Hydrotalcites
P.O. Box 6, Clifton Junction, Swinton,
Manchester M27 8LS, England.
Magnesium Elektron Inc., 500 Point Breeze Rd,
Flemington, NJ 08822, USA
Hazel Stephenson, Heather Bradshaw,
MEL Chemicals, Clifton Junction, Swinton, Manchester M27 8LS, England.
Nikkei-MEL, 4025-1, Shimizu-Miho, Shizuoka City,
Shizuoka Prefecture, 424-0901, Japan.
A Luxfer Group Company
In 2006 we began development on a
range of hydrotalcites. To date we have
been focusing our development on
products primarily for use as carbon
dioxide sorbants to complement our
melsorb product range, however there
are a wide variety of applications that
can use hydrotalcites, examples include:
Additives for polymers
Anion exchange
Antacids
Catalysts
Catalyst supports
Nuclear waste treatment
Sorbants
Water purification
Hydrotalcites are formed in nature by the
weathering of basalts or from precipitation
in saline water sources, they are of the
general formula:
•
•
•
•
•
•
•
•
[M2+1-x M3+x(OH)2x]x+ (An- )x/n.mH2O
M2+ is typically Mg but can be Ni, Zn, Cu.
M3+ is typically Al but can be Cr, Mn, Co, Fe.
A is any anion.
gentle calcination, the double layered
hydroxide structure can be regenerated
by exposure to anions, hence use as
regenerable CO2 sorbants.
The mixed oxides resulting from
calcinations of hydrotalcites can be useful
in catalytic applications, due to their high
surface area and large pores, but also the
distribution of metals on the surface.
Products
Using our experience in the preparation
of mixed oxides we have been working
on process improvements to the standard
preparation techniques, aiming to give
improved impurity removal, increased
surface area stability and particle size
control. We have developed a product
called XZO 1679/01 which has a Mg : Al : Zr
2.5 of 3:0.78 0.14.
ratio
Characterisation
2.0
Calcination
1.5
condition
(°C
/ hrs)
1.0
Surface Area
(m2/g)
Total pore
volume
(ml / g)
Dried
67
0.27
Wt% CO2
Introduction
0.5
400/2
225
0.0
0
450/2
Anions
Water molecules
M2+ or M3+
OH-
100
0.60
150
193
250
0.66 300
200
Time (mins)
500/2
177
0.58
700/2
157
0.73
1.2
Samples
Laboratory samples of XZO 1679/01 up to
500g and pilot plant samples up to 5kg are
available on request. For larger quantities,
or information on other compositions that
are available please contact:
[email protected] or our
agents O.C. Lugo, at [email protected].
0.6
1.5
0.4
1.0
References
0.2
0.5
0.0
1. Tsuji, M. et al. Hydrotalcites with an extended
Al3+ substitution: Synthesis, simultaneous
TG-DTA-MS study, and their CO2 adsorption
behaviors. J. Mater. Res.,1993 8(5).
2. Velu, S. Ramaswamy, V. Ramani, A. New
hydrotalcite-like anionic clays containing Zr4+
in the layers. Chem. Commun,. 1997, 2107.
3. Tichit, D et al, Preparation of Zr containing
Layered Double Hydroxides and characterization
of the acido-basic properties of their mixed
oxides, Chem. Mater. 2002, 14, 1530-1538.
4. Braterman, P.S. Xu, Z.P, Yarberry, F. Layered
Double Hydroxides. (LDHs) Handbook of
Layered Materials.
5. Das, N.N. et Al, Adsorption of Cr(VI) and
Se(IV) from their aqueous solutions onto Zr4+
substituted ZnAl/Mg/Al-layered double
hydroxides: effect of Zr4+ substitution.
Colloid and interface science 2004 1-8.
6. Velu. S. et al. Selective production of hydrogen
from fuel cells via oxidative steam reforming
of methanol over CuZrAl(Zr) oxide
catalysts. Applied Cat. 2001, 213 47.
2.0
0.8
0.0
0
0
5
50
10
15
Time (mins)
100
150
200
250
Time (mins)
20
300
Counts
Wt% CO2
M+ and M4+ metals can be used to part
substitute M2+ or M3+, this enables fine
Figure 2: Uptake of CO2 at 25ºC for XZO 1679/01
tuning of the product to suit specific
applications by reducing or increasing the
5000
overall positive charge, and thus the capacity
1.2
Aged 0700/2
for anions, basisity and catalytic activity.
4000
1.0
Aged 0500/2
Another interesting property of hydrotalcites
3000
is their memory effect, after relatively
0.8
Aged 0450/2
2000
0.6
Aged 0400/2
1000
0.4
0
0.2
As Received
10
20
30
40
50
60
70
º2 Theta
0.0
0
5
10
15
1679/01
Figure 3: XRD of XZOTime
(mins)
20
5000
Aged 0700/2
4000
Counts
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•
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•
•
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•
MEL Chemicals / MEI would like to thank
Dr Alexei Lapkin ([email protected]) and
Alina Iwan at Bath University for their help
measuring CO2 sorption, SEM and
continued support in CO2 sorption projects.
2.5
1.0
NO3- < Br- < Cl- < F- < OH- < SO42< CrO42- < HAsO42- < HPO42- < CO32-
Hydrotalcites can be used in a variety of
applications. Modifying the structure by
addition of zirconia and / or alternative
metals gives us the ability to tailor the
product properties to suit the specific
application.
Tuneable properties include:
Activity of supported metal
Basisity
Capacity
Kinetics: sorption/ion exchange
Particle size
Selectivity
Surface area
Acknowledgments
Figure 1: Table of data for XZO 1679/01
CO2
Wt% COWt%
2
Hydrotalcites are useful in such a variety
of applications due to their layered double
hydroxide structure (LDH). The cations
create an overall positive charge in the
layers, which is balanced by the presence
of anions in the interlayer. These anions in
the interlayer can be exchanged, the order
of preference typically being:
50
Figure 4: SEM of XZO 1679/01
Summary
Aged 0500/2
3000
Aged 0450/2
2000
Aged 0400/2
1000
As Received
0
10
20
30
40
º2 Theta
50
60
70