U.S. patent application number 12/362520 was filed with the patent office on 2010-08-05 for templated catalyst composition and associated method.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Dan Hancu, Larry Neil Lewis, Oltea Puica Siclovan, Ming Yin.
Application Number | 20100196236 12/362520 |
Document ID | / |
Family ID | 42173865 |
Filed Date | 2010-08-05 |
United States Patent
Application |
20100196236 |
Kind Code |
A1 |
Lewis; Larry Neil ; et
al. |
August 5, 2010 |
TEMPLATED CATALYST COMPOSITION AND ASSOCIATED METHOD
Abstract
A composition includes a templated metal oxide substrate having
a plurality of pores and a catalyst material includes silver. The
composition under H.sub.2 at 30 degrees Celsius, the composition at
a wavelength that is in a range of from about 350 nm to about 500
nm has a VIS-UV absorbance intensity that is at least 20 percent
less than a standard silver alumina catalyst (Ag STD). The standard
alumina is Norton alumina, and which has the same amount of silver
by weight.
Inventors: |
Lewis; Larry Neil; (Scotia,
NY) ; Hancu; Dan; (Clifton Park, NY) ;
Siclovan; Oltea Puica; (Rexford, NY) ; Yin; Ming;
(Schenectady, NY) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY;GLOBAL RESEARCH
ONE RESEARCH CIRCLE, BLDG. K1-3A59
NISKAYUNA
NY
12309
US
|
Assignee: |
GENERAL ELECTRIC COMPANY
SCHENECTADY
NY
|
Family ID: |
42173865 |
Appl. No.: |
12/362520 |
Filed: |
January 30, 2009 |
Current U.S.
Class: |
423/239.1 ;
502/243; 502/347; 502/348 |
Current CPC
Class: |
B01J 37/033 20130101;
B01J 35/002 20130101; B01D 2255/104 20130101; B01J 35/023 20130101;
B01J 37/0018 20130101; B01J 37/0201 20130101; B01J 23/50 20130101;
B01D 53/9418 20130101; B01J 37/036 20130101 |
Class at
Publication: |
423/239.1 ;
502/347; 502/348; 502/243 |
International
Class: |
B01D 53/56 20060101
B01D053/56; B01J 23/50 20060101 B01J023/50; B01J 21/04 20060101
B01J021/04; B01J 21/08 20060101 B01J021/08 |
Claims
1. A composition, comprising: a templated metal oxide substrate
having a plurality of pores; and a catalyst material comprising
silver, and the composition having a VIS-UV absorbance intensity
that is at least 20 percent less than a standard silver alumina
catalyst, and which has the same amount of silver by weight at a
wavelength in a range of from about 350 nm to about 500 nm, under
H.sub.2 at 30 degrees Celsius, wherein the composition is made by
reacting a metal alkoxide, a silver composition and a templating
agent.
2. The composition as defined in claim 1, wherein the templated
metal oxide is alumina or silica-alumina.
3. The composition as defined in claim 1, wherein the templated
metal oxide has periodically arranged templated pores, wherein the
average diameter of the pores is in a range of from about 2
nanometers to about 100 nanometers and the pores have a periodicity
in a range of from about 50 Angstrom to about 130 Angstrom.
4. The composition as defined in claim 1, wherein the templated
metal oxide has a surface area greater than about 0.5
meter/.sup.2gram.
5. The composition as defined in claim 1, wherein the templated
metal oxide is present in an amount greater than about 50 mole
percent of the composition.
6. The composition as defined in claim 1, wherein the silver is
present in an amount in a range of from about 2 weight percent to
about 10 weight percent of a total weight of the substrate.
7. The composition as defined in claim 1, wherein the composition
may further comprise a promoter.
8. The composition as defined in claim 1, wherein the composition
is free of alkaline earth metal.
9. The composition as defined in claim 1, wherein the composition
is capable of reducing NOx in reactive proximity therewith without
absorbing the NOx on a catalyst material surface.
10. The composition as defined in claim 1, wherein the composition
has capability of reducing nitrogen oxide greater than 40 percent
by volume at a temperature of about 325 degrees Celsius.
11. A method, comprising: reacting a metal alkoxide with a silver
composition and a templating agent to form a reaction product;
hydrolyzing the reaction product to form a hydrolyzed reaction
product; condensing the hydrolysed reaction product to form a
templated substrate; and controlling the reacting, hydrolyzing and
condensing step to control the silver loading of the templated
substrate, and the silver loaded templated substrate having a
VIS-UV absorbance intensity that is at least 20 percent less than a
standard silver alumina catalyst, and which has the same amount of
silver by weight at a wavelength in a range of from about 350 nm to
about 500 nm, under H.sub.2 at 30 degrees Celsius.
12. The method as defined in claim 11, wherein the condensing step
includes calcinating.
13. The method as defined in claim 12, wherein the calcinating is
done at a temperature greater than 350 degrees Celsius for a time
period greater than 10 minutes.
14. The method as defined in claim 11, the metal alkoxide is
aluminium alkoxide.
15. The method as defined in claim 11, wherein the silver
composition is selected from a group consisting of silver salt of
inorganic acids, silver salt of organic acids, and silver
oxides.
16. The method as defined in claim 11, wherein the templating agent
comprises a surfactant, cyclodextrin, or a crown ether.
17. The method as defined in claim 11, controlling the silver
loading wherein the silver is present in an amount of at least
about 2 weight percent based on a total weight of the
substrate.
18. The method as defined in claim 17, wherein the silver further
is in an amount of less than or equal to 10 weight percent of a
total weight of the substrate.
