U.S. patent application number 11/201660 was filed with the patent office on 2006-05-18 for high yield co-production of anhydrous hydrogen bromide and sodium bisulfate.
Invention is credited to Richard J. DeGroot, Dov Shellef.
Application Number | 20060104892 11/201660 |
Document ID | / |
Family ID | 36318065 |
Filed Date | 2006-05-18 |
United States Patent
Application |
20060104892 |
Kind Code |
A1 |
DeGroot; Richard J. ; et
al. |
May 18, 2006 |
HIGH YIELD CO-PRODUCTION OF ANHYDROUS HYDROGEN BROMIDE AND SODIUM
BISULFATE
Abstract
A process for co-producing anhydrous hydrogen bromide and a
purified bisulfate salt by (a) reacting a bromide salt with
sulfuric acid to produce crude hydrogen bromide and crude bisulfate
salt; (b) purifying the crude hydrogen bromide to produce anhydrous
hydrogen bromide; and (c) removing bromide from the crude bisulfate
salt to form a purified bisulfate salt. There are also provided
improvements in the bisulfate purification and bromine removal,
whereby bromine is removed from the system by a distillation
process and the bromide is removed from the crude bisulfate via a
spray drying process.
Inventors: |
DeGroot; Richard J.;
(Southfield, MI) ; Shellef; Dov; (Great Neck,
NY) |
Correspondence
Address: |
FERRELLS, PLLC
P. O. BOX 312
CLIFTON
VA
20124-1706
US
|
Family ID: |
36318065 |
Appl. No.: |
11/201660 |
Filed: |
August 11, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11029976 |
Jan 5, 2005 |
|
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11201660 |
Aug 11, 2005 |
|
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60628813 |
Nov 17, 2004 |
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Current U.S.
Class: |
423/482 ;
423/520 |
Current CPC
Class: |
C01B 7/093 20130101;
C01D 5/02 20130101 |
Class at
Publication: |
423/482 ;
423/520 |
International
Class: |
C01B 7/09 20060101
C01B007/09 |
Claims
1. In a method for co-producing anhydrous hydrogen bromide and a
purified bisulfate salt, where a bromide salt is reacted with
sulfuric acid to produce crude hydrogen bromide and crude bisulfate
salt, the improvement comprising separating the crude hydrogen
bromide into anhydrous hydrogen bromide and aqueous hydrogen
bromide containing at least a finite amount of bromine, and
removing the bromine from the aqueous hydrogen bromide in a
distillation process by: i) adding water to form a bromine/water
azeotrope; and ii) azeotropically distilling off the bromine.
2. The method of claim 1, wherein the bromide salt is sodium
bromide, and the bisulfate salt is sodium bisulfate.
3. The method of claim 1, wherein the aqueous hydrogen bromide is
distilled in a column and the water is provided in the top portion
of the column.
4. The method of claim 3, wherein the aqueous hydrogen bromide is
provided in the bottom portion of the column.
5. The method of claim 4, wherein the distillation produces a top
product comprising a bromine/water mixture and a bottom product
comprising debrominated aqueous hydrogen bromide which contains
less than about 500 ppm bromine.
6. The method of claim 5, wherein the debrominated aqueous hydrogen
bromide contains less than about 300 ppm bromine.
7. The method of claim 5, wherein the debrominated aqueous hydrogen
bromide contains less than about 100 ppm bromine.
8. The method of claim 5, wherein the debrominated aqueous hydrogen
bromide is a bromide/water azeotrope.
9. The method of claim 5, wherein the debrominated aqueous hydrogen
bromide is recycled back to the reactor.
10. The method of claim 5, wherein the bromine/water mixture is
condensed and separated to provide a first steam predominantly
comprising water and a second stream comprising water saturated
bromine.
11. The method of claim 10, wherein the first stream is recycled
back to the distillation column.
12. The method of claim 1, wherein the bromine is removed from the
aqueous hydrogen bromide intermittently.
13. The method of claim 1, wherein bromide salt is reacted in a
batch process.
14. The method of claim 13, wherein the reactor is further charged
with aqueous hydrogen bromide.
15. The method of claim 13, wherein the bromine is removed from the
aqueous hydrogen bromide in periods of once per every 5 to 10
batches.
16. (canceled)
17. The method of claim 27, wherein the bromide salt is sodium
bromide, and the bisulfate salt is sodium bisulfate.
18. (canceled)
19. (canceled)
20. (canceled)
21. The method of claim 27, wherein the gas comprises air and is
heated to a temperature of between about 100.degree. C. and
150.degree. C.
