U.S. patent application number 11/674914 was filed with the patent office on 2007-06-14 for synthesis of hydrogen peroxide.
Invention is credited to Santi Kulprathipanja, Laszlo T. Nemeth, Anil R. Oroskar, Gavin P. Towler, Kurt M. Vanden Bussche.
Application Number | 20070131540 11/674914 |
Document ID | / |
Family ID | 36097777 |
Filed Date | 2007-06-14 |
United States Patent
Application |
20070131540 |
Kind Code |
A1 |
Nemeth; Laszlo T. ; et
al. |
June 14, 2007 |
Synthesis of Hydrogen Peroxide
Abstract
An apparatus and process for producing hydrogen peroxide on an
as-needed basis is disclosed. An oxidizing agent is generated for
reaction with water to generate hydrogen peroxide.
Inventors: |
Nemeth; Laszlo T.;
(Barrington, IL) ; Oroskar; Anil R.; (Oakbrook,
IL) ; Kulprathipanja; Santi; (Inverness, IL) ;
Towler; Gavin P.; (Inverness, IL) ; Vanden Bussche;
Kurt M.; (Lake in the Hills, IL) |
Correspondence
Address: |
HONEYWELL INTELLECTUAL PROPERTY INC;PATENT SERVICES
101 COLUMBIA DRIVE
P O BOX 2245 MAIL STOP AB/2B
MORRISTOWN
NJ
07962
US
|
Family ID: |
36097777 |
Appl. No.: |
11/674914 |
Filed: |
February 14, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10955442 |
Sep 30, 2004 |
|
|
|
11674914 |
Feb 14, 2007 |
|
|
|
Current U.S.
Class: |
204/242 |
Current CPC
Class: |
C25B 1/30 20130101; C01B
15/03 20130101; C25B 1/28 20130101; C25B 15/08 20130101; C25B 1/29
20210101 |
Class at
Publication: |
204/242 |
International
Class: |
C25B 9/00 20060101
C25B009/00 |
Claims
1. A hydrogen peroxide generator comprising: an electrolyzer for
generating an oxidizing agent stream having an inlet and an outlet
for the generated oxidizing agent stream; a hydrolyzer for
hydrolyzing the oxidizing agent with water to generate a hydrolyzer
stream comprising hydrogen peroxide and an oxidizable compound, and
having an inlet in fluid communication with the electrolyzer outlet
and an outlet for the hydrolyzer stream; and a separator for
separating the hydrogen peroxide and the oxidizable compound, and
having an inlet in fluid communication with the hydrolyzer outlet
and an outlet for a stream comprising hydrogen peroxide and an
outlet for a stream comprising the oxidizable compound.
2. The reactor of claim 1 wherein the oxidizing agent is selected
from the group consisting of persulfuric acid, inorganic persulfate
salts, inorganic perchlorate compounds, and mixtures thereof.
3. The reactor of claim 1 wherein the oxidizable compound is
selected from the group consisting of sulfuric acid, inorganic
sulfate salts, inorganic chlorate compounds, and mixtures
thereof.
4. The reactor of claim 1 wherein the separator is an adsorber that
preferentially adsorbs the oxidizable compound.
5. The reactor of claim 4 wherein the adsorber includes a polymeric
adsorbent in sulfate form.
6. The reactor of claim 1 further comprising a hydrogen combustion
unit.
7. The reactor of claim 1 wherein the separator comprises an air
stripping unit.
8. The reactor of claim 7 further comprising a unit for dissolving
the hydrogen peroxide in water and having an inlet in fluid
communication with the air stripping outlet.
9. The reactor of claim 1 wherein the separator comprises a
distillation unit.
10. The reactor of claim 1 wherein the separator is a membrane
separation unit.
11. An apparatus for generating an oxidizing compound in an
appliance comprising: an electrolyzer with an inlet for admitting
water, an inlet for admitting a stream comprising an oxidizable
compound, and an outlet for an electrolyzer stream comprising the
oxidizing compound; a separator with an inlet in fluid
communication with the electrolyzer outlet, a product outlet for a
product stream comprising the oxidizing compound, and a recycle
outlet for a recycle stream comprising the oxidizable compound; and
a storage compartment for periodically holding the oxidizing
compound with an inlet in fluid communication with the separator
product outlet.
