Note: Descriptions are shown in the official language in which they were submitted.
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ACTIVATION OF ULTRA HIOEI SILICA ZEOLITES
BACKEROUND OF THE INVENTION
Field of the Invention
This invention relates to a method for enhancing the
catalytic activity of certain high silica-containing crystalline
matarials which lnvolves the sequential steps of calcining the
material and contacting the calcined material with a volatile
iron~containing compound having a minimum vapor pressure of 50 mm at
500C. The iron-containing compound contacted material may then be
subjected to heating, hydrolyzing the heated material and calcining
the resulting hydrolyzed material. The silica-containing crystall;ne
material having enhanced activity prepared by the present method
exhibits valuable shape selectivity catalytic properties.
Cescription of Prior Art
High silica-containing zeolites are well known in the art and
it is generally acceoted that the ion exchange capacity of the
crystalline aluminosilicate is directly dependent on its aluminum
content. Thus, for example, the more aluminum there is in a
crystalline structure, the more cations are required to balance the
electronegativity thereof, and when such cations are of the acidic
type such as hydrogen7 they impart catalytic activity to the
crystalline material. On the other hand, high silica-containing
zeolites having little or substantially no aluminum, have many
important properties and characteristics and a high degree of
structural stabil;ty such that they have become candidates for use in
f
various processes inclu~ins catalytic processes. Materials of this
type are known in the art and include high silica-containing
aluminosilicates such as ZSM-5 (U.S. Patent 3,702,886), ZSM-ll (U.S.
Patent 3,709,979), and zeolite ZSM-17 (U.S. Patent 3,832,449) to
; mention a few.
The silica-to-aluMina ratio of a given zeolite is often
variable; for example, zeolite X can be synthesized with a
silica-to-alumina ratio of from 2 to 3; zeolite Y from 3 to about 6.
In some zeolites, the upper limit of silica-to-alumina ratio is
lo virtually unbounded. Zeolite ZSM-5 is one such material wherein the
silica-~o-alunina ratio ls at least 5. U.S. Patent 3,941,871
discloses a crystalline metal organosilicate essentially free of
aluminum and exhibiting an x-ray diffraction pattern characteristic of
ZSM-5 type aluminosilicate. U.S. Patents 4,061,724; 4,073,865 and
4tlO4,294 describe microporous crystalline silicas or silicates
wherein the aluminum content present is at impurity levels.
ecause o, the extremely low aluminum content of these high
silica-containing zeolites, their ion exchange capacity is not as
great as materials with a higher aluminum content. Therefore, when
these materials are cont æ ted with an acidic solution or otherwise
converted to their acidic forms and thereafter are processed in a
conventional manner, they are not as catalytically active as their
higher aluminum-containing counterparts.
The novel process of this invention permits the preparation
of certain ultra high silica-containing materials which have all the
desirable properties inherently possessed by such high silica
materials and, yet, have an enhanced activity for shape selective
catalytic applications which heretofore has only been possible to be
achieved by materials having a higher aluminum content in their "as
synthesized" form. There is evidence to indicate that the zeolites
activated by the present method contain iron as a structural
component. Such a zeolite is shown to be different than a mere
mixture of i m n and the zeolite. Also, the amount of iron
incorporated in the high-silica containing material by the present
3s method is much greater than would be expected by ion exchange relative
the aluminum content of the material. - - -
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It is noted that U.S. Patents 3,354,078 and ~,644,220 relate
to treating crystalline aluminosilicates with volaiile metal halides.
Neither of these latter patents is, however, concerned with treatment
of crystallir,e materials having an ultra high silica-to-alumina mole
ratio of at least 500. Also, U.S. Patent 41350~835~ issued
September 21, 1982 teaches a process for converting gaseous
paraffinic feedstock to aromatics over a catalyst ccmprising gallium
and a zeolite characterized by a constraint index of 1 to 12 and a
sil;ca-to-alumina mole ratio of at least 12. U.S. Patent 4,180,689
teaches use of gallium-containing aluminosilicate zeolite catalysts to
provide improved yields of aromatic hydrocarbons from a feedstock of
C3-C12 hydrocarbons. The zeolite therein has a silica`to-alumina
mole ratio of from 20 to 70 and the gallium is either deposited on or
ion-exchanged into the zeolite. U.S. Patent 4,120,910 teaches use of
a ZSM-5 type al~minosilicate zeolite having incorporated therein a
minor amount of metal from Group VIII, IIB or I8 of the Periodic Table
for catalyzing the conversion of paraffinic hydrocarbons to
aromatics.
