SE178680C1 - - Google Patents

Description

Inventors: W Teske and H Holemann Prtoritet requested from / 2 August 1959 (Federal Republic of Germany) When upon substitution of hydrogen with chlorine in organic compounds half of the supplied chlorine was converted to chlorine cotton and consequently b cs lost for the actual chlorination process of liar atervinn process. chlorine from this often unsavory by-product has become an important technical problem. In principle, two vagaries are possible for this purpose: either the chlorine water formed is reacted with air or oxygen using catalysts to water and chlorine, as is the case, for example, with the Deacon process in its older or more modern embodiments, or the gaseous chlorine water formed is absorbed in water or diluted hydrochloric acid to form hydrochloric acid and electrolyzes the resulting hydrochloric acid to give hydrogen and chlorine.

Attempts have been made to reduce the energy consumption of hydrochloric acid electrolysis, which consists of three proportions, namely the energy consumption for chlorine evolution at the anode, for overcoming the internal resistance of the electrolysis cell (in electrolyte and diaphragm) and for the evolution of water at the cathode. Dh of practical difference only chlorine development at graphite electrodes comes into question, the voltage and energy consumption, which especially comes ph chlorine development, can not be affected. Different Concerns about the conditions at the cathode, where the water development at graphite electrodes precedes with a certain overvoltage.

An opportunity to avoid or at least reduce the latter disadvantage consists in not replacing the cathodic hydrogen evolution with a different cathode process, which requires a lower voltage value at the cathode than the hydrogen evolution.

For example, U.S. Pat. No. 2,468,766 proposes that instead of discharging the H ÷ ions at the cathode, the metal ions be reduced from a higher valence stage to a lower valence stage in the electrolyte solution (e.g. from Fe + 4- + Fe +4 - or Cu + - + which precedes a lower voltage value on the lintodic velocity development.This possibility Or to hanfor to the magnitude of the redox potentials for the reactions in question.

As a result of this action, the evolution of water is eliminated, whereby special devices for separating cathode and anode gas become superfluous.

At the same time, voltage and energy consumption are reduced. A disadvantage of this method, however, is that the already reduced metal ions with lower valence in the electrolyte can be oxidized at the anode, which again meant a current loss. Part Or it is therefore necessary to immediately re-remove the reduced electrolyte from the cathode at the cathode, e.g. according to the hitherto known proposals through a porous cathode with carefully prescribed permeability.

The present invention now relates to a process for the electrolytic recovery of chlorine from aqueous hydrochloric acid, whereby all the disadvantages of the known processes are avoided as well as a considerable saving in voltage in comparison with the known processes is achieved.

The process according to the invention is characterized in that an aqueous solution of hydrochloric acid, such as is obtained, for example, by absorbing the gaseous chlorine water formed in water in the most common chlorination reactions as a by-product or diluted aqueous hydrochloric acid solution, is reacted with oxygen and / or oxygen-containing gas mixtures. , especially air, and with mercury metal during the addition of the oxidation process accelerating catalysts at temperatures of at least 40 ° C up to the boiling point of the hydrochloric acid reaction solution, preferably at 600-100 ° C, forming air lost mercury (2) chloride, that the The resulting hydrochloric acid, mercury (2) chloride containing the solution is electrolysed, chlorine being formed at the anode and mercury metal at the cathode, that the mercury separated at the cathode is recycled to the mercury-borne mercury-derived mercury-derived mercury. electrolysis step coming, on mercury (2) chloride utar possibly electrolyte after it has been liberated from its chlorine content - Recirculated in the process cycle, especially as an absorbent for gaseous chlorine water to form aqueous hydrochloric acid and by the oxidation of the mercury to mercury (2) chloride the water is continuously formed from the water.

According to the invention, as catalysts for the reaction of the aqueous hydrochloric acid solution with mercury metal and with oxygen and / or oxygen-containing gas mixtures, especially air, salts with at least two different valence stages, metals have proved suitable, the higher valence stage of which has sufficient oxidative mercury. - (1) - Chloride, the lower valence stage of which can be oxidized to the higher valence stack by the oxidizing agents used, such as, for example, oxygen or wool. Such salts can act either alone or in combination with each other as catalysts for the dissolution of mercury and the simultaneous oxidation of hydrogen chloride.

Namely, mercury is a vestibule. countrywise add l and consequently black oxidizable metal, oxidation ay the same to HgCl 2 with molecular oxygen and aqueous hydrochloric acid is not readily possible, ie even if it is carried out at the elevated temperature and with fine distribution of the reactants. Only by the addition of the said catalysts according to the present invention is the oxidation rate of the mercury to mercury (2) chloride significantly increased, so that the reaction can also be carried out on a technically usable scale. Particularly advantageous catalysts for this process step have been found to be, in particular, ferrous (3) chloride and copper (2) chloride, when used alone or in admixture with each other or with other metal compounds, such as palladium chloride, cobalt chloride, molybdates and vanadates. . In the examples given at the end of the present description, Examples 1-5, 8 and 10-16, which are only to give an exemplary embodiment and did not involve a slight elucidation of the use of catalysts according to the present invention, clearly show the mode of action and the usefulness of these catalysts. various experimental conditions.

