Note: Descriptions are shown in the official language in which they were submitted.
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I
Process for the oxidation of hydro~en chloride
The present invention relates to an improved process for the preparation of
chlorine from hydrogen chloride.
In the industrial use of chlorine for the preparation of organic compounds, large
amounts of hydrogen chloride form. Thus, for example, in the production of
isocyanates which serve as raw materials for plastic foams and paints, between
0.58 and 1.4 t of hydrogen chloride form per ton of isocyanate. The chlorinationof hydrocarbons, e.g. of benzene and toluene, likewise results in large amounts of
hydrogen chloride. Thus, in the preparation of chlorobenzene, 0.32 t of hydrogenchloride forms per ton of chlorobenzene.
Various processes are known for disposing of hydrogen chloride. Thus, for
example, the hydrogen chloride arising can be split electrolytically into chlorine
and hydrogen after conversion into aqueous hydrochloric acid. This process has
the disadvantage of the high requirement for electrical energy. About 1600 KWh
are required per ton of hydrogen chloride to be electrolysed. A further
disadvantage is the high capital costs of providing the electrical energy, of
transforming and rectifying the electric current and especially of the electrolysis
cells.
For this reason, attempts have already been made to carry out the oxidation of
hydrogen chloride chemically using oxygen and in the presence of catalysts. Thisprocess is termed the "Deacon process" in textbooks of inorganic chemistry (see,e.g., Lehrbuch der anorganischen Chemie, [Textbook of inorganic chemistry],
Hollemann-Wiberg, 40th-46th edition 1958, pp.81 and 455). The advantage of this
Deacon process is that no energy needs to be supplied from outside for the
reaction. However, a disadvantage in this process is that the reaction can only be
carried out to an equilibrium position. Therefore, after the Deacon process has
been carried out, it is always necessary to fractionate a mixture which still
contains hydrogen chloride and oxygen.
Attempts have already also been made to remedy this fundamental disadvantage of
the Deacon process by a procedure in two stages. The use e.g. of catalyst systems
is described, for example Cu(I) salts (see US-A 4 119 705, 2 418 931, 2 418 930
Le A 30 707-US 2 t 62 6 ~ ~
and 2 447 323) or vanadium oxides (see US-A-4 107 280) which are able to
absorb oxygen and hydrogen chloride and, under other experimental conditions,
e.g. at higher temperature, to elimin~te chlorine again with reformation of the
original catalyst. The advantage of such a concept is that the reaction water
formed in the reaction of hydrogen chloride with the oxygen-containing catalyst
can be separated off in the 1st stage, and highly enriched chlorine is formed in the
2nd stage. A disadvantage in this concept is that the catalyst system must be
heated and cooled between the two reaction stages and, if appropriate, must be
transported from one reaction zone to the other. In combination with the relatively
low ability of the catalysts used to release oxygen - e.g. 1 t of vanadium oxidemelt can release only about 10 kg of oxygen - this means considerable technical
complexity which consumes a large part of the advantages of the Deacon process.
The concepts existing to date for the industrial implementation of the Deacon
process in a single-stage reaction are unsatisfactory. The proposal made by Deacon
in the 19th century, to use a fixed-bed reactor having a copper-containing catalyst
using air as oxidizing agent, provides only highly dilute, impure chlorine, which
can at the most be used for the preparation of chlorine bleaching liquor (see
Chem. Eng. Progr. 44, 657 (1948)).
An improved technique was developed with the socalled "Oppauer-process" (see
DE 857 633). This uses, for example, a mixture of iron(III) chloride and potassium
chloride which, as a melt at temperatures of approximately 450C, serves as
reaction medium and catalyst. The reactor used is a tower, lined with ceramic
material, having a centrally incorporated inner pipe, so that passing in the
feedstock gases hydrogen chloride and oxygen effects a circulation of the molten salts.
However, an exceptional disadvantage in this concept is the very low space-time
yield (about 15 g of chlorine per litre of melt and per hour). For this reason, the
Oppauer process is not advantageous in comparison with electrolysis of hydrogen
chloride.