22. The method of claim 21, wherein the air is heated to a
temperature of between about 110.degree. C. and 140.degree. C.
23. The method of claim 27, wherein the purified bisulfate salt
contains less than 1.5 weight percent bromide.
24. The method of claim 27, wherein the purified bisulfate salt
contains less than 0.5 weight percent bromide.
25. The method of claim 27, wherein the purified bisulfate salt
contains less than 0.1 weight percent bromide.
26. The method of claim 27, wherein the purified bisulfate salt
contains less than 0.01 weight percent bromide.
27. In a method for co-producing anhydrous hydrogen bromide and a
purified bisulfate salt, where a bromide salt is reacted with
sulfuric acid to produce crude hydrogen bromide and crude bisulfate
salt which contains at least a finite amount of bromide, the
improvement comprising the steps of: i) removing the bromide from
the bisulfate salt via a plurality of drying stages; and ii) adding
water to the bisulfate salt in between the drying stages.
28. The improvement according to claim 27, wherein the drying
stages include spray drying, drying in a column, evaporation, or
combinations thereof.
29. The improvement according to claim 27, wherein the drying
stages comprise spray drying.
30. In a method for co-producing anhydrous hydrogen bromide and a
purified bisulfate salt in a reaction vessel, where a bromide salt
is reacted with sulfuric acid to produce crude hydrogen bromide and
crude bisulfate salt which contains at least a finite amount of
hydrogen bromide, the improvement comprising the steps of: i)
removing the hydrogen bromide from the bisulfate salt via a drying
process; and ii) purifying the hydrogen bromide that is removed
from the crude bisulfate by distillation.
31. The improvement according to claim 30, wherein the bisulfate
salt is purified by a spray drying process wherein the bisulfate
salt is dispersed into droplets, and the droplets are contacted
with a heated gas.
32. The improvement according to claim 30, wherein the hydrogen
bromide that is removed from the crude bisulfate salt is combined
with the crude hydrogen bromide from the reaction vessel, prior to
or concurrently with the distillation process.
33. The improvement according to claim 30, wherein the distillation
process produces a high-boiling water/HBr azeotrope.
34. The improvement according to claim 30, further comprising the
step of charging the reaction vessel with at least a portion of the
water/HBr azeotrope from the distillation process.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 11/029,976, filed on Jan. 5, 2005, of the same
title, which claims the benefit of priority of U.S. Provisional
Patent Application No. 60/628,813, filed Nov. 17, 2004, entitled
"Method For The Co-Production of Hydrogen Bromide and Low Bromide
Sodium Bisulfate from Bromide Salts and Sulfuric Acid," the
entireties of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention is directed generally to the
co-production of anhydrous hydrogen bromide and low bromide sodium
bisulfate. More specifically, there is provided in accordance with
the present invention a method of producing anhydrous hydrogen
bromide and purified sodium bisulfate from a sodium bromide slurry
and sulfuric acid.
BACKGROUND OF THE INVENTION
[0003] Anhydrous hydrogen bromide is widely used as an intermediate
in the chemical industry. It is utilized in the production of
inorganic bromides by reaction with metal hydroxides, oxides, or
carbonates; in the production of organic bromides by reaction with
alkyl alcohols or alkenes; and as a catalyst for oxidations,
alkylations, and condensations in organic chemistry. Sodium
bisulfate is likewise widely used in textiles and chemical
processing and as a preservative.
[0004] The production of hydrogen bromide from sodium bromide is
known. The reaction typically includes adding sulfuric acid to
sodium bromide and water according to equation (I): ##STR1##
[0005] One drawback of known production methods for producing
anhydrous hydrogen bromide is that a high boiling water/HBr
azeotrope stream is produced. The azeotrope is difficult and
expensive to purify as will be appreciated by one of skill in the
art.
[0006] U.S. Pat. No. 1,379,731 to Theimer, describes a method to
produce a stream of 48% HBr/water azeotrope of aqueous hydrogen
bromide. This azeotropic solution has only limited commercial
application due to the presence of the water. One approach to
converting this azeotropic stream of 48% hydrogen bromide to
anhydrous hydrogen bromide is to utilize pressure swing
distillation where one column at high pressure will produce an
aqueous stream of hydrogen bromide greater than 48%. A second
column at lower pressure will produce a stream of hydrogen bromide
with a concentration of less than 48%. Such a system will
effectively break the azeotrope and produce an essentially
anhydrous stream of hydrogen bromide; however pressure swing
distillation requires the distillation of acidic aqueous streams
under high pressure. This process will have high costs for two
reasons. First, the process must be carried out in equipment
designed to withstand the high pressures and corrosive environment.