For the conductive air process salt according to the invention, it has furthermore been found suitable to bring the oxygen and / or the oxygen-containing gas mixtures, especially air, and the liquid mercury into finely divided form for reaction with the aqueous solution of hydrochloric acid.

The electrolysis of the hydrochloric acid HgCl solution according to the process of the present invention is advantageously carried out between a graphite anode and a solid cathode of graphite or a metal with lower overvoltage, with respect to the separation of the mercury, or also between a graphite anode and mercury cathode, using the current density must be below the branch current density required for water development at the cathode.

The deposition of the water formed in the oxidation step, in which the mercury metal is converted to mercury (2) chloride, proceeds suitably by volatilization from the oxidation step, the condensate obtained having lower or at most as high a chlorine hydrogen content as the a -H 2 O mixture.

A further suitable embodiment of the invention consists in that the condensate formed, which at most has a chlorine water concentration corresponding to this concentration in the azeotropic HCl-H 2 O mixture, is once again fed with gaseous chlorine water and thus its water content is separated from the process cycle in form air concentrated hydrochloric acid.

Referring to Fig. 1 of the accompanying drawings, the embodiment of the process according to the invention for electrolytic recovery of the chlorine from the gaseous chlorine vessel obtained from the middle chlorination of organic substances is further explained by way of example.

Chlorine is supplied to the chlorination system 1 through the line 2. The chlorine water formed during the chlorination of the organic substances is fed through the line 3 to an absorption system 4 by hand and is then absorbed in an absorption liquid, preferably in the electrolysis-derived HgCl2 depleted electrolyte, which supplied through line 38 and. Iran derives the later described - 178,680 - electrolysis step, and possibly in the distillate, which originates from the oxidation step described in connection therewith and which is fed through line 20 to the absorption system 4. In addition, there is the possibility to supply water through line 6 and divert residual gases through line 5. , such as, for example, remaining organic compounds from the aging step. The concentrated aqueous solution of hydrochloric acid obtained in the absorption system 4 is fed through the lines 7 and 7 'to the oxidation system 10, for example a corresponding dimensioned reaction tower, and from a container 8 the additives of catalytic substances which may be required for the oxidation are fed through the line 9. In the oxidation chamber 10, which can be heated, e.g. by means of the heating tubes or heating hoses indicated by 11, the matting of the mercury to HgCl2 is carried out according to the equation Hg 2HCl + 1/2 O2HgCl2 -I- H2O, in that the catalyst and hydrochloric acid solutions supplied to the oxidation chamber 10 are brought into contact by suitable procedures. oxygen and / or oxygen-containing gases, such as air, and mercury metal, preferably in finely divided form. The desired turnover can also be achieved, for example, by intensive mechanical stirring of a quantity of mercury in one of the air resp. oxygen bubbles permeate hydrochloric acid solution, i.e. in a stirrer apparatus, or for example by sprinkling mercury in one with fine air resp. oxygen vesicles filled discharge, e.g. in a reaction tower or in any other lamp-hg apparatus. Fig. 1 schematically shows, for example, a tower-shaped oxidation apparatus. From the surface 39, air is blown in through the line 12 and the air distributor 12 'in finely divided form in the oxidation space 10. The mercury is introduced into the lean storage vessel 14 through the pump 15, the line 16 and the distributor 16' in finely divided form in the oxidation space, while the oxidizing hydrochloric acid solution flows through line 7 '. From the oxidation chamber 10, the unreacted mercury is passed through a. with a suitable closing device flap, e.g. a siphon, provided with line 13, is taken to the storage tank 14. The excess hydrochloric acid charged with hydrochloric acid passes through two coolers 17 and 18 and is discharged through line 19 or possibly fed in a cycle through line 19 'to line 12 and the oxidation chamber 10. The condensate separated in the cooler 17 is returned to the oxidation chamber 10, if the memory contains metal salts, while the free condensate free condensate obtained in the cooler 18 is pumped to an additional absorber 21 through the line 20 and the pump 23, where it is fed with fresh frau. chlorination system 1 initiated by lines 3 and 22 and hydrogen chloride as concentrated hydrochloric acid is discharged through line 21. In this way a part, possibly the whole amount, of the odor of mercury in HgCl 2 in the reaction vessel 10 is removed at the same time.

However, in addition to the stable in the electrolytic circuit referred to in Fig. 1, it can also be removed in the same stable in the same position according to the equation.

Hg 211C1 + 1/2 02 = HgCl2 + 1120 formed the water, which, if not deposited, on impermissible salt would dilute the circulating electrolyte, which can be done, for example, with the aid of the joule heat developed in the electrolysis cell 26, which leads to the chlorine flowing out through the line 32 absorbs water vapor resp. a hydrochloric acid vapor corresponding to the temperature and concentration ratios. From the chlorine formed in the electrolytic cell, it is then possible, if necessary by means of cooling and drying systems of conventional construction, to separate the water resp. hydrochloric acid solution aga rum. In addition, there is the additional possibility of pre-empting the selection resp. hydrochloric acid from the electrolyte depleted of HgCl2 from the electrolysis cell in the hot state, for example by means of an air stream, if at the same time the removal of chlorine from the electrolyte is sought, or by other suitable measures, such as yekuum oranging.

