Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B17/00—Sulfur; Compounds thereof
  • C01B17/22—Alkali metal sulfides or polysulfides
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B17/00—Sulfur; Compounds thereof
  • C01B17/22—Alkali metal sulfides or polysulfides
  • C01B17/34—Polysulfides of sodium or potassium
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
  • C09K5/08—Materials not undergoing a change of physical state when used
  • C09K5/10—Liquid materials
  • C09K5/12—Molten materials, i.e. materials solid at room temperature, e.g. metals or salts
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/10—Process efficiency
  • Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/10—Process efficiency
  • Y02P20/133—Renewable energy sources, e.g. sunlight

Definitions

• Liquids for transferring heat energy are used in a variety of fields of technology.
• mixtures of water and ethylene glycol carry waste heat from combustion into the radiator. Similar mixtures transport the heat from solar roof collectors into heat storage.
• they convert the heat from electric or fossil-heated heating systems to chemical reactors or out of them to cooling devices.
• liquids According to their requirement profile, a variety of liquids is used.
• the liquids should be liquid at room temperature or even lower temperatures and, above all, have low viscosities.
• water is out of the question, its vapor pressure would be too high. Therefore, up to 250 ° C hydrocarbons are used, which usually consist of aromatic and aliphatic molecular proportions.
• oligomeric siloxanes are used for higher temperatures.
• a new challenge for heat transfer fluids is thermal solar power plants, which generate large scale electrical energy. So far, such power plants were built with a total installed capacity of about 1000 megawatts.
• the solar radiation is focused via parabolic mirror grooves in the focal line of the mirror.
• There is a metal tube which is located in a glass tube to prevent heat loss, the space between the concentric tubes is evacuated. The metal tube is flowed through by a heat transfer fluid.
• a mixture of diphenyl ether and diphenyl is usually used here.
• the heat carrier is heated to a maximum of 380 to 400 ° C and thus operates a steam generator, in which water is evaporated. This steam drives a turbine, which in turn drives the generator like in a conventional power plant. Total efficiencies are achieved by 20 to 23 percent, based on the energy content of solar radiation.
• inorganic salt melts as a heat transfer fluid.
• Such molten salts are state of the art in processes that operate at high temperatures. With mixtures of potassium nitrate, sodium nitrate, the corresponding nitrites and optionally other cations such as lithium or calcium, working temperatures of up to 500 ° C. and crystallization temperatures down to 100 ° C. are achieved (US Pat. No. 7,588,694).
• nitrates As nitrates, they have a strong oxidizing effect on the metallic materials, preferably steels, at elevated temperatures, which limits their upper application temperature to the cited about 500 ° C. is. Second, the thermal stability of the nitrates is limited at higher temperatures. They decompose with the elimination of oxygen, and insoluble oxides are formed. Because of its crystalline melting point, its lowest application temperature is about 160 ° C. The addition of lithium or calcium salts achieves a further lowering of the melting point. However, the lithium salts cause greatly increased costs, the calcium content increases the
• Energy on a large scale depends on whether there is a heat transfer fluid that allows temperatures up to 650 ° C in continuous use, which has the lowest possible economically viable vapor pressure at this temperature, preferably below ten bar, which does not oxidatively attack the iron materials used, and which has the lowest possible melting point.
• the melting point of sulfur at just under 120 ° C is lower for use as a heat transfer fluid than that of molten salts, the boiling point of sulfur at 444 ° C in the right range, a decomposition is practically impossible.
• the vapor pressure of sulfur is ten bar, a pressure that is technically manageable.
• the viscosity of sulfur is only about 7 cPoise (7 mPas).
• the density of the liquid sulfur is in wide temperature ranges on average
• the ring-shaped sulfur molecules polymerize ring-opening to very long chains. While the viscosity is above the melting range by 7 mPas, it rises to 23 mPas at 160 ° C to reach maximum values around 100,000 mPas at temperatures in the range of 170 to 200 ° C.
• the polymerization of sulfur thus generally causes an increase in viscosity, whereby the normal purified sulfur in this temperature range is generally no longer eligible, is not well suited for use as heat transfer fluid.
• thermo energy hereinafter also referred to as "heat transfer medium / inventive heat storage medium"
• heat transfer medium a composition for transport and storage of thermal energy
• inventive heat storage medium containing sulfur and the disadvantages described above, for example, the higher vapor pressure at elevated temperatures and especially the viscosity increase , not showing.