The poor space-time yield is accompanied by a large number of further
disadvantages, such as large standing volumes of molten salts, large apparatus
LeA30707-US 2~ 6~641
volumes with correspondingly high capital costs and cost-intensive maintenance.
Furthermore, thermal management of such large melt volumes can only be
performed very poorly with respect to temperature maintenance, heating up and
during shutdown of the plant, which is further reinforced by the thermal inertia of
the large reactors.
In order to avoid these disadvantages, it has been proposed to carry out the
reaction at a lower temperature, e.g. below 400C. However, at these temperatures
there is the possibility of solids separating out of the copper salt melt. The salt
melt has therefore been applied to a particulate inert support, e.g. silica or
aluminium oxide, and the reaction has been carried out in a fluidized bed (see GB-
B 908 022). A new proposal recommends chromium-containing catalysts on inert
supports, a temperature below 400C likewise being chosen (see EP-A 184 413).
In all of these proposals to solve the problems of the Deacon process using the
fluidized-bed technique, the unsatisfactory stability of the catalysts and their highly
complex disposal after deactivation is highly disadvantageous. In addition, the fine
dust which is unavoidable in the fluidized-bed technique poses problems in its
removal from the reaction mixtures. Moreover, the fluidized reaction zone which
requires a hard catalyst leads to increased erosion which, in combination with the
corrosion caused by the reaction mixture, produces considerable technical
problems and impairs the availability of an industrial plant.
A further disadvantage of the procedure using molten salts on inert supports, i.e. at
temperatures of above 400C, is that a satisfactory reaction rate and, consequently,
a good space-time yield is possible only if a relatively high oxygen excess is
employed. However, this requires work-up of the reaction mixture using a solvent,
e.g. CCl4 or S2Cl2 (see DE-A 1 467 142).
The object was therefore to find a process which permits the oxidation of
hydrogen chloride with oxygen in the simplest manner possible and with a high
space-time yield and which uses the technique of employing a system of molten
salts as catalyst which is advantageous per se in comparison with the fluidized-bed
30 technique for the Deacon process and avoids the disadvantages of the previousvariants, e.g. the two-stage salt melt process or the single-stage Oppauer process.
Le A 30 707-US
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It would, moreover, be advantageous in this context if a smaller oxygen excess in
comparison with stoichiometric conditions could be employed.
A process has now been found for the oxidation of hydrogen chloride with oxygen
in the presence of a salt melt, which is characterized in that
5 - a salt melt which contains metal salts, salts depressing the melting point and
if appropriate promoters is employed,
- temperatures between 300 and 600C are employed,
- the salt melt is dispersed in the gas containing hydrogen chloride and
oxygen in such a way that contact times of 0.01 to 100 seconds result,
10 - the reaction gases are cooled and hydrogen chloride and water are separated out of the reaction mixture,
i~
- the reaction gases freed from most of the water and some of the hydrogen
chloride are freed from residual water using sulphuric acid and
- the gas mixture then essentially containing chlorine, hydrogen chloride and
oxygen is compressed to 2 to 10 bar, the chlorine is liquefied by cooling
and, if appropriate after further purification, is separated off, and
- the remaining, essentially oxygen-containing gas is recycled in whole or in
part to the reaction zone.
In principle, hydrogen chloride of any origin can be fed to the process according
20 to the invention, e.g any hydrogen-chloride-containing gas mixtures. Preference is
given to hydrogen-chloride-containing gas mixtures as arise in chlorinations andphosgenations. Such hydrogen-chloride-containing gas streams can be fed into theprocess according to the invention in the gaseous state or as aqueous hydrochloric
acid absorbed in water. The gas streams containing hydrogen chloride may,
25 depending on their origin, possibly contain organic impurities, e.g. carbon
monoxide, carbonyl sulphide, phosgene and chlorinated and nonchlorinated
LeA30 707-US 21 62641
organics, for instance various chlorobenzenes. It is generally expedient to keep the
content of organic impurities in the hydrogen chloride to be used as low as
possible in order to minimize formation of undesirable, frequently toxic
chlorinated organics. This can be performed in a manner known per se, e.g. by
5 absorption with water and/or by adsorption onto an adsorbent, e.g. activated
carbon.