19. A method comprising: introducing a gas stream in a chamber
having a composition comprising a templated metal oxide substrate
having a plurality of pores, a catalyst material comprising an
amount of silver, wherein the composition having a VIS-UV
absorbance intensity that is at least 20 percent less than a
standard silver alumina catalyst, and which has the same amount of
silver by weight at a wavelength in a range of from about 350 nm to
about 500 nm, under H.sub.2 at 30 degrees Celsius; and reducing
nitrogen oxide present in the gas stream at a temperature in a
range of from about 275 degrees Celsius to about 350 degrees
Celsius in the chamber.
20. The method as defined in claim 19, wherein reducing nitrogen
oxide present in the gas stream occurs at a temperature, further,
that is less than about 325 degrees Celsius in the chamber.
21. The method as defined in claim 19, wherein reducing nitrogen
oxide present in the gas stream occurs at a temperature in the
range from about 300 degrees Celsius to about 325 degrees Celsius
in the chamber.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The invention includes embodiments that relate to a catalyst
composition. The invention includes embodiments that relate to a
method of making the catalyst composition and a method of using the
catalyst composition for reducing nitrogen oxides.
[0003] 2. Discussion of Art
[0004] Currently, lean NOx traps may be used in exhaust gas
treatment systems. In these, NOx reduction catalysts and methods
include the alkali and alkali earth metal in the catalyst
composition where the alkali metal or the alkali earth metal
absorbs the NOx and then the reductant reduces NOx to nitrogen.
This type of reaction may not have desirable kinetics.
[0005] Silver-containing alumina is known for selective catalytic
reduction (SCR) of NOx using linear hydrocarbon reductants.
However, reductants containing aromatics like those present in
Diesel fuel, lead to poor NOx reduction with concomitant carbon
deposition.
[0006] Therefore, it may be desirable to have a catalyst
composition with properties and characteristics that differ from
those properties of currently available compositions or catalysts.
It may be desirable to have a method that differs from those
methods currently available.
BRIEF DESCRIPTION
[0007] In one embodiment, a composition includes a templated metal
oxide substrate having a plurality of pores and a catalyst material
includes silver. The composition, under H.sub.2 at 30 degrees
Celsius, at a wavelength that is in a range of from about 350 nm to
about 500 nm has a visible-ultra-violet (VIS-UV) absorbance
intensity that is at least 20 percent less than a standard silver
alumina catalyst (Ag STD) having the same amount of silver by
weight. The standard alumina is Norton alumina.
[0008] In one embodiment, the catalyst composition is made by
reacting a metal alkoxide with a silver composition and a
templating agent to form a reaction product. The templating agent
is selected from a surfactant, cyclodextrin, crown ether, or a
mixture thereof. The reaction product is hydrolyzed to form a
hydrolyzed reaction product. The hydrolyzed reaction product is
condensed to form a templated substrate. The catalyst material
loading of the templated substrate can be controlled by controlling
the reacting, hydrolyzing and condensing steps. The metal alkoxide
is aluminum alkoxide and the aluminum alkoxide is selected from
aluminum methoxide, aluminum ethoxide, aluminum propoxide, or
aluminum butoxide.
[0009] In one embodiment, a method of using the catalyst
composition introduces a gas stream in a chamber having a
composition that includes both a templated metal oxide substrate
having a plurality of pores, and a catalyst material that includes
silver. The silver is present in an amount of at least about three
weight percent based on a total weight of the substrate. The
nitrogen oxide present in the gas stream is reduced at a
temperature in a range of from about 275 degree to about 450
degrees Celsius in the chamber in one embodiment. In another
embodiment, the nitrogen oxide present in the gas stream is reduced
at a temperature less than about 350 degrees Celsius in the
chamber.
DESCRIPTION OF FIGURES
[0010] FIG. 1 is a graph of low angle XRD scan;
[0011] FIG. 2 is an image of Scanning electron microscope (SEM) for
Ag-Templated Alumina;
[0012] FIG. 3 is an image of Scanning electron microscope (SEM) for
SBA 200 from SASOL;
[0013] FIG. 4 is an image of Scanning electron microscope (SEM) for
Norton Alumina;
[0014] FIG. 5 is a visible-ultra-violet spectra;
[0015] FIG. 6 is a visible-ultra-violet spectra;
[0016] FIG. 7 is a graphical representation of the average NOx
conversion and standard deviation;
[0017] FIG. 8 is a graphical representation of the average NOx
conversion and standard deviation.
DETAILED DESCRIPTION
[0018] The systems and methods described herein include embodiments
that relate to a catalyst composition, embodiments that relate to a
method of making the catalyst composition, and a method of using
the catalyst composition for reducing nitrogen oxides. Generally,
disclosed is a NOx reduction catalyst and NOx reduction system for
reducing NOx in exhaust gas discharged from a combustion device.
Suitable combustion devices may include furnaces, ovens or
engines.
[0019] As used herein, a catalyst is a substance that can cause a
change in the rate of a chemical reaction without itself being
consumed in the reaction. A slurry is a mixture of a liquid and
finely divided particles. A sol is a colloidal solution. A powder
is a substance including finely dispersed solid particles.
Templating refers to a controlled patterning and may include
molecular self-assembly; and, templated refers to determined
control of an imposed pattern. A monolith may be a ceramic block
having a number of channels, and may be made by extrusion of clay,
binders and additives that are pushed through a dye to create a
structure. Approximating language, as used herein throughout the
specification and claims, may be applied to modify any quantitative
representation that could permissibly vary without resulting in a
change in the basic function to which it is related. Accordingly, a
value modified by a term such as "about" is not to be limited to
the precise value specified. In some instances, the approximating
language may correspond to the precision of an instrument for
measuring the value. Similarly, "free" may be used in combination
with a term, and may include an insubstantial number, or trace
amounts, while still being considered free of the modified
term.
[0020] The substrate may include one or more of cordierite,
alumina, silica, or titania. Combinations may be useful, too, such
as silica-alumina. In other embodiments, other substrates may be
suitable and can be selected based on end-use parameters.
