U.S. patent application number 09/188005 was filed with the patent office on 2001-07-19 for highly heat resistant beta- zeolite and absorbent for automobile exhaust gas purification and adsorbent for automobile exhaust gas purificat.
Invention is credited to HIRAMATSU, TAKUYA, MATSUKATA, MASAHIKO, SUZUKI, KENJI, TAKAHASHI, AKIRA, TOMITA, TOSHIHIRO.
Application Number | 20010008624 09/188005 |
Document ID | / |
Family ID | 18143064 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008624 |
Kind Code |
A1 |
TAKAHASHI, AKIRA ; et
al. |
July 19, 2001 |
HIGHLY HEAT RESISTANT BETA- ZEOLITE AND ABSORBENT FOR AUTOMOBILE
EXHAUST GAS PURIFICATION AND ADSORBENT FOR AUTOMOBILE EXHAUST GAS
PURIFICAT
Abstract
A highly heat-resistant and hydrothermal-resistant
.beta.-zeolite having a SiO.sub.2/Al.sub.2O.sub.3 ratio of 80 or
more, which is constituted by primary particles having an average
particle diameter of 30 nm or more or by primary particles having
such a particle size distribution that the 10% particle diameter is
20 nm or more; and an adsorbent for automobile exhaust gas
purification, using said .beta.-zeolite. The .beta.-zeolite and the
adsorbent can be produced reliably so as to have quaranteed
properties.
Inventors: |
TAKAHASHI, AKIRA; (ANN
ARBOR, MI) ; TOMITA, TOSHIHIRO; (NAGOYA-CITY, JP)
; HIRAMATSU, TAKUYA; (NAGOYA-CITY, JP) ; SUZUKI,
KENJI; (NAGOYA-CITY, JP) ; MATSUKATA, MASAHIKO;
(TOKOROZAWA-CITY, JP) |
Correspondence
Address: |
BURR & BROWN
PO BOX 7068
SYRACUSE
NY
13261-7068
US
|
Family ID: |
18143064 |
Appl. No.: |
09/188005 |
Filed: |
November 6, 1998 |
Current U.S.
Class: |
423/716 ;
502/64 |
Current CPC
Class: |
B01D 2253/108 20130101;
B01J 20/18 20130101; B01D 2259/4566 20130101; C01B 39/48 20130101;
B01D 2253/304 20130101; B01D 53/02 20130101; Y10S 423/27 20130101;
B01D 2253/1085 20130101; B01D 53/92 20130101; B01D 2258/01
20130101 |
Class at
Publication: |
423/716 ;
502/64 |
International
Class: |
B01J 029/70; C01B
039/46 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 7, 1997 |
JP |
9-322384 |
Claims
What is claimed is:
1. A highly heat-resistant .beta.-zeolite having a
SiO.sub.2/Al.sub.2O.sub- .3 ratio of 80 or more, which is
constituted by primary particles having an average particle
diameter of 30 nm or more.
2. A highly heat-resistant .beta.-zeolite according to claim 1,
which is constituted by primary particles having an average
particle diameter of 50 nm or more.
3. A highly heat-resistant .beta.-zeolite according to claim 2,
which is constituted by primary particles having an average
particle diameter of 80 nm or more.
4. A highly heat-resistant .beta.-zeolite having a
SiO.sub.2/Al.sub.2O.sub- .3 ratio of 80 or more, which is
constituted by primary particles having such a particle size
distribution that the 10% particle diameter is 20 nm or more.
5. A highly heat-resistant .beta.-zeolite according to claim 4,
which is constituted by primary particles having such a particle
size distribution that the 10% particle diameter is 40 nm or
more.
6. A highly heat-resistant .beta.-zeolite having a
SiO.sub.2/Al.sub.2O.sub- .3 ratio of 80 or more, which is
constituted by primary particles having at least one angular
portion.
7. A highly heat-resistant .beta.-zeolite having a
SiO.sub.2/Al.sub.2O.sub- .3 ratio of 80 or more, which is
constituted by particles giving a full width at half maximum of
reflection peak for (h,k,l)=(3,0,2), of 2.theta.=0.5.degree. or
smaller when the X-ray diffraction pattern is obtained from an
X-ray diffractometer using Cu=K.alpha. as the X-ray source.
8. An adsorbent for automobile exhaust gas purification, comprising
a highly heat-resistant and hydrothermal-resistant .beta.-zeolite
according to claim 1.
9. An adsorbent for automobile exhaust gas purification, comprising
a highly heat-resistant and hydrothermal-resistant .beta.-zeolite
according to claim 4.
10. An adsorbent for automobile exhaust gas purification,
comprising a highly heat-resistant and hydrothermal-resistant
.beta.-zeolite according to claim 6.
11. An adsorbent for automobile exhaust gas purification,
comprising a highly heat-resistant and hydrothermal-resistant
.beta.-zeolite according to claim 7.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a highly heat-resistant and
hydrothermal-resistant .beta.-zeolite and an adsorbent for
automobile exhaust gas purification using the .beta.-zeolite.
