United States Patent [19]
`Breck, deceased et al.
`
`[11] Patent Number:
`[45) Date of Patent:
`
`4,503,023
`Mar. 5, 1985
`
`[75]
`
`[54] SILICON SUBSTITUTED ZEOLITE
`COMPOSffiONS AND PROCESS FOR
`PREPARING SAME
`Inventors: Donald W. Breck, deceased, late of
`White Plains, N.Y.; by Harold Blass,
`executor, Scarsdale; Gary W. Skeels,
`Brewster, both of N.Y.
`[73] Assignee: Union Carbide Corporation,
`Danbury, Conn.
`[21] Appl. No.: 315,853
`[22] Filed:
`Oct. 28, 1981
`
`[63]
`
`Related U.S. Application Data
`Continuation-in-part of Ser. No. 066,330, Aug. 14,
`1979, abandoned.
`Int. Cl.3 .............................................. C01B 33/28
`[51]
`[52] u.s. Cl ....................................... 423/328; 502/60;
`502/85; 502/86
`[58] Field of Search ................................ 423/328-330;
`252/441, 442,455Z; 502/60,78,79,85,86
`References Cited
`U.S. PATENT DOCUMENTS
`3,130,007 4/1964 Breck .................................. 423/328
`3,216,789 11/1965 Breck et al. ......................... 423/328
`3,436,174 4/1969 Sand .................................... 423/328
`
`[56]
`
`3,506,400 4/1970 Eberly et al ..........•............. 423/328
`3,594,331 7/1971 Elliott ................................. 252/442
`3,640,681 2/1972 Pickert ................................ 423/328
`3,702,886 11/1972 Argauer et al. ..................... 423/328
`3,929,672 12/1975 Ward ................................... 423/328
`3,933,983 1/1976 Elliott ................................. 423/328
`4,093,560 6/1978 Kerr ................................ 252/455 Z
`
`FOREIGN PATENT DOCUMENTS
`1431944 4/1976 United Kingdom .
`
`OTHER PUBLICATIONS
`Breck "Zeolite Molecular Sieves" Copyright, 1974, pp.
`507-518.
`Primary Examiner-Edward J. Meros
`Attorney, Agent, or Firm-Richard G. Miller
`[57]
`ABSTRACT
`Aluminum from AI04-tetrahedra of as-synthesized zeo(cid:173)
`lites is extracted and substituted with silicon to form
`zeolite compositions having higher SiO;V Al203 molar
`ratios and exhibiting distinctive chemical and physical
`properties. The preparative procedure involves contact
`of the starting zeolite with an aqueous solution of a
`fluorosilicate salt using controlled proportions and tem(cid:173)
`perature and pH conditions which avoid aluminum
`extraction without silicon substitution.
`
`20 Claims, 3 Drawing Figures
`
`Umicore AG & Co. KG
`Exhibit 1103
`Page 1 of 31
`
`

`

`~
`.......
`~
`nl
`t:r'
`til
`
`~
`
`Ul
`00
`1..0
`"' .......
`Ul
`~
`~
`
`f""t-
`t:S
`ft
`~·
`~
`•
`til
`
`c •
`
`U.S. Patent Mar. 5, 1985
`
`Sheet} of3
`
`4,503,023
`
`«.0
`
`80'.
`
`U)
`C:
`Lu
`(n
`
`2D2L
`
`u
`
`1800
`
`0:
`8;
`-
`
`O
`0g
`
`.....
`0::
`<(
`:z
`U)
`:::E
`.....
`~
`:z
`u
`w
`
`0O9
`
`"
`
`Ia
`
`FIG.
`
`O
`
`_
`u.
`
`8
`
`o
`co
`
`8
`
`O
`v
`
`O
`N
`
`BONVLLIWSNVEJ.
`
`Umicore AG & Co. KG
`Exhibit 1103
`Page 2 of 31
`
`

`

`US. Patent Mar. 5, 1985
`
`Sheet20f3
`
`4,503,023
`
`1.0
`
`6..
`
`8..
`
`E32 E
`
`é;
`
`FIG. lb
`
`.0
`
`FIG.
`
`
`
`8‘Q U)
`(I
`LU
`a:
`
`OO2
`
`I600
`
`IBOO
`
`EDNVLLIWSNVHTL
`
`Umicore AG & Co. KG
`Exhibit 1103
`Page 3 of 31
`
`

