U.S. patent application number 11/996151 was filed with the patent office on 2009-06-04 for scr catalyst for removal of nitrogen oxides.
Invention is credited to Soon-Hyo Chung, Heon-Phil Ha, Young-Joo Oh.
Application Number | 20090143225 11/996151 |
Document ID | / |
Family ID | 37668967 |
Filed Date | 2009-06-04 |
United States Patent
Application |
20090143225 |
Kind Code |
A1 |
Ha; Heon-Phil ; et
al. |
June 4, 2009 |
SCR CATALYST FOR REMOVAL OF NITROGEN OXIDES
Abstract
The present invention provides for catalysts for selective
catalytic reduction of nitrogen oxides. The catalysts comprise
metal oxide supporters, vanadium, an active material, and antimony,
a promoter that acts as a catalyst for reduction of nitrogen
oxides, and at the same time, can promote higher sulfur poisoning
resistance and low temperature catalytic activity. The amount of
antimony of the catalysts is preferably 0.5-7 wt %.
Inventors: |
Ha; Heon-Phil; (Gyeonggi-Do,
KR) ; Chung; Soon-Hyo; (Seoul, KR) ; Oh;
Young-Joo; (Seoul, KR) |
Correspondence
Address: |
OSTROLENK FABER GERB & SOFFEN
1180 AVENUE OF THE AMERICAS
NEW YORK
NY
100368403
US
|
Family ID: |
37668967 |
Appl. No.: |
11/996151 |
Filed: |
January 10, 2006 |
PCT Filed: |
January 10, 2006 |
PCT NO: |
PCT/KR2006/000098 |
371 Date: |
July 16, 2008 |
Current U.S.
Class: |
502/247 ;
502/349; 502/350; 502/353; 502/354 |
Current CPC
Class: |
B01D 2251/2062 20130101;
B01D 2255/20723 20130101; B01D 2255/20707 20130101; B01D 53/8628
20130101; B01D 53/9418 20130101; B01D 2255/2098 20130101; B01J
23/22 20130101 |
Class at
Publication: |
502/247 ;
502/353; 502/350; 502/349; 502/354 |
International
Class: |
B01J 21/06 20060101
B01J021/06; B01J 23/22 20060101 B01J023/22; B01J 21/04 20060101
B01J021/04; B01J 23/16 20060101 B01J023/16 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 19, 2005 |
KR |
10-2005-0065430 |
Claims
1. A ammonia SCR catalyst for reduction of nitrogen oxides
comprising: a carrier; and vanadium oxide as an active material on
the supporter; and antimony as a promoter that reduces sulfur
poisoning and enhances low temperature catalytic activity.
2. The catalyst of claim 1, wherein the supporter is at least one
from the group consisted of titanium oxide, silicate, zirconia,
alumina and the mixture thereof.
3. The catalyst of claim 1, wherein 1.about.3 wt. % of the vanadium
is used.
4. The catalyst of claim 1, wherein 0.5.about.7 wt. % of the
antimony is used.
Description
TECHNICAL FIELD
[0001] The present invention relates to catalysts for selective
reduction of nitrogen oxides, and more particularly to catalysts
for removal of nitrogen oxides that have enhancing effects on the
reduction activity of nitrogen oxides at low temperatures and on
the sulfur poisoning resistance.
BACKGROUND ART
[0002] Nitrogen oxides (NO.sub.x) are usually produced when fuels
are combusted, and are exhausted from moving sources such as a
motor vehicle and fixed sources such as a power plant or an
incinerator. These nitrogen compounds are identified as the major
causes of acid rain and smog formation. Since environmental
protection regulations have become stricter recently, more studies
are being carried out, in response, in order to reduce nitrogen
compounds through catalysts.
[0003] As a method of removing nitrogen compounds that were emitted
from fixed sources, selective catalytic reduction (SCR) device that
uses vanadium oxides (V.sub.2O.sub.5) as active materials
impregnated on a titanium oxide supporters have been generally
used. Ammonia has been known as a most suitable reduction agent for
the system.
[0004] However, for the titanium-type SCR catalysts that use
ammonia as a reductant, a catalyst that operate under 300.degree.
