U.S. patent application number 15/802971 was filed with the patent office on 2018-05-03 for surface-modified carbon and sorbents for improved efficiency in removal of gaseous contaminants.
The applicant listed for this patent is Columbus Industries, Inc.. Invention is credited to Vivekanand Gaur.
Application Number | 20180117522 15/802971 |
Document ID | / |
Family ID | 62020863 |
Filed Date | 2018-05-03 |
United States Patent
Application |
20180117522 |
Kind Code |
A1 |
Gaur; Vivekanand |
May 3, 2018 |
Surface-Modified Carbon and Sorbents for Improved Efficiency in
Removal of Gaseous Contaminants
Abstract
A material, and filters and other structures exposed to flowing
gas that have the material therein, which removes VOCs, such as
formaldehyde, from the gas. The material is a porous sorbent
impregnated by a metal oxide, such as manganese oxide (MnOx) nano
particles. The sorbent may be activated carbon, and the manganese
oxide may catalyze formaldehyde to water and carbon dioxide while
the carbon may adsorb formaldehyde, both mechanisms of which remove
the VOC from the air to prevent or reduce inhalation of the same by
humans. The material may be combined with an untreated sorbent or
sorbent treated with ionic alkaline salts.
Inventors: |
Gaur; Vivekanand; (Dublin,
OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Columbus Industries, Inc. |
Ashville |
OH |
US |
|
|
Family ID: |
62020863 |
Appl. No.: |
15/802971 |
Filed: |
November 3, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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62416899 |
Nov 3, 2016 |
|
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|
62463144 |
Feb 24, 2017 |
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62422943 |
Nov 16, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D 2259/4508 20130101;
B01J 20/28023 20130101; B01D 53/8668 20130101; B01D 53/72 20130101;
B01D 2253/102 20130101; B01J 20/3238 20130101; Y02A 50/20 20180101;
B01J 20/28004 20130101; B01J 20/324 20130101; B01D 53/02 20130101;
Y02A 50/235 20180101; B01J 20/3236 20130101; B01D 2255/2073
20130101; B01D 2101/02 20130101; B01D 2258/06 20130101; B01D
2253/25 20130101; B01D 2257/708 20130101 |
International
Class: |
B01D 53/02 20060101
B01D053/02; B01D 53/72 20060101 B01D053/72; B01J 20/28 20060101
B01J020/28; B01J 20/32 20060101 B01J020/32 |
Claims
1. A material for reacting with volatile organic compounds in a
flow of gas, the material comprising a porous sorbent impregnated
with metal oxide particles in at least pores formed on an outer
surface of the porous sorbent.
2. The material in accordance with claim 1, wherein the porous
sorbent further comprises zeolite and the metal oxide particles
further comprise manganese oxide (MnOx).
3. The material in accordance with claim 2, wherein the manganese
oxide particles are in a range of 0.5-2.0% by weight of the
zeolite.
4. The material in accordance with claim 1, wherein the porous
sorbent further comprises activated carbon and the metal oxide
particles further comprise manganese oxide (MnOx).
5. The material in accordance with claim 4, wherein the manganese
oxide particles are within a size range of about 100 to about 400
nanometers.
6. The material in accordance with claim 4, wherein the activated
carbon has a surface area per unit mass of between about 800 to
about 1,300 square meters per gram.
7. The material in accordance with claim 4, wherein the activated
carbon size is within a range of between about 10 microns and about
4.0 millimeters.
8. The material in accordance with claim 4, wherein the manganese
oxide particles are in a range of 0.5-5.0% by weight of the
carbon.
9. A material for reacting with volatile organic compounds in a
flow of gas, the material comprising: (a) a first porous sorbent
impregnated with metal oxide particles in at least pores formed on
an outer surface of the first porous sorbent; and (b) a second
porous sorbent impregnated with ionic alkaline salts in at least
pores formed on an outer surface of the second porous sorbent.
10. The material in accordance with claim 9, wherein the first
porous sorbent further comprises zeolite, the metal oxide particles
further comprise manganese oxide (MnOx), the second porous sorbent
further comprises zeolite and the ionic alkaline salts further
comprise a potassium ion.
