CA2162643A1 - Process for the oxidation of hydrogen chloride - Google Patents

Process for the oxidation of hydrogen chloride

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Publication number
CA2162643A1
CA2162643A1 CA002162643A CA2162643A CA2162643A1 CA 2162643 A1 CA2162643 A1 CA 2162643A1 CA 002162643 A CA002162643 A CA 002162643A CA 2162643 A CA2162643 A CA 2162643A CA 2162643 A1 CA2162643 A1 CA 2162643A1
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Prior art keywords
fecl3
kcl
cucl
ndcl3
prcl3
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CA002162643A
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French (fr)
Inventor
Helmut Harle
Helmut Waldmann
Hans-Ulrich Dummersdorf
Franz-Rudolf Minz
Fritz Gestermann
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Bayer AG
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Individual
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00Catalysts, in general, characterised by their form or physical properties
    • B01J35/20Catalysts, in general, characterised by their form or physical properties characterised by their non-solid state
    • B01J35/27Catalysts, in general, characterised by their form or physical properties characterised by their non-solid state in a liquid or molten state
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B7/00Halogens; Halogen acids
    • C01B7/01Chlorine; Hydrogen chloride
    • C01B7/03Preparation from chlorides
    • C01B7/04Preparation of chlorine from hydrogen chloride
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/06Halogens; Compounds thereof
    • B01J27/08Halides
    • B01J27/10Chlorides

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Chemistry (AREA)
  • Catalysts (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

Abstract

Hydrogen chloride is particularly advantageously oxidized by oxygen in the presence of a salt melt if the salt melt contains promoters.

Description

Le A 30 635-US/ Gai/ngb/S-P 2 1 6 2 6 ~ 3 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. In the chlorination 10 of hydrocarbons, e.g. of benzene and toluene, large amounts of hydrogen chloride likewise form. Thus in the preparation of chlorobenzene, 0.32 t of hydrogen chloride forms per ton of chlorobenzene.

Various processes are known for disposing of hydrogen chloride. Thus, for example, the resulting hydrogen chloride can be split electrolytically into chlorine 15 and hydrogen after transfer to 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.

20 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 25 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, a mixture must always be separated which still contains hydrogen chloride and oxygen.

30 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 and 2 447 323) or vanadium oxides (see US-A-4 107 280) which are Le A 30 635-US
2162i~43 able to absorb oxygen and hydrogen chloride and, under other experimental conditions, e.g. at relatively high temperature, to eliminate 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 1 st 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 oxide melt 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, delivers only highly dilute, impure chlorine, which at any rate can be used for the preparation of chlorine bleaching liquor (see Chem.Eng. Progr. 44, 657 (1948)).

An improved technique was developed with the so-called "Oppauer-process" (see DE 857 633), in which, for example, a mixture of iron(III) chloride and potassium chloride is used which, as a melt at temperatures of approximately 450C, servesas reaction medium and catalyst. The reactor used is a tower, lined with ceramicmaterial, having a centrally built-in 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 volumes with correspondingly high capital costs and cost-intensive maintenance.

Le A 30 635-US
2~

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.

S 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 from 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-cont~ining catalysts on inert supports, a temperature below 400C likewise being chosen (see EP-A 184 413).

In all of these proposals for solving 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 15 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.

20 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 only possible if a relatively high oxygen excess is employed. However, this requires work-up of the reaction mixture using a solvent, e.g. CC14 or S2Cl2 (see DE-A 1 467 142).

25 The obj ect 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 which is advantageous per se of employing a system of molten salts as catalyst as opposed to the fluidized-bed technique for the Deacon process and avoids the disadvantages of the previous 30 variants, e g,. the two-stage salt melt process or the single-stage Oppauer process.

Le A 30 635-US
2I 626~3 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 by oxygen in the presence of a salt melt, which is characterized in that the salt melt contains 5 promoters.

Salt melts without promoters can be, e.g., mixtures of metal salts and salts depressing the melting point. Metal salts can be both catalytically inactive andcatalytically active salts for the oxidation of hydrogen chloride by oxygen. In each case, the addition according to the invention of a promoter effects an increase in 10 the reaction rate and the space-time yield.