[0003] 2. Description of the Related Art
[0004] In order for a catalyst (used for purification of the
exhaust gas emitted from an automobile or the like) to exhibit its
catalytic activity, the catalyst must be heated to an activation
temperature or higher by, for example, the heat of the exhaust gas.
When the temperature of the exhaust gas is low as in the cold start
of engine, the harmful substances in the exhaust gas, such as
hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx)
are hardly purified. The purification of, in particular, HC which
is discharged in a large amount during the cold start of engine, is
an important task to be achieved.
[0005] In order to improve the efficiency of HC purification during
the cold start, there are known techniques of using, as an HC
adsorbent, a molecular sieve made of a crystalline aluminosilicate
such as zeolite or the like and allowing the adsorbent to adsorb HC
while a catalyst used together reaches its activation
temperature.
[0006] For example, in Japanese Patent Application Kokai
(Laid-Open) No. 75327/1990 is disclosed an apparatus for automobile
exhaust gas purification, using a Y type zeolite or mordenite as an
HC adsorbent. Also in Japanese Patent Application Kokai (Laid-Open)
No. 293519/1992 is disclosed use of an HC adsorbent obtained by
subjecting a H.sup.+/ZSM-5 zeolite to ion exchange with Cu and Pd,
in order to alleviate the adverse effect of water adsorption,
attain improved HC adsorption capability, and widen the temperature
range for HC adsorption. For the same purpose, use, as an HC
adsorbent, of a pentasil type metallosilicate subjected to ion
exchange with H, Cu or Pd is proposed in Japanese Patent
Application Kokai (Laid-Open) No. 63392/1994.
[0007] Further in Japanese Patent Application Kokai (Laid-Open) No.
99217/1997 is proposed use, as an HC adsorbent, of an
H.sup.+/.beta.-zeolite having a SiO.sub.2/Al.sub.2O.sub.3 ratio of
100 or more, superior in HC adsorption capability and capable of
maintaining its pore structure even when subjected to an exhaust
gas of 750.degree. C. or higher.
[0008] The SiO.sub.2/Al.sub.2O.sub.3 ratio indicative of the
composition of zeolite framework and/or the ion (e.g. H.sup.+,
Na.sup.+or Cu.sup.2+) presence close to the Al of zeolite framework
for electric charge compensation, which as the yardstick for the
heat resistance of zeolite, have heretofore been used mainly.
[0009] It was found out, however, that two zeolites having the same
SiO.sub.2/Al.sub.2O.sub.3 ratio or the same ion have greatly
different heat resistances when they are produced from different
raw materials or different processes.
[0010] When a zeolite insufficient in heat resistance, particularly
hydrothermal resistance (e.g. heat resistance in automobile exhaust
gas) is used for purification of the exhaust gas emitted from an
internal combustion engine of automobile or the like, the pore
structure of the zeolite is gradually collapsed; therefore, such a
zeolite has had a fear of showing deterioration in purifiability
when used in a high temperature exhaust gas such as emitted during
continuous high-speed engine operation or the like.
[0011] Also, when such a zeolite is used in a catalyst and
subjected to a heating and regeneration treatment for removal of
formed coke or the like, there have been cases that the pore
structure of the zeolite is impaired.
[0012] Thus, it has been a task how to define a highly
heat-resistant and hydrothermal-resistant zeolite by its properties
and produce such a zeolite.
SUMMARY OF THE INVENTION
[0013] In view of the above-mentioned problems of the prior art,
the present inventors made an intensive study on the properties of
zeolite relating to the heat resistance of zeolite. As a result,
the present inventors found out that the heat resistance of a
zeolite has close relations with the average particle diameter,
particle size distribution and particle shape of particles
constituting the zeolite, and/or with the crystal structure of the
zeolite. The finding has led to the completion of the present
invention.
[0014] According to the present invention, there is provided, as a
first invention, a highly heat-resistant .beta.-zeolite having a
SiO.sub.2/Al.sub.2O.sub.3 ratio of 80 or more, which is constituted
by primary particles having an average particle diameter of 30 nm
or more.
[0015] The highly heat-resistant .beta.-zeolite is preferably
constituted by primary particles having an average particle
diameter of 50 nm or more, more preferably by primary particles
having an average particle diameter of 80 nm or more.
[0016] According to the present invention, there is also provided,
as a second invention, a highly heat-resistant .beta.-zeolite
having a SiO.sub.2/Al.sub.2O.sub.3 ratio of 80 or more, which is
constituted by primary particles having such a particle size
distribution that the 10% particle diameter is 20 nm or more.
[0017] The highly heat-resistant .beta.-zeolite is preferably
constituted by primary particles having such a particle size
distribution that the 10% particle diameter is 40 nm or more.
[0018] According to the present invention, there is also provided,
as a third invention, a highly heat-resistant .beta.-zeolite having
a SiO.sub.2/Al.sub.2O.sub.3 ratio of 80 or more, which is
constituted by primary particles having at least one sharpedged
portion.
[0019] According to the present invention, there is also provided,
as a fourth invention, a highly heat-resistant .beta.-zeolite
having a SiO.sub.2/Al.sub.2O.sub.3 ratio of 80 or more, which is
constituted by particles giving a full width at half maximum (FWHM)
in X-ray diffraction pattern at (h,k,l)=(3,0,2), of
2.theta.=0.5.degree. or smaller when the X-ray diffraction pattern
is obtained from an X-ray diffractometer using Cu=Ka as the X-ray
source.