12. The apparatus of claim 11 wherein the oxidizing compound is
selected from the group consisting of hydrogen peroxide,
perhydroxyl ion, perhydroxyl radical, hydroxyl radical, peroxide
ion, and mixtures thereof.
13. The apparatus of claim 11 wherein the oxidizable compound is
selected from the group consisting of sulfuric acid, inorganic
sulfate salts, inorganic chlorate compounds, and mixtures
thereof.
14. The apparatus of claim 11 wherein the appliance is selected
from the group consisting of washing machines, dryers, dishwashers,
spas, pools, hot tubs, faucets, garbage disposals, air
conditioners, refrigerators, freezers, humidifiers, dehumidifiers,
toilets, urinals, bidets, agricultural equipment, sanitizers, and
food processing equipment.
15. The apparatus of claim 11 wherein the electrolyzer includes an
air inlet port and at least one outlet port for gases
generated.
16. The apparatus of claim 11 further comprising a reactor having
an inlet in fluid communication with the electrolyzer outlet, and
an outlet in fluid communication with the separator inlet.
17. The apparatus of claim 16 wherein the reactor is a hydrolyzing
unit.
18. The apparatus of claim 11 wherein the separator is an
adsorber.
19. The apparatus of claim 18 wherein the adsorber includes a
backwash system.
20. The apparatus of claim 11 wherein the separator is an air
stripping unit.
21. The apparatus of claim 11 wherein the separator is a
distillation unit.
22. The apparatus of claim 11 wherein the separator is a membrane
separation unit.
23. The apparatus of claim 11 wherein the storage compartment
includes a control system for turning the electrolyzer on and
off.
24. The apparatus of claim 11 further comprising a condensation
unit having an inlet in fluid communication with the product outlet
of the separator.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a Division of copending application Ser.
No. 10/955,442 filed Sep. 30, 2004, the contents of which are
incorporated by reference in its entirety.
FIELD OF THE INVENTION
[0002] This invention relates to the production of hydrogen
peroxide. Specifically, the production of hydrogen peroxide in an
acidic solution, and the subsequent separation and recycle of the
acid from the hydrogen peroxide.
BACKGROUND OF THE INVENTION
[0003] Currently the most widely practiced industrial scale
production method for hydrogen peroxide is an indirect reaction of
hydrogen and oxygen employing alkylanthraquinone as the working
material. In a first catalytic hydrogenation step, the
alkylanthraquinone, dissolved in a working solution comprising
organic solvents (e.g. di-isobutylcarbinol and methyl naphthalene),
is converted to alkylanthrahydroquinone. In a separate
autooxidation step, this reduced compound is oxidized to regenerate
the alkylanthraquinone and yield hydrogen peroxide. Subsequent
separation by aqueous extraction, refining, and concentration
operations are then employed to give a merchant grade product. In
order to be economical, the alkylanthraquinone process requires
large scale production of hydrogen peroxide to justify the cost of
the subsequent extraction and purification of the hydrogen
peroxide.
[0004] The direct production of hydrogen peroxide from hydrogen and
oxygen is one route to produce hydrogen peroxide without the costly
separation and purification associated with the alkylanthraquinone
process. However, there are problems associated with this, such as
working with combustible mixtures of hydrogen and oxygen in the gas
phase, and the low solubility of hydrogen and oxygen at relatively
low pressures in water.
[0005] It would be convenient and a savings to be able to produce
hydrogen peroxide without the complex processes associated with
large scale production, or using processes that require continuous
addition of chemicals which would require storage and careful
handling. In addition, a simpler process that would enable economic
production of hydrogen peroxide on a small scale and the periodic
production of hydrogen peroxide on an as needed basis can provide
for usage of hydrogen peroxide in areas where it would otherwise be
inconvenient, such as home usage, foregoing the need to buy and
store hydrogen peroxide.
SUMMARY OF THE INVENTION
[0006] The present invention provides a method and apparatus for
the production of hydrogen peroxide. The production can be in small
or large quantities, but the invention is aimed at the periodic
production of hydrogen peroxide for intermittent use. The invention
comprises an electrolyzer for generating a strong oxidizing agent
from an oxidizable compound. The oxidizing agent is passed to a
hydrolyzer where the oxidizing agent oxidizes water to generate an
intermediate stream comprising hydrogen peroxide. The intermediate
stream is separated and generates a product stream comprising
hydrogen peroxide and a recycle stream comprising the oxidizable
compound. In a preferred embodiment, the oxidizable compound is a
strong acid.
