U.S. patent application number 14/356074 was filed with the patent office on 2014-09-25 for co2 desorption catalyst.
This patent application is currently assigned to THE KANSAI ELECTRIC POWER CO., INC.. The applicant listed for this patent is THE KANSAI ELECTRIC POWER CO., INC.. Invention is credited to Hiroshi Deguchi, Tsunenori Watanabe, Yasuyuki Yagi.
Application Number | 20140284521 14/356074 |
Document ID | / |
Family ID | 48535348 |
Filed Date | 2014-09-25 |
United States Patent
Application |
20140284521 |
Kind Code |
A1 |
Deguchi; Hiroshi ; et
al. |
September 25, 2014 |
CO2 DESORPTION CATALYST
Abstract
This invention provides a CO.sub.2 desorption catalyst that has
an excellent CO.sub.2 desorption activity and that can be used to
replace metal filler. This invention provides a CO.sub.2 desorption
catalyst comprising an inorganic powder or inorganic powder
compact, the inorganic powder or inorganic powder compact having a
BET specific surface area of 7 m.sup.2/g or m
Inventors: |
Deguchi; Hiroshi;
(Amagasaki-shi, JP) ; Watanabe; Tsunenori;
(Amagasaki-shi, JP) ; Yagi; Yasuyuki;
(Amagasaki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
THE KANSAI ELECTRIC POWER CO., INC. |
Osaka-shi, Osaka |
|
JP |
|
|
Assignee: |
THE KANSAI ELECTRIC POWER CO.,
INC.
Osaka-shi, Osaka
JP
|
Family ID: |
48535348 |
Appl. No.: |
14/356074 |
Filed: |
November 22, 2012 |
PCT Filed: |
November 22, 2012 |
PCT NO: |
PCT/JP2012/080340 |
371 Date: |
May 2, 2014 |
Current U.S.
Class: |
252/190 ;
422/168; 428/402; 502/200; 502/300; 502/319; 502/343; 502/355;
502/60 |
Current CPC
Class: |
B01J 23/26 20130101;
B01J 2229/42 20130101; B01D 2252/20478 20130101; B01J 23/44
20130101; B01J 27/24 20130101; B01J 23/75 20130101; Y10T 428/2982
20150115; B01D 2257/504 20130101; B01D 53/96 20130101; B01J 29/06
20130101; Y02C 10/06 20130101; B01D 2255/20753 20130101; B01D
2255/104 20130101; B01D 2255/20738 20130101; B01J 23/755 20130101;
B01D 2255/1021 20130101; B01J 29/072 20130101; B01D 2255/1023
20130101; B01D 53/1425 20130101; B01J 23/50 20130101; B01D 2255/30
20130101; B01J 21/04 20130101; B01J 23/80 20130101; B01D 2255/20746
20130101; B01D 2255/2092 20130101; B01J 23/745 20130101; B01D
53/1475 20130101; B01J 29/068 20130101; Y02C 20/40 20200801; B01J
29/061 20130101; B01D 2255/9207 20130101 |
Class at
Publication: |
252/190 ;
502/200; 502/343; 502/319; 502/60; 502/355; 502/300; 422/168;
428/402 |
International
Class: |
B01J 29/06 20060101
B01J029/06; B01D 53/96 20060101 B01D053/96; B01J 23/26 20060101
B01J023/26; B01J 21/04 20060101 B01J021/04; B01J 27/24 20060101
B01J027/24; B01J 23/80 20060101 B01J023/80 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 29, 2011 |
JP |
2011-260742 |
Claims
1.-10. (canceled)
11. A CO.sub.2 desorption catalyst comprising an inorganic powder
or inorganic powder compact, the inorganic powder or inorganic
powder compact having a BET specific surface area of 7 m.sup.2/g or
more.
12. The CO.sub.2 desorption catalyst according to claim 11, wherein
the inorganic powder or inorganic powder compact is at least one
member selected from the group consisting of BN, metal oxides,
metals, and clay minerals.
13. The CO.sub.2 desorption catalyst according to claim 11, wherein
the inorganic powder or inorganic powder compact is at least one
member selected from the group consisting of BN, Ga.sub.2O.sub.3,
Al.sub.2O.sub.3, SiO.sub.2, CuO, ZnO, Pd, Fe, Co, Ag, Ni, Pt, Cr,
and zeolites.
14. The CO.sub.2 desorption catalyst according to claim 11, wherein
the inorganic powder or inorganic powder compact is at least one
member selected from the group consisting of BN, Ga.sub.2O.sub.3,
Al.sub.2O.sub.3, Pd, Fe, and zeolites.
15. The CO.sub.2 desorption catalyst according to claims 11,
wherein the inorganic powder or inorganic powder compact is at
least one member selected from the group consisting of BN and
Al.sub.2O.sub.3.
16. The CO.sub.2 desorption catalyst according to claim 15, wherein
at least one metal selected from the group consisting of Pd, Fe,
Co, Ag, Ni, and Pt is supported on the catalyst.
17. A CO.sub.2 desorption device including: a CO.sub.2 absorption
tower for absorbing and removing CO.sub.2 from exhaust gas by using
an absorbing solution; and a regeneration tower for regenerating
the absorbing solution containing absorbed CO.sub.2, wherein the
regeneration tower contains the CO.sub.2 desorption catalyst of
claim 11.