[0020] Generally, a heat-resistant zeolite having crystallinity
shows a sharp X-ray diffraction pattern. In the pattern,
crystallinity was determined by the use of full width at half
maximum of reflection peak for (h,k,l)=(3,0,2).
[0021] Preferably, the highly heat-resistant .beta.-zeolite of the
present invention has at least two elements of the above-mentioned
particular primary particle diameter, particular particle size
distribution, particular particle shape and particular X-ray
diffraction pattern (crystal structure).
[0022] According to the present invention, there is also provided
an adsorbent for automobile exhaust gas purification, comprising
any of the above-mentioned highly heat-resistant
.beta.-zeolites.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is an FE-SEM photograph showing the particle
structure of the highly heat-resistant .beta.-zeolite of Example
1.
[0024] FIG. 2 is a TEM photograph showing the particle structure of
the highly heat-resistant .beta.-zeolite of Example 1.
[0025] FIG. 3 is an electron diffraction photograph showing the
particle structure of the highly heat-resistant .beta.-zeolite of
Example 1.
[0026] FIG. 4 is an FE-SEM photograph showing the particle
structure of the highly heat-resistant .beta.-zeolite of Example
2.
[0027] FIG. 5 is a TEM photograph showing the particle structure of
the highly heat-resistant .beta.-zeolite of Example 2.
[0028] FIG. 6 is an electron diffraction photograph showing the
particle structure of the highly heat-resistant .beta.-zeolite of
Example 2.
[0029] FIG. 7 is another view of the TEM photograph showing the
particle structure of the highly heat-resistant .beta.-zeolite of
Example 2.
[0030] FIG. 8 is another view of the electron diffraction
photograph showing the particle structure of the highly
heat-resistant .beta.-zeolite of Example 2.
[0031] FIG. 9 is an FE-SEM photograph showing the particle
structure of the highly heat-resistant .beta.-zeolite of Example
4.
[0032] FIG. 10 is a TEM photograph showing the particle structure
of the highly heat-resistant .beta.-zeolite of Example 4.
[0033] FIG. 11 is an electron diffraction photograph showing the
particle structure of the highly heat-resistant .beta.-zeolite of
Example 4.
[0034] FIG. 12 is an FE-SEM photograph showing the particle
structure of the highly heat-resistant .beta.-zeolite of Example
5.
[0035] FIG. 13 is an FE-SEM photograph showing the particle
structure of the highly heat-resistant .beta.-zeolite of Example
6.
[0036] FIG. 14 is an FE-SEM photograph showing the particle
structure of the highly heat-resistant .beta.-zeolite of
Comparative Example 1.
[0037] FIG. 15 is a TEM photograph showing the particle structure
of the highly heat-resistant .beta.-zeolite of Comparative Example
1.
[0038] FIG. 16 is an electron diffraction photograph showing the
particle structure of the highly heat-resistant .beta.-zeolite of
Comparative Example 1.
DETAILED DESCRIPTION OF THE INVENTION
[0039] In the .beta.-zeolite of the present invention, each of the
primary particle diameter, the particle size distribution, the
particle shape and the X-ray diffraction pattern (crystal
structure) is allowed to be in a particular range and, as a result,
the present .beta.-zeolite has excellent heat resistance and can be
produced reliably. Therefore, the present .beta.-zeolite can be
suitably used in applications where high heat resistance and high
hydrothermal resistance are required, such as hydrocarbon
adsorption, exhaust gas purification system for internal combustion
engine (e.g. in-line type exhaust gas purification system) and the
like.
[0040] The present invention is hereinafter described in
detail.
[0041] The .beta.-zeolite of the first invention has a
SiO.sub.2/Al.sub.2O.sub.3 ratio of 80 or more and is constituted by
primary particles having an average particle diameter of 30 nm or
more, preferably 50 nm or more. In the present invention, "average
particle diameter" refers to a 50% particle diameter which, when
100 or more primary particles are randomly selected and measured
for their dimensions by the use of a scanning electron microscope
(SEM) or transmission electron microscope (TEM), is a diameter of a
particle falling at the 50% position in number of particles.
[0042] The reason for specifying a SiO.sub.2/Al.sub.2O.sub.3 ratio
of 80 or more is that the adverse effect on the heat resistance of
.beta.-zeolite, given by a SiO.sub.2/Al.sub.2O.sub.3 ratio of less
than 80 is far larger than the favorable effect thereon given by
the above-specified average particle diameter. In other words, the
particle diameter and crystal structure of .beta.-zeolite have
large effects on the heat resistance of .beta.-zeolite only when
the .beta.-zeolite has a SiO.sub.2/Al.sub.2O.sub.3 ratio of 80 or
more.