[0021] In addition to being templated, the substrate may be a
ceramic honeycomb or metal or metal compound substrate. With regard
to the templating, the substrate material may have a plurality of
pores that may have specific dimensions and periodicity. That is,
the templated metal oxide may have periodically arranged templated
pores of determined dimensions. The dimensions can include pore
diameter, degree of curvature, uniformity of the inner surface, and
the like. The average diameter of the pores may be greater than
about 2 nanometers. The average diameter of the pores may be less
than about 100 nanometers. In one embodiment, the average diameter
of the pores may be in a range from about 2 nanometers to about 20
nanometers, from about 20 nanometers to about 40 nanometers, from
about 40 nanometers to about 60 nanometers, from about 60
nanometers to about 80 nanometers, or from about 80 nanometers to
about 100 nanometers. The pores may have a periodicity greater than
about 50 Angstroms. The pores may have a periodicity less than
about 130 Angstroms. The pores may have a periodicity in the range
of from about 50 Angstroms to about 80 Angstroms, from about 80
Angstroms to about 100 Angstroms, from about 100 Angstroms to about
120 Angstroms, or from about 120 Angstroms to about 150
Angstroms.
[0022] FIG. 1 is a Low angle XRD scan for Ag-Templated Alumina
comprising 3 percent or 5 percent silver prepared via sol gel or
incipient wetness (IW) method. All samples calcined at 600 degrees
Celsius. The graph 10 shows that Ag-Templated Alumina (TA) has pore
dimensions of from 75-95 Angstroms depending on the method of
preparation. The graph 10 has peak 12 that denotes the average
pore-to-pore correlation of about 75 Angstroms and peak 14 denotes
the average pore-to-pore correlation of about 95 Angstroms.
[0023] The templated porous metal oxide substrate may have a
surface area that is greater than about 0.5 meter.sup.2/gram. In
one embodiment, the surface area is in a range of from about 0.5
meter.sup.2/gram to about 10 meter.sup.2/gram, from about 10
meter.sup.2/gram to about 100 meter.sup.2/gram, from about 100
meter.sup.2/gram to about 200 meter.sup.2/gram, or from about 200
meter.sup.2/gram to about 1200 meter.sup.2/gram. In one embodiment,
the porous substrate has a surface area that is in a range of from
about 0.5 meter.sup.2/gram to about 200 meter.sup.2/gram. In one
embodiment, the porous substrate has a surface area in a range of
from about 200 meter.sup.2/gram to about 250 meter.sup.2/gm, from
about 250 meter.sup.2/gram to about 500 meter.sup.2/gm, from about
500 meter.sup.2/gram to about 750 meter.sup.2/gm, from about 750
meter.sup.2/gram to about 1000 meter.sup.2/gm, from about 1000
meter.sup.2/gram to about 1250 meter.sup.2/gm, from about 1250
meter.sup.2/gram to about 1500 meter.sup.2/gm, from about 1500
meter.sup.2/gram to about 1750 meter.sup.2/gm, from about 1750
meter.sup.2/gram to about 2000 meter.sup.2/gm, or greater than
about 2000 meter.sup.2/gm.
[0024] SEM analysis of Ag-Templated Alumina (TA), FIG. 2 shows the
surface area and the pore structure. The SEM picture in FIG. 2 is
contrasted in FIG. 3 for SBA 200 with relatively lower surface area
and lower activity than Ag-TA and similarly for Norton alumina in
FIG. 4.
[0025] The templated porous metal oxide substrate may be present in
the catalyst composition in an amount that is greater than about 50
mole percent. In one embodiment, the amount of templated metal
oxide substrate may be present in a range of from about 50 mole
percent to about 60 mole percent, from about 60 mole percent to
about 70 mole percent, from about 70 mole percent to about 80 mole
percent, from about 80 mole percent to about 90 mole percent, from
about 90 mole percent to about 95 mole percent, from about 95 mole
percent to about 97 mole percent, based on the total amount of the
catalyst composition.
[0026] In one embodiment, the metal oxide is an aluminum oxide, but
other oxide support materials may also be considered. These other
support materials may include one or more of zirconium, silicon, or
titanium. Suitable support materials may include aluminosilicates,
aluminophosphates, hexaaluminates, zirconates, titanosilicates,
titanates, or a combination of two or more thereof.
[0027] The composition may also have a promoter for the catalytic
reaction of nitrogen oxide reduction. Non-limiting examples of the
catalyst may include various metals or metal oxides. The promoter
may include one or more of indium, gallium, tin, silver, manganese,
molybdenum, chromium, germanium, cobalt, nickel, gold, copper,
iron, and their oxides. In one embodiment, the promoter includes
silver.
[0028] In one embodiment, the catalyst material is free of one or
both of alkali metal and alkaline earth metal. In one embodiment,
the composition reduces NOx without absorbing the NOx on the
catalyst material. In this embodiment, the catalytic action is
distinct from the actions of a lean NOx trap. In one embodiment,
the composition is free of transition metal.
[0029] In one embodiment, the catalyst composition is made by
reacting a metal alkoxide with a silver composition and a
templating agent to form a reaction product. The templating agent
may be a surfactant. Other suitable templating agents may include
cyclodextrin or a crown ether. The reaction product may be
hydrolyzed to form a hydrolyzed reaction product. The hydrolyzed
reaction product may be condensed to form a templated substrate.
The catalyst material loading of the templated substrate may be
controlled, at least in part, by controlling the reacting,
hydrolyzing and condensing steps. The composition under H.sub.2 at
30 degrees Celsius, and at a wavelength that is in a range of from
about 350 nm to about 500 nm, has a VIS-UV absorbance intensity
that is at least 20 percent less than a standard silver alumina
catalyst (Ag STD). The standard alumina is Norton alumina that has
the same amount of silver by weight as the corresponding material
to which it is compared.