11. The material in accordance with claim 10, wherein the first
porous sorbent constitutes about 40-50% by weight and the second
porous sorbent constitutes about 50-60% by weight.
12. The material in accordance with claim 9, wherein the first
porous sorbent further comprises activated carbon, the metal oxide
particles further comprise manganese oxide (MnOx), the second
porous sorbent further comprises activated carbon and the ionic
alkaline salts further comprise a potassium ion.
13. The material in accordance with claim 12, wherein the first
porous sorbent constitutes about 40-50% by weight and the second
porous sorbent constitutes about 50-60% by weight.
14. A filter media for removing at least volatile organic compounds
from a flow of gas in which the filter media is placed, the filter
media comprising a first porous sorbent impregnated with metal
oxide particles in at least pores formed on an outer surface of the
first porous sorbent.
15. The material in accordance with claim 14, wherein the first
porous sorbent further comprises zeolite and the metal oxide
particles further comprise manganese oxide (MnOx).
16. The material in accordance with claim 14, wherein the first
porous sorbent further comprises activated carbon and the metal
oxide particles further comprise manganese oxide (MnOx).
17. The filter media in accordance with claim 16, wherein the first
porous sorbent is mounted to a gas-permeable panel.
18. The filter media in accordance with claim 17, wherein the
gas-permeable panel is adjacent a fibrous web.
19. The filter media in accordance with claim 16, wherein the first
porous sorbent is mounted to a fibrous web.
20. The filter media in accordance with claim 19, further
comprising a second porous sorbent impregnated with ionic alkaline
salts in at least pores formed on an outer surface of the porous
sorbent.
21. The filter media in accordance with claim 20, wherein the ionic
alkaline salts further comprise potassium ions.
22. The filter media in accordance with claim 21, wherein the first
porous sorbent constitutes about 40-50% by weight and the second
porous sorbent constitutes about 50-60% by weight.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/416,899 filed Nov. 3, 2016; U.S. Provisional
Application No. 62/463,144 filed Feb. 24, 2017; and U.S.
Provisional Application No. 62/422,943 filed Nov. 16, 2016. The
above prior applications are hereby incorporated by reference.
STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH AND
DEVELOPMENT
[0002] (Not Applicable)
THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT
[0003] (Not Applicable)
REFERENCE TO AN APPENDIX
[0004] (Not Applicable)
BACKGROUND OF THE INVENTION
[0005] The invention relates generally to materials used to remove
contaminants from a gas, and more particularly to materials used to
remove contaminant gases, such as aldehydes, from air.
[0006] Aldehydes are highly reactive organic compounds, and include
formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde,
benzaldehyde, cinnamaldehyde, tolualdehyde, and retinaldehyde,
among others. Formaldehyde is harmful if inhaled by humans at
sufficient levels and is considered a volatile organic compound, or
VOC. Aldehydes are sometimes found in air around newly manufactured
polymers, which are present in residential buildings. It is
therefore desirable to remove aldehydes from air in residential
buildings.
[0007] One common way of removing contaminants from the air in a
residential building, such as a house, is to treat a filter used in
the central heating and cooling system of the house with materials
that will adsorb contaminants from the air as it is circulated
through the house. Such heating and cooling systems are known to
use a fan to move air into each room of the home while
simultaneously drawing air out of most or all of the same rooms. In
this manner, air is circulated through the central system and while
the filter strains out and/or otherwise removes particulate from
the air, the treatment materials adsorb the contaminant gas
molecules from the air as the air passes through the filter.
[0008] Prior art filters have included activated carbon treated for
an adsorptive (physisorption or chemisorption) mechanism to filters
used in the central heating and cooling system of building. These
filters use carbon in large mesh size or in pellet form to adsorb
contaminants, such as formaldehyde. Thus, the prior art removes
formaldehyde by carbon treated for adsorptive mechanisms. It is
desirable to remove more formaldehyde, or remove formaldehyde at
faster rates, in order to reduce the negative impact of
formaldehyde on the occupants of any building.
BRIEF SUMMARY OF THE INVENTION
[0009] Disclosed herein are activated carbon and other porous
sorbents with surface modifications, which may be carried out by
impregnation with transition metals, metal oxides and complexes.
