Molecular sieve abstract
The invention relates to a process for modifying a molecular sieve,
whereby the molecular sieve is brought into contact with a modifying
agent containing at least one weak acid, a salt of a weak acid or
a derivative of a weak acid of at least one element of Groups III,
IV or V of the Periodic Table of Elements, by dry mixing the molecular
sieve and the modifying agent, optionally followed by adding liquid
to form a slurry or paste, whereafter the resulting mixture is subjected
to a thermal treatment.
Molecular sieve claims
We claim:
1. A process for modifying a molecular sieve, whereby the molecular
sieve is brought into contact with a modifying agent containing
at least one weak acid, a salt of a weak acid or a derivative of
a weak acid of at least one element of Groups III, IV or V of the
Periodic Table of Elements, by dry mixing the molecular sieve and
the modifying agent, whereafter the resulting mixture is subjected
to a first thermal treatment at a temperature in the range from
about 80-100.degree. C. followed by a second thermal treatment to
promote polymerization at a temperature in the range from about
400-600.degree. C.
2. Process according to claim 1 wherein the modifying agent contains
at least one of said modifying agent that has the ability to polymerize
at elevated temperature.
3. Process according to claim 1 wherein the molecular sieve is
brought into contact with substantially dry powder of the modifying
agent, followed by addition of liquid to form a slurry or paste.
4. Process according to claim 3 wherein said liquid is water.
5. Process according to claim 4 wherein the ratio of water to
molecular sieve ranges from 2 to 0.25 preferably from 1.25 to 0.8.
6. Process according to claim 1 wherein the modifying agent is
chosen from the group consisting of boric acid, silicic acid, acids
of phosphor and salts thereof.
7. Process according to claim 6 wherein the modifying agent is
selected from the group consisting of H.sub.3 BO.sub.3 NaH.sub.2
PO.sub.2 Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O, K.sub.3 PO.sub.4
(NH.sub.4).sub.2 HPO.sub.2 Na.sub.2 B.sub.4 O.sub.7.10H.sub.2 O
and Si(OH).sub.4.
8. Process according to claim 1 wherein the ratio of the amount
of molecular sieve to modifying agent ranges from 100:1 to 1:1.
9. Process according to claim 8 wherein said ratio ranges from
10:1 to 3:1.
10. Modified molecular sieve prepared in accordance with claim
1.
11. A process for modifying a molecular sieve, whereby the molecular
sieve is brought into contact with a modifying agent containing
at least one weak acid, a salt of a weak acid or a derivative of
a weak acid of at least one element of Groups III, IV or V of the
Periodic Table of Elements, by dry mixing the molecular sieve and
the modifying agent, followed by adding liquid to form a slurry
or paste, whereafter the resulting mixture is subjected to a first
thermal treatment at a temperature in the range from about 80-100.degree.
C. followed by a second thermal treatment to promote polymerization
at a temperature in the range from about 400-600.degree. C.
Molecular sieve description
The invention concerns a process for modifying a molecular sieve,
whereby the molecular sieve is brought into contact with a modifying
agent.
The modification of molecular sieves is well known in the art.
One type of modification, which is i.a. described in FR-A 2.143.340
is concerned with the increase of acid resistance of the molecular
sieve. Another type of modification concerns the catalytic activity,
which can be changed or modified by treatment of the molecular sieve
with certain modifying agents. An example thereof is given in EP-A
173507.
In U.S. Pat. No. 4414005 a process for modifying a molecular
sieve or zeolite is described, wherein the molecular sieve in the
H-form is treated with, for example, silane or diborane. The thus
treated molecular sieve is then reacted with water.
Modification of molecular sieves or zeolites is an important process
to obtain products with different properties. By modification both
the chemical structure and the pore geometry of the molecular sieve
are changed. This has an influence on the kind of molecules that
can enter the pores, so that the catalytic properties and the separation
characteristics of the molecular sieves are changed.
Both the molecular sieving and the adsorption selectivity may be
altered by cation exchange or decationization, and/or preadsorption
of polar molecules. The pore size and affinity of a molecular sieve
can also be altered by a chemical modification of the molecular
sieve structure using reactants as X.sub.x H.sub.y (SiH.sub.4 or
B.sub.2 H.sub.6). The free diameters of the zeolitic pores and therefore
the molecular sieving properties of a zeolite, and also the electric
field and hence the adsorption selectivity are permanently changed.