[0030] In one embodiment, the silver composition may be selected
from a group consisting of silver salt of inorganic acids, silver
salt of organic acids, and silver oxides. The silver may be present
in an amount of at least about three weight percent based on a
total weight of the substrate in one embodiment. In other
embodiments, the silver may be present in an amount of less than or
equal to about ten weight percent of a total weight of the
substrate.
[0031] In one method of making the catalyst, a metal alkoxide, a
silver composition and a templating agent may be mixed in a vessel
with a suitable solvent to form a reaction product. Initially, the
reaction product may be in the form of a sol. The sol may be
converted to a gel by the sol gel process. The gel may be subject
to one or more of filtration, washing, drying and calcinating to
yield a solid catalyst composition that includes the catalytic
metal disposed on a porous substrate.
[0032] The effect of iron on Ag-TA catalytic activity is tested by
varying the method by which silver is added to templated alumina
(TA). The alternative method for introducing silver or any other
element is called incipient wetness method whereby the precursor is
added to the hydrolyzed and condensed templated alumina as an
aqueous solution that wets the alumina followed by calcination.
Templated alumina with sol gel silver had relatively increased
activity for NOx reduction compared to templated alumina used with
incipient wetness (IW) silver. However, TA with IW silver at some
silver levels displayed catalytic activity similar to that for
Ag-TA sol gel. There are alternative methods of adding silver or
any other element in the templated alumina and those methods are
known as impregnation methods. In one embodiment, the incipient
wetness method is a type of impregnation method.
[0033] During the calcination process, the silver composition may
be reduced to a catalytic metal. The calcination may be conducted
at a temperatures in a range of from about 350 degrees Celsius to
about 400 degrees Celsius, from about 400 degrees Celsius to about
500 degrees Celsius, from about 500 degrees Celsius to about 600
degrees Celsius, from about 600 degrees Celsius to about 700
degrees Celsius, or from about 700 degrees Celsius to about 800
degrees Celsius. In one embodiment, the calcination may be
conducted at a temperature of about 550 degrees Celsius. The
calcination may be conducted for a time period of from about 10
minutes to about 30 minutes, from about 30 minutes to about 60
minutes, from about 60 minutes to about 1 hour, from about 1 hour
to about 10 hours, from about 10 hours to about 24 hours, or from
about 24 hours to about 48 hours.
[0034] Suitable solvents may include aprotic polar solvents, polar
protic solvents, and non-polar solvents. Suitable aprotic polar
solvents may include propylene carbonate, ethylene carbonate,
butyrolactone, acetonitrile, benzonitrile, nitromethane,
nitrobenzene, sulfolane, dimethylformamide, N-methylpyrrolidone, or
the like. Suitable polar protic solvents may include water,
nitromethane, acetonitrile, and short chain alcohols. Suitable
short chain alcohols may include one or more of methanol, ethanol,
propanol, isopropanol, butanol, or the like. Suitable non-polar
solvents may include benzene, toluene, methylene chloride, carbon
tetrachloride, hexane, diethyl ether, or tetrahydrofuran.
Co-solvents may also be used. Ionic liquids may be used as solvents
during gelation. Exemplary solvents may include 2-butanol and
2-propanol.
[0035] Selection of the type(s) and amounts of the templating agent
may affect or control the pore characteristics of the resultant
templated substrate. Suitable templating agents may include one or
more surfactants. Suitable surfactants may include cationic
surfactants, anionic surfactants, non-ionic surfactants, or
Zwitterionic surfactants. In one embodiment, the templating agent
may include one or more cyclic species. Examples of such cyclic
species may include cyclodextrin and crown ether.
[0036] Suitable cationic surfactants may include cetyltrimethyl
ammonium bromide (CTAB), cetylpyridinium chloride (CPC),
polyethoxylated tallow amine (POEA), benzalkonium chloride (BAC),
and benzethonium chloride (BZT). Other suitable cationic
surfactants may include those having a chemical structure denoted
by CH.sub.3(CH.sub.2).sub.15N(CH.sub.3).sub.3--Br,
CH.sub.3(CH.sub.2).sub.15--(PEO)n-OH where n=2 to 20 and where PEO
is polyethylene oxide, CH.sub.3(CH.sub.2).sub.14COOH and
CH.sub.3(CH.sub.2).sub.15NH.sub.2. Other suitable cationic
surfactants may include one or more fluorocarbon surfactants, such
as
C.sub.3F.sub.7O(CFCF.sub.3CF.sub.2O).sub.2CFCF.sub.3--CONH(CH.sub.2).sub.-
3N(C.sub.2H.sub.5).sub.2CH.sub.31), which is commercially available
as FC-4.
[0037] Suitable anionic surfactants may include one or more of
sodium dodecyl sulfate (SDS), ammonium lauryl sulfate, alkyl
sulfate salts, sodium laureth sulfate also known as sodium lauryl
ether sulfate (SLES), alkyl benzene sulfonate, soaps, fatty acid
salts, or sodium dioctyl sulfonate (AOT). Suitable Zwitterionic
surfactants may include dodecyl betaine, dodecyl dimethylamine
oxide, cocamidopropyl betaine, or coco ampho-glycinate.
[0038] Nonionic surfactants may have polyethylene oxide molecules
as hydrophilic groups. Suitable ionic surfactants may include alkyl
poly(ethylene oxide), copolymers of poly(ethylene oxide) and poly
(propylene oxide) commercially called Poloxamers or Poloxamines and
commercially available under the trade name PLURONICS from the BASF
company.