18. A method for desorbing CO.sub.2, the method comprising the step
of regenerating an absorbing solution containing absorbed CO.sub.2,
wherein the regeneration step brings the absorbing solution
containing absorbed CO.sub.2 into contact with the CO.sub.2
desorption catalyst of claim 11.
19. Use of an inorganic powder or inorganic powder compact having a
BET specific surface area of 7 m.sup.2/g or more, as a catalyst for
desorbing CO.sub.2.
20. A method for using an inorganic powder or inorganic powder
compact having a BET specific surface area of 7 m.sup.2/g or more,
as a catalyst for desorbing CO.sub.2.
Description
TECHNICAL FIELD
[0001] This invention relates to a CO.sub.2 desorption
catalyst.
BACKGROUND ART
[0002] Chemical absorption methods are widely known as a method for
removing and collecting CO.sub.2 from combustion exhaust gas from
thermal power stations and steel works (PTL 1). In a chemical
absorption method, CO.sub.2 is brought into contact with an aqueous
solution mainly containing alkanolamine (hereinafter also referred
to as an "absorbing solution") in an absorption tower, so as to
allow the CO.sub.2 to be absorbed into the absorbing solution. The
absorbing solution containing the absorbed CO.sub.2 is transferred
to a regeneration tower where the transferred solution is heated by
heating vapor to cause the absorbed CO.sub.2 to be desorbed
(degassed). The desorbed CO.sub.2 is collected, and the absorbing
solution from which the CO.sub.2 has been desorbed is transferred
back to the absorption tower to be reused.
[0003] Heretofore, the regeneration tower is filled with metal
filler, such as thin stainless-steel plates or mesh balls obtained
by wadding stainless steel mesh. The contact area of the absorbing
solution and heating vapor is increased by allowing the absorbing
solution to move through the surface of the filler. In this manner,
desorption of CO.sub.2 is promoted.
CITATION LIST
Patent Literature
PTL 1: JPH03-193116A
SUMMARY OF INVENTION
Technical Problem
[0004] However, the metal filler heretofore used exerts limited
activity on the promotion of desorption. Further, the filler
heretofore used generally occupies a large volume of space, and the
regeneration tower must therefore be made larger to achieve the
desired desorption amount.
[0005] For this reason, the development of CO.sub.2 desorption
catalysts that have an excellent CO.sub.2 desorption activity and
that can be used to replace the metal filler is in demand.
[0006] An object of the invention is to provide a CO.sub.2
desorption catalyst having excellent CO.sub.2 desorption
activity.
Solution to Problem
[0007] As a result of extensive research, the present inventors
found that the use of a specific inorganic powder or inorganic
powder compact makes it possible to provide the above CO.sub.2
desorption catalyst having excellent CO.sub.2 desorption activity.
The invention has thereby been accomplished.
[0008] Specifically, as described below, the invention relates to a
CO.sub.2 desorption catalyst, a CO.sub.2 desorption device having
this catalyst, and a method for desorbing CO.sub.2 by using this
catalyst.
[0009] 1. A CO.sub.2 desorption catalyst comprising an inorganic
powder or inorganic powder compact,
[0010] the inorganic powder or inorganic powder compact having a
BET specific surface area of 7 m.sup.2/g or more.
[0011] 2. The CO.sub.2 desorption catalyst according to Item 1,
wherein the inorganic powder or inorganic powder compact is at
least one member selected from the group consisting of BN, metal
oxides, metals, and clay minerals.
[0012] 3. The CO.sub.2 desorption catalyst according to Item 1 or
2, wherein the inorganic powder or inorganic powder compact is at
least one member selected from the group consisting of BN,
Ga.sub.2O.sub.3, Al.sub.2O.sub.3, SiO.sub.2, CuO, ZnO, Pd, Fe, Co,
Ag, Ni, Pt, Cr, and zeolites.
[0013] 4. The CO.sub.2 desorption catalyst according to one of
Items 1 to 3, wherein the inorganic powder or inorganic powder
compact is at least one member selected from the group consisting
of BN, Ga.sub.2O.sub.3, Al.sub.2O.sub.3, Pd, Fe, and zeolites.
[0014] 5. The CO.sub.2 desorption catalyst according to one of
Items 1 to 4, wherein the inorganic powder or inorganic powder
compact is at least one member selected from the group consisting
of EN and Al.sub.2O.sub.3.
[0015] 6. The CO.sub.2 desorption catalyst according to Item 5,
wherein at least one metal selected from the group consisting of
Pd, Fe, Co, Ag, Ni, and Pt is supported on the catalyst.
[0016] 7. A CO.sub.2 desorption device including:
[0017] a CO.sub.2 absorption tower for absorbing and removing
CO.sub.2 from exhaust gas by using an absorbing solution; and
[0018] a regeneration tower for regenerating the absorbing solution
containing absorbed CO.sub.2,
[0019] wherein the regeneration tower contains the CO.sub.2
desorption catalyst of any one of Items 1 to 6.
[0020] 8. A method for desorbing CO.sub.2,
[0021] the method comprising the step of regenerating an absorbing
solution containing absorbed CO.sub.2,
[0022] wherein the regeneration step brings the absorbing solution
containing absorbed CO.sub.2 into contact with the CO.sub.2
desorption catalyst of any one of Items 1 to 6.
