Molecular sieve abstract
Molecular sieve agglomerates that can have improved physical and
chemical properties are prepared by methods which comprise contacting
the agglomerates with an alkali metal silicate solution. Molecular
sieve agglomerates which comprise binders such as kaolin can additionally
be contacted with an alkali hydroxide solution to convert the kaolin
to Zeolite A prior to contacting the agglomerates with the alkali
metal silicate solution to further improve properties. The molecular
sieve agglomerates prepared according to the present invention are
suitable for use as refrigerant desiccants.
Molecular sieve claims
We claim:
1. Method for preparing attrition resistant molecular sieve agglomerates
comprising:
(a) forming an initial molecular sieve agglomerate comprising a
zeolite and a binder comprising kaolin clay;
(b) heating the initial agglomerate at a temperature of from about
550.degree.-650.degree. C. and sufficient to set the binder and
form a calcined agglomerate;
(c) contacting said calcined agglomerate with an alkali hydroxide
solution comprising from about 5 to about 50% by weight of sodium
hydroxide at conditions effective to convert the kaolin binder to
Zeolite A to form a converted agglomerate;
(d) contacting the converted agglomerate with an aqueous alkali
metal silicate solution containing from about 1 to 10 wt. % alkali
metal oxide and from about 2 to 20 wt. % silicon dioxide to form
a treated agglomerate; and
(e) drying the treated agglomerate at a temperature of from about
ambient temperature to 650.degree. C. and sufficient to remove water
therefrom.
2. Method of claim 1 wherein said zeolite is the potassium-exchanged
form of Zeolite A having uniform pore diameters of about 3 Angstroms.
3. Method of claim 1 wherein said zeolite is the sodium-exchanged
form of Zeolite A having uniform pore diameters of about 4 Angstroms.
4. Method of claim 1 wherein the binder comprises from about 5
percent to about 40 percent by weight of said initial agglomerate.
5. Method of claim 1 wherein the alkali metal oxide is potassium
oxide.
6. Method of claim 1 wherein said drying is conducted by heating
in air to a temperature of from about 200.degree. C. to 650.degree.
C.
7. Method of claim 1 wherein the alkali hydroxide solution comprises
from about 5 to about 10 percent by weight of sodium hydroxide.
8. Method of claim 1 wherein said contacting is performed at a
temperature of from about 40.degree. C. to about 110.degree. C.
9. Method of claim 8 wherein said contacting is performed at a
temperature of from about 90.degree. C. to about 95.degree. C.
10. Method of claim 1 which further comprises contacting said converted
agglomerate with a sufficient quantity of water to have a pH of
between about 9 to about 12 prior to said contacting with the alkali
metal silicate solution.
11. Method of claim 10 wherein the pH of the converted agglomerate
is about 10.
Molecular sieve description
FIELD OF THE INVENTION
The present invention relates to molecular sieve agglomerates and
more particularly to methods for treating molecular sieve agglomerates
that can provide improved physical and chemical properties.
BACKGROUND OF THE INVENTION
Crystalline molecular sieves occur naturally or are synthesized
as fine crystalline bodies which for general utility in commercial
adsorptive or catalytic processes are usually formed into agglomerates,
preferably possessing as high a degree of attrition resistance and
crush strength as possible without unduly affecting the adsorptive
properties of the sieves. One method of agglomerating these finely
crystalline materials is by combining them with a clay binder as
described in U.S. Pat. No. 2973327 issued Feb. 28 1961 in the
name of W. J. Mitchell, et al. Whereas this prior technique provides
a suitable agglomerate for a wide variety of industrial applications,
it has been found that certain applications having a very low tolerance
for attrition-produced particles or dust require a more strongly
bound molecular sieve agglomerate.
Moreover, in certain other processes, e.g. refrigerant drying,
environments exist which are chemically incompatible with some molecular
sieve agglomerates. Refrigerants often contain halogenated hydrocarbons
which can decompose and the decomposition products, e.g., hydrogen
fluoride and hydrogen chloride, can react with both the internal
active sites in the molecular sieve as well as the binder.
As a result of the above-described problems, processes have been
developed to improve both the physical properties, i.e., crush strength
and attrition resistance, and chemical properties, i.e., compatibility
with halogenated refrigerants, of molecular sieve agglomerates.