[0007] Another aspect of the invention comprises the process of
oxidizing a sulfate compound to generate a persulfate in an
electrolyzer, generating a persulfate stream. The persulfate stream
is hydrolyzed with water in a hydrolyzer to generate an
intermediate stream comprising hydrogen peroxide and the sulfate
compound. The intermediate stream is separated to generate a
product stream comprising hydrogen peroxide and a recycle stream
comprising the sulfate compound.
[0008] In a specific embodiment, the invention comprises an
electrolyzer for oxidizing sulfuric acid to generate an
electrolyzer outlet solution comprising persulfuric acid. The
outlet solution is passed to a hydrolyzer with water, and operated
at conditions to oxidize the water to hydrogen peroxide and reduce
the persulfuric acid to sulfuric acid. An intermediate stream
comprising hydrogen peroxide and sulfuric acid is passed to an
adsorption separation unit. The adsorption separation unit
separates the hydrogen peroxide from the sulfuric acid, and
generates a product stream comprising hydrogen peroxide which is
passed to a product storage unit. The adsorption separation unit
also generates a recycle stream comprising sulfuric acid and
returns the sulfuric acid to the electrolyzer. This process
minimizes the need to intermittently add chemicals to form the
oxidizing agent in the electrolyzer.
[0009] In another embodiment, the invention is as above, except for
the separation unit. The hydrolyzer passes the intermediate
solution comprising hydrogen peroxide and sulfuric acid to an air
stripping unit. The air stripping unit separates the hydrogen
peroxide from the intermediate solution by passing air through the
solution and creating a vapor comprising hydrogen peroxide, steam
and air. The vapor is condensed and a product stream comprising
hydrogen peroxide is passed to a product storage unit. The air
stripping unit also generates a recycle stream comprising sulfuric
acid which is returned to the electrolyzer.
[0010] Other objects, advantages and applications of the present
invention will become apparent to those skilled in the art from the
following drawings and detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a diagram of the process;
[0012] FIG. 2 is a diagram of an alternate embodiment of the
process;
[0013] FIG. 3 is a plot of hydrogen peroxide yields and persulfate
conversion as a function of time in a hydrolyser at 60.degree.
C.;
[0014] FIG. 4 is a plot of hydrogen peroxide yields and persulfate
conversion as a function of time in a hydrolyser at 70.degree.
C.;
[0015] FIG. 5 is plot of hydrogen peroxide concentration and pH as
a function of effluent volume in a test case;
[0016] FIG. 6 is a plot of hydrogen peroxide concentration and
sulfuric acid concentration as a function of effluent volume in a
second test case;
[0017] FIG. 7 is a logarithmic plot of the hydrogen peroxide and
sulfuric acid, with a plot of the pH of the effluent as a function
of the effluent volume in the second test case.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The synthesis of hydrogen peroxide in an aqueous solution
that is relatively free from other chemical reactants is important
for many applications. For example, bleaching and sanitizing using
hydrogen peroxide is very useful if there are no added chemicals in
the hydrogen peroxide solution that need special handling to
dispose of. Therefore it would be very useful to be able to form
hydrogen peroxide with a method that allows for relatively easy
recovery of any chemicals used in the production of the hydrogen
peroxide, or for the synthesis of an additive free aqueous hydrogen
peroxide solution. Examples of uses of hydrogen peroxide include
bleaching in washing machines, sanitizing in spas, dishwashers,
pools, hot tubs, faucets, garbage disposals, air conditioners,
refrigerators, freezers, humidifiers, dehumidifiers, toilets,
urinals, bidets, agricultural equipment, and food processing
equipment. Hydrogen peroxide in a gas phase can also be used in
dryers and for air sanitation. Positioning of the hydrogen peroxide
generation unit in the appliance and the outlet for admitting
hydrogen peroxide to the appliance is subject to determinations for
optimal hydrogen peroxide effectiveness.
[0019] The production of hydrogen peroxide requires a strong
oxidizing agent, and strong oxidizing agents can be produced
electrochemically. Inorganic persulfate compounds are very strong
oxidants, and the preferred oxidants of the present invention.
