Note: Descriptions are shown in the official language in which they were submitted.
GE2 6224
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METHOD OF FORMING HYDROGEN
- Disclosure
The present invention relates to the art of forming hydro-
gen and more particularly to a method of forming hydrogen by
electrolysis of a halogen acid produced in ac~ordance with a
novel concept utilizing carbon, such as coke or coal.
The invention is particularly applicable for an electrolysis
process employing hydrochloric acid or hydriodic acid, and it
- will be described with reference thereto; however, it is apprec-
iated that the invention has broader applications and may be
, used with hydrobromic acid. The use of the process with the
hydroflouric acid would electrochemically be appropriate, however,
because of the highly active nature of flourine, this particular
halogen is not preferred. Also, other than with hydroflouric acid,
the process can be used in a gas mode.
Background of Invention
The production of hydrogen is becoming quite desirable
- since hydrogen has beneficial aspects as a direct heating fuel
` or as a means ~or generating electrical energy in a fuel cell.
Consequently, substantial efforts have been devoted to obtain-
ing large volumes of hydrogen for subsequent use in heat ar
electrical energy generation. At this time, the most co~mon
method of producing hydrogen is electrolysis of water, which
consumes a substantial amount of electrical energy since it
requires over 2.0 volts D.C. for decomposition. As is well
known, the higher the voltage necessary for electrolysis, the
higher the electrical energy cost for the process. To reduce
the cost of production of hydrogen, most efforts have been di-
rected toward modifying the water electrolysis process in a
~" manner to reduce the voltage required for the hydrolysis and,
` thus, the electrical energy required. For instance, it has been
; 30 suggested that high pressure water electrolysîs cells can be
developed which will reduce the voltage ~rom slightly over 7.0
volts to the general range of about 1.6-1.7 volts. Still, the
production of hydrogPn by the electrolysis of water will involve
a substantial electrical energy input which will continue to
render hydrolysis of water for the production of hydrogen an ex-
pensive process even though it may be commercially feasible in
view of the versatility of the generated hydrogen.
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GR2-6224
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The present invention relates to a novel method of pro-
ducing hydrogen by electrolysis in a cell using a halogen
acid such as hydrochloric acid, hydrobromic acid or hydriodic
acid. In this manner, the electrolysis voltage can be reduced
and the required electrical energy for the electrolysis process
can be made lower than even the proposed improved processes
for water electrolysis.
The electrolysis of halogen acid to produce hydrogen and
the constituent halogen is a well known technology. This con-
cept is shown in United States Letters Patents 603,058;
1,746,542; 3,236,760; 3,242,065 and 3,756,930. The present
invention does not involve, as a novel feature, the concept of
obtaining hydrogen from the electrolysis of the halogen acid;
however, the invention relates to this general field and de-
velops a novel method wherein this electrolysis process can be
used for economic creation of hydrogen at a cost substantially
` below the cost of water electrolysis. Consequently, the inven-
tion relates to a method wherein the halogen acid electrolysis
concept can be employed for the production of commerci&l quan-
20 - tities of hydrogen with an overall efficiency heretofore not
obtainable. As will be described with respect to the present
; invention, the invention involves the concept of employing the
electrolysis of the halogen acid in combination with a method
of producing the acid in an efficient manner, which results in
a sufficient quantity of the acid created at a low cost factor.
The process is performed in a unit or device involving both the
electrolysis cell and the acid forming reaction area which may
be in the electrolysis cell itself or communicating therewith by
conduits through which the halogen acid for the electrolysis
process is circulated in liquid or gaseous form.
In summary of the background~ the present invention relates
to an improvement in producing hydrogen by employing the halogen
acid electrolysis concept with a novel interacting and combined
halogen acid producing concept,
The Invention
In accordance with the present invention, the electrolysis
cell for separation of hydrogen from a halogen acid incorporates
a reaction area in which the acid is formed using the halogen
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released by the electrolysis process. In accordance with ~he
broadest aspect o~ the invention, the reaction area is ad-
jacent the halogen collecting area of the electrolysis cell
and uses the halogen released by the cell, water and a re-
action agent for creating additional halogen acid. When the
acid is in solution, the solubility of the released halogen in
the acid solution together with the hydrogenation ef~iciency of
the present invention contributes to efficient replenishing of
the halogen acid for subsequent electrolysis to produce hydrogen.
In one aspect of the invention, the reaction zone for
creating additional acid for the electrolyte solution uses
>: water and the disassociated halogen to create addi~ional halogen
- acid. This chemical reaction requires rapid hydrogenation which
is obtained, in accordance with one aspect of the invention, by
using a catalyst such as graphitized carbon, ruthenised ~itanium
or platinised titanium. These three catalysts are effective for
hydrogenation to a certain acid concentration level which is
approximately 5% for hydrochloric acid. In accordance with the
preferred embodiment of the invention, the reaction in the re-
action area of the method involves the use of ungraphitize~
carbon which enters into the chemical reaction to produce addi-
tional halogen acid and creates carbon dioxide as a by-product.
This ungraphitized carbon, which is used in the preferred em-
bodiment of the invention, allows the hydrogenation of th~
disassociated halogen beyond relatively acid concentrations
.` which are obtainable with the catalyst concept as e~plo~ed in the
present invention. The preferred embodiment employs a solu-
tion of halogen acid; however, a gaseous process can be used.
The liquid process will be hereinafter explained. The halogen
acid as used herein is hydrohalic, i.e. no combined oxy~en.
