ZEOLITE ADSORBENTS HAVING A HIGH EXTERNAL SURFACE AREA AND USES
THEREOF
s [OOOI] The invention relates to the use of zeolite adsorbent materials in agglomerated
form comprising at least one faujasite zeolite, said adsorbents having a high external
surface area characterized by nitrogen adsorption, and a high micropore volume, for gas
phase separation, in particular in pressure swing processes, either of PSA (pressure swing
adsorption) type, or of VSA (vacuum swing adsorption) type, or of VPSA (hybrid process of
lo the previous two), or of RPSA (rapid pressure swing adsorption) type, in temperature swing
processes of TSA (temperature swing adsorption) type andlor in pressure and temperature
swing processes of PTSA (pressure and temperature swing adsorption) type.
[0002] The present invention also relates to a process for gas separation and purification
using said zeolite adsorbents having a high external surface area.
is [0003] The invention also relates to zeolite adsorbent materials that can be used in the
context of the present invention having a high external surface area and comprising lithium
andlor calcium andlor sodium.
[0004] The use of agglomerates of this type is particularly advantageous in applications
where the transfer kinetics, the volumetric adsorption capacity, which are determining
20 parameters for the overall efficiency and productivity of the process, and also low pressure
drops are desired.
[0005] In adsorption separation techniques, a great deal of effort has been given over the
past few years to increasing the hourly productivity of the adsorbent beds, in particular by
increasing the adsorptionldesorption cycle frequency, which means that the adsorbent
25 used, in addition to its thermodynamic adsorption properties, must be able to become
saturated by adsorption and to release the adsorbed gas on desorption in increasingly short
time periods. The adsorbents must thus be designed so as to have the most efficient mass
transfer possible, that is to say such that the gases to be separated or to be purified reach
the adsorption sites as rapidly as possible and are also desorbed as rapidly as possible.
30 [0006] Several paths have been explored in order to achieve this objective. The first
method proposed by the literature consists in decreasing the size of the adsorbent particles.
It is generally accepted that the effect of this is to enable a more rapid diffusion of the gases
in the macroporous network, the kinetic constant for transfer of matter being inversely
proportional to the square of the diameter of the particles (or equivalent dimension,
35 depending on the morphology of the adsorbents. Mention will for example be made of the
article "Adsorbenf particle size effects in the separation of air by rapid pressure swing
adsorption", by E. Alpay et al., Chemical Engineering Science, 49(18), 3059-3075, (1 994).
[0007] Document WO 20081152319 describes the preparation, by spray-drying, of
mechanically strong adsorbents of small sizes, which are for example used in portable
5 concentrators of medical oxygen, as shown by document US 201310216627. The main
drawback of reducing the size of the adsorbent particles is the increase in the pressure
drops in adsorbents and the high energy consumption that is associated therewith. This is
particularly unacceptable in industrial gas production adsorption processes.
[0008] The second method consists in improving the intra-granular transfer capability of
l o the adsorbents, without changing the size thereof. International applications WO 99143415,
WO 99143416, WO 99143418, WO 20021049742 and WO 20031004135 describe
adsorbents with improved kinetics, obtained by conversion of the agglomeration binder into
zeolite active matter and also the associated gas separation processes, which are more
efficient than with conventional particles.
15 [0009] Document WO 20081051904 proposes a process for producing, by
extrusionlspheronization of beads of zeolite adsorbents based on zeolite LiX with improved
diffusion. Document WO 20081109882 describes, for its part, the preparation of high crushstrength
adsorbents with improved mass transfer from UX 06 LiLSX zeolites and less than
15Oh of siliceous binder introduced in colloidal form.
20 [OOIO] Application EP 1 240 939 proposes selecting, for uses in a PSA or VSA process,
adsorbents having a certain ratio between their kinetic transport constants for adsorbable
compounds in the gas phase and in the solid phase. Document US 6 328 786 defines a
minimum threshold of mechanical strength and a kinetic coefficient above which the
adsorbents are preferred for use in a PSA process. Application EP 1 048 345 describes
2s high-macroporosity adsorbents produced by means of a spheronization and lyophilization
technique.
[OOII] A third method consists in improving the access to the adsorbent by using various
forming geometries combining both reduced active material thicknesses and sufficiently
wide fluid passage cross-sections to allow a flow with limited pressure drops. Mention may
30 be made of adsorbent sheets and fabrics, monoliths of bee's nest type, foams or the like.
[0012] Document FR 2 794 993 proposes using heterogeneous beads, with an adsorbent
of peripheral layer of small thickness coating an inert core: the diffusion distance is thus
reduced, without increasing the pressure drops. This system has the defect of having a low
volumetric efficiency: a significant part of the adsorber is taken up by matter which is ineri
35 in terms of adsorption, which has a considerable impact in terms of facility sizes and thus
of investments, or even of weight, which can be bothersome, in the case of portable
purificationlseparation equipment, for instance medical oxygen concentrators.
[0013] Patent applications US 201210093715 and US 201310052126 teach that it is
possible to form monolithic zeolite structures with a hierarchical structure, by adding a
s polymer to the synthesis reaction medium: as for the adsorbent sheets and fabrics, the
solids obtained have a very high macropore volume and a very high mesopore volume,
these solids are thus not very dense and their volumetric efficiency is low, owing to their low
volumetric adsorption capacity.
[0014] Thus, all these adsorbent geometries of various natures pose problems in terms
lo of relatively complex processing, of mechanical fatigue or wear resistance and of low
volumetric efficiency, since the active matter content is often reduced to the benefit of inert
binders or other mechanical reinforcement fibers or since the materials obtained are not
very dense.
[0015] There thus remains a need for zeolite adsorbents that are of use for the separation
is and purification of gases having good transfer properties which do not have the drawbacks
associated with the use of the prior art adsorbents. In particular, there remains a need for a
zeolite adsorbent having greater adsorption capacities and better adsorptionldesorption
kinetics, allowing in particular a more intensive use of processes, and in particular PSA,
TSA or VPSA processes.
20 [0016] The inventors have now discovered that the abovementioned objectives can be
totally or at least partially achieved by virtue of adsorbents specifically devoted to gas
separation and puiiication uses as will be described now.
[0017] Thus, and according to a first aspect, the invention relates to the use, for gas
separation, of at least one zeolite adsorbent material comprising at least one FAU zeolite,
2s said adsorbent having:
an external surface area, measured by nitrogen adsorption and expressed in m2 per
gram of adsorbent greater than 20 m2.g-l, and preferably between 20 m2.g-' and 300
m2.g-l, and more preferably between 30 m2.g-' and 250 m2.g-' and even more preferably
between 40 m2.g-I and 200 m2.g-', and most particularly between 50 m2.g-' and 200 m2.g-
30 '
e a non-zeolite phase (PNZ) content such that 0 < PNZ r 30%, preferably 3% 5 PNZ 5
25%, more preferably 3% r PNZ 5 20%, advantageously 5% 5 PNZ 5 20%, even better
still 7% r PNZ 5 18%, measured by XRD (X-ray diffraction), by weight relative to the total
weight of the adsorbent,
a mesopore volume (Vmeso) of between 0.08 cm3.g-' and 0.25 cm3.g-', preferably
between 0.08 cm3.g-' and 0.22 cm3.g-', and more preferably between 0.09 cm3.g-' and
0.20 cm3.g-', more preferably between 0.10 cm3.g-' and 0.20 cm?g-', limits included,
and an SiIAI atomic ratio of the adsorbent of between 1 and 2.5, preferably between 1
5 and 2.0, more preferably between 1 and 1.8 and entirely preferably between 1 and 1.6,
all of the measurements being carried out on the adsorbent material at least 95%
exchanged with sodium.
[0018] In the present description, the term "FAU zeolite" denotes a faujasite zeolite,
advantageously a mesopore faujasite zeolite chosen from zeolites of LSX, MSX, X and Y
10 type and mixtures thereof. According to one embodiment, the zeolite adsorbent material
can also comprise one or more other zeolite(s) chosen from FAU zeolites (LSX, MSX, X,
Y), LTA zeolites, CHA zeolites (chabazite), HEU zeolites (clinoptilolite), and mixtures of two
or more of them, and more preferably from LSX, MSX and X zeolites, and mixtures of two
or more of them.
15 [0019] Other zeolites may be present in minor amounts in the adsorbents of the invention
or usable in the process of the invention. These zeolites can be considered to be pollutants,
in particular because they do not contribute to gas adsorption, in other words they are inert
with respect to gas adsorption. By way of nonlimifing examples, these zeolites comprise
sodalite, hydroxysodalite, zeolite P, and other zeolites thai are inert with respect to gas
20 adsorption.
[0020] The various types of zeolites present in the zeolite adsorbent material are
determined by XRD. The amount of zeolites is also measured by XRD and is expressed as
% by weight relative to the total weight of the adsorbent material.
[0021] Consequently, in the present invention, the term "non-zeolite phase" (or "PNZ")
2s denotes any phase present in the adsorbent material, other than the zeolite(s) defined
above, called "zeolite phase" or "PZ". The amount of non-zeolite phase is expressed by the
amount to be added to the zeolite phase of the adsorbent to make the total up to loo%, in
other words:
%PNZ = 100 - %PZ,
30 where %PNZ represents the percentage by weight of PNZ and %PZ the percentage by
weight of zeolite phase, relative to the total weight of the adsorbent.
[0022] The expression "adsorbent at least 95% exchanged with sodium" is intended to
mean that at least 95% of the exchangeable catatonic sites of the zeolite phase are taken
up by sodium cations.
35 100231 This zedite adsorbent material at least 95% exchanged with sodium can be
obtained and preferably is obtained according to the following protocol: the zeolite
adsorbent material to be exchanged with sodium is introduced into a solution of sodium
chloride at 1 mol of NaCl per liter, at 90°C, for 3 hours, with a liquid-to-solid ratio of 10 m1.g-
'. The operation is repeated n times, n being at least equal to 1, preferably at least equal to
2, preferably at least equal to 3, more preferably at least equal to 4.