The concentrated hydrochloric acid mercury chloride solution formed in the oxidation vessel 10 is supplied with the aid of the pump 15 'through the line 25 to one or more electrolysis cells 26 so that they are divided into mercury and chlorine.

Fig. 1 shows, by way of example, an electrolysis cell with a liquid k-mercury (31) cathode in horizontal arrangement and two horizontally arranged graphite anodes (30) with associated tight supply lines 28 and 27. However, the electrolysis can also be carried out in cells of another design. , for example with vertical floating cathodes or vertical rigid cathodes, e.g. of graphite, or of mercury-moistened metals, such as copper, nickel, or alloys (monel metal). The mercury 31 separated in the electrolytic cell is fed through the conduit 29 to the storage tank 14 and from there to the oxidation chamber 10. The chlorine formed at the anode leaves the electrolytic cell through the drain line 32, the electrolyte (2) chloride depleted electrolyte through the drain line 33 and can the blow-off tower 34 is freed of its chlorine content by Iran through an air stream divided through the line 35 and divided into the distributor 35 '. The chlorine-containing air leaves the exhaust tower through line 36 and the chlorine-poor electrolyte is returned with the aid of the pump 37 and line 38 Ater - 817 680 - to the absorber 4 for absorption of the gaseous chlorine water. Optionally, in the drain lines 32 and 36, additional devices may be provided for separating entrained water droplets and coolers for separating the volatilized hydrochloric acid and thereby for removing the water formed in the oxidation vessel 10 from the circuit.

In Fig. 1 Concerns get better clarity partly joke the storekeeper and the transport device occupied, which should be connected between the various devices.

The sub-steps known for the procedure: absorption of chlorine hydrogen, oxidation of mercury and hydrochloric acid with oxygen or oxygen-containing gas mixtures to mercury (2) chloride and water, discharge of the water formed and the electrolytic sand division of the mercury formed during the oxidation can be combined in any order; especially can with deviant Iran. the diagram of the embodiment according to Fig. 1 the introduction of the gaseous chlorine in the cycle of the process set also takes place between the oxidation and electrolysis steps.

For the electrolysis of the hydrochloric acid mercury (2) chloride solution according to the method according to the invention, different embodiments of electrolysis cells can be used, of which two suitable embodiments are shown in Figs. 2 and 3.

For example, according to Fig. 2, the electrolysis can be performed between two fixed electrodes, 50 denoting the electrolyte vessel, 51 the anode and 52 the cathode, which are connected via a power supply lines 57 and 58 to a lamp-like direct current head. The anode in this embodiment probably consists of graphite, the cathode either also of graphite or of one. amalgamated and thus resistant to hydrochloric acid mercury (2) chloride solution resistant metal (such as amalgamated nickel) or an amalgamated metal alloy, such as monel, in which the separation of mercury proceeds with only very little overvoltage. The electrolytic cell Or according to Fig. 2 up to level 56 filled with electrolyte and provided with a lead 54a for the fresh electrolyte and with drain lines for the formed chlorine and the consumed electrolyte (in Fig. 2 shown jointly through the lead tube 54) and for it at the cathode separated, from this descending oeh at the threat of the man in a suitably trained collection chamber 55 collected the mercury, e.g. with a siphon. Lamply, the mercury collected at the bottom of the cell is likewise connected by a metallic conductive connection 59 to the negative current supply line 58 to cathodically polarize the same.

The electrolytic sand division of the hydrochloric acid (2) chloride solution between a mercury cathode and a graphite anode can also be advantageously performed. Fig. 3 shows as an example a lamp-hg electrolysis cell operated for this purpose. In the electrolytic cell 61 Or, a graphite anode 65 arranged horizontally opposite a horizontal mercury cathode 67. These two electrodes are supplied through the current supply connections 66 and 68 with direct current. Arranged in the lid 62 of the cell is a diverter tube 64 for the formed Mo. clean. The electrolyte is supplied through the supply line 69, fills the electrolytic cell up to the level of the lead pipe 70 and, after separation of the supplied mercury supply through the pipe 70, the separated mercury can be taken out of the cell through a suitable sparring device, e.g. siphon 63. In this embodiment there is furthermore the possibility of introducing elemental mercury into the cell for flushing purposes, e.g. through the electrolyte supply line 69.

For carrying out the electrolysis according to the method of the present invention, however, electrolytic cells can also be used to advantage, in which the working mercury cathode Or arranged vertically or in an inclined layer, in particular those embodiments in which either one or more mercury-moistened metal plates or otherwise shaped metal bodies , sasoin eg, band, alternating foras through. the electrolyte to be electrolysed, and adjacent thereto by a mercury bass finger, or sadam, at which the mercury trickles down over an inclined or vertical metal surface.

