Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F11/00—Compounds of calcium, strontium, or barium
• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
  • A01N59/00—Biocides, pest repellants or attractants, or plant growth regulators containing elements or inorganic compounds
  • A01N59/04—Carbon disulfide; Carbon monoxide; Carbon dioxide
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
  • C01C1/00—Ammonia; Compounds thereof
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
  • C01C1/00—Ammonia; Compounds thereof
  • C01C1/28—Methods of preparing ammonium salts in general
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
  • C01D13/00—Compounds of sodium or potassium not provided for elsewhere
• • 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
  • Y02P60/00—Technologies relating to agriculture, livestock or agroalimentary industries
  • Y02P60/20—Reduction of greenhouse gas [GHG] emissions in agriculture, e.g. CO2
  • Y02P60/21—Dinitrogen oxide [N2O], e.g. using aquaponics, hydroponics or efficiency measures

Definitions

• This invention relates to the manufacture of salts of thiocarbonic acids. In one of its more par ⁇ ticular aspects this invention relates to a process for producing thiocarbonate salts in solid form.
• nematodes which are roundwor s, comprising as many as 10,000 species, of which at least 150 are known to adversely affect plant life.
• Plant parasitic nematodes have been known since about the year 1750. Most of the nematodes which cause crop damage do so by feeding on plant roots, and therefore are found pri ⁇ marily in the upper few inches of soil in the roots or in close proximity to the roots. Nematode feeding
• Important destructive nematode species include the root knot nematodes which are hosted by tomatoes, alfalfa, cotton, corn, potatoes, citrus and many other crops, the golden nematode of potatoes, the sugar beet cyst nematode and the citrus nematode. These, and a few other species, are described in "The Soil Pest Complex", Agricultural and Food Chemistry, Vol. 3, pages 202-205 (1955) . Also described therein is a further complication resulting from nematode infesta ⁇ tion, namely a lowered resistance to the effects of plant attack by bacteria and pathogenic soil fungi.
• Carbon disulfide is the first reported soil fumigant, used in Europe during the 1870's to control the sugar beet nematode. This agent is commercially impractical, however, since very large quantities must be applied, due to its high volatility. Further, the material is quite flammable, reportedly being ignited even by static electricity resulting from pouring the material out of drums. In addition, carbon disulfide possesses a very objectionable odor, and its vapors are toxic to humans. When sold for fumigant use, the carbon disulfide is normally mixed with an inert fire retarding compound, such as carbon tetrachloride, and occasionally also with another fumigant. Typically, these compositions do not contain over about 20 percent by weight of carbon disulfide.
• carbon disulfide has been proven effective in the fumigation of commodi ⁇ ties, as an insecticide, as a rodenticide, and for controlling certain weeds.
• compositions possessing nematocidal properties have been developed, including active ingre ⁇ progenated compounds such as the polyamines of U.S. Patent 2,979,434 to Santmyer, the heterocyclic compounds of U.S. Patent 2,086,907 to Hessel, and various hal ⁇ genated compounds.
• active ingre ⁇ progenated compounds such as the polyamines of U.S. Patent 2,979,434 to Santmyer, the heterocyclic compounds of U.S. Patent 2,086,907 to Hessel, and various hal ⁇ genated compounds.
• useful halogen-containing nematocides are 1,2-dibromoethane, methyl bromide, 3-bromopropyne, 1,2- dichloropropane, ethylene dichl ⁇ ride and others, all of which are quite phytotoxic, therefore restricting their utility to mostly preplant treatments.
• DBCP l,2-dibromo-3-chloropropane
• use of this material has been limited due to a finding of undesira ⁇ ble reproductive system effects in workers exposed to the chemical, and the possibility that the compound is a carcinogen.
• the unavailability of DBCP has been a serious setback to growers of perennial crops, such as grapes, stone fruits and nuts, since these crops expe ⁇ rience more severe cumulative nematode population increases, and most replacement soil fumigants are phytotoxic.
• U.S. patents concerned with the use of DBCP as a soil fumigant include 2,937,936 to Schmidt and 3,049,472 to Swezey.
• a further class of materials used to control nematodes includes some thiocarbonates.
• U.S. Patent 2,676,129 to Bashour describes the preparation of lower aliphatic disubstituted trithiocarbonates having the structure as in (1) :
• R ⁇ . and R 2 are k l radicals having from three to nine carbon atoms.
• the compounds were dissolved in acetone and added to nematode-infested soils, resulting in control of the nematodes.
• nitrate e.g., ammonium nitrate-containing fertilizers
• Ammonium nitrogen is fairly tightly bound by various physical and chemical processes in a soil environment and, therefore, is much less subject to losses. Unfortunately, the bound ammonium nitrogen is also less available to plants.