`

`U.S. Patent Mar. 5, 1985
`
`Sheet 3 of3
`
`.4,503,023
`
`FIG. 2
`
`1.10
`
`1.00
`
`.90
`
`.80
`
`t w u
`z
`<! m
`0:: S5
`
`~ .70
`
`.60
`
`.5
`
`3900
`
`3700
`
`3500
`WAVE NUMBERS
`
`3300
`
`Umicore AG & Co. KG
`Exhibit 1103
`Page 4 of 31
`
`

`

`1
`
`SILICON SUBSTITUTED ZEOLITE
`COMPOSITIONS AND PROCESS FOR
`PREPARING SAME
`
`4,503,023
`
`2
`or derived from dehydroxylation of the zeolite itself, is
`effective in removing framework aluminum by hydroly(cid:173)
`sis. Evidence of this phenomenon is set forth in U.S.
`Pat. No. 3,506,400, issued Apr. 14, 1970 toP. E. Eberly,
`5 Jr. et al.; U.S. Pat. No. 3,493,519, issued Feb. 3, 1970 to
`G. T. Kerr et al.; and U.S. Pat. No. 3,513,108, issued
`May 19, 1970 to G. T. Kerr. In those instances in which
`the crystal structure of the product composition is re-
`tained after the rigorous hydrothermal treatment in(cid:173)
`volved, infrared analysis indicated the presence of sub(cid:173)
`stantial hydroxyl groups exhibiting a stretching fre-
`quency in the area of about 3740, 3640 and 3550 em -1.
`The infrared analytical data of U.S. Pat. No. 3,506,400 is
`especially instructive in this regard. An explanation of
`the mechanism of the creation of these hydroxyl groups
`is provided by Kerr et al. in U.S. Pat. No. 3,493,519
`wherein the patentees state that the aluminum atoms in
`the lattice framework of hydrogen zeolites can react
`with water resulting in the removal of aluminum from
`the lattice in accordance with the following equation:
`
`RELATED APPLICATIONS
`This is a continuation-in-part of application Ser. No.
`066,330 filed Aug. 14, 1979, now abandoned.
`The present invention relates in general to novel
`zeolite compositions and to the method for their prepa- 10
`ration. More particularly it relates to zeolite composi(cid:173)
`tions topologically related to prior known zeolites but
`which have substantially greater SiO:V Ah03 molar
`ratios than the heretofore known zeolite species and
`characterized by containing framework silicon atoms 15
`from an extraneous source, and preferably a very low
`content of defect sites in the structure. In general the
`preparative process involves contacting the starting
`zeolite under controlled conditions with an aqueous
`solution of a fluorosilicate salt, preferably one which 20
`does not form insoluble salts with aluminum.
`The crystal structures of naturally occurring and
`as-synthesized zeolitic aluminosilicates are composed of
`Al04- and Si04 tetrahedra which are cross-linked by
`the sharing of oxygen atoms. The electrovalence of 25
`each tetrahedron containing an aluminum atom is bal(cid:173)
`anced by association with a cation. Most commonly this
`cation is a metal cation such as Na + or K + but organic
`species such as quaternary ammonium ions are also
`employed in zeolite synthesis and in some instances 30
`appear as cations in the synthesized product zeolite. In
`general the metal cations are, to a considerable extent at
`least, replaceable with other cations including H + and
`NH4 +. In many instances the organic cation species are
`too large to pass through the pore system of the zeolite 35
`and hence cannot be directly replaced by ion exchange
`techniques. Thermal treatments can reduce these or(cid:173)
`ganic cations to H + or NH4 + cations which can be
`directly ion-exchanged. Thermal treatment of the H +
`or NH4 + cationic forms of the zeolites can result in the 40