The chemical modification with silane on zeolites Y, mordenite LP
and dealuminated mordenite LP changes the intracrystalline free
volume and the effective pore size of the zeolites. Similar, a chemisorption
of diborane alters the sorption characteristics of zeolites. The
mechanism of both modification procedures can be divided in three
parts: the primary chemisorption of the reactant with the zeolite,
the secondary reactions inside the channels and the reaction with
water of the treated substrate. The effective pore size can be changed,
in a controlled way, by applying silanation and/or boranation processes
under well-defined reaction conditions, such as degree of chemisorption,
reaction temperature and pressure, extent of secondary reactions,
reaction time, etc.
The known process for modifying molecular sieves has the disadvantage
that it involves the use of gaseous reactants, i.e. silane or diborane,
which requires very careful and complex processing, in view of the
hazards involved in handling these products.
Although these disadvantages of the known process can be overcome
by specific measures, it would be highly preferable if a process
of the above kind could be developed that does not require the use
of the expensive and somewhat hazardous modifying agents.
In accordance with the present invention, there has been discovered
a new procedure of modifying molecular sieves to alter their molecular
sieving and adsorption selectivity properties.
This procedure includes dry mixing the molecular sieve with weak
acids, salts or derivatives thereof, in combination with a thermal
treatment. The molecular sieve can be modified in various ways,
including:
1. dry mixing the molecular sieve and modifying agent, followed
by thermal treatment, and
2. dry mixing the molecular sieve and modifying agent, followed
by adding a liquid such as water and/or organic solvent, to form
a slurry or paste, drying the mixture thus obtained, followed by
thermal treatment as in 1.
In principle these methods either give a dry mixture, a slurry
or a paste. Preference is given to the second method under conditions
(liquid/molecular sieve ratio) that a paste is formed.
Afterwards the dry, solid mixture of molecular sieve and modifying
agent undergoes a thermal treatment for several hours. A reaction
between the molecular sieve and the modifying agent causes a change
in the porosity and affinity of the molecular sieve.
The invention thus comprises a process for modifying a molecular
sieve, whereby the molecular sieve is brought into contact with
a modifying agent containing at least one weak acid, a salt of a
weak acid or a derivative of a weak acid of at least one element
of Groups III, IV or V of the Period Table of Elements, by dry mixing
the molecular sieve and the modifying agent, optionally followed
by adding liquid to form a slurry or paste, whereafter the resulting
mixture is subjected to a thermal treatment.
One of the advantages of this new process is the ease of manipulating
both starting materials compared with the complex and dangerous
silanation and/or boranation modification methods (explosion hazards).
Because the process is based on a mixture of two compounds (determined
by a simple gravimetric measurement) the usual upscaling problems
do not occur. Also the homogenity of the modified sample can be
controlled independently of the amount of treated zeolite. Typical
of this new procedure of modifying of molecular sieves is the ease
for the industrial use and the favoured economical application without
very high pretreatment and installation costs and the absence of
process hazards. More in particular the present invention has the
advantage of very good reproducibility.
It is remarked that for a suitably good result the dry mixing step
is essential. It is remarked, that the known methods for increasing
the acid resistance of the molecular sieve by impregnation with
an aqueous solution to prepare a coating on the molecular sieve
do not give the good results obtained with the process of the present
invention.
The chemical modifications with hydrides (diborane and silane)
require OH-groups and are generally carried out only on H-form molecular
sieves. With this new process of modification however, all types
of cation-form molecular sieves can also be used.
Because the molecular sieves have been contacted with a modifying
agent and thermally treated, the compounds formed in the channels
and cages influence the molecular sieving and the selective adsorption
characteristics of the substrates. The resulting sorption behaviour
depends on the nature of the introduced obstructions, their location
and interaction with the molecular sieve. Therefore a mechanism
has been proposed to elucidate the observed adsorption properties
in the case of boric acid. When a molecular sieve has been contacted
with boric acid (H.sub.3 BO.sub.3), the boric acid will polymerise
during the thermal treatment to boron-oxides. By changing, for example
the amount of added boric acid or the degree of polymerization,
it is possible to change the adsorption behaviour of the zeolite
in a controlled way. Hydroxyl groups inside the channels of a molecular
sieve, if any, may react with boron hydroxyl groups when they are
heated. By fusing boric acid one forms first gaseous metaboric acid
and later boron oxides according to: ##STR1##
The metaboric acid undergoes several other transitions resulting
in its .alpha.-, .beta.- or -65 -form. ##STR2##
The metaboric acid will enter the zeolite and the pores and can
dimerize ##STR3##
Also in the zeolite pores a reaction with hydration water is possible.