[0023] 9. Use of an inorganic powder or inorganic powder compact
having a BET specific surface area of 7 m.sup.2/g or more, as a
catalyst for desorbing CO.sub.2.
[0024] 10. A method for using an inorganic powder or inorganic
powder compact having a BET specific surface area of 7 m.sup.2/g or
more, as a catalyst for desorbing CO.sub.2.
[0025] The CO.sub.2 desorption catalyst of the invention is
described below in detail. The invention also encompasses the use
of an inorganic powder or inorganic powder compact having a BET
specific surface area of 7 m.sup.2/g or more, as a catalyst for
desorbing CO.sub.2 from a CO.sub.2-containing solution. The
invention further encompasses a method for using an inorganic
powder or inorganic powder compact having a BET specific surface
area of 7 m.sup.2/g or more, as a catalyst for desorbing CO.sub.2
from a CO.sub.2-containing solution.
CO.sub.2 Desorption Catalyst of the Invention
[0026] The CO.sub.2 desorption catalyst of the invention
(hereinafter sometimes simply referred to as "the catalyst of the
invention") comprises an inorganic powder or inorganic powder
compact having a BET specific surface area of 7 m.sup.2/g or more.
Since the inorganic powder or inorganic powder compact has a BET
specific surface area of 7 m.sup.2/g or more, the CO.sub.2
desorption catalyst has an excellent activity to desorb CO.sub.2
from a CO.sub.2-containing absorbing solution. A BET specific
surface area is a value obtained by dividing an inorganic powder
surface area including the contribution of microscopic unevenness,
pores, etc., by the mass of the inorganic powder. A molecule whose
adsorption area has been calculated is allowed to adsorb onto the
surface of an inorganic powder at a liquid nitrogen temperature,
and based on the adsorbed amount, the BET surface area can be
calculated. The upper limit of the BET specific surface area is
preferably 500 m.sup.2/g or less.
[0027] The inorganic powder or inorganic powder compact has a BET
specific surface area of more preferably 50 to 400 M.sup.2/g, and
still more preferably 60 to 250 m.sup.2/g, in view of the catalytic
effect and strength thereof.
[0028] The BET specific surface area of the inorganic powder or
inorganic powder compact can be obtained by measuring the BET
specific surface area of the inorganic powder. When the inorganic
powder has a BET specific surface area of 7 m.sup.2/g or more, the
inorganic powder compact also has a BET specific surface area of 7
m.sup.2/g or more.
[0029] The BET specific surface area of the inorganic powder can be
measured using a commercially available measuring instrument.
Examples of an instrument for measuring the BET specific surface
area include the NOVA-4200e, produced by Quantachrome, and the
like.
[0030] The components of the catalyst of the invention (inorganic
powder or inorganic powder compact) are not limited as long as they
are inorganic components. For example, any inorganic components can
be used, such as boron nitride (BN), metal oxides, metal nitrides,
metal carbides, metal borides, metals (simple substances),
intermetallic compounds, and clay minerals. In the catalyst of the
invention, inorganic powders or inorganic powder compacts may be
used singly or in a combination of two or more. When two or more
types of inorganic powders or inorganic powder compacts are
combined for use, the inorganic powders or inorganic powder
compacts may be simply mixed, or may be in the form of a solid
solution. For example, a solid solution of a plurality of metal
oxides may be used as a composite metal oxide.
[0031] Examples of metal oxides include Al.sub.2O.sub.3, SiO.sub.2,
TiO.sub.2, Cr.sub.2O.sub.3, MgO, Ga.sub.2O.sub.3, CuO, ZnO, and the
like. Examples of composite metal oxides include
Al.sub.2O.sub.3--Ga.sub.2O.sub.3, CuO--ZnO,
Al.sub.2O.sub.3--SiO.sub.2, and SiO.sub.2--TiO.sub.2; and Sr- and
Mg-doped lanthanum gallate (LSGM), and Co-doped LSGM (LSGMC), and
the like.
[0032] Examples of metal nitrides include AlN, SiN, TiN, and the
like.
[0033] Examples of metal carbides include SiC, TiC, MgC.sub.2, and
the like.
[0034] Examples of metal borides include Co.sub.2B, Fe.sub.2B,
Ni.sub.2B, PtB, RuB.sub.2, and the like.
[0035] Examples of metals (simple substances) include Pd, Fe, Co,
Ni, Cu, Ru, Ag, Au, Pt, Cr, and the like.
[0036] Examples of intermetallic compounds include AlFe,
CoPt.sub.3, CoFe, RuTi, and the like.
[0037] Examples of clay minerals include zeolites, talcs,
sepiolites, kaolinites, montmorillonites, and the like.
[0038] The catalyst of the invention is preferably at least one
member selected from the group consisting of BN, Ga.sub.2O.sub.3,
Al.sub.2O.sub.3, Pd, Fe, and zeolites.
[0039] As the catalyst of the invention, an inorganic powder or
inorganic powder compact in which metal is supported on a component
mentioned above may be used. As the metal supported on the
component, the same metals given above as examples of metals (Pd,
Fe, Co, Ni, Cu, Ru, Ag, Au, Pt, Cr, and the like) may be used. For
example, when Al.sub.2O.sub.3 is used as the catalyst of the
invention, at least one member selected from the group consisting
of Pd, Fe, Co, Ag, and Ni (in particular, preferably at least one
member selected from the group consisting of Pd, Fe, and Ag) is
supported on the Al.sub.2O.sub.3. In this manner, the CO.sub.2
desorption activity can be improved.