`substantial removal of these cations from their normal
`association with the AI04- tetrahedra thereby creating
`an electrovalent imbalance in the zeolite structure
`which must be accompanied by structural rearrange(cid:173)
`ments to restore the electrovalent balance. Commonly 45
`when the AI04- tetrahedra constitute about 40% or
`more of the total framework tetrahedra, the necessary
`structural rearrangements cannot be accommodated
`and the crystal structure collapses. In more siliceous
`zeolites, the structural integrity is substantially main- 50
`tained but the resulting "decationized" form has certain
`significantly different properties from its fully cation(cid:173)
`ized precursor.
`The relative instability of aluminum in zeolites, par(cid:173)
`ticularly in the non-metallic cationic or the decationized 55
`form, is well recognized in the art. For example, in U.S.
`Pat. No. 3,640,681, issued to P. E. Pickert on Feb. 3,
`1972, there is disclosed a process for extracting frame(cid:173)
`work aluminum from zeolites which involves dehy(cid:173)
`droxylating a partially cation deficient form of the zeo- 60
`lite and then contacting it with acetylacetone or a metal
`derivative thereof to chelate and solubilize aluminum
`atoms. Ethylenediaminetetraacetic acid has been pro(cid:173)
`posed as an extractant for aluminum from a zeolite
`framework in a process which is in some respects simi- 65
`lar to the Pickert process. It is also known that calcining
`the H + or NH4 + cation forms of zeolites such as zeolite
`Y is an environment of water vapor, either extraneous
`
`0
`0
`0
`I
`I
`I H
`-Si-0-AI-O-Si-0 + 3H20 ---::>~
`I
`I
`I
`0
`0
`0
`
`0
`0
`0
`I
`I
`H
`-Si-OH HO-Si-0 + AI(OH)J
`I
`I
`H
`0
`0
`0
`
`The aluminum removed from its original lattice position
`is capable of further reaction with cationic hydrogen,
`according to Kerr et al. to yield aluminum-containing
`i.e. hydroxoa1uminum, cations by the equation:
`
`0
`0
`0
`I
`I
`I H
`-Si-0-AI-O-Si-0 + Al(OH)3 ----7AJ(OH)2 +
`I
`I
`I
`0
`0
`0
`
`0
`0
`0
`I
`I
`I
`-Si-0-AJ--Osi- + H20
`I
`I
`I
`0
`0
`0
`
`It has been suggested that stabilization ofNH4Y occurs
`through hydrolysis of sufficient framework aluminum
`to form stable clusters of these hydroxoaluminum cati(cid:173)
`ons within the sodalite cages, thereby holding the zeo(cid:173)
`lite structure together while the framework anneals
`itself through the migration of some of the framework
`silicon atoms.
`It is alleged in U.S. Pat. No. 3,594,331, issued July 20,
`1971 to C. H. Elliott, that fluoride ions in aqueous me(cid:173)
`dia, particularly under conditions in which the pH is
`less than about 7, are quite effective in extracting frame(cid:173)
`work aluminum from zeolite lattices, and in fact when
`the fluoride concentration exceeds about 15 grams ac(cid:173)
`tive fluoride per 10,000 grams of zeolite, destruction of
`the crystal lattice by the direct attack on the framework
`silicon as well as on the framework aluminum, can re(cid:173)
`sult. A fluoride treatment of this type using from 2 to 22
`grams of available fluoride per 10,000 grams of zeolite
`(anhydrous) in which the fluorine is provided by ammo(cid:173)
`nium fluorosilicate is also described therein. The treat(cid:173)
`ment is carried out for the purpose of improving the
`thermal stability of the zeolite. It is theorized by the
`
`Umicore AG & Co. KG
`Exhibit 1103
`Page 5 of 31
`
`

