Potassium compounds, production

Preparation and Manufacture. Magnesium chloride can be produced in large quantities from (/) camalhte or the end brines of the potash industry (see Potassium compounds) (2) magnesium hydroxide precipitated from seawater (7) by chlorination of magnesium oxide from various sources in the presence of carbon or carbonaceous materials and (4) as a by-product in the manufacture of titanium (see Titaniumand titanium alloys). 

In 1840, potassium was recognized as an essential element for plant growth (6). This discovery and the invention in 1861 of a process to recover potassium chloride from mbbish salt, a waste in German salt mines, started the modem potassium chemical industry (5). Potassium compounds produced throughout the world in 1993 amounted to ca 22 million metric tons as K O equivalent (4), down from ca 24 million t in 1992, having fallen annually from 32 million t in 1989 (2). Estimated production capacity was between 29 and 32 million t in 1992 (2). 

Approximately half of the iodine consumed is used to make potassium iodide (see Iodine and iodine compounds). Production of KI is almost 1000 t/yr. Its main uses are in animal and human food, particularly in iodized salt, pharmaceuticals (qv), and photography (qv). 

Sulfates of sodium are iadustriaUy important materials commonly sold ia three forms (Table 1). In the period from 1970 to 1981, > 1 million metric tons were consumed aimuaHy ia the United States. Siace then, demand has declined. In 1988 consumption dropped to 890,000 t, and ia 1994 to 610,000 t (1,2). Sodium sulfate is used principally (40%) ia the soap (qv) and detergent iadustries. Pulp and paper manufacturers consume 25%, textiles 19%, glass 5%, and miscellaneous iadustries consume 11% (3). About half of all sodium sulfate produced is a synthetic by-product of rayon, dichromate, phenol (qv), or potash (see Chromium compounds Fibers, regenerated cellulosics Potassium compounds). Sodium sulfate made as a by-product is referred to as synthetic. Sodium sulfate made from mirabilite, thenardite, or naturally occurring brine is called natural sodium sulfate. In 1994, about 300,000 t of sodium sulfate were produced as a by-product another 300,000 t were produced from natural sodium sulfate deposits (4). 

Tantalum Compounds. Potassium heptafluorotantalate [16924-00-8] K TaF, is the most important tantalum compound produced at plant scale. This compound is used in large quantities for tantalum metal production. The fluorotantalate is prepared by adding potassium salts such as KCl and KF to the hot aqueous tantalum solution produced by the solvent extraction process. The mixture is then allowed to cool under strictiy controlled conditions to get a crystalline mass having a reproducible particle size distribution. To prevent the formation of oxyfluorides, it is necessary to start with reaction mixtures having an excess of about 5% HF on a wt/wt basis. The acid is added directiy to the reaction mixture or together with the aqueous solution of the potassium compound. Potassium heptafluorotantalate is produced either in a batch process where the quantity of output is about 300—500 kg K TaFy, or by a continuously operated process (28). 

The use of potassium hexafluorosihcate is preferred over sodium hexafluorosihcate because of the lower tendency of the potassium compound to dissociate the lose sihcon tetrafluoride by sublimation. The addition of potassium carbonate or chloride to the fusion mix further reduces this tendency and promotes completion of the reaction. The reaction is conducted in a rotary furnace operating at 700°C. The product is cmshed prior to leaching with acidified hot water. The hot slurry is filtered to remove the sihca, and potassium hexafluorozirconate crystallizes as the solution cools. 

Seawater. Salt extraction from seawater is done by most countries having coastlines and weather conducive to evaporation. Seawater is evaporated in a series of concentration ponds until it is saturated with sodium chloride. At this point over 90% of the water has been removed, and some impurities, CaSO and CaCO, have been crystallized. This brine, now saturated in NaCl, is transferred to crystallizer ponds where salt precipitates on the floor of the pond as more water evaporates. Brine left over from the salt crystallizers is called bitterns because of its bitter taste. Bitterns is high in MgCl2, MgSO, and KCl. In some isolated cases, eg, India and China, magnesium and potassium compounds have been commercially extracted, but these represent only a small fraction of total world production. 