##STR4##
At elevated temperature, polymerization between neighbouring boron
hydroxyl groups is possible with the removal of H.sub.2 O. ##STR5##
This should lead to a network of linked boron-oxygen compounds
inside the pores of the molecular sieve. The types of formed, polymerized
compounds depend on the molecular sieve network and on the forms
characteristic for metaboric acid (namely .alpha.-, .beta.- or -65
-form).
Further dehydration results in the formation of boron-oxides, polymerized
inside the structure of the molecular sieve. Finally, cross-linked
metaborates and boron-oxides will be present in the molecular sieve
pores, strongly affecting the molecular sieving and selective adsorption
properties.
The other modifying reagents used, concerning this new procedure,
are believed to act in a similar way. The molecular sieves are modified
by the same manipulations based on a mixing of compounds and a thermal
treatment. The high temperatures induce also the formation of different
polymerized oxides compounds inside the channels of the molecular
sieves. These implanted compounds act as obstructions and change
the gas-substrate interactions compared with the original, unmodified
sample.
The contact between molecular sieve and the modifying agent, can
be carried out in a number of ways:
1) dry mixing molecular sieve and modifying agent and
2) dry mixing as in 1) followed by adding liquid such as water
and/or organic solvent, to form a slurry, or paste and afterwards
drying.
In all embodiments the molecular sieve that has been brought into
contact with the modifying agent (the mixture) is subsequently subjected
to a thermal treatment at a temperature of at least 250.degree.
C.
In the case said mixture still contains free and/or bound solvent
it is subjected to a drying and/or activating step in order to remove
free and/or bound solvent, previous to the thermal treatment. This
drying and/or activating step can be carried out at reduced pressure,
for example to prevent decomposition of organic solvent or to facilitate
the removal of solvent. It is not necessary that the steps of drying
and/or activating on the one hand and thermal treatment on the other,
are clearly distinguishable from each other, for example by intermediate
cooling.
An important aspect is that if there is free liquid present in
the mixture, the temperature is raised above the boiling point of
the used solvent at the pressure applied, with an upper limit of
200.degree. C. In the case of water it is preferred to dry the mixture
at a temperature between 50 and 110.degree. C., until all water
has been evaporated.
Thereafter the temperature is increased to a value above 250.degree.
C. for a period of time sufficient to obtain the required polymerization
of the modifying agent. The time for this ranges from 05 to 24
hours or more, whereas the temperature can be between 250.degree.
C. and 750.degree. C. Shorter times or lower temperatures tend to
give insufficient results, whereas longer times do not give additional
advantages. The same applies to higher temperatures, whereby one
should be careful to avoid that too much modifying agent becomes
gaseous, or that the molecular sieve structure collapses.
The molecular sieves to be treated in accordance with the invention
can be any natural or synthetic molecular sieve or zeolite. Zeolites
and molecular sieves are known in the art and can suitably be defined
as product with a crystallized microporous structure, such as crystalline
alumino silicates with an Si/Al molar ratio of 1 to 100 preferably
1-20. Examples are mordenite SP and LP, zeolite A, X and Y, ZSM-5
clinoptilolite, ferrieriete, silicalite, erionite, chabazite, etc.
in H- or cation form. It is also possible to use a molecular sieve
that contains metal species.
The modifying agent must be capable of forming polymerized structures
in the molecular sieve and is of inorganic nature. These requirements
are fullfilled by weak acids of the elements of Group III, IV and
V of the Periodic Table, as well as the salts and derivatives thereof.
These weak acids usually have the structure H.sub.a E.sub.b O.sub.c,
wherein H and 0 stand for hydrogen and oxygen respectively, and
E is the said element. a, b and c are such that the structure is
neutral. Salts thereof, such as with Na, K, Ca, Al, NH.sub.3 etc.
can also be used. Suitably the modifying agent is chosen from the
group of boric acid, silicic acid, acids of phosphor and salts thereof,
more in particular it is H.sub.3 BO.sub.3 NaH.sub.2 PO.sub.2 Na.sub.4
P.sub.2 O.sub.7.10H.sub.2 O, K.sub.3 PO.sub.4 (NH.sub.4).sub.2
HPO.sub.2 Na.sub.2 B.sub.4 O.sub.7.10H.sub.2 O and Si(OH).sub.4
It is also possible to use derivatives of the weak acids, such as
acid halides.