`

`4,503,023
`
`4
`
`3
`patentee that the fluoride in some manner becomes
`attached to the constructional alkali metal oxide,
`thereby reducing the fluxing action of the basic struc(cid:173)
`tural Na20 which would otherwise result in the col(cid:173)
`lapse of the crystal structure. Such treatment within the 5
`constraints of the patent disclosure has no effect on
`either the overall silicon content of the zeolite product
`or the silicon content of a unit cell of the zeolite.
`Since stability quite obviously is, in part at least, a
`function of the SiO:z/ Ah03 ratio of zeolites, it would IO
`appear to be advantageous to obtain zeolites having
`higher proportions of Si04 tetrahedra by direct synthe-
`sis techniques and thereby avoid the structural changes
`inherent in framework aluminum extraction. Despite
`considerable effort in this regard, however, only very 15
`modest success has been achieved, and this as applied to
`a few individual species only. For example, over the
`seventeen . year period since zeolite Y was first made
`known to the public as a species having an as-synthe(cid:173)
`sized SiO:z/ Ah03 molar ratio of 3 to 6, the highest Si- 20
`O:z/ Ah03 value alleged for an as-synthesized zeolite
`having theY structure to date is7.8 (Netherlands Pat.
`No. 7306078).
`We have now discovered, however, a method for
`removing framework aluminum from zeolites having 25
`SiO:z/ Ah03 molar ratios of about 3 or greater and sub(cid:173)
`stituting therefor silicon from a source extraneous to the
`starting zeolite. By this procedure it is possible to create
`more highly siliceous zeolite species which have the
`same crystal structure as would result by direct synthe- 30
`sis if such synthesis method were known. In general the
`process .comprises contacting a crystalline zeolite hav(cid:173)
`ing pore diameters of at least about 3 Angstroms and
`having a molar SiO:z/Ah03 ratio of at least 3, with a
`fluorosilicate salt, preferably in an amount of at least 35
`0.0075 moles per 100 grams of zeolite starting material,
`said fluorosilicate salt being in the form of an aqueous
`solution having a pH value in the range of 3 to about 7,
`preferably 5 to about 7, and brought into contact with
`the zeolite either incrementally or continuously at a 40
`slow rate whereby· framework aluminum atoms of the
`zeolite are removed and replaced by extraneous silicon
`atoms from the added fluorosilicate. It is desirable that
`the process is carried out such that at least 60, prefera(cid:173)
`bly at least 80, and most preferably at least 90, percent 45
`of the crystal structure of the starting zeolite is retained
`and the Defect Structure Factor is less than 0.08, and
`preferably less than 0.05 as defined hereinafter.
`The crystalline zeolite starting materials suitable for
`the practice of the present invention can be any of the 50
`well known naturally occurring or synthetically pro(cid:173)
`duced zeolite species which have pores large enough to
`permit the passage of water, fluorosilicate reagents and
`reaction products through their internal cavity system.
`These materials can be represented, in terms of molar 55
`ratios of oxides, as
`
`wherein "a" is the fraction of framework tetrahedral
`sites occupied by aluminum atoms and "b" is the frac(cid:173)
`tion of framework tetrahedral sites occupied by silicon
`atoms. The algebraic sum of all of the subscripts within
`the brackets is equal to 1. In the above example,
`a+b=l.
`For reasons more fully explained hereinafter, it is
`necessary that the starting zeolite be able to withstand
`the initial loss of framework aluminum atoms to at least
`a modest degree without collapse of the crystal struc(cid:173)