U.S. Pat. No. 3536521 discloses a silicone coated molecular sieve
and method for preparing same wherein a silicone coating is applied
to the surface of a molecular sieve by dissolving a silicone oil
in an appropriate solvent, adding the sieves to the resulting solution
and evaporating the solvent, leaving a uniform silicone deposit
on the sieve surface. The sieve is then thermally activated for
use as a drying agent. The above-identified patent discloses that
certain gases, e.g., refrigerants, are not adsorbed on the coated
surface. However, no disclosure is provided relating to attrition
and other physical breakage problems, nor to subsequent chemical
attack of the new surfaces after such breakage has occurred.
Other methods have been proposed to incorporate silicon on the
surfaces throughout the molecular sieve agglomerates to provide
improved physical strength as well as chemical resistance. These
methods commonly involve incorporating a silicate treatment step,
i.e., contacting with an aqueous alkali metal silicate solution,
into the molecular sieve agglomerate manufacturing procedure.
For example, U.S. Pat. No. 3624003 discloses molecular sieve
agglomerates and methods for preparing same wherein improved, attrition
resistant desiccant bodies are prepared by the process which comprises
applying to the outer surface of a crystalline zeolitic molecular
sieve agglomerate an essentially continuous coating of a finely
divided inert alpha-alumina monohydrate which has been thermally
treated at temperatures of from about 250.degree. C. to 350.degree.
C. to reduce the surface activity thereof, contacting and impregnating
at least the coating of the agglomerate thus formed with an aqueous
solution of potassium silicate, drying the potassium silicate impregnated
agglomerate to remove a substantial portion of water therein, and
thereafter firing the resulting composite agglomerate to set and
harden the silicate and activate the molecular sieve. This firing,
or heating step, is sometimes referred to as calcination.
Similarly, U.S. Pat. No. 3625886 discloses molecular sieve agglomerates
and methods for preparing same, however this patent discloses the
use of a mixture of disapore, i.e., beta-alumina monohydrate, and
a clay mineral, instead of the alpha-alumina monohydrate disclosed
in U.S. Pat. No. 3624003.
Both of the above-identified patents disclose that the silicate
treatment step is performed on the agglomerates prior to the heating
step which sets, or hardens, the binder. That is, the silicate treatment
is an integral step in the molecular sieve agglomerate manufacturing
procedure.
Other patents also disclose this process sequence. British Patent
Specification 972833 discloses a method for hardening a crystalline
zeolite molecular sieve agglomerate formed of such zeolite molecular
sieve and a clay mineral binder, which comprises contacting the
agglomerate in a hydrated state with an aqueous solution of an alkali
metal silicate having a solid content of from 3% to 35% by weight
to impregnate the agglomerate with the alkali metal silicate, separating
the impregnated agglomerate from the solution and firing such impregnated
agglomerate at a temperature of at least 343.degree. C. and below
the temperature at which the crystalline zeolitic molecular sieve
loses its structural ability.
Also, U.S. Pat. No. 4405503 discloses a method for strengthening
zeolitic molecular sieve agglomerates, particularly of the bound
variety, which enables them to retain (a) their strength to a satisfactory
extent despite subsequent acid treatment and (b) their suitability
for use as a catalyst support. The method comprises treating the
agglomerate with an aqueous solution of water soluble silicon compound
and subsequently with an aqueous solution of a mineral acid of sufficient
strength to decationize the zeolitic molecular sieve and/or increase
its SiO.sub.2 :Al.sub.2 O.sub.3 ratio. The decationized zeolitic
molecular sieve is thereafter calcined.
Although the above-described methods for treating molecular sieve
agglomerates have been useful, new methods are sought which could
be performed subsequently to the binder setting step, e.g., calcination
step. Such a method could be utilized in existing manufacturing
facilities where intermediate method steps may not be conveniently
implemented. Moreover, such a processing sequence could result in
a high degree of product consistency, i.e., little variation in
physical and chemical properties.
SUMMARY OF THE INVENTION
Methods are provided for treating molecular sieve agglomerates
in order to provide an improvement in at least one physical or chemical
property, preferably improved attrition resistance, crush strength,
water adsorption capacity and compatibility with halogenated refrigerants,
which comprises contacting an initial agglomerate comprising molecular
sieve and binder which had been previously heated to set the binder
with an aqueous alkali metal silicate solution, and thereafter drying
the agglomerate to remove water therefrom.