The oxygen required can be used as such or in a mixture with preferably inert
gases. Preference is given to gases having oxygen contents above 90/0 by volume.
Salt melts without promoters can be e.g. mixtures of metal salts and salts
10 depressing the melting point. Metal salts can be salts which are either catalytically
inactive or catalytically active for the oxidation of hydrogen chloride with oxygen.
Metal salts which can be used are, e.g., salts of metals of main groups I to V and
subgroups I to VIII of the Periodic Table of the Elements. Preference is given to
salts of aluminium, lanthanum, titanium, zirconium, vanadium, niobium,
15 chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, copper and
zinc. Particular preference is given to salts of vanadium, chromium, manganese,
iron, cobalt, nickel, copper and zinc. Very particular preference is given to copper
salts.
Salt depressing the melting point can be e.g. salts of metals of main groups and20 subgroups I to III and main groups IV to V of the Periodic Table of the Elements,
for example salts of lithium, sodium, potassium, rubidium, caesium, magnesium,
calcium, strontium, barium, aluminium, gallium, indium, thallium, germanium, tin,
lead, antimony, bismuth, zinc and silver. Preference is given to salts of lithium,
sodium, potassium, aluminium and zinc. Particular preference is given to salts of
25 potassium.
Salt melts without promoters are e.g. mixtures of the following type:
LiCI/KCI, ZnCI2/KCl, KCI/NaCI/LiCI, MgCI2/KCI, AICI3/KCI, AlCI3/NaCI,
V205/K2SO4/K2S207, CrCI3/NaCI/KCI, MnCI2/NaCI, MnCI2/KCI,
MnCI2/KCI/NaCI, MnCI2/AlCI3, MnCI2/GaCI3, MnCI2/SnCI2, MnCI2/PbCI2,
- ~162~41
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MnCI2/ZnCI2, FeCI3/LiCI, FeCI3/NaCI7 FeCI3/KCI, FeCI3/CsCI, FeCI3/KCI,
FeCl3/AlCl3, FeCl3/GaCI~, FeCI3/SnCI4, FeCI3/PbCI2, FeCI3/BiCI3, FeCI3/TiCI4,
FeCI3/MoCls, FeCI3/ZnCI2, FeCI3/NaCI/ZrCI4, FeCI3/KCI/ZrCI4,
FeCI3/NaCI/WCI4, CoCI2/NaCI, CoCI2/KCI, CoCI2/GaCI3, CoCI2/SnCI2,
5 CoCI2/PbCI2, CoCI2/ZnCI2, CuCI/NaCI, CuCI/KCI, CuCI/RbCI, CuCI/CsCI,
CuCI/AlCI3, CuCl/GaCl3, CuGl/InCI3, CuCI/TlCI, CuCI/SnCI2, CuCI/PbCI2,
CuCI/BiCI3, CuCI/FeCI3, CuCI/AgCI, CuCI/ZnCI2, LaCI3/FeCI2/SnCl2,
NaCI/SnCI2, FeCI2/SnCI2 and NaCI/CaCI2. Preference is given to mixtures of the
type V2O5/K2SO4/K2S2O7, CrCI3/NaCI/KCI, MnCI2/KCI, FeCI3/KCI and
10 CuCl/KCI. Particular preference is given to mixtures of the type
V205/K2SO4/K2S207, FeCI3/KCI and CuCI/KCI. Very particular preference is
given to a mixture of KCI and CuCI.
If metal oxides, e.g. V2O5, are used, these are converted into salts when the
process according to the invention is carried out.
