FI57244C - OIL ANCHORING FOER FRAMSTAELLNING AV SODIUMPOLYSULFID - Google Patents

Description

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JjBA lJ 11 UTLÄOG NINGSSKRI FT 57244 C (45) Fat? Ntti cyinr ^, tty 10 07 10-30 ^ ^ (51) Kv.lk. '/ Int.CI. * C 01 B 17 / 2W1 D 21 σ 11 / 00 SUOM I — FI N LAND (21) P «* nttih» kemu * - P * t * ntan «6fcnlng 3177/71 (22) Hakamltpllvft — AMflknlnitdag 05.11.71 ^ '(23) AlkupUvt — Glltighttidag 05.11.71 (41) ) Interpreters JulklMk ·! - Bllvlt offmtcllg 07.05.72

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Patent · och ragistaratyralaan 'An <ekan utlagd och utl.ikrift * n pubiiccrad 31.03.80 (32) (33) (31) Requested «uoikwi —Begird priorhet 06.11.70 USA (US) 87501+ (71) The Mead Corporation, Talbott Tower, Dayton, Ohio 45402, USA (72) Glen Charles Smith, Chillicothe, Ohio, Frederick William Sanders,

The present invention relates to a process and an apparatus for oxidizing a solution containing sodium sulphide or sodium hydrogen sulphide with an oxygen-containing gas an alkaline cooking liquid to form a loose-containing substance.

Several fundamentally different methods are known for the preparation of sodium polysulfide, either as the main product or as a smaller by-product. These include electrochemical procedures, redox methods, and catalytic methods.

U.S. Patent No. 3,249,522 discloses the use of hydrogen sulfide gas as a fuel in an electrochemical fuel cell with sulfur products, sulfides, polysulfides, and generated electric current. The fuel cell itself has an anode and a cathode separated by an ion exchange membrane, wherein the anode is platinum catalyzed carbon and the cathode is nickel catalyzed carbon. Hydrogen sulfide is fed to the anode compartment and oxygen is fed to the cathode compartment with the electrolyte basic. The method oxidizes hydrogen sulfide at the anode and reduces oxygen at the cathode.

U.S. Patent No. 3,409,520 discloses an electrochemical device for removing hydrogen sulfide from a natural gas mixture, which device is electrolytic in nature. The electrolytic cell has an anode spaced apart and separated from the cathode by a diffusion barrier. The acidic electrolyte has a sulfuric anodic oxidation product, whereas hydrogen gas D 21 C 3/02 57244 2 is instead formed at the cathode. When the electrolyte is basic, the anodic oxidation product is a polysulfide with sulfur gas formed at the cathode. This device requires electrical power from an external source.

U.S. Patent No. 3 * 171 25 * 1 discloses the oxidation of hydrogen sulfide in a catalytic alkaline solution to form sulfur. The catalyst is a phthalocyanine complex that is soluble in aqueous sulfide but insoluble in sulfide-free aqueous solutions, whereupon the catalyst is recovered in coagulated form and recovered.

U.S. Patent No. 2,135,879 discloses calcium hydrogen sulfide, i. reaction product of calcium oxide or calcium hydroxide and hydrogen sulphide, oxidation with air using a nickel sulphide catalyst to give polysulphide, thiosulphate and sulphate in a ratio of 7: 73 · * 17 · To increase the amount of polysulphide, mix 0.1-1.0% hydrogen sulphide gas with

From the treatment of pulp, it is known that the use of sodium polysulfide (hereinafter referred to as polysulfide) in cooking liquor increases the yield (see U.S. Patent No. 3,216,887 and its references). Various methods for forming a polysulfide are described, including, e.g., dissolving sulfur in an aqueous solution of sodium hydroxide or sodium sulfide. The preparation of a polysulfide by oxidation of neutral sodium hydrogen sulfide with air has also been described. U.S. Patent No. 3,216,887 also states that white liquor is strongly basic and its sulfide is not readily oxidizable by air. In addition, oxidation of the white liquor gives sodium thiosulfate and not sodium polysulfide. This patent proposes mixing white liquor and black liquor and oxidizing sulfide to produce polysulfide and thiosulfate. However, the values shown show that the amount of polysulfide produced, calculated in grams of Na2S2 per liter, is less than the amount of thiosulfate, expressed in grams of Na2S2O2 per liter.

U.S. Patent 2 * 459,907 discloses a general method for reacting a gas and a liquid in contact with a carbon-based contact mass. Even if the reaction of U.S. Pat. No. 3,216,887 were carried out in the column disclosed in U.S. Pat. No. 2 * 159,907, no polysulfide would be produced at the rate of the process of this invention, and even if porous carbon mass is in contact with both reagents, it is clear that either of the liquid reagent stands flooded over the surface of the porous carbon mass.

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Canadian Patent No. 81484 and its reference also disclose the advantages of polysulfide cooking, and in particular discloses an adsorption process for preparing a polysulfide cooking liquid. wherein the hydrogen sulfide gas is adsorbed on activated carbon in the presence of air or oxygen, wherein the hydrogen sulfide is oxidized to elemental sulfur which deposits on the carbon. As soon as the carbon is saturated with sulfur, the sulfur is removed by extracting it with an alkaline solution. The best results are found to be obtained when the hydrogen sulfide is saturated with water vapor before it comes into contact with the carbon and the sulfur formed is removed by base extraction to leave a small base residue to neutralize the sulfuric acid formed during the reaction. ** U.S. Patent No. 3,470,061 describes the preparation of polysulfide using insoluble manganese oxide compounds which act as oxidizing agents and which are regenerated after use by heating them in air to elevate the manganese oxidizing agent to a subsequent higher oxidation state. The latter patent also describes the disadvantages of the methods i described in U.S. Patent No. 3,216,887 and U.S. Patent Nos. 3,210,235 and 2,944,928 described above. ^