`ture unless the process is to be carried out at a very slow
`pace. In general the ability to withstand aluminum ex(cid:173)
`traction and maintain a high level of crystallinity is
`directly proportional to the initial Si02/ Ah03 molar
`ratio of the zeolite. Accordingly it is preferred that the
`value for "x" in the formula above be at least about 3,
`and more preferably at least about 3.5. Also it is pre(cid:173)
`ferred that at least about 50, and more preferably at least
`95%, of the Al04 tetrahedra of the naturally occurring
`or as-synthesized zeolite are present in the starting zeo(cid:173)
`lite. Most advantageously the starting zeolite contains
`as many as possible of its original Al04 tetrahedra, i.e.
`has not been subjected to any post-formation treatment
`which either extensively removes aluminum atoms from
`their original framework sites or converts them from
`the normal conditions of 4-fold coordination with oxy(cid:173)
`gen.
`The cation population of the starting zeolite is not a
`critical factor insofar as substitution of silicon for frame(cid:173)
`work aluminum is concerned, but since the substitution
`mechanism involves the in situ formation of salts of at
`least some of the zeolite cations, it is advantageous that
`these salts be water-soluble to a substantial degree to
`facilitate their removal from the silica-enriched zeolite
`product. It is found that ammonium cations form the
`most soluble salt in this regard and it is accordingly
`preferred that at least 50 percent, most preferably 85 or
`more percent, of the zeolite cations be ammonium cati(cid:173)
`ons. Sodium and potassium, two of the most common
`original cations in zeolites are found to form Na3AlF6
`and K3AlF6 respectively, both of which are only very
`sparingly soluble in either hot or cold water. When
`these compounds are formed as precipitates within the
`structural cavities of the zeolite they are quite difficult
`to remove by water washing. Their removal, moreover,
`is important if thermal stability of the zeolite product is
`desired since the substantial amounts of fluoride can
`cause crystal collapse at temperatures as low as 500• C.
`The naturally-occurring or synthetic zeolites used as
`starting materials in the present process are composi(cid:173)
`tions well-known in the art. A comprehensive review of
`the structure, properties and chemical compositions of
`crystalline zeolites is contained in Breck, D. W., "Zeo(cid:173)
`lite Molecular Sieves," Wiley, New York, 1974, and
`incorporated herein by reference. In those instances in
`which it is desirable to replace original zeolitic cations
`for others more preferred in the present process, con(cid:173)
`ventional ion-exchange techniques are suitably em(cid:173)
`ployed. Especially preferred zeolite species are zeolite
`Y, zeolite rho, zeolite W, zeolite N-A, zeolite L, and the
`mineral and synthetic analogs of mordenite clinoptilo(cid:173)
`lite, chabazite, offretite and erionite. The fluorosilicate
`salt used as the aluminum extractant and also as the
`source of extraneous silicon which is inserted into the
`zeolite structure in place of the extracted aluminum can
`be any of the fluorosilicate salts having the general
`formula
`
`wherein "M" is a cation having the valence "n", "x" is 60
`a value of at least about 3 and "y" has a value of from
`zero to about 9 depending upon the degree of hydration
`and the capacity of the particular zeolite to hold ad(cid:173)
`sorbed water. Alternatively, the framework composi~
`tion can be expressed as the mole fraction of framework 65
`tetrahedra, T02, as:
`
`Umicore AG & Co. KG
`Exhibit 1103
`Page 6 of 31
`
`

