Molecular sieve abstract
Disclosed is a carbon molecular sieve material. It is prepared
by a method comprising the step of adsorbing a mixture of an aqueous
carbohydrate solution and an acid or a polymer precursor into pores
of an inorganic molecular sieve material; drying and polymerizing
the adsorbates; re-adsorbing a mixture of an aqueous carbohydrate
solution and an acid or a polymer precursor onto the resultant mixture
obtained in the previous steps, and drying and polymerizing the
adsorbates; carbonizing the adsorbates through thermal decomposition;
and removing the framework of the inorganic molecular sieve from
the carbonized adsorbates by use of a fluoric acid or a sodium hydroxide
solution. With uniformity in pore size and regularity in structure,
the carbon molecular sieve is suitable for use in catalysts, adsorbents,
supports, sensors, electrodes, etc.
Molecular sieve claims
What is claimed is:
1. A method for preparing a carbon molecular sieve material comprising
the steps of: a) adsorbing into the pores of an inorganic molecular
sieve material selected from the group consisting of MCM-48 SBA-1
KIT-1 SBA-15 and MSU-1 a starting material selected from the group
consisting of: (i) a polymer precursor; and (ii) a mixture of an
aqueous carbohydrate solution and an acid; wherein said inorganic
molecular sieve material is the solid acid form thereof when the
selected starting material comprises a polymer precursor; b) drying
and polymerizing the adsorbates; c) optionally repeating the steps
of adsorbing, drying and polymerizing; d) carbonizing the polymerized
adsorbates by thermal decomposition; and e) removing the framework
of the inorganic molecular sieve from the carbonized adsorbates
of the sieve material by treating the sieve material with a solution
of hydrofluoric acid or sodium hydroxide.
2. The method as set forth in claim 1 wherein the carbohydrate
is selected from the group consisting of sucrose, xylose and glucose
and the polymer precursor is selected from the group consisting
of furfuryl alcohol, aniline, acetylene and propylene.
3. The method as set forth in claim 1 wherein the molecular sieve
material comprises a structure in which channels are three-dimensionally
arranged or one-dimensional channels are connected to each other
via micropores.
4. The method as set forth in claim 1 further comprising the step
of: f) impregnating a transition metal into pores of the carbon
molecular sieve material.
5. The method as set forth in claim 4 wherein the transition metal
is selected from the group consisting of platinum, gold, palladium,
ruthenium, molybdenum and combinations thereof.
6. The method as set forth in claim 1 wherein the carbon molecular
sieve material has an X-ray diffraction pattern at a diffraction
angle of 5.degree. or less, and has a regular structure with uniform
pore sizes.
7. The method as set forth in claim 1 wherein the thermal decomposition
is performed in the temperature range of 500 to 1200.degree. C.
for 1 to 12 hours under vacuum or oxygen-free atmosphere, wherein
the temperature is increased to this range over a period of 1 to
12 hours.
8. The method as set forth in claim 1 wherein the carbohydrate
or the polymer precursor is adsorbed into the inorganic sieve material
in an amount in the range of 0.1 to 3 g, per gram of inorganic molecular
sieve material.
9. The method as set forth in claim 1 wherein the solid acid form
is an aluminum-substituted inorganic molecular sieve.
10. The method as set forth in claim 1 wherein the acid is selected
from sulfuric acid, hydrochloric acid, nitric acid and phosphoric
acid.
11. The method as set forth in claim 1 wherein the drying and
polymerizing step is performed in the temperature range of 50 to
400.degree. C., wherein the temperature is raised to this range
over a period of 5 minutes to 24 hours.
Molecular sieve description
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates, in general, to a carbon molecular
sieve material and, more particularly, to a carbon molecular sieve
material with structural regularity, which is suitable for use in
catalysts, adsorbents, carriers, sensors, and electrodes. Also,
the present invention is concerned with a method for preparing such
a carbon molecular sieve material. In addition, the present invention
is directed to use of the carbon molecular sieve material.