It is known from the catalysis technique that certain finely divided Ή substances increase the reaction rate. For example, finely divided nickel and cobalt have been used as catalysts in the hydrogenation of vegetable oils. <

It is mentioned that improvements have been obtained using thin films or. . . . . . flakes that remain better dispersed than finely divided powders (see, e.g., U.S. Patent No. 1,083,930). * j

U.S. Patent No. 1,146,363 discloses the use of granular carbon as a catalyst or detergent, wherein the carbon is in a column or percolate in which liquid is drained through a mattress formed by Huli granules. A

U.S. Patent No. 2,365,729 discloses the oxidation of an acidic solution of ferrous sulfate to ferrous sulfate in which granular activated carbon containing absorbed air or oxygen is used as a catalyst. * The carbon is suspended in the liquid and the oxidizing agent is bubbled through the suspension or the oxidizing agent is decomposed through the liquid by a carbon diffuser or the liquid and the oxidizing agent are fed downstream through the sintered tower or column. ^

The advantages of treating a lignocellulosic material with polysulfide are well known in the art. Today, there is at least one cellulose mill using polysulfide cooking, in which sulfur is added to sodium sulfide to form a polysulfide.

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.-4 “57244. The added excess sulfur is lost from the chemical recovery process. In said plant using polysulfide cooking, the addition of elemental sulfur in an amount of 2.2% yields 3 “**% i each calculated on dry wood chips.

It is an object of the present invention to provide a simple and efficient polysulfide producing system and thus to meet a need in the pulp industry by providing a polysulfide producing and polysulfide recovering system suitable for current sulphate cooking and recovery methods and equipment. The invention is characterized in that a part of the initially hydrophilic surface of the catalyst is made hydrophobic by treatment with a non-catalytic hydrophobic substance, so that the catalyst and the hydrophobic substance do not completely enclose each other.

According to the present invention, sodium polysulfide and sodium hydroxide are prepared by a reduction-oxidation process in which sodium sulfide or sodium hydrogen sulfide in aqueous solution is oxidized in the presence of a solid electron-conducting substance. The oxidizing agent is oxygen, air, or a mixture of oxygen with other gases, and the oxidizing agent is an aqueous solution of sulfide or hydrogen sulfide. The effect of an electron-conducting substance that is chemically relatively inert with respect to both the oxidizing agent and the oxidizing agent is probably based on deriving from electron-contacting reducing agent molecules or ion-contacting oxidizing agent molecules or ions, thereby accelerating the transfer of electrons involved in the reaction. Unlike known electrochemical devices, e.g., electrolysis or fuel cells in which the anode and cathode are separated by barriers or membranes and in which oxidation occurs at one electrode and reduction at the other, in the present invention oxidation and reduction reactions occur side by side .

Reactions in which sulfide is oxidized are known to tend to form primarily thiosulfate over polysulfide, especially if the substance to be oxidized is strongly basic. The new redox system of the present invention, on the other hand, primarily produces polysulfide, with minimal thiosulfate formation. According to the invention, this is achieved by contacting the oxidizing agent and the oxidizing agent simultaneously with the electron-conducting agent and with each other, but minimizing the contact of the oxidizing agent with the oxidizing agent except where both are in contact with the electron-conducting agent. In such devices according to the invention, the oxidizing agent and the oxidizing agent form an interface to which interface. 57244

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the electron-conducting substance is arranged and kept in simultaneous contact with both the reducing agent and the oxidizing agent.

An important feature of the present invention is that the electron-conducting solid is prevented from coming into exclusive contact with the liquid reagent, i. with an oxidizing agent. Likewise, the electron-conducting solid must not be in exclusive contact with the gaseous reagent, i. with an oxidizing agent. As used in this specification, the phrase "flushed" means that the electron-conducting substance is in exclusive contact with either an oxidizing agent or a bapetephen scavenger. If the electron-conducting substance of the invention is rinsed, the preferred polysulfide-forming reactions cease for all practical purposes.

The observations obtained in catalysis and electrochemistry can be applied to some extent to the new findings of the invention.

If, for example, the electron-conducting substance according to the invention is considered as an electrode, even though no electrical wires are connected to it for supplying or removing electric current, both oxidation and reduction take place with the same "electrode", i. one organ acts as both an anode and a cathode and both the oxidation product and the reduction product are generated by the same "electrode member". Although such an element could be characterized as a mixed potential electrode, the kinetics of the device according to the invention are not understood or are not sufficiently defined to explain the reaction mechanism exhaustively. Given the solid nature of the conductive material, it also appears that elements of heterogeneous catalysis would be present, since the purpose of the present system is to increase the rate of polysulfide-producing reactions substantially higher than is possible in the absence of a solid electron-conducting material. Characterization by a phrase such as heterogeneous catalysis also does not provide an exhaustive explanation of the reaction mechanism.

Regardless of whether the description of the reaction mechanism is based on catalysis, electrochemistry, or some combination of data branches, the following general rules applicable to the present invention are derived: (a) the oxidizing agent and the oxidizing agent must be able to form an interface or boundary; (b) electron conducting must be avoided; (c) both the oxidizing agent and the oxidizing agent must be in contact with each other and with the electron-conducting substance; and (d) mixing of the oxidizing agent and the oxidizing agent outside the location or zone of the electron-conducting substance must be avoided.

The method and apparatus of the present invention are essentially a new idea and procedure for preparing chemical substances by a reduction-oxidation reaction from reagents containing chemical elements of the desired product but under valence conditions different from the desired product. In this new method, the gaseous oxidizing agent and the fluid oxidizing agent are brought into contact in a controlled manner primarily at the interface with the electron-conducting solid, the latter limited contact being an integral part of the device. This controlled contact is completely different from mixing the reagents as gas bubbles in the liquid, e.g. with a disperser, and the reaction is carried out at the point of contact between the oxidizing agent, the oxidizing agent and the electron-conducting solid. For simplicity, the phrase below has been used to describe the method and its essential elements.