¢ 15 The promoters to be added, if appropriate, to the salt melts can be, e.g., metal
salts of subgroups I to VIII of the Periodic Table of the Elements and/or of therare earths, for instance salts of scandium, yttrium, lanthanum, titanium, zirconium,
hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten,
m~ng~nese, rhenium, iron, ruthenium, cobalt, rhodium, iridium, nickel, palladium,
platinum7 copper, silver, gold and salts of the rare earths, for instance salts of, for
example, cerium, praseodymium, neodymium, samarium, europium, gadolinium,
and of thorium and uranium. Preference is given to salts of lanthanum, titanium,zirconium, vanadium, chromium, molybdenum, tungsten, manganese, rhenium,
iron, ruthenium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper,
cerium, praseodymium, neodymium and thorium. Particular preference is given to
salts of lanthanum, vanadium, chromium, manganese, iron, cobalt, nickel, copper,cerium, praseodymium and neodymium. Very particular preference is given to
salts of iron and copper.
Mixtures containing promoters are e.g. mixtures of the following type:
LiCl/KCl/FeCI3, LiCl/KCl/NdCI3/PrCI3, KCl/NaCI/LiCl/FeCl3,
KCl/NaCl/LiCI/NdCI3/PrCl3, MgCI2/KCI/FeCI37 MgCI2/KCI/NdCI3/PrCI37
MgCI2/KCl/LaCI37 MgCI2/KCI/CeCI37 AlCl3/KCI/FeCI37 AlCI3/KCI/NdCl3,
Le A 30 707-US 2 1 6 2 6 4 1
AlCl3/KCl/PrCl3, AlCl3/KCl/NdCl3/PrCl3, AlCl3/KCl/LaCI3, AlCI3/KCI/CeCl3,
AlCI3/NaCl/FeCI3, AlCI3/NaCI/NdCI3, AlCI3/NaCI/PrCI3, AlCI3/NaCI/NdCI3/PrCI3,
Alcl3/NaCI/LaCI3, Alcl3lNacllcecl3~ V25/K2S4/K2S27/FeCl3'
V25/K2S4/K2S207/CuCl, V2O5/K2SO4/K2s2o7lLacl3
V2OslK2So4lK2s2o7lcecl3, V2oslK2so4lK2s2o7lNdcl3
V205/K2SO4/K2S207/NdCI3/PrCl3, CrCl3/NaCl/KCl/FeCl3, MnCI2/KCl/FeCI3,
MnCI2/KCI/LaCl3, MnCl2/KCl/CeCI3, MnCI2/KCI/NdCl3/PrCI3,
MnCI2/AlCI3/FeCI3, MnCI2/KCI/NaCI/FeCI3, MnCI2/SnCI2/FeCI3,
MnCl2/SnCl2/LaCl3, MnCl2/SnCl2/CeCl3, MnCl2/SnCl2/NdCl3, MnCl2/SnCl2/PrCl3,
MnCl2/SnCl2/NdCI3/PrCI3, FeCI3/KCl/NdCl3/PrCl3, FeCl3/LiCl/CuCI,
FeCl3/NaCl/CuCI, FeCI3/KCl/CuCI, FeCI3/ZnCl2/CuCl, FeCl3/NaCl/ZrCl4,
CoCl2/SnCl2/FeCl3, CuCI/KCI/FeCI3, CuCI/AlCI3/FeCI3, CuCI/BiCI3/FeCI3,
CuCl/CsCI/FeCI3, CuCI/FeCI3, CuCl/SnCl2/FeCl3, CuCl/ZnCI2/FeCI3,
CuCI/TlCl/FeCl3, CuCl/KCl/NdCl3, CuCl/KCI/PrCI3, CuCI/KCl/LaCI3,
CuCI/KCl/CeCl3, CuCl/KC1/NdCl3/PrCl3, ZnCI2/KCI/FeCI3,
ZnCI2/KCl/NdCl3/PrCl3. Preference is given to mixtures of the type:
V205/K2SO4/K2S207/FeCl3, FeCl3/KCl/NdCl3/PrCl3, CuCl/KCl/FeCl3,
CuCl/AlCl3/FeCl3, CuCl/BiCl3/FeCl3, CuCl/CsCl/FeCl3, CuCl/FeCl3,
CuCl/SnCl2/FeCl3, CuCl/ZnCl2/FeCl3, CuCl/KCl/NdCl3, CuCl/KCl/PrCl3,
CuCl/KCl/LaCl3, CuCl/KCl/CeCl3, CuCI/KCI/NdCl3/PrCl3, CeCI3/NaCI/SnCI2,
CeCl3/FeCl2/SnCl2 and NdCl3/NaCl/CaCI2. Particular preference is given to
CuCl/KCI/FeCl3, CuCl/KCl/NdCl3, CuCl/KCl/PrCl3 and CuCl/KCl/NdCl3/PrCl3
mixtures. Very particular preference is given to a mixture of CuCl, KCl and
FeCl3.
