U.S. patent application number 12/135346 was filed with the patent office on 2008-10-02 for hydrogen peroxide recovery with hydrophobic membrane.
Invention is credited to Sanjay N. Gandhi, Lin Li, Anil R. Oroskar, Kurt M. Vanden Bussche.
Application Number | 20080237057 12/135346 |
Document ID | / |
Family ID | 39596651 |
Filed Date | 2008-10-02 |
United States Patent
Application |
20080237057 |
Kind Code |
A1 |
Li; Lin ; et al. |
October 2, 2008 |
Hydrogen Peroxide Recovery with Hydrophobic Membrane
Abstract
An apparatus and process are presented that provide for the
separation of hydrogen peroxide from a solution having an acid and
hydrogen peroxide.
Inventors: |
Li; Lin; (Albany, CA)
; Vanden Bussche; Kurt M.; (Lake in the Hills, IL)
; Oroskar; Anil R.; (Oakbrook, IL) ; Gandhi;
Sanjay N.; (Mount Prospect, 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: |
39596651 |
Appl. No.: |
12/135346 |
Filed: |
June 9, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11045642 |
Jan 28, 2005 |
7399344 |
|
|
12135346 |
|
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Current U.S.
Class: |
205/349 |
Current CPC
Class: |
B01D 63/02 20130101;
B01D 61/362 20130101; C01B 15/013 20130101; B01D 2325/38
20130101 |
Class at
Publication: |
205/349 |
International
Class: |
C25B 1/30 20060101
C25B001/30 |
Claims
1. A method of generating hydrogen peroxide comprising: oxidizing a
sulfate to generate a persulfate in an electrolyzer generating a
persulfate liquid stream; hydrolyzing the persulfate stream with
water to generate a hydrolyzed solution having hydrogen peroxide
and a sulfate compound; separating the hydrogen peroxide and
sulfate solution to a separation unit to form a first stream
comprising hydrogen peroxide and a second stream comprising
sulfate, wherein the separation unit comprises: a hydrophobic
membrane permeable to the vapor phase and impermeable to the liquid
phase; and recycling the second stream to the electrolyzer.
2. The method of claim 1 further comprising condensing the vapor
phase to generate a substantially sulfate free hydrogen peroxide
solution.
3. The method of claim 1 wherein separating the liquid and vapor
phases comprises passing the vapor phase to a vapor liquid
separator comprised of hollow fibers permeable to the gas phase
disposed within a shell and impermeable to entrained liquid
droplets, wherein the vapor phase is admitted to the shell side of
the fibers within the separator, and the vapor phase diffuses
through the fiber walls to the lumen side and the vapor phase is
carried through the hollow fibers.
4. The method of claim 1 wherein the hydrophobic membrane is
permeable to hydrogen peroxide vapor and impermeable to aqueous
droplets.
5. The method of claim 1 further comprising the addition of water
to the second stream to reduce the viscosity of the liquid
phase.
6. The method of claim 1 wherein the separation step comprises
passing the hydrolyzed solution to a separator comprised of hollow
fibers permeable to hydrogen peroxide and disposed within a shell,
wherein the solution is passed to the lumen side of the hollow
fibers and the hydrogen peroxide permeates the fiber walls to the
shell side of the fiber walls.
7. The method of claim 1 wherein the separation step comprises
passing the liquid phase to the shell side of vapor liquid
separator comprising hollow fibers, and passing the vapor to the
lumen side of fibers in the separator.
8. The method of claim 1 wherein the separation step comprises
passing the vapor phase to the shell side of vapor liquid separator
comprising hollow fibers, and passing the liquid to the lumen side
of fibers in the separator.
9. The method of claim 1 wherein the evaporator is a gas stripping
unit.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a Division of prior copending
application Ser. No. 11/045,642, filed Jan. 28, 2005, now allowed,
which is incorporated herein 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 the need to buy and store hydrogen
peroxide.
[0006] An aspect of the problem is the separation and recovery of
hydrogen peroxide from any chemicals used in the production of the
hydrogen peroxide. For small scale processes with periodic
production, it is desired to recover substantially all of the
intermediate chemicals in use in the process beyond water and
air.
SUMMARY OF THE INVENTION
[0007] The present invention comprises a method and apparatus for
the substantially complete separation of an acid from a solution
comprising hydrogen peroxide and acid to generate an aqueous
hydrogen peroxide solution. The process includes generating a vapor
by evaporating hydrogen peroxide and water from a solution
comprising acid and hydrogen peroxide by passing a heated gas
stream through the solution. The subsequent vapor generated
includes a mist of liquid droplets that are removed by passing the
vapor through a hydrophobic membrane to remove the liquid droplets.
The acid from the solution is retained in the liquid phase,
including the mist of liquid droplets, to generate an acid free
hydrogen peroxide solution.
[0008] In one embodiment, the invention includes an electrolyzer
for oxidizing the acid to form a peracid. The peracid is passed to
a hydrolyzer with water to generate a solution of acid and hydrogen
peroxide. The acid/hydrogen peroxide solution is passed to the
separator which generates a vapor phase for the separation of
hydrogen peroxide from the solution.