"Contactacogen" means an electron-conducting solid that forms the location of the interface between the oxidizing agent and the oxidizing agent and must be contacted simultaneously to effect the desired reaction.

Of particular interest is the fact that the present invention provides rare advantages in the preparation of polysulfides for use in the treatment of lignocellulosic materials. This rare advantage is due to the fact that polysulfide can be easily and continuously prepared under ambient conditions, although higher pressures and higher temperatures below the decomposition temperature of reagents or products can be used and polysulfide is formed simultaneously with sodium hydroxide without the need to regenerate the oxidant.

It is therefore a primary object of the present invention to provide a method and apparatus for preparing a polysulfide so that as little thiosulfate as possible is formed simultaneously, which comprises a completely new idea and procedure for the redox process.

It is also intended to prepare the polysulfide in batches or continuously, by a reaction in which the oxidizing agent is a gas and the oxidizing agent is an aqueous solution and in which both the oxidizing agent and the oxidizing agent are brought into interfacial contact with each other and simultaneously with an electron conducting solid.

It is a further object of the invention to provide a relatively simple apparatus for producing a polysulphide by a reaction in which an electron-conducting substance, i. contactogen, is kept in an unwashed state but in contact with both the oxidizing agent and the oxidizing agent, the latter being in contact with each other substantially only in the zone or point where they contact the contactogen.

The invention provides a system for producing a polysulfide for use in the cooking of lignocellulosic materials, in which both polysulfide and sodium hydroxide are produced.

It is therefore an object of the present invention to provide a process and apparatus for producing polysulfide and sodium hydroxide by a reaction in which these reaction products are prepared by the word organ without the need for membranes and barriers used in electrochemical processes.

The invention will be described in more detail below with reference to the accompanying drawings in which Fig. 1 shows a schematic view of a device according to the present invention, Fig. 2 shows a schematic view of a device according to the invention with two product-producing zones separated, Fig. 3 is a simplified view of a liquid-repellent device Fig. 4 is a schematic view of a continuous device according to the invention in which the contactogen is held at the interface between the oxidizing agent and the oxidizing agent, Fig. 5 is a schematic view of another continuous device according to the invention using several shelves and in which the contacting agent floats on the surface of the substance, Fig. 6 is a section along the line 6-6 in Fig. 5> Fig. 7 is a schematic view of a closed tower device according to the invention, parts of which have been cut away from it. to show the parent parts, Fig. 8 is an enlarged fragmentary view taken along line 8-8 in Fig. 7, Fig. 9 is an enlarged fragmentary view taken along line 9-9 in Fig. 7, and Fig. 57244

In the case of sodium sulfide, the reduction-oxidation system according to the invention comprises the following reactions:

Oxidation S = -> S ° + 2e (1)

Reduction 2H20 + 02 + 4e - »non" (2)

Combined with .2Na2S + 2H2O + 02 -> 2S + 4 NaOH (3) In this case, elemental sulfur combines with sodium sulphide to form Na2Sx, the latter being a polysulphide where x is more than 1 and not more than 4.5. However, these substances can also react in the following way: 2Na2S2 + 302 -> 2Na2S205 (4) 2Na2S + 202 + H2O -► Na2S205 + 2NaOH (5)

In the case of polysulphides used in the treatment of lignocellulosic substances, the amount of thiosulphate is preferably kept as low as possible and, if possible, its formation is prevented. Thiosulfate is not an effective cooking chemical in alkali ketone and forms an unwanted load in the recovery system.

In the case of sodium hydrogen sulphide, which can be prepared by absorbing hydrogen sulphide gas in an alkaline solution, the reactions are, for example, as follows: H2S + NaOH -> NaHS + H2O (6) 2NaHS + O2 - * 2S + 2 NaOH (7)

The three essential components of the system according to the invention are an oxidizing agent, an oxidizing agent and a contactogen. The oxidizing agent can be any gas that contains elemental oxygen, such as air, pure oxygen, or mixtures of oxygen with small amounts of chlorine or the like, but the amount of such gases, such as ozone, must be limited if they decompose or tarnish an electron-conducting solid. The oxidizing agent is an aqueous solution of sodium sulfide or sodium hydrogen sulfide and also forms an ion-conducting phase, although this phase is not believed to form as significant a factor as in electrochemical fuel cell or electrolysis systems. The oxidizing agent and the oxidizing agent are also characterized by the formation of an interface or boundary when brought into contact with each other.

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Electron conducting substance, i.e. the contactogen of the invention is a solid that is substantially inert with respect to the oxidizing agent, reducing agent and products in the sense that it is not chemically exposed to or reacts with them. A material with a high surface area / weight ratio is preferred because it provides high interfacial contact. The substance must have a resistivity such that it allows the transfer of electrons involved in the reaction. Materials having a resistivity of less than about 10 ohm-cm may be used, although the agent preferably has a resistivity of 10 ohm-cm or less.

To initiate and control the reaction of the invention, the oxidizing agent and the oxidizing agent are contacted with each other and the contactor and are maintained relative to each other such that the reactants contact each other substantially only in the same zone where they simultaneously contact the contactogen. An important feature of this invention is that the contacogen is prevented from entering either. to rinse the reactant. If the liquid oxidizing agent flushes the contactogen, the liquid film significantly slows down the diffusion rate of the oxidant to the contactogen surface. Likewise, if the oxidizing agent flushes the contactogen, the oxidizing agent is prevented from reaching the surface of the contactogen within the meaning of the invention. When operating in the unwashed state, as described above, it has been found that thiosulfate formation can be minimized, even eliminated. This is particularly significant in view of the prior art and the fact that strongly basic sulfide solutions are not easily oxidized by air, with oxidation leading to thiosulfate rather than polysulfide. The invention thus relates to a controlled oxidation in which the sulphide is primarily oxidized to sulfur and not to thiosulphate, thus providing a reaction product which, as far as the sulphide reaction is concerned, is primarily polysulphide.

