SA97170635B1 - An improved method for the electrolysis of aqueous solutions of hydrochloric acid. - Google Patents

Abstract

Abstract: The present invention relates to an improved method for producing chlorine from aqueous solutions of hydrochloric acid in a membrane cell for electrolysis each with a cathode compartment equipped with a gaseous diffusion cathode supplied with air or supplied air or oxygen, and an anodic compartment equipped with an anode equipped with a catalytic cap Electrolyte to generate chlorine. The aforementioned anode chamber is fed with an aqueous solution of hydrochloric acid with a maximum concentration of 20% and a maximum temperature of 60°C, containing an oxidizing compound with an oxidation-reduction potential of at least zero Volts NHE (usual hydrogen electrode) as Preferred from 0.3-0.6 V NHE. The suitable oxidizing compound is trivalent in concentrations included in the range 100 to 10,000 parts per million. The anodic and cathodic chambers of the cell and its internal components are made of titanium or alloys thereof, such as 0.2 titanium-palladium, and the parts made of titanium in which there are cracks are provided with a protective covering based on metals of the platinum group, and their oxides like them or Like a mixture of them.

Description

An improved method for the electrolysis of aqueous solutions of hydrochloric acid Full Description Background The present invention relates to Sua chlorine Modern industrial chemistry relies to a large extent on the use of chlorine as a raw material. Reactions of practical interest can be divided into two groups depending on whether the final product contains chlorine or not; According to the following product: A - finished offal containing chlorine. Al - production of polyvinylchloride (PVC) from the polymerization of vinyl chloride monomer (VCM) and obtaining unpolymerized vinyl chloride (VEM) through two steps of dichloroethane synthesis dichloroethane (DCE) from ethylene-6 and chlorine; And from the thermal cracking of dichloroethane 06 to vinyl Jail chloride | 0 by the following reactions: CH, =CH, +Cl, -----> CH, CI-CH, Cl (DCE) CH, Cl-CH, Cl -----> CHCI=CH; (VCM) +110 is also converted to 48 hydrochloric acid which is a by-product of the reaction and represents 7,500 percent of the chlorine used; to additional DCE by the following reaction of process 1 _ chlorination in the presence of oxygen: CH, = CH, + 2101+ ' / 03 > CHCl - CHCl + 10 Ae

Conversely creamy in other industrial processes; Hydrochloric acid cannot be recycled, as it is exposed to a commercial problem in a low-price market in general; Also, due to its content of organic impurities containing chlorine; Three similar processes are listed here: 0 20 C - production of chlorobenzene (monochlorobenzene) + HCI 11:01 < Mann + Cs Hs Cs Hg + 7 <> 11012 (dichlorobenzene) + 21101 A3 - Production of chloromethanes (lise CH, + Cl, > 1:0 (methylchloride) + HCl CH, C1, (methylenechloride) + 111 ve > M20 + CH, and OF can be Chloromethane, chloromethanes, starting materials for the reaction to produce fluorinated compounds 40 in exchange with hydrofluoric acid, as follows: HF < CHF + HCI + ion B is the final product that does not contain chlorine. polyurethane ¢ and the starting materials for the reaction are cad isocyanates isocyanates, which were obtained through two steps as follows: CO + Cl; -< 00012 (phosgene) COCl, + R-NH, (amine) - ---> RNCO (isocyanate) + 21101 Atl

p

While hydrochloric acid is contained in the chlorination process at point A

On Lov of chlorine used; For the production of isocyanates, all chlorine is removed from the

Picture of hydrochloric acid 40, hydrochloric as a by-product 0 and the same applies to produce

Polycarbonates, and there are similar properties in the production of titanium dioxide: d, ditanium dioxide, and chlorine is used to obtain titanium tetrachloride.

06 which then turns into titanium dioxide with aes

Hydrochloric acid as a by-product.