[0009] In this invention, the acid is part of the retentate for
returning to the electrolyzer and reusing in the process for
generating hydrogen peroxide.
[0010] Additional objects, embodiments and details of this
invention can be obtained from the following detailed description
of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a diagram of a hydrogen peroxide recovery
device;
[0012] FIG. 2 is a diagram of a membrane module evaporator;
[0013] FIG. 3 is a diagram of a second embodiment of a membrane
module evaporator; and
[0014] FIG. 4 is a diagram of a second embodiment of a hydrogen
peroxide recovery device.
DETAILED DESCRIPTION OF THE INVENTION
[0015] Hydrogen peroxide can be produced through electrochemical
means. This process produces a hydrogen peroxide solution with a
chemical agent for facilitating the oxidation of water to hydrogen
peroxide. The use of a chemical agent in the production of the
hydrogen peroxide requires the separation and recovery of the
hydrogen peroxide from the solution. One separation method is air
stripping, wherein the hydrogen peroxide is transferred to a vapor
phase and recovered through condensation of the vapor phase. In
order to recover adequate amounts, the process requires a high air
flow rate. Two major challenges are posed with this separation and
recovery method: first there must be adequate design for a large
gas-liquid mass transfer area, and second elimination of any liquid
entrainment.
[0016] An aspect of this invention is the substantially complete
recovery for recycle of the chemicals used in the production of
hydrogen peroxide. The invention is a method of generating hydrogen
peroxide through the use of a powerful oxidizing agent. An
electrolyzer is used to convert an oxidizable compound into an
oxidizing agent. The oxidizing agent is passed with water to a
hydrolyzing reactor which generates a solution comprising hydrogen
peroxide and the oxidizable compound. The solution is then passed
to a separation unit to separate the hydrogen peroxide from the
solution. The separation is performed by passing a gas through the
solution to create a vapor-liquid mixture. The hydrogen peroxide is
vaporized, and through the creation of a vapor-liquid mixture,
transfer of hydrogen peroxide from the liquid to the vapor is
facilitated. The transfer is enhanced with the generation of a mist
of liquid in the vapor where the liquid is in the form of small
droplets. This enhances the surface area for the transfer of
hydrogen peroxide from the liquid to the vapor phase.
[0017] The liquid droplets comprise the oxidizable compound, and
the recovery of the oxidizable compound is accomplished by the
substantially complete removal of liquid droplets from the vapor
phase. By passing the vapor phase through a hydrophobic membrane,
the liquid droplets are prevented from being carried out of the
separation unit with the vapor. The liquid droplets are accumulated
and removed through a liquid outlet port, and returned to the
electrolyzer.
[0018] The electrolyzer is operated at a temperature from about
15.degree. C. to about 40.degree. C., and at a pressure from about
100 kP.sub.A (0 psig) to about 800 kP.sub.A (100 psig). In a
preferred embodiment, the oxidizable agent is sulfuric acid, and is
oxidized in the electrolyzer to persulfuric acid in an aqueous
solution. Other preferred oxidizing agents include, but are not
limited to, sulfate salts that are oxidizable to persulfate salts,
and chlorate compounds that are oxidizable to perchlorate
compounds. The use of an electrolytic cell to produce a persulfate
is demonstrated in U.S. Pat. No. 4,144,144, which is incorporated
by reference in its entirety. The persulfuric acid solution is
passed to a hydrolyzing reactor with the addition of water, and
heated to reaction conditions to generate hydrogen peroxide in the
solution. The hydrolyzing reactor is heated to a temperature from
about 40.degree. C. to about 85.degree. C. for the reaction to
proceed, generating a solution comprising hydrogen peroxide and
sulfuric acid. The hydrolyzing reactor is sized to allow the
reaction to reach a desired degree of completion.
[0019] The sulfuric acid remains in the liquid phase when heated,
and when the hydrogen peroxide solution is passed to the
evaporator/separator, a portion of the sulfuric acid is in the
liquid droplets generated. The liquid droplets are removed from the
vapor phase to recover the sulfuric acid, generating a liquid free
vapor with the liquid being collected, cooled and then returned to
the electrolyzer. Problems associated with the separation of
sulfuric acid and hydrogen peroxide are high surface area needed
for adequate separation, and substantially complete recovery of the
sulfuric acid by substantially complete elimination of liquid from
the vapor phase, which are solved by the present invention.
[0020] The droplet free vapor comprises air, hydrogen peroxide and
water vapor. The vapor is cooled in a condensing unit and the
hydrogen peroxide is collected in an aqueous liquid phase that
results from the cooling of the vapor. The aqueous liquid is a
substantially sulfate free hydrogen peroxide solution.