• Melting point minima in the binary systems represent the compositions Na 2 S 3 with 235 ° C and K 2 S 3; 44 with 1 12 ° C, with Na 2 S 3 does not exist in the melt, but a mixture, mainly of Na 2 S 2 and Na 2 S 4 , is present.
• the lowest eutectic melting point in the (calculated) K-Na-S ternary system is a polysulfide of the composition
• K 2 S 4 decomposes under normal pressure at 620 ° C to K 2 S 3 and sulfur; K 2 S 3 decomposes at 780 ° C to K 2 S 2 and sulfur (US Patent 4,210,526).
• the areas with molar sulfur contents of S 2 to S 3 are particularly stable. If one looks at the phase diagrams of the binary systems, one finds for example for Na 2 S 2; 8 a melting point of 360 ° C, for K 2 S 2, 8 a melting point of 250 ° C and for the ternary polysulfide NaKS 2, 8 a melting point of about 270 ° C.
• the viscosity behavior of the polysulfides also tends to not concentrate on this class of compounds: Upon closer examination of the melts of alkali metal polysulfides was found that the alkali metal polysulfides at temperatures below 200 ° C have increased viscosities. Thus, sodium polysulfides of the formula Na 2 S 3 . 4 at 400 ° C a viscosity of 10 centipoise ("The Sodium Sulfur Battery", JL Sudworth and AR Tilley, Univ. Press 1985, pages 143-146, ISBN 0412-16490-6).
• This value doubles when the temperature is lowered by 50 ° C, ie to 20 cP at 350 ° C, 40 cP at 300 ° C, 160 cP at 200 ° C, 320 cP at 150 ° C and further extrapolated 640 cP, if the polysulfide would still be liquid at 100 ° C.
• the final value of 640 cP corresponds to about half the viscosity of glycerol at room temperature (1,480 cP). By comparison, the viscosity of water is around 1 cP, that of olive oil around 100 to 200 cP. Often the alkali polysulfides solidify glassy and form highly viscous glasses which slowly crystallize at room temperature for days.
• Me means the group of the following alkali metals of the Periodic Table of the Elements: lithium, sodium, potassium, rubidium and cesium.
• polysulfides of the formulas (Na 0 .5 to .o, 65Ko, 5 to 8 ⁇ , or (Na 0 , 6K 0 , 4 ) 2 S 2 , 6 .
• the alkali metal polysulfides according to the invention are obtainable by the following methods.
• very economical synthesis routes should be followed.
• concentrated aqueous solutions of the corresponding alkali metal hydrosulfides (MeHS) for example sodium hydrogen sulfide, NaHS or potassium hydrogen sulfide, KHS, which are obtained by introducing hydrogen sulfide into the aqueous hydroxide solutions of the corresponding alkali metals Me, were reacted with sulfur according to the general formula
• MeHS + zS> Me 2 S (z + i) + H 2 S (Me alkali metal, for example K, Na) with one equivalent of hydrogen sulphide escaping.
• This hydrogen sulfide can be recycled and used again for the preparation of the alkali hydrogen sulfides.
• the water of reaction and the water of dissolution were preferably distilled off rapidly with increasing the temperature up to 500 ° C., thus obtaining the alkali metal polysulfides according to the invention.
• water and hydrogen sulfide are usually present.
• water and hydrogen sulfide intervene in the reaction process and Probably causes other structures and / or molecular mass distributions than in anhydrous synthesis.
• inventive, economical process conditions undetectable, tightly bound small residues of water and / or hydrogen sulfide, hydrogen sulfides or Sulfanend phenomenon may possibly be responsible for the lowering of melting point and viscosity of the alkali metal polysulfides according to the invention.
• a further process for preparing the alkali metal polysulfides of the formula (I) according to the invention or their preferred embodiments described above is the reaction of alkali hydrogen sulfides with sulfur to form the alkali metal polysulfides according to the invention in concentrated aqueous solution and preferably their subsequent drainage by direct distillation of the water it is possible to prepare the alkali metal polysulfides according to the invention by reacting the alkali metal hydrogensulfides
• MeHS + MeOH ⁇ > Me 2 S + H 2 0 is reacted with alkali metal hydroxide to the alkali sulfides and the alkali metal sulfides are reacted with further sulfur to the polysulfides.