The electrolysis of the hydrochloric acid mercury (2) chloride solution according to the invention requires due to the low separation potential of mercury lower voltage amounts On in the already proposed procedures for electrolysis of aqueous solutions of hydrochloric acid, in which the avoidance of hydrogen evolution at the cathode metal ions from a higher valence stage to a lower valence stage (eg reduction of Fe F ++ ions or Cu ++ ions to Fe ++ ions or Cu + ions). From the known normal potentials for the individual electrode reactions, the equilibrium voltages for the electrolysis equations are calculated: I HCl = H2 Cl2 to 1.3587 V II CuCl, = CuClCl, to 1.0137 V and III Hg CI, = Hg Cl2 to 0.4977 V.

These values apply in each particular case to the activity. In the ionic species in question, the values for equations II and III further require different corrections for the concentrations (respectively activities) which can be obtained in hydrochloric acid solutions. From the equations, however, it is clear that the electrolysis voltage which must be used for an electrolysis corresponding to the equations decreases in the order file I to III.

Since the Yid electrolysis must be measured with further polymerization of the electrodes, the actual opposing voltages (polarization voltages) can be determined with the aid of air current potential curves, which on their own edge were measured without tension using auxiliary electrodes. Taking from these curves in each particular case the value of the anode and cathode potentials EA and E belonging to the same current density, calculated from both values according to the formula EEA - E., taking into account the sign for EA .and Ex. and the polarization voltage E, sd is obtained e.g. In graphite electrodes, the polarization voltages shown in Fig. 4 are dependent on the tightness used. In Fig. 1, curve C represents the polarization voltage in 21% hydrochloric acid, curve B the polarization voltage in hydrochloric acid of the same concentration with an addition of copper (2) chloride, curve A the polarization voltage in 21% hydrochloric acid with an addition of mercury. (2) chloride, and curve A 'polarization voltage in 21% hydrochloric acid with the addition of mercury (2) chloride and copper (2) chloride, in all cases depending on the current density. As can be seen from curve B, the addition of copper (2) chloride already produces a significant reduction in the polarization voltage; however, due to the presence of mercury (2) chloride in hydrochloric acid solutions, the polarization voltage was further reduced to a considerable degree. The voltage saving achieved according to the above yid use of graphite electrodes for the electrolysis yid The recovery method according to the present invention is Miles amen in other electrode combinations, for example a graphite anode with a rigid cathode, e.g. of mercury-moistened metals (eg copper, nickel) or metal alloys (eg monel metal) which, in the amalgamated state, do not have a significant essential overvoltage for the separation of mercury and have sufficient corrosion resistance to hydrochloric acid (2) chloride solutions. This voltage saving also occurs when hydrochloric acid mercury-1 (2) chloride solutions are electrolyzed between a graphite anode and a liquid cathode, especially mercury.

The concentration of mercury (2) chloride in the electrolyte also plays a significant role. Since from the hydrochloric acid solution of mercury (2) chloride yid the cathode yid low tightness mercury is separated with low voltage consumption, but yid Mining of the current tightness Above the value of it gets this separation at the concentration of mercury- (2) -chloride in question However, if the spruce current voltage rises to the level which will cause water separation, the electrolysis must be carried out at stranatates which are below the said critical spruce tension. Electrolyzed hydrochloric acid solutions with different mercury- (2) -chlorinated concentrations and determined by the measured current density potential curves are the current density values, at which water separation enters at the cathode (= spruce tightness), as shown for these spruce flow rates, the relationship shown in fig. between spruce current and mercury (2) chloride concentration. Within the area enclosed by the abscissa axis OG and the curve OF, only the separation of mercury and no water development takes place, while in the area covered above the curve OF further, unrestricted water development takes place. Fig. 5 shows, for example, that at a HgCl2 concentration of 100 g / l the cathodic current density of about 630 A / m2 must not be exceeded, so that the undesirable separation of irate must be completely avoided.

Compared to the known processes for electrolytic recovery of chlorine from chlorine, the process according to the present invention has the advantage that the electrical energy consumption required for the electrolysis is somewhat lower than that of the former process. In that the formation method according to the invention avoids the formation of material at the cathode, the electrolysis is substantially simplified in comparison with the known process softeners. Salunda eliminates a non-cloudy hazardous contamination of the chlorine formed with water-gas. Furthermore, no special measures are required as protection against atheroxidation.

The following Examples 1-5 describe the conversion of an aqueous hydrochloric acid solution with air and mercury metal to mercury (2) chloride with and without the addition of catalysts based on test results, the particular effects on the catalysts as well as the feasibility of this conversion step according to the procedure according to the invention is clear.

Example 6 contains a series of test data, in which the considerable voltage savings in the electrolysis according to the method of the present invention in comparison with the known methods are shown.