Other strong oxidizing agents include perchlorate compounds, and
perchloric acid. While other oxidizing agents are contemplated,
persulfuric acid is used as an exemplary example and not intended
to limit the choice of oxidizing agents. Currently, the commercial
method of producing persulfate compounds, such as peroxydisulfuric
acid (or persulfuric acid), is through an electrochemical process.
The operating conditions of the electrochemical reactor for the
production of persulfuric acid are different from the conditions
for using the acid to oxidize water to hydrogen peroxide.
Therefore, the persulfuric acid solution is transferred to a second
unit for reacting the acid to generate the hydrogen peroxide. The
second unit generates a solution with the desired product, hydrogen
peroxide, but also includes an undesired component, sulfuric acid.
The generated solution must be separated to produce a desired
product, the hydrogen peroxide, without the undesired component,
but also to recover the sulfuric acid to reuse and limit the need
for additives to generate the hydrogen peroxide.
[0020] While the present invention has as its preferred embodiment
the generation of hydrogen peroxide the process is intended to
include other oxidizing compounds. A solution of hydrogen peroxide
may also comprise intermediate compounds related to the production
of hydrogen peroxide. The intermediate compounds are also oxidizing
compounds that may be present in a hydrogen peroxide solution.
These intermediate compounds include, but are not limited to,
perhydroxyl ions, perhydroxyl radicals, hydroxyl radicals, and
peroxide ions. When discussing solutions comprising hydrogen
peroxide, it is intended to include solutions comprising any of one
or more intermediate compounds that may be formed during the
hydrogen peroxide production.
[0021] While most hydrogen peroxide is produced on a large scale
with a complex chemical process, hydrogen peroxide is not
conveniently stored for individual, small scale use. Therefore, an
alternative means of forming hydrogen peroxide on a small scale is
to form the peroxide directly in an electrochemical reactor. The
reactor comprises an electrolyzer for oxidizing sulfuric acid to
persulfuric acid. Persulfate production in an electrolytic cell is
demonstrated in U.S. Pat. No. 4,144,144, which is incorporated by
reference in its entirety. The reaction proceeds according to the
equation: 2H.sub.2SO.sub.4 .fwdarw.H.sub.2S.sub.2O.sub.8+H.sub.2
(1).
[0022] The reaction is driven by the electrical current running
through the electrolyzer, and is operated at a potential of about
4.5 volts. The persulfuric acid formed in the electrolyzer is
hydrolyzed with water in a hydrolyzer. The reaction in the
hydrolyzer is:
H.sub.2S.sub.2O.sub.8+2H.sub.2O.fwdarw.2H.sub.2SO.sub.4+H.sub.2O.sub.2
(2).
[0023] The product stream comprising sulfuric acid and hydrogen
peroxide in water is then separated, and the sulfuric acid is
recycled back to the electrolyzer. The electrolyzer is preferably
operated at a temperature between about 20.degree. C. and about
40.degree. C.
[0024] The process is shown in FIG. 1, wherein power is supplied to
an electrolyzer 10. Water is added to the electrolyzer and the
electrolyzer 10 comprises a solution of water and sulfuric acid,
wherein the sulfate is oxidized to produce a solution comprising a
persulfate. The solution comprising persulfate is drawn off from
the electrolyzer 10 and passed to a hydrolyzer 20. Water is added
to the hydrolyzer 20 with the persulfate solution, wherein the
water is oxidized by the persulfate compound to form a solution
comprising hydrogen peroxide and sulfuric acid. The solution
comprising hydrogen peroxide is passed to a separator 30, wherein
the hydrogen peroxide and sulfuric acid are separated. The sulfuric
acid is recycled to the electrolyzer 10.
[0025] While one embodiment of the electrolyzer uses sulfuric acid,
alternate embodiments can use other oxidizable compounds, such as
for example chlorate compounds, inorganic sulfate salts, or a
mixture of sulfate salts and sulfuric acid. Among the preferred
inorganic sulfate salts, examples include, but are not limited to,
sodium sulfate, potassium sulfate, and ammonium sulfate. Other
inorganic chemicals that would be useful, are chemicals that form
strong oxidizing agents when oxidized in an electrical environment
such as in an electrolyzer.
[0026] There is a continuous feed of water to the electrolyzer to
make up for water consumed in the process. During the operation of
the electrolyzer, hydrogen in the form of a gas is generated. This
hydrogen can be used to recover some of the energy that is used
during the operation of the electrolyzer. One embodiment for using
the hydrogen generated is to combust the hydrogen and form steam.