• Alkaline thiosulfates generally increase the melting temperature, increase the melt viscosity of the alkali metal polysulfides and decompose at elevated temperatures in different reaction routes to further salts ,
• the decomposition products of the thiosulfates are the sulfates of the alkali metals, which also generally have the disadvantageous properties of high melting temperature and viscosity as fractions in the polysulfide melt.
• the synthesis route according to the invention avoids this side reaction, there are usually no excess hydroxide ions in an increased concentration.
• alkali metal polysulfides it is possible to avoid the secondary reactions by reacting in the reaction of alkali metal hydrogen sulphide.
• a maximum of 0.9 moles of alkali metal hydroxide is used per mole of alkali metal hydrogen sulfide.
• the molar deficiency of alkali metal hydroxide then usually there is a mixture of sulfide and hydrogen sulfide, which is reacted with the sulfur to the alkali metal polysulfides according to the invention.
• the alkali metal hydrogen sulfides instead of reacting the concentrated aqueous solutions of the alkali hydrogen sulfides and optionally of the sulfides in mixture with hydrogen sulfides with sulfur and dehydrating the polysulfides, the alkali metal hydrogen sulfides, optionally in admixture with sulfides, before the reaction to dehydrate with the sulfur first and react with the sulfur in a second step the dehydrated hydrogen sulfides and optionally contained therein sulfides.
• this variant involves obtaining the high-melting dry substances during the dehydration of the hydrogen sulfides or the sulfides present in a mixture with the hydrogen sulfides, which makes the production somewhat more complicated.
• alkali metal polysulfides according to the invention are obtained whose solidification temperature is 10 to 20 ° C. below those alkali metal polysulfides according to the invention of the same composition according to the first and preferred process variant.
• the pure alkali metal polysulfides according to the invention preferably sodium polysulfides, with these sulfur contents prove extremely temperature-stable, up to about 700 ° C.
• the high temperature stability of the alkali metal polysulfides according to the invention is especially given values of z less than 3. Sulfur contents with values of z greater than 3.5 usually result in disadvantageously increased viscosities.
• the densities of the alkali metal polysulfides according to the invention are generally at 350 ° C. in the range from 1.8 to 1.9 g / cm 3 .
• alkali metal polysulfides usually form polysulfides up to the hexasulfides.
• the size of the ions influences the viscosity of the alkali metal polysulfides according to the invention.
• the larger potassium ions generally give slightly lower viscosities than the smaller sodium ions.
• alkali metal polysulfides according to the invention it is preferable not to add further salts, for example alkali thiocyanates, to the alkali metal polysulfides according to the invention for lowering their melting points.
• further salts for example alkali thiocyanates
• the thermal stability or the corrosion behavior (especially at high temperature) of the alkali metal polysulfides according to the invention can thereby be changed in a disadvantageous manner.
• the heat transfer / heat storage media according to the invention usually contain the alkali metal polysulfides according to the invention in a substantial amount up to a maximum of practicality
• 100 wt .-% for example in the range of 20 wt .-% to practically 100 wt .-% or 50 wt .-% to practically 100 wt .-%.
• the heat transfer / heat storage media according to the invention are protected against the ingress of moisture during production, storage, transport and use.
• the heat transfer / heat storage media according to the invention are used in a closed system of pipelines, pumps, control devices and containers.
• the low viscosity of the heat transfer / heat storage media according to the invention is particularly advantageous because promoted by a lower viscosity of the heat transfer and the energy required to pump the liquid through the pipes is lowered. In many cases, this can be more important than extending the temperature range downwards.
• Heat storage media with reduced wall thicknesses of piping and equipment, contributes to lower investment costs and avoids sealing problems.
• the operation of plants, preferably those for energy production, at temperatures up to 700 ° C with the heat transfer / heat storage media according to the invention generally requires materials which are stable to sulfidation at high temperatures.
• materials which are stable to sulfidation at high temperatures As already mentioned above, it is known from the literature that sodium polysulfide melts are capable of dissolving metallic gold in the form of complex sulfides. It has been found that the heat transfer media / heat storage media according to the invention then have no particularly great corrosion potential if they contain as little volatile, distillable water as possible.