2. Description of the Prior Art
Among porous materials, those having three-dimensionally arranged
pores with uniform sizes, like zeolite, are defined as molecular
sieves. Since the uniform pores make such molecular sieves be selective
for specific sizes of molecules, they are extensively used as catalysts,
catalyst supports, or adsorbents.
Compared with metal oxide type molecular sieves such as zeolite,
carbon molecular sieves are found to have advantages in thermal
stability, hydrothermal stability, chemical resistance and lipophilicity,
and active research and development is directed to carbon molecular
sieves.
Most of the carbon molecular sieves having been developed thus
far are synthesized through the pyrolysis of natural vegetable materials
such as coconut or synthetic polymers. Owing to higher sparsity
of impurities such as metals or metal oxides, carbon molecular sieves
are dominantly prepared from synthetic polymers. Such carbon molecular
sieves are, for the most part, 0.5 nm or less in pore size. By controlling
the thermal decomposition temperatures or by an after-treatment
with oxygen, their pore sizes can be increased, but to a limited
degree.
In the meanwhile, there has been made many efforts to synthesize
carbon sieves by selectively adsorbing polymers or propylene gas
onto active carbon and decomposing them. The resultant materials
have relatively uniform distribution in pore size compared with
the active carbon, so that they show properties of molecular sieves.
However, because of the absence of regularity in their whole structures,
the X-ray diffraction patterns of the above materials are close
to those of amorphous carbons. In addition, the techniques suffer
from disadvantages in that conditions for the adsorption and decomposition
are quite stringent.
In adsorption and separation functions, conventional carbon molecular
sieves having developed thus far are restrained to small molecules.
For instance, they have been used as adsorbents for storing small
molecules such as hydrogen and methane or to separate nitrogen or
oxygen from the air.
Recently, a group of researchers at Mobil Co. reported a series
of mesoporous molecular sieves, named the M41S series, including
MCM-41 and MCM-48 as disclosed in U.S. Pat. Nos. 5057296 and 5102643.
Since then, various mesoporous molecular sieves, such as SBA-1
SBA-15 KIT-1 and MSU-1 have been developed.
Ranging, in pore size, from 2 to 30 nm, mesoporous molecular sieves
are synthesized through a liquid crystal template pathway by using
surfactants as templates. These mesoporous molecular sieves have
advantages in that their pore sizes can be adjusted in a range of
1.6 to 30 nm by controlling the kinds of surfactants or synthetic
conditions employed during the production process. Further, they
can be synthesized to have various structures by virtue of the versatility
of the templates. In past, research was made on template techniques
in which various organic materials were filled within the pores
of zeolite and thermally decomposed, followed by removing the silica
framework to produce carbon molecular sieves. However, such techniques
are found to fail because, when the template zeolite is removed,
the carbon structure does not stand by itself, but collapses.
SUMMARY OF THE INVENTION
Leading to the present invention, the intensive and thorough research
on carbon molecular sieves, repeated by the present inventors aiming
to overcome the above problems encountered in prior arts, resulted
in the finding that specific inorganic mesoporous molecular sieves
are useful as templates from which carbon molecular sieves can be
synthesized with uniform pore sizes and structural regularity. Using
a carbonization method of the present invention, there can be obtained
carbon molecular sieves in which pores with uniform diameters are
regularly arranged. Such materials with regularity can find numerous
applications in catalyst supports, organic adsorbents, sensors,
electrodes, etc.
Therefore, it is an object of the present invention to provide
a method for preparing structurally regular carbon molecular sieves
in which pores with uniform diameters are three-dimensionally arranged.
It is another object of the present invention to provide carbon
molecular sieves with structural regularity.
It is another object of the present invention to provide use of
the structurally regular carbon molecular sieves.