SUMMARY OF THE INVENTION
The present invention relates to a novel process for
improving catalytic activity for shape selective catalytic
applications of certain ultra high sil;ca-containing crystalline
zeolites which comprises the essential steps of calcining the ultra
high silica-containing material and cont æ ting the calcined material
at an elevated temperature with a volatile i m n~containing compound
having a minimum vapor pressure of 5Q mm at 50QC, e.g. ferric
chloride. The iron-containing compound contacted zeolite may then, iF
desired, be subjected to heating, hydIolyzing the heateo material and
calcining the hydrolyzed material. The resulting zeolite material
exhibits énhanced activity toward catalysis of numerous chemical
reactions, such as, for example, dehydrogenation and reforming. They
exhibit high selectivites for aromatics production from various
feedstocks, e.g. in dehydrogenation of ethylcyclohexane to aromatic
compourds with preferential formation of the para-xylene isomer and
preferential dehydrogenation of l,'l-dimethyl cyelohexane relative the
1,2-isomer. Evidence suggests that the zeolites treated in accordance
he~e~ith contain iron as a structural component.
I- lZ~lg
DESCRIPTION _F SPECIFIC EMBODIMENTS
The novel process of this invention is concerned with the
treatment of ultra hish silica-containir,g crystalline material. The
expression "ultra high silica-containins crystalline material" is
intended to define a crystalline structure Hhich has a
silica-to-alumina mole ratio greater than 500 up to and including
those highly siliceous materials where the silica-to-alumina mole
ratio is infinity or as reasonably close Jo infinity as practically
possible. Highly sil1ceous materials are exemplified in U.S. patents
3,941,871; 4,061,724; 4,073,aO5 and 4,104,294 wherein the materials
are preparea from reæ tion solutions which involve no deliberate
addition of aluminum. However, t ace quantities of aluminum art
usually present due to the impurity of the reaction solutions. It is
to be understood that the expression ultra high silica-containing
crystalline material" also specifically includes those materials which
have other metals besides silica and/or alumina associated therewith,
such as boron or chromium. Thus, a requirement with regard to the
starting materials utilized in the novel process of this invention is
that they have a silica-to-alumina mole ratio greater tan about 500
(irrespective of what~other materials or metals are present in the
crystal structure).
The crystalline starting materials for the present process
may be synthesized from reaction mixtures containing varicus cation
sources, including as non-limiting examples trial~ylammonium compounds
where alkyl is frcm 1 to about 2a carbon atcms, e.s. ~ripropyl-
ammonium cation sources; quaternary ammonium compounds, e.g.
tetraprGpylammonium cation sources; and compounds containing multiple
cationic centers, e.g. diquaternary ammonium cation sources. The
compounds may be, for example, salts such as halides, e.g. chloride or
bromide, nitrates, etc.
The novel process of this invention is simple and easy to
carry out although the results therefrom are dramatic. The process is
carried out by calcining an ultra high silica crystalline zeolite
material having a silica-to-alumina mole ratio of at least 500 by
heating the same at a temperature within the ra,-se of from about 2C0C
to about 600~C in an atmosphere of air, nitrogen, etc. at atmospheric,
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superatmospheric or subatmospheric pressures for between lo minutes
and 48 hours. The calcined zeolite is thereafter treated with a
volatile im n-containing compound (i.e. having a minimum vapor
pressure of 50 mm at 500C) at a temperature of from about 5ûC to
about 500C, preferably from about 75C to about 300C. If desired,
the iron-containing compound treated zeolite may then be heated to a
temperature in the range of from about 300C to about 600C in an
inert atmosphere of air, nitrogen, etc. for from about lO minutes to
about 48 hours. The heated zeolite may then be hydrolyzed by contact
with water at a temperature of from about ambient room temperature
(e.g. 20C) to about lOûC. The hydrolyzed zeolite may then be
calcined at a temperature of from about 200C to about 600C in an
inert atmosphere of air, nitrogen, etc. at subatmospheric, atmospheric
or superatomspheric pressures for from about lO minutes to about 48
hours.
The iron-containing compound contacting step may be
accomplished by admixture of the i m n-containing compound vapor with
an inert gas such as nitrogen or helium at temperatures ranging from
about 50C to about 500C, preferably from about 75C to about 300C.