`

`5
`
`4,503,023
`
`wherein A is a metallic or non-metallic cation other
`than H+ having the valence "b". Cations represented 5
`by "A" are alkylammonium, NJ4+, Mg++, Li+, Na+,
`K+, Ba++, Cd++, Cu+, H+, Ca++, Cs+, Fe++,
`Co++, Pb++, Mn++, Rb+, Ag+, Sr++, TI+ and
`Zn + +. The ammonium cation form of the fluorosilicate
`is highly preferred because of its substantial solubility in 10
`water and also because the ammonium cations form
`water soluble by-product salts upon reaction with the
`zeolite, namely (NI4)3AlF6.
`In certain respects,
`the manner in which the
`fluorosilicate and starting zeolite are brought into 15
`contact and reacted is of critical importance. We have
`discovered that the overall process of substituting sili(cid:173)
`con for aluminum in the zeolite framework is a two step
`process in which the aluminum extraction step will,
`unless controlled, proceed very rapidly while the sili- 20
`con insertion is relatively very slow. If dealumination
`becomes too extensive without silicon substitution, the
`crystal structure becomes seriously degraded and ul(cid:173)
`timtely collapses. While we do not wish to be bound by
`any particular theory, it appears that the fluoride ion is 25
`the agent for the extraction of framework aluminum in
`accordance with the equation.
`·
`
`6
`structure. Practical commercial considerations, how(cid:173)
`ever, require that the reaction proceed as rapidly as
`possible, and accordingly the conditions of reaction
`temperature and reagent concentrations should be opti(cid:173)
`mized with respect to each zeolite starting material. In
`general the more highly siliceous the zeolite, the higher
`the permissible reaction temperature and the lower the
`suitable pH conditions. In general the preferred reac(cid:173)
`tion temperature is within the range of so· to 95° c., but
`temperatures as high as 125• C. and as low as 20• C.
`have been suitably employed in some instances. At pH
`values below about 3 crystal degradation is generally
`found to be unduly severe, whereas at pH values higher
`than 7, silicon insertion is unduly low. The maximum
`concentration of fluorosilicate salt in the aqueous solu(cid:173)
`tion employed is, of course, interdependent with the
`temperature and pH factors and also with the time of
`contact between the zeolite and the solution and the
`relative proportions of zeolite and fluorosilicate. Ac(cid:173)
`cordingly it is possible that solutions having fluorosili(cid:173)
`cate concentrations of from about J0-3 moles per liter
`of solution up to saturation can be employed, but it is
`preferred that concentrations in the range of 0.5 to 1.0
`moles per liter of solution be used. These concentration
`values are with respect to true solutions, and are not
`intended to apply to the total fluorosilicate in slurries of
`salts in water. As illustrated hereinafter, even very
`slightly soluble fluorosilicates can be slurried in water
`30 and used as a reagent-the undissolved solids being
`readily available to replace dissolved molecular species
`consumed in reaction with the zeolite. As stated herein(cid:173)
`above, the amount of dissolved fluorosilicate employed
`with respect to the particular zeolite being treated will
`35 depend to some extent upon the physical and chemical
`properties of the individual zeolites as well as other
`specifications herein contained in this application. How(cid:173)
`ever, the minimum value for the amount of fluorosili(cid:173)
`cate to be added should be at least equivalent to the
`40 minimum mole fraction of aluminum to. be removed
`from the zeolite.
`In this disclosure, including the appended claims, in
`specifying proportions of zeolite starting material or
`adsorption properties of the zeo1ite product, and the
`like, the anhydrous state of the zeolite will be intended
`unless otherwise stated. The anhydrous state is consid-
`ered to be that obtained by heating the zeolite in dry air
`at 4so· C. for 4 hours.
`It is apparent from the foregoing that, with respect to
`reaction conditions, it is desirable that the integrity of
`the zeolite crystal structure is substantially maintained
`throughout the process, and that in addition to having
`extraneous (non-zeolitic) silicon atoms inserted into the
`lattice, the zeolite retains at least 60 and preferably at
`least 90 percent of its original crystallinity. A conve(cid:173)
`nient technique for assessing the crystallinity of the
`products relative to the crystallinity of the starting rna- .
`terial is the comparison of the relative intensities of the
`d-spacings of their respective X-ray powder diffraction
`patterns. The sum of the peak heights, in terms of arbi(cid:173)
`trary units above background, of the starting material is
`used as the standard and is compared with the corre(cid:173)
`sponding peak heights of the products. When, for exam(cid:173)
`ple, the numerical sum of the peak heights of the prod(cid:173)
`uct is 85 percent of the value of the sum of the peak
`heights of the starting zeolite, then 85 percent of the
`crystallinity has been retained. In practice it is common
`to utilize only a portion of the d-spacing peaks for this
`
`NJ4+
`
`0
`0
`(Nf4)2SiF6 (soln) + /AI-'-. ~
`0
`0
`
`" /
`
`Zeolite
`
`+ (NJ4)3AlF6 (soln}
`
`0
`
`0
`
`0
`'-./
`Si
`/'-.
`0
`
`Zeolite
`
`It is, therefore, essential that the initial dealumination
`step be inhibited and the silicon insertion step be pro(cid:173)
`moted to achieve the desired zeolite product. It is found 45
`that the various zeolite species have varying degrees of
`resistance toward degradation as a consequence of
`framework aluminum extraction without silicon substi(cid:173)
`tution. In general the rate of aluminum extraction is
`decreased as the pH of the fluorosilicate solution in so
`contact with the zeolite is increased within the range of
`3 to 7, and as the concentration of the fluorosilicate in
`the reaction system is decreased. Also increasing the
`reaction temperature tends to increase the rate of silicon
`substitution. Whether it is necessary or desirable to ss
`buffer the reaction system or strictly limit the fluorosili(cid:173)
`cate concentration is readily determined for each zeolite
`species by routine observation.
`Theoretically, there is no lower limit for the concen(cid:173)
`tration of fluorosilicate salt in the aqueous solution em- 60
`ployed, provided of course the pH of the solution is
`high enough to avoid undue destructive acidic attack on
`the zeolite structure apart from the intended reaction
`with the fluorosilicate. Very slow rates of addition of
`fluorosilicate salts insure that adequate time is permitted 65
`for the insertion of silicon as a framework substitute for
`extracted aluminum before excessive aluminum extrac(cid:173)
`tion occurs with consequent collapse of the crystal
`
`Umicore AG & Co. KG
`Exhibit 1103
`Page 7 of 31
`
`