Because the reaction zone contains gas, liquid, and contactogen, the contactogen must be in contact with the gas and moistened with the liquid, but not flushed by either. In this context, wetting means that the contact angle between the contactogen and the liquid is low, e.g. less than about 90 ° and almost zero. If the contact angle is large, e.g. greater than about 90 ° and almost 180 °, the liquid tends to withdraw from the surface of the contactogen and the contactogen surface is in fact substantially in contact only with the gas, i. flushed with gas. When, on the other hand, the surface of the contactogen is well moistened with a liquid, i.e. the contact angle between the contactogen surface and the liquid is almost zero, the liquid tends to cover the surface of the contactogen and the contactogen surface is in fact substantially in contact only with the liquid, i. flushed with liquid. One method of preventing liquid rinsing is to perform a treatment on the contactogen called wetproofing. In this case, a smaller part of the inert substance is added to the contactogen, which is not wetted by the aqueous solution, i.e. the contact angle between the inert additive and the liquid is greater than about 90 °.

When porous substances are used as the contactogen, it is clear that the oxidizing gas must not be forced through the pores of the contactogen in the sense that the porous member is used as a diffuser to form small oxidant gas bubbles in contact with the liquid.

Typical useful electron-conducting materials include carbon, activated carbon, platinum-plated asbestos, nickel or carbon or activated carbon containing inclusions such as nickel, iron, cobalt, silver, platinum, palladium, manganese oxides (e.g., manganese dioxide) and manganese sulfide, manganese , nickel oxide, nickel sulphide and cobalt sulphide or mixtures thereof. Of the above materials, carbon and activated carbon appear to give the best possible result, due to the relatively high surface area / weight ratio and the ease with which inclusions of metals and metal compounds can be added to the material, as well as the degree of fineness to which the carbon can be introduced. In addition, it is an readily available substance that is available in a wide variety of particle sizes and areas. Coals from different sources often result in different reaction rates. These variations can be easily determined by simple methods. Typical carbons to be used in accordance with the present invention include carbon black, carbon black, channel carbon or by known methods from various sources, e.g. The particle size can range from 9 millimicrons to a relatively large size, e.g., 25 millimeters or more, and carbon is usually marketed as a mixture of different particle sizes. The surface of the carbonaceous substance 2. ? . .

the area can range from 3 m per gram to more than 950 m per gram, characterized by gas absorption using the 3ET method.

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The carbon can be adapted to various physical forms, e.g., a porous nickel substrate having platinum powder coated with powdered carbon and a liquid repellent, all fitted to one side of the nickel substrate as described in "Fuel Cells", Prentice Hall, 1969, pages 402-40. a water-repellent porous carbon plate or tube or a mass of water-repellent carbon granules or powder floating on the surface of the aqueous solution to be oxidised or a mattress of contaminant particles having a thickness greater than the capillary rise of the aqueous solution of the oxidizing agent, so as to prevent leaching; in contact with the surface of an aqueous solution of the oxidizing agent.

Carbon can be made water repellent as follows:

Polytetrafluoroethylene (PTFE) in the form of an emulsion is mixed with the carbon in the partial form in an amount of between 0.1 and 100% based on the solid carbon. The mixture is heated to remove the PTFE excipient and dispersant. In another method, carbon in particulate form is treated at a ratio of 1 g of linear polyethylene per 10 g of carbon. The polyethylene is dissolved in a ratio of 1 g of polyethylene per 100 g of hot toluene and poured onto carbon. After the treatment, the carbon is heated at about 105 ° C to evaporate the toluene. The particles are not uniformly water repellent, but most are repellent enough to float from several hours to several days.

Using the method described above, the carbon in the partial form can also be rendered liquid-repellent by polystyrene, fluorocarbon resins, polyethylene emulsions, silicones or other hydrophobic substances by any suitable method which avoids complete encapsulation in reagents or their products impermeable to hydroforms. Other useful materials include chlorotrifluoroethylene, prepolymerized silicone oils and supercoil silicone grease.

In another method, a chlorinated paraxylene dimer is sublimed in a vacuum chamber and the vapors are deposited on materials such as carbon in the form and porous sintered nickel to form poly (chloro-p-xylylene), known as parylene.

In the case of substances such as finely divided platinum in matrix asbestos, impregnation is achieved by using a 1% toluene solution of polyethylene, moistening the matrix asbestos with a solution of 12 57244, removing excess liquid and then drying in an oven to evaporate the toluene.

In another example, 1 / 2-2 g of paraffin wax per 10 g of carbon in particulate form is used. The paraffin is dissolved in a solvent such as hexane or toluene, carbon is added to the mixture, heated and then the solvent is evaporated. Cetyl alcohol can also be used and applied in the same manner. It is also possible to use paratoluenesulphonamide, polydichlorotrifluoroethylene or octa-decylamine, which are applied by mixing them with carbon and heating the mixture to cause the treatment agent to adhere to the carbon. Each of the above substances functions satisfactorily in the new systems, as shown by the formation of polysulfide, which is visibly detectable.

The carbon in the partial form can be bound by a carboxylated cysteine butadiene latex used as a dispersion containing 5 g of 25 solids per 10 g of carbon. The substance obtained is a plate which can be supported at the interface between sodium sulphide solution and air and the reaction becomes visible when a yellow color characteristic of polysulphide appears. In another example, polyethylene was dissolved in toluene using 5 E per 10 g of granular carbon and the toluene was removed by floating the mixture over boiling water. The result was a bound product that was sufficiently porous to permeate an oxygen-containing gas and sufficiently liquid-repellent to float.