These surface-modified porous sorbents receive the metal oxides in
their pores and may be placed in contact with room air, such as by
being added to an HVAC filter. This results in higher adsorption of
VOCs, and in catalytic activity in the oxidation of VOCs, and
especially formaldehyde, in the air passing through the filter or
other air-contacting structure, thereby removing the VOCs from the
air stream that will be breathed by the occupants of the
building.
[0010] Activated carbon is one contemplated porous sorbent, as are
titania, molecular sieves, zeolites and alumina. Activated carbon
may be impregnated with MnOx-based nano particles, which may be
previously prepared or prepared in-situ, to give an additional
mechanism of catalytic oxidation of VOCs, such as formaldehyde and
other aldehydes. This combination of MnOx nano particles and
activated carbon has a higher capacity for oxidation at faster
kinetics, which results in higher filtration efficiency and longer
filter life. Porous substrates in addition to activated carbon may
be impregnated with Manganese-based particles and/or nanoparticles,
including, without limitation, zeolite.
[0011] Also disclosed herein is a fibrous structure, such as a
woven sheet, a non-woven batt, or a web of fibers, which may be
polymeric. The fibrous structure may have a coating of metal oxide
and ionic suspensions that create catalytic sites on the fibrous
structure. This fibrous structure may be placed in a frame and
installed as a filter in a central heating and cooling system. It
is contemplated to use the resulting filtration media as air
filtration media for the oxidation of volatile organic compounds
(VOC), especially formaldehyde, in an air stream. This may be
accomplished by placing the media in a frame in a duct formed in
the air path of a heating, air conditioning and ventilation (HVAC)
system of a building, which can be a home, apartment building,
office building, factory, or any other structure. The polymeric web
coated with catalytic nano metal oxide (e.g., manganese oxide) has
enhanced efficiency in the removal of molecular gas and/or VOCs by
adsorption and catalysis of the contaminant into less-harmful
substances.
[0012] A polymeric web media may be coated with nano-sized
manganese oxide and potassium ions. The filtration media may be
used alone, or in combination with activated carbon, in an HVAC
system. The media may be treated with activated carbon impregnated
with commercially-available or in-situ-prepared MnOx-based nano
particles as described herein to give a mechanism for removing
VOCs/gases by catalytic oxidation of VOCs, such as formaldehyde.
This results in a higher capacity of removal at faster kinetics,
resulting in higher filtration efficiency and longer filter life.
Thus, the advantage of this polymeric web coated with nano
particles of manganese oxide is that the coated web can decompose
more VOCs, and at faster kinetics, to support accomplishing higher
CADR and CCM.
[0013] The polymeric fibrous structure coated with manganese oxide
acts as a strong catalyst for the decomposition and/or oxidation of
VOCs (especially formaldehyde) from the air stream into CO.sub.2.
The web has higher catalytic capacity than prior art structures to
remove gaseous contaminants (including formaldehyde vapors and
other gases) by using a catalytic coated web alone or in
combination with activated carbon in an air filtration system. Also
disclosed is technology to synthesize nano manganese oxide
particles (MnOx) and coat the polymeric web.
[0014] The filtration media disclosed herein adding catalytic
activity removes formaldehyde and molecular gases and/or vapors
from an air stream. Catalytic activity may be added to a carbon
filter by using a polymeric web layer coated with catalytic
manganese oxide and potassium ions. Alternatively, or additionally,
catalytic activity may be added to a particulate filter by
entrapping granular sorbent impregnated with MnOx between two
layers or attaching activated carbon with MnOx impregnated therein
to a fibrous web. The air filtration media for the gaseous phase
may be a combination of a particulate filter web and a carbon
filter, which may be carbon in the form of pellets, granules or
immobilized carbon in sheet form to react with (and/or adsorb) and
thereby remove the gaseous contaminants from the air stream.
[0015] The products disclosed herein should meet the emerging
standards of air filters in terms of higher filtration efficiency
to remove formaldehyde and other Volatile Organic Compounds (VOCs).
In particular, the GBT 18801 test protocol introduced by Chinese
authorities to remove formaldehyde at higher clean air delivery
rate (CADR) is desirably met by the disclosed products.