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 Elements. Preference is given to salts of aluminium, lanthanum, titanium, zirconium, vanadium, niobium, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, copper and zinc. Particular 15 preference is given to salts of vanadium, chromium, manganese, iron, cobalt, nickel, copper and zinc. Very particular preference is given to copper salts.

Salts depressin~, the melting point can be, e.g., salts of metals of main groups and 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, 20 calcium, strontium, barium, aluminium, gallium, indium, thallium, germanium, tin, antimony, bismuth, lead, zinc and silver. Preference is given to salts of lithium, sodium, potassium, aluminium and zinc. Particular preference is given to salts of potassium Salt melts without promoters are, e.g., mixtures of the following type:
25 LiCI/KCI, ZnCI2/KCI, KCI/NaCI/LiCI, MgCI2/KCI, AICI3/KCI, AlCI3/NaCl, V20s/K2SO4/K2S207, CrCI3/NaCI/KCI, MnCI2/NaCI, MnCI2/KCI, MnCI2/KCI/NaCI, MnCI2/AlCI3, MnCI2/GaCI3, MnCI2/SnCI2, MnCI2/PbCI2, MnCI2/ZnCI2, FeCI3/LiCI, FeCI3/NaCI, FeCl3/KCI, FeCI3/CsCI, FeCI3/KCI, FeCI3/AlCI3, FeCI3/GaCI3, FeCI3/SnCI4, FeCI3/PbCI2, FeCI3/BiCI3, FeCI3/TiCI4, FeCI3/MoCls, FeCI3/ZnCI2, FeCl3/NaCI/ZrCI4, FeCI3/KCI/ZrCl4, Le A 30 635-US 2 16 2 6 9 3 FeC13/NaCl/WC 14, CoC12/NaCI, CoC12/KCI, CoC12/GaC13, CoC12/SllCl2, CoCl2/PbCl2, CoCI2/ZnCl2, CuCl/NaCI, CuCI/KCI, CuCI/RbCI, CuCI/CsCl, CuCI/AlC13, CuCI/GaCI3, CuCl/InCl3, CuCl/TlCI, CuCl/SnCl2, CuCI/PbCl2, CuCl/BiCI3, CuCl/FeCl3, CuCl/AgCI, CuCl/ZnCl2, LaCl3/FeCl2/SnCI2, NaCI/SnCI2, FeCI2/SnCI2 and NaCI/CaCl2. Preference is given to mixtures of the type V2O5/K2SO4/K2S2O7, CrCl3/NaCl/KCl, MnCI2/KCl, FeCl3/KCI and CuCI/KCI. Particular preference is given to mixtures of the type V2Os/K2SO4/K2S2O7, FeCl3/KCI and CuCl/KCl. Very particular preference is given to a mixture of KCl and CuCl.

If metal oxides, e.g. V2O5, are used, these convert into salts when the process according to the invention is carried out.

The promoters to be added according to the invention 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 the rare earths, for instance salts of scandium, yttrium, lanthanum, lS titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, rhenium, iron, ruthenium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold and salts of the rareearths, 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 to be used according to the invention are, e.g mixtures of the following type:
LiCI/KCI/FeCI3, LiCI/KCI/NdCl3/PrCl3, KCl/NaCl/LiCl/FeCI3 KCI/NaCI/LiCI/NdCl3/PrCl3, MgCl2/KCl/FeCl3, MgCl2/KCI/NdCl3/PrCl MgCI2/KCI/LaCI3, MgCI2/KCI/CeCI3, AlCI3/KCI/FeCI3, AlCI3/KCI/NdCI
AlCI3/KCI/PrCI3, AlCI3/KCl/NdCI3/PrCI3, AlCI3/KCI/LaCl3, AlCl3/KCI/CeCI
AlCI3/NaCI/FeCI3, AlCl3/NaCllNdCI3, AlCI3/NaCI/PrCI3, AlCI3/NaCI/NdCl3/PrCl LeA30635-US 216264~