In Figure 1, which shows a preferred embodiment of the apparatus of the present invention, the polypropylene container 10 is provided with a supply pipe 12 and an outlet pipe 14 for supplying a solution of the oxidizing agent and for removing the reaction products. Inside the container, the contact gene 15 forms its second wall and the contact gene may be a porous nickel substrate, platinum black and a carbon powder and liquid repellent may be deposited on the side of the substrate in contact with the reducing agent. The tank 10 also has a supply pipe 16 for the gaseous oxidant and an outlet pipe 17 for it. The gaseous oxidant initially contacts the nickel side of the contactor 15.

During use, a two-molar solution of sodium sulfide was recycled from the tank (not shown) through the solution space 19 by means of a pump (not shown) and then back to the same tank. The solution was maintained at 50 ° C and a gaseous oxidizing agent, e.g., oxygen, was introduced into the gas space from 20 pressure cylinders, using a water column to apply pressure to the gas in the gas space by a 40-6 mm high water column. Excess and unreacted oxygen was removed through the outlet pipe 17. The free surface of the contact gene was 48.5 cm. After running for 65 hours, 72.2 g of polysulfide-sulfur and 252 g of sodium hydroxide were formed. No thiosulfate was formed. This indicates that the sulfide has reacted at $ 50 to sulfur.

In another embodiment of the invention, the contactogen was a 6.4 mm thick porous carbon electrode made liquid repellent as described. The operating conditions were as described above and after 23 hours of running 40.6 g of sulfur had been formed as well as 112 g of sodium hydroxide and 5.7 g of thiosulfate. This means that $ 68 of sulfide has reacted to sulfur and $ 4 to thiosulfate.

It is obvious that the device according to Fig. 1 can be set so that the contactogen 15 is arranged horizontally above the sulphide solution only by turning the entire device 90 °. In this embodiment, the liquid surface of the solution space is maintained so that the solution contacts the surface of the carbon but does not flush the entire member 15. Thus adapted, it may not be necessary to use a pressure system for the oxidant maintained in contact with the member 15.

In the embodiment shown in Figure 2, in which the same reference numerals have been used in appropriate places, an alternative embodiment is shown in which two separate contactogen members 15 and 15a form opposite walls of the container 10. The space between them forms a solution space 19, whereby the solution of the oxidizing agent is fed through the feed pipe 12 and the reaction products are removed through the outlet pipe 14. A member 15a of the type described above is provided with an oxidizing agent supply and discharge pipe 16a and 17a. After four hours of use, 26.6 g of sulfur and 83.6 g of sodium hydroxide were formed as described for the device according to Figure 1. No thiosulfate was formed. In both cases, however, the appearance of a yellow color indicated the formation of sulfur, and the color gradually darkened as more sulfur was formed and dissolved in sodium sulfide to form polysulfide. The nature of the reaction products was confirmed by analysis.

Figure 3 shows a simple apparatus for applying the present invention on a batch basis and for evaluating contactogens in a container 25 containing a reducing agent 26. The contactogen 29 is in the form of particles floating on the surface of the reducing agent and simultaneously in contact with an oxidizing gas, e.g.

In one example, sodium sulfide solution was fed to the tank and carbon removed from the surface of the fuel cell electrode was used as the contactogen. The activity manifested itself as the appearance of a yellow color and heat generated at the interface. Analysis of the carbon showed the presence of fluorocarbon resin, copper, nickel, cobalt and iron, the latter metals in trace amounts. The solution of the oxidizing agent originally contained 62 g of sulfide sulfur per liter and 169 g of total alkali per liter expressed as sodium hydroxide. A small amount of thiosulfate was also present. This solution was allowed to stand without stirring at room temperature for 3 days with the carbon floating on the surface of the oxidizing agent and then analyzed. The result was 9 g of sulphide sulfur per liter, 30.7 g of polysulfide sulfur per liter, 34.5 g of sulfur per liter in the form of thiosulfate (S 2 O 3). The total alkali was 142.8 g per liter calculated as sodium hydroxide. For the purposes of this invention, it is defined that each polysulfide ion, Sx, consists of one atom of sulfide sulfur, i. S-, and x-1 atomic polysulfide sulfur, i.e. S °,. The value of factor X is calculated from the amounts of sulphide sulfur and poly- * 1 * r n sulphide sulfur by the formula X = S + S °, i.e. sulphide sulfur plus S = the ratio of polysulphide sulfur to sulphide sulfur.

A second sample of the same sulfide solution was used, and after one hour and 15 minutes at room temperature, the analysis was as follows: 47.2 g of sulfide sulfur per liter, 11.2 g of polysulfide sulfur per liter, and no thiosulfate (S 2 O-). The total alkali was 16.6 g per liter as sodium hydroxide. After four hours, the analysis was 29.3 g of sulfide sulfur per liter, 21.1 g of polysulfide sulfur per liter and no thiosulfate (S 2 O 2 =). The total alkali was 157.2 g per liter expressed as sodium hydroxide.