Second, energy costs are high due to the high reflux ratios
required to affect the distillation process as well as the high
heats of evaporation of aqueous systems.
[0007] U.S. Pat. No. 2,705,670 to Chao also discloses a continuous
process for producing HBr from sodium bromide; however, that
continuous process produces amounts of molecular bromine (Br.sub.2)
and sulfur dioxide which range from about 0.035% to about 1% or
more. Indeed, Applicants have observed that duplication of the
process in Chou results in excessive amounts of bromine. The '670
patent also contains what appear to be batchwise examples, but does
not address handling of the HBr azeotrope or purification of
bisulfate salt; features critical to the commercial usefulness of
the present invention.
[0008] The production of unwanted bromine and sulfur dioxide is
believed due to the fact that sulfuric acid reacts with HBr to form
the undesirable products in accordance with equation II: ##STR2##
when the salt is added to aqueous reactants as described in the
reference. The present Applicants have also noticed that the
unwanted production of bromine can occur due to the presence of
bromates in the NaBr feed.
[0009] The need for a high-yield, environmentally friendly process
to anhydrous hydrogen bromide utilizing salts is seen by the fact
that large producers of bromide salt streams recycle them through
bromine suppliers. For example, in St. Louis, Mo. a large chemical
manufacturer produces 150 million pounds of a 44% NaBr solution. To
convert this to a usable reagent they must ship it to Great Lakes
Chemical in Eldorado, Ark. for reprocessing through conventional
chlorination routes (see U.S. Pat. Nos. 2,143,223 and
2,359,221).
[0010] The present invention is directed generally to an improved
high-yield slurry process which produces both anhydrous hydrogen
bromide and low-bromide bisulfate salt from a bromide salt source.
In the inventive process, bromide salt reacts with sulfuric acid to
produce crude HBr and crude bisulfate salt. The crude HBr stream
contains water and may also contain a small amount of bromine. The
crude bisulfate salt contains some bromide. The crude HBr and crude
bisulfate are processed into anhydrous HBr and purified bisulfate,
respectively.
[0011] Co-production of the two products minimizes waste and
enables economical re-processing of bromide salt streams. The
process is also capable of being run batchwise which allows for
processing of a variety of starting materials and allows for
re-processing of the azeotrope as will be seen in the examples
appearing hereinafter. In certain circumstances it may be necessary
to reduce the minor amounts of bromine that accumulate in the
process. This can arise, for example, when bromates are present in
the bromide salt feed. Bromine is an undesirable component in the
system because it is a highly reactive impurity. Also, due to the
presence of bromide in the bisulfate product, there exists a need
in the process to purify the bisulfate salt in a cost-effective
manner.
SUMMARY OF THE INVENTION
[0012] In one aspect, the present invention provides an improvement
to the process whereby the crude hydrogen bromide produced by the
reaction is separated into anhydrous hydrogen bromide and aqueous
hydrogen bromide which contains at least a finite amount of
bromine, and removing the bromine from the aqueous hydrogen bromide
in a distillation process by adding water to form a bromine/water
azeotrope and azeotropically distilling off the bromine. Typically,
the bromide salt is sodium bromide and the bisulfate salt is sodium
bisulfate.
[0013] The bromine may be removed from the aqueous HBr in a column
where the water is added in the top portion of the column and the
aqueous HBr is added in the bottom portion of the column. The
distillation procedure suitably produces a top product comprising a
bromine/water mixture and a bottom product comprising debrominated
aqueous hydrogen bromide having less than about 500 ppm bromine.
Preferably, the debrominated HBr contains less than about 300 ppm
bromine, and even more preferably contains less than 100 ppm
bromine.
[0014] The debrominated HBr is generally a bromide/water azeotrope
and may be recycled back to the reactor. Typically, the
bromine/water mixture is condensed and separated to provide a
stream comprising predominantly water and a stream comprising water
saturated bromine. The stream comprising mostly water may be
recycled back to the distillation column.
[0015] Suitably, the bromine is removed from the aqueous hydrogen
bromide intermittently. In preferred embodiments, the bromide salt
is reacted in a batch process and the reactor is optionally charged
with aqueous hydrogen bromide. For batchwise processing, the
bromine may be allowed to accumulate and then removed from the
aqueous hydrogen bromide in periods of about once per every 5 to 10
batches. In some circumstances it may be suitable to remove the
bromine even less frequently.
