Molecular sieve abstract
The present invention relates to a manufacturing method of granulated
complex molecular sieve composition having multifunction and useful
for removal agent of harmful gas of cigarette or treatment agent
of water purification etc. as having multifunctioned adsorption
capacity and excellent anti-abrasion property, and convenient process,
in particular, to a manufacturing method which is comprised of granulating
by mixing alkali metal silicate aqueous solution to mixture of zeolites
of various types and active carbon and treating it with water solution
of alkali earth metal salt without calcination, and drying.
Molecular sieve claims
What is claimed is:
1. A method of manufacturing a granulated complex molecular sieve
composition having multi-functions, said method comprising the steps
of:
spray-adding an alkali metal silicate aqueous solution to a mixture
of zeolite and active carbon powder,
granulating the aqueous solution containing mixture, treating the
granulated aqueous solution containing mixture with an alkali earth
metal salt aqueous solution, and drying.
2. The method according to claim 1 wherein said zeolite is 4A
type.
3. The method according to claim 1 wherein said alkali metal silicate
aqueous solution contains 15 to 38 wt % of sodium silicate.
4. The method according to claim 1 wherein said alkali earth metal
salt aqueous solution contains 10 to 45 wt % of calcium chloride.
Molecular sieve description
FIELD OF THE INVENTION
The present invention relates to a method of manufacturing granulated
complex molecular sieve compositions having multi-functions, which
can be used, for example, to remove harmful gases that are emitted
from cigarettes or as a treatment agent in water purification. The
present molecular sieve compositions also have a multi-adsorption
capacity, an excellent anti-abrasion property and can be conveniently
processed. In particular, the inventive method comprises granulating
an alkali metal silicate aqueous solution with a mixture of zeolites
of various types and active carbon powder, and treating the mixture
with an aqueous solution of
alkali earth metal salt without calcination and drying.
DESCRIPTION OF THE RELATED ART
Zeolite is a crystalline alumino silicate salt generally represented
by the following formula (I).
wherein, M is a cation,
n is the cation valence,
w is the number of water molecules.
The rate of y/x usually has values of 1.about.5 depending upon
the structure.
The minute pore diameter of approximately 3 to 10 .ANG., that is
characteristic of most zeolites, results in molecular sieving properties.
Zeolites are especially useful as a hydrophilic adsorbent, because
they have a strong adsorption capacity with polar molecules such
as water. In addition, their adsorption capacity is great even under
low partial pressures and at high temperatures.
An active carbon is manufactured by a method comprising the carbonization
of materials that include coconut husk, coal or wood. Activation
is then carried out under a reduction atmosphere. The resulting
active carbon has a granule, fragment or powder morphology, and
a pore diameter of 1 to 100 nm, with most pores being below 2 nm.
Active carbon is a hydrophobic adsorbent and has strong adsorption
power with non-polar molecule. The specific surface area of the
active carbon may exceed 1200 m.sup.2 /g.
To assist in the adsorption capacity of the hydrophilic adsorbent
of zeolite and the hydrophobic adsorbent active carbon, methods
of manufacturing such adsorbents having multi-functions have been
recently reported. These methods include mixing zeolite and active
carbon, combining active carbonization substance and substance of
zeolite type, and mixing a silicate compound and active carbon.
For example, Japanese non-examination patent sho 54-53669 discloses
a method of manufacturing a composition for ozon degradation by
adding bentonite and sugar to a mixture of zeolite and active carbon,
which is then formed, dried and calcined. This method uses a natural
clay such as bentonite as an inorganic binder. Consequently, the
final product includes adulterated impurities. In addition, because
the natural clay binder is a water-insoluble compound, its plasticity
becomes low when it is mixed with water. To form a desired pattern,
therefore, its plasticity must be maintained by adding water-soluble
compounds such as polymers as an organic binder. Furthermore, due
to the swelling of bentonite in water, the composition readily dissolves
in water. To prevent the composition from dissolving and to carbonize
sugar as an organic binder, a drying process and a calcination process
under reduction atmosphere is required.
Therefore, this method needs complex calcination equipment which
results in enormous costs. This method also produces dust, because
of the contraction of bentonite during calcination, which leads
to a decrease in the anti-abrasion capability and in the adsorption
capability (because of the decrease in specific surface area) of
the product. Use of an organic binder also necessarily results in
contamination to the atmosphere from the volatile oils that are
produced during the carbonization of the organic binder. Accordingly,
this method requires a system to remove such contaminative substances.
Japanese non-examination Patent Pyong 4-4039 discloses a method
of manufacturing a wastewater treatment agent using oil-adsorption
capability by adding blast furnace slag powder to zeolite. This
method gives rise to ecological safety problem of using the blast
furnace slag component. Also, the bad plasticity associated with
using the slag component makes the granulation process difficult.
Moreover, the resulting product's hydrophobic adsorption capability
is low.
Japanese non-examination patent sho 59-69146 discloses a method
of manufacturing an adsorbent of filter phase by adding bentonite
and silicate compounds to active carbon. This method has a problem
with the pore of active carbon becoming plugged by the bentonite
and silicate compounds, which results in a low hydrophilic adsorption
capability for the molecular sieve.