While generating industrial chemistry, Lf will go along with establishing new industrial units or expanding others

present for the production of fluorine isocyanates as well as certain chlorinated compounds;

1, it can easily be predicted that a large increase in the quantities of hydrochloric acid will be available

While market requirements are very weak; In this situation, the process capable of converting acid appears

Hydrochloric acid chlorine is very useful.

The technological background regarding hydrochloric acid conversion can be summarized. acid

to chlorine as follows:

1- Stimulation processes

These processes derive from the well-known Deacon process; Invented at the end of the ninth century

Ten. It is based on the oxidation reaction of gaseous hydrochloric acid

Catalyst 1 metal (copper chloride)

Cl; + 0 JH Ymoila + HCl Tim

This - and recently, the process has been significantly improved by matching the catalyst containing chromium oxide and operating at a low temperature. The problem affecting this process lies in the thermodynamics of the reaction; Which allows only partial conversion of hydrochloric acid, and therefore the direction of the current for the reaction must take into account both the separation of chlorine from the hydrochloric acid and the re-cycling of the hydrochloric acid. add to that ; The water crack is removed in the industrial unit (the water is a reaction product) and contains ALE minerals produced from the catalyst. And to overcome these negatives; newly ; Z oxidation is proposed to be performed in two steps; They are: a reaction between gaseous hydrochloric acid and copper oxide to form copper chloride; Sequentially, a reaction between copper chloride and oxygen to form chlorine and oxide 0 copper, which is a new material for the first reaction (chemical engineering test - 11 September 1380), while this new process contains the need to support the properties of new catalysts capable of withstanding thermal shock and friction. Electrochemical processes Hydrochloric acid is analyzed in the form of an aqueous solution electrolytically in an electrochemical cell 1 divided into two chambers by a porous barrier or by an ion exchange membrane, Perfluorinated type.The following reactions occur at the polarity: positive (anode) and negative (cathode) Cl ja Cl-2¢ + H++2 > H d 0 - Total reaction Cly+H, H HCl chem

- the process is applied to a certain number of industrial units; This process includes in a modified version as close as possible to typical; Energy consumption, Vow ny, is kilowatt-hours per ton of chlorine at a current density of 5000 amperes per square metre. This energy consumption is usually considered too high to be economically beneficial and also due to the high investment costs in fact 1; The high sharpness of both hydrochloric acid and chlorine solutions leads to the selection of black lead as a construction material. which imposes a high GSS of the mechanical mechanism. moreover; The high embrittlement of black lead constitutes reliability problems for the industrial unit, and in particular; The process under pressure is excluded, which can provide clear advantages in terms of product quality and the integration of the electrolytic decomposition process into the industrial production units. Today, black lead can be replaced by black lead compounds, which are obtained by hot pressing of black lead powders and thermoplastic and chemically resistant adhesives 0 as described in US Patent 4,911,557. These compounds require special molds and very strong pressures, and in addition to that, the weight has 1 advantages in terms of high resistance and its ability to be formed from pure black lead. It is proposed to replace the hydrogen-emitting cathode with an oxygen-consuming cathode. This provides the advantage of a lower voltage cell; Accordingly, reducing the electrical energy consumed to 1101 - 0001 kilowatt-hour per ton of chlorine - and finally this reduced consumption works on GUE electrolysis processes. And while this system has been tested on a laboratory level; The application has not been registered at the industrial level. Recently, other suggestions have been made: ‎. PCT publication no. 10/095/44797 of Du Pont De Nemours and Co