In one preferred aspect, the method comprises contacting the initial
agglomerate which contains zeolite, preferably the sodium-exchanged
or potassium-exchanged forms of Zeolite A, and a clay binder, preferably
kaolin, attapulgite and mixtures thereof, with a potassium silicate
solution to form a treated agglomerate, and thereafter drying the
treated agglomerate by heating in air to a temperature of from about
200.degree. C. to 650.degree. C.
In another preferred aspect, the method further comprises contacting
the initial agglomerate which contains zeolite and a kaolin clay
binder, prior to the alkali metal silicate solution contacting,
with an alkali hydroxide solution, preferably a sodium hydroxide
solution comprising from about 5 to about 50 weight percent, more
preferably from about 5 to about 10 weight percent sodium hydroxide
at conditions effective to convert the kaolin to Zeolite A and form
a converted agglomerate, said contacting preferably performed at
a temperature of from about 40.degree. C. to 110.degree. C. and
more preferably from about 90.degree. C. to 95.degree. C., and thereafter
contacting the converted agglomerate with a sufficient quantity
of water to have a pH of between about 9 to 12 and more preferably
about 10.
DESCRIPTION OF THE INVENTION
The present invention provides molecular sieve agglomerates that
can have improved physical and chemical properties and methods for
preparing the agglomerates. Preferably, the improved properties
obtained in accordance with the present invention are at least one
of improved attrition resistance, improved crush strength, improved
water adsorption capacity and improved chemical resistance to halogenated
refrigerants.
The molecular sieves suitable for use according to the present
invention include the various forms of silicoaluminophosphates,
and aluminophosphates disclosed in U.S. Pat. Nos. 4440871 4310440
and 4567027 hereby incorporated by reference, as well as zeolitic
molecular sieves, which are preferred.
Zeolitic molecular sieves in the calcined form may be represented
by the general formula: ##EQU1## where Me is a cation, x has a value
from about 2 to infinity and y has a value of from about 2 to 10.
Typical well known zeolites which may be used include, chabazite,
also referred to as Zeolite D, clinoptilolite, erionite, faujasite,
also referred to as Zeolite X and Zeolite Y, ferrierite, mordenite,
Zeolite A, and Zeolite P. Detailed descriptions of the above-identified
zeolites, as well as others, may be found in D. W. Breck, Zeolite
Molecular Sieves, John Wiley and Sons, New York, 1974 hereby incorporated
by reference. Other zeolites suitable for use according to the present
invention are those having a high silica content, i.e., those having
silica to alumina ratios greater than 10 and typically greater than
100. One such high silica zeolite is silicalite, as the term used
herein includes both the silicapolymorph disclosed in U.S. Pat.
No. 4061724 and also the F-silicalite disclosed in U.S. Pat. No.
4104294 hereby incorporated by reference.
It is especially preferred that for use in drying halogenated refrigerants
the agglomerates of the present invention contain as the zeolitic
molecular sieve the species known as Zeolite 3A, which has uniform
pore diameter of about 3 Angstroms, Zeolite 4A, which has uniform
pore diameters of about 4 Angstroms, and mixtures thereof. Zeolite
3A can be prepared from the sodium cation form of Zeolite A, i.e.,
Zeolite 4A, by replacing at least 65 equivalent percent of the sodium
cations with potassium cations by conventional cation exchange techniques.
Both Zeolite 3A and Zeolite 4A, as well as methods for their preparation
are disclosed by D. W. Breck, supra, and are available from UOP,
Des Plaines, Ill.
For purposes of the present invention it is desired that the solid
adsorbent be agglomerated with a binder in order to ensure that
the molecular sieve will have suitable physical properties. Although
there are a variety of synthetic and naturally occurring binder
materials available such as metal oxides, clays, silicas, aluminas,
silica-aluminas, silica-zirconias, silica-thorisas, silica-berylias,
silica-titanias, silica-alumina-thorias, silica-alumina-zirconias,
mixtures of these and the like, clay type binders are preferred.
Examples of clays which may be employed to agglomerate the zeolites
without substantially altering the adsorptive properties of the
zeolite are attapulgite, kaolin, volclay, sepiolite, halloysite,
palygorskite, ball clays, bentonite, montmorillonite, illite and
chlorite. Kaolin and attapulgite binders are particularly preferred
for practicing the present invention and may be obtained from UOP,
Des Plaines, Ill. Fibrous additives such as kaowool or glass fibers
may also be optionally used with the binder.