• the process of nitrification results in conversion of ammonium ions into nitrate ions.
• Micro- bial species known as nitrosomonas oxidize ammonium to nitrate; nitrobacter species oxidize nitrite to ni ⁇ trate.
• compositions have been offered as inhibitors of nitrification, including expensive organ ⁇ ic materials such as 2-chloro-6-(trichloromethyl)- pyridine, 2-amino-4-chloro-6-methyl-pyrimidine, sulfa- thiazoles, alkanoylsulfathiazoles, and others.
• organ ⁇ ic materials such as 2-chloro-6-(trichloromethyl)- pyridine, 2-amino-4-chloro-6-methyl-pyrimidine, sulfa- thiazoles, alkanoylsulfathiazoles, and others.
• organ ⁇ ic materials such as 2-chloro-6-(trichloromethyl)- pyridine, 2-amino-4-chloro-6-methyl-pyrimidine, sulfa- thiazoles, alkanoylsulfathiazoles, and others.
• Carbon disulfide in very small amounts is described as having "a remarkable inhibitory effect on nitrification of ammonium in soils incubated in closed systems.” Carbon disulfide was tested in the field by J. Ashworth et al., Chemistry and Industry. September 6, 1975, pages 749-750, and found to be effective as a nitrification inhibitor. Hawkins, in U.S. Patent 4,078,912, describes the use of sodium, potassium and ammonium trithiocarbonates, and of xanthates, either alone or in fertilizer mixtures, to inhibit nitrifica- tion; the mode of operation is attributed to a release of carbon disulfide by the compounds.
• Yeoman reports a further study of thiocarbonates (called trithiocarbonates therein) and also reports the preparation and proper ⁇ ties of perthiocarbonates (or tetrathiocarbonates) , derivatives of tetrathiocarbonic acid (H 2 CS 4 ) .
• Yeoman reports on methods of preparing the ammonium, alkali metal and alkaline earth metal salts of these acid species. For example, Yeoman prepared ammonium trithi ⁇ ocarbonate by saturating an alcoholic ammonia solution with hydrogen sulfide and then adding carbon disulfide to precipitate the product salt.
• Ammonium perthiocar- bonate was prepared in a similar manner, except that after reacting the ammonia and hydrogen sulfide, ele ⁇ mental sulfur was added to form the disulfide, (NH 4 ) 2 S 2 ; adding carbon disulfide immediately precipi ⁇ tated the product.
• solutions of sodium perthiocarbonate are reported to be stable for a con ⁇ siderable time in the absence of oxygen, the presence of air causing decomposition into thiosulfate and carbon disulfide, while carbon dioxide decomposes the compound to form a carbonate, elemental sulfur, carbon disulfide and hydrogen sulfide.
• the potassium thiocar ⁇ bonates behave similarly, according to Yeoman.
• Yeoman also attempted to prepare and charac ⁇ terize the stability of thiocarbonate salts of four of the alkaline earth metals. Yeoman was unable to pre ⁇ pare a pure calcium tri- or tetrathiocarbonate, but did observe that the double salt of calcium trithiocarbon ⁇ ate which he prepared was more stable (probably because it was less hygroscopic) than the sodium or potassium thiocarbonates.
• the barium salt of tetrathiocarbonic acid could not be isolated, although Yeoman believed it existed in solution. Solid barium trithiocarbonate could not be isolated, although it was alleged to behave like sodium trithiocarbonate when dissolved in water. The preparation of aqueous solutions of the tri- and tetrathiocarbonates of magnesium and strontium was alleged, but the magnesium thiocarbonates were not isolated.
• the previously noted paper by Mills and Robinson shows the preparation of ammonium thiocarbon ⁇ ate by digesting ammonium pentasulfide with carbon disulfide.
• the ammonium pentasulfide was obtained by suspending sulfur in aqueous ammonia, then saturating with hydrogen sulfide.
• a crystalline residue from the reaction was found to be ammonium perthiocarbonate.
• the authors prepared a "better" ammonium perthiocarbon ⁇ ate product, however, by extracting the ammonium penta ⁇ sulfide with carbon disulfide in a Soxhlet apparatus.
• Stone et al. disclose several methods for preparing solid ammonium, alkali and alkaline earth metal salts of tri- and tetraperoxythiocarbonates, hereinafter referred to simply as
• tetrathiocarbonates One such method involves the solution of an active metal such as sodium in anhydrous ethanol to form an ethoxide which, in turn, is reacted with hydrogen sulfide and carbon disulfide to form sodium trithiocarbonate. They report, however, that the trithiocarbonates tend to be quite soluble in ethanol, and if it is desired to recover the solid material from the solution, it is necessary to treat the reaction mixture with a "displacing agent" such as ether, in which case the thiocarbonates frequently separate, not as solids, but as difficultly crystalliz- able oils which appear to be saturated aqueous solu ⁇ tions of the trithiocarbonate salt. Consequently, such a procedure is not considered feasible for use on a commercial scale. Similar problems were reported with tetrathiocarbonate salts, which were prepared using procedures analogous to those for the trithiocarbon ⁇ ates.