The present invention involves the method of forming hydrogen
by the electrolysis of the halogen acid in a solution, which
method includes also the use of a reaction zone in which the
halogen acid is replenished by reacting dissolved, electro-
chemically released halogen with water in the presence of a
catalyst or in the presence of ungraphitized carbon. The la~ter
preferred aspect of the method allows higher concentrations of
the halogen acid by producing hydrogenation at concentration
levels greater than the catalyst method and substantially grea~er
than other known processes for obtaining halogen acid by reac-
tion of a halogen directly with water. Thus, the present inven-
tion requires only the use of water to maintain the continuous
~1 4~
operation of the hydrogen forming method. In the preferred
embodiment water and ungraphitized carbon is used to increase
the concentration of the halogen acid and thus the efficiency
of the total electrolysis process. As can be seen, by using
the present invention, hydrogen is released for use exterior
of the cell. Only water or water and carbon must be introduced
into the cell. The electrical working voltage of the cell
is substantially less than an electrolysis cell used in the
electrolysis of water. Consequently, by using only water as
the input material hydrogen is obtained at an electrical
efficiency not obtainable in a cell which produces hydrogen by
direct electrolysis of water. In the present invention, the
water is first converted into the halogen acid which is then
efficiently converted into hydrogen and the halogen, which
halogen is dissolved back into the Qlectrolyte within the cell
itself, reacts with water in the presence of the stated catalyst
; or ungraphitized carbon to again convert the water into the more
efficiently decomposed halogen acid solution.
- This novel method which will be described hereinafter in
detail and defined in the appended claims hereof is not suggested
by the known prior art. Production of a halogen acid, such as
hydrochloric acid, by heated carbon and water is illustrated in
United States Letters Patents 1,229,509; 1,420,209; 1,485,816;
1,695,522; 1,843,196; 1,843,354; 1,870,308; and 2,238,896. None
of these patents suggest a method for producing hydrogen, nor
` the concept of using carbon particles in a reac~ion zone of an
electrolysis cell to produce a halogen acid by using the released
halogen. The present invention relates to the concept of obtain-
ing hydrogen from water without the direct electroLysis of the
water itself. United States Letters Patent 3,995,016 suggests
a method of producing hydrogen from water wherein water vapor
and iodine vapor is reacted to form hydrogen iodide which is then
decomposed into hydrogen and iodine. This process reacts water
vapor and iodine vapor in an initial step. The present inven-
tion relates to an electrolysis process wherein a solu~ion of
halogen acid is employed, which
process is not suggested by this prior process of producing
hydrogen from water using iodine. Another method of producing
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~E2-6~Z~
hydrogen and oxygen from water without the electrolysis of
water is illustrated in United States Letters Patent ~,069,120.
In this patent, the halogen and water is combined as gas which
is radiated to form the hydrogen halide. Again, this process does
not relate to the use of the disassociated halogen in an electrol-
ysis process for recreating the depleted electrolyte acid. Also,
no reaction ~one employing a reaction agent is shown.
United States Letters Patent 4,021,323 relates ~o a system
for producing hydrogen by ~he electrolysis of hydrogen ~odide.
In this arrangement, the hydrogen iodide is replaced by a
chemical reaction with the released hydrogen and iodine in a
water solution. The iodine is not dissolved in the electralyte,
which is then continuously replenished by reacting the di~solved
iodine with water in the presence of ca~bon or a catalyst as
disclosed in the p~esent invention.
The prior art described in conjunction with the basic
aspects of the present invention is to show the novelty of
the simplified method of the present invention for producing
hydrogen from water or water and carbon, preferably ungraphi-
tized carbon.
In one aspect of the present invention, there is
provided a method of forming halogen by electrolysis of the
halogen acid produced from a reaction process using electroly-
tically released hydrogen dissolved in the solution. This
method involves providing an electrolysis cell with a hydrogen
electrode in a hydrogen collection area of the cell and a
halogen electrode in a halogen collecting area of the cell.
A solution of halogen acid is provided in the cell to form a
liquid electrolyte with a known total working voltage. A
continuous process is used for producing the halogen acid of
the electrolyte used in the solution. This continuous process
involves dissolving the electrolytically released hydrogen of
the halogen electrode into the halogen acid solution at the
halogen collecting area and reacting the dissolved halogen
in a reaction area adjacent the halogen collecting area with
the solution water of the electrolyte and in the presence of
~` a catalyst selected from a group of graphitized carbon, ruthenised titanium and platinised titanium or ungraphitized carbon.
This reaction creates hydrogenation of the dissolved halogen
within the
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GE2-6Z24
- 6 -
electrolyte solution to replenish the acid of the solution
by the addition of only water or water and carbon. In the pre-
ferred embodiment, the carbon particles are ungraphitized car-
bon, such as coke. By using the dissolved halogen in the
electrolyte the electrolyte and the dissolved halogen can be
circulated through the reaction zone to produce a total unit
wherein the continuous addition of water or water and cok~
allows continuous production of hydrogen by the elect~olysis
process.
; 10 The primary object of the present invention is the pro-
vision of a method of producing hydrogen by electrolysis, which
method requires a lesser working potential than the hydrolysis
of water.
Another object of the present invention is the provision
of a method as defined above, which me~hod utilizes a dilute
solution of halogen acid into which acid the released halogen
of the electrolysis process can be dissolved for replenishing
the halogen acid of the electrolyte in a connected reaction
zone by the addition o water or water and carbon.
Still a further obiect of the present invention is the pro-
vision of a method as defined above, which method can be used to
convert coke and water to hydrogen by an electrolysis concept.
These advantages, the advantages discussed in relation to
the prior art and other advantages, which will be apparent from
the following description of the present invention, illustrate
the advance in the art realized by the present invention when
producing hydrogen.