The amount of modifying agent can vary within wide ranges and is
mainly determined by the degree of modification that is required.
Preferred ranges of the weight ratio of molecular sieve to modifying
agent are between 100:1 and 1:1 more in particular 10:1 to 3:1.
These ratio applies to the amount of molecular sieve and the amount
of dry modifying agent, not taking into account any liquid that
can be used in the process. The amount of liquid is of influence
on the results obtained.
Generally the ratio of liquid (if used) to modifying agent ranges
from 400:1 to 1:20. Preferably the ratio of liquid, more in particular
water, to molecular sieve ranges from 2 to 0.25 whereby the ratio
of 1.25 to 0.8 is especially preferred. The reason for this preference
lies therein, that within these ratios the best results are obtained.
Higher amounts of liquid than twice the amount of molecular sieve
can be used, but do not give any added advantages.
The modified molecular sieve can be used for various purposes.
It is possible to apply it as a catalyst for chemical reactions,
optionally after the outer surface has been made inert. Another
application is the separation or storage of gases. The modified
molecular sieves can also be used as selective ion exchangers in
liquids, or to purify liquids.
The invention will now be elucidated on the basis of some examples.
EXAMPLE 1
3 grams of the parent sample, Ca A from Ethyl Company, were dehydrated
at 370.degree. C. in vacuum overnight. The adsorption kinetics of
CH.sub.4 were investigated at 0.degree. C. (FIG. 1). 3 grams of
this parent sample (particle size <150/.mu.m) were mixed with
0.15 grams boric acid powder. After adding 3 ml of water the mixture
was stirred during a few minutes, dried at 105.degree. C. in air
for 1 hour and heated for 2 hours at 400.degree. C. in air. 2 grams
of this modified sample were dehydrated overnight in vacuum at 368.degree.
C. As shown in FIG. 1 one observes a decrease in the adsorption
capacity for CH.sub.4 at 0.degree. C.
EXAMPLE 2
2 grams of Na-mordenite SP (E127Nam 543:SCGP) were outgassed overnight
at 420.degree. C. in high vacuum and tested for its adsorption behaviour.
The sorption characteristics for Kr at 0.degree. C. are shown in
FIG. 2. 3 grams of the parent sample (fraction <150/.mu.m) were
mixed with 0.15 g powdered boric acid and stirred with 3 ml H.sub.2
O for a few minutes at room temperature. Then the sample was thermally
treated for 1 hour at 110.degree. C. and for 2 hours at 400.degree.
C., both in air. 2 g of this modified sample were dehydrated at
450.degree. C. overnight in vacuum to investigate the sorption behaviour
for Kr. FIG. 2 shows a capacity decrease for said gas.
EXAMPLE 3
2 g of the parent sample, CaM CM782 (SCGP, extrudates) were dehydrated
in vacuum overnight at 450.degree. C. FIG. 3 shows the observed
sorption characteristics for Xe at 0.degree. C. No equilibrium was
observed after 25 min. 3 g of the parent sample (fraction <150/.mu.m)
were mixed with 0.15 g boric acid powder and stirred with 3 ml H.sub.2
O at room temperature. Afterwards, the sample was thermally treated
for 1 hour at 105.degree. C. and for 2 hours at 400.degree. C.,
both in air. 2 g of this sample were dehydrated overnight at 454.degree.
C. in vacuum to study the adsorption kinetics of Xe. FIG. 3 shows
a capacity decrease.
EXAMPLE 4
50 g of E127NaM 543 from SCGP were exchanged for Ba.sup.2 with
65 g of Ba(NO.sub.3).sub.2 into 1 1 of water at room temperature
during 1 night. 2 g of this batch were outgassed overnight in vacuum
at 450.degree. C. and tested for its adsorption behaviour with Xe
at 0.degree. C. (FIG. 4). The adsorption of Xe after 25 min is 1.473
mmol/g. 3 g of the parent sample were mixed with 0.15 g powdered
boric acid and stirred with 3 ml H.sub.2 O at room temperature.
Afterwards the sample was heated for 1 hour at 110.degree. C. and
for 2 hours at 400.degree. C., both in air. 2 g of this treated
sample were dehydrated at 450.degree. C. overnight in vacuum. As
shown in FIG. 4 the decrease in adsorption capacity for Xe was important.