AlCI3/NaCI/LaC13, AlCI3/NaCl/cecl3, V25/K2S4/K2S27/FeC13 V~s/K~S4/K2S27/CUCI, V2o5lK2so4lK2s2o7lL
V205/K2SO4/K2S207/CeCl3, V2o5lK2so4lK2s2o7lNdcl3 V205/K2SO4/K2S207/NdCI3/PrCI3, CrCI3/NaCI/KCI/FeCI3, MnCI2/KCI/FeCI3, MnCI2/KCI/LaCI3, MnCI2/KCI/CeCI3, MnCI2/KCI/NdCI3/PrCI3, MnCI2/AlCI3/FeCI3, MnCI2/KCI/NaCI/FeCI3, MnCI2/SnCI2/FeCI3, MnCI2/SnCI2/LaCI3, MnCI2/SnCI2/CeCI3, MnCI2/SnCI2/NdCI3, MnCI2/SnCI2/PrCI3, MnCI2/SnCI2/NdCI3/PrCI3, FeCI3/KCI/NdCl3/PrCl3, FeCI3/LiCI/CuCI, FeCI3/NaCI/CuCI, FeCI3/KCI/CuCI, FeCI3/ZnCI2/CuCI, FeCI3/NaCI/ZrCI4, CoCI2/SnCl2/FeCI3, CuCI/KCI/FeCI3, CuCI/AlCI3/FeCI3, CuCI/BiCI3/FeCI3, CuCI/CsCI/FeCI3, CuCI/FeCI3, CuCI/SnCI2/FeCI3, CuCI/ZnCI2/FeCI3, CuCI/TlCI/FeCI3, CuCI/KCI/NdCI3, CuCI/KCI/PrCI3, CuCI/KCI/LaCI3, CuCI/KCI/CeCI3, CuCI/KC 1 /NdCI3/PrCI3, ZnCI2/KCI/FeCI3, ZnCI2/KCI/NdCI3/PrCl3. Preference is given to mixtures of the type:
V~O5/K2SO4/K2S2O7/FeCI3, FeCI3/KCI/NdCI3/PrCI3, CuCI/KCI/FeCI3, CuCI/AlCI3/FeCI3, CuCI/BiCI3/FeCI3, CuCI/CsCI/FeCI3, CuCI/FeCI3, CuCI/SnCI2/FeCI3, CuCI/ZnCI2/FeCI3, CuCI/KCI/NdCI3, CuCI/KCI/PrCI3, CuCI/KCI/LaCI3, CuCI/KCI/CeCI3, CuCI/KCI/NdCI3/PrCI3, CeCl3/NaCI/SnCI2, CeCI3/FeCI2/SnCI2 and NdCI3/NaCI/CaCI2. Particular preference is given to CuCI/KCI/FeCI3, CuCI/KCI/NdCI3, CuCI/KCI/PrCI3 and CuCI/KCI/NdCI3/PrCI3 mixtures. Very particular preference is given to a mixture of CuCI, KCI and Fecl3.

The salt melts containing promoters and to be used according to the invention can if appropriate also simultaneously contain a plurality of components from the group consisting of the metal salts, the salts depressing the 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 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, at least one component complying with the definition given for metal salts, at least one component complying with the definition given for salts depressing the Le A 30 635-US

melting point and at least one component complying with the definition given forpromoters.

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 5 component can be used in any oxidation state or in any mixtures of different oxidation 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%
10 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 promoters need not be completely dissolved in the salt melt during the reaction, but this is preferred. Their concentration in the salt melt can be, e.g. 0.01 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 promoters to be used according to the invention 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 transform into metal salts when the process according to the invention is carried out. Preferably, chlorides are used.

The reaction temperature required to achieve a high yield essentially depends onthe activity of the salt melt containing the promoters used. It is generally between room temperature and 1000C. Preferably, temperatures between 300C and 600C
are employed, particularly preferably those between 350C and 550C.

The pressure for carrying out the process according to the invention can be, e.g., between 0.1 and 50 bar. Preferably, pressures between 0.5 and 10 bar are employed, particularly preferably those between 1 and 3 bar.