Economic Aspects and Uses. Total world production of potassium products is 29,000,000 tons per year (65). Potassium chloride is removed from brine at Moab, and Wendover, Utah, and at Seades Lake, California. Potassium sulfate is made from Great Salt Lake brine by Great Salt Lake Minerals Corp., which is the largest producer of solar potassium sulfate in the wodd. Combined, these U.S. faciUties stiU produce a relatively small percentage of potash fertilizers in the wodd. Production from the Dead Sea, for example, is 10 times greater than production of potassium from brines in the United States. More than 95% of all the potassium produced is used in fertilizer blends. The remainder is converted to other potassium chemicals for industdal use (see Potassium compounds). 

Thermodynamic data show that the stabilities of the caesium chloride-metal chloride complexes are greater than the conesponding sodium and potassium compounds, and tire fluorides form complexes more readily tlrair the chlorides, in the solid state. It would seem that tire stabilities of these compounds would transfer into tire liquid state. In fact, it has been possible to account for the heats of formation of molten salt mixtures by the assumption that molten complex salts contain complex as well as simple anions, so tlrat tire heat of formation of the liquid mixtures is tire mole fraction weighted product of the pure components and the complex. For example, in the CsCl-ZrCU system the heat of formation is given on each side of tire complex compound composition, the mole fraction of the compound... 

NH3 Naphth2). If sodium is used in place of potassium, the product detonates as crystallisation starts. This is attributed to energetic expulsion of ammonia held endothermically in the growing crystal lattice. The same also occurs with anthracene and sodium, and nitrobenzene and barium. Caution in preparing and using these compounds is urged. 

These nitridooxophosphates are stable in water and 1 N HC1, which is useful to extract eventual by-products. Their composition has been undoubtedly established by a complete chemical analysis. The XRD powder patterns can be indexed with hexagonal parameters (Z = 6) as illustrated for the potassium compounds ... 

The potassium compound 19 is readily transformed into 20 (R = alkyl) by the action of alkyl halides. The products are converted into salts of alkylamines RNH2 by acidic hydrolysis50. Uses of di-t-butyl imidodicarboxylate (21) have been reviewed46. Treatment of formamide with di-t-butyl dicarbonate 22 gives the unstable formyl compound 23, which yields 21 by the action of 2-diethylaminoethylamine (equation 18)51. 

The production of n-butylbenzene may be attributed to an inherent lack of complete selectivity in carbanion reactions, because the greater stability of an intermediate does not exclude the formation of the less stable product. This stability is only important when the step in forming intermediates is slow or when energy differences are large. On the other hand, the formation of n-butylbenzene from toluene and propylene may be due to a partial radical character of benzyl alkali metals. The latter would not seem to be the case because the potassium compounds should have greater ionic character, but they yield more n-butylbenzene. This agrees with the idea that lack of selectivity may be due to greater rate of reaction of potassium compounds with olefins. 

Potassium bromide also can be prepared by treating iron turnings with a 35 wt% aqueous solution of bromine. The product ferrosoferric bromide is boded in potassium carbonate solution containing a slight excess of 15% potassium carbonate (Dancy, W.B. 1980. Potassium Compounds. In Kirk-Othmer Encyclopedia of Chemical Technology, 3 i ed. p. 963. New York Wiley Interscience). The method does not involve bromate formation. The second step of the process may be represented in the foUowing reaction ... 

Potassium nitrate may be produced by several methods. It is made commercially by reacting potassium chloride with nitric acid at high temperature. Nitrosyl chloride, a product obtained in the reaction, is converted into chlorine in this manufacturing process. Also, nitric acid is partly recycled in the process. The reactions are (Dancy, W.B. 1981. Potassium Compounds. In Kirk-Othmer Encyclopedia of Chemical Technology, 3 i ed. Pp. 939-42. New York Whey Interscience) ... 

The metallic character of the cation-deficient partially oxidized tetracyano-platinate complexes is of considerable interest because of their unusual anisotropic electrical properties. The method used in the preparation of these compounds is a modification of the procedure used by Levy1 and gives a higher yield of pure product than the syntheses previously described in the literature2 5 (only the potassium compound has been reported to date). 