The amount of iron-containing compourd vapor which is utilized is not
narrowly critical but usually from about 0.01 to about 2 grams of
iron-containing compou,~d are used per gram of ultra high silica
crystalline material.
The iron-containing compourd for use herein must have a
minimum vapor pressure of about 50 mm at a temperature of 500C. Said
compound may be inorganic or organic. 5uitable inorganic iron
compounds include, as a non-limiting example, salts such as ferric
chloride. A non-limiting example of an organic iron compourd is
ferrocene. Iron carbonyl may also be used. Of course, mixtures of
any of the above volatile iron compounds may be used.
The high-silica crystalline material prepared by the present
method may have its catalytic activity further tailored for specific
chemical conversion by various procedures. One such tailoring
procedure involves incorporation by ion exchange or impregnation of
one or more other metals, such as, for example, Group VI B (e.g. Cr,
Mo and W), IB (e.g. Cu) or IIB (e.g. Zn) metals of the Periodic Table -
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of the Elements. Combinations of the above metals may also be
( utilized in this fashion as well as metals from Group VIII other than
im n (e.g. Co, Ni, Pt and Ir) and their combinations with each other
and the above metals. Another such tailoring procedure involves
treatment of the crystalline material prepared by the present method
by ion exchange or impregnation, or merely effective cont æ t with
Group IA cations (e.g. i+, Na+ and K+) of the Periodic Table.
This latter tailoring procedure reduces any available acid activity
and makes the crystalline material more suitable as a catalyst for
reactions requiring 10~N acid activity, e.g. dehydrogenation.
Compounds which may be used to provide the Group IA cations include,
for example, KOH, K2C03, Na2C03 and NaOH. 4nother such
tailoring method involves ion exchange with hydrogen or hydrogen
precursors by known methods.
The high silica crystalline material product of this
invention exhibits a much larger amount of iIon than would be expected
oy ion exchange of ore staring crystaliine material based on aluminum
content thereof. For example, assuming ion exchange due to presence
of tetrahedrally coordinated aluminum in the starting crystalline
material structure, exchange of Fe+ff therein would provide about
0.002 weight percent iron in a material having a silica-to-alumina
mole ratio of 26,000 and about 0.001 weight percent im n in a 50,000
silica-to-alumina material. Reverence to the specific examples which
follow will indicate much larger quantities of im n present by way of
~5 this invention. This is evidence indicating structural location of
im n introduced by the present method.
Of the ultra high silica zeolite materials advantageously
treated in accordance herewith, zeolites ZSM-5, ZSM- ll and
ZSM-5/ZSM-ll intermediate are particularly noted. ZSM-5 is described
in u.S. Patents 3,702,886 and Re 29,948. zsM-ll is
described in u.S. Patent 3,709,979. ZSM-5/ZSM-ll
intermediate is described in U.S. Patent 4,229,424.
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The activity enhanced high silica crystalline materials
prepared by the present method are useful as catalyst components for a
variety of organic, e.g. hydrocarbon, compound conversion processes.
Such conversion processes include, as non-limiting examples,
desulfurization of sulfur-containing feedstocks with reaction
corditions including a temperature of from about 120C to about 400C,
a hydrogen partial pressure of from about 0.2 atmosphere (bar) to
about 20 atmospheres and a liquid hourly space velocity of from about
0.1 to about 15; dehydrogenating hydrocarbon compounds with reaction
conditions including a temperature of from about 3~0C tc about ,00C,
a pressure of from about 0.1 tmosphere to about 10 atmospheres and a
weight hourly space velocity of from about 0.1 to about 20; converting
paraffins to aromatics with reaction conaitions including a
temuerature of from about lû0C to about 7C0C, a pressure of from
about 0.1 atmosphere to about 60 atmospheres, a weight hourly space
velocity ox from about 0.5 to about 400 and a hydrogen/hydrocarbon
mole ratio of from about 0 to about 20; converting olefins to
aromatics, e.g. benzene, toluene and xylenes, with reaction conditions
including a temperature of from about 100C to about 700C, a pressure
of from about 0.1 atmosphere to about 60 atmospheres, a weight hourly
space velccity of from about 0.5 to about 400 and a
hydrogen/hydrocarbon mole ratio of from about a to aoout 2û;
converting synthesis gas to organic compounds with reaction conditions
including a temperature of from about 230C to about 400C and a
pressure of from about 40 atmospheres to about 400 atmospheres.