C. is frequently required according to the working condition.
Additionally, in case of a flue gas which contains sulfur oxides
that easily poison the catalysts at low temperatures, catalysts
that could with this problem also need to be developed.
[0005] For the V.sub.2O.sub.5/TiO.sub.2 SCR catalyst, high
catalytic de NOx activity is exhibited at 300 .degree. C. or
higher. Therefore, it is necessary to develop a catalyst which
shows high activity at a lower reaction temperature. Generally,
when titanium oxide (TiO.sub.2) supporters and vanadium (V) are
used as active catalytic materials, additional amount of vanadium
is added to increase the catalytic activity at 300.degree. C. or
lower. However, when the amount of vanadium is increased, the
oxidation of sulfur dioxide(SO.sub.2) that are contained in the
exhaust gas to sulfur trioxide (SO.sub.3) is induced, which then
react with slipped ammonia. As a result, ammonium bisulfate,
NH.sub.4HSO.sub.4 which is a solid salt, is formed.
[0006] The produced ammonium bisulfate salts are imbedded into the
surfaces of the catalysts, thereby interfering with the reduction
reaction. As a result, as the amount of unreacted ammonia
increases, formation of sulfur trioxides (SO.sub.3) is promoted,
thereby accelerating the sulfur poisoning, which eventually shorten
the life of the catalysts.
[0007] Therefore, catalysts that can improve catalytic activity at
low temperatures without promoting the oxidation of sulfur dioxides
have been developed. In general, in order to enhance low
temperature activity and sulfur poisoning resistance, tungsten has
been added to vanadium/titania catalysts as a promoter. For
example, when tungsten oxides were added, sulfur poisoning
resistance at low temperatures could be increased.
[0008] However, since the amount of tungsten oxides used is high,
approximately between 5 wt. % and 10 wt. %, the increase in the
price of catalysts is unavoidable.
[0009] Moreover, most of the conventional catalysts for removal of
nitrogen oxides with less sulfur poisoning have been developed such
that a supporter is impregnated with special active materials.
[0010] A conventional art uses a TiO.sub.2 supporter impregnated
with vanadium sulfate (VSO.sub.4), vanadyl sulfate (VO SO.sub.4)
and the like, and is reacted at the range of temperatures at
300-520.degree. C. However, the problem of the previously-explained
sulfur poisoning also arises in this case due to the usage of
vanadium.
[0011] According to another conventional art, TiO.sub.2 supporter
impregnated with active materials such as V.sub.2O.sub.5,
MoO.sub.3, WO.sub.3, Fe.sub.2O.sub.3, CuSO.sub.4, VOSO.sub.4,
SnO.sub.2, Mn.sub.2O.sub.3, Mn.sub.3O.sub.4 are used. However, not
only the problem of the sulfur poisoning from vanadium oxides still
exists, but also, the previously-mentioned high cost problem due to
the usage of tungsten oxides are accompanied.
DISCLOSURE OF INVENTION
[0012] The present invention provides for catalysts for the
reduction of nitrogen oxides that are impregnated in to supporters
and contain vanadium as an active material and antimony as a
promoter that promote reduction of nitrogen oxides at low
temperatures and increase sulfur poisoning resistance.
[0013] Another embodiment of the present invention provides for the
transition metal oxides supporters, titanium oxides, silicate,
zirconia, alumina and the mixture thereof, where vanadium and
antimony can be impregnated.
[0014] Another embodiment of the present invention provides that
the amount of said vanadium impregnated is 1-3 wt. %.
[0015] Another embodiment of the present invention provides that
the amount of said antimony impregnated is 0.5-7 wt. %.
[0016] As mentioned above in the conventional arts, nitrogen oxides
can be reduced to harmless nitrogen and water by using a reductant.
Catalysts for the reduction of nitrogen oxides are used and each of
these catalysts comprise a supporter, an active material and a
promoter which reduces sulfur poisoning and enhancing low
temperature catalytic activity.
[0017] For the supporter, titanium oxides, silicate, zirconia,
alumina and the mixture thereof can be used. Preferably, titania
(TiO.sub.2) is used.