In accordance with the present invention, there is provided a method
for preparing a carbon molecular sieve material comprising the steps
of: adsorbing a mixture of an aqueous carbohydrate solution and
an acid or a polymer precursor into pores of an inorganic molecular
sieve material; drying and polymerizing the adsorbates; re-adsorbing
a mixture of an aqueous carbohydrate solution and an acid or a polymer
precursor onto the resultant mixture obtained in the previous steps,
and drying and polymerizing the adsorbates; carbonizing the adsorbates
through thermal decomposition; and removing the framework of the
inorganic molecular sieve from the carbonized adsorbates by use
of a hydrofluoric acid or a sodium hydroxide solution.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and other advantages of the
present invention will be more clearly understood from the following
detailed description taken in conjunction with the accompanying
drawings, in which:
FIG. 1 is an electron micrograph of the carbon molecular sieve
CMK-1 prepared using a mesoporous molecular sieve MCM-48 as a template
according to an embodiment of the present invention;
FIG. 2 shows scanning electron micrographs of the MCM-48 used as
a template (a) and the CMK-1 (b) obtained by removing the silica
framework with NaOH after the thermal decomposition of sucrose in
pores of the MCM-48;
FIG. 3 shows X-ray diffraction patterns of MCM-48 used as a template
and CMK-1 synthesized by use of MCM-48 as a template;
FIG. 4 shows argon adsorption-desorption isotherms of CMK-1 synthesized
by use of MCM-48 as a template, with a pore size distribution curve
for CMK-1 obtained by the Horvarth-Kawazoe method and the Barrett-Joyner-Halenda
(BJH) method;
FIG. 5 shows X-ray diffraction patterns of the mesoporous molecular
sieve SBA-1 and the CMK-2 synthesized by use of SBA-1 as a template;
FIG. 6 shows an X-ray diffraction pattern of CMK-1 synthesized
from furfuryl alcohol by use of aluminum-substituted MCM-48 as a
template;
FIG. 7 shows an X-ray diffraction pattern of CMK-1 synthesized
from acetylene gas by use of aluminum-substituted MCM-48 as a template;
and
FIG. 8 shows pore size distribution curves for CMK-1 samples using
as templates MCM-48 materials with different pore sizes, obtained
by means of the BJH method.
DETAILED DESCRIPTION OF THE INVENTION
The present invention contemplates carbon molecular sieves with
orderly arranged pores of uniform sizes, which are synthesized after
removing templates of inorganic molecular sieves. Into inorganic
molecular sieve pores is adsorbed an organic material or a polymer
which is then polymerized under a catalytic action of an acid and
thermally decomposed to form carbon. The silica framework of the
inorganic molecular sieve is dissolved in a hydrofluoric acid or
a sodium hydroxide solution leaving a carbon molecular sieve (hereinafter
referred to as "CMK") with structural regularity.
First, a mixture of a carbohydrate solution and an acid or a precursor
of polymer is adsorbed in a molecular sieve. Suitable as a molecular
sieve are MCM-48 (Ia3d) and SBA-1 (Pn3m), each of which has a cubic
structure in which channels are arranged three-dimensionally, and
KIT-1 and MSU-1 each of which has three-dimensionally, disorderly
channels. Also useful are various mesoporous molecular sieves such
as SBA-15 (Zhao et al., Science, 1998 279 548.) in which one-dimensional
channels are connected to each other via micropores. In the present
invention, MCM-48 and SBA-1 are used as templates for synthesizing
carbon molecular sieves which are named "CMK-1" and "CMK-2",
respectively. MCM-48 can be prepared by the method of Kim et al.,
(Chem. Commun., 1998 259) for its preparation and SBA-1 by the
method of Kim and Ryoo (Chem, Mater., 1999 11 487).
Used as a source of the CMKs, carbohydrates are preferably exemplified
by water-soluble monosaccharides, such as sucrose, xylose, glucose,
etc., disaccharides and polysaccharides. In addition, organic precursor
materials such as furfuryl alcohol and aniline, and gases such as
acetylene and propylene may be useful as sources of the CMKs.
Preferably, the used amount of the organic material is as much
as a carbon amount corresponding to the total pore volume of the
inorganic molecular sieve. If the organic material is used at a
larger amount, an amorphous carbon mass is formed. Usually, the
amount of carbohydrates or organic materials necessary to fill pores
of molecular sieves of 1 g is in the range of 0.1 to 3 g. When carbohydrates
are to be dissolved in water for use, no limitation is imposed on
the amount of water. However, too excessive an amount of water requires
too long a period of time which it takes to dry the carbohydrates
in a drying step, later. Accordingly, sufficient is an amount allowing
to submerge the inorganic molecular sieves under water.