Le A 30 635-US

The oxidation according to the invention of hydrogen chloride succeeds in principle using any oxygen-containing gases. Preferably, however, gases are employed which have an oxygen content of more than 90% by volume of oxygen.

The ratio of hydrogen chloride to oxygen can be varied in broad ranges. For 5 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 1:1.25, particularly preferably between 8:1 and 1:0.5, very particularly preferably between 5:1 and 1:0.3.

The process according to the invention is advantageously carried out in such a way that the feedstocks are conducted into a reaction zone as a continuous phase10 and the salt melt containing promoters is dispersed in the continuous phase.

The term feedstocks is to be taken to mean the gas mixture of hydrogen chloride and oxygen to be brought to reaction, which mixture can possibly contain inert gas portions, e.g. nitrogen, carbon dioxide, argon and/or helium or impurities, e.g.carbon monoxide.

15 In the reaction zone, with advancing reaction, a continuous conversion of the feedstocks to the products takes place in accordance with the equation 4 HCI + 2 ~ 2 Cl2 + 2 H2O.

The product mixture contains chlorine, steam, possibly inert gas portions and can contain impurities and unreacted feedstocks. With suitable reaction conditions, by 20 using the process according to the invention the thermodynamic equilibrium can be set, i.e. the maximum possible chlorine yield can be achieved.

It is advantageous to run the process according to the invention in such a way that the contact times between the continuous phase and the disperse phase are between 0.001 and 500 seconds, preferably between 0.01 and 50 seconds, 25 particularly preferably between 0.1 and 4 seconds.

Preferably, the continuous phase of the feedstocks and the salt melt containing promoters are run in counter-current.

Le A 30 635-US 2162643 Reaction apparatuses which are suitable for carrying out the process according to the invention industrially are, e.g., trickling film reactors, packed reactors, spray tower reactors and bubble column reactors.

Preference is given to trickling film reactors. The process according to the 5 invention can be carried out continuously, discontinuously or in cycles.

The process according to the invention permits the oxidation of hydrogen chloride by oxygen or an oxygen-containing gas in the presence of a salt melt with higherconversion rates than according to the prior art. Furthermore, the reaction succeeds with higher space-time yields and in a simpler manner than according to the prior 1 0 art.

The process according to the invention further has the advantage that the addition of promoters increases the reaction rate and by this means conversion rate and space-time yield are markedly improved. Consequently, smaller reactors can be used and the capital costs can be decreased. The smaller volume of the salt melt to 15 be handled decreases the energy losses which occur, e.g. during the heat-up process. In addition, the start-up and shut-down processes are shortened.

The superiority of the process according to the invention with respect to the prior art is illustrated by the following examples.

Le A 30 635-US

~o Examples Example 1 In a 1 I glass reactor which, for relatively small batches, acts as a model for reactors to be used industrially, a mixture of 318.6 g (4.27 mol) of potassium S chloride, 423.0 g (4.27 mol) of copper(I) chloride, 158.1 g (0.44 mol) of neodymium chloride hexahydrate and 68.5 g (0.19 mol) of praseodymium chloride hexahydrate (molar ratio: 1: 1 :0.1 :0.045) was introduced as initial charge andheated to a temperature of 450C. The mixture melted at about 150C and became a virtually black, easily stirrable melt which occupied a volume of 415 ml. 48 I/h of hydrogen chloride and 12.61/h of oxygen (technical grade quality) were introduced continuously with stirring through a glass frit. After equilibrium was established, the chlorine yield was determined by introducing the product gas stream into a potassium iodide solution and iodometric determination with thiosulphate. The chlorine yield achieved can be seen in Table 1.

Exam ple 2 In a I I glass reactor a mixture of 289.3 g (3.88 mol) of potassium chloride, 768.2 g (7.76 mol) of copper(I) chloride and 21.0g (0.078 mol) of iron(III) chloride hexahydrate was introduced as initial charge and heated to a temperature of 450C. This gave a melt having a volume of 415 ml. The procedure was then followed as in Example 1. The chlorine yield achieved can be seen in Table 1.

