Molecular sieve abstract
The present invention relates to a manufacturing method of molecular
sieve compound and in particular, to a manufacturing method whereas
crystalline aluminosilicate salt is formed in the pores of activated
carbon and thereby possessing both hydrophilic and hydrophobic adsorption
capacity, therefore the molecular sieve compound manufactured according
to this present invention is in use for treatment agent of wastewater,
deodorizing agent, antibacterial and disinfectant agent, adsorbent
of organic matter and water, removal agent of harmful gas of cigarette,
separable agent of air and many other applications.
Molecular sieve claims
What is claimed is:
1. A manufacturing method of granulated complex molecular sieve
compound having multi-functional adsorption capacity, which is characterized
in comprising:
(a) manufacturing sodium aluminate aqueous solution by reacting
sodium hydroxide and a substance containing alumina;
(b) manufacturing sodium silicate composition by reacting sodium
hydroxide and a substance containing silica;
(c) gelling by said sodium aluminate aqueous solution and sodium
silicate composition by homogeneously mixing to form a gel composition
mole ratio of SiO.sub.2 /Al.sub.2 O.sub.3 is 2.0.about.40.0;
(d) depositing said gel composition into the pores of activated
carbon; and
(e) aging and crystallizing the deposited gel composition.
2. The manufacturing method according to claim 1 wherein the substance
containing alumina in (a) step is selected from the group consisting
of sodium aluminate(NaAlO.sub.2), aluminum nitrate(Al(NO.sub.3).sub.3.9H.sub.2
O), aluminum sulfate(Al.sub.2 (SO.sub.4).sub.3.18H.sub.2 O), aluminum
chloride(AlCl.sub.3.6H.sub.2 O), aluminum hydroxide(Al(OH).sub.3),
aluminum alkoxide and alumina gel.
3. The manufacturing method according to claim 1 wherein the substance
containing silica in (b) step is selected from the group consisting
of colloidal silica, fumed silica, water glass and silica gel.
4. The manufacturing method according to claim 1 wherein said
mole ratio of SiO.sub.2 /Al.sub.2 O.sub.3 in (c) step is 2.about.15.
5. The manufacturing method according to claim 1 wherein said
activated carbon in (d) step is 20.about.70 wt % of said gel composition.
6. The complex molecular sieve compound manufactured by method
according to anyone of claims 1 to 5 in which zeolite of A, X or
Y type is firmly linked in the pores of activated carbon.
Molecular sieve description
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a manufacturing method of molecular
sieve compound and in particular, to a manufacturing method whereas
crystalline aluminosilicate salt is formed in the pores of activated
carbon and thereby possessing both hydrophilic and hydrophobic adsorption
capacity, therefore the molecular sieve compound manufactured according
to this present invention is in use as treatment agent of wastewater,
deodorizing agent, antibacterial and disinfectant agent, adsorbent
of organic matter and water, removal agent of harmful gas of cigarette,
separable agent of air and many other application.
2. Description of the Prior Art
Crystalline aluminosilicate salt(also called `zeolite`) have the
following formula (I)
wherein,
M is cation,
n is cation valence,
x, y are the constants depending upon the structure of zeolite.
Generally, zeolite has pore diameter of range 3.about.10 .ANG.
and thus act as molecular sieving effect. Especially as a hydrophilic
adsorbent, zeolite has a strong adsorption power for polar molecules
like water and this adsorption power is very large even under low
partial pressure and high temperature. As adsorption capacity mentioned
above, zeolite is widely applied in adsorbent, catalyst, catalyst
carrier, molecular sieve, detergent addition agent and many other
fields.
Up to the present, many scientists are engaged in research to synthesize
zeolites. The synthesis processes generally require organic materials,
alcohols and acids in the crystallization of aluminosilicate salt
by hydrothermal reaction. This method results in various contamination
by adding above materials and has shortcoming such as the control
of mole ratio of silica to alumina. Furthermore reaction involves
conversion of gel phase into slurry phase which results in formation
of material with to several to several scores .mu.m of average diameter
requiring filtration step to isolate proper size of particles followed
by washing and spray drying to get final product. And in order to
use for adsorption or catalyst process, an intricate sequence of
process to granulate has to be followed.