[0018] Moreover, active and promoting materials comprise materials
such as vanadium and antimony, respectively. The vanadium includes
a compounds (solution) that contains vanadium oxides, and the
antimony (Sb) includes compounds(solution) that contains antimony
oxides, antimony chlorides (SbCl.sub.3) and the like. Among the
impregnated active and promoting materials, vanadium oxide is used
as a main catalyst and the antimony oxide is used as an auxiliary
catalyst.
[0019] The present invention uses titanium oxide (TiO.sub.2) as a
supporter to combine the vanadium (V) and antimony (Sb) to prepare
catalysts for the reduction of nitrogen oxides. When preparing the
catalysts, impregnation method, which uses the TiO.sub.2 and
precursors containing vanadium and antimony, or other conventional
catalyst synthesis methods such as sol gel method can be used.
[0020] According to the present invention, antimony is added to
promote the reactivity at low temperatures and the sulfur poisoning
resistance. Preferably, 0.5-6 wt. % of antimony is added. By the
addition of antimony as a promoter, the addition amount of vanadium
can be reduced, and thus, the sulfur poisoning resistance can be
reduced. Preferably, 1-3 wt. % of vanadium is added.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a graph showing the NO conversions of Example 1
and Reference 1 at different temperatures.
[0022] FIG. 2 is a graph showing the sulfur poisoning resistance of
Example 1 and Reference 1 when ammonia was used as a reductant at
240.degree. C.
[0023] FIG. 3 is a graph showing the sulfur poisoning resistance of
Example 1 and Reference 2 at 230.degree. C.
[0024] FIG. 4 is a graph showing the NO conversions of Examples 1
to 7 and Reference 1 at different temperatures.
[0025] FIG. 5 is a graph comparing the sulfur poisoning resistance
of Examples 1 to 7 with Reference 1.
MODE FOR THE INVENTION
[0026] The present invention will be further illustrated by the
following examples in order to provide a better understanding of
the invention. However, the present invention is not limited to the
examples, and particularly, the substances that compose each layer
can be other substances that are within the technical effect of the
present invention.
[0027] FIG. 1 shows NO conversion without the presence of antimony
according to Reference 1 (standard 1) and one with antimony at
different temperatures according to Example 1 (type 1) of the
present invention.
[0028] Reference 1 uses titanium oxide (TiO.sub.2) carrier, without
antimony added and impregnated with 2 wt. % of vanadium as an
active material. Example 1 uses titanium oxide (TiO.sub.2) carrier
which is impregnated with 2 wt. % of vanadium as an active material
and 2 wt. % of antimony oxide as a minor catalyst. The amounts of
nitrogen oxides and ammonia used are each 800 ppm, the amount of
water is 6%, and the amount of oxygen is 3%.
[0029] FIG. 2 shows sulfur poisoning resistances of Example 1 (type
1) with antimony added and Reference 1 (standard 1) without
antimony added when ammonia was used as a reductant at 240.degree.
C. The same results were observed for Reference 1 and Example 1 as
is shown in FIG. 1, and the amount of nitrogen oxides and ammonia
used were each 800 ppm. Moreover, the amount of water and oxygen
used were 6% and 3%, respectively. In FIG. 2, Reference 1
(NH.sub.3) line and Example 1 (NH.sub.3) line each represent the
amount of unreacted ammonia, and Reference 1 (SO.sub.2) line and
Example 1 (SO.sub.2) line each represent the amount of sulfur
dioxides.
[0030] As shown in FIG. 2, in case of a high NO removal rate as in
Example 1 (type 1), since most of the ammonia provided is exhausted
during the NO removal process, the amount of unreacted ammonia can
be decreased, and the amount of emitted sulfur dioxide of is nearly
similar to the amount of the provided sulfur dioxide of 500 ppm, it
can be inferred that almost no oxidation of sulfur dioxide
occurred.
[0031] However, it is shown in Reference 1 that the amount of
unreacted ammonia is increased after about 10 hours, and the amount
of sulfur dioxide is decreased due to oxidation. The reduction of
the NO conversions after about 10 hours, also called deactivation,
was clearly indicated.