[0016] Disclosed herein is a high filtration media that immobilizes
the surface-modified carbon described herein to accomplish the
higher adsorption and catalytic activity to remove formaldehyde and
other vapors/gases from the air stream.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0017] FIG. 1 is a schematic cross-sectional view illustrating a
highly porous carbon granule onto which particles of MnOx are
dispersed.
[0018] FIG. 2 is a graphical representation of experimental data
resulting from an experiment in which the amount of time required
for multiple different substances to remove formaldehyde from a
volume of air.
[0019] FIG. 3 is a graphical representation of experimental data
resulting from an experiment in which the time for breakthrough of
a filter by contaminants is shown for each of four samples.
[0020] FIG. 4 is a schematic side view illustrating an embodiment
of the invention.
[0021] FIG. 5 is a schematic side view illustrating an embodiment
of the invention.
[0022] FIG. 6 is a schematic end view in section illustrating the
embodiment of the invention of FIG. 5 through the line 5-5.
[0023] FIG. 7 is a schematic side view illustrating an embodiment
of the invention.
[0024] FIG. 8 is a schematic end view in section illustrating the
embodiment of the invention of FIG. 7 through the line 8-8.
[0025] FIG. 9 is a schematic illustration of a heating, ventilation
and cooling system with an embodiment of the invention in place
therein.
[0026] In describing the preferred embodiment of the invention
which is illustrated in the drawings, specific terminology will be
resorted to for the sake of clarity. However, it is not intended
that the invention be limited to the specific term so selected and
it is to be understood that each specific term includes all
technical equivalents which operate in a similar manner to
accomplish a similar purpose. For example, the word connected or
terms similar thereto are often used. They are not limited to
direct connection, but include connection through other elements
where such connection is recognized as being equivalent by those
skilled in the art.
DETAILED DESCRIPTION OF THE INVENTION
[0027] U.S. Provisional Application No. 62/416,899 filed Nov. 3,
2016; U.S. Provisional Application No. 62/463,144 filed Feb. 24,
2017; and U.S. Provisional Application No. 62/422,943 filed Nov.
16, 2016 are incorporated into this application by reference.
[0028] Activated carbon in any particle size distribution from as
coarse as 4 mm to as fine as 10 micron may be treated, such as by
being impregnated, with manganese oxide (MnOx) and such complexes
prepared as their finely dispersed nano particles. The
nanoparticles of MnOx are preferably in the range of 100-400
nanometers.
[0029] These nano particles are commercially available and may be
applied to the activated carbon or other substrate. Alternatively,
the particles may be formed in situ by chemical/reducing agents
with their precursors, such as potassium/sodium permanganate,
manganese acetate, manganese oxalate and/or manganese sulfate and
others known by the person of ordinary skill. One may blend this
MnOx impregnated carbon with a proportion (10-60%) of carbon
impregnated with ionic alkaline salts, such as KOH and KCl, to
increase the activity for the catalytic oxidation.
[0030] The resulting MnOx impregnated activated carbon or other
substrates have catalytic properties in addition to adsorptive
properties. One proposed MnOx impregnated substrate is activated
carbon with a concentration of MnOx particles in the range of
0.5-5.0% by weight of the carbon. A proposed impregnated substrate
is zeolite with a concentration of MnOx particles in the range of
0.5-2.0% by weight of the zeolite.
[0031] To combine the effect of catalytic oxidation of VOCs, such
as formaldehyde, with the physisorption and chemisorption of such
VOCs, the porous carbon or other substrate is impregnated with
manganese oxide and possibly also hydroxides on finer carbon
particles and accomplished uniform dispersion of the catalytic
sites of manganese crystallites. This MnOx impregnated carbon may
be blended with a proportion of ionic alkaline salts (such as KOH
and KCl) impregnated carbon to further increase the activity for
the catalytic oxidation.
[0032] The air filtration media for the gaseous phase may be a
combination of particulate filters and carbon filters. Carbon
filters may be formed of carbon pellets, granules or immobilized
carbon in sheet form, which may have a honeycomb structure to
retain the granules.