Any acid, if it can polymerize the hydrates or the polymer precursors,
may be used in the present invention. Preferable is sulfuric acid,
hydrochloric acid, nitric acid or phosphoric acid. In addition,
solid acids which are prepared by charging aluminum into mesoporous
molecular sieves may be used for this purpose. Sufficient is the
minimal amount at which the acid is allowed to serve as a catalyst
for condensing or polymerizing carbohydrates or organic materials.
Next, the organic materials adsorbed in the pores of the molecular
sieves are dried and polymerized at an appropriate temperature for
a predetermined period of time under an appropriate atmosphere.
In this step, the drying and polymerization is performed preferably
at 50 to 400.degree. C., to which it preferably takes five minutes
to 24 hours to raise the reaction temperature. Depending on the
adsorbed materials, the drying and polymerization may be performed
in the air, under vacuum or in an oxygen-free atmosphere.
Afterwards, additional carbohydrates or polymer precursors are
re-adsorbed into the molecular sieves having polymerized adsorbates,
and dried and polymerized. This step, a repetition of the adsorbing
and the drying and polymerizing steps, may be omitted depending
on kinds of the mesoporous molecular sieves and the adsorbates.
Then, the adsorbates in the molecular sieves are thermally decomposed
at an appropriate temperature for a predetermined period of time
under a suitable atmosphere. In this regard, the thermal decomposition
is preferably conducted at 500 to 1200.degree. C. to which it is
preferable to raise the temperature within 1 to 24 hours. Also,
the temperature is preferably maintained for 1 to 12 hours. By controlling
the thermal decomposition temperature, the amount of the oxygen
present on the surface of the CMK may be controlled. A vacuum or
an oxygen-free atmosphere is suitable for the thermal decomposition.
Thereafter, the inorganic framework of the molecular sieves is
removed from the carbonized mixture by use of a hydrofluoric acid
or an aqueous sodium hydroxide solution to obtain desired carbon
molecular sieves. For instance, when 1 g of an inorganic molecular
sieve is used as a template to synthesize CMK, about 50 to 100 ml
of an aqueous 10 wt % hydrofluoric solution or 30 to 60 ml of a
1M sodium hydroxide solution is preferably used. A smaller amount
may not dissolve the inorganic framework of the template.
In the adsorbing and the re-adsorbing step, a mixture of an aqueous
carbohydrate solution and an acid or polymer precursors are adsorbed
along with a metal element selected from the group consisting of
platinum, gold, palladium, ruthenium, molybdenum, and transition
metals, so as to enhance the functionality of the molecular sieves.
Likewise, a metal element selected from the group consisting of
platinum, gold, palladium, ruthenium, molybdenum and transition
metals may be adsorbed into pores of the carbon molecular sieves
thus obtained.
In a view of structures, the CMK prepared according to the above-described
procedure is inverse to the inorganic molecular sieves which serve
as templates. Thus, the CMK can be versatile in structure and morphology
in accordance with the templates.
With reference to FIG. 1 there is an electron micrograph of the
CMK-1 which is prepared from sucrose with MCM-48 serving as a template.
As shown in FIG. 1 CMK-1 has a cubic structure in which carbon
framework units are uniformly connected to one another on the whole.
In addition, CMK-1 has pores which reflect the shapes of the template
MCM-48 particles as they are. Scanning electron micrography is useful
to recognize the conformational relation between the product and
the template. FIGS. 2a and 2b are scanning electron microphotographs
of MCM-48 and CMK-1 respectively. As seen, the truncated octahedral
shapes of MCM-48 particles are maintained, as they are, in the structure
of the CMK-1 after the template is removed.
With reference to FIG. 3 there are X-ray diffraction analysis
results of MCM-48 which served as a template, and CMK-1 which
was patterned after the template. In the diffraction pattern of
CMK-1 there appears a new peak corresponding to (110) diffraction
of MCM-48 which is not symmetry allowed for the Ia3d cubic structure,
indicating that the carbon molecular sieve is rearranged from an
Ia3d cubic structure to a different structure. Element analysis
shows that the carbon framework constituting the carbon molecular
sieve can be represented by C.sub.12 HO upon treatment at 900.degree.