• the present invention provides a process for the production of salts of thiocarbonic acids in solid form, stabilized thiocarbonates and methods for their use.
• stabilized aqueous solutions of thiocarbonate salts are converted to solid thiocarbonates by evaporating to dryness.
• Such stabilized aqueous solutions are described in copending applications Serial Nos. 07/262,961, filed October 28, 1988, 07/262,962, filed October 28, 1988, 07/415,874, filed February 10, 1989 and 07/440,024, filed November 21, 1989, the disclosures of which in their entireties are incorporated herein by reference, in which a sulfide, polysulfide and/or base are used to stabilize the thiocarbonate solution.
• Water is evaporated from an aqueous solution of a salt of the desired trithiocarbonic acid or tetra- thiocarbonic acid containing a stabilizing amount of a sulfide, polysulfide and/or base.
• a stabilizing amount of a sulfide, polysulfide and/or base Preferably a stabi ⁇ lizing amount of a sulfide or polysulfide is used. More preferably a stabilizing amount of a base is used with the sulfide or polysulfide.
• Evaporation can be accomplished by boiling the solution under vacuum or evaporating at ambient pressures and sub-boiling tem ⁇ peratures.
• a wet solid is produced and the wet solid is then further dried at elevated tempera ⁇ tures to produce the desired essentially dry solid product.
• the two steps are combined in a semi-continuous process.
• solid thiocarbonate salts stems from the fact that, in addition to being more easily handled and transported, the rate of re ⁇ lease of CS 2 from the solid salts can be readily manip ⁇ ulated by various methods such as coating the solid salt or mixing with adjuvants.
• solid thiocarbonate salts are advanta ⁇ geous for use in dry farming.
• a solid thiocar ⁇ bonate applied to dry soil will release CS 2 upon con ⁇ tact with water, for example rain.
• a particular advantage of the process of the present invention is that the previously available methods of producing solid thiocarbonate salts required the use of organic solvents, the disposal of which presented environmental problems.
• the present inven ⁇ tion requires no organic solvents and presents no disposal problems.
• a further advantage is that the "stabilized" solid thiocarbonates obtained by the described methods are more stable than the solids obtained by previous investigators, and they are therefore more useful as fumigants, intermediates for the manufacture of other thiocarbonate-containing compositions, and for the manufacture of "stabilized" thiocarbonate solutions, such as those described in copending applications Serial Nos. 07/262,961 and 07/262,962, supra, upon dissolution in water.
• the sole figure of the drawing is a schematic representation of a flowsheet in partial elevation showing a system for conducting the process of the present invention.
• aqueous solutions of thiocarbonates are useful for various commercial applications, such as in the control of nematodes and other soil-borne and water-borne plant pathogens, the use of thiocarbonate solutions has several disadvantages. Because aqueous solutions of thiocarbonates break down upon exposure to air, elevated temperatures or a low pH environment, the solutions must be kept tightly covered during handling prior to use. In addition the solutions have a rela ⁇ tively short half-life after application to the soil.
• the "stabilized" solid thiocarbonates described herein are more suitable than the solid thiocarbonates previously available as intermediates for the manufacture of other materials ' such as the stabilized solid thiocarbonate compositions disclosed by Pilling and Young in copending application Serial No. 07/290,992, filed December 28, 1988, the disclosure of which is incorporated herein by reference in its entirety.
• the stabilized, aqueous thiocarbonate solu ⁇ tions from which the stabilized solids can be derived involve aqueous solutions of thiocarbonates, soluble in the solution and having the general formula A a CS b wherein A is a mono- or divalent cation, b is 3 to 4, a is 2 when A is a monovalent cation, and a is 1 when A is a divalent cation, and a base and/or a sulfide and/or polysulfide of the formula M n S ⁇ wherein M is selected from mono- and divalent cations, and combina ⁇ tions thereof, x is at least 1, n is 2 when M is a aonovalent cation, and n is 1 when M is a divalent cation.
• the aqueous solutions can comprise mixtures of tri- and tetrathiocarbonates having the same or differ ⁇ ent cations as well as mixtures of sulfides and poly- sulfides of the same or different cations.
• the thio ⁇ carbonates presently preferred are the ammonium and alkali and alkaline earth metal thiocarbonates and combinations of these, with the alkali and alkaline earth metal thiocarbonates being the most preferred.