• Highly suitable materials for the heat transfer medium / heat storage media according to the invention, especially at elevated temperature are the following:
• Particularly corrosion-resistant materials are aluminum and in particular aluminum-containing alloys, for example, high-temperature resistant aluminum-containing steels.
• Such iron materials have ferritic structure and are free of nickel.
• Nickel sulphides form low-melting phases with iron.
• the most effective alloying constituent is aluminum, which has on the surface of the material a dense, passivating oxide layer and / or sulphide Layer forms.
• Sulfur-resistant iron alloys contain less chromium and more aluminum, as described, for example, in EP 0 652 297 A.
• Niobium, boron and titanium serve to precipitate a fine-grained iron aluminide (Fe 3 Al), thus providing increased toughness with strains above 3% and improved processability.
• a particularly good combination of sulphidation resistance with good processability by casting, hot working, cold working and good ductility at room temperature with elongation at break of 20% allows an alloy composition with 8 to 10 weight percent aluminum, 0.5 to 2 weight percent molybdenum, balance Iron. Silicon should not be present in the alloy, it lowers the ductility at room temperature. Shares of chromium are also not beneficial, chromium sulfide is dissolved in the melts.
• zirconium oxide By alloying up to 2 percent by weight of yttrium and / or zirconium zirconium and / or yttrium oxide are also formed in the protective aluminum oxide layer, which greatly increase the ductility of the alumina and thus make the protective layer particularly stable against chipping and mechanical stresses in temperature fluctuations.
• zirconium oxide the ductility of the aluminum oxide layer is advantageously increased.
• Such alloys which are alloys with Fe 3 Al phases, contain 21 at.% Aluminum, 2 at.% Chromium and 0.5 at.% Niobium or 26 at.% Aluminum, 4 at.%.
• the chromium content should be kept as low as possible, it is best to dispense with the chromium as an alloying element.
• molybdenum is recommended in addition to aluminum as a housing material for sodium-sulfur batteries.
• the heat transfer / heat storage media according to the invention can be inexpensively manufactured from inexpensive primary products by the conventional large-scale processes of the chemical industry.
• the alkali metal polysulfides according to the invention can be prepared, for example, in the case of sodium or potassium, by preparing the corresponding hydroxides from sodium and potassium chloride by means of chloralkali electrolysis.
• the hydrogen produced at the same time is advantageously converted with liquid sulfur to hydrogen sulphide.
• the chemical industry has developed very elegant economical continuous and non-pressurized processes which eliminate the need for storage of larger amounts of hydrogen sulphide (e.g., WO 2008/087086). It is generated with the mass flow that is needed by the following stage.
• the hydrogen sulfide is usually mixed with the alkali hydroxides to form the alkali hydrogen sulfides and then reacted with sulfur to form the polysulfides.
• alkali metal polysulfides by reacting concentrated aqueous solutions of ammonium sulfide (NH 4 ) 2 S or ammonium hydrogen sulfide NH 4 HS or mixtures of ammonium sulfide and ammonium hydrogen sulfide with the corresponding alkali hydroxides with elimination of ammonia to give the corresponding alkali metal hydrogensulfides.
• Ammonia is recycled to the synthesis of ammonium sulfides.
• this synthesis route will be carried out if ammonia sulfide and / or ammonium hydrogen sulfide are favorably available from another process, for example from the washing out of hydrogen sulfide from gases.
• potassium sulfate is produced by the fertilizer industry in quantities of millions of tons per year. Economic processes for lowering the chloride content of potassium sulfate, for example by treating the salts with water, are known (DE 2 219 704). If hydrogen is used as the reducing agent, it is possible to work in a solid state at temperatures of 600 to 700 ° C. in a rotary kiln and obtain very clean sulfides (US Pat. No. 20,690,958, DE 590 660). As catalysts for the reduction generally 1 to 5 weight percent of alkali metal carboxylates are used, preferably the formates or the oxalates. However, the most effective catalysts are alkali metal polysulfides, which only have to be added to the alkali metal sulfate at the beginning of the reduction.