5 [0024] The solids resulting from the exchange operations n-1 and n are successively
washed four times by immersion in water in a proportion of 20 m1.g-' in order to remove the
excess salt, and then dried for 12 hours at 80°C in air, before being analyzed by X-ray
fluorescence. If the weight percentage of sodium oxide of the zeolite adsorbent material,
between the exchange operations n-I and n, is stable at i. I%, said zeolite adsorbent
lo material is considered to be "in its form at least 95% exchanged with sodium". Where
appropriate, additional exchanges are carried out as described above until stability of the
weight percentage of sodium oxide of + 1% is obtained.
[0025] It will in particular be possible to carty out successive batchwise cationic
exchanges, with a large excess of sodium chloride, until this weight percentage of sodium
15 oxide of the zeolite adsorbent material, determined by X-ray fluorescence chemical
analysis, is stable at ? 1%. This method of measurement is explained below in the
description. As a variant, the zeolite adsorbent material can already be intrinsically in its
sodiumexcbanged form afier the synthesis step when the latter is carried out exdusivety in
an alkaline sodium medium.
20 [0026] The SilAl atomic ratio of the zeolite adsorbent material is measured by X-ray
fluorescence elemental chemical analysis, a technique well known to those skilled in the art
and explained below in the description. If necessary, the sodium exchange is carried out
before analyses according to the procedure described in detail above.
[0027] The term "Vmicro" is intended to mean the micropore volume of the zeolite
25 adsorbent material, the measurement technique of which is explained below. The term
"Vmeso" is intended to mean the mesopore volume of the zeolite adsorbent material, the
measurement technique of which is explained below.
[0028] According to one preferred embodiment, said at least one zeolite adsorbent
material that can be used in the context of the present invention has a (Vmicro -
30 Vmeso)Nmicro ratio of between -0.5 and 1 .O, limits not included, preferably between -0.1
and 0.9, limits not included, preferably between 0 and 0.9, limits not included, more
preferably between 0.2 and 0.8, limits not included, more preferably between 0.4 and 0.8,
limits not included, preferably between 0.6 and 0.8, limits not included, where Vmicro is the
micropore volume measured by the Dubinin-Raduskevitch method and. Vmeso is the
35 mesopore volume determined by the Barren-Joyner-Halenda (BJH) method, all of the
measurements being carried out on the adsorbent material at least 95% exchanged with
sodium.
[0029] According to yet another embodiment, said at least one zeolite adsorbent material
has a micropore volume (Vmicro, or else Dubinin-Raduskevitch volume), expressed in cm3
s per gram of adsorbent material, of between 0.210 cm3.g-' and 0.360 cm3.g-I, preferably
between 0.230 cm3.g-' and 0.350 cm3.g-', preferably between 0.240 cm3.g-I and 0.350
cm3.g-I, more preferably 0.250 cm3.g-I and 0.350 cm3.g-I, measured on the adsorbent
material at least 95% exchanged with sodium
[0030] On the basis of the micropore volume according to Dubinin-Raduskevitch
10 measured on the zeolite adsorbent material exchanged with sodium, it is also possible to
calculate an overall Dubinin-Raduskevitch volume of FAU zeolite(s), which is PNZweighted.
[0031] The total volume of the macropores and mesopores of the zeolite adsorbent
materials that can be used in the context of the present invention, measured by mercury
1s intrusion, is advantageously between 0.1 5 cm3.g-I and 0.5 cm3.g-I, preferably between 0.20
cm3.g-' and 0.40 cm3.g-I and very preferably between 0.20 cm3.g-I and 0.35 cm3.g-',the
measurements being carried out on the adsorbent material at least 95% exchanged with
sodium.
[0032] The volume fraction of the macropores of the zeolite adsorbent material that can
20 be used in the context of the present invention is preferably between 0.2 and 1.0 of the total
volume of the macropores and mesopores, very preferably between 0.4 and 0.8 and even
more preferably between 0.45 and 0.65, limits included, the measurements being carried
out on the zeolite adsorbent material at least 95% exchanged with sodium.
[0033] The zeolite adsorbent materials that can be used in the context of the present
2s invention are either known or can be prepared using known procedures, or else are novel
and in this respect are an integral part of the present invention.
100341 According to yet another preferred embodiment, the use according to the invention
employs a zeolite adsorbent material comprising at least one mesoporous FAU zeolite. The
term "mesoporous" is intended to mean a zeolite which has, togetherwith the microporosity
30 inherent in the structure of the zeolite, internal cavities of nanometric size (mesoporosity),
easily identifiable by observation using a transmission electron microscope (TEM), as
described for example in US 7 785 563.
[0035] More specifically, said FAU zeolite of the zeolite adsorbent material is a
mesoporous FAU zeolite, that is to say a zeolite having an external surface area, defined
35 by the t-plot method described below, of between 40 m2.g-' and 400 m2.g-I, preferably
between 60 m2.g-' and 200 m2.g-', limits included. By extension, for the purposes of the
present invention, a "non-mesoporous zeolite" is a zeolite optionally having an external
surface area, defined by the t-plot method described below, of strictly less than 40 m2.g-'.
[0036] In particular, the zeolite adsorbent materials that can be used in the context of the
present invention comprise at least one FAU zeolite, said at least one FAU zeolite having
s an SiIAI ratio corresponding to the inequation 1 5 SiIAI < 1.5, preferably 1 2 SilAI r 1.4, and
more preferably an SilAl atomic ratio equal to 1.00 +I- 0.05, said SiIAI ratio being measured
by solid silicon 29 nuclear magnetic resonance of (29Si NMR), according to the techniques
well known to those skilled in the art.
[0037] The SilAl ratio of each of the zeolite(s) present in the adsorbent is also measured
lo by NMR of the solid.
[0038] According to one preferred embodiment, the FAU zeolite of the zeolite adsorbent
material is in the form of crystals, the number-average diameter of which, measured using
a scanning electron microscope (SEM), is less than 20pm, preferably between 0.1 pm and
20 pm, preferably between 0.1 and 10 pm, preferably between 0.5 pm and 10 pm, more
is preferably between 0.5 pm and 5 pm, limits inciuded.
[0039] According to yet another preferred embodiment, said zeolite adsorbent material
comprises at least one cation chosen from the ions of groups IA, IIA, IIIA, IB, 118 and Ill6 of
the periodic table, the trivalent ions of the lantbanide or rare earth series, the zinHll) ion,
the silver(!) ion, the cupric (11) ion, the chromium(lll) ion, the ferric (111) ion, the ammonium
20 ion andlor the hydronium ion, the preferred ions being calcium, lithium, sodium, potassium,
barium, cesium, strontium, zinc and rare-earth ions and more preferably sodium, calcium
and lithium ions.
[0040] According to one embodiment, the zeolite adsorbent material that can be used in
the context of the present invention comprises at least one alkali or alkaline-earth metal
2s chosen from sodium, calcium, lithium, and mixtures of two or three of them in any
proportions, the contents of which, expressed as oxides, are preferably such that:
the CaO content is between 0% and 20.5% by weight relative to the total weight of the
zeolite adsorbent material, preferably between 3% and 20.5% by weight relative to the
total weight of the zeolite adsorbent material, preferably between 7.5% and 20.5% by
30 weight relative to the total weight of the zeolite adsorbent material, and preferably
between 9% and 20.5% by weight relative to the total weight of the zeolite adsorbent
material, limits included,
the Li20 content is between 0% and 12% by weight relative to the total weight of the
zeolite adsorbent material, preferably between 3% and 12% by weight relative to the total
35 weight of the zeolite adsorbent material, preferably between 5% and 12% by weight
relative to the total weight of the zeolite adsorbent material, and preferably between 6.5%
and 12% by weight relative to the total weight of the zeolite adsorbent material, limits
included, . the NazO content is between 0% and 22% by weight relative to the total weight of the
zeolite adsorbent material, preferably between 0% and 19% by weight relative to the total
5 weight of the zeolite adsorbent material, preferably between 0% and 15% by weight
relative to the total weight of the zeolite adsorbent material, preferably between 0% and
10% by weight relative to the total weight of the zeolite adsorbent material, and entirely
preferably between 0% and 7% by weight relative to the total weight of the zeolite
adsorbent material, advantageously between 0% and 2% by weight relative to the total
10 weight of the zeolite adsorbent material, limits included,
e it being understood that the zeolite adsorbent material comprises at least one of the three
metals chosen from lithium, sodium and calcium,
= said zeolite adsorbent material possibly also comprising at least one rare earth, chosen
from lanthanides and actinides, preferably from lanthanides, in a content of generally
1s between 0% and lo%, preferably between 0% and 7%, . said zeolite adsorbent material possibly also comprising, in small amounts (%expressed
as oxide, less than 5%, preferably less than 2%). one or more cations other than lithium,
sodium and caldum, for example and preferably chosen from potassium, barium,
strontium, cesium, transition metals such as silver, and the like.
20 [0041] According to the present invention, the zeolite adsorbent materials described
above are most particularly useful, suitable and effective in processes for gas-phase
separation, in particular in pressure andlor temperature swing processes, either of PSA
type, or of VSA type, or of VPSA type, or of RPSA type, or of TSA type andlor in processes
of PTSA type.
25 [0042] More specifically, the present invention relates to the use of at least one zeolite
adsorbent material comprising at least one FAU zeolite, as defined above, for gas
separation. The term "gas separation" is intended to mean purifications, pre-purifications,
eliminations, and other separations of one or more gas compounds present in a mixture of
one or more gas compounds.
30 [0043] According to one preferred aspect of the present invention, the zeolite adsorbent
materials that can be used for the gas purification are materials which only generate a slight
pressure drop or pressure drops that are acceptable for the abovementioned uses.