C. and by C.sub.16 HO upon treatment at 1100.degree. C. Also, the
peaks read at 1350 and 1590 cm.sup.-1 in Raman spectra show that
the structure of the carbon framework is amorphous. It is, however,
believed that the carbon framework may be crystallized by controlling
the treatment temperature. The carbon molecular sieves according
to the present invention show X-ray diffraction patterns at a diffraction
angle of 5.degree. or less and are uniform in pore size with structural
regularity.
From the data of the argon adsorption-desorption curve and pore
size distribution diagram of FIG. 4 it is apparent that CMK-1 possesses
a small portion of micropores and a majority of mesopores which
are uniformly about 3.0 nm in size. In addition, CMK-1 is characterized
by a BET adsorption area of 1380 cm.sup.-1 and a pore volume of
1.06 cm.sup.3. MCM-48 templates different in pore size, even if
they have a Ia3d cubic structure, allow the synthesis of CMK-1 different
in pore size.
Besides MCM-48 various three-dimensional structures of mesoporous
molecular sieves can be used as templates in synthesizing CMK. For
instance, SBA-1 being of a Pm3n cubic structure, is used to synthesize
CMK-2 whose spectral characteristics are found in the X-ray diffraction
patterns of FIG. 5.
CMK materials can find various applications in supports for catalytically
active materials, catalysts, adsorbents of organic materials, sensors,
electrode materials, etc. When used as a catalyst support, CMK-1
enhances excellent catalytic activity. For example, after being
impregnated at amounts of 2% and 5% into CMK-1 platinum is subjected
to reduction under vacuum to form platinum clusters. When these
platinum clusters were used for hydrogen adsorption, results were
obtained as shown in Table 1 below. As apparent, the platinum clusters
can be formed at a size as small as about 2 nm on CMK-1 and the
platinum-impregnated CMK-1 is very useful as a catalyst for the
reaction of hydrophobic organic compounds, such as hydrogen addition
and reduction.
TABLE 1 Hydrogen Adsorption of Platinum Clusters on CMK-1 Samples
H/Pt 2 wt % Pt/CMK-1 1.0 5 wt % Pt/CMK-1 0.8
A better understanding of the present invention may be obtained
in light of the following examples which are set forth to illustrate,
but are not to be construed to limit, the present invention.
PREPARATION EXAMPLE I
Preparation of MCM-48
Based on the teaching disclosed in Chem. Commun., 1998 p 259 by
Kim et al., the preparation of MCM-48 was performed as follows.
A solution of 12.3 g of ethanol in 105.2 g of water was mixed with
15.8 g of hexadecyltrimethyl ammonium bromide (HTABr) to give Solution
A. Separately, 9.4 g of Ludox HS40 (trade name of DuPont, colloid
silica) was mixed with 33 g of an aqueous 1.0 M sodium hydroxide
solution and heated at 80.degree. C. for 2 hours to give Solution
B. Solution A and Solution B were mixed with each other by dropwise
addition of Solution B for 1 hour at room temperature while vigorously
stirring Solution A in a polypropylene bottle with a magnetic bar.
In this mixture, the mole ratio of SiO.sub.2 to HTABr was 1:0.7
with SiO.sub.2 :Na.sub.2 O:ethane:H.sub.2 O=1:0.25:3.5:100. The
resultant mixture was subjected to reaction at 100.degree. C. for
four days. The precipitate thus obtained was filtered off, washed
with 2.degree. distilled water and dried at 100.degree. C.
PREPARATION II
Preparation of MCM-48
Preparation of MCM-48 was achieved in a method developed by the
present inventors as follows.