Brief Description of Drawings
FIGURE 1 is a schematic illustration of the apparatus for
performing the method constituting the present inventibn.
FIGURE 2 is an acid concentration graph illustrating a
characteristic of certain materials used in the reaction zone
or area of the method constituting the present invention;
FIGURE 3 is a graph illustrating the over-voltage char~
acteristics of ungraphitized carbon compared tv graphitized
carbon which is theorized as the reason ungraphitized carbon
will allow a substantially higher hydrogenation of the halide
dissolved in the electrolyte of the present invention;
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GE2-6224
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FIGURE 4 is a schematic view illustrating a more detailed
arrangement for performing the method constituting the pre-
ferred embodiment of the present invention;
FIGURE 5 is a schematic view illustrating a system for using
the present invention in a gaseous mode; and,
FIGURE 6 is a schematic view illustrating the use of a fea-
ture of the invention for stripping chlorine.
~ 10
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!' Preferred Embodiment of The Invention
Referring now to FIGURE 1, there is schematically illus-
trated a device or cell for practicing the present invention
of making hydrogen from water and preferably from water and
ungraphitized carbon particles. In accordance with this illus-
: trated embodiment, device or cell A includes a hydrogen elec-
trode 10 and a halogen electrode 12 adjacent to which a halogen,
~20 such as chlorine or iodine, is released ior immediate absorp-
tion into the electrolyte E formed from a solution of halogen
acid corresponding to the halogen being released at electrode
12. An appropriate power supply 11 applies-a decomposition
vol~age across electrodes 10, 12 to decompose the halogen acid
in the electrolyte solution to produce hydrogen at the hydrogen
collecting area 14 of compartment 16 and the halogen at the
halogen collection area 20 of compartment 22, Compartments 16
and 22 are connected by an appropriate arrangement including a
`;` channel 24 separated by a membrane 30 which, in practice, is
~30 formed from Nafion produced byDuPont. This membrane is No. 120
Nafion and is approximately 10 mils in thickness. As is well
known, Nafion is a perfluorosulfonic acid based permselective
plastic material.
Compartment 16 includes a lower drain 32 and compartment 22
includes a lower drain 34. Appropriate valves 3~, 38, respec-
`: tively, are used to control the level of liquid in these compart-
ments. These drains can be used to remove sludge or other un-
wanted accumulated materials at the bottom of the respective
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compartments 16, 22. Within compartment 22, which not only
forms the halogen collecting area but also the reaction zone
or area for p~oducing make-up halogen acid, there is provided
an inlet 40 through which water and carbon particles C are
introduced. An appropriate valve or other metering device 42
controls the amount of car~on particles and/or water which is
introduced into the reaction area formed by compartment ~2.
At the start of the process, it is desirable to introduce
halogen, such as chlorine, into ~he reaction compartment 22.
This is schematically illustrated as a halogen inlet 44 con-
` trolled by an appropriate valve 46. An impeller 50 is
supported in compartment 22 by an appropriate journal mount
52 and is driven by an electric motor 54 to maintain a liquid
eurrent flow outwardly and upwardly in the electrolyte E of
; 15 compartment 22. Consequently, the electrolyte in the reaction
zone is agitated and continuously circulated. This maintains
the carbon particles C in suspension within the electrolyte of
compartment 22. In practice, the electrolysis produces suffl-
cient heat to maintain the electrolyte in the reaction zone
at above about 80C. This temperature facilitates the chemical
reaction in area 20. At first it may be necessary to heat the
electrolyte. This can be done with cal rod 60 connec~ed across
terminals 62, 64. An electrical heating control 66 senses the
electrolyte temperature by thermocouple 68 and controls heating
element 60. During continued use the electrolysis heat is suffi-
cient to maintain the level of heat in the reaction zone. As
previously described, the carbon particles C react with the water
to form carbon dio~ide which accumulates in the upper portion
of eompartment 22. Since the carbon dioxide is substantially
. 30 insoluble in the electrolyte E, an appropriate Yent 70 is pro-
vided to allow escape of the carbon dioxide through a one-way
`; eheek valve 72 conneeted to a water trap 74 containing a body
of water 76. This body o~ water absorbs and dissol~es any
halogen whieh may escape with the earbon dioxide through ~ent 70.
As the concentration of halogen within the water body 76 in-
ereases, the liquid can be drained and replaced by ~resh water
to maintain an arrangement for separating escaping halogen fro~
- the carbon dio~ide which is released in the reaction compartment 22.
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GE2-67.~
4~7
g
Referring now to compartment 16; this compartment in-
cludes a hydrogen collection line ~0 including a valve 82
to allow escape o~ hydrogen gas from compartment 16 for
appropriate subsequent use, such as direct burning or elec-
trical genera~ion by a fuel cell. In the schematically
illustrated apparatus for performing the method of the present
invention, the hydrogen is used as the fuel in a fuel cel~
,~' 90 which is also supplied with oxygen from an appropriate
; oxygen source 92. In this manner, an electrical potential
is created across leads 94, 96 of fuel cell 90, ~hich leads
are used to power any appropriate load, schematically illus-
trated as load 10.