[0033] Surface modification may be carried out on carbon in one or
more of the many forms and in a wide range of particle size
distribution by wet impregnation with manganese oxide. The
manganese oxide may be prepared by dissolving manganese precursor
compounds (such as potassium/sodium permanganate, manganese
acetate, manganese oxalate and manganese sulfate) with their
reducing agents (such as ammonium oxalate, ammonium hydroxide and
aniline) in aqueous phase. The manganese oxide particles formed in
suspension in the liquid phase are then dispersed in the activated
carbon's porous surface by wet process followed by drying at a
temperature lower than 150.degree. C.
[0034] The reaction rate forming manganese oxide particles affects
the particle size. If the precursor and reducing agents are
combined rapidly, large particles will precipitate, which is
undesirable. However, if the precursor and reducing agents are
combined in a controlled manner, for example in diluted form (in
water) with the reducing agent deliberately kept at a low
concentration to slow the reaction, the particles formed are
extremely small, as desired. The carbon with alkaline ionic charges
may be prepared by dissolving potassium precursor compounds, such
as potassium hydroxide/chloride/iodide, in water. The carbon is
impregnated or soaked with this solution for about an hour and then
dried in the same way at a temperature lower than 150.degree.
C.
[0035] The manganese precursor is typically used in the range
between 0.5 and 5 wt % of the carbon to be impregnated and prepared
using de-ionized water in 1-100% (e.g., 20%) excess of the carbon's
incipient volume. Reducing agents like ammonium hydroxide, ammonium
oxalate, oleic acid or aniline are used to convert manganese
precursors into manganese oxide particles of very small size. Then
the carbon is impregnated with this water suspension containing
fine manganese oxide nano particles, using a spraying and/or
soaking process that evenly spreads the manganese oxide nano
particles over the activated carbon.
[0036] The alkaline/K+ ionic precursor is typically used in the
range between 0.5 and 10 wt % of the carbon and prepared using
de-ionized water in 1-100% excess of the carbon's incipient volume,
as above.
[0037] In one method, commercially available manganese oxide
(MnO.sub.4) powder was purchased and 1.0 g of the MnO.sub.4 powder
was suspended in 100 ml of water. This suspension was then sprayed
on 100 g of commercially available activated carbon and dried. The
CADR test results for this carbon was similar to that of MnOx
Carbon produced in the method described below.
[0038] In another method, 1.0 g of potassium permanganate or
manganese acetate was dissolved in 120 ml of water. A few drops of
ammonium hydroxide or oxalate solution (which solution is a
dilution of 50.0 g in 500 ml of water) were added and the
combination was shaken for 30 minutes to form manganese oxide nano
particles in suspension in the liquid. Then 100.0 g of activated
carbon particles in the herein-referenced size range was sprayed
with this suspension and allowed to soak for 30 minutes. Finally,
the carbon was dried at low temperature (less than 150.degree. C.)
until the final moisture content in the carbon was less than about
1% by the weight of carbon, which took about 20-24 hours.
[0039] The described carbon impregnated with manganese oxide has
both adsorptive as well as catalytic properties to remove VOCs,
especially formaldehyde, from the air stream. The manganese oxide
is prepared in fine particles by a wet process and dispersed in the
pores of activated carbon granules. The formaldehyde (HCHO)
molecules are adsorbed and react with the catalytic MnOx particles
and are oxidized to CO.sub.2 and H.sub.2O, by the mechanism
proposed below:
HCHO+O.sub.2.fwdarw.CO.sub.2+H.sub.2O
[0040] The surface modified carbon, loaded with such manganese
oxide, acts as a strong catalyst for the decomposition/oxidation of
formaldehyde into CO.sub.2 and the decomposition and/or oxidation
of other VOCs. Furthermore, the material acts as a high efficiency
sorbent to adsorb such organic gaseous molecules by physisorption
and chemisorption in the gas phase filtration.
[0041] The resulting form of the surface modified carbon loaded
with MnOx (e.g., MnO.sub.2 and other manganese oxides) is sketched
in FIG. 1. It can be seen by the schematic of FIG. 1 that MnOx
particles are widely and evenly distributed within the pores of the
porous substrate granule, and on or toward the outer surface
thereof. At the concentrations stated herein, such MnOx particles
on the carbon substrate have catalytic properties in addition to
adsorptive properties. These MnOx particles may be mounted in a
filter to remove formaldehyde and other VOCs from ambient air that
is flowing through the filter that is mounted in a conventional
HVAC system or a room or building filtration device. The
catalyzation of formaldehyde oxidizes the harmful chemical into
much less harmful CO.sub.2 and H.sub.2O. The adsorptive feature
removes the VOC from the air by adsorption. This combination arises
due to the surface area per unit mass of the extremely small
particles of MnOx. As an example, the MnOx particles may be in the
range of 100-400 nanometers in size. The activated carbon also has
a high surface area per unit mass, and may be in the range of
800-1,300 m.sup.2/g. The preferred activated carbon has a surface
area of about 1,000 m.sup.2/g.