Ae

In fact, the electrolysis of gaseous hydrochloric acid obtained from industrial units for the production of isocyanates, fluorinated compounds, or chlorides has been described; After appropriate filtration to remove organic and solid particles, ills can be present. Hydrochloric acid supplies an electrolysis cell divided into 2 chambers by a Perfluorinated ion exchange membrane. The anode chamber comprises a gas diffusion electrode made of a porous thin film containing a catalyst suitable for close contact with the membrane. Gaseous hydrochloric acid diffuses through the electrode holes to the interface between the membrane and the catalyst, where it is converted to chlorine. The cathode chamber is provided with a Lad electrode in close contact with the membrane capable of generating hydrogen 0 . The water stream removes the released hydrogen in the form of bubbles and contributes to the regulation of cell temperature, however, under certain operating conditions, in particular during the off and on operation of the anode chamber; Lay the appearance of Sle, which contains 40 hydrochloric acid at Ale concentrations of 40 - 70 7 . Then this process also needs materials with high resistance and only black lead seems to be suitable and thus involves high investment costs as discussed from hve The general description of the invention 2 The purpose of the present invention is to overcome the defects of the previous field; In particular, it reveals a new process for the electrolysis of aqueous solutions of hydrochloric acid 80 with a cell that includes the use of a gaseous diffusion cathode supplied with oxygen and is characterized by high mechanical reliability and reduced investment costs. It was completed

Mother -

The present invention relates to a method for the electrolysis of Agile solutions of hydrochloric acid, where the aqueous solution of hydrochloric acid is provided with an anode chamber of an electrochemical cell containing an anode made of a material resistant to a specific enzyme that is resistant to rust, and equipped with an electrocatalytic cover for the emission of chlorine. The enzyme-resistant materials are porous flakes of graphitized carbon; According to Jara article (G8) PWB - 3 201166 or TGH Toray porous; Grids or expanded metals made of titanium, titanium alloys, ctitanium, niobium, or tantalum. The electrocatalytic cover can be made of oxides of these Jie platinum group metals, or in 0 mixtures; Optional addition of oxides, chemical stability, Fa, titanium or tantalum oxides; The cathode is separated from the anode compartment by an ion exchange membrane pre-saturated with fluorine 0 of the ion type.

positive charge. Suitable films are commercially marketed by Du Pont under the registered mark 0 (in particular Nafion 11; Nafion 111 films). Similar 0 products may also be used and commercially available by Asahi Glass and Asahi Chemical. In Japan, the cathode chamber includes “a gaseous diffusion cathode equipped with air, oxygenated air, or pure oxygen; the gaseous diffusion cathode is made of porous enzyme-resistant raw material that includes at least in one form a porous electrocatalytic cover. The cathode is made waterproof For example, Jt immersed polytetrathylene molecules in the catalyst layer and optionally also in © all the porous enzyme-resistant material in order to facilitate the release of the water formed by the reaction between

Tim

F - Oxygen and protons leaving through the membrane from the anode chamber. The material for enzymes is generally made of porous film or TGH carbon graphite fabric.

Sia graphitized carbon ‎Toray or BWB - 3 ZoltecThe electrocatalytic layer includes as a catalyst metals from the platinum group or an oxide from that source either per se or in a mixture. Taking into account the selection of the optimal installation; The need. And the need at the same time to take the preferred kinetics for the reaction of oxygen and good resistance to all acidic conditions prevailing inside the electrocatalytic jacket as a result of the diffusion of hydrochloric acid through the membrane from the anode chamber and also the high tolerance type of oxygen gas. Suitable catalysts are platinum ¢ iridium; ruthenium oxide and selenium per se; Or possibly supported on 0 carbon powder with high surface area Jie Lakan-72-XC gas diffusion cathode can be provided with a thin layer of ionic polymer material on the facing side of the membrane. Preferably, the Lig copolymer has a similar composition to that of the ion exchange membrane. The gas diffusion cathode is kept in close contact with the membrane under its heat; pressure regulator; for an appropriate time. prior to placement in the cell. preferably due to lower costs; The cathode and the membrane are installed inside the cell as single pieces and kept in contact with an appropriate differential pressure between the anode and cathode chambers (the pressure of the anode chamber is higher than the pressure of the cathode chamber). It was found that satisfactory results were obtained with a differential pressure of 1 - 1.1 bar; with lower values; Substitution efficiencies are essentially where lel values are used even if they have slight advantages. However differential pressure is useful. Loveie Lad© previously presses the cathode into the membrane; And as it was known in the choice; Tim can happen