The salt melts to be used can if appropriate simultaneously also contain a plurality
of components from the group consisting of the metal salts, the salts depressingthe melting point and/or the promoters.
If a promoter also complies with the definition given for the salts depressing the
melting point, in this case the separate addition of a salt depressing the melting
point is not absolutely necessary; the promoter then assumes both functions.
However, it is preferable to employ salt melts which contain at least 3 different
components, where at least one component complies with the definition given for
metal salts, at least one component complies with the definition given for the salts
Le A 30 707-US 21 6 2 6 41
depressing the melting point and at least one component complies with the
definition given for promoters.
If the metal component of the salt melt constituents described can assume a
plurality of oxidation states, for example iron, copper or vanadium, this metal
S component can be used in any oxidation state or in any mixtures of differentoxidation states. While the process according to the invention is being carried out
the oxidation state can change.
The amount of the salts depressing the melting point employed in the process
according to the invention, based on the entire melt, can be between 0 and 99%
by weight, preferably between 10 and 90% by weight and corresponds, very
particularly preferably, roughly to the composition of the eutectic mixture of the
components used.
The concentration of promoters in the salt melt can be, e.g., 0 to 100 mol %,
preferably 0.1 to 50 mol%, and particularly preferably 0.1 to 10 mol%, in each
case based on the entire salt melt.
The metal salts, salts depressing the melting point and, if appropriate, promoters
can be used e.g. directly as salts, e.g. as halides, nitrates, sulphates or
pyrosulphates. Precursors of metal salts can also be used, e.g. metal oxides or
metal hydroxides or elemental metals which are transformed into metal salts whenthe process according to the invention is carried out. Preferably, chlorides areused.
The ratio of hydrogen chloride to oxygen can be varied within wide limits. For
example, the molar ratio of hydrogen chloride to oxygen can vary between 40:1
and 1:2.5. Preferably, this ratio is between 20:1 and 1:125, particularly preferably
between 8:1 and 1:0.5, very particularly preferably between 5:1 and 1:0.3.
The gas containing hydrogen chloride and oxygen is conducted as a continuous
phase into a reaction zone and the salt melt is dispersed therein. Preferably, the
continuous phase and the salt melt are conducted in counter-current to one
another, contact times between 0.1 and 4 seconds are implemented and the
Le A 30 707-US 2 1 6 2 6 4 1
procedure is carried out at 350 to 550C. Suitable reactors for this are e.g. packed
reactors and jet reactors, trickling film columns and spray towers.
The gases coming from the reaction can contain, for example, 40 to 50% by
weight of chlorine, 30 to 40% by weight of hydrogen chloride, 0.5 to 10% by
5 weight of oxygen, 10 to 20% by weight of water (steam) and possibly entrained
inert gases, e.g. nitrogen, and possibly small amounts of organics.
Before the gases coming from the reaction are cooled and hydrogen chloride and
water are separated out therefrom, it is advantageous first to remove entrained
and/or volatilized portions of the salt melt therefrom. For this purpose, this gas
10 can be scrubbed, for example with one or more condensed phases from the overall
process, and the scrubbing liquid can be recycled to the reaction zone.