[0016] In another aspect, the present invention provides for an
improvement to the process whereby bromide in the bisulfate salt is
removed via spray drying, wherein the bisulfate salt is dispersed
into droplets and the droplets are contacted with a heated gas.
Here again, the bromide salt is typically sodium bromide and the
bisulfate salt is sodium bisulfate.
[0017] In some embodiments, water is added to the bisulfate salt
prior to the spray drying process. Typically, the water is added in
amounts needed for the bisulfate salt to form a complete hydrate.
The bromide may also be removed by processing the bisulfate in a
plurality of spray drying processes. Typically, the bromide that is
removed is recombined with the crude hydrogen bromide from the
reactor.
[0018] Preferably the heated gas in the spray drying process
comprises air and is heated to a temperature of between 100.degree.
C. and 150.degree. C., and even more preferably between 100.degree.
C. and 140.degree. C.
[0019] Typically the purified bisulfate salt contains less than 1.5
weight percent bromide and in preferred embodiments contains less
than 0.5%, 0.1%, and even less than 0.01% bromide.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The process of the invention is illustrated and described in
connection with the following figures:
[0021] FIG. 1 is a schematic diagram illustrating an alternating
batch process of the invention;
[0022] FIG. 2 is a schematic diagram which illustrates a bromine
removal system according to the invention; and
[0023] FIG. 3 is a schematic diagram illustrating a bisulfate
purification system of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The invention is described in detail below in connection
with particular features. Modifications within the spirit and scope
of the present invention, set forth in the appended claims, will be
readily apparent to those of skill in the art.
[0025] As previously explained, the production of hydrogen bromide,
from sodium bromide, is a well known process. The method comprises
the addition of sulfuric acid to sodium bromide and water according
to the process (I): ##STR3##
[0026] It has been discovered through the course of this work that
by concentrating a 44% solution of sodium bromide to a slurry of
aqueous crystals, the reaction with sulfuric acid is readily
carried out. The sodium bromide salt may be concentrated in a
crystallizer to provide the salt feed. The fact that solid sodium
bromide is present with small amounts of water affects three
things: [0027] 1. It eliminates the formation of excessive amounts
of bromine. Despite the fact that large amounts of solid sodium
bromide are present the water inhibits the formation of bromine by
dissolving the sulfuric acid before it can react with the solids;
[0028] 2. It facilitates the handling of the solids. This is the
case since chemical processing equipment is typically designed to
handle slurries; and [0029] 3. The low water concentration allows
for the production of hydrogen bromide at a concentration well
above the azeotropic concentration of 48%.
[0030] Referring to FIGS. 1-3 there is shown schematically a
suitable apparatus 10 for practicing the present invention.
Apparatus 10 is an alternating batch apparatus with a first reactor
12 and a second reactor 14 as well as a drying column 16, bromine
removal system 100, and a bisulfate purification system 200.
[0031] In order to run the reaction, reactor 12 is first charged
with sodium bromide salt via line 24. The initial slurry of sodium
bromide feed for this reaction can be made of:
[0032] 1. Water and sodium bromide crystals;
[0033] 2. 48% Hydrogen bromide and sodium bromide crystals;
[0034] 3. Sodium bisulfate hydrate (mp 58 C) and sodium bromide
crystals;
[0035] 4. Sodium sulfate hydrate and sodium bromide crystals;
and
[0036] 5. Various mixtures of the above components.
[0037] Once the reactor is charged with sodium bromide salt, line
24 is closed off and sulfuric acid, preferably highly concentrated
(>95%), is added to reactor 12 via line 28. The batchwise
reaction of sodium bromide with sulfuric acid proceeds while crude
HBr is withdrawn from reactor 12 via line 30. The crude HBr gas
typically contains from about 0.5 to about 30 percent water,
preferably less than 10 percent.
[0038] The crude HBr gas is fed to drying column 16 via line 32.
Column 16 is a fractional distillation column which removes water
from the crude product. Purified product is withdrawn at 34,
wherein the anhydrous HBr has less than 1000 ppm water, preferably
less than 100 ppm. A condensed 48% HBr/water azeotrope is withdrawn
from column 16 at 36 and is recycled via line 40 to either reactor
12, reactor 14, or the bromine removal system 100. During batch
processing of a bromide salt charge in reactor 12, it is preferable
to feed the azeotrope to batch reactor 14.
