Zeolite SSZ-15 and process for preparing the same

TECHNICAL FIELD 
Natural and synthetic aluminosilicates are important and useful 
compositions. Many of these aluminosilicates are porous and have definite, 
distinct crystal structures as determined by X-ray diffraction. Within the 
crystals are a large number of cavities and pores whose dimensions and 
shapes vary from zeolite to zeolite. Variations in pore dimensions and 
shapes cause variations in the adsorptive and catalytic properties of the 
zeolites. Only molecules of certain dimensions and shapes are able to fit 
into the pores of a particular zeolite while other molecules of larger 
dimensions or different shapes are unable to penetrate the zeolite 
crystals. 
Because of their unique molecular sieving characteristics, as well as their 
potentially acidic nature, zeolites are especially useful in hydrocarbon 
processing as adsorbents, and, as catalysts, for cracking, reforming, and 
other hydrocarbon conversion reactions. Although many different 
crystalline aluminosilicates have been prepared and tested, the search 
continues for new zeolites which can be used in hydrocarbon and chemical 
processing. 
I have discovered a novel family of crystalline aluminosilicate zeolites, 
hereafter called "Zeolite SSZ-15" or simply "SSZ-15", and methods for its 
preparation and use. 
In recent years, many crystalline aluminosilicates having desirable 
adsorption and catalytic properties have been prepared. Typically, 
zeolites are prepared from reaction mixtures having sources of alkali or 
alkaline earth metal oxides, silica, and alumina. More recently, 
"nitrogenous zeolites" have been prepared from reaction mixtures 
containing an organic species, usually a nitrogen compound. Depending upon 
the reaction conditions and the composition of the reaction mixture, 
different zeolites can be formed even if the same organic species are 
used. For example, zeolites ZK-4, ZSM-4, faujasite and PHI, have all been 
prepared from tetramethylammonium solutions. 
Although most experiments reported as producing nitrogenous zeolites have 
used fairly simple organic species such as tetra(n-alkyl)ammonium cations 
or alkylenediamines, several experiments are reported as using other 
organic species. U.S. Pat. No. 3,692,470, Ciric, Sept. 19, 1972, discloses 
preparing ZSM-10 from 1,4-dimethyl-1,4-diazoniabicyclo[2.2.2.]octane. U.S. 
Pat. No. 3,783,124, Rubin et al., Jan. 1, 1974 discloses preparing a 
zeolite from benzyl trimethylammonium compounds. U.S. Pat. No. 3,832,449, 
Rosinski et al., Aug. 27, 1974, discloses preparing ZSM-12 from the 
reaction products of alkylene dihalides with complex amines or nitrogen 
heterocycles. U.S. Pat. No. 3,950,496, Ciric, Apr. 13, 1976, discloses 
preparing ZSM-18 from "tris" ammonium hydroxide 
(1,3,4,6,7,9-hexahydro-2,2,5,5,8,8-hexamethyl-2H-benzo[1,2-C:3,4-C':5,6-C" 
]tripyrolium trihydroxide). U.S. Pat. No. 4,000,248, Martin, Dec. 28, 1976 
discloses preparing ferrierite using N-methylpyridine. U.S. Pat. No. 
4,018,870, Whittam, Apr. 19, 1977, discloses preparing AG5 and AG6 using 
nitrogenous basic dyes. U.S. Pat No. 4,251,499, Nanne, Feb. 17, 1981 
discloses preparing ferrierite using piperidine or alkyl substituted 
piperidine. And, U.S. Pat. No. 4,285,922, Audeh, Aug. 25, 1981, discloses 
preparing ZSM-5 using 1-alkyl, 4 aza, 1-azonia-bicyclo[2.2.2]octane, 
4-oxide halides. 
TECHNICAL DISCLOSURE 
My invention is a zeolite having a mole ratio of an oxide selected from 
silicon oxide, germanium oxide, and mixtures thereof to an oxide selected 
from aluminum oxide, gallium oxide, and mixtures thereof greater than 
about 5:1 and having the X-ray diffraction lines of Table 1. The zeolite 
further has a composition, as synthesized and in the anhydrous state, in 
terms of mole ratios of oxides, as follows: (0.5 to 1.4)R.sub.2 O:(0 to 
0.50)M.sub.2 O:W.sub.2 O.sub.3 :(greater than 5)YO.sub.2 wherein M is an 
alkali metal cation, W is selected from aluminum, gallium, and mixtures 
thereof, Y is selected from silicon, germanium and mixtures thereof, and R 
is an organic cation. 