The reaction gases, if appropriate freed of entrained and/or volatilized salt melt
portions, are preferably rapidly cooled to a temperature below 300C, preferablybelow 200C, and in particular to 120 to 180C. This cooling can be performed,
15 for example, in a spray cooler. Alternatively, or additionally, the reaction gases
can be cooled in an absorption tower filled with previously condensed, aqueous
hydrochloric acid, if appropriate with addition of fresh water, and hydrogen
chloride and water can be condensed together.
The concentration of the resulting aqueous hydrochloric acid can be varied within
20 wide limits, which poses no difficulty to those skilled in the art. It is preferably
aimed to obtain 35 to 37% by weight strength aqueous hydrochloric acid (socalledconcentrated hydrochloric acid). This can then be used for any desired purposes
for which concentrated aqueous hydrochloric acid is known to be used. Before thefurther use, a purification known per se can be carried out, for example by
25 blowing through inert gas (e.g. air) and/or by absorption of impurities (e.g. onto
activated carbon). In this manner, e.g. residual chlorine and/or in the organicspresent can be removed. In this manner, it is possible to obtain, e.g., 5 to 15% by
weight of the hydrogen chloride fed to the process according to the invention aspure, preferably concentrated, aqueous hydrochloric acid.
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The aqueous hydrochloric acid separated off can also be used in another manner.
Thus, for example, concentrated sulphuric acid can be added to the aqueous
hydrochloric acid initially separated off and thus free it of water. The resulting,
preferably unpurified, hydrogen chloride gas can then be recycled to the reaction
5 zone of the process according to the invention. The reaction water in this case
results as more or less dilute sulphuric acid. This can be used in a known manner
or concentrated and thus the reaction water can be obtained as such.
The gas stream remaining after the cooling and separation out of hydrogen
chloride and water essentially contains the chlorine formed in the reaction zone,
10 unreacted oxygen, residual portions of hydrogen chloride and steam, and possibly
inert gases and/or possibly small amounts of organics.
Before chlorine is separated off from this gas stream, residual steam is first
removed. This is achieved by the addition of concentrated sulphuric acid. The
resulting, generally only slightly diluted sulphuric acid can, if appropriate after
15 concentration, be further used at a different point in the process according to the
invention or in another (known) manner, e.g. for the production of fertilizers.
The gas stream freed of residual steam to a very great extent contains, for
example, 60 to 97% by weight of chlorine and is now compressed to 2 to 10 bar.
This compression can be carried out in a single stage or multiple stages.
20 Preferably, two stages are employed. Compression apparatuses which are suitable
are, e.g., piston compressors, rotary compressors and screw compressors. After the
compression the gas mixture is cooled until the chlorine liquefies. Suitable
temperatures are e.g. at a pressure of 10 bar those below 34C, and at a pressure
of 2 bar those below -20C. At other pressures, suitable temperatures can be
25 determined by extrapolation from these values. Chlorine is obtained in this manner
in li~uid form which can be used, if appropriate after further purif1cation, in liquid
form or, after vaporization, like chlorine originating from the electrolysis of
sodium chloride. Preferably, the chlorine is used for chlorinations and
phosgenations of organic compounds. If the chlorine separated off is further used
30 in gaseous form, the cold stored in the chlorine separated off in liquid form can be
utilized for any cooling purposes.
. ~ ~
Le A 30 707-US 21 6 2 6 41
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The gas remaining after the chlorine separation off generally contains essentially
oxygen, and in addition small traces of chlorine and hydrogen chloride, possiblyinert gases and/or possibly small amounts of organics, usually chlorinated
organics. This gas is wholly or partially recycled to the reaction zone of the
5 process according to the invention. It is advantageous, in particular when theprocess according to the invention is carried out for a relatively long time, torecycle only some of this gas and to eject the rest. In this manner accumulation of
inert gas and organics in the reaction system is avoided. Environmentally polluting
constituents, e.g. chlorine, hydrogen chloride and, possibly, organic impurities, in
10 particular chlorinated organic impurities, can be separated from the ejected part of
the gas by absorption and/or adsorption. The absorption can be carried out e.g
using water or aqueous alkalis, and the adsorption can be carried out e.g. usingsilica gel, aluminium oxides and/or activated carbon. Preferably, regenerable
activated carbon is used.