- 1. separations between the cathode and the membrane with time as a result of the capillary pressure formed inside the bore with water produced by the reaction of oxygen; In this case, the differential pressure ensures an appropriate close contact between the separation zones. Differential pressure can only be applied when Load is supplied to the cathode; and the membrane. Cathode chamber with rigid construction suitable for orderly support of the cathode-membrane assembly

0 to make such a composition for example from a porous foil of suitable thickness and well leveled 0 and in a preferred embodiment of the present invention; The porous sheet shall be made of a first layer made of expanded metal mesh or sheet with a large mesh size and necessary thickness in order to provide the necessary rigidity. a second layer made of expanded metal mesh or sheet having less thickness and mesh size than the first layer; suitable to be provided with a large number of contact points with the gas diffusion electrode; In this way it can be solved more easily

0 and cheaper to the problem of varying requirements than the cathodic composition being solid which means basic thickness and a large number of contact points which means small holes or mesh size; Easy access to oxygen and rapid removal of water formed by the reaction of oxygen, whose targets can only be obtained with small fish. The anode and cathode chambers of the electrochemical cell are bounded on one side by an ion exchange membrane and on the other

1 The other side with an electrically conductive wall with appropriate chemical resistance. This characteristic is clear for the anode chamber that is supplied with hydrochloric acid, but Lind is necessary for the cathode chamber. And in fact; It has been observed that by means of the aforementioned fluorine membranes, the water formed by the interaction of oxygen is that; The caustic liquid appearance on the base of the cathode chamber contains hydrochloric acid in amounts ranging from © to LY

0 .by weight.

A

11- Now the invention will be described by reference to Figure 1, which is a simplified longitudinal cross-section of the electrochemical cell of the invention; The cell includes an ion exchange membrane 1 ; Two YoY cathode and anode compartments in series; anode ; acid feed nozzle 0; Nozzle + for drawing spent acid and resulting chlorine; wall 17 defines the anode compartment; gas diffusion cathode 4; Cathode supporting element 4 comprising a thick metal expanded mesh plate 01 and a plate 0 fine expanded metal mesh 11 ; Nozzle 11 for supplying air, oxygenated air, or pure oxygen; Nozzle 117 to withdraw acidic water for the reaction of oxygen; excess oxygen; wall bounding cathode compartment VE; Vo 26 sealing end gaskets in industrial practice; The electrochemical cells are like the one plotted in Fig. 1; Usually 0 grouped into a certain number Lad for layout planning; The so-called 'filter press' arranges to form an electrolyte; Which is the electrochemical equivalent of a chemical reactor. in the electrolyzer; The various cells are electrically connected either in parallel; or in a string. In a parallel arrangement, the cathode of each cell is connected to a connecting rod in electrical contact with the negative pole of the rectifier; While each anode is also connected to the conduction arm in electrical contact with the positive pole of the rectifier. and conversely in order in 0s series; The anode of each cell connects to the cathode of the next cell without the need for electrical conductors, as in the parallel arrangement; This electrical connection can be made by resorting to suitable conductors which provide the necessary electrical continuity between the anode of one cell or the cathode of an adjacent cell. And when the anode and cathode materials are one; The connection can be made simply by using a single wall LGE function to locate both the anode of one cell and the cathode compartment of the adjacent cell; © Especially since it is a simplified structural solution used in electrolyzers using T-current technology

- 11 “when mentioned. hydrochloric acid For hydrochloric acid dla for electrolysis of solutions Technology, in fact, black lead is used as a structural material only for both the anode compartments and the cathode compartments. While this material is very expensive as a result of the difficult and consuming mechanism. for the time; In addition to the scarcity of dependence on it as a result of its self-destruction

And as already said; Pure black lead can be replaced by compounds made of black ala ll and polymers ¢, especially fluorinated polymers; which are less brittle, but also more expensive than pure black lead; Do not use another substance in the previous field. For special interest, titanium, which has an acceptable cost, can be used. It can be produced in thin sheets that are easy to manufacture and form, and are also resistant