The celL or device A is used to electrically decompose
the halogen acid in the solution which constitutes electrolyte
E. The concentration of the halogen acid in the elec~rolyte
is an important feature to maintain the general efficiency of
device or cell A. The voltage across electrodes 10, 12 is below
the decomposition voltage for water; therefore, the water which
is used with the halogen acid is not electrically decomposed
by the electrolysis process. Thus, thc water within the ~lectro-
lyte forms a solution of halogen acid for electrolysis of the
acid. One of the ~eatures of the present invention is an arrange-
ment for increasing the concentration of the halogen acid within
the water forming the electrolyte solution. This requires hydro-
' 25 genation of the halogen released ~y electrode 12, which halogenis dissolved in electrolyte E. Thus7 the halogen released dur-
ing the electrolysis process is immediately dissol~ed in~o the
solution. The dissolved halogen is then hydrogenated within
compartment 22 to form additional halogen acid or the electrol-
, 30 ysis process.' When the'ceIl or device'A uses chlorine as thehalogen, hydrochloric acid is formed in the electrolyte. ~e-
" ' cause of the high concentration of the hydrochloric acid withinthe'eIectrolyte'solution, there is an insignificant amount of
hypochlorous acid in the`electrolyte. Thus, the over-voltage
or over potential associated with oxygen is not a factor in
the decomposition proces's between electrodes 10, 1~.
To increase'the'concentration of the halogen acid, an agent
is used in the'reaction area of compartTnent 2.2 to promote the
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- 10 -
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hydrogenation of the halogen. In the preferred embodiment
as will be described wi~h respect to Example I, the agent is
ungraphitized carbon particles having a relatively small size.
This carbon is oxidized to form carbon dioxide as previously
- 5 discussed so that the energy of the carbon is used in the
chemical process involved in the creation of the halogen acid
which is subsequently electrically decomposed in the electrolysis
aspect of device or cell A. By increasingthe hydrogenation
of the halogen, such as chlorine, dissolved in ~he electrolyte
E, the concentration of the acid in the electrolyte solution
can be drastically increased over other processes wherein halo-
gen is absorbed into water to form acids. In the past, when
halogen wasabsorbed in a water solution, a very low acid con-
` centration was obtainable, i.e. below about 3%. Thus, absorp-
tion of halogen in water to produce halogen acid was not useful
for efficient electrolysis of the resulting acid solution. It
has been found that chlorine, bromine and iodine can be con-
tinuously dissolved into the aqueous acid solution formed by
these halogens and that the dissolved halogens can be hydro-
' 20 genated in the presence of carbon particles to produce make-up
halogen acids at concentrations higher than about 3%. It was
found that graphitized carbon promotes hydrogenation of the
`. disclosed halogen into the halogen acid solution at a rate
' which diminishes sharply as added acid strength increases. This
~'25 concept is illustrated in curve 1 of FIGURE 2. Thus, in hydro-
chloric acid, carbon particles which are graphitized particles
promote hydrogenation of the acid at a relatively rapid rate
until a concentration is obtained, which concentration is found
to be'approximately 5%. Thus, graphitized carbons can be used
` 30 if the concentration of the hydrochloric acid-or other halogen
acid is to be`relatively low. However, higher concentration of
the halogen acids produces a superior and more efficient electrol~
ysis process. It has been found that if the carbon particles
are ungraphitized carbon, they promote the hydrogenation of
the dissolved halogen into the'acid solution at a rate which
does not diminish as the concentration of the acid increases at
~`~ least to a concentration of 20%-30V/o~ This is shown in curve 2
of FIGURE 2. For this reason, the'preferred embodiment of the
.. ~ .
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GE2 6~7.
4~ ~
present invention uses ungraphi~ized carbon. By using un-
graphitized carbon particles as the energy source for hydro-
genation of dissolved halogen within electrolyte E, the carbon
of the particles is consumed to ~orm carbon dioxide. ~onse-
quently, carbon is used in the process of making hydrogen so
that the energy of the carbon is released in the process. This
energy is used to provide hydrogen which has vastly superior
burning and energy creating characteristics than the carbon. For
this reason, ungraphi~ized carbon is pre~erred in the present in-
vention and the invention is directed to the concept of convert-
ing carbon in the presence of water into hydrogen wherein carbon
dioxide is formed as a by-product. ~IGURE 2 also shows curves
3 and 5 which are related to the hydrogenation by catalysts
other than graphitized carbon, within compartment 22. The
catalysts used to produce these two curves are ruthenised titanium
; and platinised titanium, respectively. As can be seen in FIGURE
2, the two catalysts, which can be used with added water only
; in the reaction zone 22, produces a concentration of hydrochloric
acid or other halogen acid generally comparing to the graphitized
carbon of curve 1 which acts as a catalys~. FIGURE 2 illustrates
that the use of ungraphitized carbon as shown in curve 2 is the
preferred source of energy for the reaction within reaction
chamber 22. By using ungraphitized carbon, the concentration of
the halogen increases substantially to approximately 20% hydro-
` chloric acid. The material used in creating the curves of FIGURE
` 2 was ATJ graphite ~rom Union Carbide Corporation as the graph-
itized carbon. The ungraphitized carbon was Grade 37 coke-carbon
from Airco Speer Corporation. This ungraphitized carbon is used
in Example I as will be described later. The ruthenisèd titanium
was prepared by the well known method of air heating~porous
titanium dipped in a ruthenium chloride solution. The platinised
titanium, was prepared by a well known method of air heating
porous titanium dipped in a chloroplatinic acid solution. In
FIGURE 2 it is noted that there is a rapid increase in the
halogen acid concentration in a solution containing dissolved
; halogen below about 3% concentration. A very slow increase in
concentration beyond about 5% of halogen acid was found for all
the materials, except the ungraphitized carbon. The concentration
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GE~ 22~
8~7
- 12 ~
of the halogen acid when using ungraphitized carbon is a sub-
stantially constant rate even at the low~r levels and this
rate con~inues ~or an acid concentration within water of up to
and beyond about 20% acid in solution. Thus, a dissolved
halogen is continuously hydrogenated when using ungraphitized
carbon. When using the other three agents, the hydrogenation
of the halogen continues until the solution reaches about 5%
acid. At this point, hydrogenation of the halogen essentially
stops. Still, the 5% concentration is higher than the hydrogena-
tion level obtainable without the selected agents. Thus, any
of the four materials as so far described and illustrated
graphically in FIGURE 2 can be used to increase the hydro-
genation level of the absorbed halogen within an acid solution
used for the electrolyte in device or cell A. The ungraphitized
carbon is the preferred hydrogenation material.