[0044] Preference is thus given to the agglomerated and formed zeolite adsorbent
materials prepared according to any techniques known to those skilled in the art, such as
35 extrusion, compacting, agglomeration on a granulating plate or granulating drum,
atomization and the like. The proportions of agglomeration binder and of zeolites used are
typically those of the prior art, that is to say between 5 parts and 30 parts by weight of binder
per 95 parts to 70 parts by weight of zeolite.
[0045] The zeolite adsorbent material that can be used in the context of the present
invention, whether it is in the form of balls, extruded pieces or the like, generally has a
5 volume mean diameter, or a mean length (largest dimension when it is not spherical), of
less than or equal to 7 mm, preferably between 0.05 mm and 7 mrn, more preferably
between 0.2 mm and 5 mm and more preferentially between 0.2 mm and 2.5 mm.
[0046] The zeolite adsorbent materials that are of use in the context of the present
invention also have mechanical properties that are most particularly suitable for the
10 applications to which they are intended, that is to say:
a either a bulk crush strength (BCS) in a bed, measured according to standard ASTM
7084-04, of between 0.5 MPa and 3 MPa, preferably between 0.75 MPa and 2.5 MPa,
for a material having a volume mean diameter (050) or a length (largest dimension when
the material is not spherical), of less than 1 mm, limits included,
15 or a single pellet crush strength, measured according to standards ASTM D 4179 (201 1)
and ASTM D 6175 (2013), of between 0.5 daN and 30 daN, preferably between 1 daN
and 20 daN, for a material having a volume mean diameter (D50) or a length (largest
dimension when the material is no$ spherical), greater than or equal to 1 mm, limits
included.
20 I00471 According to another preferred embodiment, the use according to the invention
uses at least one zeolite adsorbent material having a high volumetric adsorption capacity,
that is to say a volumetric micropore volume expressed in ~ m ~ . c mof -a~ds orbent material
at least 95% exchanged with sodium, said micropore volumetric volume being greater than
0.10 ~ m ~ . c mp-re~f,e rably greater than 0.12 ~ m ~ . c mm-o~re, preferably greater than 0.15
25 ~m~.cm-~,mporreefe rably greater than 0.16 ~ m ~ . c mm-o~re, preferably greater than 0.18
~ m ~ . c me-n~tir,e ly preferably greater than 0.20 ~ m ~ . c m - ~ .
100481 According to yet another embodiment, the use according to the invention
preferably uses at least one zeolite adsorbent material having a loss on ignition, measured
at 950°C according to standard NF EN 196-2, of between 0% et 5%, preferably between
30 0% and 3% by weight.
[0049] In particular, the present invention relates to the use of at least one zeolite
adsorbent material as has just been defined, for purifying natural gas, in particular for
removing the impurities and preferably for removing the carbon dioxide andlor the
mercaptans, present in natural gas, and in particular according to pressure andlor
35 temperature swing adsorption (PSA or TSA or PTSA) processes, preferably TSA or PTSA
processes. It is in particular preferred to use, for these types of applications, the adsorbent
materials comprising an FAU zeolite, which is preferably mesoporous, of the type chosen
from NaX and CaX, and mixtures thereof.
[0050] For these types of applications, preference is given to a zeolite adsorbent material
of which the volume mean diameter (or the longest length) is between 0.3 mm and 7.0 mm,
s preferably between 0.8 mmand 5.0 mm, and more preferably between 2.0 mm and 5.0 mm,
limits included.
/0051] According to another embodiment, the present invention relates to the use of at
least one zeolite adsorbent material as has just been defined, for the noncryogenic
separation of industrial gases and of gases in the air, and in particular for nitrogen
l o adsorption in the separation of gas from the air, in particular for the enrichment of oxygen
in the air. This use is most particularly suitable in pressure swing adsorption (PSA) devices
according to very short cycles (typically between 0.1 second and 10 seconds, preferably
between 0.1 second and 5 seconds), and in particular in oxygen concentrators for
respiratory assistance, as described for example in application WO 200811 5231 9.
15 [0052] In the case of the use according to the invention for the noncryogenic separation
of industrial gases and of gases in the air, these processes are well known from the prior
art, and in particular from document EP 0 893 157 which describes, generally, gas
separationJpurifjdton processes by means of zeolite adsorbenis.
[0053] For the applications of noncryogenic separation of industrial gases and of gases in
20 the air and preferably of nitrogen separation for oxygen enrichment, preference is also given
to the zeolite adsorbent material comprising at least one FAU zeolite, which is preferably
mesoporous, of the type chosen from NaX, LiX, CaX, LiCaX, NaLSX, LiLSX, CaLSX,
LiCaLSX, and mixtures of two or more of them, said zeolite adsorbent material comprising
at least one alkali or alkaline-earth metal chosen from sodium, calcium, lithium, and
25 mixtures of two or three of them in any proportions, the contents of which expressed as
oxides are as defined above.
I00541 More particularly, the use described above is most particularly suitable for nitrogen
separation for oxygen enrichment, and most particularly for use in oxygen concentrators for
respiratory assistance. In these cases, it is preferred to use at least one zeolite adsorbent
30 material comprising sodium, calcium andlor lithium, alone or as a mixture, and it is most
particularly preferred; for these types of applications, to use a zeolite adsorbent material
comprising at least one FAU zeolite, which is preferably mesoporous, of the type chosen
from NaX, LiX, CaX, LiCaX, NaLSX, LiLSX, CaLSX and LiCaLSX, and mixtures of two or
more of them, preferably from CaLSX, LiLSX and LiCaLSX, more preferably at least one
35 LiLSX zeolite, preferably mesoporous LiLSX zeolite.
[0055] For applications for the separation of industrial gases and of gases in the air in
general, a zeolite adsorbent material in the form of balls of which the mean volume diameter
is between 0.05 mm and 5 mm, preferably between 0.05 mm and 3.0 mm, more preferably
between 0.05 mm and 2.0 mm, is preferred.
5 I00561 For specific applications of oxygen enrichment of air, for example oxygen
concentrators for respiratory assistance, a zeolite adsorbent material in the form of balls of
which the mean volume diameter is between 0.05 mm and 1 mm, preferably between 0.1
mm and 0.7 mm, more preferably between 0.3 mm and 0.6 mm, is preferred.
[0057] According to another embodiment, the invention relates to the use of at least one
10 zeolite adsorbent material as has just been defined, for the purification of syngas. An
example of a process for purifying syngas is described in patent EP 1 312 406. The
syngases targeted here are in particular syngases that are based on hydrogen and carbon
monoxide andlor on hydrogen and nitrogen, and more particularly mixtures of hydrogen
and carbon monoxide andlor of hydrogen and nitrogen, these syngases possibly also
15 containing, or being polluted with, carbon dioxide and one or more possible other impurities,
for instance, and in a nonlimiting manner, one or more impurities chosen from nitrogen,
carbon monoxide, oxygen, ammonia, hydrocarbons and oxygen-comprising derivatives, in
particular alkanes, in particular methane, alcohols, in particular methanol, and others.
[0058] The use according to the present invention is thus most particularly suitable for
20 removing nitrogen, carbon monoxide, carbon dioxide, methane, and other impurities,
preferably by pressure swing adsorption (PSA) processes, for hydrogen production. For
these types of applications, adsorbent materials comprising an FAU zeolite, which is
preferably mesoporous, of the type chosen from NaX, LiX, LiLSX, CaX, CaLSX, LiCaX and
LiCaLSX, preferably chosen from NaX, NaLSX and LiCaLSX, and mixtures of two or more
2s of them, are preferred.
[0059] For these types of applications, preference is given to a zeolite adsorbent material
of which the volume mean diameter (or the longest length) is between 0.3 mm and 7 mm,
preferably between 0.8 mm and 5.0 mm, and more preferably between I .0 mm and 3.0 mm,
limits included.
30 [0060] According to yet another embodiment, the invention also relates to the use of at
least one zeolite adsorbent material as has just been defined, for the purification of air of air
separation units (ASUs), in particular for removing hydrocarbons, carbon dioxide and
nitrogen oxides, upstream of cryogenic distillation units. These types of applications,
preferably carried out in PSA, TSA or PTSA processes, and preferably TSA or PTSA
35 processes, zeolite adsorbent materials comprising an FAU zeolite, which is preferably
mesoporous, of the type chosen from NaX, NaLSX, CaX and CaLSX, and mixtures of two
or more of them, are preferred.
[0061] For these types of applications, preference is given to a zeolite adsorbent material
of which the volume mean diameter (or the longest length) is between 0.3 mm and 7.0 mm,
5 and more preferably between 0.5 mm and 5.0 mm, limits included.
[0062] According to another aspect, the invention relates to a zeolite adsorbent material
having:
e an SilAI ratio of said adsorbent, such that 1 5 SilAl < 2.5, preferably 1 r SiIAI 5 2, more
preferably 1 r SilAI r 1.8, and more preferably between 1 5 SiIAI 5 1.6,
lo e a mesopore volume of between 0.08 cm3.g-I and 0.25 cm3.g-I, preferably between 0.08
cm3.g-' and 0.22 cm3.g-', and more preferably between 0.09 cm3.g-I and 0.20 cm3.g-I,
more preferably between 0.10 cm3.g-I and 0.20 cm3.g-', limits included,
of ratio (Vmicro - Vmeso)Nmicro between -0.5 and 1 .O, limits not included, preferably -
0.1 and 0.9, limits not included, preferably 0 and 0.9, limits not included, more preferably
15 between 0.2 and 0.8, limits not included, more preferably between 0.4 and 0.8, limits not
included, preferably between 0.6 and 0.8, limits not included, wherein the Vmicro is
measured by the Dubinin-Raduskevitch method and the Vmeso is measured by the BJH
method, and
a non-zeolite phase (PNZ) content such that 0 < PNZ r 30%, preferably 3% r PNZ r
20 25%, more preferably 3% r PNZ 5 20%, advantageously 5% 5 PNZ 5 20%, even better
still 7% r PNZ r 18%, measured by XRD, by weight relative to the total weight of the
zeolite adsorbent material,
all of the measurements being carried out on the zeolite adsorbent material at least 95%
exchanged with sodium.