0 for aqueous solutions of chlorine containing hydrochloric acid, which is the typical anode conditions during operation. While titanium attacks easily in the absence of chlorine and electric current; A situation identical to the initial form of starting work, and all these cases Cun violate the rule; There is a sudden power outage; Furthermore ; In the previous technological field » Electrolysis is carried out without gas diffusion cathodes supplied with air or oxygen, and then it is

1 - The cathodic reaction is the generation of hydrogen in the presence of hydrogen titanium; And when it is used as a material for the cathode chamber, it causes embrittlement. Surprisingly, it was found that by introducing modifications to the electrolysis process of the previous field, it is possible to use titanium and alloys from that source; such as fluorinated titanium - palladium +.Y) polymers 7); While the mounting material for both the anodic and cathodic compartments; Then supply

© _ With a simple and cheap installation of the electrolyzer completely made of metal.

Tim

EN

The modifications included in the present invention are listed here as follows: - Adding an oxidizing compound to the aqueous solution of hydrochloric acid, and the said compound must always be kept in the state of chlorine oxidation, and it must not be reduced predominantly when it comes into contact with a gas diffusion cathode. These requirements meet when the oxidation potential 0 and reduction is higher than the discharge of hydrogen; Gas diffusion can occur at the electrode in cases of strong irregularity. This reduces the value of the voltage in the acidic liquid present in the gas diffusion cathode vaults and is ia volt for the NHE field (Normal Hydrogen Electrode). NHE: In an identical manner, trivalent iron and 0-bivalent copper can be added to the acid, while the invention does not intend to be limited either. through the membrane; the most favorable concentrations of trivalent iron are in the range of 0001 - 001 ppm; preferably in the range of 0001 - 0080© ppm. - Use of gas diffusion cathode supplied with air or Air supplied with oxygen or pure oxygen. alkali salt, preferably the basic alkali Jo chloride, for example in simplified Ala, sodium chloride

And 1- hydrochloric acid, aqueous. The reasons for the aforementioned modifications can be explained as follows: - Addition of trivalent iron or another oxidizing compound with similar oxidation-reduction potential; Titanium is preserved in passive forms that resist corrosion; As a result of the formation of a protective oxide film© produced by an oxidizing compound; Even in the absence of electric current or chlorine, and this situation is identical to the opening and closing of the cell as a result of the emergency reasons for the sudden cessation of the electrical current; during work ; Electric current and chlorine are dissolved in a solution of hydrochloric acid; Its effect is added to that oxidizing compound; to re-pay a negative deed; The oxidizing compound is able to form a protective oxide; often when its redox potential 0 is sufficiently high to be at least zero volts NHE (usual hydrogen electrode); preferably from 17 - 56 V NHE; And when its concentration increases certain limited values; In the special case of trivalent iron this small concentration is 100 parts per million; While this concentration is preferably kept in the range of 0001 = 000 ppm ; In order to obtain high reliability and also efficient protection of the cathode chamber; As explained in the following description. vo can control the necessary concentration of the oxidizing compound in a solution of hydrochloric acid 0 circulating in the anode compartments of the cell by measuring af the redox potential or by Cus amperometric well known in his technical method of electrolysis; Through readily available commercial standards and tools. - Using a gas diffusion cathode ¢ in this type of aa Sl » the cathodic reaction takes place between the oxygen and protons migrating from the anode chamber through the membrane with the production of water. As already mentioned by At