Activated carbon is manufactured by carbonization of coconut husk,
coal, wood and polymer fiber followed by activation under reduction
condition. The activated carbon thus produced could be granular,
fragment, powder or fibrous type with pore diameter of several to
several hundreds .ANG.. Activated carbon is hydrophobic adsorbent
with strong adsorption power for non-polar molecules and its specific
surface area can be attained till more than 1200 m.sup.2 /g. Due
to these novel properties, activated carbon is widely used as adsorbent
for purification, food industry, deodorizing agent, decoloring agent,
treatment agent of waste water, air clean agent and also catalyst
carrier.
And recently, many researches to combine adsorption capacity of
activated carbon and zeolite are being conducted. For instance,
Japanese non-examination patent sho 54-53669 discloses a manufacturing
method of adsorbent having multi-functions by adding organic and
inorganic binder to mixture of zeolite and activated carbon.
Korean patent application No. 94-18327 by this applicant is reported
a manufacturing method of molecular sieve which zeolite is added
to activated carbon and the material to be carbonized in plasticity.
But as previously mentioned, conventional methods are difficult
in controlling by powder mixing and have to granulate using appropriate
binder.
To overcome said problem in prior art, the inventors report development
of
a new manufacturing method wherein zeolite is directly crystallized
in the pores of activated carbon.
SUMMARY OF THE INVENTION
The objective of this invention is to provide a manufacturing method
for molecular sieve compound having large adsorption power for both
hydrophilic and hydrophobic adsorption capacity.
In accordance with this invention, silica tetrahedron or alumina
tetrahedron produced in alkaline aqueous solution is allowed to
deposit into the pores of activated carbon by various mole ratio,
silica and alumina components contact with alkali reactive mother
liquor and promote seeding of the crystals in activated carobon
pores. So complex molecular sieve compound with fine zeolite crystalline
in the pores of activated carbon is produced as follows.
DESCRIPTION OF THE DRAWINGS
The invention will be described in greater details in the drawings.
FIG. 1 is a Scanning Electron Micrograph showing distribution of
zeolite in the pores of activated carbon produced according to Example
1.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to a manufacturing method of molecular sieve
compound having multi-functional adsorption capacity, which is characterized
in comprising:
(a) Manufacturing sodium aluminate aqueous solution by reacting
sodium hydroxide and the substance of alumina;
(b) Manufacturing sodium silicate composition by reacting sodium
hydroxide and the substance of silica;
(c) Gelation by homogeneous mixing said sodium aluminate aqueous
solution and sodium silicate composition;
(d) Deposition of gel composition into the pores of activated carbon;
and
(e) Aging and crystallization.
More detailed description of this invention is as follows.
This invention relates to manufacturing method of multi-functional
molecular sieve compound which is the 3-dimensional zeolite having
homogeneous pore and channel. Said zeolite is produced by crosslinking
oxygen with silica tetrahedron and alumina tetrahedron in alkali
aqueous solution in the pores of activated carbon.
The activated carbon is used as supporter because of high adsorption
capacity due to the presence of various size of pores. So if gel
phase composition is settled at time of zeolite synthesis, silica
tetrahedron or alumina tetrahedron deposits into the pores of activated
carbon and mole ratio of silica(SiO.sub.4) vs alumina(Al.sub.2 O.sub.3)
can be freely controlled in this processing.
Furthermore, silica and alumina components thus reaching activated
carbon in contact with mother liquor and promote seeding action,
thereby fine zeolite crystalline can be firmly produced in the pores
of activate carbon.
In synthesis of crystalline aluminosilicate according to the present
invention, sodium hydroxide is used for the substance of alkaline.
Sodium aluminate(NaAlO.sub.2), aluminum nitrate(Al(NO.sub.3).sub.3.9H.sub.2
O), aluminum sulfate(Al.sub.2 (SO.sub.4).sub.3.18H.sub.2 O), aluminum
chloride(AlCl.sub.3.6H.sub.2 O), aluminum hydroxide (Al(OH).sub.3),
aluminum alkoxide and alumina gel etc. can be used as the substance
of alumina. Colloidal silica, fumed silica, water glass(sodium silicate
aqueous solution), silica gel etc. can be used as the substance
of silica.
The factors affecting crystallization of aluminosilicate are the
substance of silica, mole ratio of silica vs alumina, pH, reaction
temperature, reaction time, degree of aging in room temperature,
presence of stirring etc. The morphology and nature of zeolite produced
are directly linked to these variation.
Among the these factor, taking example of the substance of silica;
if size of silica particles becomes larger, the reactivity of the
complex reduces while stable state is reached. The particle size
of silica is affected by kinetics of hydroylsis or condensation
under the alkali condition. So it is very important factor in crystalline
reaction.