[0042] One advantage of the resulting carbon is that it can
decompose more VOCs, and at faster kinetics, than other products
due to the combination of adsorptive and catalytic activities.
Another advantage is that the carbon can be in any size particles
from coarser to finer mesh sizes. Moreover, the carbon can be
immobilized, such as between two layers, in a nonwoven filtration
media to impart these benefits in the given space of a filter.
[0043] In order to support the increase in efficiency by catalytic
oxidation, Applicant compared the formaldehyde CADR of different
carbon and zeolite samples. The results are shown in FIG. 2. In the
test, a 1 m.sup.3 chamber was filled with .about.1.2 ppm of
formaldehyde using a VOC generator and allowed to naturally decay
for half an hour. During this time, the temperature was maintained
at 22.degree. C. and the relative humidity at about 50%. Once the
concentration was stabilized, an air purification device in the
chamber was turned on and the time versus concentrations were
recorded until the chamber was completely cleaned of formaldehyde.
The results show that a product made according to the invention
removed the formaldehyde faster than either type of commercially
available carbon alone. It can be further seen that the surface
modified Carbon and Zeolite show significantly higher efficiency
(CADR) in cleaning the chamber as compared to those untreated (raw)
Carbon and Zeolite.
[0044] The invention differs from the prior art by the existence of
nano manganese oxide particles (MnOx) dispersed in carbon or other
sorbent substrate pores to result in the specific morphology and
properties of the combination. This results in adsorption and
catalytic activity to remove gaseous contaminants including
formaldehyde vapors and other gases.
[0045] The combination of MnOx impregnated in carbon and blended
with a proportion of ionic alkaline salts (such as KOH and KCl)
impregnated in other carbon particles further increases the
activity for catalytic oxidation. The structural integrity of the
media and its formulation with treated carbon and binder is
significant. The invention contemplates including a proportion of
the surface-modified sorbents in addition to carbon, such as
titania, molecular sieves, zeolites and alumina to result in
synergy to give even higher performance. In existing honeycomb
filters, it is contemplated to coat the structure with this
catalytic carbon so that there are two VOC-removing mechanisms
operating: catalysis by the catalytic carbon and adsorption by the
carbon in the honeycomb filter.
[0046] A method of preparing MnOx particles in aqueous phase may
begin with manganese precursors, such as potassium permanganate or
manganese acetate or manganese sulfate, and results in impregnating
carbon particles with these finely suspended MnOx particles. The
starting carbon particle size can be as coarse as 4 mm to as fine
as 10 micron with high micro-porosity and textural properties. Due
to the uniform dispersion of the fine catalytic MnOx particles on
the carbon, resulting filters have higher life at higher filtration
efficiency of gaseous contaminants.
[0047] The above-described compound impregnates activated carbon
with an in-situ-prepared nano manganese oxide (nMnOx) particles
suspension which imparts the catalytic properties to decompose
various gaseous molecules, such as formaldehyde. It is known that
formaldehyde is a basic compound in the class of "Aldehyde"
compounds. Another such compound is acetaldehyde which has similar
properties and is considered to be an equally or more toxic air
pollutant. The same nMnOx impregnated carbon may remove
acetaldehyde as well as formaldehyde, by catalytic oxidation. It is
in this context that the product is extended to the catalytic
oxidation of VOCs such as the aldehyde group of compounds, which
include formaldehyde and acetaldehyde.