Although the reason for the continued hydrogenation of the
chlorine or other halogen beyond a low level when using un-
graphitized carbon is not known it is believed that this phenom-
enon is related to the over potential characteristics of un-
2~ graphitized carbon in a halogen acid solution. This concept
`- is shown in FIGURE 3 wherein the over potential or over-voltage
in millivolts for u~graphitized carbon and graphitized car~on
are compared. This graph was constructed by using electrodes
of graphitized and ungraphitized carbon in different concentra-
tions of hydrochloric acid and measuring the over-voltage at
these concentrations. In this graph, it i5 noted that both the
ungraphitized and graphitized carbon retain a relatively low over
potential up to approximately 20% hydrochloric acid and this is
; the percentage of hydrochloric acid at which the hydrogen chloride
: 30 ¦ commences to disassociate from the water. Thereafter, the graph-
;~` itized carbon substantially increases its over potential with
respect to the halogen whereas ungraphitized carbon continues
-` on at approximately the same over potential or over-voltage
` level. Thus, the ungraphitized carbon continues to retain a
; 35 relatively low over-voltage or over potential. At the surface
of the carbon particles in the present invention, the hydrogena-
tion of the halogen takes place. The concentrations of the
halogen acid at the particle surfaces is relatively higher than
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: GE2-6224
- 13 -
' the total acid solution concentration because the produced
acid accumulates at the reaction surface. Consequently,
- the ungraphitized carbon continues to hydrogenate the halogen
at the carbon-surfaces whereas the graphitized carbon has a
substantially higher over potential or over-voltage at this
level and stops hydrogenation at about 18% acid in ~he area
of the carbon surfaces. This produces an acid concentration
within the total electrolyte E of approximately 5% whereas the
- capability of the ungraphitized carbon to retain a low over-
voltage or over potential continues to hydrogenate even though
the concentration of the halogen acid at the surface of the
carbon increases substantially above'the 18-20% solution or
~'` c.oncentration level.
The actual test recorded in EIGURE 3 relates to over-voltage
or o~er potentîal which is generally the voltage or potential
greater than the theoretical po~ential to produce a given elec-
trbchemical reaction. To obtain the chart shown in FIGURE 3 to
illustrate the relationship between graphitized and ungraphitiæed
` carbon as an over potential factor, the over-voltage between
`. 20 two eIectrodes and hydrochloric acid having various concentrations
was measured at the electrode. Ten milliamps per square inch
of current density was used. As the concentration was increased,
the over potential for the ungraphitized carbon electrode was .'
substantially constant at about 7 millivolts at 5% hydrochloric
acid concentration and raised in a substantially uniform manner
to about 8 millivolts at 37% concentration of hydrochloric acid.
As to graphitized carbon electrode, the over potential was
abcut 5 millivolts over a range'of concentration of 5-18% acid
within the solution. As the acid concentration was thereafter
increased, the graphitized carbon electrode used in the test
shows a very sharp over potential or over-voltage rise reaching
about 45 millivolts at 24% concentration of hydrochloric acid.
'.~ As the hydrochloric acid then continued to increase in'
. percentage, the graphitized carbon showed an over potential of
,`: 35 about 45-46 millivolts ~hrough'acid concentrations of 24-37%
`'~ concentration, This re~ationship is illustrated in FIGURE 3.
Thus, since'the'ungraphitized carbon electrode in the test
~-~' indicated no substantial increase'in the'over potential at the
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GE2-6224
4~7
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electrode as the concentration of acid increased> it has been
theorized that when using ungraphitized carbon in the method
of the present inven~ion for the reaction particles within
compartment 22, the over potential at the carbon particle
surfaces does not substantially increase even though the con-
centration of the acid within the reaction zone and adjacent
the surface does increase. By the experiment using graphitized
and ungraphitized carbon in hydrochloric acid as illustrated in
FIGURE 3, it is shown that the ungraphitized carbon does not
have a substantial change in over potential with respect to a
halogen, such as chlorine. This indicates that the over poten-
tial of the ungraphitized carbon particles remais subs~antially
constant in the reaction zone 22 of device or cell A shown in
FIGURE 1. Thus, ungraphitized carbon is used in the preferred
em~odiment of the invention with all the halogens such as
chlorine, bromine and iodine.
From the above description, the present invention involves
a novel means of using coal or other carbon for the manufacture
- of halogen acids which are electrolytically decomposed into hydro-
gen. The by-product is carbon dioxide. The released halogen
is dissolved into electrolyte and then hydrogenated within the
reaction zone of the cell A to produce a con~inuous process
wherein the dissolved halogen in a circulated electrolyte is
rehydrogenated by the use of carbon. Since hydriodic acid has
a much lower electrical disassociation voltage than water or hydro-
chloric acid, this acid can be used in a more efficient manner
than hydrochloric acid. Examples II and III relate to the use
of this halogen acid and improvements in the method of the
present invention as they relate to hydriodic acid.