Generally if particle size of silica is greater than 100 .mu.m,
crystalline reaction is very slow and amorphous gel is formed. On
the other hand, if particle size of silica is very small, it is
converted into other phases(quartz, cristobalite, keatite) which
is very sensitive to surrounding environment.
The factor to affect crystalline reaction of zeolite is mole ratio
of silica/alumina, which is important factor to decide morphology
of zeolite, such as zeolite of A, X, Y type, in case zeolite of
P type or anlacime.
The other factor is pH. Because silica particle is very stable
particle, the formation of nucleation of zeolite must be performed
under strong base condition. As silica particles having low reactivity
are readily dissolved under the alkali condition, they have high
reactivity and easily formed nucleus.
Finally, reaction temperature and reaction time are interdependent.
As reaction time becomes longer, unstable crystals among already
produced crystals are ressolved in strong alkali solution and the
phase transition occurs.
A manufacturing method of molecular sieve compound according to
the present invention is as follows.
A suitable sodium aluminate solution is made by adding the substance
of alumina to sodium hydroxide solution and stirring for 20.about.60
minutes at 70.about.120.degree. C. to dissolve completely. Concentration
of sodium hydroxide in solution is 20.about.50 wt %, especially
30.about.40 wt %. Sodium silicate composition is produced by sufficiently
stirring at 25.about.70.degree. C. the sodium hydroxide solution
and the substance of silica.
Furthermore, sodium aluminate solution and sodium silicate composition
are mixed in ratios up to SiO.sub.2 /Al.sub.2 O.sub.3 =2.0.about.40.0
mole ratio, Na.sub.2 O/SiO.sub.2 =0.4.about.2.0 mole ratio, H.sub.2
O/Na.sub.2 O=15.0.about.70.0 mole ratio and gelation is brought
about homogeneously mixed using stirring machine.
Following gelation, gel composition is allowed to deposit into
the pores of activated carbon by adding activated carbon of 20.about.70
wt % and reducing pressure. In the above process, if mole ratio
of SiO.sub.2 /Al.sub.2 O.sub.3 is under 2.0 alumina component remains
in final product and if mole ratio is greater than 40 crystallization
of zeolite from reactant becomes difficult.
Beside, if mole ratio of Na.sub.2 O/SiO.sub.2 is under 0.4 activity
of silica component is difficult, it is slowly converted into zeolite.
If mole ratio is more than 2.0 crystalline aluminosilicate having
very low activity like hydroxy sodalite or analcime is produced.
If mole ratio of H.sub.2 O/Na.sub.2 O is under 15 alkalinity in
solution is so high that side reactions easily occur. If more than
70.0 then high pressure and temperature are required for the synthesis
reaction.
On the other hand if activated carbon is added under 20 wt % in
reaction, the component to be converted into zeolite is so excessive
that the zeolite particles condensed at the outside of the pores
of activated carbon exist and side products of slurry phase are
produced in excess. If activated carbon in reaction is more than
70 wt %, then gel component fails to homogeneously deposit into
the pores of activated carbon and a heterogeneous product is produced.
The reaction mixture is allowed to age for 2.about.96 hours at
25.about.60.degree. C. and crystallized at 70.about.120.degree.
C., especially it is appropriate to crystallize at 90.about.100.degree.
C. for 2.about.24 hours.
Upon completion of crstallization, the side product of slurry phase
is separated and final product washed with water, and dried for
4.about.12 hours at 100.about.120.degree. C. in dryer to provide
molecular sieve compound.
To evaluate structure and physical property of molecular sieve
compound manufactured in this method, X-ray diffraction (XRD), the
pore structure by SEM, the pore volume by mercury penetration, the
content of zeolite produced in the pores of activated carbon, the
specific surface area by BET method, the adsorption capacity of
moisture, the adsorption capacity of ammonia and the adsorption
capacity of iodine were measured.
The complex molecular sieve compounds produced by this invention
have zeolite of A, X, or Y type finely distributed into the pores
of activated carbon. Therefore the compounds have both hydrophilic
and hydrophobic adsorption power having properties of activated
carbon and zeolite. Because these unique properties, these compounds
use as treatment agent of water purification, deodorizing agent,
antibacterial and disinfectant agent, adsorbent of organic matter,
adsorbent of moisture, reagent of harmful gas of cigarette, separable
agent of air etc. and wide uses.
The present invention is represented in detail by the examples
below, which aren't intended to be exemplary only. |