Example 3 (for comparison) In a 1 I glass reactor, a eutectic mixture of 289.3 g (3.88 mol) of potassium chloride and 768.2 g (7.76 mol) of copper(I) chloride was introduced as initial charge and heated to a temperature of 450C. This gave a melt having a volume of 415 ml. The procedure was then followed as in Example 1. The chlorine yield achieved can be seen in Table 1.

Le A 30 635-US 21 6 2 6 4 3 T~ble I

Example Chlorine yield (% of theory) 3 (comparison) 23 4 Ex~mples 4-8 In a I I glass reactor, a eutectic mixture of 289.3 g (3 88 mol) of potassium chloride and 768.2 g (7.76 mol) of copper(I) chloride was introduced as initial charge and heated to a temperature of 450C. This gave a melt having a volume 10 of 415 ml. Neodymium chloride hexahydrate (see Table 2 for the amounts) was then added and the procedure was followed as in Example 1 The chlorine yields achieved after equilibrium had been established can be seen from Table 2.

T~ble 2 ExampleNeodymium chlorideReaction temperature Chlorine yield (mol% with respect to (C) copper) (% of theory) 4 1 480 45.4 1 420 19.1 6 2 450 41.1 7 4 480 57.1 8 8 450 62.3 Le A 30 635-US 2 I 6 2 6 4 3 Examples 9-16 In a 1 l glass reactor, a eutectic mixture of 289 3 g (3.88 mol) of potassium chloride and 768.2 g (7.76 mol) of copper(I) chloride was placed as initial charge and heated to a temperature of 450C. This gave a melt having a volume of 415 5 ml. Iron chloride trihydrate (see Table 3 for amounts) was then added and the procedure was followed as in Example 1. The chlorine yields achieved after equilibrium had been established can be seen in Table 3.

Table 3 Example Iron chloride Reaction temperature Chlorine yield (mol% with respect (C) to copper) (% of theory) 9 0.25 450 30 0 0 5 450 32.2 I l 1 420 21.7 16 450 42.5 for comparison Example 17 20 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 at 480C in the presence of a salt melt, comprising 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 l of melt were transported Le A 30 635-US

at intervals pneumatically by the feedstock gas stream to a storage vessel situated above the packed bed, continuously added to a column (d = 50 mm; h = 270 mm) packed with Raschig rings and brought into contact with the feedstock gases in counter-current. 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.

Example 18 In a continuously operated trickling film reactor a gas mixture preheated to 480C, comprising 81.5 g of hydrogen chloride and 17.8 g of oxygen, was reacted per hour at 480C in the presence of a salt melt comprising 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 transportedat intervals pneumatically by the feedstock gas stream to a storage vessel situated above the packed bed, continuously added to a column (d = 50 mm; h = 270 mm) packed with Raschig rings and brought into contact with the feedstock gases in counter-current. 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.

Ex~ml)le 19 (for comparison) 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 at 450C in the presence of a salt melt, comprising 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 1 of melt were transported at intervals pneumatically by the feedstock gas stream to a storage vessel situated above the packed bed, continuously added to a column (d = 50 mm; h = 270 mm) packed with Raschig rings and brought into contact with the feedstock gases in counter-current. The product gas mixture leaving the reactor comprised, per hour, 361.7 g of hydrogenchloride, 75.6 g of oxygen, 44.3 g of chlorine and 11.25 g of steam.

Claims (10)