and 1 -; This water, which forms a liquid that wets the walls of the cathode compartments, is a strong acid as a result of the migration of hydrochloric acid through the membrane. These acidic can include between 4; and 17 # depending on working conditions; Moreover, the cathode compartments are also exposed to a highly harmful DAD even if that is a GSH at a level of 0 less than that level typical for the anode compartments. The acidic liquid form also contains the oxidizing compound that is added to the hydrochloric acid liquids in the circuit inside the anode chambers; The oxidized compound, especially if it is in the form of a cation, Je cation, is the state of trivalent iron; It migrates through the membrane as a result of the electric field and accumulates in the reaction water inside the cathode cavity. Gas diffusion depends on the concentration of the oxidized compound in the acid reaction water. 0 Under the same working conditions, the concentration of the oxidized compound in the hydrochloric acid solution circulating in the anode chamber. If the latter is preserved as mentioned before at sufficiently high values; For example, in the case of trivalent iron in the range of 001 = 2000 ppm; The Lind concentration in the acid reaction water then reaches values sufficient to keep the titanium safely inactivated even when acidic values are reached; - 7 7 . On the other hand; The use of a gas diffusion cathode 1 eliminates the cathodic reaction to generate hydrogen which can be very hazardous with titanium; And all the possibility of embrittlement is also like the possibility of destroying the protective resistant rust oxides. = Once the necessary factors for the formation of protective titanium oxide are obtained by means of appropriate concentrations of the oxidized compound, each in the hydrochloric acid solution circulating through the anode chambers; and in the acidic water of the cathodic chamber; And it is necessary to avoid other © _ work envelopes that could cause them to melt. And it was found that obtaining the appropriate conditions in terms of security is beneficial.

- 11 -

Laie, the working temperature does not exceed Te degrees Celsius. The maximum concentration of hydrochloric acid in the circulating solution inside the anode compartments is Ye 7 by weight. Lind has observed that the hydrochloric acid solution circulates in The anode chambers efficiently increase the heat generated by the effect of the mol in the solution and in the membrane and by the electrochemical reactions. and that it is possible to keep the temperature within the constant limit of Te °C Lay by means of a current density of 00860 -0 5060 amperes per square metre; With a moderate flow rate for hydrochloric acid solutions eg 0 liters per hour per

square meter of film. - add base salt; Especially sodium chloride, a 0-hydrochloric acid solution circulating inside the anode chambers; This addition takes place to combine the transmission of the electrical current affected by protons with those affected by base cations 0, especially sodium cations. This is a union of electric current transmission; if properly balanced; Most of the acidic content of the cathodic reaction water is neutralized in the cathode compartments. Thus, the acidity can be reduced to values in the ratio of 1 - 0.1 : 0 7 taking into account the ; - LV 1, which is characterized by working conditions without the addition of alkali salts; and in dlls, especially for sodium chloride; It was noted that the addition of Ye - 56 grams per liter to 710) hydrochloric acid solutions substantially reduces the acidity of the cathodic reaction water with a certain additional fixed effect on titanium. These simple conditions also reduce the rate of silvering (metal conversion). Crude) for certain catalysts which may be incorporated into a gas diffusion cathode. During the test x with electrochemical cells as shown in Figure 1; It is explained that the circumstances mentioned above;

live

- 117 The addition of the oxidizing compound controls the temperature; maintaining the maximum concentration of the spinning acid and using gas diffusion electrodes; Hydrochloric acid is allowed to be used. Titanium for the installation of the anode and cathode compartments with sufficient long-term reliability, taking into account the corrosion. Sometimes it was found that the only weak points in the places of cracks are available where there is titanium that is not free to contact with the liquid form containing the oxidized compound. A typical example would be the ciphers 1 . peripheral anodic and cathodic chambers in the area of gaskets, and the problem is overcome by applying crack areas; mainly; oxides on the end blades and various nozzles; and a covering containing minerals from the platinum group such as those or oxides or mixtures from that source, which are then optionally mixed with titanium oxides concentrated in titanium titanium oxides Chau Sg; zirconium; zirconium niobium titanium | 0 in the molar ratio of titanium and ruthenium, and the corresponding example is an alloyed oxide of ruthenium. Another more reliable solution includes the use of; titanium alloys instead of . In particular; The interest is in terms of cost and availability SUI titanium, and in particular “the interest is in terms of cost and availability in a titanium-palladium alloy eo, and this alloy has a certain resistance in the cracks areas; As it is 0 / a titanium-palladium from rust in non-adhesive places, LS is known in this field; be fortified. In acidic solutions containing oxidizing compounds as described by Timm