SSZ-15 zeolites can have a YO.sub.2 :W.sub.2 O.sub.3 mole ratio greater 
than about 5:1. As prepared, the silica:alumina mole ratio is typically 
above about 50:1. Since aluminum need not be used in the reaction mixture, 
the zeolite can be prepared in essentially aluminum free form as silica 
polymorphs having silica:alumina mole ratios greater than 1000:1. The 
silica:alumina mole ratio of the SSZ-15 zeolites can be increased by using 
standard acid leaching or chelating treatments and by using silicon and 
carbon halides and similar compounds. Preferably, for catalytic use, 
SSZ-15 is an aluminosilicate wherein W is aluminum and Y is silicon. 
My invention also involves a method for preparing SSZ-15 zeolites, 
comprising preparing an aqueous mixture containing sources of an organic 
nitrogen-containing compound, an oxide selected from aluminum oxide, 
gallium oxide, and mixtures thereof, and an oxide selected from silicon 
oxide, germanium oxide, and mixtures thereof, and having a composition, in 
terms of mole ratios of oxides, falling within the following ranges: 
W.sub.2 O.sub.3 /YO.sub.2, 1:5 to 0:1; R.sub.2 O/W.sub.2 O.sub.3 0.5:1 to 
40:1; and OH.sup.- /SiO.sub.2 less than about 0.95:1; wherein Y is 
selected from silicon, germanium, and mixtures thereof, W is selected from 
aluminum, gallium and mixtures thereof, and R is an organic cation; 
maintaining the mixture at a temperature of at least 100.degree. C. until 
the crystals of said zeolite are formed; and recovering said crystals. 
SSZ-15 zeolites have a crystalline structure whose X-ray powder diffraction 
pattern shows the following characteristic lines: 
TABLE 1 
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Relative 
2 .phi. d/n Intensity 
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7.96 11.10 15 
9.59 9.22 31 
19.17 4.63 59 
19.86 4.47 22 
20.61 4.31 100 
22.28 3.99 39 
23.60 3.77 11 
24.05 3.70 17 
24.84 3.59 20 
25.98 3.43 6 
26.61 3.35 20 
27.27 3.27 28 
29.78 3.00 6 
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Typical SSZ-15 aluminosilicate zeolites as synthesized have the X-ray 
diffraction patterns of Tables 4-7. 
The X-ray powder diffraction patterns were determined by standard 
techniques. The radiation was the K-alpha/doublet of copper and a 
scintillation counter spectrometer with a strip-chart pen recorder was 
used. The peak heights I and the positions, as a function of 2 .theta. 
where .theta. is the Bragg angle, were read from the spectrometer chart. 
From these measured values, the relative intensities, 100I/I.sub.0, where 
I.sub.0 is the intensity of the strongest line or peak, and d, the 
interplanar spacing in Angstroms corresponding to the recorded lines, can 
be calculated. The X-ray diffraction pattern of Table 1 is characteristic 
of SSZ-15 zeolites. The zeolite as synthesized or as produced by 
exchanging the metal or other cations present in the zeolite with various 
other cations yields substantially the same diffraction pattern although 
there can be minor shifts in interplanar spacing and minor variations in 
relative intensity. Minor variations in the diffraction pattern can also 
result from varying the organic compound used in the preparation and from 
variations in the silica-to-alumina mole ratio from sample to sample. 
Calcination can also cause minor shifts in the X-ray diffraction pattern. 
Notwithstanding these minor perturbations, the basic crystal lattice 
structure remains unchanged. 
SSZ-15 zeolites can be suitably prepared from an aqueous solution 
containing sources of an alkali metal oxide, an organic compound, an oxide 
of aluminum or gallium, or mixture of the two, and an oxide of silicon or 
germanium, or mixture of the two. The reaction mixture should have a 
composition in terms of mole ratios of oxides falling within the following 
ranges: 
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Broad Preferred 
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W.sub.2 O.sub.3 /YO.sub.2 
0-0.2 0.0005-0.02 
M.sub.2 O/W.sub.2 O.sub.3 
0.5-20 1-17 
R.sub.2 O/W.sub.2 O.sub.3 
0.5-40 5-25 
OH.sup.- /YO.sub.2 
&lt;0.95 &lt;0.40 
______________________________________ 
wherein R is as disclosed below, Y is silicon, germanium or both, and W is 
aluminum, gallium or both. M is an alkali metal, preferably sodium. 