3.5 g of hexadecyltrimethylammonium (HTABr) and 0.84 g of LE-4
(C.sub.12 H.sub.25 O(CH.sub.2 CH.sub.2 O).sub.4 H) was mixed with
40.4 g of water to give Solution A. Separately, 9.4 g of Ludox HS40
(trade name of DuPont, colloid silica) was mixed with 31 g of an
aqueous 1.0 M sodium hydroxide solution and heated at 80.degree.
C. for 2 hours to give Solution B. Solution A and Solution B were
mixed with each other by dropwise addition of Solution B for 1 hour
at room temperature while vigorously stirring Solution A in a polypropylene
bottle with a magnetic bar. In this mixture, the mole ratio of HTABr
to LE-4 was 0.81: 0.19 with HTABr:SiO.sub.2 :Na.sub.2 O:H.sub.2
O=0.81:5:1.25:400. The resultant mixture was subjected to reaction
at 100.degree. C. for two days, cooled to room temperature and neutralized
to 10 in pH with an aqueous 30 wt % acetic acid solution. The same
reaction, cooling and neutralization procedure was repeated twice
more. The precipitate thus obtained was filtered off, washed with
2.degree. doubly distilled water and dried at 100.degree. C.
PREPARATION EXAMPLE III
Preparation of SBA-1
Based on the teaching disclosed in Chem. Mater. Vol. 11 p 487
by Kim and Ryoo, the preparation of SBA-1 was conducted as follows.
0.59 g of hexadecylethylammonium bromide (HTEABr) was dissolved
in 100 ml of an aqueous 4.08 M hydrochloric acid (HCl) to give Solution
A. While being stirred in ice water, Solution A was cooled to 0.degree.
C. and then, added with 1.55 g of tetraethyl orthosilicate (TEOS).
In the reaction mixture, the molar ratio of HTEABr:TEOS:HCl:H.sub.2
O was 1:5 280:3500. After further stirred at 0.degree. C. for an
additional 2 hours, the reaction mixture was heated to 100.degree.
C. under reflux and allowed to react for one hour. The precipitate
thus formed was quickly dried in a hot state with the aid of an
aspirator. This aspiration was conducted for 30 min so that the
hydrochloric acid was removed to a substantial degree. Finally,
the precipitate was completely dried in an oven maintained at 140.degree.
C.
PREPARATION EXAMPLE IV
Metal Impregnation for the Preparation of Aluminum-Substituted
Mesoporous Molecular Sieves
Based on the teaching disclosed in Chem. Commun., 1999 p 2225
by Ryoo et al., impregnation of aluminum into frameworks of mesoporous
molecular sieves MCM-41 MCM-48 SBA-1 KIT-1 and MSU-1 was achieved
as follows.
To remove surfactants present within pure silica frameworks of
preexisting mesoporous molecular sieves, they were washed with an
ethanol-hydrochloride mixture solution. The surfactant-removed mesoporous
molecular sieves were immersed in a solution of anhydrous aluminum
chloride (AlCl.sub.3) in 50 ml of absolute ethanol and stirred at
room temperature. After one hour of the stirring, the samples were
filtered, washed cleanly with absolute ethanol, and dried at 140.degree.
C. In the air, the dried samples were calcined at 550.degree. C.
for five hours.
EXAMPLE I
While the MCM-48 prepared in Preparation Example I served as a
template, carbon molecular sieves CMK-1 were prepared from various
amounts of sucrose. For this, first an aqueous sucrose solution
was added with sulfuric acid, as indicated in Table 2 below, to
give Solution A. Values given in Table 2 were quantities per g of
MCM-48. The calcined MCM-48 was put in Solution A, which was dried
and polymerized by slowly heating to 145.degree. C. This sample
was treated at 200.degree. C. under vacuum to remove the sulfuric
acid and water remaining unreated in pores of MCM-48. After being
put in Solution B which was prepared by adding sulfuric acid in
an aqueous sucrose solution, the sample was subjected to the same
drying and polymerization as in above, followed by thermal decomposition
at 900.degree. C. under vacuum. The composition of Solution B is
given in Table 3 below. Following this carbonization, the MCM-48
silica framework, serving as a template, was removed using an aqueous
1 M NaOH solution and a small amount of ethanol. CMK-1 thus obtained
was analyzed in X-ray diffraction patterns which are shown in FIG.