The sorption value of Xe after 25 min is only 0.079 mmol/g.
EXAMPLE 5
2 g of the parent sample, CaM CM782 (SCGP, extrudates) were dehydrated
in vacuum overnight at 450.degree. C. The adsorption behaviour of
this sample was tested for CH.sub.4 at 0.degree. C. (FIG. 5).
A. Particle size >800/.mu.m
3 g of the parent sample (fraction >800/.mu.m) were mixed with
0.15 g H.sub.3 BO.sub.3 - powder. After adding 3 ml of H.sub.2 O,
the slurry was mixed and dried during 1 hour at 105.degree. C. in
air. The dried sample was heated at 400.degree. C. for 2 hours in
air. 2 g of this modified sample were dehydrated at 463.degree.
C. overnight in vacuum. FIG. 6 shows the kinetic runs of CH.sub.4
at 0.degree. C. One observes a decrease in the sorption capacity.
B. Particle size 250-800/.mu.m
3 g of the parent sample (fraction 250-800/.mu.m) were mixed with
0.15 g H.sub.3 BO.sub.3 -powder. Afterwards 3 ml of H.sub.2 O was
added and the slurry was mixed and dried during 1 hour at 105.degree.
C. in air. The dried sample was heated at 400.degree. C. for 2 hours
in air. 2 g of this modified sample were dehydrated at 450.degree.
C. overnight in vacuum. The adsorption kinetics of CH.sub.4 are
shown in FIG. 6. Compared to the modification with a fraction >800/.mu.m,
one observes a lower sorption capacity.
C. Particle size <150/.mu.m
3 g of the parent sample (fraction <150/.mu.m) were mixed with
0.15 g H.sub.3 BO.sub.3 -powder. After adding 3 ml of H.sub.2 O,
the slurry was mixed and dried during 1 hour at 105.degree. C. in
air. The dried sample was heated at 400.degree. C. for 2 hours in
air. 2 g of this sample were dehydrated at 454.degree. C. overnight
in vacuum.
FIG. 6 shows the kinetic runs of CH.sub.4 at 0.degree. C.
EXAMPLE 6
The parent sample used in this example was E127NaM 543 treated
with an aqueous KN03 solution. The Na.sup.+ -ions were exchanged
for K.sup.+ -ions using 100 g KNO.sub.3 and 50 g sample E127 in
0.5 1 of H.sub.2 O for 1 night at room temperature.
2 g of this exchanged sample (extrudates) were dehydrated in vacuum
at 435.degree. C. overnight. The adsorption behaviour was tested
for Xe at 0.degree. C. (FIG. 7). An equilibrium situation was reached
after 36 min.
2 g of the parent sample (fraction 250-800/.mu.m) were mixed with
0.2 g K.sub.3 PO.sub.4 dry. Then 2 ml of H.sub.2 O were added and
mixed. The sample was first dried during 1 hour at 100.degree. C.
in air and afterwards treated at 500.degree. C. for 2 hours in air.
After dehydration the adsorption characteristics were investigated
(FIG. 7). Xe was excluded.
EXAMPLE 7
2 g of the parent sample, E126NaM 543 were dehydrated at 440.degree.
C. for one night in vacuum. The kinetic runs of Xe were investigated
at 0.degree. C. (FIG. 8). An equilibrium situation is reached after
25 min and it shows a high adsorption capacity. 3.1 g of the parent
sample (fraction <150/.mu.m) were mixed with 0.3 g (NH.sub.4).sub.2
HPO.sub.4. After mixing with 3 ml of H.sub.2 O the substrate was
dried at 100.degree. C. in air. A thermal treatment of 2 hours at
500.degree. C. in air was the next experimental manipulation before
dehydrating the sample in vacuum at 455.degree. C. overnight. The
adsorption of Xe was again investigated on this modified sample
at 0.degree. C. The modified sample shows a decrease in the adsorption
capacity, but especially a strong diffusion-controlled sorption
process for Xe at 0.degree. C. (FIG. 8).
EXAMPLE 8
2 g of the parent sample. CaM CM782 (SCGP, extrudates), were dehydrated
in vacuum overnight at 450.degree. C. FIG. 9 shows the observed
sorption characteristics of CH.sub.4 at 0.degree. C. 3 g of the
parent sample (fraction <150/.mu.m) were mixed with 0.075 g H.sub.3
BO.sub.3 (2.5% weight) and stirred with 3 ml of H.sub.2 O at room
temperature. Then the sample was evaporated for 1 hour at 100.degree.