[0043] The reason why the average particle diameter specified by
the present invention has a favorable effect on the heat resistance
of .beta.-zeolite, is not clear. However, it is presumed that when
the primary particles of .beta.-zeolite are allowed to have a
particle diameter of 30 nm or more, the particles have a small
external surface area per unit weight and are less affected by
water (which acts so as to accelerate the structural destruction of
zeolite), whereby the particles have high heat resistance and
hydrothermal resistance.
[0044] The .beta.-zeolite of the second invention has a
SiO.sub.2/Al.sub.2O.sub.3 ratio of 80 or more and is constituted by
primary particles having such a particle size distribution that the
10% particle diameter is 20 nm or more, preferably 40 nm or
more.
[0045] By allowing the primary particles to have such a particle
size distribution that the 10% particle diameter is 20 nm or more,
it is possible to reduce the number of primary particles having a
small particle diameter and low heat resistance.
[0046] The .beta.-zeolite of the third invention has a
SiO.sub.2/Al.sub.2O.sub.3 ratio of 80 or more and is constituted by
primary particles having at least one sharpedged portion.
[0047] A .beta.-zeolite constituted by primary particles having at
least one sharpedged portion is preferred because the presence of
such primary particles is presumed to improve the particle growth
during crystallization.
[0048] The .beta.-zeolite of the fourth invention has a
SiO.sub.2/Al.sub.2O.sub.3 ratio of 80 or more and is constituted by
particles giving a full width at half maximum of reflection peak
for (h,k,l)=(3,0,2), of 2.theta.=0.5.degree. or smaller when the
X-ray diffraction pattern is obtained from an X-ray diffractometer
using Cu=Ka as the X-ray source.
[0049] Generally, a heat-resistant zeolite having crystallinity
shows a sharp X-ray diffraction pattern. In the pattern,
crystallinity was determined by the use of full width at half
maximum of reflection peak for (h,k,l)=(3,0,2).
[0050] In general, the full width at half maximum of X-ray
diffraction pattern is affected by three parameters, i.e. a
parameter associated with the size of crystal grain, a parameter
associated with crystallinity (e.g. lattice strain), and a
parameter inherent to diffractometer (a diffractometer constant).
The full width at half maximum in the fourth invention is affected
by parameters including the diffractometer constant. Since the
diffractometer constant is determined by the main parameters of
diffractometer, the parameters of the X-ray diffractometer used for
measurement of the full width at half maximum specified in the
fourth invention are shown below.
[0051] 1. Goniometer radius: 185 mm
[0052] 2. Slit
[0053] DS (divergence slit)=SS (scattering slit)=1.degree.
[0054] RS (receiving slit)=0.3 mm
[0055] 3. Graphite-curved monochrometer was used.
[0056] 4. Target: Cu
[0057] 5. Measurement conditions
[0058] Scanning speed: 2.theta.=1/4.degree./min
[0059] Accelerating voltage: 35 kV
[0060] Current: 20 mA
[0061] 6. Cu=Kd.sub.1 and Cu=Kd.sub.2 were separated from each
other, and full width at half maximum was calculated from
Cu=Kd.sub.1.
[0062] When the sizes of primary particles are 100 nm or smaller,
the full width at half maximum is affected by a parameter
associated with the size of crystal grain as mentioned above; in
this case, therefore, the full width at half maximum is affected by
three parameters, i.e. a diffractometer constant, a parameter
associated with the size of crystal grain, and a parameter
associated with crystallinity (e.g. lattice strain). Hence, it is
presumed that when the diameters of primary particles are 100 nm or
smaller, the full width at half maximum of X-ray diffraction
pattern is small (full width at half maximum of reflection peak for
(k,h,l)=(3,0,2), of 2.theta.=0.5.degree. or smaller), the particle
diameter is relatively large or the crystallinity of particle is
good and, as a result, high heat resistance is obtained. When the
sizes of primary particles are 100 nm or larger, the full width at
half maximum is not affected by the size of crystal grain and is
affected by a parameter associated with crystallinity and a
diffractometer constant. It is presumed that when the diameters of
primary particles are 100 nm or larger, the full width at half
maximum of X-ray diffraction pattern is small (full width at half
maximum of reflection peak for (k,h,l)=(3,0,2), of
2.theta.=0.5.degree. or smaller), the crystallinity of particle is
good and, as a result, high heat resistance is obtained.
[0063] Next, description is made on the process for production of
the highly heat-resistant .beta.-zeolite of the present
invention.
[0064] In general, .beta.-zeolite is obtained by adding, to a
silica solution or gel, Al and a template such as
tetraethyl-ammonium cation (TEA cation) or the like and subjecting
the mixture to a hydrothermal treatment using an autoclave or the
like to give rise to crystallization. Further, filtration, washing
with water, drying, TEA removal and calcination are conducted to
obtain usable .beta.-zeolite. When the obtained .beta.-zeolite has
a low SiO.sub.2/Al.sub.2O.sub.3 ratio, it is subjected to an
Al-removing treatment (e.g. an acid treatment, or a steam treatment
at a high temperature) to increase the SiO.sub.2/Al.sub.2O.sub.-
3ratio.