[0040] When metal is supported, the loading of the supported metal
is preferably 0.1 to 10 wt %, based on the entire catalyst of the
invention.
[0041] The metal supported on the CO.sub.2 desorption catalyst is
in many cases in the so-called oxidation state immediately after
the preparation. In this case, a reduction treatment may be
performed in advance so that the metal in the oxidation state is
reduced to the metal state. The catalytic activity of the CO.sub.2
desorption catalyst is thereby further enhanced.
[0042] The reduction treatment may be performed, for example, by
heat treatment in gas such as H.sub.2 or H.sub.2--N.sub.2. The heat
treatment is performed at a temperature of preferably 200 to
400.degree. C. The duration of the heat treatment is preferably
about 30 minutes to 5 hours.
[0043] The shape of the inorganic powder is not particularly
limited. Examples include a spherical shape, a granular shape, an
unfixed shape, a branched shape, a needle shape, a rod shape, a
flat shape, and the like.
[0044] The size of the inorganic powder is not particularly
limited. When the inorganic powder is in the shape of a sphere, the
diameter is preferably about 0.01 to 10 .mu.m.
[0045] A compact obtained by shaping the inorganic powder (an
inorganic powder compact) can also be used as the catalyst of the
invention. The shape of this compact is not particularly limited.
Examples include a spherical shape, a columnar shape, a disk shape,
a ring shape, a coating film shape, and the like.
[0046] The size of the inorganic powder compact is not particularly
limited. When the compact is in the shape of a disk, the diameter
is preferably about 1 to 100 mm.
[0047] The method for producing the inorganic powder compact is not
particularly limited. For example, an inorganic powder that can be
used in this invention is shaped by a tableting machine, an
extruder, or the like.
[0048] When the inorganic powder compact is in the shape of a
coating film, the film thickness is preferably about 0.1 to 0.5
mm.
[0049] The inorganic powder compact in the shape of a coating film
(a coating film-shaped compact) may be produced, for example, in
the following manner: organic substances, such as polyethylene
glycol and/or ethyl cellulose, are mixed with an inorganic powder
to produce a paste composition, the produced paste composition is
applied to form a coating film and then calcined to decompose and
remove the organic substances. The calcination here is preferably
performed at 200.degree. C. or higher.
[0050] The coating film-shaped compact may be formed on the surface
of a metal filler, on the inner surface (wall surface) of a
regeneration tower described later, on a narrow tube of a vapor
heater, on a plate surface, and the like. When the coating
film-shaped compact is formed on the surface of a metal filler, the
filler can be used to fill a regeneration tower as is
conventionally done or can be placed in a CO.sub.2-containing
absorbing solution reservoir at the bottom of a regeneration tower.
The coating film-shaped compact may also be formed on the inner
surface of a structure in which many flat plates are stacked
leaving gaps that serve as flow paths for an absorbing material, or
on the inner surface of a honeycomb (monolith) structure with many
parallel through-holes. It is also possible to form these
structures themselves from the inorganic powder compact.
CO.sub.2 Desorption Device and Desorption Method of the
Invention
[0051] The CO.sub.2 desorption device and desorption method of the
invention are described below. FIG. 1 is a schematic diagram
roughly illustrating a CO.sub.2 desorption device according to one
embodiment of the invention. FIG. 2 is a schematic diagram roughly
illustrating the inside of the regeneration tower of FIG. 1.
[0052] As shown in FIG. 1, the CO.sub.2 desorption device of the
invention includes a CO.sub.2 absorption tower for absorbing and
removing CO.sub.2 by using an absorbing solution (hereinafter
simply referred to as "absorption tower") and a regeneration tower
for regenerating the absorbing solution containing absorbed
CO.sub.2. In an exhaust gas introduction area, an exhaust gas
cooling unit and an exhaust gas cooler for cooling exhaust gas, an
exhaust gas blower for pressurizing exhaust gas, and the absorption
tower filled with the CO.sub.2 absorbing solution for absorbing and
removing CO.sub.2 from exhaust gas, are arranged. In this
application, an absorbing solution containing absorbed CO.sub.2 is
referred to as a CO.sub.2-containing absorbing solution (or a
CO.sub.2-containing solution), and an absorbing solution not
containing absorbed CO.sub.2 or an absorbing solution regenerated
in the regeneration tower is referred to as an unabsorbed solution.
In this application, the CO.sub.2-containing absorbing solution and
the unabsorbed solution are distinguished from each other.
[0053] The solution used for absorbing CO.sub.2 (unabsorbed
solution) is not particularly limited. For example, an aqueous
solution of one or more alkanolamines, such as monoethanolamine,
diethanolamine, triethanolamine, methyldiethanolamine,
diisopropanolamine, and diglycolamine, in water is suitably used.
These alkanolamines may be used singly or in a combination of two
or more.
[0054] The absorption tower and the regeneration tower are
connected by a line for supplying the CO.sub.2-containing absorbing
solution to the regeneration tower and a line for supplying the
regenerated unabsorbed solution to the absorption tower. These two
lines are provided with a heat exchanger for exchanging heat
between the CO.sub.2-containing absorbing solution and the
unabsorbed solution. Between the heat exchanger and the absorption
tower in the line for supplying the unabsorbed solution to the
absorption tower, a cooler for further cooling the unabsorbed
solution is provided.