Typically, an alkali metal hydroxide is used in the reaction mixture; 
however, this component can be omitted so long as the equivalent basicity 
is maintained. The organic compound can provide hydroxide ion. 
"Essentially alumina free", as used herein, is meant the product, a silica 
polymorph having the SSZ-15 lattice structure (or essentially alumina-free 
silicaceous crystalline molecular sieve), has a silica:alumina mole ratio 
of greater than 200:1, preferably greater than 500:1, and more preferably 
greater than 1000:1. The term "essentially alumina free" is used because 
it is difficult to prepare completely aluminum free reaction mixtures for 
synthesizing these materials. Especially when commercial silica sources 
are used, aluminum is almost always present to a greater or lesser degree. 
The hydrothermal reaction mixtures from which the essentially alumina free 
crystalline silicaceous molecular sieves are prepared can also be referred 
to as being substantially aluminum free. By this usage is meant that no 
aluminum is intentionally added to the reaction mixture, e.g., as an 
alumina or aluminate reagent, and that to the extent aluminum is present, 
it occurs only as a contaminant in the reagents. 
The organic component of the crystallization mixture is typically a 
cycloalkyl trimethyl heteroatom compound. The heteroatom can be nitrogen 
or phosphorus. The preferred organic species are sources of cyclohexyl 
trimethylammonium cations and cyclopentyl trimethylammonium cations. The 
cyclopentyl trimethylammonium cation sources are especially preferred. 
The reaction mixture is prepared using standard zeolitic preparation 
techniques. Typical sources of aluminum oxide for the reaction mixture 
include aluminates, alumina, and aluminum compounds such as AlCl.sub.3 and 
Al.sub.2 (SO.sub.4).sub.3. Typical sources of silicon oxide include 
silicates, silica hydrogel, silicic acid, colloidal silica, tetraalkyl 
orthosilicates, and silica hydroxides. Gallium and germanium can be added 
in forms corresponding to their aluminum and silicon counterparts. Salts, 
particularly alkali metal halides such as sodium chloride, can be added to 
or formed in the reaction mixture. They are disclosed in the literature as 
aiding the crystallization of zeolites while preventing silica occlusion 
in the lattice. 
The reaction mixture is maintained at an elevated temperature until the 
crystals of the zeolite are formed. The temperatures during the 
hydrothermal crystallization step are typically maintained from about 
100.degree. C. to about 235.degree. C., preferably from about 120.degree. 
C. to about 200.degree. C. and most preferably from about 135.degree. C. 
to about 165.degree. C. The crystallization period is typically greater 
than 1 day and preferably from about 3 days to about 50 days. 
The hydrothermal crystallization is usually conducted under pressure and 
usually in an autoclave so that the reaction mixture is subject to 
autogenous pressure. The reaction mixture can be stirred during 
crystallization. 
Once the zeolite crystals have formed, the solid product is separated from 
the reaction mixture by standard mechanical separation techniques such as 
filtration. The crystals are water-washed and then dried, e.g., at 
90.degree. C. to 150.degree. C. for from 8 to 24 hours, to obtain the as 
synthesized, SSZ-15 zeolite crystals. The drying step can be performed at 
atmospheric or subatmospheric pressures. 
During the hydrothermal crystallization step, the SSZ-15 crystals can be 
allowed to nucleate spontaneously from the reaction mixture. The reaction 
mixture can also be seeded with SSZ-15 crystals both to direct, and 
accelerate the crystallization, as well as to minimize the formation of 
undesired aluminosilicate contaminants. If the reaction mixture is seeded 
with SSZ-15 crystals, the concentration of the organic compound can be 
greatly reduced or eliminated, but it is preferred to have some organic 
compound present, e.g., an alcohol. 
The synthetic SSZ-15 zeolites can be used as synthesized or can be 
thermally treated (calcined). Usually, it is desirable to remove the 
alkali metal cation by ion exchange and replace it with hydrogen, 
ammonium, or any desired metal ion. The zeolite can be leached with 
chelating agents, e.g., EDTA or dilute acid solutions, to increase the 
silica:alumina mole ratio. The zeolite can also be steamed; steaming helps 
stabilize the crystalline lattice to attack from acids. The zeolite can be 
used in intimate combination with hydrogenating components, such as 
tungsten, vanadium, molybdenum, rhenium, nickel, cobalt, chromium, 
manganese, or a noble metal, such as palladium or platinum, for those 
applications in which a hydrogenation-dehydrogenation function is desired. 