Referring now to FIGURE 4, this figure is a modification
of the preferred embodiment shown in FIGURE 1 and is used for
a halogen acid as previously described. In this particular
example, iodine is used as the halogen; however 9 the halogen
could also be chlorine.` Cell B includes hydrogen collecting
3~ compartment 110 and iodine collecting compartment 112. Within
` compartment 110 is a hydrogen collecting electrode 114. In a
; like manner, an iodine collecting electrode 116 is
provided within compartment 112. A conduit 118 connects
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GE~ 6224
- 15 -
com~artments 110, 112 and includes an appropriate me~brane 120
of the type previously described. A D.c. power supply schematically
illustrated as power supply 122 applies a D.C. voltage across
electrodes 114, 116 which voltage is in the general range of
.6-.7 volts D.C. This voltage is selected ~o electrically de-
compose the hydriodic acid within electrolyte E. Of course,
this same arrangement could be used for the other halogen such
~' as chlorine and bromine. A hydrogen outlet 130 directs hydrogen
from compartment 110 ~o an appropriate storage or using device.
, In this illustrated embodiment, a separate reaction tank 140 is
' provided through which is continuously circulated the electrolyte
E by an appropriate inlet 142 having a pump 144. This pump
pumps dissolved halogen and the electrolyte into the reaction
tank 14~. The heat caused by the electrical decomposition process
is suficient heat to retain necessary reaction temperature
within tank 140. Thus, additional heat is not required and the
electrolyte within tank 140 can be heated to the boiling point
if sufficient waste heat is created by cell B. Outlet 146 di- ''
rects electrolyte E from reaction'tank 140 to cell B through
an appropriate filter 150 which removes any unwanted impurities
, within the electrolyte as it is being circulated back to cell B.
' A center intake'l52 is used to collect the electrolyte from tank
'~ 140. Impeller 154 circulates the electrolyte in tank 140 out-
wardly so that the carbon particles are generally spaced from
: 25 intake 152 and are not directed toward filter 150. In this
illustrated embodiment of the invention, line 160 is used or
..troducing iodine or HI into the tank at the start-up of the
~" process. Thereafter, make-up iodine is not generally required
in the continuous operation process. A line'l62 allows the
` 30 introduction of hydrochloric acid into the reaction chamber
140. As will be'described later, hydrochloric acid has a
' decomposition voltage'substantially higher than the hydrogen
', iodine or hydriodic acid and thus can be'used with water within
~: electrolyte E without actually entering into the e~ectrolysis
process. The'hydrochloric acid has an advantage which will be
described later. It reduce's the'voltage'necessary between
electrodes 114,116. Any reduction in voltage'is a savings ln
electrical energy which'thus increases the el'ectrical eficiency
.
```:
GE2-62Z~
- 16 -
of a device using the present invention. ~ine 16~ is use~
for introducing water into the reaction chamber 140. The
purpose of the water has been previously described. In
accordance with this particular illustration of the invention,
coke is introduced thro~gh line 166 and is treated by nitric
acid in tanl~ 170. Thereafter, the coke particles are washed
in a tank 172 and the residual acid is removed by line 174.
'~ Thus, the nitric acid treated coke particles are introduced
in the reaction chamber 140 in the desired amount to promote
hydrogenation of the iodine dissolved within electrolyte E
pumped from cell B through inlet 142. An appropriate vent for
' the carbon dioxide gas is illustrated as line 18G having a
check valve 182. Of course,' a water trap could be used as
previously described with respect to the embodiment of the
cell A as shown in FIGUR~ 1. The general operation of cell B
and i~s associated reaction chamber 140 is the sa~e as ~he
; operation of device or cell A shown in FIGURE 1. The advantages
of using thP nitric acid washed carbon particles and hydrochloric
' acid in an iodine pr'ocess are explained hereinafter and used in
' 20 Example'III. Again, the device'shown in FIGURE 4 produces hydro-
gen by the'use of water and ungraphitized carbon particles. Of
course, graphitized carbon could be used. In the former instance>
the carbon is consumed in the chemical process used in pro-
ducing the halogen acid necessary for the electrolysis process
carried out by cell B.
~` Example I
' A reaction or chlorine compartment of cell A had a capac-
` ity of about 500 ml and was filled with 300 ml of water. This
`'` fills the hydrogen compartment, which was the same general
' 30 size, to this same leveI. The hydrogen electrode was graphite
which had beèn platinised by dipping it in chloroplatinic acid
~`; and heating it in air. This reduces the'el'ectrode over potential`'` with hydrogen. In a similar manner, the'chlorine electrode was
formed from graphitized carbon or graphite and was boiled in
nitric acid for 30 hours. The intermediate membrane between
`~ the compartments was formed from DuPont 120 Nafion with a thick-
" ness of 10 mils. The hydrogen ions pass between the cham'bers
' to establish'electr'ical continuity and generally uniform acid
- concentration.
GE2-6224
37
- 17 -
Approximately 20 grams of powdered coke was charged in-
to the reaction compartment and the water was heated to about
80C. The coke was standard ungraphitized carbon sold by
Airco Speer Corporation as Grade 37 coke-carbon. The particle
size was such tha~ it passed through a standard 6 mesh screen
and not through a standard 14 mesh screen. This powder was
then slurried in the water and held in suspension by the im-
peller. Thereafter, chlorine gas was introduced into the slurry
of the reaction compartment and the HCl concentration continued
to raise to be~ween 20%-25~/o by weight, whereas when using the
same procedure with ATJ graphite from Union Carbide Corporation,
ruthenised titanium and platinised titanium instead of the un-
graphitized coke, the concentration peaked out at about 5% HCl.
To reach the 25% HCl, about 140 grams of chlorine reacted with
the 20 grams of coke'to produce'about 140 grams HCl in solution.