• the "stabilized solid” thiocarbonates are "non-stoichiometric" in that they contain excess, equivalent base and/or sulfide and that they are more stable upon exposure to water, air and/or elevated temperatures than are solids prepared from aqueous or non-aqueous media and "stoichiometric" thiocarbonate compositions, i.e. compositions comprising only amounts of carbon, sulfur and cation corresponding to the empirical formula for the corresponding tri- and/or tetrathiocarbonates in the absence of significant amounts of excess base and/or sulfide.
• the stabilized, solid thiocarbonates are stable in air at 24° C.
• the stability of the solids in air at the selected relative humidity and temperature can be readily determined by screening the solids to obtain particles passing 30 U.S. standard mesh and letting those particles stand under the designated conditions until a characteristic color change (to white) occurs, for a designated period of time, or until a specified amount of equivalent CS 2 has been lost to the atmos ⁇ phere.
• CS 2 loss can be determined by capturing the vapor phase overlying the solid and analyzing it for carbon disulfide.
• the amount of equivalent CS 2 remaining in the solid after the aforegoing stabil ⁇ ity test can be determined by dissolving the remaining solid in water, acidifying to a pH of about 4 or less to decompose the thiocarbonate, and capturing the resulting CS 2 released in a toluene phase overlying the water phase in which the thiocarbonate is dissolved.
• the evolved CS 2 is captured in the toluene phase, and its concentration can be determined by analyzing the toluene phase for CS 2 by gas chromatography.
• the stabilized solids can also be character ⁇ ized by composition, i.e. the amount of equivalent base, sulfide and/or polysulfide in excess of the stoichiometric composition of the thiocarbonate.
• the amount of excess base, sulfide and/or polysulfide will usually correspond to at least about 0.01, typically at least about 0.02, preferably at least about 0.04 and most preferably at least about 0.08 equivalent of base, sulfide or polysulfide per equivalent of carbon disul ⁇ fide in the solid thiocarbonate.
• stabilized, solid thiocarbonates In addition to the several advantages of the stabilized, solid thiocarbonates discussed herein, they have the further advantage that, when dissolved in water, they form stabilized, thiocarbonate solutions such as those disclosed in copending applications Serial Nos. 07/262,961 and 07/262,962. As disclosed in those copending applications, stabilized, aqueous solutions of thiocarbonates containing excess base, sulfide and/or polysulfide are much more resistant to thiocarbonate decomposition and are therefore more useful as fumigants, intermediates, and in other indus ⁇ trial applications.
• the resulting, stabilized, solid thiocarbon ⁇ ates can be used directly as such or can be dissolved in water or solvents other than water for use in agri ⁇ culture or industrial applications where thiocarbonates are useful or required.
• the solids, or solutions derived therefrom can be employed as fumigants for enclosed spaces, stored grains or other perishables, soil fumigants for the control of plant pathogens and vectors, e.g. nematodes, insects, fungi, bacteria, viruses, et cetera, or may be applied to the foliage of plants, the soil surface or to other areas for the control of pests of all varieties.
• a stabilized, aqueous solution of a thiocarbonate salt is converted to a solid thiocarbonate salt by a process which involves removing the water from a stabilized, aqueous, thiocarbonate salt solution. Since thiocar ⁇ bonate salt solutions break down upon exposure to excessively elevated temperatures, it is not possible merely to evaporate a thiocarbonate salt solution to dryness at any elevated temperature. Moreover, it is difficult and generally not possible to evaporate a stoichiometric thiocarbonate solution to dryness, since CS 2 will be released and the typical product will be an oil rather than the desired solid. Consequently, it is necessary to stabilize the solution by the use of sulfides, polysulfides or bases, as will be explained in detail in the ensuing description.
• the term "stability", as used herein with regard to the aqueous solutions, can be regarded as a composite of two concepts: chemical stability and physical stability. Since the effectiveness of a composition depends, at least in part, upon its ability to release carbon disulfide during decomposition, chemical stability is expressed accordingly; this can be quantified by, for example, chemically decomposing the composition and measuring the amount of carbon disulfide which evolves. Alternatively, an indication of the amount of available carbon disulfide can be obtained by spectrophotometrically determining the presence of the thiocarbonyl bond ( C S) in a sample of the composition. The absorbance at wavelengths corresponding to those at which thiocarbonyl is known to absorb energy can be used for a quantitative analy ⁇ sis.
• Symptomatic of chemical stability is physical stability. This concept is important due to the nature of the products formed during decomposition of the composi ⁇ tion, particularly the ammonia (when present) , hydrogen sulfide, and carbon disulfide, which each have a high vapor pressure. It is readily apparent that a change in the physical form of the composition from a solution of low vapor pressure into a mixture of compounds, each possessing a high vapor pressure, imposes some rather stringent requirements upon storage containers. Vapor pressure above the composition of the invention, there ⁇ fore, will be used herein as an indicator of physical stability; a condition of maintained low vapor pressure is the desired property.
