/DISPAL
2.4 How to Disperse and Use DISPERAL and DISPAL
DISPERAL and DISPAL powders may be dispersed by following the descriptions below. Figure 4
shows a schematic representation of what occurs to the powder during dispersion using
chemical attack and mechanical energy.
Figure 4:
Schematic mechanism of dispersion
Mechanical Chemical
energy attack
Mechanical
energy
Powderparticle Agglomerates Primary aggregates
40 micron 5–10 micron 20–500 nm
2.5 Water Dispersible Boehmite
To form a colloidal sol or dispersion from a water dispersible DISPERAL or DISPAL powder (see
page 10), simply stir the powder in deionized water with moderate to intense agitation at room
temperature for 20–30 minutes. The maximum achievable solids loading will vary according to
the specific boehmite selected (figure 5). For most applications, the boehmites perform best
when completely dispersed prior to further formulation. The resulting pH will be between 3 and
5. DISPAL 11 N7-80 that is modified with 0.1 wt.% nitric acid can be dispersed at pH 6–7 as
well.
Figure 5:
Schematic mechanism of dispersion
100000 30 wt.%
20 wt.%
10000
10 wt.%
1000
[mPa•s] 100
10 Viscosity
1
0.1
0 10 20 30 40 50 60 70 80 90 100
Crystallite size [nm]
7
High-Purity Dispersible Alumina Hydrates DISPERAL/DISPAL
2.6 Acid Dispersible Boehmite
Dispersions of acid dispersible products may be formed in a similar fashion described above
by dispersing in dilute aqueous monovalent acids such as nitric, hydrochloric, formic or acetic
(typically < 1 wt.% acid) at pH 3–5.
2.7 Neutral to Alkaline Dispersible Boehmites
By changing the surface chemistry Sasol boehmites can also be stabilized under neutral and
alkaline conditions. By modification with lanthanum the iso-electric point can be shifted
to higher pH values, providing stability at pH 6–7. DISPERAL HP14/7 and DISPAL 18C9 are
surface modified with citric acid to provide colloidal stability at
pH 8–10. The stability of the dispersion is dependent on the absolute value of the zeta
potential (figure 6).
Figure 6:
Zeta potential curves of some 50
boehmites
40
30
20
[mV] 10
0
3 4 5 6 7 8 9 10 11 12
-10
-20 zeta-Potential -30
-40
-50
-60
pH
Lanthanum modified boehmite anionically modified boehmite
unmodified boehmite grey area: instable/no dispersion
2.8 Rheology
Rheological characteristics of boehmite dispersions can be affected by numerous factors. These
include product used, solid content, crystallinity, water quality, pH, ionic strength and other
formulation components. Figure 5 gives example curves of viscosity versus crystallite size for
some typical Sasol products. Also low-viscosity dispersions can be “thickened” by the addition
of acids, bases or salts to form thixotropic, shear-thinning systems (figure 7). This, for example,
allows boehmite to function as a thickener for many types of either acidic or basic formulations.
8
High-Purity Dispersible Alumina Hydrates DISPERAL/DISPAL
Figure 7:
Effect of boehmite concentration on
viscosity versus shear rate 4000
3500
3000
2500 (mP•s) 2000
1500 Viscosity 1000
500
0
20 %
0.1 15 %
1 10 %
10 5 %
Shear rate (1/s) 100 Solid content (wt.%)
2.9 Solvent Dispersible Boehmites
Sasol dispersible boehmites may be dispersed in organic solvents. Stable dispersions can be
prepared by dispersing the non-modified boehmite powder under intense mixing into the
solvent in presence of a stabilizing agent. For further, detailed information please contact
one of our representatives. Another option is the use of already surface-treated boehmites
that do not need further stabilization (figure 8). Different grades are available for polar and
non-polar solvents (see page 10).