The above results are summarized in the table below:

Time * S = * S ° xl * S2 ° 3 = X value 1.25 hours 47.2 11.2 0.0 1.24 4.0 hours 29.3 21.1 0.0 1.75 72.0 hours 9, 0 30.7 34.5 4.23

The water-exposed quality of the activated carbon was made water-skinning using polyethylene as described above. The floating mattress system of Figure 3 was used with the following values:

Time XS = * sx-1 * s2 ° 3 = X-value 5 hours 56.1 5.6 0.0 1.10 24 tur.jö 40.3 22.2 0.0 1.55 * concentrations, in grams of sulfur / liter 15 57244 Using carbon-sealed cottons in the partial form, it was made that a sufficiently high water-repellent degree would prevent rinsing and maintain the continuous production of polysulfide even under hydrostatic pressure. Carbon comparisons performed in this way showed that virtually no polysulfide was formed on carbon that had not been made liquid-repellent, whereas large amounts of thiosulfate were formed instead. The basic method used 100 g of 2-molar sodium sulfide solution in a 25.4 mm diameter glass column with a glass separator at the bottom. Air was bubbled into the column at a rate of 250 cm 2 per minute for 2 hours. The following values were obtained:

Test Contactcogen Water repellent s S xi S2 ° 3 x * value 1 none - 53.8 0.0 10.2 g / l 1.00 2 carbon none 51.0 1.1 11.9 g / l 1 .02 3 carbon 2% PTFE 20.2 34.2 9.6 g / 1.69 4 carbon 20% PTFE 48.4 15.6 0 1.32 These values indicate that the best possible operation of the system of the present invention requires keeping the contactogen at the interface between the gaseous oxidant and the liquid oxidizing agent and keeping the oxidant in contact with the contactogen. with an unwashed surface.

Whatever the explanation for these unusual results, it is clear that rinsing the surface of the contactogen substantially reduces the oxidation rate. Furthermore, the results are unique in that such oxidation, which occurs when the contactogen surface is flushed, raises the degree of sulfur oxidation to too high a thiosulfate, whereas the desired reaction with a fast flushed water-repellent contactogen only raises the sulfur oxidation state to polysulfide only. One explanation for this behavior in a column structure using a liquid-non-repellent material in which polysulfide formation can be ignored and thiosulfate formation is higher may be that there is a direct reaction between the oxidizing agent and the oxidizing agent in which the contactogen is not involved.

It has been found that when the sulfide solution is kept in the vicinity of the oxidizing site for too long, too much thiosulfate is obtained as an oxidation product, the amount of which increases with increasing reaction time. In the column structure, the reaction time can be adjusted to the throughput concentrations of the sulfide solution, in grams of sulfur / liter at 57244, the lower the delay time, the shorter the reaction time. Analyzes under the effluents from the bottom of a particulate column through which air is fed upstream upwards show that the throughput of a given contactogen must be kept above the value at which thiosulphate is formed. The reference values below show that unless the contactogen is made water repellent, the oxidation rate is relatively low.

Feed rate χς = χςο Χς, n = cm3 / hour x-1 2 3 10¾: 11a PTFE. water repellent carbon 22 1.9 8.5 50.5 45 3.7 11.8 42.8 116 9.9 31.8 21.7 1.88 25.4 32, 8 0, 0 256 31.8 26, 8 0.0 370 36.6 17.9 3.2

The same carbon in the raw state 40 57, 3 1.0 2.6 130 63.2 0.5 0, 0 159 58.9 0.8 2, 6 326 63.4 1.0 0.0

The amount of impregnant with which the contactogen is to be treated can vary from less than H to more than 99¾ by weight of contactogens. Smaller or larger amounts of impregnant do not appear to serve any useful purpose because the surface area of the available contactogen of one fluid phase is greatly reduced relative to that of the other phase exposed. The exact amount of impregnating agent is best determined experimentally for the particular contactogen used in a particular device, depending on the practical results desired.

By way of example, the amount of PTFE used to treat activated carbon was varied, with several water-repellent carbons thus prepared being sintered into glass columns with a diameter of 4.8 cm to a depth of 40 cm. A sodium sulfide solution having a concentration of about 2 molar was drained downwards through the columns at a controlled and measured volume rate and a large chemical excess of air was fed upstream at a constant volume rate of 17 57244 grams of sulfur / liter. In different experiments, the flow rate of the sulfide solution was adjusted to different magnitudes, and after the treatment was continued long enough to reach a steady state, samples of the effluent solution were collected and analyzed. The table below shows the analytical results of these experiments at the corresponding values of the amount of water-repellent PTFE on carbon and the delay time, the latter being inversely proportional to the feed rate, corresponding in minutes in these experiments to ^ 3, ^ 40 divided by emes per hour.

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• H rH C Ή VO m • Η Ο · Η <D - = r in> x ε p 19 57244 Looking at this table, it is observed that if the minimum possible delay time in the column is the primary criterion and the maximum possible polysulfide sulfur yield the secondary criterion gives either 2, 5 or 10 # water-repellent PTFE on carbon with the largest oiir — I did the same results. If, on the other hand, the highest possible yield of polysulfide sulfur is the primary criterion and the lowest possible yield of thiosulfate sulfur is the second-class criterion, a 10 # amount of water-repellent PTFE on carbon gives the best results in these experiments. In two experiments, a column using activated carbon without a water repellent was used, and the above results show that the yield of oxidized sulfur products was significantly reduced compared to the presence of PTFE in amounts of 2.5 or 10 # on carbon.

A simple device for applying the present invention on a batch basis and for evaluating contactogens is shown in Figure 3> where the reservoir 25 contains a sulfide solution 26. The contagogen 29 is in the form of particles floating on the surface of the sulfide solution supported by it and in simultaneous contact with the gaseous oxidant. The device specifically shown in Figure 3 can be used with a contactogen supported at the interface, and a conventional effective means of accomplishing this is to make the contactogen water-repellent, e.g., water-repellent particulate carbon. In this way, a floating mattress structure is provided. · The contactogen is held at the interface formed between the two reagents.

The container 30 shown in the figure is provided with an inlet pipe 31 and an outlet pipe 33 for oxidizing agent solution 32 to remove reaction products and unreacted oxidizing agent. Inside the container 30 there is a mesh element 3 fitted to the liquid surface of the oxidizing agent 32 in the container 30. contacting the underside of the mesh 3 ** and dimensioning the thickness of the mattress of the contacting agent 35 so that its vertical height is greater than the capillary rise of the oxidizing agent solution to prevent the oxidizing agent from rinsing the contacting agent, the contacting agent free surface 36 is continuously exposed to the oxidizing agent (air) floating mattress. In the device of Figure 4, the contact gene 35 may be, for example, a porous carbon plate consisting of bound porous carbon particles supported either by a net or some other sounding device. Depending on the size, cross-section and strength of the plate, it can be made self-supporting, thus eliminating the use of support nets and other structures. As with the devices described above, this device ensures that any oxidizing agent that contacts the solution of the oxidizing agent also contacts the contactogen.