3.
TABLE 2 Composition of Solution A Sucrose Sol'n (wt %) Sucrose
Sol'n (g) Sulfuric acid (ml) 18.1 6.9 0.15
TABLE 3 Composition of Solution B Sucrose Sol'n (wt %) Sucrose
Sol'n (g) Sulfuric acid (ml) 11.7 6.4 0.15 15.0 6.6 0.15 18.1 6.9
0.15
EXAMPLE II
While the SBA-1 prepared in Preparation Example III served as a
template, carbon molecular sieves CMK-2 were prepared from various
amounts of sucrose. For this, first, a sucrose solution was added
with sulfuric acid to give Solution A. The calcined SBA-1 was put
in Solution A, which was dried and polymerized by slowly heating
to 145.degree. C. This sample was treated at 200.degree. C. under
vacuum to remove the sulfuric acid and water remaining unreated
in pores of SBA-1. After being put in Solution B which was prepared
by adding sulfuric acid in an aqueous sucrose solution, the sample
was subjected to the same drying and polymerization as in above,
followed by thermal decomposition at 900.degree. C. under vacuum.
The compositions of Solutions A and B are the same as in Example
I. Following this carbonization, the SBA-1 silica framework, serving
as a template, was removed using an aqueous 1 M NaOH solution and
a small amount of ethanol. CMK-2 thus obtained was analyzed in X-ray
diffraction patterns which are shown in FIG. 5.
EXAMPLE III
While an Al-substituted MCM-48 served as a template, carbon molecular
sieves CMK-1 were prepared from furfuryl alcohol. Into the AlMCM-48
which was prepared by impregnating MCM-48 with aluminum as in Preparation
Example IV, furfuryl alcohol was adsorbed at an amount of 1 g per
g of ALMCM-48 at room temperature, after which furfuryl alcohol
was polymerized at 140.degree. C. for 24 hours in a nitrogen atmosphere.
Then, thermal decomposition was performed at 900.degree. C. in a
vacuum atmosphere, followed by removing the AlMCM-48 silica framework
with an aqueous 1 M NaOH solution and a small amount of ethanol.
CMK-1 thus obtained was analyzed in X-ray diffraction patterns which
are shown in FIG. 6.
EXAMPLE IV
Carbon molecular sieves CMK-1 were prepared from acetylene gas
with an Al-substituted MCM-48 serving as a template. The AlMCM-48
prepared by impregnating MCM-48 with aluminum as in Preparation
Example IV, was treated at 400.degree. C. under vacuum, after which
acetylene gas was sufficiently adsorbed into the AlMCM-48 while
being polymerized. Following the polymerization, thermal decomposition
was carried out at 900.degree. C. under vacuum and the AlMCM-48
silica framework, serving as a template, was removed using an aqueous
1 M NaOH solution and a small amount of ethanol. CMK-1 thus obtained
was analyzed in X-ray diffraction patterns which are shown in FIG.
7.
EXAMPLE V
Carbon molecular sieves CMK-1 different in pore size were prepared
from sucrose with MCM-48 materials of different framework thickness
serving as templates.
To this end, the MCM-48 materials which were prepared and calcined
as described in Preparation Examples I and II were used as templates.
The other procedures necessary for the preparation of CMK-1 were
carried out as in Example I. The sieves CMK-1 were found to be different
in pore size as measured by the BJH method. The results are shown
in FIG. 8.
As described hereinbefore, structurally regular carbon molecular
sieves with uniform pore sizes can be synthesized with mesoporous
molecular sieves serving as templates in accordance with the present
invention. The uniformity in pore size and regularity in structure
make the carbon molecular sieves find numerous applications in catalysts,
adsorbents, carriers, sensors, electrodes, etc.
The present invention has been described in an illustrative manner,
and it is to be understood that the terminology used is intended
to be in the nature of description rather than of limitation. Many
modifications and variations of the present invention are possible
in light of the above teachings. Therefore, it is to be understood
that within the scope of the appended claims, the invention may
be practiced otherwise than as specifically described. |