• Another index of physical instability is the formation of undesirable insoluble precipitates, which frequently comprise sulfur, or of an immiscible liquid phase, such as carbon disulfide. The more general description of physical stability, then, is the maintenance of only a single phase in the composition.
• Assessment of the stability of a particular solution usually involves consideration of both the chemical stability and the physical stability over a period of time during which stability is desired. Certain formulations do not form precipitates and do not develop high vapor pressures during a reasonable storage period and, therefore, may be preferred over a formulation which has a greater chemical stability, but develops objectionable physical characteristics during storage.
• the useful thiocarbonates include, without limitation, salts of trithiocarbonic acid and tetrathi- ocarbonic acid, compositions having empirical formulae intermediate to these acid salts (such as MCS 3>7 , wherein M is a divalent metal ion) , and compositions containing substances in addition to thiocarbonates, such as a stabilized ammonium tetrathiocarbonate which contains ammonium sulfide, i.e., (NH 4 ) 2 CS 4 * (NH 4 ) 2 S.
• These compositions are generally water soluble and can be prepared, stored, and used in aqueous solutions. The solutions are stable during prolonged periods of storage in a closed container, exhibit low vapor pres ⁇ sure, and are not flammable.
• Aqueous solutions that can be stabi ⁇ lized by the addition of base, sulfide and/or polysul ⁇ fide include solutions of alkali, alkaline earth and ammonium tri- and tetrathiocarbonates and combinations of these, and very stable alkali metal and alkaline earth metal tetrathiocarbonate solutions can be ob ⁇ tained.
• Stability enhancement can be achieved by providing, in the solution, an organic or inorganic base which, preferably, is soluble in the solution, and more preferably, has significant solubility in water.
• bases include water-soluble inor ⁇ ganic bases, and the most preferred, are alkali metal and ammonium hydroxides, and combinations of these.
• similar increases in stability can be achieved by providing, in the solution, a sulfide and/or polysulfide which, preferably, is soluble in the solution, and more preferably, has significant solubil ⁇ ity in water.
• Illustrative sulfides include ammonium, alkali and alkaline earth metal sulfides and polysul- fides having the general, empirical formula M n S ⁇ , wherein M is ammonium, alkali or alkaline earth metal, x is at least about 1, preferably greater than 1 in the case of polysulfides, and usually within the range of 1 to about 5, most preferably greater than 1 to about 5, n is 2 when M is ammonium or alkali metal, and n is 1 when M is an alkaline earth metal. Combinations of different sulfides and/or polysulfides can be employed.
• combinations of ammonium, alkali and/or alkaline earth metal sulfides and/or polysulfides can be used to stabilize the thiocarbonate compositions, and combina ⁇ tions of the described bases, sulfides and/or polysul ⁇ fides can be used to achieve further enhanced stabili ⁇ ty, and are presently preferred.
• the most preferred stabilized, thiocarbonate solutions contain added base in addition to one or more of the described sulfides or polysulfides.
• the useful compositions comprise aqueous solutions of thiocarbonates containing added base, sulfide and/or polysulfide.
• the amount of added base, sulfide or polysulfide will correspond to about 0.01, usually about 0.02, preferably at least about 0.04, and most preferably about 0.08 equivalents of base, sulfide or polysulfide per equivalent of carbon disulfide in the solution.
• Concentrated, aque ⁇ ous tetrathiocarbonate solutions having CS 2 vapor pressures corresponding to CS 2 concentrations in the equilibrium vapor phase below about 1 volume percent at 24° C.
• base concentra ⁇ tions of about 0.02 equivalent of base per equivalent of carbon disulfide.
• the concentration of sulfide and/or polysulfide required to achieve the desired reduction in CS 2 par ⁇ tial pressure is generally somewhat higher than the concentration of base required to achieve a similar stability improve ⁇ ment.
• concentrations of sulfide and/or polysulfide of about 0.04 or more equivalent of sulfide and/or polysulfide per equivalent of carbon disulfide.
• concentrations of sulfide and/or polysulfide of about 0.04 or more equivalent of sulfide and/or polysulfide per equivalent of carbon disulfide.
• greater solution stability and lower CS 2 partial pressures can be achieved by using even higher concentrations of sulfides and/or polysulfides, or by employing combinations of base and sulfide and/or polysulfide.
• the concentration of sulfide, polysulfide or combination thereof will correspond to at least about 0.02, preferably at least about 0.04, and most preferably at least about 0.08 equivalent of sulfide and/or polysulfide per equivalent of carbon disulfide.