[0039] Suitable non-ionic surfactants may include one or more alkyl
polyglucosides; octylphenol ethoxylate; decyl maltoside; fatty
alcohols; cetyl alcohol; oleyl alcohol; cocamide monoethanolamine;
cocamide diethanolamine; cocamide triethanolamine;
4-(1,1,3,3-tetramethyl butyl) phenyl-poly (ethylene glycol);
polysorbitan monooleate; or amphiphilic poly (phenylene ethylene)
(PPE). Suitable poly glucosides may include octyl glucoside. Other
suitable non-ionic surfactants may include long-chain alkyl amines,
such as primary alkylamines and N,N-dimethyl alkylamines. Suitable
primary alkylamines may include dodecylamine and hexadecylamine.
Suitable N,N-dimethyl alkylamines may include N,N-dimethyl
dodecylamine or N,N-dimethyl hexadecylamine. Suitable non-ionic
surfactant may include (1,1,3,3-Tetramethylbutyl)
phenyl-polyethylene glycol, which is commercially available as
TRITON X-114 from the Sigma-Aldrich company.
[0040] In one embodiment, the templating agent may include
cyclodextrin. Cyclodextrins may include cyclic oligosaccharides
that include 5 or more .alpha.-D-glucopyranoside units linked 1 to
4, as in amylose (a fragment of starch). Suitable cyclodextrins in
the templating agent may include 5-membered to about 150-membered
cyclic oligosaccharides. Exemplary cyclodextrins include a number
of glucose monomers ranging from six to eight units in a ring.
Suitable cyclodextrins are .alpha.-cyclodextrin, a six-membered
sugar ring molecule; .beta.-cyclodextrin, a seven sugar ring
molecule; .gamma.-cyclodextrin, an eight sugar ring molecule; or
the like.
[0041] As noted above, the templating agent may include crown
ethers. Crown ethers are heterocyclic chemical compounds that
include a ring containing several ether groups. Suitable crown
ethers may include oligomers of ethylene oxide, the repeating unit
being ethyleneoxy, i.e., --CH2CH2O--. Useful members of this series
may include the tetramer (n=4), the pentamer (n=5), and the hexamer
(n=6). Crown ethers derived from catechol may be used in the
templating agent. Crown ethers that strongly bind certain types of
cations to form complexes may be included in the templating agents.
The oxygen atoms in the crown ether may coordinate with a cation
located at the interior of the ring, whereas the exterior of the
ring may be hydrophobic. For example, 18-crown-6 has high affinity
for potassium cation, 15-crown-5 for sodium cation, and 12-crown-4
for lithium cation.
[0042] In one embodiment, a method of using the catalyst
composition introduces a gas stream in a chamber having the
composition that includes a templated metal oxide substrate having
a plurality of pores, and a catalyst material comprising silver
that is present in an amount of at least about three weight percent
based on a total weight of the substrate. The nitrogen oxide
present in the gas stream may be reduced at a temperature of about
275 degrees Celsius or greater. In one embodiment, the reduction
may occur at a temperature range of from about 275 degrees Celsius
to about 300 degrees Celsius, from about 300 degrees Celsius to
about 325 degrees Celsius, or from about 325 degrees Celsius to
about 350 degrees Celsius. The nitrogen oxide present in the gas
stream may be reduced at a temperature of less than about 350
degrees Celsius in the chamber.
EXAMPLES
Preparation of Material
[0043] Templated alumina is produced as follows, for example.
Solution 1 is formed by combining ethylaetoacetate (26.5 g, 0.2
mol), TRITON X-114 (85g, ca. 0.15 mol) and 2-butanol (500 mL) in a
5-L, 3-neck flask equipped with an addition funnel, a condenser,
and a mechanical stirrer. Solution 2 is composed of
Al(O-secBu).sub.3 (500 g, 2 mol) and 2-BuOH (2 L). Solution 3 is
composed of water (75 mL, 4 mol) and 2-BuOH (850 mL).
[0044] Solution 2 is added to Solution 1 while stirring, and is
held at ambient temperature for 30 min. Solution 3 is added to
solutions 1 and 2 via an addition funnel over about 90 minutes.
Mechanical stirring is continued at ambient temperature for 3 hours
and then the contents are heated to about reflux for about 20 to
about 24 hours.
[0045] The contents are cooled and filtered on a #50 paper filter
and washed with ethanol. The obtained white solid is dried in
vacuo, in a vacuum oven at 80 degrees Celsius. The solid is
subjected to Soxhlet extraction with ethanol for 20-24 hours. The
solid is dried in a vacuum oven at 80 degrees Celsius, to yield 164
grams. The dry material is heated under N.sub.2 in a tube furnace
from room temperature to 550 degrees Celsius at a heating rate of 2
degrees Celsius/minute, maintained at 550 degrees Celsius for 1 hr
and is calcined in a flow of air at 550 degrees Celsius for 5
hours.
Process for Forming Templated Support with Catalyst Material:
[0046] A 5 L, 3-necked flask equipped with a mechanical stirrer, a
reflux condenser and an addition funnel, is charged with TRITON
X114 (68.7 g, 0.16 mol) and ethylacetoacetate (13.2 g, 0.1 mol) in
250 mL of 2-propanol. Then Al(O.sup.secBu).sub.3 (249.8 g, 1.02
mol) in 1 L 2-propanol is added and the contents are stirred for 30
minutes. An amount of AgNO.sub.3 is dissolved in water (37 mL, 2.06
mol). The amount of silver nitrate is changed as noted below to
create a number of reaction products. The solution is combined with
500 mL 2-propanol and is charged to an addition funnel. The
contents of the addition funnel are added to a 5 Liter flask over
the course of 75 minutes. The stirred solution is refluxed for 24
hours. After cooling, the contents are filtered and washed with
about 250 mL of ethanol to obtain a semi-dried mass. The semi-dried
mass is subjected to Soxhlet extraction with ethanol for 24 hours
and then oven-vacuum dried at 30 mmHg for 24 hours to obtain a
solid. The obtained brown solid is calcined under nitrogen in a
tube furnace to 550 degrees Celsius at a heating rate of 2 degrees
Celsius/minute to obtain a reaction product.