The steam can be used as heat that is used in the process of
separating the sulfate compound from the hydrogen peroxide. This
embodiment is illustrated in FIG. 2, where an electrolyzer 10
oxidizes sulfuric acid to generate persulfuric acid. The
persulfuric acid is drawn off and passed to a hydrolyzing reactor
20, where the persulfuric acid reacts with water to form a solution
having hydrogen peroxide and sulfuric acid. The solution with
hydrogen peroxide and sulfuric acid is passed to a separation unit
30, where a product stream comprising hydrogen peroxide is
generated and a recycle stream comprising sulfuric acid is
generated. The recycle stream is passed to the electrolyzer 10 to
replenish the sulfate compound carried out to the hydrolyzing
reactor 20. The electrolyzer is operated at a temperature between
about 5.degree. C. and about 50.degree. C., with a preferred
operation between about 10.degree. C. and about 40.degree. C.
[0027] A product of the oxidation of sulfuric acid is the
production of hydrogen in the form of a gas. The hydrogen is passed
to a combustion unit 40 which generates heat and steam. The energy
produced by the combustion unit 40 can be used to heat the
hydrolyzing reactor 20 for use with other units. In one embodiment,
the hydrolyzer is operated between about 20.degree. C. and about
90.degree. C., with a preferred operation between about 40.degree.
C. and about 85.degree. C., and a more preferred operation between
about 60.degree. C. and about 70.degree. C. In another embodiment,
the heat or steam or both can be passed to the separation unit 30,
providing a portion of the energy required to drive the separation
of hydrogen peroxide and sulfuric acid.
[0028] The hydrogen peroxide and sulfate compound are separated in
a separation unit generating a first product stream comprising
hydrogen peroxide, and a second product stream comprising the
sulfate compound. The second product stream is also a recycle
stream, wherein the recovered sulfate compound, in this instant
invention sulfuric acid, is returned to the electrolyzer for
continuing the process.
[0029] In one embodiment, the separation unit is a distillation
unit. The distillation unit can be an ordinary distillation unit, a
vacuum distillation unit, or a steam distillation unit. The choice
of distillation unit will depend upon design and economic
considerations. In the embodiment of a steam distillation unit, the
hydrogen combustion unit can provide at least a portion of the
steam used in the steam distillation separation. Distillation
methods and operating conditions are well known in the art, and are
not discussed here.
[0030] The current invention comprises the formation of hydrogen
peroxide with the use of an acidic additive to drive the reaction.
One of the problems to be solved is the separation of the additive
for recycle. Acids are used as food acidulants in the
pharmaceutical industry, and in industrial and detergent
formulations. Currently, technology for the separation of organic
acids involves salt precipitation by forming a calcium salt. The
precipitated calcium salt is filtered and washed, and then
reacidified with a strong acid, such as sulfuric acid, to
regenerate the organic acid. Examples of organic acid separations
are found in European Patent No. 135,728; United Kingdom Patent No.
868,926; and U.S. Pat. No. 4,323,702. These patents while
presenting organic acid separation require the addition of
additives, other than water, or use anion exchange resins that are
not especially suited to this separation process.
[0031] In another embodiment, the separation unit comprises an
adsorber. The adsorber may be a polymer based adsorption column, a
reverse phase column, an ion exchange column, or an acid exchanged
anion exchange column. This invention can be practiced as a fixed
or moving bed adsorbent system, and can be run as either a batch or
continuous process. It is preferred that the process be operated as
a continuous process, and can be operated as a continuous
countercurrent simulated moving bed system. One such system is
described in U.S. Pat. No. 2,985,589, which is incorporated by
reference in its entirety.
[0032] The acid exchange anion exchange column produces an
adsorption system that preferentially adsorbs the acid. Therefore,
a solution comprising an acid compound and hydrogen peroxide is
passed over an adsorbent, and the adsorbent preferentially adsorbs
the acid compound. In a particular embodiment, the acid compound is
sulfuric acid, and the anion exchange resin is a polymeric
adsorbent in sulfate form, wherein the adsorbent comprises a weakly
basic anionic exchange resin having tertiary amine or pyridine
functional groups, or the adsorbent comprises a strongly basic
anionic exchange resin having quaternary amine functional groups,
or the adsorbent comprises mixtures thereof. The ion exchange
column is operated at a temperature between about 20.degree. C. and
about 100.degree. C., and at a pressure between about 100 kPa (14
psia) and about 800 kPa (116 psia). It is preferable that the pH of
the solution is lower than the first ionization constant,
pKa.sub.i, of the strong acid. This achieves high selectivity of
the adsorbent for the adsorbed acid compound. A calculated
separation capacity for the anion exchange column is about 85
g/liter resin of hydrogen peroxide, and about 17 g/liter resin of
sulfuric acid.