• concentrations of each can be reduced by approximately 1/2 to obtain a comparable degree of stability improvement and CS 2 partial pressure reduction.
• the degree of stability enhancement achieved by the use of 0.02 equivalent of base per equivalent of carbon disulfide can be achieved by using approximately 0.01 equivalent of base in combination with about 0.01 equivalent of sulfide or polysulfide.
• the term "equivalent,” as employed herein, is used in its conventional sense.
• one mole of carbon disulfide constitutes 2 equiv ⁇ alents, and the same is true for the sulfide and poly ⁇ sulfide and for the alkaline earth metal bases and other bases which can be employed in which the cation is divalent.
• one mole of the ammonium and alkali metal bases, wherein the cation is monovalent constitute only 1 equivalent. Therefore, on a molar basis, as opposed to an equivalent basis, 2 moles of an alkali metal hydroxide, e.g. sodium hydroxide, are equivalent to 1 mole of carbon disulfide.
• the amount of base, sulfide and/or polysulfide employed should be sufficient to reduce the carbon disulfide partial pressure of the solution by the desired amount, and the amount of additive required to achieve that effect can be easily determined by adding different, known quantities of base, sulfide and/or polysulfide to the desired thio ⁇ carbonate solution, confining the vapor space over the solution at 24° C. for a sufficient period of time, e.g. about 24 hours, and analyzing the vapor phase by gas chromatography for carbon disulfide.
• Lower addi ⁇ tive concentrations will result in somewhat higher CS 2 equilibrium concentrations (e.g. higher CS partial pressures) , and higher additive concentrations will result in lower CS 2 partial pressures.
• compositions are those in which the carbon disulfide partial pres ⁇ sure has been reduced to a level corresponding to about 1 volume percent or less carbon disulfide in the equi ⁇ librium vapor phase at 24° C.
• a greater safety factor, with regard to CS 2 partial pressure, toxicity, handling difficulty, etc. can be realized by reducing CS 2 partial pressure even further.
• more preferred thiocarbonate solutions are those in which the carbon disulfide partial pressure corresponds to less than about 0.5, most preferably less than about 0.2 volume percent carbon disulfide in the equilibrium vapor phase overlying the solution at 24° C.
• Base-containing compositions of enhanced stability can be readily obtained by providing the desired amount of base in the thiocarbonate salt solution.
• Base can be introduced before, during or after preparation of the thiocarbonate salt solution, it being necessary only that the final composition contain additional base.
• such added base is provided either during or after preparation of the thiocarbonate salt solution.
• Similar techniques can be employed to pre ⁇ pare sulfide- and polysulfide-containing compositions.
• soluble sulfide or polysulfide can be introduced before, during or after preparation of the thiocarbon ⁇ ate salt solution, although sulfides are preferably added either during or after preparation of the thio ⁇ carbonate salt solutions.
• Sulfide and polysulfide can be provided in the composition by direct addition of such compounds, or they can be formed in situ.
• an amount of base for example, potassium hydroxide
• an equivalent quantity of hydrogen sulfide to convert the base to the corresponding sulfide, potassium sulfide (K 2 S) .
• the polysulfides can be formed in situ by addition of elemental sulfur with adequate agitation to promote the reaction of the elemental sulfur with the sulfide already present in the composition.
• the present process removes water from the aqueous, thiocarbonate salt solution which has been stabilized against loss of CS 2 .
• Water is removed by treatment at temperatures which result in the evapora ⁇ tion of water from the solution without excessive decomposition of the thiocarbonate salt, which decompo ⁇ sition results in the loss of CS 2 from the salt.
• Such process is conducted by evaporating the stabilized, thiocarbonate salt solution at temperatures below the boiling point of the solution or by boiling the stabi ⁇ lized, thiocarbonate salt solution under sufficient vacuum to ensure that significant decomposition does not occur.
• any evaporation process or vacuum distilla ⁇ tion process which meets these requirements is satis ⁇ factory for the purposes of this invention.
• vacuum evaporation is used for evaporation of water from a stabilized aqueous solution of a thiocarbonate since thiocarbonates are subject to decomposition at relatively low temperatures.
• any procedure can be employed which results in the formation of a dried thiocarbonate containing a significant amount of bound- CS 2 .
• the stabilized, aqueous solution can be evaporated at ambient temperatures and pressures by simply allowing water to evaporate from the solution into the air.
• a vacuum can be drawn on the solution and/or the solution can be heated to a temperature that does not result in excessive thiocarbonate decomposi ⁇ tion.
• Excessive thiocarbonate decomposition means such extensive decomposition of the thio ⁇ carbonate initially present in the stabilized solution that an insignificant amount of solid thiocarbonate is recovered as a result of the evaporation procedure.