Typical replacing cations can include metal cations, e.g., rare earth, 
Group IIA and Group VIII metals, as well as their mixtures. Of the 
replacing metallic cations, cations of metals such as rare earth, Mn, Ca, 
Mg, Zn, Cd, Pt, Pd, Ni, Co, Ti, Al, Sn, Fe and Co are particularly 
preferred. 
The hydrogen, ammonium, and metal components can be exchanged into the 
zeolite. The zeolite can also be impregnated with the metals, or, the 
metals can be physically intimately admixed with the zeolite using 
standard methods known to the art. And, the metals can be occluded in the 
crystal lattice by having the desired metals present as ions in the 
reaction mixture from which the SSZ-15 zeolite is prepared. 
Typical ion exchange techniques involve contacting the synthetic zeolite 
with a solution containing a salt of the desired replacing cation or 
cations. Although a wide variety of salts can be employed, chlorides and 
other halides, nitrates, and sulfates are particularly preferred. 
Representative ion exchange techniques are disclosed in a wide variety of 
patents including U.S. Pat. Nos. 3,140,249; 3,140,251; and 3,140,253. Ion 
exchange can take place either before or after the zeolite is calcined. 
Following contact with the salt solution of the desired replacing cation, 
the zeolite is typically washed with water and dried at temperatures 
ranging from 65.degree. C. to about 315.degree. C. After washing, the 
zeolite can be calcined in air or inert gas at temperatures ranging from 
about 200.degree. C. to 820.degree. C. for periods of time ranging from 1 
to 48 hours, or more, to produce a catalytically active product especially 
useful in hydrocarbon conversion processes. 
Regardless of the cations present in the synthesized form of the zeolite, 
the spatial arrangement of the atoms which form the basic crystal lattice 
of the zeolite remains essentially unchanged. The exchange of cations has 
little, if any, effect on the zeolite lattice structures. 
The SSZ-15 aluminosilicate can be formed into a wide variety of physical 
shapes. Generally speaking, the zeolite can be in the form of a powder, a 
granule, or a molded product, such as extrudate having particle size 
sufficient to pass through a 2-mesh (Tyler) screen and be retained on a 
400-mesh (Tyler) screen. In cases where the catalyst is molded, such as by 
extrusion with an organic binder, the aluminosilicate can be extruded 
before drying, or, dried or partially dried and then extruded. 
The zeolite can be composited with other materials resistant to the 
temperatures and other conditions employed in organic conversion 
processes. Such matrix materials include active and inactive materials and 
synthetic or naturally occurring zeolites as well as inorganic materials 
such as clays, silica and metal oxides. The latter may be naturally 
occurring or may be in the form of gelatinous precipitates sols, or gels, 
including mixtures of silica and metal oxides. Use of an active material 
in conjunction with the synthetic zeolite, combined with it, can improve 
the conversion and selectivity of the catalyst in certain organic 
conversion processes. Inactive materials can serve as diluents to control 
the amount of conversion in a given process so that products can be 
obtained economically without using other means for controlling the rate 
of reaction. Frequently, zeolite materials have been incorporated into 
naturally occurring clays, e.g., bentonite and kaolin. These materials, 
i.e., clays, oxides, etc., function, in part, as binders for the catalyst. 
It is desirable to provide a catalyst having good crush strength and 
attrition resistance, because in petroleum refining the catalyst is often 
subjected to rough handling. This tends to break the catalyst down into 
powders which cause problems in processing. 
Naturally occurring clays which can be composited with the synthetic 
zeolites of this invention include the montmorillonite and kaolin 
families, which families include the sub-bentonites and the kaolins 
commonly known as Dixie, McNamee, Georgia and Florida clays or others in 
which the main mineral constituent is halloysite, kaolinite, dickite, 
nacrite, or anauxite. Fibrous clays such as sepiolite and attapulgite can 
also be used as supports. Such clays can be used in the raw state as 
originally mined or can be calcined, treated with acid, or chemically 
modified. 
In addition to the foregoing materials, the SSZ-15 zeolites can be 
composited with porous matrix materials and mixtures of matrix materials 
such as silica, alumina, titania, magnesia, silica-alumina, 
silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia, 
silica-titania, titania-zirconia as well as ternary compositions such as 
silica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesia 
and silica-magnesia-zirconia. The matrix can be in the form of a cogel. 
The SSZ-15 zeolites can also be composited with other zeolites such as 
synthetic and natural faujasites (e.g., X and Y), erionites, and 
mordenites. They can also be composited with purely synthetic zeolites 
such as ZSM-5. The combination of zeolites can also be composited in a 
porous inorganic matrix. 