25 /0063] The zeolite adsorbent material of the invention as has just been defined is a novel
material in that it results from the agglomeration, with a binder as described below, of at
least one mesoporous FAU zeolite, where the term "mesoporous", already previously
defined, denotes a zeolite which has, together with the microporosity inherent in the
structure of the zeolite, internal cavities of nanometric size (mesoporosity), easily
30 identifiable by obsewation using a transmission electron microscope (TEM), as described
for example in US 7 785 563.
I00641 More specifically, the zeolite adsorbent material comprises at least one
mesoporous FAU zeolite, that is to say a zeolite having an external surface area, defined
by the t-plot method described below, of between 40 m2.g-I and 400 m2.g-I, preferably
35 between 60 m2.g-I and 200 m2.g-I, limits included.
[0065] In addition, the zeolite adsorbent material according to the invention comprises at
least one metal chosen from lithium, sodium and calcium, and mixtures of two or more of
these metals, preferably two metals chosen from lithium, sodium and calcium, preferably
sodium and lithium or sodium and calcium or sodium, lithium and calcium. The zeolite
5 adsorbent materials in which the barium oxide content is less than 0.5%. preferably less
than 0.3%, more preferably less than 0.1%, by weight relative to the total weight of the
material, are also preferred.
lo0661 These characteristics make the zeolite adsorbent material according to the
invention particularly suitable for gas treatments, as was described above in the present
lo description.
[0067] The zeolite adsorbent material according to the invention can be in all the forms
known to those skilled in the art, and preferably in simple geometric forms, that is to say in
granular forms, for example of ball or rod type, that is to say in spherical or cylindrical forms,
respectively. Such simple forms are most particularly suitable since they are easy to
is process, in particular because of their shapes and their sizes that are compatible with
existing technologies. In addition, these simple forms mean that the processes used
consume low amounts of energy, since the zeolite adsorbent material generates few
pressure drops, and has improved transfer properties.
[0068] The zeolite adsorbent material according to the invention can be prepared
20 according to any method known to those skilled in the art, and in particular, and preferably,
using the process for preparing mesoporous FAU as described for example by W.
Schwieger (Angew. Chem. Int. Ed., (2012), 57, 1962-1965) and by agglomerating the
crystals obtained with at least one organic or mineral binder, preferably mineral binder, more
preferably a binder chosen from zeolitizable or non-zeolitizable clays, and in particular from
25 kaolins, kaolinites, nacrites, dickites, halloysites, attapulgites, sepiolites, montmorillonites,
bentonites, illites and metakaolins, and also mixtures of two or more of these clays, in any
proportions.
[0069] The agglomeration and the forming can be carried out according to all of the
techniques known to those skilled in the art, such as extrusion, compacting, agglomeration
30 on a granulating plate or granulating drum, atomization and the like. These various
techniques have the advantage of allowing the preparation of adsorbent materials according
to the invention which have the sizes and shapes previously described and are most
particularly suitable for gas treatments.
[0070] The proportions of agglomeration binder (for example clays, as indicated above)
35 and of zeolite(s) used for the preparation are typically those of the prior art, and vary
according to the desired PNZ content and the degree of zeolitization of the binder. These
proportions can be easily calculated by those skilled in the art specializing in the synthesis
of zeolite agglomerates.
[0071] The agglomerates of the zeolite adsorbent materials, whether they are in the form
of balls, extruded pieces or the like, generally have a volume mean diameter, or a mean
s length (largest dimension when they are not spherical), of less than or equal to 7 mm,
preferably between 0.05 mm and 7 mm, more preferably between 0.2 mm and 5 mm and
more preferentially between 0.2 mm and 2.5 mm.
[0072] The process for preparing the zeolite adsorbent materials according to the
invention is readily adaptable from the preparation processes known to those skilled in the
10 art, as already indicated, the use of at least one mesoporous FAU zeolite not substantially
modifying these known processes, which means that the preparation process is a process
that is easy, rapid and economical to implement and thus easily industrializable with a
minimum of steps.
[0073] The zeolite adsorbent material of the invention preferably comprises at the same
15 time macropores, mesopores and micropores. The term "macropores" is intended to mean
pores of which the opening is greater than 50 nm, preferably between 50 nm and 400 nm.
The term "mesopores" is intended to mean pores of which the opening is between 2 nm
and 50 nm, limits not induded. The term "tniuopores" is intended to mean pores of which
the opening is less than 2 nm.
20 [0074] According to one preferred embodiment, the zeolite adsorbent material according
to the present invention has a micropore volume ( Dubinin-Raduskevitch volume),
expressed in cm3 per gram of zeolite adsorbent material, of between 0.210 cm3.g-I and
0.360 cm3.g-', preferably between 0.230 cm3.g-? and 0.350 cm3.g-', more preferably
between 0.240 cm3.g-' and 0.350 cm3.g-', advantageously between 0.250 cm3.g-' and 0.350
25 cm3.g-', said micropore volume being measured on the zeolite adsorbent material at least
95% exchanged with sodium
100751 The total volume of the macropores and mesopores of the zeolite adsorbent
materials according to the invention, measured by mercury intrusion, is advantageously
between 0.15 cm3.g-' and 0.5 cm3.g-', preferably between 0.20 cm3.g-I and 0.40 cm3.g-' and
30 very preferably between 0.20 cm3.g-' and 0.35 cm3.g-',the measurements being carried out
on the adsorbent material at least 95% exchanged with sodium.
[0076] The volume fraction of the macropores of the zeolite adsorbent material is
preferably between 0.2 and 1.0 of the total volume of the macropores and mesopores, very
preferably between 0.4 and 0.8 and even more preferably between 0.45 and 0.65, limits
35 included, the measurements being carried out on the zeolite adsorbent material at least
95% exchanged with sodium.
[0077] The size of the FAU zeolite clystals used to prepare the zeolite adsorbent material
of the invention and also the size of the FAU zeolite elements in the zeolite adsorbent
material are measured by observation under a scanning electron microscope (SEM).
Preferably, the mean diameter of the FAU zeolite crystals is between 0.1 pm and 20 pm,
5 preferably between 0.5 pm and 20 pm, and more preferably between 0.5 pm and 10 pm.
The SEM observation also makes it possible to confirm the presence of non-zeolite phase
comprising for example residual binder (not converted during the optional zeolitization step)
or any other amorphous phase in the agglomerates.
[0078] According to one preferred embodiment, the zeolite adsorbent material according
10 to the invention has an external surface area, measured by nitrogen adsorption and
expressed in m2 per gram of adsorbent, greater than 20 m2.g-', and preferably between 20
m2.g-I and 300 m2.g-', and more preferably between 30 m2.g-' and 250 m2.g-' and more
preferably between 40 m2.g1 and 200 m2.g-I, and most preferably between 50 m2.g-' and
200 m2.g1, the measurements being carried out on the zeolite adsorbent material at least
1s 95% exchanged with sodium.
[0079] According to one preferred embodiment, the zeolite adsorbent material according
to the invention has a high volumetric adsorption capacity, that is to say a volumetric
micropore volume expressed in cm3.cm3 of zeolite adsofbent material at least 95%
exchanged with sodium, said volumetric micropore volume being greater than 0.10 cm3.cm-
20 3, preferably greater than 0.12 ~m~.cmm-o~r,e preferably greater than 0.15 ~m~.cm-~,more
preferably greater than 0.16 ~ m ~ . c mm-o~re, preferably greater than 0.18 ~m~.cme-n~tir,e ly
preferably greater than 0.20 ~ m ~ . c m - ~ .
[0080] According to one preferred embodiment, the zeolite adsorbent material according
to the invention comprises at least one mesoporous FAU zeolite as defined above, said at
2s least one zeolite having an SiIAI ratio such that 1 r SiIAI < 1.5, preferably 1 5 SilAl 5 1.4.
According to a most particularly preferred aspect, the SilAI ratio of said at least one
mesoporous FAU zeolite is equal to 1.00 +I- 0.05, the measurements being carried out on
the zeolite adsorbent material at least 95% exchanged with sodium.
[0081] According to yet another preferred embodiment, said zeolite adsorbent material
30 comprises at least one cation chosen from the ions of groups IA, IIA, IIIA, IB, IIB and lllB of
the periodic table, the trivalent ions of the lanthanide or rare earth series; the zinc(lI) ion,
the silver(1) ion, the cupric (11) ion, the chromium(lll) ion, the ferric (Ill) ion, the ammonium
ion andlor the hydronium ion, the preferred ions being calcium, lithium, sodium, potassium,
barium, cesium, strontium, zinc and rare-earth ions and more preferably sodium, calcium
35 2nd lithium ions. as indicated above.
[0082] The metal contents of the zeolite adsorbent material according to the invention,
expressed as oxides, preferably those previously indicated, and more particularly:
6 the CaO content is between 0% and 20.5% by weight relative to the total weight of the
zeolite adsorbent material, preferably between 3% and 20.5% by weight relative to the
5 total weight of the zeolite adsorbent material, preferably between 7.5% and 20.5% by
weight relative to the total weight of the zeolite adsorbent material, and preferably
between 9% and 20.5% by weight relative to the total weight of the zeolite adsorbent
material, limits included,
the Liz0 content is between 0% and 12% by weight relative to the total weight of the
10 zeolite adsorbent material, preferably between 3% and 12% by weight relative to the total
weight of the zeolite adsorbent material, preferably between 5% and 12% by weight
relative to the total weight of the zeolite adsorbent material, and preferably between 6.5%
and 12% by weight relative to the total weight of the adsorbent, limits included,
the Na20 content is between 0% and 22% by weight relative to the total weight of the
I S zeolite adsorbent material, preferably between 0% and 19% by weight relative to the total
weight of the zeolite adsorbent material, preferably between 0% and 15% by weight
relative to the total weight of the zeolite adsorbent material, preferably between 0% and
10% by weight relative to the total weight of the zeolite adsotlsent material, and entirely
preferably between 0% and 7% by weight relative to the total weight of the zeolite
20 adsorbent material, advantageously between 0% and 2% by weight relative to the total
weight of the zeolite adsorbent material, limits included, . it being understood that the zeolite adsorbent material comprises at least one of the three
metals chosen from lithium, sodium and calcium,
said zeolite adsorbent material possibly also comprising at least one rare earth, chosen
25 from lanthanides and actinides, preferably from lanthanides, in a content of generally
between 0% and lo%, preferably between 0% and 7%,
e said zeolite adsorbent material possibly also comprising, in small amounts (% expressed
as oxide, less than 5%, preferably less than 2%), one or more cations other than lithium,
sodium and calcium, for example and preferably chosen from potassium, barium,
30 strontium, cesium, transition metals such as silver, and the like.