[0055] As shown in FIG. 2, the regeneration tower is provided with
a nozzle for downwardly spraying the CO.sub.2-containing absorbing
solution supplied from the line. Below the nozzle, a filled portion
filled with the catalyst of the invention is provided.
[0056] At the bottom of the regeneration tower, a heater for
heating the CO.sub.2-containing absorbing solution is provided. The
heater and the regeneration tower are connected by a line so that
the CO.sub.2-containing absorbing solution accumulated in the
bottom of the tower is returned to the bottom of the tower after
being heated by the heater.
[0057] At the CO.sub.2 gas outlet side at the top of the
regeneration tower, a line is provided, in which a cooler for
cooling CO.sub.2 gas and a separator for separating moisture from
CO.sub.2 gas are sequentially arranged. The separator is provided
with a line for resupplying water separated by the separator to the
top of the regeneration tower. This line is provided with a nozzle
for downwardly spraying this reflux water.
[0058] Next, a CO.sub.2 desorption method is described below.
CO.sub.2-containing exhaust gas discharged from a boiler is first
transferred to the cooling unit to be cooled with cooling water.
The cooled exhaust gas is pressurized by the blower, and then
transferred to the absorption tower.
[0059] In the absorption tower, exhaust gas is brought into
countercurrent contact with an unabsorbed solution mainly
containing alkanolamine, and as a result of the chemical reaction,
CO.sub.2 in the exhaust gas is absorbed into the unabsorbed
solution. The exhaust gas from which CO.sub.2 was removed is
discharged out of the system from the top of the tower. The
absorbing solution containing absorbed CO.sub.2 is pressurized with
a pump, heated by the heat exchanger, and supplied to the
regeneration tower via the line from the bottom of the tower.
[0060] In the regeneration tower, the CO.sub.2-containing absorbing
solution is sprayed from the nozzle and flows down through the
surface of the catalyst of the invention. At this time, the
absorbing solution is heated by high-temperature water vapor coming
upward from below (described later), causing partial desorption of
CO.sub.2. The use of the catalyst of the invention in this
desorption reaction better promotes desorption, compared to known
metal fillers. The CO.sub.2-containing absorbing solution that has
passed through the filled portion accumulates at the bottom of the
tower. The accumulated CO.sub.2-containing absorbing solution is
extracted through the line and heated by the heater, causing
partial desorption of CO.sub.2 with the generation of
high-temperature water vapor. Here, CO.sub.2 desorption can be
promoted with the application of the catalyst of the invention to
the surface of the heater. The desorbed CO.sub.2 and the
high-temperature water vapor move upward inside the tower while the
not evaporated CO.sub.2-containing absorbing solution moves
downward to be accumulated again. As described above, the
high-temperature water vapor that moves upward inside the tower
heats the CO.sub.2-containing absorbing solution that is flowing
down through the surface of the catalyst of the invention. The
CO.sub.2 and water vapor discharged from the top of the
regeneration tower are cooled by the cooler so that the moisture is
condensed. The condensed moisture is separated by the separator and
returned to the regeneration tower. The high-purity CO.sub.2 free
from moisture is discharged out of this CO.sub.2 desorption device,
so as to be effectively used for other purposes.
[0061] As described above, the inorganic powder or inorganic powder
compact having a BET specific surface area of 7 m.sup.2/g or more
can efficiently desorb CO.sub.2 from a CO.sub.2-containing
solution.
Advantageous Effects of Invention
[0062] The catalyst of the invention comprises an inorganic powder
or inorganic powder compact having a BET specific surface area of 7
m.sup.2/g or more, and thus has an excellent activity to desorb
CO.sub.2 from a CO.sub.2-containing absorbing solution. Therefore,
the inorganic powder or inorganic powder compact can be suitably
used as a catalyst for desorbing CO.sub.2 from a
CO.sub.2-containing solution.
BRIEF DESCRIPTION OF DRAWINGS
[0063] FIG. 1 is a schematic diagram roughly illustrating a
CO.sub.2 desorption device according to one embodiment of the
invention. The arrow A in FIG. 1 indicates a movement of exhaust
gas free from CO.sub.2 towards a flue. The arrow B in FIG. 1
indicates that CO.sub.2 is separated from the absorbing solution.
The arrow C in FIG. 1 indicates that CO.sub.2 is collected.
[0064] FIG. 2 is a schematic diagram roughly illustrating the
inside of the regeneration tower of FIG. 1. The arrow D in FIG. 2
indicates that a CO.sub.2-containing absorbing solution is
transferred from the absorption tower. The arrow E in FIG. 2
indicates that the CO.sub.2-containing absorbing solution
transferred from the absorption tower moves down through the
surface of the CO.sub.2 desorption catalyst of the invention while
allowing desorption of CO.sub.2 under the heat of high-temperature
water vapor. The arrows F in FIG. 2 indicate upward movement of the
high-temperature water vapor and CO.sub.2, and downward movement of
the not evaporated absorbing solution. The arrow G in FIG. 2
indicates that the absorbing solution is partially extracted to be
heated by the heater (high-temperature water vapor is generated
when the absorbing solution is heated by the heater).