[0033] Without being bound to any theory, it is believed that the
sulfate compound is adsorbed on the anion exchange membrane through
hydrogen bonding, thereby slowing the passage of the sulfate
compound through the adsorber, and allowing the hydrogen peroxide
to pass through more quickly, and generating a sulfate free
hydrogen peroxide solution. Using water as the carrier of the
solution facilitates desorption of the sulfate compound from the
adsorbent during a backflush of the adsorber, or for use in a
continuous process, such as with a simulated moving bed.
[0034] After the sulfate free hydrogen peroxide solution emerges
through the outlet from the adsorption unit, the solution is passed
to a collection vessel, or holding tank. The solution continues to
be passed to the collection vessel until the sulfate compound
begins to appear at the outlet of the adsorption unit. When the
sulfate compound begins to appear from the adsorption unit, the
solution is no longer passed to the collection vessel. The
subsequent solution containing the sulfate compound is recycled
back to the electrolyzer, or the method can begin reversing flow of
desorbent through the adsorption unit. In a preferred operation, it
is desired that the hydrogen peroxide solution be substantially
free of the sulfate compound, while it is not required that the
sulfate solution that is recycled to the electrolyzer be free of
hydrogen peroxide. Therefore, the cutoff of the flow to the
collection tank is determined based upon prevention of loss of the
sulfate compound and not on the amount of hydrogen peroxide carried
in the recycle stream back to the electrolyzer.
[0035] The adsorbed sulfate compound can be recovered by
continuously running the adsorption column with a desorbent, such
as for example water, or the column can be backwashed with a
desorbent after the hydrogen peroxide has been removed from the
column. Following separation, the sulfate compound is recycled to
the electrolyzer.
[0036] In one embodiment, the apparatus includes a control system
for turning the electrolyzer and separator on and off for a
periodic, as-needed supply of hydrogen peroxide. This would be
integrated with the entire control system for an appliance using an
oxidizing compound.
[0037] In another embodiment, the separation unit is a
precipitation unit, wherein the sulfate compound is reacted to form
a precipitate and removed from solution. One specific example of an
oxidizable compound is a sulfate compound and a specific sulfate
compound is sulfuric acid, and is neutralized with a base wherein
the neutralized acid forms a solid salt precipitate. The
precipitate is separated from the liquid phase, and the hydrogen
peroxide is recovered. The precipitate can be reconstituted, to
regenerate the acid and recycle the acid to the electrolyzer.
[0038] In another embodiment, the separation unit is an air
stripper. The air stripper comprises a vessel wherein the solution
from the hydrolyzer is passed. The solution comprising hydrogen
peroxide and sulfuric acid is aerated by passing air through a
sparger, or other means to distribute the air in small bubbles in
the solution. The hydrogen peroxide is preferentially carried out
in the air with water vapor in a gas phase. The gas phase is then
condensed to recover an aqueous solution comprising hydrogen
peroxide.
[0039] Other embodiments include using a membrane separation unit
wherein the membrane preferentially allows passage of one of the
compounds in the process. Membrane separators are known in the art
and described in U.S. Pat. No. 6,288,178 which is incorporated by
reference in its entirety.
EXAMPLE 1
[0040] Experiments were run for the hydrolysis of persulfate. The
experiments were performed to test the use of hydrolyzing reactors
for producing hydrogen peroxide. The glass reactor was heated to
60.degree. C. with hot water, and when the temperature stabilized,
100 grams of persulfuric acid solution was added to the 100 ml
capacity reactor and stirred. The system was closed and the
reaction was allowed to proceed. The system included an inverted
glass cylinder for collecting any gas generated during the
reaction. Samples of the solution were taken initially, and at
intervals of 30 minutes for up to 2 hours. The samples were then
analyzed for hydrogen peroxide concentration and for persulfuric
acid concentration.