Specific chemical reactions of interest for the
shape-selective catalyst prepared herehy include conversion of
n-hexane to benzene; shape-selective conversion of
1,4-di~ethylcyclohexane to p-xylene; conversion of ethylbenzene to
styrene; and the selective conversion of p-ethyltoluene in admixture
with o-ethyltoluene to p-methylstyrene.
In practicing a particularly desired chemical conversion
process, it may be useful to incorporate the above-described activity
enhanced crystalline zeolite with a matrix comprising another material
resistant to the temperature and other conditions employed in the
process. Such matrix material is useful as a blnder and imparts
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greater resistarce to the catalyst for the severe temperature,
pressure and reactant feed stream velocity conditions encountered in
many processes.
Useful matrix materials ir~lude both synthetic ard naturally
occurring substances, as well as inorganic materials such as clay,
silica and/or metal oxides. The latter may be either naturally
occurring or in the form ox gelatinous precipitates or gels including
mixtures of silica and metal oxides. Naturally occurring clays which
oan be composited with the zeolite include tnose of the
montmorillonite ano 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.
Such clays can be used in the raw state as originally mined or
initially subjected to calcination, acid treatment or chemical
modification.
In addition to the foregoing materials, the zeolites employed
herein may be composited with a porous matrix material such as
alumina, silica-alumina, silica-magnesia, silica-zirconia, silica-
thoria, silica-beryllia, and silica-titania, as well as ternary
compositions, such as silica-alumina-thoria, silica-alumina-zirconia,
silica-alumina-magnesia and silica-magnesia-zirconia. The matrix may
be in the form of a cogel. The relative proportions of activity
enhanced zeolite component and inorganic oxide gel matrix, on an
anhydrous basis, may vary widely with the zeolite content ranging from
between about 1 to about 99 percent by weight and more usually in the
range of about 5 to about 80 percent by weight of the dry composite.
The following examples will illustrate the novel process of
the present invention.
EXAMPLE 1
.
Zeolite ZSM-5 having a silica-to-alumina mole ratio of 50,000
was prepared and then calcined at 538C for 8 hours. After cooling,
anhydrous ferric chloride (FeC13) vapors in a nitrogen stTeam were
passed over the zeolite, while the temperature was programmed from
room temperature to 300C at a rate of 2-3C/minute, where it was held
for 1 hour. The temperature was then raised to 500C, where it was
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maintained for an hour. The iron-containing compound ccntacted
material was cooled to about room te~oerature and was then slurried in
water at rocm temperature for 15 minutes. The flltered and washed
resulting catalyst material was then calcined in air at 538C for 8
hours. The yellow b m wn catalyst material obtained was analyzed,
indicating 4.9 weight percent iron.
EXPMPLE 2
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Zeolite ZSM-5 having a silica-to-alumina mole ratio of 26,0~0
was prepared and subjeoted Jo calcination ard cont æ ted with
iIon-containing compound, i.e. anhydr~us ferric chloride, as in
Example 1. The cooled iron-containing compound cont æ ted material was
then slurried in water at room temperature for 17 hours. The filtered
and washed resulting catalyst material was then calcined in air at
538C for 8 hours. The fir~l catalyst material contained 2.8 weight
percent iron by analysis.
EXAMPLE 3
A quantity of the catalyst material prepared in Example 2 was
subjected to ammonium exchange by slurring it in 25 ml lM aqueous
NH4Cl solution containing 2 ml NH40H for 17 hours at room
temperature. The ammonium content of the ion-exchanged material was
greater than û.ll meq/gram indicating significant ammonium exdnange.
As a basis for comparison, the ZSM-5 starting material of Example 2
was subjected to the same ammonium exchange procedure as above and no
significant ammonium exchange was observed, i.e. the ammonium content
was less than 0.01 ,T~q/gram. This is evidence indicating structural
location of iron introduced by the present method.
EXAMPLE 4
To exemplify shape-selective dehydrogenation of isomeric
ethyltoluenes over the catalyst material prepared by way of the
present invention, an equimolar mixture of para- and
ortho-ethyltoluene was reacted over the catalyst material prepared in
Example 2 at 575C and a weight hourly space velocity of û.25 hr 1.
A mixture of isomeric methylstyrenes was obtained including the
meta-isomer. The residual ethyltoluenes were predominantly the
ortho-isomer, indicating preferential conversion of the para-isomer.