When clay binders are utilized, the amount of clay with respect
to molecular sieve in the preferred starting agglomerate depends
primarily upon the degree of dilution of the molecular sieve permissible
in a desired use of the final product. For most purposes, a clay
content of from 5 percent to 40 percent by weight of the final product
is satisfactory. Preferably, the clay content will be from about
10 percent to about 25 percent by weight of the molecular sieve
agglomerate.
After the molecular sieve is mixed with the binder in the desired
proportions, the mixture is then formed into an agglomerate, typically
by extrusion or bead formation. These formed agglomerates are commonly
referred to as "green" agglomerates. Next, the green agglomerates
are typically heated to a temperature sufficient to set the binder
and cause hardening thereof thereby forming the initial agglomerates
of the present invention. This heating step is sometimes referred
to as calcination. The temperature required to set the binder depends
on what binder is used. For example, a temperature of about 200.degree.
C. is required to set most silica binders. On the other hand, a
temperature of from about 500.degree. C. to about 700.degree. C.
is required to set most clay binders. When kaolin clays are used,
it is preferred that the binder be set at a temperature of from
about 550.degree. C. to 650.degree. C. The details of the above-described
techniques in forming molecular sieve agglomerates are well known
to those skilled in molecular sieve technology.
Unlike methods previously proposed for treating molecular sieve
agglomerates with silicate solutions, the method of the present
invention does not require that the silicate treatment be performed
prior to the heating step which sets, or hardens, the binder in
the agglomerate. In fact, in accordance with the present invention,
the silicate treatment is advantageously performed subsequently
to the setting of the binder. As a result, it is possible to practice
the present invention using existing, i.e., hardened, molecular
sieve agglomerates. Accordingly, the method of the present invention
can be utilized in existing manufacturing facilities where intermediate
method steps may not be conveniently implemented. Moreover, such
a processing sequence can result in a high degree of product consistency,
i.e, little variation in physical and chemical properties.
In accordance with the present invention, the initial agglomerate
which has been previously subjected to heating at an elevated temperature
sufficient to set the binder is thereafter contacted or soaked in
an aqueous alkali metal silicate solution, such as sodium silicate
or potassium silicate, to form a treated agglomerate. Potassium
silicate is preferred, particularly when Zeolite 4A is treated,
because in addition to providing improved physical properties, e.g.
crush strength and attrition resistance, the potassium cations in
the potassium silicate solution can ion-exchange with the sodium
cations in the Zeolite 4A, thereby reducing the pore size to 3 Angstroms
and improving the chemical resistance to halogenated refrigerants
which are not as easily adsorbed into the 3 Angstrom pores. It is,
of course, possible to introduce the silicon compounds as colloidal
silica in suspension in the impregnating solution, however this
may not materially improve the product, nor will it facilitate ion-exchange
if such ion-exchange is desired.
The solid content of the silicate solution which is the sum of
weight percent of the alkali metal oxide and the silicon dioxide
in the solution may be from about 2 to about 30 weight percent.
Lower than about 2 percent will not provide a sufficient introduction
of silicate into the agglomerate to materially improve the crush
strength, while more than about 30 percent can lead to a loss of
adsorption capacity of the contained molecular sieve. The alkali
metal oxide may be present in the range to provide about 0.4 to
about 0.6 pounds alkali metal oxide per pound of silicon dioxide.
Ratios lower than about 0.4 may be used but are not preferred because
they tend to have increasing amounts of the silcone dioxide present
in undissolved form. Typically, alkali metal silicate solutions
may contain from about 1 to about 10 weight percent alkali metal
oxide and from about 2 to about 20 weight percent silicon dioxide.
Within the above ranges of ratio of oxides and solid contents of
the solution, the quantity of solution employed to impregnate a
quantity of coated molecular sieve agglomerate may be in the range
to provide from about 0.1 to about 0.5 pounds of solution solid
per pound of agglomerate.
The contacting or soaking of the agglomerates in the silicate solution
may be either batch-type or continuous. When batchwise contacting
is employed, it is desirable to provide agitation for uniformity.
Such agitation may be conducted by stirring the solution with moderation,
to avoid breaking up the agglomerates.
Continuous contacting is conveniently accomplished by percolating
the solution through a chamber containing the agglomerates. In the
continuous-contact method the concentration of the solids in the
silicate solution may be in the lower concentration range and the
solution can be replenished as the solids are depleted.
The immersion may be hot or cold, the advantage of heat being that
shorter contacting time may be employed but the disadvantage is
the increased tendency toward alkali attack on the crystal structure
of the zeolitic molecular sieve. Temperatures below about 60.degree.