[0048] Disclosed herein is a surface modification of activated
carbon and other porous sorbents by wet impregnation with
transition metals and metal oxides, especially manganese oxide. The
activated carbon granules can be any mesh size and any form, but
preferably is in the ranges of 4-8 mm, 8-16 mm, 20-50 mm and 50-200
mm U.S. mesh size. If zeolite is used, the preferred size is 12-30
mm mesh size. Activated carbon pellets may be used in the range of
2-3 mm in size. This MnOx impregnated carbon may be blended with
another carbon impregnated with ionic alkaline salts like KOH and
KCl to increase the activity for the catalytic oxidation.
[0049] An objective is to remove the gaseous species from the air
stream by higher adsorption and catalysis by the activated carbon.
The said higher adsorption and catalytic activity can be created by
different chemical treatments and impregnation with active
metal/oxides. By the chemical treatments we create different
functional groups on the carbon basal plane, which are considered
to be the chemisorption active sites. These sites are occupied by
the gaseous molecules to form a bond between a functional group and
the gas molecules and gradually become saturated. In other words,
the chemically-treated carbon (e.g., activated carbon with
potassium ions) has limited capacity for chemisorption to remove
the gaseous species. However, the catalytic carbon prepared by the
explained method of impregnation with nMnOx particles has the
capability to decompose the gaseous molecules and the remaining
active sites are regenerated after every cycle.
[0050] It is contemplated to combine the chemisorption and
catalytic mechanisms to remove gases. Two approaches are
contemplated. A first approach is to physically blend the two
carbons: the chemically-treated carbon and nMnOx-impregnated
catalytic carbons can be mixed in various proportions to combine
the effects. It is observed that the formaldehyde and other gaseous
removal efficiency increases significantly by blending the
chemisorption and catalytic carbons. The effects add up
significantly, as can be seen in FIG. 3, which shows the results of
experiments to determine formaldehyde breakthrough and saturation
capacity of various blends. The shortest breakthrough time is by
catalytic nMnOx carbon alone, the next shortest time is by
chemically treated carbon alone. The longest time to breakthrough,
which signifies the best product in this regard, is the physical
blend in 50/50 mixture of carbon impregnated with nMnOx and carbon
chemically-treated with ionic alkaline salts, such as potassium
ions (e.g., KCl, KOH, KI). The second highest time is the blend of
40% carbon impregnated with nMnOx and 60% carbon chemically-treated
with ionic alkaline salts. The longest time until breakthrough of
contaminants is thus found in the blend of 50% activated carbon
impregnated with nMnOx and 50% carbon chemically-treated with ionic
alkaline salts.
[0051] The second approach is to create dual effects of
chemisorption and catalysis on the same carbon by impregnating
first with catalytic manganese oxide and then treating with
chemical reagents. The first step of preparing nMnOx carbon is
explained herein. The second treatment is carried out on the same
carbon. For this, the chemical reagents like KI, KOH, etc., are
dissolved in water in the 10-25% volume of the carbon to be treated
and then sprayed uniformly on the nMnOx carbon.
[0052] Another embodiment may be created by coating polymeric
fibrous structures with the same manganese oxide particles and
potassium ions described herein to give additional catalytic
activity in the air filters for oxidizing VOCs, when in use
individually or in combination with carbon filters described
herein. One may prepare MnOx particles in aqueous phase (starting
with manganese precursors such as potassium permanganate, manganese
acetate, or manganese sulfate) and impregnate carbon with these
finely suspended MnOx particles. The next step is to coat the MnOx
particles on the polymeric web to accomplish the higher CADR and
CCM for removing molecular gas contaminants/VOCs from the air
stream. In the first step, the manganese precursor compound is
dissolved in water in the range between 1 and 30% w/v, the
potassium ion precursor is dissolved in the range between 10 and
30% w/v for the coating on the fibers. In the second step, the nano
manganese oxide loading is 1-5%.
[0053] The product resulting from coating fibers with impregnated
carbon is shown schematically in FIG. 4, in which a filter media,
such as a non-woven batt 100, is placed in a stream of gas flow
110. A magnified view of the media shows the porous sorbent
particles 120 in the non-woven batt 100. The particle 120 may be
impregnated with MnOx, treated with potassium ions, both, or a
combination of some impregnated and some treated. In an alternative
embodiment shown in FIGS. 5 and 6, a batt 200 of fibrous media has
interposed within it a sheet or panel 210 of material in which the
impregnated carbon particles are retained. The panel 210 may be two
sheets of woven or non-woven, gas-permeable material. Thus, the
batt 200 filters particulate while the impregnated carbon particles
retained in the panel 210 catalyze the conversion of VOCs and
adsorb the same, thereby removing the VOC from the gas passing
through the media batt 200. Another alternative embodiment is shown
in FIGS. 7 and 8, in which a media batt 300, which may be polymer
fibers formed in a non-woven structure, has had porous, sorbent
particles adhered to the fibers of the batt 300. The sorbent
particles are impregnated with metal oxide nano particles according
to the disclosure herein, and some sorbent particles may be treated
by ionic alkaline salts.