[0021] One embodiment of the invention involves the use of an air
stripper as shown in FIG. 1. An acid/peroxide solution flows into
an evaporator 10 through a liquid inlet 16. A stripping gas such as
air, or a non-reactive gas, is passed through a heater 50, to heat
the stripping gas. The stripping gas can be any non-reactive gas
and for purposes of discussion, air as used hereinafter will mean
the stripping gas and can include, but is not limited to, air,
nitrogen, argon, carbon dioxide and mixtures thereof. The heated
air is passed to the evaporator 10 where the acid/peroxide solution
is heated and generates a mist laden effluent gas. The effluent gas
is passed to a gas/liquid separator 20, wherein the liquid removed
from the effluent gas contains substantially all of the acid used
in the process and the vapor is a substantially acid free hydrogen
peroxide vapor. The vapor is further passed through a hydrophobic
membrane disposed in the separator 20 to remove residual liquid
droplets in the vapor phase. The vapor is passed to a condensing
unit 30 wherein hydrogen peroxide and water vapor are condensed and
collected in a holding tank 40. Air, or a non-reactive gas, is
injected into the system through a gas inlet line 12. The stripping
gas is vented from the system through an air vent 42 off the
holding tank 40 for the condensed peroxide solution.
[0022] In an alternative, the evaporator 10 can also comprise the
gas-liquid separator, as shown in FIG. 2. The evaporator 10
includes a shell having a plurality of hollow fiber membrane tubes
14. The fibers 14 have an inside, or lumen side, and an outside, or
shell side and are made of a hydrophobic material to prevent the
diffusion of acid through the membrane walls. The liquid
acid/hydrogen peroxide solution enters through a liquid inlet 16 to
the shell side of the evaporator 10, and air passes through the
lumen side of the hollow fibers 14. The fibers 14 provide a large
contact surface area for hydrogen peroxide to migrate through and
evaporate on the lumen side of the fibers. The hydrogen peroxide is
carried out in a gas phase from the evaporator 10, and passed to a
condenser. The hollow fibers preferably are small diameter tubes
having diameters from 20 to 300 micrometers and can be used to
provide a high surface area while having a low pressure drop. The
surface areas can be on the order of 10,000 m.sup.2/m.sup.3 of
separator volume. The use of hollow fibers for collecting the vapor
as it diffuses through the fiber walls limits the amount of acid
transferred to the gas phase. The gas phase comprising hydrogen
peroxide and water vapor is subsequently directed through a gas
outlet 18 to a condensing unit 30 wherein the hydrogen peroxide is
condensed and air is vented. The acid is directed out a liquid
outlet 22 for recovery and return to the electrolyzer.
[0023] With the evaporation of water and peroxide from the
acid/peroxide solution, the viscosity increases, and in turn
increases the pressure drop. Optionally, additional water is added
to the acid/peroxide solution in the evaporator 10 to reduce the
solution viscosity. Optionally, the acid/peroxide solution and air
can enter the evaporator 10 on the shell side as a two-phase flow
with the air carrying the hydrogen peroxide vapor through the
membrane.
[0024] The high surface area facilitates the transfer of hydrogen
peroxide from the liquid to the vapor phase. The evaporation of
hydrogen peroxide is accompanied with the evaporation of water. The
liquid remaining behind has an increasing concentration of sulfuric
acid and with the increasing concentration, the viscosity also
increases. The increase in liquid viscosity adversely affects the
liquid side mass transfer. In another embodiment, the liquid is fed
to the lumen side of the hollow fibers 14, as shown in FIG. 3. By
flowing the liquid on the lumen side, liquid phase mass transfer
limitations from diffusion are reduced. The hydrogen peroxide
permeates the walls of the fibers 14 to the shell side of the
evaporator. Air is heated and passed into the shell side of the
evaporator 10, and carries out the hydrogen peroxide vapor out the
gas outlet 18 to a condensing unit 30. The acid solution is
directed out a liquid outlet 22 for recovery and return to the
electrolyzer. In this embodiment, the possibility of forming
stagnant liquid is significantly reduced.
[0025] The use of the hydrophobic membrane can also be to
substantially remove entrained liquid in the gas stream. In this
embodiment, as shown in FIG. 4, the vapor-liquid separation
comprises a first stage of gross liquid separation from a mist
laden vapor, and passing the mist laden vapor to a vapor liquid
separator having a shell side for admitting the liquid laden vapor,
and an outlet for a liquid phase. The separator includes a
plurality of hollow fibers comprising a hydrophobic material that
is permeable to the vapor. The hollow fibers carry the vapor to a
vapor side outlet 18. In this embodiment, the first stage can
comprise an evaporator 10 wherein air is heated and passed through
the acid/hydrogen peroxide solution creating a vapor comprising
hydrogen peroxide with a mist of liquid wherein the liquid mist
contains acid, and some hydrogen peroxide and a liquid phase. The
creation of a liquid mist enhances mass transfer from the liquid to
the gas phase. The liquid phase may be collected and separated in
the evaporator 10, or may be passed to the gas/liquid separator 20
to provide additional contact time between the vapor phase and the
liquid phase. The vapor phase is passed into the separator 20 for
removing entrained liquid droplets in the vapor. The separator 20
comprises a plurality of hollow fibers 14 to provide a large
surface area to transfer the vapor through the fiber membranes. In
order to prevent the acid from traveling through the fiber
membrane, the membrane is comprised of a hydrophobic material, and
the mist or droplets, accumulate on the fibers 14 and are recovered
for return to the electrolyzer.
[0026] 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.
* * * * *