Example 7 describes the invention as an example of the continuous electrolysis of a hydrochloric acid HgCl2 solution between graphite electrodes and in Example 8 between graphitic anodes and a mercury cathode, examples of which in particular the recovery of anhydrous chlorine, while Example 9 misses the feasibility of regeneration. of an electrolysis solution depleted in HgCl2.

In the following examples 10-16, the same procedure was used as in examples 2-4 to show the effect of varying working conditions and on different additives on the process of transferring mercury to mercury (2) chloride.

The process set according to the invention can of course be carried out with other apparatus devices than those described in the above-mentioned examples 6-178880, as well as with other concentrations of the solutions described therein.

Example 1.

A glass tube 3 cm in diameter and 60 cm long filled with glass beads, at its lower end provided with supply lines for air and drainage pipes for mercury and hydrochloric acid and at its upper spirit with a drainage line for air and supply lines for mercury and hydrochloric acid. The glass tube is filled with 21% hydrochloric acid. While air in a finely divided state is blown in at a speed of 300-350 1 / h at the lower end of the column through a sintered glass body (Glasfritte), about 30 ml of hydrochloric acid of the said concentration is passed from above and through a suitable drip device about 60 ml finely divided mercury drop by the hour. The said apparatus is kept at room temperature. After the course of 1 round number 6 hours have only small amounts of mercury loaded in the total amount of hydrochloric acid (the content of the glass column and drained amount of hydrochloric acid).

Examples 2. In a 500 ml glass flask equipped with a stirrer, air supply and drain pipes, reflux condenser and thermometer, about 15 g of mercury are stirred while passing air at 70 ° C into 250 ml of about 23% hydrochloric acid for 9 hours. After each 2-hour period, an analytical sample is taken and the content of mercury (2) chloride therein is determined analytically on per se edge Ott and recalculated on the starting volume of the solution. In this case, the values given in Table 1 for the dissolved amount of mercury are obtained, which are expressed in milliequivalents so that it can be better compared with the results in the following examples.

Table 1.

Sample taken after 24678 9 hours Dissolved amount of mercury in milliequivalents0.35 0.70 1.83 3.56 6.33 8.94 In some cases, already markedly larger amounts of mercury had already been dissolved than in Example 1. However, the oxidation rate also shows of the mercury in crude hydrochloric acid even at MI-Ad temperature be too low to be used practically.

Example 3.

In the same test device as in Example 2, 4.31 g of anhydrous jam (3) chloride are dissolved in 250 ml of about 21% hydrochloric acid and, while passing air (120 l / h), 13.47 g of mercury are stirred in 70 ° C. After each period of 2 hours, an analytical sample is taken from the hydrochloric acid, the content of mercury (2) chloride and iron (2) chloride is analyzed analytically and recalculated. total water volume 250 ml. From these values it is calculated how large the total amount of oxidized mercury is in milliequivalents, the proportion oxidized by transferring air oxygen to the mercury-hydrochloric acid system, and what proportion of the mercury oxidized at the expense of the present iron (3) the chloride at the end of each time period. In this case, the values given in Table 2 are obtained.

Trial time in hours (from the beginning of the front) Total amount lost Hg meq. Table 2.

Percentage of mercury oxidized by FeCl3 meq. Percentage of mercury oxidized by atmospheric oxygen meq. 2 2,603 25,90 25,90 0,00 0,00 4 5,858,16,41,972,0 6 8,890 88,6,82,92,90 8 10,9109,00 3,76 105,24 95,60 Am table 2 shows that the oxidation rate compared with Example 2 has been increased to a very significant degree and that the oxidized amount of mercury has been largely oxidized with the aid of supplied oxygen. The added iron salt is present at the end of the experiment to a large extent in 3-form form, namely 6.13 moles of FeCl2 per 1 mole of FeCl2, waif & jam (3) -chloride mainly acting as an oxygen transfer agent during the oxidation of the mercury.

Example 4.

In the same test device as that used in Examples 2 and 3, 20.54 g of mercury are treated in 300 ml of hydrochloric acid (about 21% "), containing 5.25 g of CuCl2, for 7 hours during the introduction. of air (120 I / h) and heating to 700 G. After each hour, analytical samples are taken, the content of which in mercury- (2) -chloride, copper- (2) -chloride and copper- (1) -Idoride are determined analytically and recalculated In addition, the proportion of mercury oxidized by atmospheric oxygen and the proportion of mercury oxidized to the reduced amount of copper in each case (ie corresponding to the amount of copper present) are calculated. kb-rid) The results are given in Table 3.

- - Trial time in hours (from the beginning of the fdrstiket) Total amount lost Hg mekv. Table 3.

Percentage of Oct by CuCL oxidized mercury meq. Proportion of the common = oxidized oxygen oxidized mercury meq. 1 4,40,60 22,19 18,41 45, 2 7,72 76,731,80 44,959, 3 11,80 117,28,60 88,75,60 4 13,08 130,9,00 121.00 93 , 16,76 161,5,34 156,16 96,70 6 18,87 187,1,56 185,94 99, 7 20,204,2,18 202,02 98.90 As already shown by this Mrs & occurring color change and as is also apparent from the figures in column 4 of Table 3, the oxidation of mercury to a start proceeds via conversion of the copper (2) chloride to copper (1) chloride. During the course of the oxidation, however, in accordance with the results given in the last column, the total amount of mercury oxidized at the expense of the aerated oxygen rises rapidly to almost 100%. Even the copper (2) chloride, like the iron (3) chloride given in the preceding example, acts only as a catalyst for the transfer of the atmospheric acid to the mercury hydrochloric acid system.