[0054] Due to the uniform coating of these catalytic MnOx particles
on the polymeric layers, such media has longer life at higher
filtration efficiency of gaseous contaminants when used in
combination with activated carbon filters described herein. Thus,
it is contemplated to create a polymeric, non-woven web of fibers
that is coated with catalytic manganese oxide and potassium ions.
This web of fibers may be used individually, or in combination with
carbon filters, in the air filtration media.
[0055] The manganese oxide coating may be prepared in multiple
steps, starting with coating the fibrous structure with a colloidal
solution of manganese compounds, such as potassium/sodium
permanganate. These may be the same as the precursors used in
formation of MnOx nano particles that coat the activated carbon
granules as described herein. The nano manganese oxide particles
are applied to the resulting web structure, such as by applying the
suspension of MnOx nano particles to the web structure. The metal
oxide complex solution is thus prepared with manganese oxide (MnOx)
using chemical/reducing agents with their precursors as
potassium/sodium permanganate or manganese acetate or manganese
sulfate, and the nano manganese oxide particles that were prepared
in aqueous form coat the polymeric fibers or web.
[0056] The manganese oxide may be prepared by dissolving manganese
precursor compounds such as potassium permanganate, manganese
acetate and manganese sulfate and their redox reactions with
chemicals agents including ammonium oxalate, ammonium hydroxide and
aniline in aqueous phase, as described herein.
[0057] Polymeric fibrous structures with different concentrations
of MnOx particles in different concentrations start with manganese
precursors, such as potassium permanganate, manganese acetate, or
manganese sulfate. This nano manganese oxide coated fibrous web may
be coated in conventional honeycomb filters to synergize the
catalytic activity.
[0058] The manganese oxide precursor may be applied to the fibers
when the precursor is diluted in water or some other liquid. The
manganese oxide nano particles may be applied to the fibers by
applying the suspension described above to the fibers. The
manganese oxide precursor on the fibers may have some effect of
catalyzing VOCs, and the manganese oxide nano particles also on the
fibers may have some effect of catalyzing VOCs. The catalyzing
effect of a resulting product can be enhanced by adding to the
fibers so coated (with manganese oxide precursor and manganese
oxide nano particles) an activated carbon filter which may be as
shown in U.S. Pat. No. 9,199,189 and/or United States Patent
Application Publication No. 2016/0023186, both of which are
incorporated herein by reference.
[0059] An embodiment of the invention is shown positioned in a
conventional heating, ventilation and cooling (HVAC) system 400 in
FIG. 9. The HVAC system 400 holds a filter 420 adjacent an air
handling furnace 430, in which a blower fan 440 draws air through
an air return 410 from rooms in a building, through the filter 420,
through the air handling furnace 430 and out a supply 450 to rooms
of the building. Any filter described herein, and any filter media
or additive to media or a filter, may be positioned where the
filter 420 is located as shown in FIG. 9. Air, or any other gas,
thereby flows through the filter 420 and VOCs, such as
formaldehyde, is catalyzed in a reaction to H.sub.2O and CO.sub.2,
and adsorbs to, the additives described herein.
[0060] This detailed description in connection with the drawings is
intended principally as a description of the presently preferred
embodiments of the invention, and is not intended to represent the
only form in which the present invention may be constructed or
utilized. The description sets forth the designs, functions, means,
and methods of implementing the invention in connection with the
illustrated embodiments. It is to be understood, however, that the
same or equivalent functions and features may be accomplished by
different embodiments that are also intended to be encompassed
within the spirit and scope of the invention and that various
modifications may be adopted without departing from the invention
or scope of the following claims.
* * * * *