15 The process according to the invention has a number of surprising advantages.Thus, the reaction can be carried out in a continuously uniformly active reaction
zone, a salt melt surface which is constantly being renewed is available for thereaction, a substantial freedom of choice of conditions for the melt and of the gas
streams is available, high conversion rates and high space-time yields may be
20 achieved and only relatively small amounts of salt melt and relatively small
apparatuses are required. It is further advantageous that the reaction can be carried
out without supply of energy from outside, under continuous reaction conditions,without problems with respect to long-term stability of the reactors, with the
reaction water being separated off in the form of a concentrated aqueous
25 hydrochloric acid, with a high concentration of chlorine in the reaction gas and
with the chlorine being separated off by compression and liquefaction without
external solvent.
Le A 30 707-US 21 6 2 6 4 l
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Examples
Example 1
In an apparatus to be operated continuously, a gas mixture comprising 3900 g of
hydrogen chloride, 854 g of oxygen, 211 g of chlorine and 192 g of nitrogen was
reacted per hour in a trickling film reactor at 370C in the presence of a salt melt.
The salt melt comprised 9000 g of the eutectic mixture of potassium chloride andcopper(I) dichloride. For the reaction, the salt melt was pneumatically transported
at intervals by the feedstock gas stream into a storage vessel situated above the
packing bed and continuously metered onto the packing bed. The diameter of the
packing bed was 40 mm. The feedstock gas mixture preheated to 370C was
passed through the packing bed from bottom to top. The hot product gas mixture
leaving the reactor comprised 780 g of hydrogen chloride, 160 g of oxygen,
3245 g of chlorine, 780 g of water and 192 g of nitrogen. It was cooled to 150Cin a spray cooler with 408 g of 34% by weight strength aqueous hydrochloric
acid, and in a downstream absorption tower already filled with 3526 g of 34% by
weight strength aqueous hydrochloric acid the reaction water formed and unreacted
hydrogen chloride were separated off in the form of 34% strength by weight
aqueous hydrochloric acid. In this manner, 397 g of hydrogen chloride, 769 g of
water and 9 g of chlorine were separated off. The remaining reaction gas (per hour
383 g of hydrogen chloride, 160 g of oxygen, 3236 g of chlorine and 192 g of
nitrogen) was dried with concentrated sulphuric acid in a drying tower, then
compressed to 6 bar and cooled to -10C. This resulted in 2308 g of chlorine in
liquid form which additionally contained 91 g of hydrogen chloride in dissolved
form. The non-condensed portions of the gas were conducted into a second
condensation stage operated at -25C, where a further 576 g of chlorine and a
further 41 g of hydrogen chloride in liquid form were separated off
From the non-condensed residual gas, a part-stream comprising 100 g of hydrogen
chloride, 63 g of oxygen, 141 g of chlorine and 75 g of nitrogen was ejected. The
remaining gas stream (per hour 150 g of hydrogen chloride, 94 g of oxygen, 211 gof chlorine and 112 g of nitrogen) was recycled to the reactor.