[0047] The amount of AgNO.sub.3 (2.6 g, 0.0158 mol) for Catalyst
Product 1, results in 3 percent silver templated alumina catalyst
composition. The amount of AgNO.sub.3 (3.463 g, 0.0204 mol) for
Catalyst Product 2, results in 4 percent silver templated alumina
catalyst composition. The amount of AgNO.sub.3 (4.407 g, 0.0259
mol) for Catalyst Product 3, results in 5 percent silver templated
alumina catalyst composition. The amount of AgNO.sub.3 (5.383 g,
0.0317 mol) for Catalyst Product 4, results in 6 percent silver
templated alumina catalyst composition. The amount of AgNO.sub.3
(6.391 g, 0.0376 mol) for Catalyst Product 5, results in 7 percent
silver templated alumina catalyst composition. The amount of
AgNO.sub.3 (7.49 g, 0.0441 mol) for Catalyst Product 6, results in
8 percent silver templated alumina catalyst composition. The amount
of AgNO.sub.3 (8.443 g, 0.0497 mol) for Catalyst Product 7, results
in 9 percent silver templated alumina catalyst composition.
[0048] Catalyst Product 8--Templated Alumina with 8 percent Silver
having a different solvent: A 5 L 3-neck round bottom flask
equipped with a mechanical stirrer, reflux condenser, and addition
funnel is charged with ethyl acetoacetate (13.26 g, 0.1019 mol),
TRITON X114 (69.73 g, 0.1117 mol) and 250 mL of 2-Butanol. The
stirrer is then turned on low. Aluminum sec-butoxide (250.96 g,
1.0188 mol) is dissolved in 1 Liter of 2-BuOH and transferred to
the 5 L flask. This reaction mixture is stirred under ambient
conditions for 30 minutes. AgNO.sub.3 (7.49 g, 0.0441 mol) is
dissolved in 37.5 mL of distilled H.sub.2O and then combined with
425 mL of 2-BuOH to produce a transparent, clear solution. This
solution is added via dropping funnel to the 5 L flask. The stir
speed is adjusted to account for changing viscosity of the fluid,
water addition occurred over the course of 2-3 hours. The mixture
is aged at 95 degrees Celsius for 24 hours.
[0049] Two different processes are carried out with the obtained
slurry. 1.) Alumina-water slurry. Distilled water (1.47 L) is added
to the flask in order to remove butanol via azeotropic distillation
(bp ca. 87 degrees Celsius) and to yield a water slurry of 5
percent solids. 2.) Extracted Solid. The obtained slurry described
above is filtered through a #50 filter paper on a Buchner funnel,
washed with ethanol and then the obtained solid is extracted with
ethanol in a Soxhlet apparatus. The solid is dried in a vacuum oven
at 80 degrees Celsius, yield 164 g. The dry material is heated
under N.sub.2 in a tube furnace from room temperature to 550
degrees Celsius at a heating rate of 2 degrees Celsius/min,
maintained at 550 degrees Celsius for 1 hr and calcined in a flow
of air at 550 degrees Celsius for 5 hours to get Catalyst Product
8.
[0050] FIG. 5 is a graph that plots VIS-UV absorbance intensity at
different wavelengths. The plot compares the Comparative Ag STD, Ag
TA (sol-gel) and Ag TA (impregnated), all having the same Ag
percent. The test conditions are under H.sub.2 at 30 degrees
Celsius (spectra have been subtracted with the ones from fresh
catalyst under He at 30 degrees Celsius). The Ag TA (sol-gel) is a
silver templated alumina catalyst made by the sol gel process and
Ag TA (impregnated) is a silver templated alumina catalyst made by
the impregnation process. Particularly, Curve 16 is a comparative
plot for 8 percent Ag with standard Norton alumina under H.sub.2 at
30 degrees Celsius. Curve 18 is a plot for 8 percent Ag with
templated alumina made by sol gel method under H.sub.2 at 30
degrees Celsius (Catalyst Product 8). Curve 20 is a plot for 8
percent Ag with templated alumina made by impregnation method under
H.sub.2 at 30 degrees Celsius. In FIG. 5, curve 16 indicates the
amount of silver ion (Ag.sup.+) agglomeration, the peak is
identified with reference number 22, silver (Ag) cluster
agglomeration, peak 24, and Ag particles agglomeration, peak
26.
[0051] FIG. 6 is a graph that plots VIS-UV absorbance intensity at
different wavelengths. Curve 28 is a comparative plot for 8 percent
Ag with standard Norton alumina under H.sub.2 at 300 degrees
Celsius. Curve 30 is a plot for 8 percent Ag with templated alumina
made by sol gel method under H.sub.2 at 300 degrees Celsius
(Catalyst Product 6). Curve 32 is a plot for 8 percent Ag with
templated alumina made by impregnation method under H.sub.2 at 300
degrees Celsius. For the standard silver alumina catalyst (curve
18) the agglomeration is very high whereas for the silver templated
alumina catalyst the agglomeration is low, showing the relatively
different properties with regard to the silver templated alumina
catalyst.
[0052] With respect to FIG. 6 the graph that shows the Catalyst
Product 6 is having a VIS-UV absorbance intensity that is at least
20 percent less than a comparative silver alumina catalyst (Ag
STD). The standard alumina is Norton alumina, and which has the
same amount of silver by weight, at a wavelength in a range of from
about 350 nm to about 500 nm, under H.sub.2 at 30 degrees
Celsius.