In the latter half of the nineteenth centuiy the United States was dependent on the vast Stassfurt deposits of Germany for the potassium compounds needed as fertilizers. In 1911 Congress appropriated funds for a search for domestic minerals, salts, brines, and seaweeds suitable for potash production (67). The complex brines of Searles Lake, California, a rich source of potassium chloride, have been worked up scientifically on the basis of phase-rule studies with outstanding success. Oil drillers exploring the Permian Basin for oil became aware of the possibility of discovering potash deposits through chemical analysis of the cores of saline strata. A rich bed of sylvinite, a natural mixture of sylvite (potassium chloride) and halite (sodium chloride), was found at Carlsbad, New Mexico. At the potash plane near Wendover, Utah, the raw material, a brine, is worked up by solar evaporation (67). 

Although the isomerization H2C=CHGsCNR2 - HC=CCH=CHNR2 can be brought about with catalytic amounts of r-BuOK in HMPT or DMSO [185], the procedure below is more satisfactory because aqueous work-up of the water-sensitive products can be avoided. The potassium amide is consumed in the conversion into the slightly soluble potassium compound of the ynene amine. We therefore presume that an equivalent amount of KNH2 is required for a complete conversion of the starting compound. 

While the polyarsenates and arsenatophosphates of lithium and sodium are closely related to the corresponding polyphosphates, the relationship is more complicated for the potassium compounds. The dehydration product of KH2As04 which is formed above about 180°C (122) has the analytical composition (KAsOa) and exists in three forms (121, 298). 

Fertilizers - [AMMONIA] (Vol2) -in bioremediation piOREMEDIATION] (Supplement) -blended [POTASSIUM COMPOUNDS] (Vol 19) -boron in [BORON COMPOUNDS - BORON OXIDES, BORIC ACID AND BORATES] (Vol 4) -cyanamidein [CYANAMIDES] (Vol 7) -lecithin in [LECITHIN] (Vol 15) -molybdenum compounds m [MOLYBDENUM AND COMPOUNDS] (Vol 16) -nitric acid m mfg [NITRIC ACID] (Vol 17) -potassium hydroxide mmfg of [POTASSIUM COMPOUNDS] (Vol 19) -radioactive tracers for [RADIOACTIVE TRACERS] (Vol 20) -role of H2 m production of [HYDROGEN] (Vol 13) -specialty liquid [POTASSIUM COMPOUNDS] (Vol 19) -tanks for [TANKS AND PRESSURE VESSELS] (Vol 23) -use of diatomite m [DIATOMITE] (Vol 8) -use of sulfur for [SULFUR] (Vol 23)... 

The reaction of silole 44 with KH in THF or DME yields, after work-up with D2O, quantitatively the corresponding deuteriated silole (equation 52) metalated siloles have been suggested as intermediates80. In contrast, the analogous treatment of silole 45 with KH yields a mixture of three NMR spectroscopically characterized potassium compounds (equation 53). The main product of this reaction is the pentavalent silicate 46, which results from the nucleophilic attack of a hydride at the silicon center109. The other two products result from hydride addition to one of the ring carbons. 

Reactions on or close to solid surfaces maybe inhibited by deposition ofinsoluble or poorly soluble products on the reactant surface, a phenomenon referred to as overgrowth. Examples include the reaction of amines with chloranil [7], the diazotisation of poorly soluble aromatic amines in which the product diazonium salt is also insoluble and halogen exchange reactions of chloroaromatic compounds using potassium fluoride in dipolar aprotic solvents where the potassium chloride product may coat the potassium fluoride [8]. 

The nature of the counter ion and the solvent medium is also significant as these additions are reversible. The terminal adduct is thermodynamically the more stable, and the initial product mixture can in some cases be converted to it. Thus the zinc and lithium derivatives rearrange on prolonged heating in thf or thf-HMPA (91). The more ionic potassium compounds, however, which can be obtained by addition of potassium hydride, isomerize rapidly, especially in the presence of crown ethers and in polar solvents (92,93) [Eq. (4)]. 

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