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21 62641
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Example 2
In continuously operated trickling film reactor, a gas mixture preheated to 480C,
comprising 5967 g of hydrogen chloride, 888 g of oxygen, 248 g of chlorine
124 g of steam and 154 g of nitrogen was reacted per hour at 480C in the
presence of a salt melt as described in Example 1. The hot product gas mixture
leaving the reactor comprised, per hour, 2586 g of hydrogen chloride, 137 g of
oxygen, 3536 g of chlorine, 970 g of water and 154 g of nitrogen. It was cooled
to 150C in a spray cooler using 29% strength by weight aqueous hydrochloric
acid, and in a downstream absorption tower the reaction water formed and
unreacted hydrogen chloride were separated off in the form of 29% strength by
weight hydrochloric acid. The amounts separated off were 334 g of hydrogen
chloride and 830 g of water. The procedure was further carried out as described in
Example 1. A total of 3284 g of liquid chlorine which contained 31 g of hydrogenchloride and 8 g of oxygen resulted. From the non-condensed gas, a part stream
which, per hour, comprised 1 g of hydrogen chloride, 64 g of oxygen, 87 g of
chlorine and 72 g of nitrogen was ejected. The residual gas was recycled to the
reactor.
Example 3
In a continuously operated trickling film reactor, a gas mixture preheated to
480C, comprising 326 g of hydrogen chloride and 71 g of oxygen, was reacted
per hour as described in Example 1 at 480C in the presence of a salt melt. The
salt melt comprised a mixture of 1174 g of potassium chloride, 1001 g of
copper(I) chloride, 2255 g of copper(II) chloride and 600 g of neodymium chloride
hydrate. Per hour, 25 1 of melt were metered through a column (d = 50 mm; h =
70 mm) packed with Raschig rings and were reacted in counter-current with the
feedstock gases The product gas mixture leaving the reactor comprised, per hour,218 g of hydrogen chloride, 47.2 g of oxygen, 104 g of chlorine and 26 5 g of
steam. As described in Example 1, the product gases were cooled to 150C in a
spray cooler using aqueous hydrochloric acid, the reaction water was separated off
in an absorption tower as aqueous hydrochloric acid, the product gases were dried
with concentrated sulphuric acid, and chlorine was taken off in liquid form by
compression to 6 bar and cooling to -10C
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Example 4
In a continuously operated trickling film reactor, a gas mixture preheated to
480C7 comprising 81.5 g of hydrogen chloride and 17.8 g of oxygen, was reacted
per hour as described in Example 1 at 480C in the presence of a salt melt. The
salt melt comprised a mixture of 1174 g of potassium chloride, 1001 g of
copper(I) chloride, 2255 g of copper(II) chloride and 600 g of neodymium chloride
hydrate. Per hour, 25 1 of melt were metered through a column (d = 50 mm; h =
70 mm) packed with Raschig rings and were reacted in counter-current with the
feedstock gases. The product gas mixture leaving the reactor comprised, per hour,
27.3 g of hydrogen chloride, 5.9 g of oxygen, 52.6 g of chlorine and 13.3 g of
steam. As described in Example 1, the product gases were cooled to l50C in a
spray cooler using aqueous hydrochloric acid, the reaction water was separated off
in an absorption tower as aqueous hydrochloric acid, the product gases were dried
with concentrated sulphuric acid, and chlorine was taken off in liquid form by
compression to 6 bar and cooling to -10C.
Example 5
In a continuously operated trickling film reactor, a gas mixture preheated to
480C, comprising 407.5 g of hydrogen chloride and 85.2 g of oxygen, was
reacted per hour as described in Example 1 at 450C in the presence of a salt
melt. The salt melt comprised a mixture of 1174 g of potassium chloride, 1001 g
of copper(I) chloride and 2255 g of copper(II) chloride. Per hour, 20.6 l of melt
were metered through a column (d = 50 mm; h = 70 mm) packed with Raschig
rings and were reacted in counter-current with the feedstock gases. The product
gas mixture leaving the reactor comprised, per hour, 361.7 g of hydrogen chloride,
75.6 g of oxygen, 44.3 g of chlorine and 11.2 g of steam. As described in
Example 1, the product gases were cooled to 1 50C in a spray cooler using
aqueous hydrochloric acid, the reaction water was separated off in an absorptiontower as aqueous hydrochloric acid, the product gases were dried with
concentrated sulphuric acid, and chlorine was taken off in liquid form by
compression to 6 bar and cooling to -10C.