`

`4,503,023
`
`7
`purpose, as for example, five of the six strongest d-spac(cid:173)
`ings. In zeolite Y these.d-spacings correspond to the
`Miller Indices 331,-440, 533, 642 and 555. Other indicia
`of the crystallinity retained by the zeolite product are
`the degree of retention of surface area and the degree of 5
`retention of the adsorption capacity. Surface areas can
`be determined by the ·well-known Brunauer-Emmett(cid:173)
`Teller method (B-E-T). J. Am. Chern. Soc. 60 309
`(1938) using nitrogen as the adsorbate. In determining
`the adsorption capacity, the capacity for oxygen at 10
`- 183° C. at 100 Torr is preferred.
`All available evidence indicates that the present pro(cid:173)
`cess is unique in being able to produce zeolites essen(cid:173)
`tially free of defect structure yet having molar Si02.
`I Ah03 ratios higher than can be obtained by direct 15
`hydrothermal synthesis. The products resulting from
`the operation of the process share the common charac(cid:173)
`teristic of having a higher molar SiOv Ah03 ratio than
`previously obtained for each species by direct hydro(cid:173)
`thermal synthesis by virtue of containing silicon from an 20
`extraneous, i.e. non-zeolitic, source, preferably in con(cid:173)
`junction with a crystal structure which is characterized
`as containing a low level of tetrahedral defect sites. This
`defect structure, if present, is revealed by the infrared
`spectrum of zeolites in the hydroxyl-stretching region. 25
`In untreated, i.e. naturally occurring or as-synthe(cid:173)
`sized zeolites the original tetrahedral structure is con(cid:173)
`ventionally represented as
`
`I
`-Si-
`1
`0
`I
`I
`I
`-Si-0-Al-OSi-
`1
`I
`I
`0
`I
`-Si-
`1
`
`I
`-Si-
`1
`0
`I
`H
`-Si-OH
`I
`H
`0
`I
`-Si-
`1
`
`I
`HO-Si-
`1
`
`8
`groups of adsorbed water molecules are also hydrogen(cid:173)
`bonded and produce a similar broad absorption band as
`do the "nest" hydroxyls. Also, certain other zeolitic
`hydroxyl groups, exhibiting specific characteristic ab(cid:173)
`sorption frequencies within the range of interest, will if
`present, cause infrared absorption bands in these regions
`which are superimposed on the band attributable to the
`"nest" hydroxyl groups. These specific hydroxyls are
`created by the decomposition of ammonium cations or
`organic cations present in the zeolite.
`It is, however, possible to treat zeolites, prior to sub(cid:173)
`jecting them to infrared analysis, to avoid the presence
`of the interferring hydroxyl groups and thus be able to
`observe the absorption attributable to the "nest" hy(cid:173)
`droxyls only. The hydroxyls belonging to adsorbed
`water are avoided by subjecting the hydrated zeolite
`sample to vacuum activation at a moderate temperature
`of about 200° C. for about 1 hour. This treatment pet(cid:173)
`mits desorption and removal of the adsorbed water.
`Complete removal of adsorbed water can be ascertained
`by noting when the infrared absorption band at about
`1640 cm-1, the bending frequency of water molecules,
`has been removed from the spectrum.
`The decomposable ammonium cations can be ·re-
`moved, at least in large part, by ion-exchange and re(cid:173)
`placed with metal cations, preferably by subjecting the
`ammonium form of the zeolite to a mild ion exchange
`treatment with an aqueous NaCl solution. The OH
`30 absorption bands produced by the thermal decomposi(cid:173)
`tion of ammonium cations are thereby avoided. Accord(cid:173)
`ingly the absorption band over the range of 3745 em -1
`to about 3000 em- I for a zeolite so treated is almost
`entirely attributable to hydroxyl groups associated with
`35 defect structure and the ·absolute absorbance of this
`band can be a measure of the degree of aluminum deple(cid:173)
`tion.
`It is found, however, that the ion-exchange treat(cid:173)
`ment, which must necessarily be exhaustive even
`though mild, requires considerable time. Also the com(cid:173)
`bination of the ion-exchange and the vacuum calcina(cid:173)
`tion to remove adsorbed water does not remove every
`possible hydroxyl other than defect hydroxyls which
`can exhibit absorption in the 3745 cm-1 to 3000 cm- 1
`range. For instance, a rather sharp band at 3745 em- 1
`has been attributed to the Si-OH groups situated in the
`terminal lattice positions of the zeolite crystals and to
`amorphous (non-zeolitic) silica from which physically
`adsorbed water has been removed. For these reasons
`50 we prefer to use a somewhat different criterion to mea(cid:173)
`sure the degree of defect structure in the zeolite prod(cid:173)
`ucts of this invention.
`In the absence of hydrogen-bonded hydroxyl groups
`contributed by physically absorbed water, the absorp-
`55 tion frequency least affected by absorption due to hy(cid:173)
`droxyl groups other than those associated with frame(cid:173)
`work vacancies or defect sites is at 3710±5 cm-1. Thus
`the relative number of defect sites remaining in a zeolite
`product of this invention can be gauged by first remov(cid:173)
`ing any adsorbed water from the zeolite, determining
`the value of the absolute absorbance in its infrared spec-
`trum at a frequency of 3710 cm-1, and comparing that
`value with the corresponding value obtained from the
`spectrum of a zeolite having a known quantity of defect
`structure. The following specific procedure has been
`arbitrarily selected and used to measure the amount of
`defect structure in the products prepared in the Exam(cid:173)
`ples appearing hereinafter. Using the data obtained
`
`After treatment with a complexing agent such as ethyl- 40
`enediaminetetraacetic acid (H4EDT A) in which a stoi(cid:173)
`chiometric reaction occurs whereby framework alumi(cid:173)
`num atoms along with an associated cation such as
`sodium is removed as NaAIEDTA, it is postulated that
`the tetrahedral aluminum is replaced by four protons 45
`which form a hydroxyl "nest", as follows:
`
`The infrared spectrum of the aluminum depleted zeolite
`will show a broad nondescript absorption band begin- 60
`ning at about 3750 cm-1 and extending to about 3000
`cm-1. The size of this absorption band or envelope
`increases with increasing aluminum depletion of the
`zeolite. The reason that the absorption band is so broad
`and without any specific absorption frequency is that 65
`the hydroxyl groups in the vacant sites in the frame(cid:173)
`work are coordinated in such a way that they interact
`with each ·other (hydrogen bonding). The hydroxyl
`
`Umicore AG & Co. KG
`Exhibit 1103
`Page 8 of 31
`
`