C., preferably below about 40.degree. C., are desired to reduce
this attack, particularly when the alkali metal oxide to silicon
dioxide ratio is high.
The amount of silicate impregnated into the agglomerates is affected
by all of the variables in the instant method and the time of contacting.
In some instances when using concentrated treating solutions, elevated
temperatures, and very porous agglomerates, an immersion time of
a few minutes is satisfactory. Longer contacting times will generally
result in an increase in the quantity of silicate entering the agglomerate
and the distance of penetration of the silicate into the agglomerate.
The time may extend to several hours or even several days, if desired,
provided that the integrity of the agglomerate or the molecular
sieve crystal is not affected. Increase in either or both the concentration
and distance of the penetration will increase the final crush strength
of the product.
It is readily seen that by employing short immersion times in the
practice of this invention, one can make a product having a hardened,
abrasion-resistant exterior on the agglomerates which is entirely
satisfactory for applications where this property is desired. On
the other hand, longer contact times will effect a somewhat deeper
hardening, which is preferred for maximum crush strength.
Following the immersion step, the agglomerates are separated from
the treating solution and may, if desired, be given a brief water
rinse which will remove just enough of the solution adhering to
the outer surface of the agglomerates to eliminate the tendency
of the agglomerates to adhere to each other.
After the agglomerates have been separated from the silicate solution,
they are to be dried in order to remove water therefrom. Such drying
can be accomplished in a number of ways, for example, the agglomerates
can be allowed to dry in air or purged with suitable drying gas
such as nitrogen. Preferably, the agglomerates are heated at an
elevated temperature, preferably between about 200.degree. C. and
650.degree. C. and most preferably between about 500.degree. C.
to 650.degree. C. The final drying temperature is determined by
the desired water content remaining on the molecular sieve agglomerate,
i.e., higher drying temperatures result in lower water content.
Another aspect of the present invention provides molecular sieve
agglomerates that can have even further improved physical and chemical
properties and methods for their production. This aspect relates
specifically to the conversion of a binder, preferably kaolin, to
a zeolite and comprises an additional processing step wherein the
initial agglomerate is contacted with an alkali hydroxide solution
at conditions effective to convert the binder to Zeolite A, thereby
forming a converted binder. Although kaolin is a preferred binder
for this purpose, other binders having a silica to alumina ratio
similar to zeolite, i.e., from about 1 to about 4 may also be suitable.
Such binders would include, for example, halloysite and montmorillonite.
The converted binder is thereafter contacted with the alkali metal
silicate solution as hereinbefore described.
The alkali hydroxide solution preferably comprises from about 5
to about 50 percent, and more preferably about 5 to about 10 percent
by weight of sodium hydroxide. Sodium hydroxide is preferred because
the sodium ions are effective to convert the binder to Zeolite 4A.
However, it can be appreciated that potassium hydroxide may be used
when it is desired to produce Zeolite 3A. The contacting of said
initial agglomerate with the alkali hydroxide solution is preferably
performed at a temperature of from about 40.degree. C. to about
110.degree. C. and more preferably at a temperature of from about
90.degree. C. to about 95.degree. C. and for a time sufficient to
substantially convert the binder to Zeolite A. It can be appreciated
that the time required to convert the binder is variable and dependent
on such factors as the concentration of the alkali hydroxide solution
and the amount of binder in the initial agglomerate. Although the
appropriate contacting time can be determined by testing the agglomerate
at various times during the contacting, in general contacting times
of from about 1 to about 6 hours are sufficient. D. W. Breck, supra,
at pages 731 to 734 describes the kaolin clay conversion process
to Zeolite A, i.e., the dehydroxylation of kaolin to metakaolin
which occurs upon heating the binder, followed by the conversion
of metakaolin to Zeolite A by treatment with alkali hydroxide.
After the binder has been converted to Zeolite A, it is desirable
to contact the converted agglomerate with a sufficient quantity
of water to remove excess alkali hydroxide solution prior to said
contacting with the alkali metal silicate solution. This contacting
is preferably continued until the pH of the converted agglomerate
is between about 9 to about 12 and more preferably to a pH of about
10.
In assessing the exceptional physical properties of the agglomerates
of this invention, a number of test procedures were employed. Both
activated agglomerate beads, i.e., purged with nitrogen at 350.degree.