[0041] FIGS. 3 and 4 show the results of hydrolysis of persulfuric
acid in the production of hydrogen peroxide, for reactors operated
at 60.degree. C. and 70.degree. C. respectively. The persulfuric
acid oxidized water to form hydrogen peroxide. The results show the
persulfate rapidly reacts with the water, with about 100%
conversion of the persulfuric acid to sulfuric acid over the course
of approximately 2 hours. The percentage yield of hydrogen peroxide
is the amount of hydrogen peroxide produced relative to the amount
of persulfate reacted. The results indicate that the reaction
proceeds almost to completion and that one can expect greater than
80% of the expected amount of hydrogen peroxide from the reaction.
From the experimental results, the operating temperatures for the
hydrolyzing reactors is preferably between about 40.degree. C. and
about 85.degree. C.
EXAMPLE 2
[0042] After the production of hydrogen peroxide, a solution
comprising hydrogen peroxide and sulfuric acid is generated. The
solution needs to be separated and a product stream comprising
hydrogen peroxide, and a recycle stream comprising the acid are
needed. An anion exchange resin was used for separation of the
sulfuric acid and hydrogen peroxide. A commercially available anion
exchange resin was used, AMBERLITE.TM. IRA-400 from Rohm &
Haas, Philadelphia, Pa. The resin was acid saturated with sulfuric
acid and loaded into an ion exchange column, forming a bed volume
of 20 cc. The column was washed to a pH neutral condition, and then
solutions of sulfuric acid and hydrogen peroxide were injected. The
column was operated at room temperature and atmospheric pressure.
The solutions comprised 5% H.sub.2O.sub.2 and 1% H.sub.2SO.sub.4,
and were injected in amounts of about 34 cc. In one run, as shown
in FIG. 5, the hydrogen peroxide concentration peaks and declines,
followed by the pH beginning to decline, indicating the hydrogen
peroxide passed through the column before the sulfuric acid began
to exit the column. The recovery for both hydrogen peroxide and
sulfuric acid were calculated at about 100%.
[0043] A second test example is shown in FIGS. 6 and 7
demonstrating the separation of the hydrogen peroxide and sulfuric
acid, and that an ion exchange resin such as AMBERLITE IRA-400
provides for a good separation of the hydrogen peroxide and
sulfuric acid. The data indicates that one can recover most of the
hydrogen peroxide with almost no sulfuric acid, and that the
sulfuric acid can be substantially entirely recycled.
EXAMPLE 3
[0044] The separation of hydrogen peroxide and sulfuric acid is
needed to produce an acid free hydrogen peroxide solution. In this
example an alternate method of separating the compounds was tested.
A solution comprising 5 wt. % hydrogen peroxide and 20 wt. %
sulfuric acid was obtained. 100 grams of the solution was loaded
into a vessel having a 500 cc volume. The vessel was heated, and
air was passed through the solution and generated a vapor stream
comprising water and hydrogen peroxide. The vapor stream was
condensed in a condenser which was cooled to a temperature between
about 0.degree. C. and about 20.degree. C. The cooled vapor stream
was then passed through water in a container at temperature between
about 0.degree. C. and about 20.degree. C. to dissolve any residual
hydrogen peroxide in the cooled vapor.
[0045] The results for the separation of hydrogen peroxide and
sulfuric acid by air stripping are shown in Table 1. TABLE-US-00001
TABLE 1 Material Air Flow Time H2O2 conc., H2O2 H2SO4 Conc. In
Balance Decomposed Run # Temperature (liters/min) (hours) wppm
Recovery Adsorber wppm for H.sub.2O.sub.2 H.sub.2O.sub.2 1 60 20.8
4 9848 70.24% 5.15 0.87 13.37% 2 80 15 3 21,010 81.36% 923 0.81
18.62% 3 80 24.5 3 17,766 80.85% 251 0.81 18.95%
[0046] All of the runs passed through glass wool in the gas phase.
It was found that air separation generates a relatively high
recovery of hydrogen peroxide with a greater than 99% removal of
the sulfuric acid from the hydrogen peroxide.
[0047] While the invention has been described with what are
presently considered the preferred embodiments, it is to be
understood that the invention is not limited to the disclosed
embodiments, but it is intended to cover various modifications and
equivalent arrangements included within the scope of the appended
claims.
* * * * *