[0039] The removal of bromine may be necessary if there is a build
up of Br.sub.2 in the system. As stated above, the presence of
bromine can occur due to bromate impurities in the NaBr feed. It
should be understood, then, that the presence of unwanted bromine
in the system may occur frequently or, perhaps, only occasionally
depending upon the makeup of the bromide salt feed. The HBr
azeotrope 40 may be continuously fed to the bromine removal system
100, but is preferably only distilled intermittently to remove the
bromine as needed. Desirably the bromine should be removed about
once every 5-10 batches, or when the bromine level reaches about
1.0% or more.
[0040] When it is desired to remove the bromine from the system,
the HBr bottom stream (b.p. 124.degree. C.) is fed into a
distillation column 102 near the bottom of the column. A small
stream of water 104 is added near the top of the column to form the
bromine/water azeotrope (b.p. 58.degree. C.). A bromine/water
mixture comes off the top of the column and is sent to a condenser
106, where the mixture is condensed into liquid phase and allowed
to separate in decanter 108. The water 110 is then recycled back to
the column. The bromine stream 112, which is saturated with water
(about 600 ppm), is removed from the system. The debrominated
aqueous HBr 114 is taken off of the bottom of the column and
reintroduced to either reactor 12 or reactor 14. Recycling the
aqueous HBr from either the high boiling azeotrope 40 of column 16
or the debrominated aqueous HBr 114 of column 102, serves to
minimize waste and maximize yield.
[0041] It is believed that the bromine removal system is effective
because the addition of water at the top of the column promotes the
formation of the water/HBr azeotrope and prevents or hinders
aqueous HBr from dissolving in the Br.sub.2 which exits the top of
the column. The water/HBr azeotrope is taken off of the bottom of
the column and a mixture of water and Br.sub.2 exits out the top of
the column. The bromine/water mixture which is removed from the top
of the column may then be easily separated. Typically, the HBr at
the bottom of the column contains less than about 500 ppm bromine,
preferably less than 300 ppm bromine, and even more preferably less
than about 100 ppm bromine.
[0042] As the bromide salt is being reacted in reactor 12, reactor
14 is provided with another charge of bromide salt and preferably
with an HBr/water azeotrope from column 16 and/or column 102. The
charge of reactor 14 is optionally dried while batch reactor 12 is
provided with HBr. When a batch reaction is completed in reactor
12, that reactor is closed off and sulfuric acid is fed to reactor
14, starting processing of the next batch of bromide salt. It will
be appreciated from the foregoing that while successive batches of
bromide salts are processed batchwise in reactors 12 and 14, the
drying column 16, bromine removal system 100, and bisulfate
purification system 200 may be operated continuously, reducing
capital costs for purification.
[0043] Regarding the bisulfate production of the present invention,
while batch reactor 14 is producing product, the bisulfate
(hydrate) salt is removed from reactor 12 once the reaction is
complete, and fed via line 42 and to the bisulfate purification
system 200. Once the primary reaction between the sodium bromide
and sulfuric acid has been completed, a slight excess of sulfuric
acid is typically added to the reaction bottoms. The excess of
sulfuric acid assures that the bromide is present in the form of
hydrogen bromide. Water may also be added to the crude bisulfate
salt to facilitate bromide separation as will be appreciated from
specific examples provided below.
[0044] FIG. 3 shows the bisulfate purification system 200. The
bisulfate (hydrate) melt feed 42 is taken from the HBr reactor 12
into a first spray dryer 202. In alternative embodiments, the melt
may also be fed to a column, an evaporator, or combinations
thereof, to remove bromide, though spray drying is the preferred
method. Using a spray drying process is advantageous because it can
reduce processing and energy costs, while removing at least the
same, if not more, moisture as other processes. Spray drying
processes and apparatuses are well-known in the art. U.S. Pat. Nos.
6,223,455; 4,187,617; 4,052,255 and 4,451,330 disclose various
processes and apparatuses for spray drying a slurry to produce
solid particles. In typical spray-drying processes, a slurry or
solution is dispersed into a stream of hot gas in the form of fine
droplets or mist.
[0045] The droplets are generally formed in the spray drying
chamber by passing the slurry through a spray nozzle, or high-speed
disks or wheels. The hot gas, which is usually air, causes the
droplets to flash off moisture. The moisture carries off the HBr
from the bisulfate as the water/HBr azeotrope. Preferably, the
spray dryer should disperse the bisulfate into smaller particles
rather than larger particles, as the bromide may be more
efficiently removed from smaller particles. The air may flow
concurrently, countercurrently, or mixed-flow, in relationship to
the droplets. In the inventive process, the air is preferably
heated to a temperature of between about 100.degree. C. and
150.degree. C., and preferably between about 110.degree. C. and
140.degree. C. When contacted with the air, the droplets quickly
dehydrate becoming small solid particles which are removed from the
bottom of the tower. The solid particles are separated from the gas
stream by various means such as a cyclone or a bag filter. There
are numerous variables associated with the spray drying process,
e.g., air flow rate, air velocity, temperature, nozzle pressure,
feed consistency, etc. It should be understood that the specific
parameters used would be routinely chosen by a person of skill in
the art, depending on the desired processing conditions, bromide
content, and other considerations. Desirably, the conditions of the
spray drying process should be optimized to allow for efficient
removal of the bromide from the bisulfate.