• the invention will be described with refer ⁇ ence to producing a solid potassium tetrathiocarbonate product.
• Other thiocarbonates can be used as well.
• the decomposition point of solid potassium thiocarbon ⁇ ate determined in a melting point apparatus is about 302° F.
• the boiling point of aqueous solutions of thiocarbonates varies depending upon the concentration and pressure. For example, a 40 weight percent solu ⁇ tion of potassium thiocarbonate boils at about 155° F. under a vacuum of about -25 inches Hg whereas the boiling point at atmospheric pressure is about 215° F. In general, the boiling point at atmospheric pressure is about 60° F. higher than under a vacuum of -25 inches Hg.
• An 80 weight percent oily solution of the salt boils at about 195° F. under a vacuum of -25 inches Hg and at about 255° F. at atmospheric pressure. Distilling off the water from a solution of potassium thiocarbonate under a vacuum of about -25 inches Hg causes the temperature to slowly rise to about 200° F. as the vacuum distillation proceeds. At this point a solid begins to separate from the solution. The solid which is formed is moist to the touch and has a tenden ⁇ cy to cake.
• Drying to produce a non-caking solid can be accomplished at ambient pressure using a rotary dryer, a spray dryer, an evaporator or a low temperature kiln.
• a dry solid is produced at ambient pressure with the temperature rising from about 270° F. to about 290° F.
• the potassium tetrathiocarbonate begins to decompose at temperatures over about 300° F.
• Drying under a vacuum of about -25 inches Hg or lower is preferred, because by drying a stabilized aqueous thiocarbonate salt solution under a vacuum a dry solid thiocarbonate salt is produced at tempera ⁇ tures substantially below the decomposition temperature of the salt.
• a dry solid is formed at a temperature of about 210° F. to about 230° F. Drying under a vacuum is typically accomplished by using a Sigma blades mixer, a ribbon mixer or a rotary mixer.
• a liquid storage tank 10 is connected to a feed pump 12 by means of a conduit 14.
• Feed pump 12 is connected to a liquid distributor 16 by means of a conduit 18.
• Liquid distributor 16 is disposed within and is part of rotary dryer 20 which is equipped with a heating jacket 22.
• Rotary dryer 20 is connected to a heat exchanger 24 which functions as a condenser by means of a conduit 26.
• a vacuum receiver 28 is con ⁇ nected to heat exchanger 24 by means of a conduit 30.
• a condensate pump 32 is connected to vacuum receiver 28 by means of a conduit 34.
• a gas blower 36 is connected to vacuum receiver 28 by means of a conduit 38 equipped with a valve 40. Gas blower 36 is connected to a vacuum pump, not shown, by means of a valve 42 and a conduit 44.
• Gas blower 36 is bypassed by means of a conduit 46 equipped with a valve 48. Gas blower 36 is also connected to another valve 50 which is connected to a gas heater 52 by means of a conduit 54 and to a valve 56 in a conduit 58 which connects with an inert gas supply, not shown. Gas heater 52 is connected to a gas inlet 60 of rotary dryer 20 by means of a conduit 62.
• Rotary dryer 20 is adapted to rotate in the direc ⁇ tion shown by arrow 64. Alternatively, rotary dryer 20 can be replaced with a stationary vessel equipped with internal, rotating mixing elements, if desired.
• a gas outlet 66 of rotary dryer 20 is connected to conduit 26. Within rotary dryer 20 are shown liquid sprays 68 exiting from liquid distributor 16, solid product 70 and grinding media 72 shown intermixed with solid product 70.
• Starting materials for the process of the present invention are typically thiocarbonate salt solutions having concentrations of about 15 to about 80 weight percent thiocarbonate and preferably concentra ⁇ tions of about 30 to about 60 weight percent.
• potassium tetrathiocarbonate has been mentioned specif ⁇ ically, it should be understood that other thiocarbon ⁇ ates such as ammonium trithiocarbonate and tetrathio ⁇ carbonate and other alkali metal and alkaline earth metal thiocarbonate salts as well as other metal salts of thiocarbonic acids can be similarly processed to provide solid thiocarbonates.
• Stabiliza ⁇ tion can be accomplished by including with the thiocar ⁇ bonate a base, a soluble sulfide salt or a polysulfide.
• the stabilized aqueous thiocarbonate salt solution exemplified herein as K CS 4
• K CS 4 the stabilized aqueous thiocarbonate salt solution
• Rotary dryer 20 is maintained at the desired temperature by means of heating jacket 22 which increases and controls the temperature of the K CS 4 solution in the rotary dryer.
• heating jacket 22 which increases and controls the temperature of the K CS 4 solution in the rotary dryer.