Example 5.

A vertically stable glass tube with a diameter of about 5 cm and a length of 120 cm is held with the aid of a hot water jacket at 65 ° C. The glass tube is blown in from below through a sintered glass body finely divided air at a speed of air 11 to 26 l / h. The filling in the glass tube consists of air 1350 ml about 21% hydrochloric acid, as inside. hailer 71.8 g / l copper (2) chloride. From a drip device, a total of 600 g of mercury in fine distribution is allowed to drip through the hydrochloric acid over the course of 50 minutes. After this time, a total of 6.45 g of mercury (2) chloride is present in the aqueous hydrochloric acid solution. Thus, the oxidation rate, i.e. the amount of mercury dissolved per hour has further increased considerably in this embodiment of the procedure compared to the method used in Examples 2-4. At this mode of operation it can already be seen at lower temperatures, e.g. at 53 ° C, an amount of mercury applied to the procedure set forth in Examples 2-4 is brought to solution.

Example 6.

The following solutions are prepared one after the other: a) hydrochloric acid 21%, b) hydrochloric acid 21% with dari lost 65 g / l crystallized copper chloride (CuCl 2 2H 2 O), c) hydrochloric acid 21% with dari lost 500 g / l mercury (2) chloride , d) hydrochloric acid 21% with dari lost 500 g / l mercury (2) chloride + 65 g / l crystallized copper chloride (CuCl2 • 2E120).

The solutions a, b, e and d are electrolysed one after the other between the electrode combinations in the same electrolysis cell given in Table 4 below, especially at the same electrode size and the same electrode distance, the associated current voltage curves are taken up and by comparing the current voltage curve of the same hydrochloric acid concentration (solution a), the voltage saving achieved by the additives at different current densities is determined.

Table 4.

Electrolyte Meaning Significant dream Electrode combination AnodeCathode Voltage saving V Yid current- Whet A / m2 HCl, CuCl2 Graphite Graphite 0.2 0.59 500 0.61 7 0.61 1000 0.59 12 HCl, HgCl2 Graphite Graphite 0.76 2 0.82 500 0.82 7 0.80 1000 0.79 12 HCl, HgCl, CuCl, Graphite Graphite 0.83 2 0.87 500 Electrolyte Meaning. Intravenous airmen HC1, HgCl2 - - Electrode combination AnodeCathode Graphite Mercury Silver Voltage saving V 0.89 0.87 0.87 1.08 1.15 1.13 1 1.11 1.16 At current density 750 1000 1250 250 500 750 1000 1250 1500 HCl, HgCl2 CuCl2 Graphite Mercury 0.86 2 0.90 500 0.88 7 0.86 1000 0.82 12 0.77 1500 HCl, HgCl2 Graphite Monel 0.72 2 0.7500 0.71 7 0.68 1000 0.67 12 0.64 1500 HCl, HgCl2 GuCl2 Grant Monel 0.72 0.79 500 0.74 7 0.69 1000 0.61 12 0.59 1500 Table 4 shows that the presence of mercury (2) chloride leads to a substantial decrease in the electrolysis voltage beyond the decrease. which can be achieved with the already known copper (2) chloride. The presence of copper (2) chloride in hydrochloric acid, which contains mercury (2) chloride, affects only insignificantly the stress ratios in contrast to the role played by copper (2) chloride in hydrochloric acid, which is free from mercury (2) chloride. 2) -chloride additives. What has been said about the role of copper (2) chloride in electrolysis applies to the same salt for the iron (3) chloride in question as well as the oxidation catalyst.

Example 7.

In a closed electrolytic cell provided with devices for supplying and diverting the electrolyte and mercury, as well as with a gas diverting tube for the evolved chlorine gas, a solution containing 228.2 g / l hydrochloric acid (HCl), 250 g / l is electrolyzed. mercury (2) chloride and 37.7 g / l copper (2) chloride, between graphite electrodes with a current equivalent to a cathodic and anodic current of 1500 A / m2. After the solution has passed twice through the cell at a rate of about 2.15 l / h, the concentration of hydrochloric acid and copper chloride is practically unchanged, while the concentration of mercury chloride has dropped to 2 g / l. The developed chlorine contains no vate; at the cathode have only mercury compounds reduce ats.

Example 8.

