Phosphorous fluorides

Phosphor) Fluoridate Bis-[2-lluuro-ctliyl]- ElOa. 50 (Toxicity)... 

DOT Label Poison Gas, UN 2198 Formula PF5 MW 125.97 CAS [7647-19-0] Synonyms phosphoric fluoride pentafluo-rophosphorane... 

The P—F group gives rise to absorption at 835-720 cm for phosphor-fluoridate salts.Organic phosphorus-fluorine compounds absorb at 890-805 cm for pentavalent phosphorus. 

Environmentally sound phosphate fertilizer plants recover as much of the fluoride value as H2SiFg as possible. Sales for production of AIF. -3H20 is one of the most important markets (see Fertilizers Phosphoric acid and the phosphates). 

The large amount of fluorine values released from phosphate rock in the manufacture of fertilisers (qv) gives a strong impetus to develop fluorine chemicals production from this source (see Phosphoric acid and the phosphates). Additional incentive comes from the need to control the emission of fluorine-containing gases. Most of the fluorine values are scmbbed out as fluorosiUcic acid, H2SiPg, which has limited useflilness. A procedure to convert fluorosihcic acid to calcium fluoride is available (61). 

Alternative Processes. Because of the large quantity of phosphate rock reserves available worldwide, recovery of the fluoride values from this raw material source has frequently been studied. Strategies involve recovering the fluoride from wet-process phosphoric acid plants as fluosiUcic acid [16961-83-4] H2SiFg, and then processing this acid to form hydrogen fluoride. 

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). 

Difluorophosphates. Difluorophosphates have limited appHcations largely because of hydrolytic instabiHty of the P03F 2 ion. The ammonium salt can be prepared from ammonium fluoride and phosphoric anhydride. 

Lead shows excellent resistance to phosphoric and sulfuric acid in almost all concentrations and at elevated temperatures, as well as to sulfide, sulfite, and sulfate solutions. The corrosion film is insoluble lead sulfate which rapidly reforms if it is damaged. Lead is also resistant to chlorides, fluorides, and bromates at low concentrations and low temperatures. However, because lead is soluble in nitric and acetic acids, it is not resistant to these acids. 

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). 

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. 

Aluminum fluoride is also made by the reaction of fluosiUcic acid [16961 -83-4] H2SiFg, a by-product from phosphoric acid production (see Phosphoric ACID AND THE PHOSPHATES), and aluminum hydroxide from the Bayer process. 

The vapor-phase conversion of aniline to DPA over a soHd catalyst has been extensively studied (18,22). In general, the catalyst used is pure aluminum oxide or titanium oxide, prepared under special conditions (18). Promoters, such as copper chromite, nickel chloride, phosphoric acid, and ammonium fluoride, have also been recommended. Reaction temperatures are usually from 400 to 500°C. Coke formed on the catalyst is removed occasionally by burning. In this way, conversions of about 35% and yields of 95% have been reported. Carba2ole is frequently a by-product. 

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. 

Cadmium Fluoride. Elemental fluorine reacts with cadmium metal as well as the oxide, sulfide, and chloride to give CdF2 [7790-79-6]. Alternatively, treatment of CdCO with 40% HF yields a solution of CdF2, which may be evaporated to recover efflorescent crystals of the dihydrate. CdF2 has been used in phosphors, glass manufacture, nuclear reactor controls, and electric bmshes and in 1991 sold as a pure electronic grade (99.99%) at l/g. 

Phosphoric Elemental phosphorus Particulate matter, fluorides Baghouse... 

Hot oleum (>50°C), strong alkalis, fluoride solutions, sulphur trioxide Strong alkalis, especially >54°C, distilled water >82°C, hydrofluoric acid, acid fluorides, hot concentrated phosphoric acid, lithium compounds >1 77°C, severe shock or impact applications Strong oxidizers, very strong solvents... 

Fluor-jod, n. iodine fluoride, -kalium, n. potassium fluoride, -kalzium, n. calcium fluoride, -kiesel, m. silicon fluoride, -kie-selsaure,/. fluosilicic acid, -kohlenstoff, m. carbon fluoride, -lithium, n. lithium fluoride. -metall, n. metallic fluoride, -natrium, n. sodium fluoride, -phosphat, n. fluophosphate. -phosphor, m. phosphorus fluoride, -salz, n. fluoride, -schwefel, m. sulfur fluoride, -selen, n. selenium fluoride, -silber, n. silver fluoride, -silikat, n. fluo-silicate. -silizium, n. silicon fluoride, -sili-ziumverbindung, /. fluosilicate. -tantal-sMure, /. fluotantalic acid, -tellur, n. tellurium fluoride, -titan, n. titanium fluoride, -toluol, n. fluorotoluene, fluotoluene. 

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