Another embodiment of the device is shown in Figures 5 and 6, in which a plurality of vertically stacked troughs 46 are supported on the device 45 and are spaced apart by members 47. In the embodiment shown, there are four trays, but it will be appreciated that more or fewer trays may be used. Each trough has a plurality of spaced apart separating elements 48 extending from the second wall 49 of the trough. through the feed pipe 55 and flows serpentinely into the trough outlet line 56 due to the arrangement of the separating elements 48 and 53, which allows the solution of the oxidizing agent to flow mainly into the lower trough. In this way, the substance to be oxidized passes from one trough to the next and is finally removed through the outlet pipe 57.

The reaction is carried out in the presence of a contactogen, which may be, for example, a polytetrafluoroethylene (PTFE) water-repellent particulate carbon floating on the surface of the oxidizing agent in approximately the same manner as described in connection with Figure 3. However, the device of Figures 5 and 6 is a continuous system in which fresh sulphide solution is fed into the inlet pipe 55 and removed from the outlet pipe 57. remains in place. The oxidizing agent is the air circulating between the troughs.

In a typical test, 0.6 x 1.2 m series-connected troughs were used continuously for 5 1/2 hours. The feed rate was 430-490 cm of aqueous sodium sulfide per minute containing about 64.6 g of sulfide per liter expressed as sulfur. The feed temperature was about 55 ° C and the concentration, percentage reaction and X-value of the effluent from each tray were analyzed. The results are shown in the following table: 21 57244

Tray XS ~ * Sx-1 * S2 ° 3 ^ reaction ratexx X value

Input 64.6 - 0 1.00 1 59.0 5.1 0 8.2 1.09 2 51.0 12.5 0 19.4 1.2¾ 3 M3.9 19.9 0 31.0 1, 45 4 34.6 28.2 0 44.8 l, 8l 5 31.1 33.0 0 51.5 2.06 6 No values were taken 7 27.2 36.2 0 57.0 2.33 8 25, 3 37.2 0 59.5 2.47

In the second set of tests, a feed rate of 400 cm 2 / min was used. at a feed temperature of 49 ° C, the unit being used continuously for 28 hours. The values were compiled as described above and were as follows:

Tray XS = XS °, xS ,, 0ä # reaction ratexx X-value X-l 2 5

Input 31.9 - 0 1.00 1 25.8 5.9 0 18.7 1.23 2 20.4 10.9 0 34.6 1.53 3 17.0 14.2 0 45.6 1, 84 4 14.9 15.9 0 51.5 2.06 5 13.3 16.5 0 55.3 2.24 6 12.3 18.4 0 59.8 2.49 7 11.5 19.1 0 62.4 2.65 8 10, 7 19, 9 0 65.0 2.85 These values are significant due to the large amount of polysulfide formed in the absence of thiosulfate using a device of the type shown in Figures 5 and 6. It is also significant that the generator 45 operated continuously for an extended period of time without any obvious decrease in contactogen activity and thus regeneration became unnecessary.

Figures 7 ~ 9 show a closed tower device 75 with a plurality of vertically stacked trough elements 76, four of which are shown, although more or less voidaan Concentrations, in grams of sulfur / liter

Cumulative amount of sulfide reacted to polysulfide in percent 22 57244 if desired. This device each has a trough made of polypropylene, stainless steel or other suitable material with a plurality of spaced apart separating elements 77 extending from the second end wall 73 and terminating a short distance from the opposite end wall 79. terminating a short distance from the wall 78. Separation elements 77 and 80 form flow channels for the reducing agent and the oxidizing agent. The oxidizing agent is fed through the feed pipe 8l in the lid 82 and the reducing agent is likewise fed through the feed pipe 84 in the lid. The sulfide solution supply chamber 85 is formed by baffles 86 and 87 extending from an adjacent sidewall to an adjacent separator 80. The baffles terminate a short distance from the lid 82 to provide a pathway for the oxidant . Adjacent to the sulfide solution supply chamber is an oxidant supply chamber 88 bounded by a septum 86 and an end wall 79.

The unreacted oxidizing agent and product and some residual oxidizing agent are removed from the outlet tube 89 in a chamber 85a formed by partitions 86a and 87a corresponding in structure to the partitions 86 and 87. The top of the outlet tube 89 extends above the bottom of the partition so that the contact gene 90 in the form of carbon in the water-repellent partial form cannot flow from one tray to the next. The oxidizing agent passes over the tops of the partitions 86a and 87a through the oxidizing agent removal chamber 88a and the outlet pipe 91 to the next lower trough. For simplicity, each trough is substantially similar in structure, with the passageways 89a and 91a at the feed end of the trough being blocked or closed as shown in Figure 8. With liquid and gas. thus, both the oxidizing agent and the oxidizing agent flow in the opposite direction to the above trough and exit through chambers whose location and structure correspond to chambers 85a and 88a. In the last trough, unused oxidant, if any, and residual gases are removed from the tower outlet 92, while a solution containing unreacted substance and products is removed from the trough outlet 93 · 57244 23

The lid 82 is thus fixed to the uppermost tray by sealing elements so that a flow channel is formed between the separating elements and the walls, as shown in Fig. 7. The bottom of the top trough forms the lid of the trough below it, whereby the top trough is provided with a separate base. The trays are sealed with sealing elements 95, which may be of different shapes. In the form shown in Figures 7-9, the sealing elements are resilient members attached to the top of the separating elements 77 and 80 and to the top of the side and end walls of each trough. In this way, the oxidant feed rate can be forcibly controlled and the system can be pressurized if desired.