[0032] Example 1 (type 1), which added antimony as a minor
catalyst, showed changes of the amounts of unreacted ammonia and
sulfur dioxide after 16 hours. Thus, not until after 16 hours, it
could be determined that the sulfur poisoning occurred. Therefore,
as shown in FIG. 2, when antimony was added as a promoting
catalyst, the sulfur poisoning resistance was increased.
[0033] FIG. 3 compares the sulfur poisoning resistance of Example 1
with that of another Reference 2 (standard 2) using another
catalyst at 230.degree. C. Example 1 (type 1) is under the same
condition as mentioned above, reference 2 represents a common
catalyst that is impregnated with 1 wt % of vanadium to a titanium
oxide carrier and 10 wt % of tungsten as a promoting catalyst.
[0034] The injected nitrogen oxides and ammonia amounts are each
200 ppm, and the amount of sulfur dioxide is also 200 ppm.
Moreover, the amounts of water and oxygen are 12.3% and 3%,
respectively.
[0035] As shown in FIG. 3, in case of a high removal rate according
to Example 1, the increase in the amount of unreacted ammonia at
different time periods was smaller than Reference 2 (standard 2),
and the decrease amount of sulfur dioxide compared to Reference 2
was also smaller. Accordingly, Example 1 was shown to exhibit a
remarkably higher sulfur poisoning resistance than the conventional
catalyst of Reference 2.
[0036] FIG. 4 and FIG. 5 represent sulfur poisoning resistances and
the NO conversion of Reference 1 (standard 1) and Examples 1 to 7
(types 1 to 7).
[0037] Example 1 (type 1) and Reference 1 (standard 1) are same as
explained above.
[0038] Example 2 (type 2) represents catalysts that were prepared
by impregnating a titanium oxide (TiO.sub.2) carrier with 2 wt. %
of vanadium and 1 wt. % of antimony. Example 3 shows catalysts that
were prepared by impregnating a titanium oxide (TiO.sub.2) carrier
with 2 wt. % of vanadium and 0.5 wt. % of antimony. Example 4 shows
catalysts that were prepared by impregnating a titanium oxide
(TiO.sub.2) carrier with 2 wt. % of vanadium and 3 wt. % of
antimony. Example 5 (type 5) shows catalysts that were prepared by
impregnating a titanium oxide (TiO.sub.2) carrier with 2 wt. % of
vanadium and 5 wt. % of antimony. Example 6 (type 6) shows
catalysts that were prepared by impregnating a titanium oxide
(TiO.sub.2) carrier with 2 wt. % of vanadium and 7 wt. % of
antimony. Example 7 (type 7) shows catalysts that were prepared by
impregnating a titanium oxide (TiO.sub.2) carrier with 2 wt. % of
vanadium and 10 wt. % of antimony. In FIG. 4 and FIG. 5, the amount
of nitrogen oxides and ammonia added are each 800 ppm, 500 ppm for
sulfur dioxide, and 6% and 3% for water and oxygen,
respectively.
[0039] First, as shown in FIG. 4, the removal activity at low
temperatures according to Examples 1 to 6 (types 1 to 6), except
for Example 7 (type 7), was shown to be higher than that of
Reference 1. Therefore, it was shown that the amount range of
antimony that increases the removal activity at low temperature is
0.5.about.7 wt %. There can be a deviation of the amount range of
antimony due to the standard of error.
[0040] Moreover, the amount of vanadium added is preferably 2 wt %,
however considering the conventional of error of the process, it is
preferred to add a range of 1.about.3 wt %. According to FIG. 5,
other than in Example 7 (type 7), Examples 1 to 6 (types 1 to 6)
showed an increase in the amount of unreacted ammonia and a
decrease in the amount of sulfur dioxide with time compared to
Reference 1. Accordingly, it can be shown that Examples 1 to 6 all
have an increased sulfur poisoning resistance compared to Reference
1. Therefore, the amount range of antimony that increases the
sulfur poisoning resistance is 0.5.about.7 wt %. There can be a
deviation of the amount range of antimony due to a conventional of
error of the process. Additionally, although a vanadium addition
amount is preferably 2 wt %, the range of 1.about.3 wt %
considering the standard of error.
* * * * *