DESCRIPTION OF EMBODIMENTS
[0065] The invention is described in further detail below with
reference to Examples. However, the scope of the invention is not
limited to these Examples.
Example 1
[0066] 15 mg of a BN powder (produced by Sigma-Aldrich) was pressed
into a disk shape having a diameter of about 5 mm to produce the
inorganic powder compact (catalyst) (metals unsupported) of Example
1. Based on the size of this compact, the external surface area was
calculated to be 0.55 cm.sup.2. Hereinafter, this simple external
surface area of the external surface of the compact is referred to
as the "apparent surface area."
Example 2
[0067] An aqueous solution was prepared by dissolving gallium
nitrate n-hydrate (Ga=18.9%) (Mitsuwa Chemistry Co., Ltd.) and
aluminum nitrate nonahydrate (Nacalai Tesque, Inc.) in 100 mL of
water, in such a manner that Ga/(Ga+Al)=0.5. Next, ammonium
carbonate (5-fold equivalent) (the "equivalent" as used herein is
based on the total molar numbers of Ga ions and Al ions) was added
at once to the aqueous solution above, and stirred for 1 hour with
a stirrer. The produced precipitate was washed several times with
water and collected, followed by calcination at 700.degree. C. in
air to obtain Ga.sub.2O.sub.3--Al.sub.2O.sub.3. Subsequently, 15 mg
of the EN powder used in Example 1 and 15 mg of this
Ga.sub.2O.sub.3--Al.sub.2O.sub.3 were thoroughly mixed and pressed
into a disk shape as in Example 1 to thereby produce the inorganic
powder compact of Example 2.
Examples 3 to 14
[0068] Each metal salt powder was dissolved in water to produce
each metal salt aqueous solution. Each metal salt aqueous solution
was impregnated onto an Al.sub.2O.sub.3 powder (Sumitomo Chemical
Co., Ltd., product name: AKP-G05) or onto an SiO.sub.2 powder (Fuji
Silysia Chemical Ltd., product name: CARiACT G-10), in such a
manner that the weight of each metal after reduction treatment was
2 wt %, followed by drying in air at 100.degree. C. for 6 hours and
then calcination in air at 400.degree. C. for 30 minutes to thereby
obtain various inorganic powders (produced by an impregnation
method). Each metal salt powder used herein is shown below.
Metal Salt Powders
[0069] Pd salt: a palladium nitrate n-hydrate
(Pd(NO.sub.3).sub.2.nH.sub.2O) powder, produced by Kishida Chemical
Co., Ltd.)
[0070] Fe salt: an iron nitrate nonahydrate
(Fe(NO.sub.3).sub.3.9H.sub.2O) powder, produced by
Sigma-Aldrich
[0071] Co salt: a cobalt nitrate hexahydrate
(Co(NO.sub.3).sub.2.6H.sub.2O) powder, produced by
Sigma-Aldrich
[0072] Ag salt: a silver nitrate (AgNO.sub.3) powder, produced by
Sigma-Aldrich
[0073] Ni salt: a nickel nitrate hexahydrate
(Ni(NO.sub.3).sub.2.6H.sub.2O) powder, produced by Kanto Chemical
Co., Inc.
[0074] Pt salt: a diammine dinitro platinum
(Pt(NH.sub.3).sub.2(NO.sub.2).sub.2) powder, produced by Kojima
Chemicals Co., Ltd.
15 mg of the EN powder used in Example 1 and 15 mg of each of these
various inorganic powders obtained by the impregnation method above
were thoroughly mixed, and pressed into a disk shape as in Example
1. A heat treatment was further performed at 300 to 400.degree. C.
in 1% H.sub.2--N.sub.2 gas for 2 hours to thereby produce the
inorganic powder compacts of Examples 3 to 14.
Example 15
[0075] 2.5 mol of sodium carbonate was dissolved in 2 L of water
and kept warm at 60.degree. C. This aqueous alkaline solution was
used as Solution A. 0.15 mol of zinc nitrate, 0.015 mol of aluminum
nitrate, 0.012 mol of gallium nitrate, and 0.003 mol of magnesium
nitrate were dissolved in 600 mL of water, and kept warm at
60.degree. C. This acidic solution was used as Solution B. 0.3 mol
of copper nitrate was dissolved in 300 mL of water and kept warm at
60.degree. C. This acidic solution was used as Solution C. First,
Solution B was uniformly added to Solution A dropwise over 30
minutes while being stirred to obtain a suspension. Next, Solution
C was added to this suspension dropwise over 30 minutes at a
constant rate to obtain a precipitate. After completion of the
dropwise addition, aging was performed for 2 hours. Next, the
precipitate was filtered and washed to the extent that neither
sodium ions nor nitrate ions were detected. Further, the resulting
product was dried at 100.degree. C. for 24 hours and then calcined
at 300.degree. C. for 3 hours to produce a cylindrical compact of a
composite oxide (CuO--ZnO--Al.sub.2O.sub.3--Ga.sub.2O.sub.3--MgO;
metal molar ratio: Cu:Zn:Al:Ga:Mg=100:50:5:4:1). A portion of this
cylindrical compact was chipped off to give 15 mg of a spherical
compact, which was subjected to heat treatment at 300 to
400.degree. C. in 1% H.sub.2--N.sub.2 gas for 2 hours to produce
the inorganic powder compact of Example 15.