• water vapor from the K 2 CS 4 solution is condensed in the heat exchanger 24 through the conduit 30 to the vacuum receiver 28 to be disposed of by means of condensate pump 32.
• the rotary dryer is rotated in the direction shown by arrow 64.
• the grinding media shown as grinding media 72 in the drawing, which are optional, are typically ceramic balls or alloy steel balls which are added to prevent caking or sticking of the solid product on the walls of rotary dryer 20.
• internal wipers or blades can be used to maintain the heat transfer surface of rotary dryer 20 or an alternative stationary vessel free of solids.
• a process which utilizes an inert gas such as nitrogen as the heating medium can be used.
• the stabilized aqueous thiocar ⁇ bonate salt solution exemplified herein as K CS 4
• the stabilized aqueous thiocar ⁇ bonate salt solution exemplified herein as K CS 4
• Rotary dryer 20 is maintained at the desired tempera ⁇ ture by means of heating jacket 22 and gas heater 52, which control the temperature of the inert gas entering rotary dryer 20 through gas inlet 60.
• the rate at which the solution is sprayed into the rotary dryer also controls the rate of evaporation of the water from the solution and the rate of deposition of solid on the accumulating bed of solids within the rotary dryer.
• the inert gas supply not only prevents unwanted oxygen from entering the rotary dryer, but also serves to sweep the water vapor from the dryer through gas outlet 66 and conduit 26 to heat exchanger 24.
• Water vapor released from the K 2 CS 4 solution during the evaporation and drying process is condensed in heat exchanger 24 and passed through conduit 30 to vacuum receiver 28 to be disposed of by means of condensate pump 32.
• the inert gas is passed through gas blower 36 and valve 50, and is recycled to gas heater 52. Valves 42, 48 and 56 are closed during this process. Additional inert gas can be supplied through valve 56 if required.
• a combination of the above two processes is also desirable.
• vacuum is used to evaporate the water vapor from the thiocarbonate solu ⁇ tion and inert gas is later used to dry the solid.
• the solid thiocarbonate salts produced ac ⁇ cording to the present invention may be somewhat hygro ⁇ scopic. In that event, and particularly under condi ⁇ tions of high humidity, the solid products are prefera ⁇ bly packed in appropriate containers and sealed after drying.
• the present invention thus provides a process for producing solid salts of thiocarbonic acids conven ⁇ iently without utilizing organic solvents and without causing decomposition of the thiocarbonate salts.
• the invention may be embodied in other forms without departing from the spirit or essential charac ⁇ teristics thereof.
• other devices than a rotary dryer can be used to evapo ⁇ rate water from the aqueous thiocarbonate solutions used as starting materials in the process of the present invention. Consequently, the present embodi ⁇ ments are to be considered only as being illustrative and not restrictive, with the scope of the invention being indicated by the appended claims. All embodi ⁇ ments which come within the scope and equivalency of the claims are therefore intended to be embraced there ⁇ in.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Pest Control & Pesticides (AREA)
• Materials Engineering (AREA)
• Agronomy & Crop Science (AREA)
• Geology (AREA)
• Plant Pathology (AREA)
• Health & Medical Sciences (AREA)
• Dentistry (AREA)
• General Health & Medical Sciences (AREA)
• Wood Science & Technology (AREA)
• Zoology (AREA)
• Environmental Sciences (AREA)
• Agricultural Chemicals And Associated Chemicals (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=23930693

Family Applications (1)

Country Status (12)

Families Citing this family (1)

Citations (5)

Family Cites Families (2)

• 1990
  • 1990-09-24 IN IN757/MAS/90A patent/IN171497B/en unknown
  • 1990-09-27 IL IL95826A patent/IL95826A0/xx unknown
  • 1990-10-01 AP APAP/P/1990/000210A patent/AP162A/en active
  • 1990-10-01 MA MA22236A patent/MA21967A1/fr unknown
  • 1990-11-19 CN CN90109298A patent/CN1054403A/zh active Pending
• 1991
  • 1991-02-26 AU AU73446/91A patent/AU7344691A/en not_active Abandoned
  • 1991-02-26 HU HU922623A patent/HUT61709A/hu unknown
  • 1991-02-26 WO PCT/US1991/001325 patent/WO1991013028A1/en active Application Filing
  • 1991-02-26 JP JP3505254A patent/JPH05504930A/ja active Pending
  • 1991-02-27 PL PL28922091A patent/PL289220A1/xx unknown
  • 1991-02-28 CS CS91530A patent/CS53091A2/cs unknown
  • 1991-02-28 PT PT96915A patent/PT96915A/pt not_active Application Discontinuation

Patent Citations (5)

Also Published As

Similar Documents

Legal Events