C. for about 10 hours, and hydrated beads, i.e., 15 to 20 weight
percent water, were used for some of the tests. They are as follows:
1. Paint Shaker Attrition Test
This test measures principally attrition strength. In accordance
with the procedure, 136 ml of desiccant beads are placed in a cylindrical
150 ml container having a diameter of 4.4 cm. and a height of 10
cm. 68 ml. of trichloroethylene are added, the container closed,
and subjected to a high frequency swirling motion in a model No.
30 Red Devil Paint Conditioner (manufactured by Red Devil Tools,
Union, N.J.) for 120 minutes. The fines produced by attrition are
thereafter washed from the beads with additional trichloroethylene
through a No. 100 U.S. Standard Sieve into a beaker, isolated from
the trichloroethylene, heated to 350.degree. C. to activate the
sieve, and weighed. The weight obtained, expressed as a weight percent
of the initial charge of desiccant beads is taken as the measure
of the paint shaker attrition strength.
2. Crush Strength Test
This test consists of placing a single agglomerate on an anvil
on a load measuring device and increasing the loading force on a
plate arranged to rest on top of the agglomerate until it is crushed.
The crush strength value (pounds) is an average for at least 15
activated agglomerates.
3. Refrigerant Compatibility
This test is designed to determine the tnedency of a molecular
sieve desiccant to chemically decompose halogenated refrigerants
to decomposition products such as hydrogen fluoride and hydrogen
chloride. The procedure is as follows:
Approximately 125 g of beads, previously activated at about 350.degree.
C. for at least about 10 hours under vacuum, are loaded into a 300
cc. stainless steel bomb with approximately 80 g of refrigerant,
e.g., R-22 (chlorodifluoromethane) or R-134a (1112-tetrafluoroethane)
and approximately 8 g of a suitable refrigerant oil. Suniso 3GS,
a naphthenic oil, available from Witco Corporation, New York, N.Y.,
is suitable for use with R-22 and LB525 a polyalkelene glycol,
available from Union Carbide Corporation, Danbury, Conn., is suitable
for R-134a. The bomb is then sealed and maintained at about 180.degree.
F. for 14 days. The beads are thereafter removed from the bomb and
purged with nitrogen at about 300.degree. C. for about 2 hours.
Next, the beads are analyzed for fluoride content by any suitable
means, such as by pyrohydrolysis and measurement by ion-selective
electrode. The results are reported as weight percent fluoride.
Low fluoride values are indicative of a greater degree of compatibility.
4. H.sub. 2 O Adsorption Capacity
This test is performed using a standard McBain gravimetric apparatus.
The beads are initially purged with nitrogen at about 300.degree.
C. for about 2 hours prior to loading into the apparatus. A quantity
of beads, e.g., about 1 to 5 g, is loaded into the McBain apparatus
and heated to about 400.degree. C. to 450.degree. C. for about 2
hours under vacuum and thereafter cooled to room temperature. The
beads are thereafter exposed to water vapor at a partial pressure
of 4.6 torr at room temperature. The equilibrium water pick-up is
expressed in weight percent H.sub.2 O.
The following examples are provided for illustrative purposes and
are not intended to be limitations on the claims that follow.
EXAMPLE 1
Treatment of molecular sieve agglomerates: 150 pounds of 4A-XH5
8.times.12 beaded adsorbent obtained from UOP, Des Plaines, Ill.
were initially hydrated with about 20 pounds of water. The hydrated
beads were then soaked in approximately 350 pounds of a potassium
silicate solution consisting of about 2.4 weight percent potassium
oxide, 6.0 weight percent silicon dioxide, with the balance consisting
of water, at room temperature for about six hours. The beads were
thereafter removed from the solution, rinsed with about 2.5 gallons
of water per pound of beads, and dried by heating in air to a temperature
of about 650.degree. C., maintaining said temperature for about
0.5 hours and thereafter cooling to room temperature.
EXAMPLE 2
Treatment of molecular sieve agglomerates with binder conversion:
450 g of 4A-XH5 8.times.12 beaded adsorbent obtained from UOP,
Des Plaines, Ill. were initially hydrated with about 60 g of water.
The hydrated beads were then contacted in approximately 1890 g of
a solution consisting of about 6 weight percent sodium hydroxide
with the balance consisting of water for about 4 hours at about
93.degree. C. with mild stirring. The beads were thereafter removed
from the sodium hydroxide solution and washed with water until the
beads had a pH of about 10. The washed beads were dried in ambient
air overnight then processed in accordance with Example 1 beginning
with the potassium silicate solution soaking. |