Example 16
[0076] A portion of Cr-based catalyst (Sud-Chemie Catalyst Co.,
Ltd., product name: ActiSorb 410RS) was chipped off to give 15 mg
of a spherical inorganic powder, which was subjected to heat
treatment at 300 to 400.degree. C. in 1% H.sub.2--N.sub.2 gas for 2
hours to produce the inorganic powder compact of Example 16.
Example 17
[0077] 660 mg of Zeolite (produced by Tosoh Corporation, product
name: HSZ-640 HOD1A; BET specific surface area catalog value: 400
m.sup.2/g; diameter: about 1.5 mm; length: about 6 .mu.m; extruded
shape) was prepared.
Example 18
[0078] 660 mg of spherical Al.sub.2O (produced by Sumitomo Chemical
Co., Ltd., product name: KHA-46; BET specific surface area catalog
value: 150 m.sup.2/g) was prepared. Specifically, six spherical
Al.sub.2O.sub.3 articles (110 mg each) each having a diameter of
about 5 mm were prepared.
Comparative Example 1
[0079] Conventionally used metal filler (100 mg) was prepared.
Specifically, one metal filler (100 mg) was prepared by wadding a
stainless steel mesh with a width of 6 mm and a length of 30 mm
into a ball having a diameter of 6 mm.
Comparative Example 2
[0080] Conventionally used metal filler (660 mg) was prepared.
Specifically, seven fillers in total were prepared: six metal
fillers (100 mg each) used in Comparative Example 1; and one metal
filler (60 mg) obtained by wadding a stainless steel mesh with a
width of 6 mm and a length of 18 mm into a ball having a diameter
of 6 mm.
Test Example 1
Surface Area Measurement
[0081] The apparent surface area of each catalyst obtained in
Examples 1 to 16 and Comparative Examples 1 to 2 (inorganic powder
compacts, fillers, etc.) was calculated, and the BET specific
surface area was measured.
[0082] The apparent surface area was calculated based on the size
and shape of each catalyst. The apparent surface area of each metal
filler of Comparative Examples 1 and 2 was calculated based on the
diameter, length, and number of stainless steel wires used to form
the mesh. The BET specific surface area was obtained using the
NOVA-4200e produced by Quantachrome. Tables 1 and 2 below show the
measurement results.
Test Example 2
Measurement of CO.sub.2 Amount Present in Test Liquid and
Calculation of Desorption Amount Per Apparent Surface Area
[0083] 30 wt % of aqueous monoethanolamine (MEA) solution (50 mL)
containing absorbed CO.sub.2 (123.4 or 127.1 g-CO.sub.2/L) was
placed into a volumetric flask, to which one of each of the
catalysts obtained in Examples 1 to 16 and Comparative Example 1
was added. The aqueous MEA solution was then heated. The heating
was performed using a silicone oil bath. The temperature was
increased at a rate of 1.4.degree. C./min. After the temperature of
the aqueous MEA solution reached 104.degree. C. and was maintained
at 104.degree. C. for 30 minutes, a small amount of the aqueous MEA
solution was sampled to measure the amount of residual CO.sub.2.
Based on the measured amount of residual CO.sub.2, the CO.sub.2
desorption amount per apparent surface area was calculated. The
CO.sub.2 desorption amount per apparent surface area was obtained
by subtracting the amount of residual CO.sub.2 after the
temperature reached 104.degree. C. and was maintained at this
temperature for 30 minutes from the CO.sub.2 amount before the
test, and dividing the result by the apparent surface area. Table 1
shows the test results.
Test Example 3
Calculation of Desorption Rate of CO.sub.2 Present in Test Liquid
and Desorption Rate of CO.sub.2 Per Apparent Surface Area
[0084] An aqueous amine solution (150 mL) containing absorbed
CO.sub.2 (151.6 g-CO.sub.2/L) was placed into a flask, to which one
of each of the catalysts obtained in Examples 17 and 18 and
Comparative Example 2 was added. This absorbing solution was heated
to 75.degree. C. The heating was performed by immersing the flask
in a silicone oil bath heated to 120.degree. C. The flow rate of
desorbed CO.sub.2 when the absorbing solution had a temperature of
75.degree. C. was measured using a mass flow meter (Azbil
Corporation, MQV0002). Table 2 shows the test results.
Consideration 1:
[0085] Referring to the results obtained in Test Example 2 in terms
of the CO.sub.2 desorption amount per apparent surface area
obtained 30 minutes after the solution temperature reached
104.degree. C., the use of the catalysts of Examples 1 to 16
resulted in much greater values, compared to the results of
Comparative Example 1. This indicates that the CO.sub.2 desorption
activity of each catalyst (inorganic powder compact) of Examples 1
to 16 is far more excellent than that of metal filler. The use of a
catalyst free from BN, such as the catalysts obtained in Examples
15 and 16, also resulted in a high CO.sub.2 desorption amount per
apparent surface area. Therefore, BN is not an essential component
in the catalyst of the invention.
Consideration 2:
[0086] Referring to the results obtained in Test Example 3 in terms
of the CO.sub.2 desorption rate when the absorbing solution had a
temperature of 75.degree. C., the use of the catalysts of Examples
17 and 18 showed much higher values, compared to the results
obtained with the use of the metal filler of Comparative Example 2.