1. A process for the oxidation of hydrogen chloride with oxygen in the presence of a salt melt which contains a promoter.
2. A process according to claim 1, in which the salt melt, in addition to the promoter, comprises a mixture of a metal salt and a salt to depress the melting point.
3. A process according to claim 1, in which the salt melt, in addition to the promoter, comprises a mixture of a metal salt and a salt to depress the melting point and the metal salt is a salt of a metal of main groups I to V or sub-groups I to VIII of the Periodic Table of the Elements or a mixture thereof.
4. A process according to claim 1, in which the salt melt, in addition to the promoter, comprises a mixture of a metal salt and a salt to depress the melting point and the salt to depress the melting point is a salt of a metal of main groups or subgroups I to III or main groups IV to V of the Periodic Table of the Elements or a mixture of such metal salts.
5. A process according to claim 1, in which the promoter is a metal salt of subgroups I to VIII of the Periodic Table of the Elements or rare earths or mixtures thereof.
6. A process according to claim 1, in which the salt melt is selected from:
LiCl/KCl/FeCl3, LiCl/KCl/NdCl3/PrCl3, KCl/NaCl/LiCl/FeCl3, KCl/NaCl/LiCl/NdCl3/PrCl3, MgCl2/KCl/FeCl3, MgCl2/KCl/NdCl3/PrCl3, MgCl,/KCl/LaCl3, MgCl2/KCl/CeCl3, AlCl3/KCl/FeCl3, AlCl3/KCl/NdCl3, AlCl3/KCl/PrCl3, AlCl3/KCl/NdCl3/PrCl3, AlCl3/KCl/LaCl3, AlCl3/KCl/CeCl3, AlCl3/NaCl/FeCl3, AlCl3/NaCl/NdCl3, AlCl3/NaCl/PrCl3, AlCl3/NaCl/NdCl3/PrCl3, AlCl3/NaCl/LaCl3, AlCl3/NaCl/CeCl3, V2O5/K2SO4/K2S2O7/FeCl3, V2O5/K2SO4/K2S2O7/CUCl, V2O5/K2SO4/K2S2O7/LaCl3, V2O5/K2SO4/K2S2O7/CeCl3, V2O5/K2SO4/K2S2O7/NdCl3, V2O5/K2SO4/K7S2O7/NdCl3/PrCl3, CrCl3/NaCl/KCl/FeCl3, MnCl2/KCl/FeCl3, MnCl2/KCl/LaCl3, MnCl2/KCl/CeCl3, MnCl2/KCl/NdCl3/PrCl3, MnCl2/AlCl3/FeCl3, MnCl2/KCl/NaCl/FeCl3, MnCl2/SnCl2/FeCl3, MnCl2/SnCl2/LaCl3, MnCl2/SnCl2/CeCl3, MnCl2/SnCl2/NdCl3, MnCl2/SnCl2/PrCl3, MnCl2/SnCl2/NdCl3/PrCl3, FeCl3/KCl/NdCl3/PrCl3, FeCl3/LiCl/CuCl, FeCl3/NaCl/CuCl, FeCl3/KCl/CuCl, FeCl3/ZnCl2/CuCl, FeCl3/NaCl/ZrCl4, CoCl2/SnCl2/FeCl3, CuCl/KCl/FeCl3, CuCl/AlCl3/FeCl3, CuCl/BiCl3/FeCl3, CuCl/CsCl/FeCl3, CuCl/FeCl3, CuCl/SnCl2/FeCl3, CuCl/ZnCl2/FeCl3, CuCl/TlCl/FeCl3, CuCl/KCl/NdCl3, CuCl/KCl/PrCl3, CuCl/KCl/LaCl3, CuCl/KCl/CeCl3, CuCl/KCl/NdCl3/PrCi3, ZnCl2/KCl/FeCl3, ZnCl2/KCl/NdCl3/PrCl3, V2O5/K2SO4/K2S2O7/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, CuClKCl/NdCl3/PrCl3, CeCl3/NaCl/SnCl2, CeCl3/FeCl2/SnCl2 and NdCl3/NaCl/CaCl2.
7. A process according to claim 1, in which the salt melt contains a salt to depress the melting point in an amount of 0 to 99% by weight, based on the total melt, and a promoter in a concentration of 0.01 to 100 mol%, based on the total salt amount.
8. A process according to claim 1, in which the salts in the salt melt are halides, nitrates, sulphates or pyrosulphates or are precursors of metal salts in the form of metal oxides, metal hydroxides or elemental metals.
9. A process according to claim 1, which is effected at a temperature between room temperature and 1,000°C.
10. A process according to claim 1, in which the molar ratio of hydrogen chloride to oxygen in the starting mixture is between 40:1 and 1:2.5.
CA002162643A 1994-11-14 1995-11-10 Process for the oxidation of hydrogen chloride Abandoned CA2162643A1 (en)

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