[0053] Catalyst Product 6 has a visible-ultra-violet (VIS-UV)
absorbance intensity that is at least 20 percent less than a
standard silver alumina catalyst (Ag STD), under H.sub.2 at 30
degrees Celsius and at a wavelength that is in a range of from
about 350 nanometers (nm) to about 500 nm. The standard alumina is
Norton alumina, and has the same amount of silver by weight as the
instant composition. FIGS. 5 and 6 indicate an amount of silver
(Ag) agglomeration (Ag particles and mainly Ag clusters) and silver
ion (Ag.sup.+) agglomeration. For the standard silver alumina
catalyst, the agglomeration is relatively high, whereas for the
silver templated alumina catalyst the agglomeration is relatively
low. The agglomeration level affects, and possibly controls, the
function and efficacy of the corresponding material.
High Throughput Screening (HTS) Reactor:
[0054] The reactor mixes gases (using mass flow controllers--MFCs,
Brooks and MKS) and up to two liquids (usually water and a liquid
reductant) which are vaporized. The water and liquid reductant are
pumped in under pressure. The gas mixture enters the heated
(.about.115 degrees Celsius) top box and goes into a manifold that
contains 32 capillary exit tubes. The gas is restricted in the
manifold and the pressure builds up to .about.60 psi. Backpressure
indicates the same amount of gas is flowing out of each capillary.
The capillaries (stainless steel) open up into tubes (INCONEL,
stainless steel) where the catalyst is positioned. This zone is a
copper block that can be temperature controlled.
[0055] The catalyst powders (25-50 mg) are held in place by quartz
wool that has been wedged into the tube. Each tube can be
individually sampled by controlling the two switching valves. The
flow of the outlet stream is measured and recorded. The flow can be
diverted through a deep oxidation catalysts (Pt/Al.sub.2O.sub.3
from Johnson Matthey) to determine N.sub.2 selectivity. The flow
then passes through a diluter (CAI, Model 701) that takes 25 ml/min
from the reactor (which generally puts out .about.35-40 mL/min) and
mixes it with 1000 m/min house N.sub.2 (.about.25:1 dilution). The
diluted sample is pulled though the CO/CO.sub.2 detector (CAI) by a
pump in the NO.sub.x detector (CAI, Model 600 HCLD). The NO.sub.x
value is recorded. It is possible to record the NO and NO.sub.2
values separately. A LABVIEW program controls many features of the
reactor system. The MFCs are not controlled by the software but
their settings are recorded. The software controls the temperature
of the reactor block and the switching of the values. The software
records amount CO, CO.sub.2 and NO.sub.x from the analyzers. The
reductant delivery is checked by measuring CO.sub.2 level, after
the feed is completely combusted over the Deep Oxidation Catalyst
(DOC).
[0056] The screening conditions are as follows: gas composition: 12
percent O.sub.2, 600 ppm nitrogen oxide (NO), 7 percent H.sub.2O, 1
ppm SO.sub.2 and the balance N.sub.2. The catalysts are pretreated
with 7 percent H.sub.2O and 50 ppm SO.sub.2, 12 percent O.sub.2 for
7 hours at 450 degrees Celsius to "age" or sulfur soak the
catalysts. The reductant used is a liquid mixture composed of:
2,2,4 Trimethylpentane (64 weight percent), octane (7 weight
percent) and toluene (29 weight percent), also known as Moctane.
Another liquid reductant used in a few experiments is a
distillation cut (<210 degrees Celsius) of ultra low sulfur
diesel (ULSD) fuel. For all the experiments mentioned using the HTS
reactor, the C1:NO ratio used is 8 (C1:NO is defined as the number
of carbon atoms in the reductant stream per number of NO
molecules).
[0057] Each run examines the catalysts at three different
temperatures 275 degrees Celsius, 375 degrees Celsius and 425
degrees Celsius and the catalysts are tested in triplicates. Data
is presented as percent NOx conversion by measuring the NO.sub.x
concentration through tube #1 with no catalyst present and then
measuring the NO.sub.x concentration over the other tubes with
catalysts and determining the percent change.
[0058] The catalysts screened in the 32-tube reactor are prepared
by incipient wetness impregnation of the sized support (425-710
nanometers) with a silver nitrate (AgNO.sub.3) solution. The volume
of the AgNO.sub.3 solution used is twice the pore volume of the
support and contained the correct number of moles of Ag to hit the
target mole percent. The pore volume of the support is obtained
from the BET measurement report. In one condition of the
experiment, the catalysts containing 2 mole percent Ag on Norton
alumina is called AgSTD and is present in runs as a control. The
impregnated materials are dried in a vacuum oven at 80 degrees
Celsius and then calcined in air at 600 degrees Celsius for 6 hours
in a box furnace.
[0059] The prepared catalysts are weighed out (.about.50 mg) and
placed in 2 ml GC vials until used in the reactor. The exact weight
of each catalyst is measured using a Bohdan weighing robot.
Scale-up Reactor:
[0060] The experimental setup is described in brief. The catalyst
to be tested is installed in a quartz-tube reactor (19 mm I.D.)
located inside a furnace. Temperature, pressure, space velocity
over the catalyst, and gas composition at the inlet of the reactor
are controlled. This reactor is fully automated and experimental
test matrix can be run over an extended period of time (days or
weeks). Analytical lines allow for the measurement of NO, NO.sub.2
(chemiluminescence detector), CO, CO.sub.2 (IR detector), and
SO.sub.2 (UV-Vis detector). Also, a deep oxidation catalytic bed
located before the analytical lines can be either flown through or
by-passed. When by-passed, the NOx concentration measured
(NO+NO.sub.2) is referred to as "NOx concentration". When flown
through the Deep Oxidation Catalyst (DOC, Johnson-Matthey catalyst,
Pt/Al.sub.2O.sub.3, SV<20000 hr.sup.-1, T=450 degrees Celsius),
the NOx concentration measured (NO+NO.sub.2) is referred to as "NOt
concentration". Therefore, the difference between those two values
(NOx concentration-NOt concentration) corresponds to the quantity
of NOx species that reacted in the quartz-tube reactor to form new
chemicals, which are oxidized back to NO or NO.sub.2 in the DOC.
