Phosphoric acid CAS

Phosphoric acid (CAS 7664-38-2) A strong corrosive add severe burns may result trom direct contact. Mist orvapors irritating to eyes and respiratory tract. 

Bis [2,4-bis (1,1-dimethylethyl)-6-methylphenyl] ethyl ester, phosphorous acid CAS 145650-60-8... 

Chemistry and Properties. TSP is essentially impure monocalcium phosphate monohydrate, Ca(H2P0 2 20, made by acidulating phosphate rock with phosphoric acid according to... 

The ores of most importance are fluorspar, CaF2 fluorapatite, Ca (P0 2Fj cryoHte [15096-52-3], Na AlF. Fluorspar is the primary commercial source of fluoiine. Twenty-six percent of the world s high quaHty deposits of fluorspar are ia North America. Most of that is ia Mexico. United States production ia 1987—1991 was 314,500 metric tons, most of which occurred ia the Illinois-Kentucky area. Imported fluorspar ia 1990—1991 represented about 82% of U.S. consumption 31% of U.S. fluorspar imports were from Mexico and 29% from China compared to 66% from Mexico ia the 1973—1978 period. The majority of the fluorine ia the earth s cmst is ia phosphate rock ia the form of fluorapatite which has an average fluorine concentration of 3.5%. Recovery of these fluorine values as by-product fluorosiHcic acid from phosphate production has grown steadily, partially because of environmental requirements (see Phosphoric acid and THE phosphates). 

The majority of the fluorine ia the earth s cmst is present in the form of the phosphoms fluoride fluoroapatite [1306-05 ] Ca (P0 2F- Phosphate rock deposits contain an average concentration of 3.5 wt % fluorine. During phosphate processing these fluorine values are partially recovered as by-product fluorosihcic acid. The amount of fluorosiUcic acid recovered has grown steadily, in part because of environmental requirements (see Phosphoric acid and THE phosphates). 

The methyl a-hydroxyisobutyrate produced is dehydrated to MMA and water in two stages. First, the methyl a-hydroxyisobutyrate is vaporized and passed over a modified zeoHte catalyst at ca 240°C. A second reactor containing phosphoric acid is operated at ca 150°C to promote esterification of any methacrylic acid (MAA) formed in the first reactor (74,75). Methanol is co-fed to improve selectivity in each stage. Conversions of methyl a-hydroxyisobutyrate are greater than 99%, with selectivities to MMA near 96%. The reactor effluent is extracted with water to remove methanol and yield cmde MMA. This process has not yet been used on a commercial scale. 

Phosphorus. Eighty-five percent of the phosphoms, the second most abundant element in the human body, is located in bones and teeth (24,35). Whereas there is constant exchange of calcium and phosphoms between bones and blood, there is very Httle turnover in teeth (25). The Ca P ratio in bones is constant at about 2 1. Every tissue and cell contains phosphoms, generally as a salt or ester of mono-, di-, or tribasic phosphoric acid, as phosphoHpids, or as phosphorylated sugars (24). Phosphoms is involved in a large number and wide variety of metaboHc functions. Examples are carbohydrate metaboHsm (36,37), adenosine triphosphate (ATP) from fatty acid metaboHsm (38), and oxidative phosphorylation (36,39). Common food sources rich in phosphoms are Hsted in Table 5 (see also Phosphorus compounds). 

Ghloromethylation. The reactive intermediate, 1-chloromethylnaphthalene [86-52-2] has been produced by the reaction of naphthalene in glacial acetic acid and phosphoric acid with formaldehyde and hydrochloric acid. Heating of these ingredients at 80—85°C at 101.3 kPa (1 atm) with stirring for ca 6 h is required. The potential ha2ard of such chloromethylation reactions, which results from the possible production of small amounts of the powerhil carcinogen methyl chloromethyl ether [107-30-2J, has been reported (21). 