[0083] As indicated above, the zeolite adsorbent materials in which the barium oxide
content is less than 0.5%, preferably less than 0.3%, more preferably less than 0.1%, by
weight relative to the total weight of the material, are also preferred.
[0084] According to a further preferred aspect, the zeolite adsorbent material according
35 to the invention does not have a zeolite structure other than the FAU (faujasite) structure.
Tie expression "does not have a zeolite structure other than the FAU struciure" is intended
to mean that an XRD (X-ray diffraction) analysis of the adsorbent material according to the
invention does not make it possible to detect more than 5% by weight, preferably not more
than 2% by weight, limits included, of zeolite structure other than a faujasite structure,
relative to the total weight of the adsorbent material.
5 [00851 According to yet another preferred embodiment, the invention relates to a zeolite
adsorbent material as defined above and having a total macropore and mesopore volume,
measured by merculy intrusion, of between 0.15 cm3.g-' and 0.5 cm3.g-', and a macropore
volume fraction of between 0.2 and 1 time said total macropore and mesopore volume,
preferably between 0.4 and 0.8, limits included, the measurements being carried out on the
l o adsorbent material at least 95% exchanged with sodium.
Characterization techniques
[0086] The physical properties of the zeolite adsorbent materials are evaluated by the
methods known to those skilled in the art, the main ones of which are recalled below.
15 Zeolite crystal particle size:
[0087] The estimation of the number-average diameter of the FAU zeolite crystals
contained in the zeolite adsorbent materials, and which are used for preparing said zeolite
adsorbent material, is camied out by observation under a scanning electron microscope
(SEM).
20 [0088] In order to estimate the size of the zeolite crystals on the samples, a set of images
is taken at a magnification of at least 5000. The diameter of at least 200 crystals is then
measured using dedicated software, for example the Smile View software published by
LoGraMi. The accuracy is of the order of 3%.
Zeolite adsorbent particle size
25 [0089] The volume mean diameter (or "volume-average diameter") of the zeolite
adsorbent material of the process according to the invention is determined by analysis of
the particle size distribution of a sample of adsorbent material by imaging according to
standard IS0 13322-2:2006, using a conveyor belt that allows the sample to pass in front
of the objective of the camera.
30 [0090] The volume-average diameter is then calculated from the particle size distribution
by applying standard IS0 9276-2:2001. In the present document, the name "volumeaverage
diameter" or else "size" is used for the zeolite adsorbent materials. The accuracy
is of the order of 0.01 mm for the size range of the adsorbent materials which may be used
in the context of the present invention.
35 Chemical analysis of the zeolite adsorbent materials - SilAl ratio and degree of
exchange:
[0091] An elemental chemical analysis of a zeolite adsorbent material described above
can be carried out according to various analytical techniques known to those skilled in the
art. Among these techniques, mention may be made of the technique of chemical analysis
by x-ray fluorescence as described in standard NF EN IS0 12677: 201 1 on a wavelength-
5 dispersive spectrometer (WDXRF), for example the Tiger S8 machine from the company
Bruker.
[0092] X-ray fluorescence is a non-destructive spectral technique which exploits the
photoluminescence of atoms in the x-ray range, to establish the elemental composition of
a sample. Excitation of the atoms, generally with an x-ray beam or by electron
10 bombardment, generates specific radiations after returning to the ground state of the atom.
A measurement uncertainty of less than 0.4% by weight is conventionally obtained after
calibration for each oxide.
[00931 Other methods of analysis are for example illustrated by the atomic absorption
spectrometry (AAS) and inductively coupled plasma atomic emission spectrometry (ICP-
15 AES) methods described in standards NF EN IS0 21587-3 or NF EN IS0 21079-3 on an
apparatus of for example Perkin Elmer 4300DV type.
[0094] The x-ray fluorescence spectrum has the advantage of depending very little on the
chemical cornbination of the element, which offers a precise determination, both
quantitatively and qualitatively. After calibration for each oxide SiOz and A1203. and also the
20 various oxides (such as those originating from the exchangeable cations, for example
sodium), a measurement uncertainty of less than 0.4% by weight is conventionally obtained.
The ICP-AES method is particularly suitable for measuring the lithium content which makes
it possible to calculate the lithium oxide content.
[0095] Thus, the elemental chemical analyses described above make it possible to verify
2s both the SilAl ratio of the zeolite used within the zeolite adsorbent material and the SiIAI
ratio of the zeolite adsorbent material. In the description of the present invention, the
measurement uncertainty for the SiIAI ratio is ?5%. The measurement of the SiIAl ratio of
the zeolite present in the adsorbent material can also be carried out by solid silicon nuclear
magnetic resonance (NMR) spectroscopy.
30 [0096] The quality of the ion exchange is linked to the number of moles of the cation in
quesiion in the zeolite adsorbent material after exchange. More specifically, the degree of
exchange with a given cation is estimated by evaluating the ratio between the number of
moles of said cation and the number of moles of all of the exchangeable cations. The
respective amounts of each of the cations are evaluated by chemical analysis of the
35 corresponding cations. For example, the degree of exchange with the sodium ions is
esiimated by evaluating the ratio between the total number of Na+ cations and the total
number of exchangeable cations (for example Ca2+, K+, Li', Ba2+, Csi, Nat, etc..), the
amount of each of the cations being evaluated by chemical analysis of the corresponding
oxides (Na20, CaO, K20, BaO, LizO, Cs20, etc.). This method of calculation also takes into
account the possible oxides present in the residual binder of the zeolite adsorbent material.
5 However, the amount of such oxides is considered to be minor compared with the oxides
originating from the cations of the exchangeable sites of the zeolite(s) of the zeolite
adsorbent material according to the invention.
Macropore and mesopore volume
[0097] The macropore and mesopore volume are measured, on a sample at least 95%
lo exchanged with sodium, by mercury intrusion porosimetry. A Micromeritics Autopore@9 500
mercury porosimeter is used to analyse the distribution of the pore volume contained in the
macropores and in the mesopores.
[0098] The experimental method, described in the operating manual for the apparatus
which refers to standard ASTM D4284-83, consists in placing a pre-weighed sample of
15 zeolite adsorbent material to be measured (of known loss on ignition) in a porosimeier cell,
then, after prior degassing (discharge pressure of 30 pmHg for at least 10 min), in filling the
cell with mercury at a given pressure (0.0036 MPa), and then in applying an increasing
pressure in steps up to 400 MPa in order to gradually cause the mercury to penetrate into
the porous network of the sample.
20 [0099] In the present document, the macropore and mesopore volumes of the zeolite
adsorbent materials, expressed in cm3.g-', are thus measured by mercury intrusion and
related to the weight of the sample in anhydrous equivalent, that is to say the weight of said
material corrected for the loss on ignition.
Mechanical strength of the zeolite adsorbent materials:
25 [00100] The bulk crush strength in a bed of the zeolite adsorbent materials as described in
the present invention is characterized according to standard ASTM 7084-04. The grain
crush strengths are determined with a " grain crushing strength" apparatus sold by Vinci
Technologies, according to standards ASTM D 4179 and D 6175.
Micropore volume measurement:
30 [OOIOI] The micropore volume measurement is estimated by conventional methods such
as Dubinin-Raduskevitch volume measurements (adsorption of liquid nitrogen at 77 K or of
liquid argon at 87 K).
[00102] The Dubinin-Raduskevitch volume is determined from the gas, such as nitrogen or
argon, adsorption isotherm measurement, at its liquefaction temperature, as a function of
35 the pore openings of the zeolite: nitrogen will be chosen for FAU. Prior to the adsorption,
the zeolite adsorbent material is degassed at between 300°C and 450°C for a time of
between 9 hours and 16 hours, under vacuum (P < 6.7~10P.~a) . Measurement of the
adsorption isotherms is then performed on a machine of ASAP 2020 type from
Micromeritics, taking at least 35 measurement points at relative pressures of ratio PIP0
between 0.002 and 1. The micropore volume is determined according to Dubinin and
s Raduskevitch from the isotherm obtained, by applying standard IS0 15901-3 (2007). The
micropore volume evaluated according to the Dubinin and Raduskevitch equation is
expressed in cm3 of liquid adsorbate per gram of zeolite adsorbent material. The
measurement uncertainty is + 0.003 cm3.g-', the measurements being carried out on the
zeolite adsorbent material at least 95% exchanged with sodium.
10 Volumetric micropore volume measurement:
[00103] The volumetric micropore volume is calculated from the micropore volume as
defined above and by multiplying said micropore volume by the apparent density of said
zeolite adsorbent material. The apparent density is measured as described in standard DIN
894817.6.
1s Loss on ignition of the zeolite adsorbent materials:
[00104] The loss on ignition is determined under an oxidizing atmosphere, by calcination
ofthe sample in air at a temperature of 950°C + 2YC, as described in standard NF EN 196-
2 (April 2006). The measurement standard deviation is less than 0.1%.