C. in air and thermally treated for 2 hours at 400.degree. C. also
in air.
2 g of this modified sample were dehydrated overnight at 457.degree.
C. in vacuum. FIG. 10 shows a decrease in the adsorption of CH.sub.4
at 0.degree. C. after modification.
EXAMPLE 9
3 g of the parent sample (cfr. Example 8 (fraction <150/.mu.m)
were mixed with 0.15 g H.sub.3 BO.sub.3 (5% weight) and stirred
with 3 ml of H.sub.2 O at room temperature. Afterwards the sample
was thermally treated for 1 hour at 100.degree. C. and for 2 hours
at 400.degree. C. both in air.
2 g of this treated sample were dehydrated overnight at 454.degree.
C. in vacuum.
At this modified degree one observes for CH.sub.4 a larger capacity
decrease compared to that in Example 8 (FIG. 10).
EXAMPLE 10
3 g of the parent sample (cfr. Example 8) (fraction <150/.mu.m)
were mixed with 0.3 g H.sub.3 BO.sub.3 (10% weight) and stirred
with 3 ml of H.sub.2 O at room temperature. Afterwards, the sample
was thermally treated for 1 hour at 100.degree. C. and for 2 hours
at 400.degree. C., both in air. 2 g of this treated sample were
dehydrated at 455.degree. C. overnight, to investigate the kinetic
run of CH.sub.4 at 0.degree. C. (FIG. 10). With this modification
CH.sub.4 shows at this adsorption temperature not only an enormous
capacity decrease but the adsorption is also strongly diffusion-controlled.
EXAMPLE A (comparative)
The parent sample used in this experiment was CaM CM782 (SCGP;
extrudates).
2 g of the sample were dehydrated overnight at 450.degree. C. in
vacuum in order to investigate its adsorption behavious. FIG. 11
shows the sorption kinetics of Xe at 0.degree. C. 3 g CaM CM782
(fraction <150/.mu.m) were treated for 1 hour and 30 min at 90.degree.
C. in a H.sub.3 BO.sub.3 -solution (0.15 g H.sub.3 BO.sub.3 in 40
ml H.sub.2 O). After cooling to room temperature the residual solution
was decanted and the sample was dried at 60.degree. C. in air. The
dried material was thermally treated for 2 hours at 400.degree.
C. in air.
2 g of this modified substrate were dehydrated at 449.degree. C.
overnight in vacuum. The kinetic run of Xe at 0.degree. C. was investigated
on the modified sample (FIG. 11). One observes only a small capacity
decrease.
EXAMPLE 11
Parent sample : same as in Example 10.
3 g of the parent sample (fraction <150/.mu.m) were mixed with
0.15 g H.sub.3 BO.sub.3 and stirred with 3 ml of H.sub.2 O at room
temperature. Afterwards the sample was thermally treated for 1 hour
at 100.degree. C. and for 2 hours at 400.degree. C., both in air.
2 g of this treated sample were dehydrated overnight at 454.degree.
C. in vacuum.
As shown in FIG. 12 the adsorption kinetics of Xe at 0.degree.
C. reveal a capacity decrease.
EXAMPLE 12
2 g of the parent sample CaM CM782 (SCGP, extrudates) were dehydrated
overnight at 450.degree. C. in vacuum. The kinetic runs of Xe and
CH.sub.4 at 0.degree. C. were tested, both gases are still adsorbing
after 25 min. The sorption value for CH.sub.4 after 25 min is 0.762
mmol/g. (FIG. 13). (a) 3 g of the parent sample (fraction <150/.mu.m)
were mixed with 0.15 g powdered H.sub.3 BO.sub.3 and stirred with
3 ml of H.sub.2 O at room temperature. Afterwards the substrate
was thermally treated for 1 hour at 100.degree. C. and for 2 hours
at 300.degree. C., both in air. 2 g of this modified sample were
dehydrated overnight at 444.degree. C. in vacuum to investigate
the adsorption behaviour for CH.sub.4 at 0.degree. C. (FIG. 23).