Isopropylnaphthalenes can be prepared readily by the catalytic alkylation of naphthalene with propjiene. 2-lsopropylnaphthalene [2027-17-0] is an important intermediate used in the manufacture of 2-naphthol (see Naphthalenederivatives). The alkylation of naphthalene with propjiene, preferably in an inert solvent at 40—100°C with an aluminum chloride, hydrogen fluoride, or boron trifluoride—phosphoric acid catalyst, gives 90—95% wt % 2-isopropylnaphthalene however, a considerable amount of polyalkylate also is produced. Preferably, the propylation of naphthalene is carried out in the vapor phase in a continuous manner, over a phosphoric acid on kieselguhr catalyst under pressure at ca 220—250°C. The alkylate, which is low in di- and polyisopropylnaphthalenes, then is isomerized by recycling over the same catalyst at 240°C or by using aluminum chloride catalyst at 80°C. After distillation, a product containing >90 wt % 2-isopropylnaphthalene is obtained (47). 

Phosphoric acids and the phosphates maybe defined as derivatives of phosphoms oxides where the phosphoms atom is in the +5 oxidation state. These are compounds formed in the M2O—P20 system, where M represents one cation equivalent, eg, H", Na", 0.5 Ca ", etc. The molecular formula of the phosphoms(V) oxide [1314-56-3] is actually P O q, but this oxide is commonly referred to in terms of its empirical formula, P2O5. StmcturaHy, four phosphoms—oxygen (P—O) linkages are arranged in an approximate tetrahedral configuration about the phosphoms atom in the phosphate anion. Compounds containing discrete, monomeric PO ions are known as orthophosphates or simply as phosphates. 

Elemental phosphoms from the electrothermal process is a distilled product of high purity and yields phosphoric acid pure enough for most industrial uses without any further treatment. The main impurity is ca 20—100 ppm arsenic present in the phosphoms as the element and in the phosphoric acid as arsenious acid. To remove the arsenic, the phosphoric acid destined for food, pharmaceutical, and some industrial-grade appHcations is treated with excess hydrogen sulfide, filtered, and blown with air to strip out excess H2S. This treatment generally reduces the arsenic content of the phosphoric acid to less than 0.5 ppm. The small amount of filter cake is disposed of in approved chemical landfills. 

Solvent extraction—purification of wet-process phosphoric acid is based on preferential extraction of H PO by an organic solvent vs the cationic impurities present in the acid. Because selectivity of acid over anionic impurities is usually not sufficient, precipitation or evaporation steps are included in the purification process for removal. Cmde wet-process acid is typically concentrated and clarified prior to extraction to remove post-precipitated sludge and improve partition of the acid into the solvent. Concentration also partially eliminates fluoride by evaporation of HF and/or SiF. Chemical precipitation of sulfate (as Ba or Ca salts), fluorosiUcates (as Na salt), and arsenic (as sulfides) may also be used as a prepurification step preceding solvent extraction. 

Tricalcium phosphate, Ca2(P0 2> is formed under high temperatures and is unstable toward reaction with moisture below 100°C. The high temperature mineral whidockite [64418-26-4] although often described as P-tricalcium phosphate, is not pure. Whidockite contains small amounts of iron and magnesium. Commercial tricalcium phosphate prepared by the reaction of phosphoric acid and a hydrated lime slurry consists of amorphous or poody crystalline basic calcium phosphates close to the hydroxyapatite composition and has a Ca/P ratio of approximately 3 2. Because this mole ratio can vary widely (1.3—2.0), free lime, calcium hydroxide, and dicalcium phosphate may be present in variable proportion. The highly insoluble basic calcium phosphates precipitate as fine particles, mosdy less than a few micrometers in diameter. The surface area of precipitated hydroxyapatite is approximately... 

Anhydrous monocalcium phosphate, Ca(H2PObe made in a pan mixer from concentrated phosphoric acid and lime. The high heat of reaction furnishes essentially all the necessary thermal input and subsequent drying is minimized. A small amount of aluminum phosphate or a mixture of sodium and potassium phosphates is added in the form of proprietary stabilizers for coating the particles. Heat treatment converts the coating to a protective polyphosphate (19). 