Figure 8:
Schematic for a surface modified
boehmite and dispersion in ethanol R
(solid content 10 wt.%)
R R
SO3-
SO3- -O3S
+ + +
+ +
R SO3- + AIO (OH) + -O3S R
+ +
+ +
+
SO3- -O3S
SO3-
R R
R
9
High-Purity Dispersible Alumina Hydrates Technical Data
3. Technical Data
3.1 Water Dispersible Boehmites
Typical chemical DISPERAL DISPAL DISPAL DISPAL DISPAL DISPAL DISPAL DISPAL DISPAL
and physical properties P2 T25N4 25F4 23N4-80 18N4-80 14N4-80 11N7-80 10F4 8F4
Al2O3 [%] 72 78 78 80 80 80 80 83 83
NO3 [%] 4.0 4.5 – 1.6 1.1 0.7 0.1 – –
H3COO- [%] – – 2.0 – – – – 0.25 0.2
Loose bulk density [g/l] 850–1000 800 820 980 870 850 620 550 500
Particle size (d50) [μm] 45 30 30 50 50 50 40 30 30
Surface area (BET)** [m²/g] 260 >230 250 200 180 140 100 100 95
Pore volume** [ml/g] 0.5 0.4 0.4 0.4 0.5 0.5 0.8 0.8 0.7
Crystallite size (120) [nm] 4.5 7.0 8 9 15 18 30 40 53
Dispersed particle size*** [nm] 20 50 70 90 110 120 220 240 350
Dispersions of water dispersible products may be formed by simply stirring the powder in deionized water.
3.2 Acid Dispersible Boehmites
Typical chemical DISPERAL DISPERAL DISPERAL DISPERAL DISPERAL DISPERAL DISPERAL DISPAL
and physical properties 20 40 60 80 HP 14 HP 18 18HP
Al2O3 [%] 77 77 80 80 95 77 77 77
Loose bulk density [g/l] 400–600 500–700 400–600 300–500 200–500 300–500 300–500 300–500
Particle size (d50) [μm] 15 35 35 35 35 35 35 35
Surface area (BET)** [m²/g] 180 150 100 100 80 160 150 150
Pore volume** [ml/g] 0.5 0.7 0.8 0.9 0.9 1.1 1.2 1.2
Crystallite size (120) [nm] 10 20 40 50 65 14 18 18
Dispersed particle size***
Measured with PCS [nm] 80 150 250 350 500 100 150 200
Measured with [nm] 40 100 180 250 300 80 100 –
disc centrifuge
3.3 Surface Modified Boehmites
Typical chemical DISPERAL DISPERAL DISPAL DISPERAL DISPAL DISPAL
and physical properties HP 14 L1 HP 14/7 18C9 OS-1 25SR 25SRL
Al2O3 [%] 75 70 65 60
Surface treatment La-acetate Citric acid p-toluene sulfonic acid Dodecylbenzene sulfonic acid
Loose bulk density [g/l] 300–500 300–500 400–600 400–600
Particle size (d50) [μm] 35 35 35 35
Surface area (BET)** [m²/g] 150 150 240 240
Pore volume** [ml/g] 1.0 1.0 0.5 0.5
Crystallite size (120) [nm] 14 14 10 10
Stability [pH] 3–6 8–10 – –
Chemical purity: C: 0.25 %, SiO2: 0.01–0.015 %, Fe2O3: 0.005–0.015 %, TiO2: 0.01–0.15 % Further specialty grades are available upon request.
* Particle size as measured on the powder Analytical methods see page 14.
** Activation at 550 °C for 3 hours
*** 10 wt.% Al2O3 in 0.4 wt.% HNO3
Dispersions of acid dispersible products may be formed by dispersing in dilute aqueous monovalent acids (typically 1 wt.% acid)
such as nitric, hydrochloric, formic, lactic or acetic acid.
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High-Purity Dispersible Alumina Hydrates Technical Data
11
High-Purity Dispersible Alumina Hydrates Product Information/Certifications
4. Product Information
4.1 Storage and Transfer
DISPERAL and DISPAL boehmite powders are mildly abrasive materials having a Mohs
hardness of 3.5 to 4.0. Therefore, handling and storage equipment should be designed for such
materials. Examples are aluminium, abrasion resistant carbon steel and polypropylene or epoxy-
lined steel. Blower or vacuum systems can be used to move the powders.
A minimum of 4,000 ft/min fluidizing velocity is recommended. Boehmite powders will absorb
atmospheric moisture and facilities should be designed appropriately. The liquids are readily
pumpable using standard centrifugal or positive displacement pumps. Due to the pH range of
available products, recommended materials for process equipment include stainless steel, or
polymeric-lined steel.
4.2 Safety and Handling
DISPERAL and DISPAL boehmite powders are classified as non-toxic nuisance dusts. Exposure
to high concentrations of dust may cause physical irritation and drying of skin and eye
tissues. Repeated or prolonged contact with alumina sols may cause irritation as well.
Handling and shipping procedures should be designed to avoid such contact and to minimize
the inhalation of airborne dust. Normal good laboratory practices and operating procedures
should ensure personnel safety. See also corresponding material data safety sheet.