`

`4,503,023
`
`9
`from this procedure it is possible, using simple mathe(cid:173)
`matical calculation, to obtain a single and reproducible
`value hereinafter referred to as the "Defect Structure
`Factor", denoted hereinafter by the symbol "z", which
`can be used in comparing and distinguishing the present
`novel zeolite compositions from their less-siliceous
`prior known counterparts and also with equally sili(cid:173)
`ceous prior known counterparts prepared by other
`techniques.
`
`10
`Once the defect structure factor, z, is known, it is
`possible to determine from wet chemical analysis of the
`product sample for Si02, Ah03 and the cation content
`as M21nO whether silicon has been substituted for alu-
`5 minum in the zeolite as a result of the treatment and also
`the efficiency of any such silicon substitution.
`For purposes of simplifying these determinations, the
`framework compositions are best expressed in terms of
`mole fractions of framework tetrahedra T02. The start-
`10 ing zeolite may be expressed as:
`
`whereas "a" is the mole fraction of aluminum tetrahedra
`in the framework; "b" is the mole fraction of silicon
`tetrahedra in the framework; 0 denotes defect sites and
`"z" is the mole fraction of defect sites in the zeolite
`framework. In many cases the "z" value for the starting
`zeolite is zero and the defect sites are simply eliminated
`from the expression. Numerically the sum of the values
`a+b+z=l.
`The zeolite product of the fluorosilicate treatment,
`expressed in terms of mole fraction of framework tetra(cid:173)
`hedra (T02) will have the form
`
`wherein: "N" is defined as the mole fraction of alumi(cid:173)
`num tetrahedra removed from the framework during
`the treatment; "a" is the mole fraction of aluminum
`tetrahedra present in the framework of the starting
`zeolite; "b" is the mole fraction of silicon tetrahedra
`present in the framework of the starting zeolite; "z" is
`the mole fraction of defect sites in the framework;
`(N- ~z) is the mole fraction increase in silicon tetrahe(cid:173)
`dra resulting from the fluorosilicate treatment; "h.z" is
`the net change in the mole .fraction of defect sites in the
`zeolite framework resulting from the treatment
`~z=z (product zeolite)-z(starting zeolite) The term
`Defect Structure Factor for any given zeolite is equiva(cid:173)
`lent to the "z" value of the zeolite. The net change in
`Defect Stru