Molecular sieve abstract
Granular molecular sieve may be obtained, without necessitating
any activng treatment, by subjecting a vinylidene chloride copolymer
to a thermal carbonization treatment for removal of hydrochloric
acid, pulverizing the resultant product to a grain size smaller
than 100 mesh size, adding 15 to 35 parts by weight of a carbonaceous
sintering agent and 8 to 15 parts by weight of an organic pelletizer
capable of gas generation by heating to 100 parts by weight of the
pulverized product, pelletizing the resultant mixture and carbonizing
the resultant pellets at a temperature of 400 to 900.degree. C for
a period of 2 to 6 hours. The pore diameter of this molecular sieve
can be suitably controlled within a range of from 5 to 10 A by appropriately
selecting the sintering agent and pelletizer employed and the conditions
of the thermal treatment.
Molecular sieve claims
What is claimed is:
1. A method of manufacturing carbonaceous granular molecular sieves
having a pore diameter in the range of about 3-10 A comprising the
steps of subjecting a vinylidene chloride copolymer to a thermal
carbonization treatment for removal of hydrogen chloride gas, cooling
and pulverizing the resultant product to a grain size smaller than
100 mesh, admixing per 100 parts of said pulverized product 15 to
35 parts of a carbonaceous sintering agent and 8 to 15 parts of
an organic pelletizing binder generating gas upon heating, pelletizing
the resultant mixture and carbonizing the resultant pellets without
activation at a temperature ranging from 400.degree. C. to 900.degree.
C. for a period ranging from 2 to 6 hours, all parts being by weight.
2. A method according to claim 1 wherein said vinylidene chloride
copolymer is vinylidene chloride-vinyl chloride copolymer.
3. A method according to claim 1 wherein said carbonaceous sintering
agent is coal tar pitch or coking coal.
4. A method according to claim 1 wherein said pelletizer is crystalline
cellulose or sulfite waste liqour.
5. A product obtainable by the method according to claim 1
Molecular sieve description
BACKGROUND OF THE INVENTION
This invention relates to a method of manufacturing carbonaceous
granular molecular sieve. More particularly, the invention relates
to a method of manufacturing carbonaceous granular molecular sieve
from a vinylidene chloride copolymer without necessitating any activating
treatment.
Heretofore, molecular sieves consisting of zeolite have chiefly
been used for the separation and refinement of gases. The zeolite
molecular sieve, however, lacks in chemical resistance and its selective
adsorption capacity deteriorates at high temperatures. Besides the
above, it is also expensive. Therefore, it is not suitable for employment
on an industrial scale.
Molecular sieve materials obtainable by sintering certain carbonaceous
materials followed by activating treatment are also known in the
art. Such carbonaceous molecular sieve, however, is inadequate for
continuous use for a long period of time because of its low mechanical
strength.
The industries dealing with gases have accordingly been calling
for a molecular sieve material, which has sufficient chemical resistance
and mechanical strength while having excellent selective adsorption
capacity with respect to different gases.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of
inexpensively manufacturing a molecular sieve, which has sufficient
chemical resistance and mechanical strength while having excellent
adsorption capacity with respect to different gases.
It is another object of the present invention to provide a method
of manufacturing a molecular sieve having excellent properties from
plastic waste products through a simple process.
It is a further object of the present invention to provide a novel
carbonaceous molecular sieve having pore diameters ranging from
3 to 10 A.
Further objects, features and advantages of the present invention
will become apparent from the following description.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention, a carbonaceous granular molecular sieve
having a high chemical resistance and excellent mechanical strength
at high temperatures can be obtained by subjecting a vinylidene
chloride copolymer to a thermal carbonization treatment for removal
of hydrochloric acid, pulverizing the resultant product to a grain
size smaller than 100 mesh size, adding 15 to 35 parts by weight,
preferably 20 to 30 parts by weight, of a carbonaceous sintering
agent and 8 to 15 parts by weight, preferably 10 to 12 parts by
weight, of an organic pelletizer, which is capable of thermal gas
generation, to 100 parts by weight of the crushed product, pelletizing
the mixture and subjecting the resultant pellets to a thermal carbonization
treatment at a temperature of 400.degree. to 900.degree. C. for
a period of 2 to 6 hours.