[0065] In order to obtain a highly heat-resistant .beta.-zeolite
whose average particle diameter or particle size distribution is in
the above-mentioned particular range, it is preferred to control
the hydrothermal treatment for crystallization, mentioned in the
above production process. As to the method for controlling the
hydrothermal treatment for crystallization, there are various
methods and there is no particular restriction. Examples thereof
include (1) a method of reducing the gel concentration or adding a
nucleus formation-suppressing agent (e.g. triethanolamine) to
reduce the number of nuclei formed, and (2) a method of extending
the time of the hydrothermal treatment to extend the time for
crystal growth. The hydrothermal treatment for crystallization can
also be controlled by using two or more kinds of silica source in
nucleus formation and crystal growth timing.
[0066] In order to obtain a highly heat-resistant .beta.-zeolite
whose particle shape is as specified above or whose full width at
half maximum of X-ray diffraction pattern is in the above-mentioned
particular range, there is employed, for example, a method of
increasing the concentration of TEA (used as a template) or the
like.
[0067] The highly heat-resistant .beta.-zeolite of the present
invention can also be obtained by a process which comprises adding,
to a Si source (e.g. colloidal silica), an aqueous sodium hydroxide
solution, tetraethylammonium hydroxide (TEAOH) and an Al source
(e.g. aluminum sulfate), heating the resulting mixture with
stirring until a completely dried gel is obtained, feeding the
dried gel into an autoclave so that the gel and water are
separated, and conducting a hydrothermal treatment at a temperature
of about 180.degree. C. for several hours to several hundreds
hours. In this hydrothermal treatment as well, various parameters
such as temperature, time and the like must be controlled.
[0068] The present invention is hereinafter described in detail
with reference to Examples. However, the present invention is in no
way restricted to these Examples.
[0069] The highly heat-resistant H.sup.+/.beta.-zeolites obtained
in Examples were evaluated for performances according to the
following methods.
[0070] [Observation of Particle Form and Measurement of Particle
Size Distribution]
[0071] Particle size and particle shape were observed using a field
emission gum type high resolution scanning electron microscope
(FE-SEM) (JSM-890, a product of Nihon Denshi K.K.) and a
transmission electron microscope (TEM) (JEM-2010, a product of
Nihon Denshi K.K.).
[0072] The accelerating voltage used during FE-SEM observation was
10 kV. During TEM observation, the accelerating voltage was 200 kV
and, in order to determine whether or not each observed particle
was a single crystal, electron diffraction was conducted at a
camera length of 100 cm.
[0073] When the electron diffraction image of a whole particle
showed a spotly periodic regular pattern, the particles were judged
to be primary particles (a single crystal); for other cases, the
particles were judged to be aggregated particles.
[0074] Particle size distribution was determined by using 200
particles randomly selected from the photograph (observed image) of
FE-SEM or TEM and measuring the maximum size on the photograph.
[0075] [Measurement of Full Width at Half Maximum of Reflection
Peak for (h,k,l)=(3,0,2)]
[0076] Using an X-ray diffractometer (RAD-IB, a product of Rigaku
Denki K.K.), powder X-ray diffractometry was conducted using
Cu=K.alpha. as an X-ray source. From the X-ray diffraction pattern
obtained, the full width at half maximum at a peak in the vicinity
of 2.theta.=22.degree. was calculated. The peak shows
(h,k,l)=(3,0,2), and it is the main peak of .beta.-zeolite.
Crystallinity was determined by the use of the full width at half
maximum at this peak. Incidentally, during the measurement, the
accelerating voltage was 35 kV and the current was 20 mA. As a slit
system, there were used a divergence slit (DS) 1.degree., a
scattering slit (SS) 1.degree., and a receiving slit (RS) 0.3 mm.
All but CuKa was removed by the use of a curved monochromator.
Prior to the calculation of full width at half maximum, Cu=Kd.sub.1
was separated form Cu=Kd.sub.2, and full width at half maximum was
obtained from Cu=Kd.sub.1. The ratio of Cu-Kd.sub.2/Cu-Kd.sub.1 was
0.49.
[0077] [Evaluation of Heat Resistance]
[0078] A highly heat-resistant H.sup.+/.beta.-zeolite powder was
subjected to a durability test by placing it on an alumina-made
boat, transferring the boat into an electric furnace, and exposing
the boat to an atmosphere containing 10% of steam, at 1,000.degree.
C. for 4 hours. The specific surface areas of the powder before and
after durability test were measured. The specific surface area
after durability test was divided by the specific surface area
before durability test to calculate the retention (%) of specific
surface area, which was taken as the heat resistance of the
.beta.-zeolite powder.
EXAMPLE 1
[0079] An aqueous sodium hydroxide solution was added to colloidal
silica (30% by weight). To the resulting mixture was added a
solution obtained by mixing aluminum nitrate nonahydrate
[Al(NO.sub.3).sub.3.9H.sub.2O] with an aqueous solution of 35% by
weight of tetraethylammonium hydroxide (TEAOH). The resulting
mixture was stirred until it became homogeneous, to obtain a final
mixture. The final mixture had the following composition.