Qualitative and quantitative analysis by x-ray diffraction
20 [00105] The purity of the zeolites in the zeolite adsorbent materials is evaluated by x-ray
diffraction analysis, known to those skilled in the art by the acronym XRD. This identiiication
is carried out on a Bruker XRD apparatus.
[00106] This analysis makes it possible to identify the various zeolites present in the
adsorbent material since each of the zeolites has a unique diffractogram defined by the
2s positioning of the diffraction peaks and by their relative intensities.
[00107] The zeolite adsorbent materials are ground and then spread and levelled out on a
sample holder by simple mechanical compression.
[00108] The conditions under which the diffractogram is acquired on the Bruker 05000
machine are as follows:
30 Cu tube used at 40 kV - 30 mA;
slit size (divergent, scattering and analysis) = 0.6 mm;
filter: Ni;
sample device rotating at: 15 rpm;
* measuring range: 3" < 28 < 50";
3s increment: 0.02";
counting time per increment: 2 seconds.
[00109] Interpretation of the diffractogram obtained is performed with the EVA software
with identification of the zeolites using the ICDD PDF-2 release 201 1 base.
[OOIIO] The amount of the FAU zeolite fractions, by weight, is measured by XRD analysis;
this method is also used to measure the amount of the zeolite fractions other than FAU.
5 This analysis is performed on a Bruker brand machine, and the amount by weight of the
zeolite fractions is then evaluated using the TOPAS software from the company Bruker.
Measurement of the external surface area (m2/g) via the "t-plot" method:
[OOIII] The "t-plot" calculation method exploits the adsorption isotherm data Q ads = f
(PIPO) and makes it possible to calculate the micropore surface area. The external surface
10 area may be deduced therefrom by determining the difference with the BET surface area
which calculates the total pore surface area in m2/g (S BET = micropore surface area +
external surface area).
[00112] To calculate the micropore surface area via the t-plot method, the curve Q ads
(cm3.g-') is plotted as a function of t = thickness of the layer depending on the partial
15 pressure PIP0 that would be formed on a reference non-porous material (t function of log
(PIPO): Harkins-Jura equation applied: [13.99/(0.034-10g(PIP0))~0.5J. In the interval t
between 0.35 nm and 0.5 nm, a straight line may be plotted which defines an adsorbed
intercept point Q, which makes it possible to calculate the mimpore surface area. If the
material is not microporous, the straight line passes through 0, the measurements being
20 carried out on the zeolite adsorbent material at least 95% exchanged with sodium.
Mesopore volume measurement:
[00113] The measurement of the mesopore volume, on a sample at least 95% exchanged
with sodium, is estimated by conventional methods such as the Barret-Joyner-Halenda
volume measurements (adsorption of liquid nitrogen at 77 K).
25 [00114] The mesopore volume is determined from the gas, such as nitrogen, adsorption
isotherm measurement, at its liquefaction temperature, as a function of the pore openings
of the zeolite: nitrogen will be chosen for FAU. Prior to the adsorption, the zeolite adsorbent
material is degassed at between 300°C and 450°C for a time of between 9 hours and 16
hours, under vacuum (P < 6 . 7 ~ 1P0a~). Measurement of the adsorption isotherms is then
30 performed on a machine of ASAP 2020 type from Micromeritics, taking at least 35
measurement points at relative pressures of ratio PIP0 between 0.002 and 1. The mesopore
volume is determined according to Barret-Joyner-Halenda from the isotherm obtained, by
applying standard IS0 15901-2 (2007). The mesopore volume evaluated according to the
Barret-Joyner-Halenda equation is expressed in cm3 of liquid adsorbate per gram of zeolite
35 adsorbent material.
[00115] The following examples serve to illustrate the present invention without aiming to
limit the scope thereof as defined by the appended claims.
Example 1: Preparation of a zeolite adsorbent material according to the invention
5 Ster,: Synthesis of mesoporous LSX zeolite crystals having an SilAl ratio equal to
1.01 and an external surface area equal to 95 m2.g-'
a) Preparation of the growth gel: reactor stirred with an Archimedean screw at 250 rpm
[00116] A growth gel is prepared in a 3 liter stainless-steel reactor equipped with a heating
jacket, a temperature probe and a stirrer, by mixing an aluminate solution containing 300 g
10 of sodium hydroxide (NaOH), 264 g of 85% potassium hydroxide, 169 g of alumina
trihydrate (AI2O3.3H20c, ontaining 65.2% by weight of A1203) and 1200 g of water at 25°C
over 5 minutes, with a stirring speed of 250 rpm, with a silicate solution containing 490 g of
sodium silicate, 29.4 g of NaOH and 470 g of water at 25°C.
[00117] The stoichiometly of the growth gel is as follows: 4.32 Na20 1 1.85 K2O I A1203 1
15 2.0 Si02 1 114 H20. Homogenization of the growth gel is performed with stirring at 250 rpm
for 15 minutes at 25°C.
b) Addition of the nucleating gel
1001 181 11.6 g of nucleating gel (i.e. 0.4% by weigh*) of composition 12 Wa20/ AL03 1 10
Si02 1180 Hz0 prepared in the same manner as the growth gel, and which has matured for
20 1 hour at 40°C, is added to the growth gel, at 25°C with stirring at 300 rpm. Afler 5 minutes
of homogenization at 250 rpm, the stirring speed is reduced to 50 rprn and stirring is
continued for 30 minutes.
c) Introduction of the structuring agent into the reaction medium
[00119] 35.7 g of a solution of [3-(trimethoxysilyl)propyl]octadecyldirnethylammonium
25 chloride (TPOAC) at 60% in methanol (MeOH) are introduced into the reaction medium with
a stirring speed of 250 rpm for 5 minutes (TPOAC/AI2O3 mole ratio = 0.04). A maturation
step is then performed at 30°C for 20 hour at 50 rpm before starting the crystallization.
d) 2-Step crystallization
[00120] The stirring speed is maintained at 50 rpm and then an increase in the set point of
30 the reactor jacket is programmed at 63°C in a linear manner so that the reaction medium
increases in temperature to 60°C over the course of 5 hours, followed by a stationary
temperature phase for 21 hours at 60°C; the set point of the reactor jacket is then set at
102°C so that the reaction medium increases in temperature to 95°C over the course of 60
minutes. After 3 hours at a stationary temperature phase of 95"C, the reaction medium is
35 cooled by circulating cold water through the jacket to stop the crystallization.
e) Filfration/washing
[00121] The solids are recovered on a sinter and then washed with deionized water to
neutral pH.
fl Drying/calcination
[00122] In order to characterize the product, drying is performed in an oven at 90°C for 8
5 hours.
[00123] The calcination of the dried product, required in order to free both the microporosity
(water) and the mesoporosity by removing the structuring agent, is carried out by degassing
under vacuum with a gradual increase in steps of 50°C up to 400°C for a period of between
9 hours and 16 hours, under vacuum (P < 6.7~10.P~a ).
l o [00124] The micropore volume and the external surface area, measured according to the
t-plot method from the nitrogen adsorption isotherm at 77 K after degassing under vacuum
at 400°C for 10 hours, are respectively 0.215 cm3.g-I and 95 m2.g-'. The number-average
diameter of the crystals is 6 pm. The mesopore diameters calculated from the nitrogen
adsorption isotherm by the DFT method are between 5 nm and 10 nm. The XR diffractogram
15 corresponds to a pure faujasite (FAU) structure, no LTA zeolite is detected. The Si/AI mole
ratio of the mesoporous LSX determined by X-ray fluorescence is equal to 1.01.
[00125] Figure 1 shows an image obtained by transmission electron microscopy (TEM) of
the zeolite thus synthesized.
20 Step: Preparation of mesoporous LSX zeolite agglomerates
[00126] In the subsequent text, the weights given are expressed in anhydrous equivalent.
[00127] A homogeneous mixture consisting of 1700 g of mesoporous LSX zeolite crystals
obtained in step 1, of 300 g of ZeoclayB attapulgite, sold by CECA, and also of the amount
of water such that the loss on ignition of the paste before forming is 35%, is prepared. The
2s paste thus prepared is used on a granulating plate in order to prepare balls of agglomerated
zeolite adsorbent material. Selection by sieving of the balls obtained is carried out so as to
collect balls having a diameter of between 0.3 and 0.8 rnrn and a volume-average diameter
equal to 0.55 mm.
[00128] The balls are dried overnight in a ventilated oven at 80°C. They are then calcined
30 for 2 h at 550°C under nitrogen flushing, then 2 hat 550°C under flushing with decarbonated
dry air.
Step 3: Lithium exchange and activation of the mesoporous LSX zeolite
agglomerates
35 [00129] Five successive exchanges are carried out by means of 1 M lithium chloride
solutions, in a proportion of 20 ml.g-' of solid. Each exchange is continued for 4 h at 100"C,
and intermediate washes are performed, making it possible to remove the excess salt at
each step. In the final step, four washes are carried out at ambient temperature, in a
proportion of 20 m1.g-'.
[00130] The balls are dried overnight in a ventilated oven at 80°C. They are then activated
5 for 2 h at 550°C under nitrogen flushing.
[00131] The lithium oxide Li20 content, determined by ICP-AES, is 8.9% by weight relative
to the total weight of the zeolite adsorbent material. The volume-average diameter of the
balls is 0.55 mm. The bulk crush strength in a bed of the lithium-exchanged mesoporous
LSX zeolite balls is 2.6 daN.
10
Step: Characterizations
[00132] In orderto characterize the zeolite adsorbent material, it is at least 95% exchanged
with sodium in the following way: the zeolite adsorbent material is introduced into a NaCl
solution containing 1 mol of NaCl per liter, at 90°C, for 3 h, with a liquid-to-solid ratio of 10
15 m1.g-'. The operation 1s repeated 4 times. Between each exchange, the sol~ds are
successively washed four times by immersing them in water in a proportion of 20 m1.g-' in
order to remove the excess salt, and then dried for 12 h at 80°C under air, before being
analyzed by x-ray fluorescence. The weight percentage of sod~um oxide of the zeolite
adsorbent material is equal to 18.2% with a stability at less than 1% between exchange
20 operations 3 and 4. The balls are dried overnight in a ventilated oven at 80°C. They are
then activated for 2 h at 550°C under nitrogen flushing.