A closed electrolytic cell, which in principle is formed according to the usual cells for chlor-alkali electrolysis according to the mercury procedure, contains in a gas and vfitsketate bath ladle a horizontal mercury cathode with 125 cm2 electrode surface, above which two horizontal ones, with bores for the removal of chlorine, graphite provided one with 50 ent2 underside). It carried inlet and outlet rafters for the mercury, each a supply and drain line of mercury and electrolyte, a drain line for chlorine (from the gas chamber), thermometer, manometer and other connections for control means. While placing the anode and cathode under voltage from a connected sham cold, the electrolyte preheated to 85 ° C, containing 220.4 g / l hydrochloric acid, 251.6 g / l mercury (2) chloride and 43.0 g / l of copper (2) chloride, fill the cell and during the current passage (at a rate of 0.4 l / h) flow through the cell and at the same time mercury thread into and out of the cell in countercurrent to the electrolyte. The cell is loaded with an average of 12.67 A (corresponding to a current density of 1013 A / m2 anodic or 1267 A / m2 cathodic) and exhibits at the temperature - -9 air 17-50 ° C, which settles in the cell, an average voltage of 1.435 V. The chlorine developed in the cell at the anode is collected and analyzed. It contains no irate. The effluent electrolyte contains 222.6 g / l HCl, 153.1 g / l HgG12, 43.3 g / l CuCl2 and 0.7 g / l dissolved chlorine. By determining the change in the mercury content from the filling of the cell and the run-off of the electrolyte, the cathodic current yield is determined and by absorbing the chlorine in NaOH the anodic current yield. Under the specified conditions, the cathodic current yield is 86% and the anodic 80%. This results in an energy consumption of 1.35 kWh / kg for the chlorine developed from the cell, the current exchange and energy consumption are dependent on a) the electrode distance, b) the conductivity of the electrolyte, c) the conduction of the liquid currents in the cell, d) the temperature and e) the load in the cell .

Example 9.

To 300 ml of an electrolyte containing 330 g / l of mercury (2) chloride and 65.3 g / l of copper (2) chloride was added in the same apparatus as that used in Examples 2-4, 67 .6 g of mercury metal and stirring are carried out under air passage. After 29 hours it has-. na livicksilvermangd upplOsts. According to the analysis, the electrolyte contains 629 g / l of mercury (2) chloride and can be used for electrolysis.

Example 10.

If, instead of the solution used in Example 4, a solution of 30.43 g of mercury in 400 ml of hydrochloric acid (about 21.5%) is stirred, to which is added 38.72 g of copper (2) chloride, at 930 G, while on the same salt as in Examples 2-4 air was passed, 401 milliequivalents of Hg per hour were dissolved, and liters, of which during this time 213 milliequivalents were oxidized by the supplied atmospheric oxygen.

Example 11. 400 ml of hydrochloric acid (about 21.5%) are added with 50 g of titanium (4) chloride and reacted under air passage at 87 ° C together with 29.58 g of mercury. The after 7 hours or-Ulna solution contains 24.3 milliequivalents of mercury (2) chloride.

Example 12.

The same hydrochloric acid moiety with the same HG1 concentration as in Example 11 was continued with 8.7 g of potassium perrhenate. In about 9 hours, 50.6 milliequivalents of mercury dissolve as mercury (2) chloride during air passage and under stirring at 89 ° G.

The addition of titanium (4) chloride according to Example 11 and potassium perrhenate according to Example 12 thus achieves a faster dissolution of the mercury against the action of pure hydrochloric acid according to Example 2.

Example 13. 20 g of sodium molybdate are dissolved in 400 ml of hydrochloric acid (about 21.5%) and stirred at 87 DEG C. during air introduction with 29.7 g of mercury. After 8 hours, the mercury is substantially converted to calomel. After adding 50 g of CuCl2 21 - L0 to this batch, the oxidation (at 84 ° C) is practically complete in 1 hour, i.e. at this hour a Mining of the mercury (2) chloride content is achieved with 740 milliequivalents (rated at 1 liter solution and 1 hour), of which taking into account the amount of copper (1) chloride formed during this time 503 milliequivalents oxidized by the atmospheric oxygen.

Similarly, when a small amount of copper (2) chloride or a lot of copper (2) chloride is present, a molybdate addition is present, favorable to the dissolution of the mercury, as is apparent from the following experiments. 14.44 5.3 70.4 64, 16.0 32.9 276.7 159.0 Example 14.

Vanadates act in a similar way to molybdates. 20.83 g NaVO3, dissolved in 400 ml HCl, give with mercury and air at 86 ° C partly calomel and partly mercury (2) chloride. By adding 33.48 g of copper (2) chloride, a rapid dissolution of the calomel and the remaining mercury is obtained, whereby a mercury solution of 352 milliequivalents per hour and liter, respectively, an air oxidation ay mercury of 321.8 milliequivalents per hour and liters can be achieved.

On the corresponding salt, a combination of molybdate, vanadate and copper (2) chloride shows good catalytic effect in oxidation, in that 670 milliequivalents of mercury per liter and hour can be dissolved, if you convert 19.75 g NaVO 3, 19.89 g Na 2 MO 4, 39.42 g CuCl 2 with 400 ml hydrochloric acid (about 21%) 30.26 g Hg and air.

Example 15.