Using a tower device of the type shown in Figures 7-9, oxidizing air was fed at a rate of 44 l / min, while an aqueous solution of sodium sulfide to be treated with 61.5 g of sulfide sulfur per liter was fed at a rate of 400 cm 2 / min and water-repellent carbon in the form of PTFE. was used as a contactogen and floated on the surface of the oxidizing agent solution. The values were as follows:

Tray Feed- Reaction temperature xs = XqO x „0 = degree% X-value oc x-1 23

Feed 61.5 g / 1 1 59 62.1 g / 1 0 0 0 1.0 2 58 60.5 g / 1 0 0 0 1.0 3 64 57.4 g / 1 1.6 0 3.0 1.03 4 84 52.5 g / 1 3.5 0 6.5 1.07 5 91 45.1 g / 1 11.2 0 20.0 1.25 6 89 28.2 g / 1 28.5 0 50.2 2.01

The oxidizing agent was about 21% oxygen-containing air, and the oxygen content of the gas from the exhaust pipe 93 was found to be about $ 9. The delay time was about 90 min for six trays or 15 min for each tray. The total running time was about 6 hours of continuous use.

The closed device of Figures 7-9 is preferred in the practice of this invention. The heat generated during the exothermic reaction can be used, for example, as a low heat source by using a heat exchanger assembly connected to the tower. In addition, the reaction conditions and temperature can be controlled by adjusting the feed rates of the oxidizing agent and the oxidizing agent. Oxidant configurations can be adjusted. Countercurrent can be used if desired. Part of the tower can be χ Concentration, grams of sulfur / liter 2 “57244 ment can be used to increase the reaction rate using heat generated in other parts of the tower or with a separate source. Cooling of certain parts of the tower is possible if it is found to be advantageous. It is also clear that the tower may have some other shape.

Given that the reaction is exothermic, it is clear that if water repellents are used as the contactogen, the water repellent must be stable at the temperatures in question.

Other variables that affect the operation of the device shown in Figures 7-9 include oxidant concentration, feed rate, and rate, the rate of rejection of the carbon in the subform, or other contactogen. Since the amount of oxygen is greatly reduced when air is used as the oxidizing agent, the exhaust gas can be further treated using the system of the invention to provide a mixture of inert gas rich in nitrogen and oxygen deficient, although it will be appreciated that other systems may be used to remove residual oxygen. The exhaust gas can, for example, be passed through another device of the type according to Fig. 7. It is also possible to adjust the reaction conditions to enhance oxygen reduction rather than polysulfide formation.

The speed and / or efficiency of the device according to the invention can be increased by using inclusions and the like with contactpene. For example, inclusions of metals and metal compounds in the particulate carbon appear to increase the reaction rate compared to the rate of reaction without inclusions on the same carbon. The inclusions can be achieved as follows:

Cobalt sulfate was dissolved in water at a ratio of 0.5 P per 100 ml of water. The carbon in the partial form was added 10 per 100 ml of solution. The resulting mixture was heated to boiling point and then dried in an oven at 110 ° C. The solid was then treated with sodium hydroxide to precipitate insoluble cobalt, then the solids were precipitated and washed with 0.1 N sodium hydroxide. The carbon was then dissolved in sodium sulfide solution for one hour, filtered and washed with hot water three times and then dried again at 110 ° C.

Manganese (II) nitrate was dissolved in a slightly acidic solution in a ratio of 0.5 p per 100 ml of water acidified with 0.1 g of nitric acid. The post-treatment was the same as described for cobalt sulfate.

The method just described was used with the difference that the inclusion was derived from 57,524 ferrous sulfate dissolved in 0.1 N sulfuric acid.

Nickel sulfate, silver nitrate, and chloroplatinic acid were used separately and treated to form the inclusions described above.

All of these inclusions were found to increase the reaction rate compared to the reaction rate obtained without the inclusions.

The main advantage of the device according to the present invention is its use as a generator of polysulphide cooking liquid in the treatment of l-p; no-cellulosic substances such as wood and the like for the production of pulp. .

Claims (5)

A process for oxidizing a solution containing sodium sulfide or sodium hydrogen sulfide with an oxygen-containing gas to form a lignocellulosic substance alkali alcohol containing sodium polysulfide, contacting the aqueous solution and the oxidizing gas with a gas-liquid thereon the oxidation is a solid heterogeneous catalyst, which is chemically affected relatively little by reactants and reaction products, characterized in that a portion of the catalyst surface, which is initially hydrophilic, is made hydrophobic by treating it with a catalytic hydrophobic substance, in that the hydrophobic substance does not completely enclose the catalyst. Process according to claim 1, characterized in that the catalytic converter is koi, active koi, platinum asbestos or nickel, koi or active koi containing inclusions of nickel, iron, cobalt, Silver, platinum, palladium, manganese oxides, manganese sulphides, iron oxides, nickel oxides. , nickel sulfides, cobalt sulfides or a mixture thereof and of the hydrophobic agent being polystyrene, polytetrafluoroethylene, polyethylene, silicone, polyclorotrifluoroethylene, prepolymerized silicone oil, high vacuum silicone grease, poly (chloro-p-xylylate, paraffin, -leene or octadecylamine and its weight is 0.1-100% calculated by weight of the bullet. Process according to claim 2, characterized in that the solid catalytic particle is carbon. Apparatus for carrying out the process according to claim 1, characterized in (a) by a reaction chamber (10) for receiving the aqueous solution, b) by a solid catalytic substance (15) in the reaction chamber, the surface of which catalyst has parts which are in contact with the hydrophobic substance without being fully enclosed by this hydrophobic substance, while the oxidizing gas, oxidizable solution and reaction products chemically affect relatively small males on the solid catalytic agent;