21Na.sub.2O.10Al.sub.2O.sub.3.300SiO.sub.2.150TEAOH.4000H.sub.2O
[0080] The mixture was placed in a teflon container. The container
was placed in an autoclave and heated at 135.degree. C. for 7 days
at autogenous pressure. Then, the contents in the container was
subjected to centrifugation to obtain a solid reaction product. The
product was separated, washed, dried at 80.degree. C. and
heat-treated in air at 540.degree. C. for 4 hours to remove the
template. The powder obtained was subjected to a steam treatment
(650.degree. C. and 5 hours) and an leaching treatment in 1N
aqueous hydrochloric acid solution. A series of these two
treatments were conducted three times. The resulting powder was
treated in an aqueous ammonium nitrate solution at 80.degree. C.
for 1 hour for the purpose of ion exchange. Then, separation,
washing, drying and calcination were conducted to obtain a highly
heat-resistant H.sup.+/.beta.-zeolite.
EXAMPLE 2
[0081] An aqueous sodium hydroxide solution was added to colloidal
silica (30% by weight). To the resulting mixture was added a
solution obtained by mixing iron (III) nitrate nonahydrate
[Fe(NO.sub.3).sub.3.9H.sub.2O] and aluminum nitrate nonahydrate
[Al(No.sub.3).sub.3.9H.sub.2O] with an aqueous solution of 35% by
weight of tetraethylammonium hydroxide (TEAOH). The resulting
mixture was stirred until it became homogeneous, to obtain a final
mixture. The final mixture had the following composition.
21Na.sub.2O.Al.sub.2O.sub.3.6Fe.sub.2O.sub.3.300SiO.sub.2.150TEAOH.6200H.s-
ub.2O
[0082] The mixture was placed in a teflon container. The container
was placed in an autoclave and heated at 135.degree. C. for 8 days
at autogenous pressure. Then, the contents in the container was
subjected to centrifugation to obtain a solid reaction product. The
product was separated, washed, dried at 80.degree. C. and
heat-treated in air at 540.degree. C. for 4 hours to remove the
template. The resulting powder was treated in an aqueous ammonium
nitrate solution at 80.degree. C. for 1 hour for the purpose of ion
exchange. Then, separation, washing, drying and calcination were
conducted to obtain a highly heat-resistant
H.sup.+/.beta.-zeolite.
EXAMPLE 3
[0083] An aqueous sodium hydroxide solution was added to colloidal
silica (30% by weight). To the resulting mixture was added a
solution obtained by mixing aluminum nitrate nonahydrate
[Al(NO.sub.3).sub.3.9H.sub.2O] with an aqueous solution of 35% by
weight of tetraethylammonium hydroxide (TEAOH). The resulting
mixture was stirred until it became homogeneous, to obtain a final
mixture. The final mixture had the following composition.
21Na.sub.2O.8Al.sub.2O.sub.3.300SiO.sub.2.150TEAOH.3200H.sub.2O
[0084] The mixture was placed in a teflon container. The container
was placed in an autoclave and heated at 135.degree. C. for 6 days
at autogenous pressure. Then, the contents in the container was
subjected to centrifugation to obtain a solid reaction product. The
product was separated, washed, dried at 80.degree. C. and
heat-treated in air at 540.degree. C. for 4 hours to remove the
template. The powder obtained was subjected to a steam treatment
(650.degree. C. and 5 hours) and an leaching treatment in 1N
aqueous hydrochloric acid solution. A series of these two
treatments were conducted three times. The resulting powder was
treated in an aqueous ammonium nitrate solution at 80.degree. C.
for 1 hour for the purpose of ion exchange. Then, separation,
washing, drying and calcination were conducted to obtain a highly
heat-resistant H.sup.+/.beta.-zeolite.
EXAMPLE 4
[0085] An aqueous sodium hydroxide solution and an aqueous solution
of 35% by weight of tetraethylammonium hydroxide (TEAOH) were added
to colloidal silica (30% by weight), and they are stirred at room
temperature. To the resulting mixture was added an aqueous solution
of aluminum sulfate, and the resulting mixture was stirred and
heated up to 80.degree. C. The mixture was further stirred until a
gel is dried to obtain a dried gel for crystallization. The dried
gel had the following composition.
10Na.sub.2O.Al.sub.2O.sub.3.200SiO.sub.2.75TEAOH.500H.sub.2O
[0086] The dried gel was sufficiently ground and then placed in an
autoclave to be subjected to steam treatment at 180.degree. C. for
16 hours at autogenous pressure. In the steam treatment, the dried
gel was separated from water, placed in the autoclave, and heated
in a closed container. Then, the products in the container was
washed with water, subjected to centrifugation, subjected to
washing, dried at 80.degree. C., and heat-treated in air at
540.degree. C. for 4 hours to remove the template. The resulting
powder was treated in an aqueous ammonium nitrate solution at
80.degree. C. for 1 hour for the purpose of ion exchange. Then,
separation, washing, drying and calcination were conducted to
obtain a H.sup.+/.beta.-zeolite molecule sieve.