4.3 Technical Support
The Sasol alumina organization is committed to offering the technical service necessary to
ensure customer satisfaction. Technical support is available worldwide to aid you in choosing
the best alumina for your needs, as well as for providing advice on safe and efficient use. The
products described in this brochure give some indications of our total capability. We look
forward to discussing specific technical requirements with you.
5. Certifications
All Sasol Performance Chemicals locations worldwide are certified to DIN ISO 9001/14001
and to OHSAS 18001 standards (Occupational, Health and Safety Assessment Series), and
the German plants additionally comply with EMAS III (Eco Management and Audit Scheme).
Our production sites operate according to an internationally recognised, integrated quality,
environmental and safety management system that has been established at the sites for
many years.
12
High-Purity Dispersible Alumina Hydrates Product Information/Certifications
13
High-Purity Dispersible Alumina Hydrates Analytical Methods
6. Analytical Methods
6.1 Crystallite Size
Crystallite dimensions in powdered boehmite samples are analyzed using X-ray diffraction
techniques on X-ray diffractometers supplied by Siemens or Philips.
6.2 Dispersed Particle Size
The particle size distribution of diluted boehmite sols and dispersions is measured using
laser diffraction or photon correlation spectroscopy techniques on Malvern, Horiba or Cilas
instruments. Alternatively dispersed particle sizes can be measured using a disk centrifuge
supplied by CPS.
6.3 Dispersibility of Boehmite Powder
A specified amount is added to water or dilute acid under stirring. The mixture is then stirred
for a specified period of time to form a dispersion. The dispersion is centrifuged, and the
undispersed residue is isolated, dried and weighed to determine the percentage of non-
dispersed material.
6.4 Surface Area
The boehmite is first calcined at 550 °C for three hours in preparation for analysis. Alumina
surface area is then measured using BET nitrogen adsorption techniques on instruments
supplied by Quantachrome (Nova series) or by Micromeritics (Gemini series).
6.5 Trace Element Analysis
Trace element analysis is performed by using several methods, including X-ray fluorescence of
pressed alumina disks and wet techniques (ICP/OES).
6.6 Pore Volume and Pore Size Distribution
The boehmite is first calcined at 550 °C for three hours in preparation for analysis. The
porosity is measured by nitrogen desorption using Autosorb instruments supplied by
Quantachrome.
14
High-Purity Dispersible Alumina Hydrates Analytical Methods
15
At Your Service
Sasol Performance Chemicals
Advanced Materials
Anckelmannsplatz 1, 20537 Hamburg, Germany
Telephone +49 40 63684 1000 Fax +49 40 63684 3700
inorganics@de.sasol.com
Sasol Germany GmbH
Anckelmannsplatz 1, 20537 Hamburg, Germany
Telephone +49 40 63684 1245 Fax +49 40 63684 3626
inorganics@de.sasol.com www.sasolgermany.de
Sasol Chemicals North America LLC
12120 Wickchester Lane, Houston, Texas 77079-2990, USA
Telephone +1 281 588 3000 Fax +1 281 588 3589
inorganics@us.sasol.com www.sasolnorthamerica.com
Sasol Chemicals Japan KK
P.O. Box 46 St. Luke’s Tower 35 F, 8-1 Akashicho Chuo-ku, Tokyo 104-6591, Japan
Telephone +81 (3) 3248 6711 Fax +81 (3) 3248 6715
adm@sasoljapan.com
US
www.sasolalumina.com www.sasol.com 08/18
Hydrates
Source reference
Cover: Sasol Germany GmbH, p. 3: Sasol Ltd., p. 5, p. 9, p. 11, p. 13, p. 15: Sasol Germany GmbH Alumina
Sasol is a registered trademark of Sasol Ltd. Product trademarks displayed in this document are the
property of the Sasol Group of companies, except where it is clear from the context that not. Users of
this document are not permitted to use these trademarks without the prior written consent of their
proprietor. All rights not expressly granted are reserved.Disclaimer: The information contained in this document is based on Sasol`s knowledge and experience Dispersible
at the time of its creation. We reserve the right to make any changes to this document or the products
described therein, as a result of technological progress or developments. This information implies no
liability or other legal responsibility on our part, including with regard to existing third-party patent
rights. In particular, no guarantee or warranty of properties in the legal sense is implied. The customeris not exempted from the obligation to conduct careful inspection and testing of incoming goods. High-Purity
Reference to trademarks used by other companies is neither a recommendation, nor should it give the –
impression that products of other companies cannot be used. All our business transactions are governed
exclusively by our General Business Conditions. DISPAL
DISPERAL