[0046] Once the crude bisulfate is spray dried, the bromide is
evolved at stream 44 and recombined with the crude HBr stream 32.
Preferably the removed bromide is in the form of the water/HBr
azeotrope. If further removal of bromide is desired, additional
water is then added to the sodium bisulfate at hydration reactor
204 and the mixture is subjected to another spray drying process
206. The bisulfate is re-hydrated to allow for easy processability
(the anhydrate melts at about 315.degree. C. while the hydrate
melts at about 58.5.degree. C.), and also to promote the removal of
bromide. Each successive spray drying will further decrease the
amount of bromide in the crude bisulfate. Thus, the spray
drying/hydration process may be repeated several times, depending
on the desired amount of bromide content. The bromide content of
the purified bisulfate should be below about 1.5%, preferably below
0.1%, and most preferably below about 0.01%. If desired, even lower
values can be obtained by with additional spray drying/hydration
steps.
[0047] After spray drying, the bisulfate is optionally rehydrated
at reactor 208. Base is then added to the bromide-free bisulfate at
210 in order to neutralize residual acid, if needed, to bring the
bisulfate salt to the desired specification. The bisulfate is then
pelletized at 212 for sale as a commercial product. The bisulfate
salt may also be dried prior to pelletizing if the bisulfate is to
be sold as the anhydrate salt.
[0048] The invention is further illustrated in the Examples which
follow.
EXAMPLE 1
[0049] Aqueous slurry with NaBr and water: A slurry of 258 gm
sodium bromide and 58 gm water was prepared and added to a 500 ml
round bottom flask. To this was added 238 gm of concentrated
sulfuric acid over a period of 1.5 hours at a temperature of
approximately 120.degree. C. Upon addition of 15% of the sulfuric
acid, hydrogen bromide gas began to off gas and was collected in a
water trap. The reaction bottoms were then heated to 145.degree. C.
once all the sulfuric acid was added to drive off additional
HBr.
[0050] The reaction effluents were as follows: [0051] 205 gm of HBr
was collected and consisted of 90% HBr and 10% water. [0052] 334.3
gm of sodium bisulfate was collected and contained 4.0% Br--.
EXAMPLE 2
[0053] An aqueous slurry of NaBr in 48% HBr: A slurry of 600 gm
sodium bromide and 110 gm of 48% aqueous hydrogen bromide was
prepared and added to a 1000 ml round bottom flask. To this was
added 637 gm of concentrated sulfuric acid over a period of 1.5
hours. The initial temperature at the beginning of the acid
addition was 70.degree. C. and was ramped up to 140.degree. C. at
the end of the acid addition. Hydrogen bromide was generated
immediately upon the addition of sulfuric acid and was collected in
a water trap.
[0054] The reaction effluents were as follows: [0055] 526 gm of HBr
was collected and consisted of 90% HBr and 10% water. [0056] 820 gm
of sodium bisulfate was collected and contained 3.9% Br--.
EXAMPLE 3
[0057] An aqueous mixture of NaBr and NaHSO.sub.4--H.sub.2O: A
slurry of 600 gm sodium bromide with 62 gm of 48% aqueous hydrogen
bromide 59 gm NaHSO.sub.4 and 8 gm water was prepared and added to
a 1000 ml round bottom flask. To this was added 638 gm of
concentrated sulfuric acid over a period of 45 minutes. The
temperature was held at 120.degree. C. Hydrogen bromide was
generated almost immediately upon the addition of sulfuric acid and
was collected in a water trap.
[0058] The reaction effluents were as follows: [0059] 487 gm of HBr
was collected and consisted of 98% HBr and 2% water. [0060] 887 gm
of sodium bisulfate was collected.
EXAMPLE 4
[0061] Bromide reduction in NaHSO.sub.4: The sodium
bisulfate-hydrate bottoms stream from example 2 was held at
140.degree. C. and 10'' of vacuum was applied for 10 minutes. The
bromide level was reduced from 3.9% to 0.36%. The sodium
bisulfate-hydrate melt began to solidify due to reduction in
concentration of the hydrate (the hydrate melts at 58.degree. C.
and the non-hydrated sodium bisulfate melts at greater than
315.degree. C.). 50 gm of water was added to rehydrate the mixture
and 20'' of vacuum was again applied for 10 minutes. The bromide
concentration was reduced from 0.36% to 0.061%.