In accordance with the present invention, as the vinylidene chloride,
a copolymer of vinylidene chloride and vinyl chloride and also copolymers
of vinylidene chloride and olefins may be used and the vinylidene
chloride content of the copolymer is preferably within a range of
from 40 to 95 percent by weight. It is possible to use, as the vinylidene
chloride copolymer, recovered waste products of plastics, for example,
that of Saran (Tradename of Dow Chemical Co., U.S.A.).
This vinylidene chloride copolymer is first thermally carbonized
at a temperature of 500.degree. to 700.degree. C. for 1 to 5 hours
and then cooled and pulverized to a grain size smaller than 100
mesh size.
As the carbonaceous sintering agent, a carbonaceous material, derived
from petroleum or coal and capable of being fused to exhibit viscosity
when heated, for instance coal tar pitch, asphalt and caking coal,
may be used. It is also pulverized to a grain size smaller than
100 mesh size for use. As the organic pelletizer, a tenacious organic
substance, which can be partially gasified when heated with the
remaining ungasified portion becoming carbonized, for example, crystalline
cellulose solution, waste treacle, sulfite waste liquor, etc., may
be used.
The sintering agent and pelletizer are added within respective
ranges of 15 to 35 percent by weight and 8 to 15 percent by weight
with respect to the vinylidene chloride copolymer product powder
with hydrochloric acid removed therefrom. If the proportion of the
sintering agent is less than 15 weight percent, the mechanical strength
of the resultant molecular sieve will be extremely reduced. On the
other hand, if the proportion is greater than 35 weight percent,
resultant pellets will adhere to one another at the time of the
subsequent carbonization so that the uniformity of quality of the
product will be lost. If the proportion of the pelletizer is less
than 8 weight percent, the resultant pellets will display low mechanical
strength at normal temperature, so that they will tend to collapse
and become finer particles at the time of carbonization treatment.
On the other hand, with a proportion greater than 15 weight percent,
such inconvenience as difficulty to pelletize to a given grain size
or adhesion to the pelletizer during the pelletizing step would
be encountered. Generally, with the increase of the quantity of
the pelletizer, the pore diameter of the resultant molecular sieve
is increased while the mechanical strength thereof is reduced.
In the method according to the present invention, the mixture of
the hydrochloric acid removal treatment product powder of vinylidene
chloride copolymer, sintering agent and pelletizer is pelletized,
for example, into pellets with a diameter of 2 millimeters and a
thickness of 0.5 to 1 millimeter, followed by thermal carbonization
in a carbonizing furnace at a temperature ranging from 400 to 900.degree.
C. for a period of 2 to 6 hours. If the carbonizing temperature
at this time is lower then 400.degree. C., sufficient gasification
of the pelletizer contained in the pellets will not be obtained,
so that neither perfect microporous structure nor sufficient mechanical
strength can be obtained. On the other hand, increasing the carbonizing
temperature over 900.degree. C. will not lead to any added advantage
with respect to the properties of the resultant molecular sieve,
but it will merely lead to an increase in the equipment costs. If
the carbonizing period is shorter than 2 hours, the gasifying effect
of the sintering agent and pelletizer is again insufficient, so
that the development of the microporous structure of the pellets
will be insufficient. Also, the congealing effect is insufficient,
so that the mechanical strength of the product will be low. Extending
the carbonizing period in excess of 6 hours, on the other hand,
will not lead to any pronounced effect. The carbonizing period may
be suitably curtailed by appropriately increasing the carbonizing
temperature. Generally, within the range of 400.degree. to 900.degree.
C., the lower the carbonizing temperature, the smaller the pore
diameter of the molecular sieve and by increasing the carbonizing
temperature, a molecular sieve having increased pore diameter may
be obtained.
It will be appreciated that according to the present invention,
it is possible to control the pore diameter of the molecular sieve,
practically within a range of from 5 to 10 A, by appropriately selecting
the sintering agent and pelletizer and the conditions for thermally
treating the pellets.
In the step of carbonizing the pellets according to the present
invention, the sintering agent and pelletizer contained in the pellets
are thought to provide congealing effect as well as gas generation
effect for the formation of the microporous structure of the pellets.
The molecular sieve obtainable according to the present invention,
unlike the prior art carbonaceous molecular sieve, requires no subsequent
activating treatment and can be used in situ.
The present invention will be understood more readily by reference
to the following examples, which, however, are intended to illustrate
the invention and should not be construed as limiting the scope
of the invention. |