Thus, according to Examples 13 and 14, the effect of the molybdates and vanadates can be increased by the addition of CuCl2, or conversely its catalytic effect in the dissolution of mercury can be increased by the addition of vanadate and / or molybdate, that the mutual effect of jam and copper compounds is not negligible. . 4.16 g of FeCl 3 and 3.16 g of CuCl 2 dissolved in 300 ml of HCl (about 21.5%) give at 78 ° C the solution of 127 milliequivalents of mercury in 7 hours.

One. additive air manganese (2) sulphate provided- Table 5.

Additives to 400 ml HCl (approx. 21.5%) Hg-upp- Sodium- Copper solution molybdate (2) -1doride meq / l. h Of which oxidized with- deist air mekv / 1. h - - more on the other hand an improvement of the catalytic effect of jama, as shown in Table 6 below (where 21.5% hydrochloric acid was used as solvent and the treatment was carried out at 75 ° C).

Table 6.

HCl volume nil Additives Hg solution meq / 1. h Air toxin of Hg meq / 1. h 2 300 4.31 g FeCl 2 5.63 g FeCl 2 {1.1 g'InSO 4 J 54 69 52.4 66, Example 16.

The effect of copper (2) chloride can be affected by the addition of other metal compounds which can undergo valence exchange, as already shown in examples 13 and 14. A palladium chloride additive and a cobalt chloride additive to the hydrochloric acid copper (2) chloride solution act on the same salt. .

The experiments with these additives are carried out as in the previous examples in 400 ml of HCl (about 21.5% -i.g). and give the results given in Table 7.

Table 7.

Air oxidation of mercury, etc. h .CuCl2 27.32 gl91 ° C PdCl2 0.2 g j CuCl3 39.6 g91 and CoCl2 19.8 gl This addition specifically promotes the -6.1 oxidation of the copper (1) chloride formed intermediate upon dissolution of the mercury.

Examples 2-4, 8 and 10-16 show that a series of metal salts with alternating valence, individually or in combination with each other, catalyze the reaction of mercury with hydrogen chloride and oxygen in aqueous phase according to the principle of the present process. •

Claims (8)

Patent ans per fik: 1. A method for the electrolytic recovery of chlorine from aqueous hydrochloric acid, characterized in that an aqueous solution of hydrochloric acid is reacted with oxygen and / or oxygen-containing gas mixtures, especially air, and with mercury metal with the addition of the oxidation process. 40 ° C up to the boiling point of the hydrochloric acid reaction solution, preferably at 60-100 ° C, to give dissolved mercury (2) chloride, electrolysing the resulting hydrochloric acid, mercury (2) chloride containing the solution, whereby at the anode is formed, which is recovered and at the cathode mercury metal, that the mercury metal separated at the cathode is returned to the mercury (2) chloride for the production of the mercury (2) chloride, that the electrolyte (2) chloride resulting on electrolysis depleted of the electrolyte that it is freed from its chlorine content, re-enters the procedural cycle, and is used in particular as an absorbent for gaseous chlorine water to form the aqueous hydrochloric acid intended for the process for processing and that the water formed during the oxidation of the mercury to mercury (2) chloride is removed from the process cycle. 2. A kit according to claim 1, characterized in that as catalysts for the reaction of the aqueous solution of hydrochloric acid with mercury metal and with oxygen and / or oxygen-containing gas mixtures, especially air, salts of metals appearing at least in two different valence stages are used. The valence stage has sufficient oxidation capacity over metallic mercury and mercury (1) chloride and whose lower valence stage can be oxidized again to the higher valence stage by the oxidizing agents used. Salt according to claim 1-2, characterized in that oxygen and / or oxygen containing gas mixtures, especially air, and the liquid mercury in finely divided form. as reacted with the aqueous solution of hydrochloric acid. 4. A kit according to claim 1, characterized in that the electrolysis of the hydrochloric acid (2) chloride solution is carried out between a graphite anode and a solid cathode of graphite or a metal with a lower overvoltage with respect to the separation of mercury, 5. according to claim 1, characterized in that the electrolysis of the hydrochloric acid of the mercury (2) chloride solution is carried out between a graphite anode and a mercury cathode. Salt according to claims 1, 4 and 5, characterized in that the electrolysis of the hydrochloric acid (2) chloride solution takes place with a current density which increases below the branch current density required for hydrogen development at the cathode. 7. A claim according to claim 1, characterized in that the deposition of the water formed in the oxidation stone of mercury metal to mercury (2) chloride in the presence of hydrochloric acid takes place by volatilization and that the obtained condensate has a lower or equally high chlorine water content as the azeotropic H 2 O mixture. Hg-up- AdditiveTemperature reading meq / 1. h 1134 2189 - —11 8. A set according to claim 7, characterized in that its water content is separated from the form by the fact that the condensate formed, which has a chlorine-hydrogen concentration in the form of a concentrated hydrochloric acid in the form of the concentrated cycle. of the azeotropic HCl-H2 O mixture, then matted with gaseous chlorine cotton and the like.