• the sulfides are advantageously dissolved in water and converted into the hydrogen sulfides by the introduction of hydrogen sulfide: the equilibrium forms in concentrated aqueous solution
• alkali metal polysulfides according to the invention Complete conversion of the sulfides to the hydrogen sulfides is also generally not necessary here. It is usually sufficient if the formation of the alkali metal hydroxides is suppressed by the addition of hydrogen sulfide and for the implementation of the alkali metal polysulfides according to the invention is a mixture of alkali metal sulfides and alkali metal bisulfides, which contains a very low concentration of alkali metal hydroxide.
• An advantage of the alkali metal polysulfides according to the invention is that they can be prepared in a cost-effective continuous process: the individual reaction steps proceed very rapidly and exothermically. This allows small reaction volumes to be flowed through quickly by the reactants. A well-suited method is performed as follows.
• the resulting stream of hydrogen sulphide, mixed with steam, is cooled and the hydrogen sulphide together with the hydrogen sulphide-containing water in the Level of the hydrogen sulfide synthesis attributed.
• All reaction steps are carried out under inert conditions. Oxygen is usually excluded because it can oxidize the polysulfides to undesirable, the melting temperature of the liquid increasing and most unstable thiosulfates, sulfites and high-melting sulfates.
• Reaction mixers are advantageously used as reactors, followed by residence time ranges to complete the reactions. The reaction times of the individual reactions are in the time range of 0.1 to 10 minutes.
• the solidification point above room temperature can be constructively met with little effort by setting up the mirror and the absorber tubes with a slight slope and the heat carrier / heat storage media according to the invention from the tubes shortly before sunset in a manifold and in heat-insulated buffer tanks for the operation on stored next day in the liquid state a few degrees above the benchmark.
• the pipelines usually have to be insulated very well thermally against heat losses anyway, so that the losses due to heat conduction are low, much lower than during the daytime operation. At the comparatively low temperatures, the radiation losses due to the absorber tubes located in the vacuum are also generally quite low. If the temperature of the circulating heat transfer medium / heat storage media according to the invention should decrease too far, small quantities of the hot heat carrier / heat storage media according to the invention from the corresponding storage tank are admixed with them.
• the heat transfer / heat storage media according to the invention are used as heat transfer in combination with absorber tubes, which carry a coating that allows a high absorption capacity for solar radiation with a low emission for thermal radiation in the temperature range of 150 to 250 ° C in combination.
• the heat transfer / heat storage media according to the invention also allow the combination with another heat transfer fluid. So it is, for example, to operate the or the heat storage of a solar thermal power plant with its large amounts of storage medium with a very inexpensive sulfane-containing and thus low-viscosity sulfur under a pressure as a storage medium, the solar field with its absorber tubes but unpressurized with the smaller amounts of personallyigen to operate according to the invention Alkalipolysulfide. The energy is transferred in this case via an intermediate heat exchanger.
• the tower technology, the heat transfer medium / heat storage media according to the invention are just as suitable as for the parabolic trough construction: Tracking mirrors direct the solar radiation to the top of a tower where it impinges on the receiver and heats the heat transfer fluid in the receiver to the highest possible temperatures.
• the heated liquid is used for steam generation and directed for storage in large volume tanks for night operation. At sunset, you simply let the liquid down from the receiver into a storage tank. Even if you evaporate water directly in the receiver and thus operate a heat engine, there is still the problem of operating the system at night.
• a heat storage fluid for such types of power plants is usually essential.
• the heat transfer / heat storage media according to the invention are also suitable for all other applications of heat transfer and heat storage in the art, which require an extremely wide temperature range of the liquid phase and high temperatures. Their vapor pressure is negligibly low for the purposes of the art.
• the heat transfer / heat storage media according to the invention are also suitable for the transport of heat energy from the fuel elements of a nuclear reactor in a primary circuit, which can thus be operated practically without pressure and thus safely up to temperatures of 700 ° C. This would make a safe, radiation-resistant heat transfer medium available.
• the steam temperatures in the secondary circuit can be significantly increased and the efficiency of nuclear power plants can thus be correspondingly increased.
• the use of the heat transfer / heat storage media according to the invention is limited only by the stability of the materials used.
• the heat transfer / heat storage media according to the invention are far less environmentally hazardous or safety-critical than organic liquids.
• the polysulfides burn with the formation of sulfur dioxide with little luminous flame. Apart from sulfur dioxide, no environmentally toxic products are produced. Sulfur dioxide and the resulting from oxidation with atmospheric oxygen sulfur trioxide are not known as greenhouse gases.