M1 - Example: Lad relates to the efficiency of the electrochemical cells described above; shows a form? The relationship between the cell voltage and the current density obtained for each of them according to the technical methods of the present invention (1) and those of the previous field (7); and the anodic and cathodic compartments are made (referring to Figures ? and D 67 and Lao 14 in Figure 1) Made of titanium-palladium alloy 0.7 7, provided with end gaskets to prevent leakage made of EPDM elasbmer (referring to numbers 11 and 11 in Figure 1). The anode chamber is provided with an anode made of titanium mesh slice - Palladium 1,7 7 expanded, forming a non-surface lattice with a thickness of 1.9 millimeters, with quasi-certain holes of electron diameters of 01 mm in a row, equipped with an electrocatalytic cover, made of oxide mixtures of Rathenium, Iridium and Titanium (? in Figure 1) 0. The cathode chamber 1.7 ALES AGE 7 of titanium-palladium with a thickness of V0 mm is provided with quasi-rhombic apertures of diameters © and 01 mm, respectively, with a fine mesh (referring to figures 11 000 cd in Figure 1) with a concentration of * Ra 7 titanium - palladium (thickness in millimeters; semi-certain holes with diameters? and millimeters, respectively) also spot welded; the thin grid shall be provided with an electrically conductive cover made of platinum-iridium grid. The double-composite grid supports a gas diffusion cathode consisting of ELAT 0 electrodes commercially marketed by (30) E-TEX - USA 1 platinum on LCAN-72 XC activated carbon; with a total weight of 10 grams per square meter of metal. generous) ; Provided with a thin layer of ionic polymerized Pergluorinated material on the side opposite to that which is in contact with the double-composite lattice (2A) Figure 1). The two compartments are separated by a Nafion 1117 membrane (Nafion; available from Du Pont - USA) (1 in fig. 1) ; The anode is supplied with a solution of 7 01 hydrochloric acid and the cathode chamber is supplied with pure oxygen at a level slightly above the atmospheric pressure.

- 1 bar maintains the differential pressure at an indistinguishable level. 7 71 with a flow rate matching the equivalent increment between the two compartments and keeping the temperature at 00°C. Hydrochloric acid is added one part for every You with iron chloride so that the trivalent iron concentration reaches one million hydrochloric acid. The liquid drawn from the bottom of the cathode chamber makes an aqueous solution of +7 acid. Parts per million of trivalent iron 701 hydrochloric containing about You cell work takes an hour with various intermediate stops and long periods of inactivity in the presence of stagnant acid. There is no rot or rust even in the blade areas under the end gaskets; Another monitoring is done for the decomposition of the external fluids without detecting any residual titanium that can be estimated.

Av

Claims (1)