EXAMPLE 5
[0087] An aqueous sodium hydroxide solution and an aqueous solution
of 35% by weight of tetraethylammonium hydroxide (TEAOH) were added
to colloidal silica (30% by weight), and they are stirred at room
temperature. To the resulting mixture was added an aqueous solution
of aluminum sulfate, and the resulting mixture was stirred and
heated up to 80.degree. C. The mixture was stirred until a
viscosity of the gel rose, and then transferred to a kneader (K-1
type produced by Neotech K.K.). The mixture was further kneaded at
80.degree. C. until the gel was dried to obtain a dried gel for
crystallization. The dried gel had the following composition.
10Na.sub.2O.Al.sub.2O.sub.3.300SiO.sub.2.110TEAOH.320H.sub.2O
[0088] The dried gel was sufficiently ground and then placed in an
autoclave to be subjected to steam treatment at 180.degree. C. for
16 hours at autogenous pressure. In the steam treatment, the dried
gel was separated from water, placed in the autoclave, and heated
in a closed container. Then, the products in the container was
washed with water, subjected to centrifugation, subjected to
washing, dried at 80.degree. C., and heat-treated in air at
540.degree. C. for 4 hours to remove the template. The resulting
powder was treated in an aqueous ammonium nitrate solution at
80.degree. C. for 1 hour for the purpose of ion exchange. Then,
separation, washing, drying and calcination were conducted to
obtain a H.sup.+/.beta.-zeolite molecule sieve.
EXAMPLE 6
[0089] Colloidal silica (30% by weight) and an aqueous sodium
hydroxide solution were added to a solution obtained by mixing an
aqueous solution of aluminum sulfate to an aqueous solution of 35%
by weight of tetraethylammonium hydroxide (TEAOH) to obtain a
mixture. The mixture was stirred to obtain a reacted mixture. The
reacted mixture was heated up to 80 C and stirred until a viscosity
of the gel rose, and then transferred to a kneader (K-1 type
produced by Neotech K.K.). The mixture was further kneaded until
the gel was dried to obtain a dried gel for crystallization. The
dried gel had the following composition.
10Na.sub.2O.Al.sub.2O.sub.3.300SiO.sub.2.110TEAOH.770H.sub.2O
[0090] The dried gel was sufficiently ground and then placed in an
autoclave to be subjected to steam treatment at 180.degree. C. for
16 hours at autogenous pressure. In the steam treatment, the dried
gel was separated from water, placed in the autoclave, and heated
in a closed container. Then, the products in the container was
washed with water, subjected to centrifugation, subjected to
washing, dried at 80.degree. C., and heat-treated in air at
540.degree. C. for 4 hours to remove the template. The resulting
powder was treated in an aqueous ammonium nitrate solution at
80.degree. C. for 1 hour for the purpose of ion exchange. Then,
separation, washing, drying and calcination were conducted to
obtain a H.sup.+/.beta.-zeolite molecule sieve.
COMPARATIVE EXAMPLE 1
[0091] An aqueous sodium hydroxide solution was added to colloidal
silica (30% by weight). To the resulting mixture was added a
solution obtained by mixing aluminum nitrate nonahydrate
[Al(NO.sub.3).sub.3.9H.sub.2O] with an aqueous solution of 35% by
weight of tetraethylammonium hydroxide (TEAOH). The resulting
mixture was stirred until it became homogeneous, to obtain a final
mixture. The final mixture had the following composition.
21Na.sub.2O.10Al.sub.2O.sub.3.300SiO.sub.2.100TEAOH.2000H.sub.2O
[0092] The mixture was placed in a teflon container. The container
was placed in an autoclave and heated at 135.degree. C. for 5 days
at autogenous pressure. Then, the contents in the container was
subjected to centrifugation to obtain a solid reaction product. The
product was separated, washed, dried at 80.degree. C. and
heat-treated in air at 540.degree. C. for 4 hours to remove the
template. The powder obtained was subjected to a steam treatment
(650.degree. C. and 5 hours) and an leaching treatment in 1N
aqueous hydrochloric acid solution. A series of these two
treatments were conducted three times. The resulting powder was
treated in an aqueous ammonium nitrate solution at 80.degree. C.
for 1 hour for the purpose of to ion exchange. Then, separation,
washing, drying and calcination were conducted to obtain a highly
heat-resistant H.sup.+/.beta.-zeolite.
COMPARATIVE EXAMPLE 2
[0093] An aqueous sodium hydroxide solution was added to colloidal
silica (30% by weight). To the resulting mixture was added a
solution obtained by mixing aluminum nitrate nonahydrate
[Al(NO.sub.3).sub.3.9H.sub.2O] with an aqueous solution of 35% by
weight of tetraethylammonium hydroxide (TEAOH). The resulting
mixture was stirred until it became homogeneous, to obtain a final
mixture. The final mixture had the following composition.
21Na.sub.2O.10Al.sub.2O.sub.3.300SiO.sub.2.150TEAOH.4000H.sub.2O
[0094] The mixture was placed in a teflon container. The container
was placed in an autoclave and heated at 130.degree. C. for 7 days
at autogenous pressure. Then, the contents in the container was
subjected to centrifugation to obtain a solid reaction product. The
product was separated, washed, dried at 80.degree. C. and
heat-treated in air at 540.degree. C. for 4 hours to remove the
template. The powder obtained was subjected to a steam treatment
(650.degree. C. and 5 hours) and an leaching treatment in iN
aqueous hydrochloric acid solution. A series of these two
treatments were conducted three times. The resulting powder was
treated in an aqueous ammonium nitrate solution at 80.degree. C.
for 1 hour for the purpose of ion exchange. Then, separation,
washing, drying and calcination were conducted to obtain a highly
heat-resistant H.sup.+/.beta.-zeolite.