SSZ-15 zeolites are useful in hydrocarbon conversion reactions. Hydrocarbon 
conversion reactions are chemical and catalytic processes in which carbon 
containing compounds are changed to different carbon containing compounds. 
Examples of hydrocarbon conversion reactions include catalytic cracking, 
hydrocracking, and olefin and aromatics formation reactions. The catalysts 
are useful in other petroleum refining and hydrocarbon conversion 
reactions such as isomerizing n-paraffins and naphthenes, polymerizing and 
oligomerizing olefinic or acetylenic compounds such as isobutylene and 
butene-1, reforming, alkylating, isomerizing polyalkyl substituted 
aromatics (e.g., ortho xylene), and disproportionating aromatics (e.g., 
toluene) to provide mixtures of benzene, xylenes and higher 
methylbenzenes. The SSZ-15 catalysts have high selectivity, and under 
hydrocarbon conversion conditions can provide a high percentage of desired 
products relative to total products. 
SSZ-15 zeolites can be used in processing hydrocarbonaceous feedstocks. 
Hydrocarbonaceous feedstocks contain carbon compounds. They can be from 
many different sources, such as virgin petroleum fractions, recycle 
petroleum fractions, shale oil, liquefied coal, tar sand oil, and, in 
general, can be any carbon containing fluid susceptible to zeolitic 
catalytic reactions. Depending on the type of processing the 
hydrocarbonaceous feed is to undergo, the feed can contain metal or be 
free of metals, it can also have high or low nitrogen or sulfur 
impurities. It can be appreciated, however, that in general the processing 
will be more efficient (and the catalyst more active) the lower the metal, 
nitrogen, and sulfur content of the feedstock. 
The conversion of hydrocarbonaceous feeds can take place in any convenient 
mode, for example, in fluidized bed, moving bed, or fixed bed reactors 
depending on the types of process desired. The formulation of the catalyst 
particles will vary depending on the conversion process and method of 
operation. 
Using SSZ-15 catalysts which contain hydrogenation components, heavy 
petroleum residual stocks, cycle stocks, and other hydrocrackable charge 
stocks can be hydrocracked at temperatures from 175.degree. C. to 
485.degree. C. using molar ratios of hydrogen to hydrocarbon charge from 1 
to 100. The pressure can vary from 0.5 to 350 bar and the liquid hourly 
space velocity from 0.1 to 30. For these purposes, the SSZ-15 catalyst can 
be composited with mixtures of inorganic oxide supports as well as with 
faujasites such as X and Y. 
Hydrocarbon cracking stocks can be catalytically cracked using SSZ-15 at 
liquid hourly space velocities from 0.5 to 50, temperatures from about 
260.degree. F. to 625.degree. F., and pressures from subatmospheric to 
several hundred atmospheres. 
SSZ-15 can be used to dewax hydrocarbonaceous feeds by selectively removing 
straight chain paraffins. The process conditions can be those of 
hydrodewaxing, a mild hydrocracking, or they can be at lower pressures in 
the absence of hydrogen. Dewaxing in the absence of hydrogen at pressures 
less than 30 bar, and preferably less than 15 bar, is preferred as 
significant amounts of olefins can be obtained from the cracked paraffins. 
SSZ-15 can also be used in reforming reactions using temperatures from 
315.degree. C. to 595.degree. C., pressures from 30 to 100 bar, and liquid 
hourly space velocities from 0.1 to 20. The hydrogen to hydrocarbon mole 
ratio can be generally from 1 to 20. 
The catalyst can also be used to hydroisomerize normal paraffins, when 
provided with a hydrogenation component, e.g., platinum. 
Hydroisomerization is carried out at temperatures from 90.degree. C. to 
370.degree. C., and liquid hourly space velocities from 0.01 and 5. The 
hydrogen to hydrocarbon mole ratio is typically from 1:1 to 5:1. 
Additionally, the catalyst can be used to isomerize and polymerize olefins 
using temperatures from 0.degree. C. to 260.degree. C. 
Other reactions which can be performed using the catalyst of this invention 
containing metals such as platinum, include hydrogenation-dehydrogenation, 
denitrogenation, and desulfurization reactions. 
SSZ-15 can be used in hydrocarbon conversion reactions with active or 
inactive supports, with organic or inorganic binders, and with and without 
added metals. These reactions are well known to the art, as are the 
reaction conditions. 
SSZ-15 can also be used as an adsorbent, a filler in paint and paper 
products, and a water-softening agent in detergents. 
The examples illustrate my invention without limiting it.