M * Elements of protection 1 1 - The electrolysis process of aqueous solutions of hydrochloric acid Y to produce chlorine 6 is carried out in electrolyzers consisting of at least ¥ of one electrochemical cell that includes a cathode and anode chamber 1 separated by a cationic type stainless ion exchange membrane; ° The two chambers of the cathode and anode 6 are occupied by a gas diffusion cathode and an anode made of inert enzyme-influenced material, equipped with an electrocatalytic cover to generate chlorine for chlorine; At least the gas diffusion cathode and the membrane are in close contact with (AY) A; Then the cathode chamber is supplied. 1:00 AH” with an inlet to supply gas containing 4 oxygen 0 and an outlet of zl AY reaction water; The anode compartment on Ve includes an inlet for the hydrochloric acid aqueous converter to electrolyze 1 40 and an outlet to remove the spent hydrochloric acid solution VY and the produced chlorine; This process is carried out in a cell where the anode chambers Vr 6 and the cathode are made of the same composition material, which is selected from the group of titanium Ve and titanium alloys, Alay titanium, into an aqueous solution of hydrochloric acid 12 to be decomposed electrically; An oxidizing compound with an oxidation-reduction potential le potential of 1 least equal to zero Volt NHE which must remain metabolized under VY oxidation state by chlorine and must be reduced when it reaches contact with YA cathode. AT Y 1 - The process Lia of element 1 ¢ is characterized by the said redox potential Y being between 17 and 56 Volt 11118. 1 ¥ - The process is characterized according to the element 1; That the aforementioned oxidized compound is an 7-valent trivalent iron. 1 8 — The process Gi of element ¥ is characterized by the trivalent iron concentration Y 0 being preserved in the range of 000011 = 001 ppm . 1 © - the process is distinguished according to the element; ; that the concentration mentioned is preserved in the range from 0001 to Cosel 1 + - The operation Uy of an element is distinguished; That the concentration be controlled by electrochemical Y screws or amperometric measurements. V 1 - the process is characterized according to the element; ; That the concentration of an aqueous solution of hydrochloric acid Y, to be electrolyzed, has a maximum value of 01 # by weight v, and the temperature of the solution All of hydrochloric acid ¢ consumed does not exceed Te degrees see 4 . Atl A 1 - The process is distinguished according to section 7 in that the temperature of the aqueous solution of the spent hydrochloric acid is kept under control by adjusting the flow rate of the aqueous solution of the hydrochloric acid to be electrolyzed $. 1 4 - The process according to item A is characterized by a flow rate of 100 liters per hour per 7 square meter of membrane ¢ and a Seve tar density — 11 amps per square meter of membrane. 0 1 - Characterizes the process Gg of element 1; After that, 0 alkali salt v is added to the aqueous solution of Y hydrochloric acid to be electrolyzed. 1 1 - The process is characterized according to item 01; The alkali salt mentioned above is sodium chloride, and its concentration is between ee - 00 grams per liter. 11 1- The process is distinguished according to the element ¢ in that it uses titanium or titanium alloy (titanium Y) as a mounting material for the anode and cathode stones, and is provided with a protective spur cover ST in the crack areas of each of the two chambers. Tim 10 “1 - The process according to element 11 is characterized by the fact that the aforementioned protective cover is made of metals of platinum group Y and their oxides are used as those or as a mixture of that source with the optional addition of 5 oxides to be selected. From group 1 titanium titanium niobium ¢ zirconium - titanium oxides 2 14- The process according to item 1 is characterized by the fact that the aforementioned protective cover is made of mixed Y oxides of ruthenium and titanium in an equal proportion, molar Y. Ve 1 - the process is characterized according to element 1; That the aforementioned constituent material is 1.1 7# of the ¥ weight of the titanium-palladium alloy. 1 01 - the process is characterized according to item 1; That the surface of the gas diffusion cathode, which is in close contact with the ion exchange membrane, is provided with a thin layer of ionomeric 0 corrosion-resistant polymer compatible with the membrane-forming material. cathode; That the aforementioned close contact between the KAGRD 1 The process is characterized according to the element - VY 1 00; It is obtained before the synthesis of the aforementioned gas diffusion and ion exchange membrane Y. Fusion electrolysis induces heat and pressure ¥ ‎Ae 1 - The process is characterized according to element 1; That the anode chamber was subjected to a higher pressure, Y, than the cathode chamber. 1 4 - The process is characterized according to the YA element by the differential pressure between the chambers of | The Y anode and the cathode are kept in a range between 0.10 = 6.1 bar att. 0 1 - The process according to element VA is characterized by the aforementioned gas diffusion cathode and the Y jon exchange membrane supported by a solid structure; Porous with many regions and gyal with the surface of the cathode gas diffusion corresponding to that in close contact with the membrane § ¢ placed in the aforementioned structure in the cathode compartment. 1 1?- The process according to item 01 is characterized by the aforementioned composition of a sheet of coarse steel 7 expanded or a grid and a sheet or expanded metal grid; Welded each other 3 with the aforementioned thin expanded metal plate or grid 1 made of titanium or titanium alloy. The said thin metal plate or grid shall be equipped with an electrically conductive rust-resistant cover. Atl