[0095] For the highly heat-resistant H.sup.+/.beta.-zeolites
obtained in Examples 1 to 6 and Comparative Examples 1 to 2, the
particle forms were observed and the particle size distributions
were measured. The results are shown in FIGS. 1 to 16 and Table
1.
1 TABLE 1 Particle size distribution 10% particle 50% particle 90%
particle diameter (nm) diameter (nm) diameter (nm) Example 1 39 65
87 Example 2 83 220 282 Example 3 18 40 62 Example 4 76 96 120
Example 5 72 98 118 Example 6 180 224 263 Comparative 9 18 23
Example 1 Comparative 12 23 34 Example 2
[0096] Also for the highly heat-resistant H.sup.+/.beta.-zeolite
obtained in Examples 1 to 6 and Comparative Examples 1 to 2, the
full width of half maximum of X-ray diffraction pattern were
measured and the heat resistances were evaluated. The results are
shown in Table 2.
2 TABLE 2 Specific surface area After FWHM of Before dura- Re-
reflection durability bility ten- SiO.sub.2/Al.sub.2O.sub.3 peak
for test test tion ratio (h, k, l) = (3, 0, 2) (m.sup.2/g)
(m.sup.2/g) (%) Ex. 1 120 0.259 630 390 62 Ex. 2 130 0.278 610 430
70 Ex. 3 110 0.523 630 370 59 Ex. 4 200 0.332 520 380 73 Ex. 5 300
0.235 470 390 83 Ex. 6 300 0.188 520 440 85 Comp. 120 0.623 620 270
44 Ex. 1 Comp. 150 0.659 590 290 49 Ex. 2 FWHM (= full width at
half maximum)
[0097] (Discussion on Results of Examples 1 to 6 and Comparative
Examples 1 to 2)
[0098] In the highly heat-resistant .beta.-zeolite of Example 1,
the electron diffraction image of whole particles shows a periodic
regular pattern in FIG. 3 and, therefore, each particle observed is
a primary particle (a single crystal). Meanwhile, in the
.beta.-zeolite of Comparative Example 1, the electron diffraction
image shows no regular pattern as seen in FIG. 16 and, therefore,
the particles are judged to be aggregates of particles of 10 to 30
nm in size.
[0099] In the highly heat-resistant .beta.-zeolite of Example 1,
the primary particles have an sharpedged shape as seen in FIGS. 1
and 2 (Example 1).
[0100] The highly heat-resistant .beta.-zeolite of Example 2
appears, from the FE-SEM photograph of FIG. 4, to be aggregated
particles having a primary particle diameter of about 100 nm.
However, since the electron diffraction image of whole particles of
FIG. 6 shows a periodic regular pattern and a clear spot image, the
particles shown in FIG. 5 are judged to be a single crystal.
Further, the highly heat-resistant .beta.-zeolite of Example 2
appears, from the electron diffraction image of FIG. 8, to be
aggregated particles as in FIG. 4; however, the particles of FIG. 7
are judged to be constituted by primary particles having particle
diameters of about 100 to 300 nm.
[0101] In the highly heat-resistant .beta.-zeolite of Example 4,
the electron diffraction image of whole particles shows a periodic
regular pattern in FIG. 11 and, therefore, each particle observed
is a primary particle (a single crystal). It was found that the
particles have an sharpedged shape as seen in the FE-SEM photograph
of FIG. 9 and the TEM photograph of FIG. 10.
[0102] Further, in the highly heat-resistant .beta.-zeolite of
Examples 5 and 6, the particles have an sharpedged shape as seen in
the FE-SEM photographs of FIGS. 11 and 12.
[0103] As is clear from the results of Table 2, the highly
heat-resistant .beta.-zeolites of Examples 1 to 6, as compared with
the .beta.-zeolites of Comparative Examples 1 to 2, are superior in
heat resistance.
[0104] In the highly heat-resistant .beta.-zeolites of Examples 1
to 2 and Examples 4-6, the particle size distribution is such that
the 10% particle diameter is 20 nm or larger, as seen in the
results of Table 1; and the full width at half maximum of
reflection peak for (h,k,l)=(3,0,2) is 2.theta.=0.5.degree. or
smaller as seen in the results of Table 2.
[0105] As stated above, the highly heat-resistant .beta.-zeolite of
the present invention and the adsorbent for automobile exhaust gas
purification, using said zeolite can be produced reliably so as to
have guaranteed properties, by controlling the average particle
size, particle size distribution, particle shape and crystal
structure (these items are new yardsticks for determining the heat
resistance of zeolite); and can suitably be used in applications
where high heat resistance and high hydrothermal resistance are
required, such as adsorption of hydrocarbons, exhaust gas
purification system for internal combustion engine (e.g. exhaust
gas purification system of in-line type) and the like.
* * * * *