[00133] The external surface area is equal to 99 m2.g-' of adsorbent, the micropore volume
is 0.264 cm3.g-' of sodium-exchanged adsorbent. The volumetric micropore volume is 0.1 50
cm3 per cm3 of sodium-exchanged zeolite adsorbent material. The mesopore volume is
25 equal to 0.165 cm3.g-' of sodium-exchanged adsorbent. The total macropore and mesopore
volume, measured by mercury intrusion, is 0.42 cm3.g-' of sodium-exchanged adsorbent.
[00134] The SiIAI atomic ratio of the adsorbent is 1.25. The SiIAI ratio of the zeolite present
in the adsorbent zeolite material, which is equal to 1.01, is determined by solid silicon 29
NMR.
30 [00135] The content of non-zeolite phase (PNZ), measured by XRD and expressed by
weight relative to the total weight of the adsorbent, is 15.3%
Example 2: Comparative zeolite adsorbent material
[00136] SiliporiteB NitroxyB SXSDM sieve from CECA is a material based on LiLSX zeolite
35 agglomerated with attapulgite. The volumetric mean diameter of the balls is equal to 0.55
mm. The content of lithium oxide Li20, measured by ICP-AES, is 9.2% by weight relative to
the total weight of sieve.
[00137] As in step 4 of example 1, sodium exchanges are carried out so as to obtain a solid
at least 95% exchanged with sodium. As previously, this result is obtained with 4
s consecutive exchanges.
[00138] The weight percentage of sodium oxide of the zeolite adsorbent material, obtained
by x-ray fluorescence, is equal to 18.4% with a stability at less than 1% between exchange
operations 3 and 4. The balls are dried overnight in a ventilated oven at 80°C. They are
then activated for 2 h at 550°C under nitrogen flushing.
10 [00139] The external surface area is equal to 31 m2.g-l of adsorbent, the micropore volume
is 0.265 cm3.g-I of sodium-exchanged adsorbent. The volumetric micropore volume is 0.1 72
cm3 per cm3 of sodium-exchanged zeolite adsorbent material. The mesopore volume is
equal to 0.07 cm3.g-' of sodium-exchanged adsorbent. The total macropore and mesopore
volume, measured by merculy intrusion, is 0.31 cm3.g-I of sodium-exchanged adsorbent.
1s [00140] The SiIAI atomic ratio of the adsorbent is 1.23. The content of non-zeolite phase
(PNZ), measured by XRD and expressed by weight relative to the total weight of the
adsorbent, is 15.3%.
Example 3:
20 N2 / O2 separation tests on a fixed bed of adsorbant with pressure swing adsorption
[00141] An N2 102 separation test is carried out by adsorption in a single column according
to a principle presented in E. Alpay et al. (ibid.).
[00142] Figure 2 describes the assembly produced. A column (1) of internal diameter equal
to 27.5 mm and of internal height equal to 600 mm, filled with zeolite adsorbent material
25 (2), is fed with dry air (3) intermittently by means of a valve (4). The time for feeding the
column ( I ) with the stream (3) is called adsorption time. When the column (1) is not fed with
dry air, the stream (3) is discharged into the atmosphere by the valve (5). The zeolite
adsorbent material preferentially absorbs nitrogen, so that an oxygen-enriched air leaves
the column via the non-return valve (6), to a buffering tank (7). A regulating valve (8)
30 continuously delivers the gas at outlet (9) at a constant flow rate fixed at 1 NL.min-l.
[00143lj When the column (1) is not fed, that is to say when the valve (4) is closed and the
valve (5) is open, the column (1) is depressurized by the valve (10) to the atmosphere (1 I ) ,
for a period called the desorption time. The adsorption and desorption phases follow on
from one another. The durations of these phases are fixed from one cycle to the other and
35 they are adjustable. Table 1 indicates the respective state of the valves as a function of the
adsorption and desorption phases.
I Valve (5) closed 1 Valve (5) open I
Table 1
Adsorption phase
example 1 (according to the invention) and of example 2 (comparative). The column is
loaded at constant volume, with respectively 204.5 g and 239.7 g of adsorbent materials.
5 The pressure at the inlet is fixed at 280 kPa relative.
Desorption phase
Valve (10) closed
[00145] The outlet flow rate is fixed at 1 NL.min-'. The adsorption time is fixed at 0.25 s.
The desorption time is variable between 0.25 s and 1.25 s.
[00146] The oxygen concentration at outlet (9) is measured by means of a Servomex 570A
Valve (4) open I Valve (4) closed
Valve (1 0) open
oxygen analyzer.
l o [00147] Figure 3 shows the oxygen content of the stream produced at outlet (9) as a
function of the desorption time fixed for the materials of example 1 and example 2. Despite
[00144] The tests are carried out successively with the zeolite adsorbent materials of
a lower weight loaded into the column, the material of example 1 (according to the invention)
proves to be much more efficient ( ~tne rms of oxygen content of the gas produced) than the
solid of example 2 (comparative).

CLAIMS
5 1. The use, for gas separation, of at least one zeolite adsorbent material comprising
at least one FAU zeolite, said adsorbent having: . an external surface area, measured by nitrogen adsorption and expressed in m2 per
gram of adsorbent greater than 20 m2.g-', and preferably between 20 m2.g-' and 300
m2.g-', and more preferably between 30 m2.g-' and 250 m2.g-' and even more preferably
10 between 40 m2.g-' and 200 m2.g-', and most particularly between 50 m2.g-' and 200 m2.g-
1 . a non-zeolite phase (PNZ) content such that 0 < PNZ r 30%, preferably 3% 5 PNZ r
25%, more preferably 3% r PNZ 5 20%, advantageously 5% r PNZ 5 20%, even better
still 7% r PNZ r 18%, measured by XRD (X-ray diffraction), by weight relative to the total
15 weight of the adsorbent,
e a mesopore volume of between 0.08 cm3.g-' and 0.25 cm3.g-', preferably between 0.08
cm3.g-' and 0.22 cm3.g-', and more preferably between 0.09 cm3.g-' and 0.20 cm3.g-',
mare preferably between 0.10 m3.g-' and 0.20 m3.g-', limits included,
e and an SilAl atomic ratio of the adsorbent of between 1 and 2.5, preferably between 1
20 and 2.0, more preferably between 1 and 1.8 and entirely preferably between 1 and 1.6,
all of the measurements being carried out on the adsorbent material at least 95%
exchanged with sodium.
2. The use as claimed in claim I, wherein said at least one zeolite adsorbent material
25 has a (Vmicro -Vmeso)lVmicro ratio of between -0.5 and 1 .O, limits not included, preferably
between -0.1 and 0.9, limits not included, preferably between 0 and 0.9, limits not included,
more preferably between 0.2 and 0.8, limits not included, more preferably between 0.4 and
0.8, limits not included, preferably between 0.6 and 0.8, limits not included, where Vmicro
is the micropore volume measured by the Dubinin-Raduskevitch method and Vmeso is the
30 mesopore volume measured by the Barrett-Joyner-Halenda (BJH) method, all of the
measurements being carried out on the zeolite adsorbent material at least 95% exchanged
with sodium.
3. The use as claimed in either of claims 1 and 2, in which said at least one zeolite
35 adsorbent material has a micropore volume (Dubinin-Raduskevitch volume), expressed in
cm3 per gram of zeolite adsorbent material, of between 0.210 cm3.g-' and 0.360 cm3.g-',
preferably between 0.230 cm3.g-' and 0.350 cm3.g-', preferably between 0.240 cm3.g-' and
0.350 cm3.g-', more preferably 0.250 cm3.g-' and 0.350 cm3.g-', measured on the zeolite
adsorbent material at least 95% exchanged with sodium
5 4. The use as claimed in any one of claims 1 to 3, wherein said at least one FAU
zeolite has an SiIAI ratio corresponding to the inequation 1 5 SiIAI < 1.5, preferably 1 r SiIAI
5 1.4, and more preferably an SiIAI atomic ratio equal to I .OO +I- 0.05, said SiIAI ratio being
measured by solid silicon 29 NMR.
l o 5. The use as claimed in any one of claims 1 to 4, wherein said zeolite adsorbent
material comprises at least one cation chosen from the ions of groups IA, IIA, IIIA, IB, llB
and Ill6 of the periodic table, the trivalent ions of the lanthanide or rare earth series, the
zinc(ll) ion, the silver(1) ion, the cupric (11) ion, the chromium(lll) ion, the ferric (Ill) ion, the
ammonium ion andlor the hydronium ion, the preferred ions being calcium, lithium, sodium,
15 potassium, barium, cesium, strontium, zincand rare-earth ions and more preferably sodium,
calcium and lithium ions.