• Burning alkali polysulfides can be easily quenched with water because their density is greater than that of water.
• the evaporating water quickly cools the polysulfide melt, the resulting water vapor simultaneously binds sulfur dioxide.
• Sulfur dioxide must be precipitated with water, the polysulfides dissolve easily in water.
• Polysulfide residues adhering to parts of the system can easily be washed off with water and without residue, leaving no encrustations behind.
• Polysulfides dissolved in water are also oxidized by atmospheric oxygen, usually forming sulfur and sulfates. Both the polysulfides and the sulfur can be oxidized in the soil by sulfur bacteria to sulfates.
• the sulfur released is, as far as known, environmentally neutral.
• Potassium hydrogensulfide was prepared by introducing hydrogen sulfide to saturation in 12 grams of a commercial 50% by weight aqueous potassium hydroxide solution, one mole equivalent, with cooling. In this case, a temperature of 50 ° C was not exceeded. The bulk of the solution increased by 34 grams, corresponding to one mole of hydrogen sulfide. Thus, an aqueous solution of potassium hydrogensulfide in a concentration of 49% by weight was obtained.
• the temperature was further increased after a short time, within 2 to 5 minutes to values around 500 ° C in order to evaporate the water as completely as possible.
• the temperature of the reaction product was maintained for about 2 minutes.
• the temperatures were measured electronically by means of a thermocouple.
• the lower application temperature measured on cooling was the temperature at which the melt on the thermocouple of 1.5 mm diameter when removing it from the melt just started to draw a thin thread.
• the corresponding viscosity was about 200 cP.
• An analogously prepared sodium polysulfide of the composition Na 2 S 3 had a slightly higher viscosity. It began to draw on cooling at 150 ° C threads and solidified on further cooling without crystallization glassy.
• the sodium polysulfide Na 2 S 3 was prepared again, in contrast to the first procedure, however, characterized in that the sodium hydrogen sulfide was dehydrated in a first step by heating to about 350 ° C. In the second step, the sulfur was added and the mixture heated with shaking. The polysulfide thus obtained began to draw threads upon cooling at 135 ° C.
• composition K 2 S 3; 4 began to draw filaments on cooling at 150 ° C. Upon further cooling, it crystallized. When heated to about 750 ° C, it turned dark. Signs of decomposition were not observed. On cooling, she turned red again and began to draw threads at 150 ° C, indicating that she did not experience any change when heated to 750 ° C.
• Example 4 0.02 mol of sodium hydrosulfide, 0.02 mol of potassium hydrogen sulfide and 0.034 mol of sulfur were reacted with one another analogously to Example 1.
• a red low viscosity liquid of the composition Ko , 5 Nao , 5 ) 2 S 2; 7, which on cooling at 125 ° C to draw threads and crystallized on further cooling. The liquid was heated to 700 ° C, whereby it turned dark. After cooling, it again showed the properties as before heating.
• Example 4 A red low viscosity liquid of the composition (Ko , 5 Nao , 5 ) 2 S 2; 7, which on cooling at 125 ° C to draw threads and crystallized on further cooling. The liquid was heated to 700 ° C, whereby it turned dark. After cooling, it again showed the properties as before heating.
• Example 4
• the polysulfide of the above composition was prepared again, but by dehydration of the reaction mixture of the potassium hydrogen sulfide and the sodium hydroxide.
• the dehydrated Hydrogensulfidl sulfide mixture was reacted with the sulfur.
• the resulting red polysulphide began to draw on cooling at 1 15 ° C threads, with further cooling, it solidified glassy.
• Example 4 As in Example 4, 0.024 mole (1.66 grams) of an 81% potassium hydroxide was dissolved in 0.04 mole of the 49% potassium hydrogensulfide while heating. The amount of potassium hydroxide corresponded to 60% of the theoretical amount of potassium hydroxide for complete neutralization of the hydrogen sulfide. In this solution, 0.0544 mol (1, 74 grams) of sulfur were weighed and the reaction mixture after the exothermic use of the reaction while distilling off water and hydrogen sulfide to about 600 ° C heated.
• the thermal stability is promoted by the lowest possible sulfur content.
• compositions are in the range of
• this composition should have a melting range of 360 to 380 ° C.

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