Phosphorus [7723-14-0] is a nonmetaUic element having widespread occurrence in nature as phosphate compounds (see Phosphoric acid and phosphates). Fluorapatite [1306-03-4], Ca F(P0 2> is the primary mineral in phosphate rock ores from which useful phosphoms compounds (qv) ate produced. The recovery from the ore into commercial chemicals is accompHshed by two routes the electric furnace process, which yields elemental phosphoms and the wet acid process, which generates phosphoric acid. The former is discussed herein (see Furnaces, electric). Less than 10% of the phosphate rock mined in the world is processed in electric furnaces. Over 90% is processed by the wet process, used primarily to make fertilisers (qv). 

About 264,000 metric tons of elemental capacity is available in North America, plus another 79,000 t (P equivalent) of purified wet phosphoric acid (14). About 85% of the elemental P is burned to P2 5 hydrated to phosphoric acid. Part of the acid (ca 21%) is used direcdy, but the biggest part is converted to phosphate compounds. Sodium phosphates account for 47% calcium, potassium, and ammonium phosphates account for 17%. Pinal apphcations include home laundry and automatic dishwasher detergents, industrial and institutional cleaners, food and beverages, metal cleaning and treatment, potable water and wastewater treatment, antifree2e, and electronics. The purified wet acid serves the same markets. 

Titanium corrodes very rapidly in acid fluoride environments. It is attacked in boiling HCl or H2SO4 at acid concentrations of >1% or in ca 10 wt % acid concentration at room temperature. Titanium is also attacked by hot caustic solutions, phosphoric acid solutions (concentrations >25 wt%), boiling AlCl (concentrations >10 wt %), dry chlorine gas, anhydrous ammonia above 150°C, and dry hydrogen—dihydrogen sulfide above 150°C. 

For solvent extraction of a tetravalent vanadium oxyvanadium cation, the leach solution is acidified to ca pH 1.6—2.0 by addition of sulfuric acid, and the redox potential is adjusted to —250 mV by heating and reaction with iron powder. Vanadium is extracted from the blue solution in ca six countercurrent mixer—settler stages by a kerosene solution of 5—6 wt % di-2-ethyIhexyl phosphoric acid (EHPA) and 3 wt % tributyl phosphate (TBP). The organic solvent is stripped by a 15 wt % sulfuric acid solution. The rich strip Hquor containing ca 50—65 g V20 /L is oxidized batchwise initially at pH 0.3 by addition of sodium chlorate then it is heated to 70°C and agitated during the addition of NH to raise the pH to 0.6. Vanadium pentoxide of 98—99% grade precipitates, is removed by filtration, and then is fused and flaked. 

Phosphates. The primary constituent of phosphate rock is fluorapatite, Ca3FP2022- Industrial phosphates including phosphate fertilizers (qv), phosphoric acid, and calcium phosphates (11) (see Phosphoric acid and the phosphates) are obtained from the large deposits of fluorapatite found in Florida in the United States, and in Morocco. Because phosphate rock is too insoluble to be useful as a fertilizer, it is converted to superphosphate [12431 -88-8] Ca(H2P0 2 CaSO, by H2SO and to triple superphosphate [7758-23-8] by H PO (l )- Phosphoric acid may also be... 

Monocalcium phosphate [10031-30-8] Ca(H2P0 2 H2O, used in baking powder (see Bakeryprocesses and leavening agents), is crystallized from a hot reaction mixture of concentrated (electric furnace) phosphoric acid and lime, or it is made by spray-drying a slurry of the product of reaction of lime and phosphoric acid (14). 

Phospha.tes, Pentasodium triphosphate [7758-29-4] sodium tripolyphosphate, STPP, Na P O Q, is the most widely used and most effective builder in heavy-duty fabric washing compositions (see also Phosphoric acid and phosphates). It is a strong sequestrant for calcium and magnesium, with a p c of ca 6, and provides exceUent suspending action for soils. Because of its high sequestration power, it also finds extensive appHcation in automatic-dishwashing detergents. Sodium tripolyphosphate forms stable hydrates and thus aids in the manufacture of crisp spray-dried laundry powders. 

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