A voltage'of 1.2 volts D.C. was applied across the elec-
trodes to produce about 1.0 amperes of current flow through the
electrolyte. About 1.1 volt D.C. was used for decomposition
of the acid. ~Iydrogen was produced at the hydrogen electrode
and directed from the unit. The chIorine produced at the chLorine
' electrode was reused to combine with water and carbon to pro-
'~ duce make-up ~Cl. Carbon dioxide was released by this process
' and was passed through water hath 76. In the process 20 grams
; of water and 6 grams of the coke carbon are consumed per hour
2~ to produce 2 grams of hydrogen per hour while maintaining the
acid concentration at about 20%.
After the process came on line, the heat generated by the
.. I2R drop across the electrodes was sufficient to maintain the
electrolyte at an elevated temperature above 80C. Heater 60 ~,
was disconnected during the process. Consequently, 6 grams
of carbon produce 2 grams of hydrogen per hour with a theoret-
~ ical heating capacity of 265 Btu. The electrical energy used
;~ per hour is about 66 watt-hours which converts into approximately
226 Btu per hour. The electrical energy of 226 ~tu produced
' 35 hydrogen with a converted heating capacity of 26~ Btu.
~i Example II
The same basic process as used in Example I was performed
` in cell A with hydriodic,acid as the electrolyte acid. In
.
.
- 18 -
this instance the voltage was reduced to about .6-.7 volts
D C, and about 2 grams of coke were used as make-up ungraph-
itized carbon per hour. T~is example produced 2 grams of
hydrogen at a heating capacity of 264 ~tu with 32 watt
hours or 110 Btu input per hour of electrical ~nergy.
Hydrogenation Effectiveness Factors
A study of the halogens, chlorine, bromine and iodine,
for use in the processes described in Examples I and II indi-
cated several factors which affect the effectiveness of the
processes, but not the basic theory or operability of the
processes Hydrogenation of the halogens, even at con~entra-
tions about 3%-5%, allows the system to operate ef~ectively.
The hydrogenation rate of the halogen is inversely related to
the free energy of thé halogen acid which is lowest for the
chlorine acid and is highest ~or the iodine acid. ~onsequently,
hydrogenation, or acid formation, is more rapid and easily
accomplished with hydrochloric acid. However, the solubility
of the halogen in its respective acid is greatest for iodine
in hydriodic acid and less for chlorine in hydrochloric acid.
Taking these'factors into consideration, certain modifications
in the rate of acid ~ormation in the coke-water-halogen system
have been discovered.
By treating the coke with nitric acid by passing the coke
through hot nitric acid, the rate of hydrogenation of the
halogens in the coke process is increased. The increase in
hydrogenation rate is a factor of about ten for iodine and
substantially less for chlorine. The reason for this action is
not known; however, it is theorized that t~e nitric acid Leduces
the absorption of the'halogen into the coke or ungraphitized
carbon, i.e.' carbon which has not been heated to over about
2000~. The'absorption reduction appears to result in a re-
duced ha~ogen over-potential at the carbon surface and, thus,
increases the'rate of hydrogenation. The iodine is affected
more by this process. In summary, one'improvement in the basic
method of Examples -I and II is the pretreatment of the coke
particles by nitric acid.
Since solubilit'y of the halogen in its acid is important
to ultimate'hydrogenation of the invention, an improvement in
- 19- '
solubility is advantageous. In practice this has been accom-
plished by adding sodium chloride ~o iodic acid. This salt
increased the rate of solubility of iodine in hydriodic acid,
but decreased this rate for chlorine in hydrochloric acid.
Consequently, the rate'of hydrogenation may be adjusted by a
salt, ~uch as sodium chloride.
The rate of reaction is also affected by the free energy
of the acid at the carbon surface of the particles. As prev-
iously stated, the higher the free energy, the lower ~he hydro
genation rate.' It has been found that this rate can be affec~ed
by adding acids of a lower Icnown free energy level ~o acids of
higher free ener~y leveIs,For instance, if hydrochloric acid,
having the lowest free energy of ~he halogens under considera-
tion, is added to a system based upon hydrogen bromide or
- 15 hydrogen iodide 9 the hydrogenation ra~e is increased. In a
like manner, hydrobromic acid or hydrogen bromine can increase
the hydrogenation rate'of a hydrogen iodide sy tem. This
phenomenon apparently occurs because of the free energy modi-
fication at the carbon surface. Also, these added acids are
?O not decomposed because they require a higher voltage than used
for the base acid.
In summary, factors such as treatment of the coke with
; nitric acid, using a solubility modifier and adding a second
halogen acid to the system are helpful in controlling the
effectiveness of the basic system described in Examples I and
II. Sufficient solubility of the halogen in its acid is needed
to capture the'releàsed halogen at the halogen electrode for
, hydrogenation in the'system. In addition, low over po~ential
` of the ungraphi~ized carbon a~ higher concentrations retains
''~` 30 the hydrogenation process beyond the normal lower ~oncentrations
obtained by merely reacting halogen with water.
The interaction of the experimentally determined effecti-
"` veness factors for the'general process o~ Examples 1 and II
can be manipulated to obtain proce'ss reactions having ~urther
improved electrical and chemical char'acteristics. Theise
`~ factors act upon the'solubility and over potential of the carbon
to control and facilitate'hydrogenation at higher acid concen-
trations, in the`range'of 5%-25% in the case of h~drogan
chlorine for example.
.
~s
. ~.
.. . .