EXAMPLE 5
[0062] Water Balance and Recycling NaHSO.sub.4 Consisting of
Reactions 5A and 5B:
Reaction 5A
[0063] A slurry of 800.0 gm sodium bromide and 128.0 gm water was
prepared and added to a 1000 ml round bottom flask. To this was
added 840 gm of concentrated sulfuric acid over a period of 70
minutes at a temperature of approximately 130.degree. C. Upon
addition of 15% of the sulfuric acid hydrogen bromide gas was
generated and passed through a water condenser. The aqueous 48% HBr
condensate was collected and the non-condensable HBr was collected
in a water trap. The reaction bottoms were then heated to
145.degree. C. after all the sulfuric acid was added to drive off
additional HBr.
[0064] The reaction effluents were as follows: [0065] 478 gm of
non-condensable HBr was collected and consisted of: 82% HBr, less
than 300 ppm bromine and 18% water. [0066] 230 gm of condensed
aqueous HBr was collected and consisted of: 58.6% HBr, 0.201%
bromine, and 41.2% water. [0067] 1056 gm of sodium bisulfate
(hydrate) was collected and contained 4.0% Br--. Reaction 5B
[0068] 857.2 gm of sodium bisulfate were removed from the reaction
flask leaving 198.8 gm of sodium bisulfate (hydrate). To this were
added 800 gm sodium bromide and the 230 gm of aqueous hydrogen
bromide collected above. To this slurry was added 840 gm of
concentrated sulfuric acid over a period of 60 minutes at a
temperature of approximately 130.degree. C. Hydrogen bromide gas
was generated immediately upon the addition of the acid. The
hydrogen bromide gas was passed through a water condenser and the
aqueous hydrogen bromide condensate was collected. The
non-condensable HBr was collected in a water trap. The reaction
bottoms were then heated to 145.degree. C. to drive off additional
HBr.
[0069] The reaction effluents were as follows: [0070] 689 gm of
non-condensable HBr was collected and consisted of: 99.9% HBr, less
than 300 ppm bromides, and 0.1% water. [0071] 73 gm of condensed
aqueous HBr was collected consisting of: 59.5% HBr, 0.352%
bromides, and 40.1% water. [0072] 1303 gm of sodium bisulfate was
collected and contained 4.0% Br--.
[0073] From this series of reactions it is evident that reacting
NaBr in a slurry will allow for complete conversion of NaBr to HBr
without a build up of the aqueous azeotropic hydrogen bromide. This
is evident since the first reaction collected 230 gm of aqueous
hydrogen bromide and the second collected only 73 gm.
[0074] It also shows that the reaction can successfully be carried
out in a slurry of NaBr formed from the sodium bisulfate hydrate
and aqueous hydrogen bromide. This will allow for the process to be
carried out in an alternating batch reaction scheme which operates
continuously, where one reactor will be used for acidification and
a second for carrying out the steam distillation. Cycling between
the two reactors will allow for a very efficient process.
EXAMPLE 6
[0075] Bromide Reduction in sodium bisulfate with water: To the
1303 gm of sodium bisulfate above was added 130 gm water and the
mixture was distilled under a maximum of 14'' of vacuum at a
temperature of 141.degree. C. (well above the HBr azeotrope
temperature of 124.degree. C. at atmospheric pressure). After
removing 100 ml of water the bromides were reduced from 4.0% to
0.37%.
[0076] An additional 100 ml of water was added and the distillation
above was repeated but under a maximum of 18.5'' of vacuum at a
temperature of 134.degree. C. After removing an additional 100 ml
of water the bromides were reduced from 0.37 to 0.12%.
[0077] An additional 50 ml of water was added and the distillation
above was repeated but under a maximum of 20'' of vacuum at
130.degree. C. After removing an additional 90 ml of water, 50 mls
that were added and 40 ml of water of hydration, the bromides were
reduced from 0.12% to 0.03%.
[0078] Therefore, the use of water to remove bromides from sodium
bisulfate is very effective. The process can be carried out as
indicated above using liquid water. Once skilled in the art can
adapt such a procedure to a continuous process using a column or
using steam in place of water.