6. The use of at least one zeolite to adsotbent material as dairned in any one of
claims 1 to 5, wherein said at least one material comprises at least one alkali or alkaline-
20 earth metal chosen from sodium, calcium, lithium, and mixtures of two or three of them in
any proportions, the contents of which, expressed as oxides, are such that:
the CaO content is between 0% and 20.5% by weight relative to the total weight of the
zeolite adsorbent material, preferably between 3% and 20.5% by weight relative to the
total weight of the zeolite adsorbent material, preferably between 7.5% and 20.5% by
2s weight relative to the total weight of the zeolite adsorbent material, and preferably
between 9% and 20.5% by weight relative to the total weight of the zeolite adsorbent
material, limits included,
the LizO content is between 0% and 12% by weight relative to the total weight of the
zeolite adsorbent material, preferably between 3% and 12% by weight relative to the total
30 weight of the zeolite adsorbent material, preferably between 5% and 12% by weight
relative to the total weight of the zeolite adsorbent material, and preferably between 6.5%
and 12% by weight relative to the total weight of the zeolite adsorbent material, limits
included,
the NazO content is between 0% and 22% by weight relative to the total weight of the
35 zeolite adsorbent material, preferably between 0% and 19% by weight relative to tine total
weight of the zeolite adsorbent material, preferably between 0% and 15% by weight
relative to the total weight of the zeolite adsorbent material, preferably between 0% and
10% by weight relative to the total weight of the zeolite adsorbent material, and entirely
preferably between 0% and 7% by weight relative to the total weight of the zeolite
adsorbent material, advantageously between 0% and 2% by weight relative to the total
5 weight of the zeolite adsorbent material, limits included,
it being understood that the zeolite adsorbent material comprises at least one of the three
metals chosen from lithium, sodium and calcium,
said zeolite adsorbent material possibly also comprising at least one rare earth, chosen
from lanthanides and actinides, preferably from lanthanides, in a content of generally
10 between 0% and lo%, preferably between 0% and 7%,
said zeolite adsorbent material possibly also comprising, in small amounts (% expressed
as oxide, less than 5%, preferably less than 2%), one or more cations other than lithium,
sodium and calcium, for example and preferably chosen from potassium, barium,
strontium, cesium, transition metals such as silver, and the like.
15
7. The use as claimed in any one of claims 1 to 6, for purifying natural gas, in
particular for removing the impurities and preferably for removing the carbon dioxide andlor
the mercapians, present in natural gas.
20 8. The use as claimed in claim 7, wherein the zeolite adsorbent material comprises
at least one FAU zeolite, which is preferably mesoporous, of the type chosen from NaX and
CaX, and mixtures thereof.
9. The use as claimed in any one of claims 1 to 6, for the noncryogenic separation of
2s industrial gases and of gases in the air.
10. The use as claimed in claim 9, for nitrogen adsorption in the separation of gas from
the air, in particular for the enrichment of oxygen in the air.
30 11. The use as claimed in claim 9 or claim 10, wherein the zeolite adsorbent material
comprises at least one FAU zeolite, which is preferably mesoporous, of the type chosen
from NaX, LiX, CaX, LiCaX, NaLSX, LiLSX, CaLSX and LiCaLSX, and mixtures of two or
more of them.
12. The use as claimed in any one of claims 9 to 11 in pressure swing adsorption
devices according to very short cycles, and in particular in oxygen concentrators for
respiratory assistance.
5 13. The use as claimed in claim 12, wherein the zeolite adsorbent material comprises
at least one FAU zeolite, which is preferably mesoporous, of the type chosen from CaLSX,
LiLSX and LiCaLSX, more preferably at least one LiLSX zeolite, preferably mesoporous
LiLSX zeolite.
lo 14. The use as claimed in any one of claims 1 to 6, for the purification of syngas, which
is possibly polluted with carbon dioxide and one or more possible other impurities.
15. The use as claimed in claim 14, wherein the zeolite adsorbent material comprises
at least one FAU zeolite, which is preferably mesoporous, of the type chosen from NaX,
is LiX, LiLSX, CaX, CaLSX, LiCaX and LiCaLSX, preferably chosen from NaX, NaLSX and
LiCaLSX, and mixtures of two or more of them.
16. The use as claimed in any one of claims 1 to 6, for the purification of air of air
separation units (ASUs), in particular for removing hydrocahons, carbon dioxide and
20 nitrogen oxides, upstream of cryogenic distillation units.
17. The use as claimed in claim 16, wherein the zeolite adsorbent material comprises
at least one FAU zeolite, which is preferably mesoporous, of the types chosen from NaX,
NaLSX, CaX and CaLSX, and mixtures of two or more of them.
25
18. A zeolite adsorbent material which has: . an SiIAI ratio of said adsorbent, such that 1 5 SiIAI < 2.5, preferably 1 5 SiIAI s 2, more
preferably 1 r SiIAI 5 1.8, and more preferably between 1 5 SiIAI 5 1.6, . a mesopore volume of between 0.08 cm3.g-' and 0.25 cm3.g~',p referably between 0.08
30 cm3.g-' and 0.22 cm3.g-I, and more preferably between 0.09 cm3.g-' and 0.20 cm3.g-',
more preferably between 0.10 cm3.g-' and 0.20 cm3.g-I, limits included,
of ratio (Vmicro - Vmeso)Nmicro between -0.5 and 1.0, limits not included, preferably -
0.1 and 0.9, limits not included, preferably 0 and 0.9, limits not included, more preferably
between 0.2 and 0.8, limits not included, more preferably between 0.4 and 0.8, limits not
35 included, preferably between 0.6 and 0.8, limits not included, wherein the Vmicro is
measured by the Dubinin-Raduskevitch method and the Vmeso is measured by the BJH
method, and
a non-zeolite phase (PNZ) content such that 0 < PNZ r 30%, preferably 3% r PNZ r
25%, more preferably 3% 5 PNZ 5 20%, advantageously 5% 5 PNZ 5 20%, even better
5 still 7% r PNZ 5 18%, measured by XRD, by weight relative to the total weight of the
zeolite adsorbent material,
all of the measurements being carried out on the zeolite adsorbent material at least 95%
exchanged with sodium.
l o 19. The zeolite adsorbent material as claimed in claim 18, which has a micropore
volume, expressed in cm3 per gram of zeolite adsorbent material, of between 0.210 cm3.g-
' and 0.360 cm3.g-', preferably between 0.230 cm3.g-' and 0.350 cm3.g-', more preferably
between 0.240 cm3.g-' and 0.350 cm3.g-I, advantageously between 0.250 cm3.g-I and 0.350
cm3.g-', said micropore volume being measured on the zeolite adsorbent material at least
15 95% exchanged with sodium
20. The zeolite adsorbent material as claimed in either one of claims 18 and 19, of
which the to$a.l volume ofthe macropores and mesopores, measured by mercury intrusion,
IS between 0.15 cm3.g-' and 0.5 cm3.g-', preferably between 0.20 cm3.g-' and 0.40 cm3.g-'
20 and very preferably between 0.20 cm3 g-' and 0.35 cm3 g ',measured on the zeolite
adsorbent mater~aal t least 95% exchanged with sodium.
21. The zeolite adsorbent material as claimed in any one of claims 18 to 20, which has
an external surface area, measured by nitrogen adsorption and expressed in m2 per gram
25 of adsorbent, greater than 20 m2.g-', and preferably between 20 m2.g-' and 300 m2.g-', and
more preferably between 30 m2.g-' and 250 m2.g-I and more preferably between 40 m2.g-'
and 200 m2.g-', and most preferably between 50 m2.g-' and 200 m2.g-', measured on the
zeolite adsorbent material at least 95% exchanged with sodium.
30 22. The zeolite adsorbent material as claimed in any one of claims 18 to 21, which has
a volumetric micropore volume, expressed in ~ m ~ . comf z-e~o lite adsorbent material at least
95% exchanged with sodium, of greater than 0.10 ~ m ~ . c mpr-e~fe,r ably greater than 0.12
~ m ~ . c mm-o~re, preferably greater than 0.15 ~m~.cm-~,rnporreefe rably greater than 0.16
~ m ~ . c mm-o~re, preferably greater than 0.18 ~ m ~ . c men-t~ire, ly preferably greater than 0.20
35 ~ m ~ . c m - ~ .
23. The zeolite adsorbent material as claimed in any one of claims 18 to 22, of which
the metal contents, expressed as oxides, are the following:
the CaO content is between 0% and 20.5% by weight relative to the total weight of the
zeolite adsorbent material, preferably between 3% and 20.5% by weight relative to the
5 total weight of the zeolite adsorbent material, preferably between 7.5% and 20.5% by
weight relative to the total weight of the zeolite adsorbent material, and preferably
between 9% and 20.5% by weight relative to the total weight of the zeolite adsorbent
material, limits included,
the Liz0 content is between 0% and 12% by weight relative to the total weight of the
ID zeolite adsorbent material, preferably between 3% and 12% by weight relative to the total
weight of the zeolite adsorbent material, preferably between 5% and 12% by weight
relative to the total weight of the zeolite adsorbent material, and preferably between 6.5%
and 12% by weight relative to the total weight of the adsorbent, limits included,
the NazO content is between 0% and 22% by weight relative to the total weight of the
15 zeolite adsorbent material, preferably between 0% and 19% by weight relafive to the total
weight of the zeolite adsorbent material, preferably between 0% and 15% by weight
relative to the total weight of the zeolite adsorbent material, preferably between 0% and
10% by weight relative to the total weight of the zeolite adsorbent material, and entirely
preferably between 0% and 7% by weight relative to the total weight of the zeolite
20 adsorbent material, advantageously between 0% and 2% by weight relative to the total
weight of the zeolite adsorbent material, limits included,
it being understood that the zeolite adsorbent material comprises at least one of the three
metals chosen from lithium, sodium and calcium,
said zeolite adsorbent material possibly also comprising at least one rare earth, chosen
25 from lanthanides and actinides, preferably from lanthanides, in a content of generally
between 0% and lo%, preferably between 0% and 7%,
said zeolite adsorbent material possibly also comprising, in small amounts (% expressed
as oxide, less than 5%, preferably less than 2%), one or more cations other than lithium,
sodium and calcium, for example and preferably chosen from potassium, barium,
30 strontium, cesium, transition metals such as silver, and the like
24. The material as claimed in any one of claims 18 to 23, which has a total macropore and
mesopore volume, measured by mercury intrusion, of between 0.15 cm3.g-' and 0.5 cm3.g-', and a
macropore volume fraction of between 0.2 and 1 time said total macropore and mesopore volume,
preferably between 0.4 and 0.8, limits included, the measurements being carried out on the
adsorbent material at least 95% exchanged with sodium.