The sorption value of CH.sub.4 after 25 min is 0.351 mmol/g. (b)
3 g of the parent sample (fraction <150/.mu.m) were mixed with
0.15 g H.sub.3 BO.sub.3 -powder and stirred with 3 ml of H.sub.2
O at room temperature. Afterwards the substrate was thermally treated
for 1 hour at 100.degree. C. and for 2 hours at 400.degree. C.,
both in air. 2 g of this modified sample were dehydrated overnight
at 454.degree. C. in vacuum. FIG. 13 shows a capacity decrease at
0.degree. C. After modification the sorption value after 25 min
of CH.sub.4 is 0.303 mmol/g.
EXAMPLE 13
In this experiment the parent sample was CaM CM782 (SCGP, extrudates).
2 g of the parent sample were dehydrated overnight at 450.degree.
C. in vacuum to investigate its adsorption behaviour for Xe at 0.degree.
C. (FIG. 14).
(a) 3 g of the parent sample (fraction <150/.mu.m) were mixed
with 0.15 g H.sub.3 BO.sub.3 and with 3 ml of water at room temperature.
Afterwards the sample was thermally treated for 1 hour at 100.degree.
C. and for 30 min at 400.degree. C., both in air. After a dehydration
(overnight, at 444.degree. C., in vacuum) of the sample the kinetic
run of Xe at 0.degree. C. were investigated (FIG. 14). A decrease
of sorption capacity after the modification is observed.
(b) 3 g of the parent sample (fraction <150/.mu.m) were mixed
with 0.15 g H.sub.3 BO.sub.3 and stirred with 3 ml of H.sub.2 O
at room temperature. Then the sample was thermally treated for 1
hour at 100.degree. C. and for 2 hours at 400.degree. C., both in
air. 2 g of this modified sample were dehydrated at 454.degree.
C. overnight in vacuum. FIG. 14 shows the adsorption kinetics of
Xe at 0.degree. C. after the modification.
Comparing to Example 13 the sorption values of Xe are a little
lower on this modified sample, due to the longer thermal treatment
time.
EXAMPLE 14
2 g of the parent sample, CaM CM 782 (SCGP, extrudates) were dehydrated
overnight at 450.degree. C. in vacuum. FIG. 15 shows the observed
sorption characteristics for Xe at 0.degree. C. After 16 min Xe
is still adsorbing.
3.1 g of the parent sample (fraction <150/.mu.m) were mixed
with 0.3 g H.sub.3 BO.sub.3 (10% weight) and stirred with 3 ml H.sub.2
O at room temperature. Afterwards the sample was thermally treated
for 1 hour at 100.degree. C. and for 3 hours at 400.degree. C.,
both in air. 2 g of this sample were dehydrated overnight at 427.degree.
C. in vacuum. FIG. 15 shows exclusion for Xe.
EXAMPLE 15
The parent sample, CaM CM782 (SCGP: extrudates) was dehydrated
overnight at 450.degree. C. in vacuum. FIG. 16 shows the observed
sorption characteristics for Xe at 0.degree. C. After 16 min Xe
is still adsorbing.
3 g of the parent sample (fraction <150/.mu.m) were mixed with
0.3 g H.sub.3 BO.sub.3 (10% weight) and stirred with 3 ml H.sub.2
O at room temperature. Afterwards the sample was thermally treated
for 2 hours at 100.degree. C. in air. The thermal treatment at 455.degree.
C. was carried out overnight in vacuum. FIG. 16 shows the obtained
adsorption behaviour. A capacity decrease occurs with diffusion-controlled
adsorption for Xe. The pore-narrowing of this sample is not so effective
as the one in Example 14 although the same amount of boric acid
was used.
EXAMPLE 16
3 grams of the parent sample NH.sub.4 -exchanged CM 790 were mixed
with 0.9 grams dry Na.sub.2 SiO.sub.3.9H.sub.2 O. Then 3 ml of H.sub.2
O was added and the obtained slurry was mixed again. The sample
was first dried during 1 hour at 100.degree. C. in air and afterwards
at 500.degree. C. for 2 hours in air. The same procedure was used
for the other samples. Instead of 3 ml H.sub.2 O; respectively no
water and 2 ml of water were added to the mixture of zeolite and
modifying agent. After dehydration (overnight, 450.degree., vacuum)
of the modified samples, the adsorption characteristics were investigated
for N.sub.2 and O.sub.2 at 0.degree. C. as shown in FIGS. 17 18
and 19. Increasing the amount of H.sub.2 O introduces a diffusion-controlled
adsorption especially for N.sub.2. |