To overcome the problems of the above prior art, the inventors
have developed a product having improved plasticity and anti-abrasion
capabilities. This improved product was initially made by adding
alkali earth metal silicate as an inorganic binder and molasses
as organic binder to a mixture of zeolite and active carbon. See,
Korean patent application 94-18327. However, this process also required
a calcination step, which lead to the previously described problems,
i.e., limitations in improvement of adsorption capability and specific
surface area.
Therefore, the inventors attempted to solve the problems described
in the prior art by using a method that did not require high temperature
calcination. As a result, the inventors developed a method comprising
(a) manufacturing a granulated composition by adding an alkali metal
silicate aqueous solution having good plasticity to a mixture of
zeolite and active carbon, (b) and adding the composition directly
to an alkali earth metal salt aqueous solution without drying or
calcinating.
The inventors have discovered that the water-soluble alkali metal
silicate is converted into water-insoluble alkali earth metal silicate,
even without separately using an organic binder. Therefore, anti-abrasion
capability of the granulated composition increases without the composition
dissolving in water. The use of the inorganic binder also increases
adsorption capability. Moreover, because zeolite contained in the
granulated compositions is converted into zeolite of alkali earth
metal type, the specific surface area of the granulated compositions
is also greatly improved.
The objection of the present invention is to provide a method of
manufacturing a granulated complex molecular sieve composition having
multi-functions, such as the adsorption of water and organic solvent,
or the separation of substances.
SUMMARY OF THE INVENTION
The present invention relates to a method of manufacturing a granulated
complex molecular sieve composition which comprises the steps of
adding alkali metal silicate aqueous solution to a mixture of zeolite
and active carbon powder. The mixture is then granulated and soaked
with an alkali earth metal salt aqueous solution. The following
is a more detailed description of the invention.
This invention relates to a method of manufacturing a granulated
complex molecular sieve composition having various adsorption capability
by developing micropores.
Zeolite powder of A type and active carbon powder is first added
together, and then placed in a plowshare mixer where it is sufficiently
mixed. An alkali metal silicate aqueous solution is then sprayed
on the zeolite and active carbon, mixed and granulated to a size
of 0.2 to 5 nm. Besides zeolite of A type, other zeolites that can
be used include X, Y, or ZSM type or natural zeolite.
In this invention, the active carbon is manufactured from coconut
husk, and it is a powder type having a specific surface area of
greater than 100 m.sup.2 /g. An active carbon of lignite series,
soft coal series, or wood type can also be used.
As the alkali metal silicate aqueous solution, sodium silicate
aqueous solution or potassium silicate aqueous solution is used.
When sodium silicate aqueous solution is used, the aqueous solution
contains 15 to 38 wt % of sodium silicate. In addition to a plowshare
mixer, other granulation equipment that can be used includes a rotating
granulator, an extruder, a fluidized bed granulator or a tablet
press.
When the granulated composition is added to an alkali earth metal
salt aqueous solution, the alkali metal silicate component, which
acts as a binder, is converted into alkali earth metal silicate.
For example, zeolite of 4A type is simultaneously converted into
zeolite of alkali earth metal A type. The granulated complex molecular
sieve composition of the present invention is produced by removing
the liquid component of the solution by drying with a fluidized
bed dryer. As the alkali earth metal aqueous solution, the present
invention can utilize calcium chloride(CaCl.sub.2) aqueous solution
or magnesium chloride(MgCl.sub.2) aqueous solution. When calcium
chloride aqueous solution is used, the aqueous solution contains
10 to 45 wt % of calcium chloride. The detailed chemical reactions
that occur in zeolite and silicate when the granulation composition
is treated with alkali earth metal salt, e.g., CaCl.sub.2 are as
follows: ##STR1##
As mentioned above, this invention has the advantage that the pretreatment
process in which zeolite powder is converted into alkali earth metal
zeolite powder is not required. In other words, by using water-insoluble
alkali earth metal silicate in the inventive process, binding power
and water resistant property of the granulated composition is greatly
improved, without the need for high temperature calcination.
The granulated complex molecular sieve composition manufactured
according to the present invention is composed of 20 to 60 wt %
of zeolite, 15 to 50 wt % of active carbon and 10 to 35 wt % of
alkali earth metal silicate, as solid components. When the content
of these components are above or below these ranges, it is difficult
to have desired hydrophobic/hydrophilic adsorption capability and
to manufacture a granulated composition having the desired anti-abrasion
capability. Also, when the components are outside these ranges adsorption
capability is decreased because of the severe plugging of the micropores
by the adsorbent.
The properties associated with the granulated composition include
a specific surface area greater than 500m.sup.2 /g, an iodine adsorption
power greater than 320 mg/g, a decoloration power of methylene blue
greater than 65 mg/g, and an anti-abrasion capability greater than
99.5%. Consequently, the granulated composition of this invention
has excellent plasticity and anti-abrasion capability, without the
need for a calcination step. In addition, the adsorption capability
of the composition is not adversely affected by the presence of
an organic binder.
The granulated composition is useful for adsorption of water, organic
solvents and poisonous gas. The composition can also be used in
the treatment of service water and sewage and for the separation
of substances using the molecular sieve properties of the composition.
In particular, the inventive composition can be used as a treatment
agent for water purification or air purification, a deodorization
agent or as a catalyst and support for adsorbents. The present invention
is represented by the Examples below, which are intended to be exemplary
only. |