GE2-6224
- 20 -
, Example III
- Another example was performed using the effectiveness
factors experimentally obtained and explained above. In this
example the ~hree hydrbgenation rate modification factors were
used for a system similar to Example II using hydrogen iodide
in ~he electrolyte solution. Hydrogen was obtained from the
electrolyte formed by hydrogenation of iodine which is the pre-
', ferred system of the present invention. In this example, cell
B as shown in FIGURE 4 was used. The ungraphitized carbon,i.e.
coke, was treated with nitric acid and then heated to remove
excess nitric acid. This produced an increase in the iodine
hydrogenation rate; however, the small amount of nitric acid
residue on the'carbon particles exhibited no apparent dele-
' terious effect on the total system. In this example a small
amount of titanium tetrachloride was added whic~ is a sa~t to
further increase the hydrogenation rate and reduce the corrosive-
~` ness of the acid mixture. This salt increased the solubility
' of the electrode released iodine. A substantial amount of
hydrochloric acid was used with the hydrogen iodiae electroly~e.
The hydrochloric acid lowered the decomposition voltage of the
HI electrolyte; however, it did not enter into ~he electrolysis
since the voltage across the electrodes was about .3 volts D.C.
Without a substantial amount of HCl, the voltage of the HI
~ cell was about .6-.7 volts D.C. This voltage of .3 volts is
`: 25 sufficient to electrically decompose the HI, but, not the HCl,
; which requires about 1.2-1.3 volts. To obtain a .3 volt de-
composition voltage for the HI cell without the HCl additive,
the HI concentration would need to be about 50% HI by weight
in water. In this example'the .3 volt decomposition of HI
~; 30 electrolyte was obtained by 20% HCl by weight and 1% by weight
HI. Consequently, this example'produced increased hydrogenation
of iodine, reduction in the decomposition voltage of HI and
reduction in the'amount of iodine required, which is considerably
,'` more'expensive'than chlorine. This example'contained:
' 35 (1) Airco Speer Grade 37 coke''carbon boiled for 8
hours in constant boiling nitric acid washed in
water.
(2) 20% by weight HCl.
.
.~
GE2-6224
- 21 -
(3) 1% by weight HI.
(4) l~/o by weight titanium tetrachloride.
(5) Remainder water.
The temperature of the cell was about 108C and ~he
electrolyte was stirred to prevent settlin~ of the carbon
particles. The decomposition voltage to produce hydrogen was
.3-.4 volts D.C. and hydrogen was produced at 2 amperes of
current. The cell was sealed from air to prevent oxidation
of the HI electrolyte.
` 10 Of course, other modifications could be made in the
various processes illustrated in carrying out ~he present
invention wi~hout departing from the scope of the invention
which relates to the concept of producing hydrogen from the
electrolysis of a halogen acid electrolyte which absorbs the
released halogen and circulates ~he absorbed halogen with the
electrolyte in a reaction area to rehydrogenate the halogen
` with the use of water and water or carbon. The released
n hydrogen itself is not required for the rehydrogenation and
is totally useful for external purposes such as heating or
generation of electricity, to name two examples.
Modifications
Referring now to FIGURE 5, a modification of the preferred
` embodiment is illustrated. In this embodiment the cell D in-
cludes a housing 20~ with a Nafion membrane 202 having surface
mounted electrodes 204, 206. A voltage source applies a working
" voltage across leads 210, 212 so that the membrane produces an
electrolysis function. A halogen compartment 220 provides a
gaseous acid vapor at the electrode face of the membrane to
allow electrolysis to form a halogen gas in compartment 220
At the same time, hydrogen is separated and accumulated in
compartment 222, from which it exits by way of conduit 224.
Disassociated halogen, in the example chlorine, is
conveyed in gaseous form from compartment 220 to a reaction
~`~ tank or area 230 by a means represented as pump or blower
:35 232 in conduit 234. Vapor from conduit 234 is forced into
chamber 240 defined by a body of water 242 and an upper
bed of ungraphitized carbon 244. surners 250 in line 252
heat the water in body 242 in the boiling temperature to
produce water vapor. This vapor together with
G~-6~
~ a ~ 3 7
- 22 -
the vapor from conduit 23~ reacts with the carbon to hydrogenate
the chlorine into hydrochloric acid vapors which are carried by
condu;t 260 to the lower portion of halogen compartment 220
wherein the electrolysis releases chlorine for a continuous cycle.
Condenser 270 removes water vapor. The heat of the electrolysis
process maintains the vaporized condition of the ~irculated
constituents in compartment 220 and conduit 234.
To remove the carbon dioxide from the closed loop, a vent
272 having a small diameter, i.e. about 1120th o the area of
~L0 conduit 234, is provided in the coolest area of the circuit.
: A condenser 274 condenses the water vapor which absorbs any HCl.
large volume of carbon dioxide with traces of halogen then
passes from the condenser. A dry carbon bed 276 then removes
the halogen, if necessary.
The catalyst concept used in the present invention can be
used in stripping a halogen from a gas stream since it increases
the obtainable concentration of halogen in water. FIGURE 6 shows
a system for utiliæing this aspect. A tank 280 is partially
filled wit~ water from valved conduit ~g2. Graphitized carbon,
ruthenised titanium, platinised titanium or mixtures thereof,
in particle form, is introduced into the water through feed
line 284. A gas stream, illustrated as chlorine, is directed
by valved conduit 286 into a diffuser 290 at the lower portion
of tank 280. As the halogen bubbles through the water in the
presence of the catalyst, the halogen is formed into hydrohalic
acid to higher concentrations than obtained by water itself.
A drain 292 ultimately drains tank 280. By this arrangement,
` more chlorine can be stripped from a gas stream. Any insoluble
gases pass from tank 280 by outlet 294.