This indicates that the CO.sub.2 desorption activity of each
catalyst of Examples 17 and 18 is far more excellent than that of
metal filler.
[0087] When each inorganic powder compact of Examples 1 to 18 is
observed at the micro level, the surface thereof is not flat due to
the presence of microscopic unevenness, pores, and the like, unlike
metal filler. The presence of the microscopic unevenness, pores,
and the like is assumed to be one of the reasons for the high
CO.sub.2 desorption activity. Considering this, high CO.sub.2
desorption activity is achieved not only by the catalysts of
Examples 1 to 16, but also by those having microscopic unevenness
and pores to some extent. Among the catalysts of Examples 1 to 16,
the compact of the BN powder used in Example 1 has the smallest BET
surface area of 7 m.sup.2/g. A catalyst having a BET specific
surface area equal to or higher than this value is therefore
expected to achieve an effect similar to the above.
TABLE-US-00001 TABLE 1 CO.sub.2 amount in test liquid Desorption
(g-CO.sub.2/L) amount per Weight and surface area of test catalyst
30 min apparent surface Catalyst Apparent after the area 30 min
other than surface BET specific temp. after the temp. BN BN area
surface area Before reached reached 104.degree. C. (mg) (mg)
(cm.sup.2) (m.sup.2/g) test 104.degree. C. (g-CO.sub.2/cm.sup.2)
Ex. 1 BN 0 15 0.55 7 127.1 31.3 174 Ex. 2 BN +
Ga.sub.2O.sub.3--Al.sub.2O.sub.3-based 15 15 0.46 78 123.4 29.9 203
catalyst Ex. 3 BN + Pd/Al.sub.2O.sub.3 catalyst 15 15 0.48 80 123.4
31.7 191 Ex. 4 BN + Fe/Al.sub.2O.sub.3 catalyst 15 15 0.49 73 123.4
32.9 185 Ex. 5 BN + Pd/SiO.sub.2 catalyst 15 15 0.51 113 123.4 34.6
174 Ex. 6 BN + Co/SiO.sub.2 catalyst 15 15 0.50 77 123.4 35.5 176
Ex. 7 BN + Fe/SiO.sub.2 catalyst 15 15 0.50 96 123.4 36.1 175 Ex. 8
BN + Co/Al.sub.2O.sub.3 catalyst 15 15 0.49 74 123.4 36.2 178 Ex. 9
BN + Ag/Al.sub.2O.sub.3 catalyst 15 15 0.48 68 123.4 36.8 180 Ex.
10 BN + Ag/SiO.sub.2 catalyst 15 15 0.51 89 123.4 37.1 169 Ex. 11
BN + Ni/Al.sub.2O.sub.3 catalyst 15 15 0.49 77 123.4 37.3 176 Ex.
12 BN + Pt/SiO.sub.2 catalyst 15 15 0.51 112 123.4 37.8 168 Ex. 13
BN + Pt/Al.sub.2O.sub.3 catalyst 15 15 0.49 71 123.4 40.2 170 Ex.
14 BN + Ni/SiO.sub.2 catalyst 15 15 0.50 70 123.4 40.4 166 Ex. 15
CuO--ZnO-based catalyst 15 0 0.24 63 123.4 34.6 370 Ex. 16 Cr-based
catalyst 15 0 0.43 245 123.4 37.5 200 Comp. Ex. 1 Metal filler 100
0 3.4 <3 123.4 40.2 24 (less than 3)
TABLE-US-00002 TABLE 2 CO.sub.2 desorption rate Weight and surface
area of when absorbing solution is test catalyst at 75.degree. C.
BET CO.sub.2 desorption Apparent specific CO.sub.2 rate per surface
surface desorption apparent Weight area area rate surface area (mg)
(cm.sup.2) (m.sup.2/g) (mL/min) (mL/(min cm.sup.2) Ex. 17 Zeolite
catalyst 660 21 400 473 23 Ex. 18 Al.sub.2O.sub.3 catalyst 660 4.7
150 419 89 Comp. Ex. 2 Metal filler 660 22 <3 144 7 (less than
3)
EXPLANATION OF REFERENCE NUMERALS
[0088] 1. Exhaust Gas [0089] 2. Exhaust Gas Cooling Tower [0090] 3.
Exhaust Gas Cooler [0091] 4. Exhaust Gas Blower [0092] 5.
Absorption Tower [0093] 6. Filler [0094] 7. Extraction Pump [0095]
8. CO.sub.2-containing Absorbing Solution [0096] 9. Heat Exchanger
[0097] 10. Regeneration Tower [0098] 11. Filler [0099] 12. Heater
[0100] 13. Heated Vapor (High-temperature Water Vapor) [0101] 14.
Cooler [0102] 15. CO.sub.2 Separator [0103] 16. Cooler [0104] 17.
CO.sub.2-containing Absorbing Solution [0105] 18. CO.sub.2
Desorption Catalyst of the Invention [0106] 19. Heated Water Vapor
(High-temperature Water Vapor) [0107] 20. Mixture of
High-temperature Absorbing Solution, Water Vapor, and CO.sub.2
[0108] 21. Unabsorbed Solution after CO.sub.2 has been desorbed
therefrom [0109] 22. Mixture of CO.sub.2 Gas and Water Vapor
* * * * *