These nitrogen-containing species are called RONOs. RONOs are
unidentified by-products of the SCR reaction of NOx to
nitrogen.
[0061] Catalysts are tested under experimental conditions reported
in Table 1. The total powder catalyst weight is 2.7 grams. The
total volumetric flow rate over the catalyst is 3 SLPM.
[0062] The powder bed is placed at least 24'' from the inlet of the
quartz tube to allow for preheating of the feed gas. The powder bed
is packed between two 0.5 grams plugs of quartz wool.
TABLE-US-00001 TABLE 1 Experimental Conditions X's Values NO (ppm)
475, 610, 690 O.sub.2 (percent) 12 C1:NO ratio 6 H.sub.2:NO ratio
0, 3:1 H.sub.2O (percent) 7 Temperature (degrees Celsius) 275, 375,
430 SO.sub.2 (ppm) 0 CO (ppm) 250 CO.sub.2 (percent) 0
[0063] Moctane, Ethylene+Propylene (C2_C3), Ultra Low Sulfur Diesel
(ULSD) and Diesel Fraction 1 are used as reductants. Liquid
reductants are pumped by a HPLC pump (ASI model 500G) and
vaporized/diluted at 300 degrees Celsius with nitrogen before being
injected in the reactor. Gaseous reductants are metered and
delivered with Mass Flow Controllers (MFCs). The amount of
reductant injected is quantified by deep oxidation on
Pt/Al.sub.2O.sub.3 catalyst at 450 degrees Celsius (space velocity
below 20,000 hr.sup.-1) followed by the measurement of CO.sub.2
concentration in the gas stream. The assumption that full catalytic
combustion of the reductants takes place is validated by the fact
that very low CO concentrations are measured. In addition, deep
oxidation of reductants provided the C1 (ppm of molecular carbon)
equivalent number (equal to CO.sub.2 concentration, in ppm), which
allows for the computation of the C1/NO ratio.
[0064] FIG. 7 is a graphical representation of the average NOx
conversion and the standard deviation at 325 degrees Celsius using
catalyst of templated alumina with silver loading of 2 percent, 3
percent, 4 percent, 5 percent, 6 percent, 7 percent, 8 percent, and
9 percent. FIG. 8 is a graphical representation of the average NOx
conversion and the standard deviation at 325 degrees Celsius using
Norton alumina with silver loading 2 percent, 3 percent, 4 percent,
5 percent, 6 percent, 7 percent, 8 percent, and 9 percent.
[0065] As used herein, the terms "may" and "may be" indicate a
possibility of an occurrence within a set of circumstances; a
possession of a specified property, characteristic or function;
and/or qualify another verb by expressing one or more of an
ability, capability, or possibility associated with the qualified
verb. Accordingly, usage of "may" and "may be" indicates that a
modified term is apparently appropriate, capable, or suitable for
an indicated capacity, function, or usage, while taking into
account that in some circumstances the modified term may sometimes
not be appropriate, capable, or suitable.
[0066] Reference is made to substances, components, or ingredients
in existence at the time just before first contacted, formed in
situ, blended, or mixed with one or more other substances,
components, or ingredients in accordance with the present
disclosure. A substance, component or ingredient identified as a
reaction product, resulting mixture, or the like may gain an
identity, property, or character through a chemical reaction or
transformation during the course of contacting, in situ formation,
blending, or mixing operation if conducted in accordance with this
disclosure with the application of common sense and the ordinary
skill of one in the relevant art (e.g., chemist). The
transformation of chemical reactants or starting materials to
chemical products or final materials is a continually evolving
process, independent of the speed at which it occurs. Accordingly,
as such a transformative process is in progress there may be a mix
of starting and final materials, as well as intermediate species
that may be, depending on their kinetic lifetime, easy or difficult
to detect with current analytical techniques known to those of
ordinary skill in the art.
[0067] Reactants and components referred to by chemical name or
formula in the specification or claims hereof, whether referred to
in the singular or plural, may be identified as they exist prior to
coming into contact with another substance referred to by chemical
name or chemical type (e.g., another reactant or a solvent).
Preliminary and/or transitional chemical changes, transformations,
or reactions, if any, that take place in the resulting mixture,
solution, or reaction medium may be identified as intermediate
species, master batches, and the like, and may have utility
distinct from the utility of the reaction product or final
material. Other subsequent changes, transformations, or reactions
may result from bringing the specified reactants and/or components
together under the conditions called for pursuant to this
disclosure. In these other subsequent changes, transformations, or
reactions the reactants, ingredients, or the components to be
brought together may identify or indicate the reaction product or
final material.
[0068] In describing, the products of the instant invention as a
reaction product of initial materials reference is made to the
initial species recited and it is to be noted that additional
materials may be added to the initial mixture of synthetic
precursors. These additional materials may be reactive or
non-reactive. The defining characteristic of the instant invention
is that the reaction product is obtained from the reaction of at
least the components listed as disclosed. Non-reactive components
may be added to the reaction mixture as diluents or to impart
additional properties unrelated to the properties of the
composition prepared as a reaction product. Additional reactive
components may be added; such components may react with the initial
reactants or they may react with the reaction product; the phrase
"reaction product" is intended to include those possibilities as
well as including the addition of non-reactive components.
[0069] The embodiments described herein are examples of composition
and methods having elements corresponding to the elements of the
invention recited in the claims. This written description may
enable those of ordinary skill in the art to make and use
embodiments having alternative elements that likewise correspond to
the elements of the invention recited in the claims. The scope of
the invention thus includes articles, systems and methods that do
not differ from the literal language of the claims, and further
includes other articles, systems and methods with insubstantial
differences from the literal language of the claims. While only
certain features and embodiments have been illustrated and
described herein, many modifications and changes may occur to one
of ordinary skill in the relevant art. The appended claims cover
all such modifications and changes.
* * * * *