EXAMPLE 7
[0079] Bromide removal via spray drying: To simulate spray drying a
28.9 gm of crude NaHSO.sub.4 was added to a 500 ml vacuum flask and
heated to 125.degree. C. The NaHSO.sub.4 formed a thin film on the
bottom of the flask. Quickly applying vacuum to this will simulate
a spray dryer. 28'' of vacuum was applied and held for 1 minute.
The flask was then vented to the atmosphere and this application of
28'' vacuum and venting were repeated two additional times. This
process reduced the bromide concentration from 9.2% to 0.95%.
[0080] To these spray dried solids was added 3 ml water to
re-hydrate the mixture. It was heated to 125.degree. C. and all the
solids were allowed to dissolve/melt. Vacuum was again applied as
above. The bromides were reduced from 0.95% to 0.13%.
[0081] To the dried bottoms above were added 3 additional mls of
water and the solids were allowed to dissolve/melt. Vacuum was
applied as in the first step and the bromides were reduced to
0.0028%.
[0082] It should be noted that for this experiment it was necessary
to wipe all the condensate from the side of the flask with a paper
towel or other absorbent material. This condensate contains
HBr/water stripped from the NaHSO.sub.4 and condensed on the cold
flask walls. In an actual spray dryer no condensate would form
allowing for a more efficient bromide strip. This procedure proves
the concept that a spray drier will remove bromides from the
bisulfate.
ALTERNATE EMBODIMENTS
[0083] Additional embodiments of the inventive process for
co-producing anhydrous hydrogen bromide and a purified bisulfate
salt are also contemplated. For example, there is also provided a
process comprising: (a) charging a batch reactor with a bromide
salt slurry, wherein the slurry is more than 50% by weight bromide
salt; (b) supplying hydrogen bromide to the reactor; (b) reacting
the slurry with sulfuric acid in a batch reaction wherein bromide
salt is consumed to produce crude hydrogen bromide and crude
bisulfate salt, the crude bisulfate salt containing bromides; (d)
purifying the crude hydrogen bromide to produce anhydrous hydrogen
bromide; and (e) removing bromides from the crude bisulfate salt to
form a purified bisulfate salt. In a preferred embodiment the
bromide salt is sodium bromide and the bisulfate salt is sodium
bisulfate. A convenient way to add the hydrogen bromide to the
reactor is in the form of a water/HBr azeotrope or the hydrogen
bromide charged to the reactor is derived from a water/HBr
azeotrope.
[0084] Typically, the crude hydrogen bromide is purified by
distillation and has less than 1,000 ppm water. More preferably,
the purified hydrogen bromide has less than 500 ppm water, and even
more preferably less than 100 ppm water.
[0085] Upon isolation, the crude bisulfate salt generally has less
than 5 weight % bromide. To further purify the crude bisulfate, the
crude bisulfate salt is acidified during purification and/or water
is added to the bisulfate. Bromides are removed from the bisulfate
salts by distillation through the utilization of the 48% water/HBr
azeotrope. Preferably, the purified bisulfate salt has less than
1.0 weight percent bromide and more preferably the purified
bisulfate salt has less than 0.25 weight percent bromide, and still
more preferably has less than 0.1 weight percent bromide.
[0086] A salt slurry charged to the reactor may consist essentially
of sodium bisulfate-hydrate and sodium bromide charged to the
reactor or sodium sulfate and aqueous HBr. Additionally, it may be
desirable to add a small amount of sulfuric acid to this initial
reactor charge to help keep it fluid.
[0087] In cases where a water/HBr azeotrope is added to the sodium
bromide slurry, hydrogen bromide is preferably charged to the
reactor prior to reaction of the bromide salt with sulfuric
acid.
[0088] In a batch process for producing anhydrous hydrogen bromide
from a bromide salt and sulfuric acid, another aspect of the
invention is the improvement comprising adding hydrogen bromide to
a batch reactor prior to or concurrently with reaction of the
bromide salt and sulfuric acid.
[0089] In a batch process for producing hydrogen bromide and a
bisulfate salt from a bromide salt and sulfuric acid, still yet
another aspect of the invention is the improvement comprising
purifying the bisulfate salt of bromide such that the purified
bisulfate salt has a bromide content of less than 1.0%; preferably
the bisulfate salt has a bromide content of less than 0.5%
[0090] While the invention has been described in connection with
several examples, modifications to these examples within the spirit
and scope of the invention will be readily apparent to those of
skill in the art. In view of the foregoing discussion, relevant
knowledge in the art and references discussed above in connection
with the Background and Detailed Description, the disclosures of
which are all incorporated herein by reference, further description
is deemed unnecessary.
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