Boron phosphate

The tertiary metal phosphates are of the general formula MPO where M is B, Al, Ga, Fe, Mn, etc. The metal—oxygen bonds of these materials have considerable covalent character. The anhydrous salts are continuous three-dimensional networks analogous to the various polymorphic forms of siHca. Of limited commercial interest are the alurninum, boron, and iron phosphates. Boron phosphate [13308-51 -5] BPO, is produced by heating the reaction product of boric acid and phosphoric acid or by a dding H BO to H PO at room temperature, foUowed by crystallization from a solution containing >48% P205- Boron phosphate has limited use as a catalyst support, in ceramics, and in refractories. 

The alkylation of pyridine [110-86-1] takes place through nucleophiUc or homolytic substitution because the TT-electron-deficient pyridine nucleus does not allow electrophiUc substitution, eg, Friedel-Crafts alkylation. NucleophiUc substitution, which occurs with alkah or alkaline metal compounds, and free-radical processes are not attractive for commercial appHcations. Commercially, catalytic alkylation processes via homolytic substitution of pyridine rings are important. The catalysts effective for this reaction include boron phosphate, alumina, siHca—alurnina, and Raney nickel (122). 

A number of boron chemicals are prepared directly from boric acid. These include synthetic inorganic borate salts, boron phosphate, fluoborates, boron ttihaHdes, borate esters, boron carbide, and metal aHoys such as ferroboron [11108-67-1]. 

Boron phosphate, BPO, is a white, infusible soHd that vapori2es slowly above 1450°C, without apparent decomposition. It is normally prepared by dehydrating mixtures of boric acid and phosphoric acid at temperatures up to 1200°C. 

The stmcture of boron phosphate prepared under normal atmospheric conditions consists of tetragonal bipyrimids analogous to the high cristobahte form of siUca. Both the boron and phosphoms are tetrahedraHy coordinated by oxygen. Similar siUcalike stmctures ate found for BAsO and TaBO (156). A quart2like form of boron phosphate can be prepared by heating the common form to 500°C at 5.07 GPa (50,000 atm) (157). 

The tri-, tetra-, penta-, and hexahydrates of boron phosphate have been reported. AH of these decompose rapidly in water to give solutions of the parent acids. Anhydrous boron phosphate hydroly2es in a similar fashion, though the reaction proceeds quite slowly for material that has been ignited at high temperatures. 

The principal appHcation of boron phosphate has been as a heterogeneous acid catalyst (158). 

Although boron phosphate is derived from two of the three most common glass-forming oxides, it exhibits Htde tendency to form a glass itself. Boron phosphate is a primary phase over a considerable portion of the B2O2—Si02—P20 system (159). 

In a typical process adiponitrile is formed by the interaction of adipic acid and gaseous ammonia in the presence of a boron phosphate catalyst at 305-350°C. The adiponitrile is purified and then subjected to continuous hydrogenation at 130°C and 4000 Ibf/in (28 MPa) pressure in the presence of excess ammonia and a cobalt catalyst. By-products such as hexamethyleneimine are formed but the quantity produced is minimized by the use of excess ammonia. Pure hexamethylenediamine (boiling point 90-92°C at 14mmHg pressure, melting point 39°C) is obtained by distillation, Hexamethylenediamine is also prepared commercially from butadience. The butadiene feedstock is of relatively low cost but it does use substantial quantities of hydrogen cyanide. The process developed by Du Pont may be given schematically as ... 

See also Borates Boric acid Sodium borates boron oxides, 4 246-249 boron oxides table,4 242t environmental concerns, 4 284—285 health and safety factors, 4 285-288 occurrence, 4 245—246 Boron perchlorates, 18 278 Boron phosphate, 4 242t, 283 Boron removal, from water, 14 418 Boron-stabilized carbanions, 13 660-661 Boron subhalides, 4 141 Boron suboxide, 4 242t Boron tribromide, 4 138 manufacture, 4 145—146 physical properties of, 4 139-140t, 325 reactions, 4 141 specifications, 4 147t uses of, 4 149 Boron trichloride, 4 138 manufacture, 4 145—146 physical properties of, 4 139-140t reactions, 4 141... 

Adipic acids gets converted to adiponitrile on treatment with NH3 at 350-450°C in presence of boron phosphate catalyst. Hydrogenation of adiponitrile can be done in presence of NH3 to Organisation and Qualities... 

Boron phosphate is used as an acid catalyst for dehydration of alcohols to olefins isomemization of olefins nitration of aromatic hydrocarbons polymerization of aldehydes and other synthetic reactions. It also is used as a flux in silica-based porcelain and ceramics special glasses and acid cleaners. 

Boron phosphate is prepared by heating an equimolar mixture of boric acid and phosphoric acid at 1,000 to 1,200°C ... 

Various preparative methods are adopted at nonstoichiometric formulations, incomplete dehydration or using oxide additives to obtain boron phosphate of varying purity for its catalytic applications. The compound also forms hydrates (tri- tetra-, penta-, and hexahydrates) which readily decompose in water to phosphoric acid and boric acid. 

As in the synthesis of other bipyridines, several routes to 4,4 -bipyridine have been devised where one of the pyridine rings is built up from simpler components. For example, a dimer of acrolein reacts with ammonia and methanol in the presence of boron phosphate catalyst at 350°C to give a mixture of products including 4,4 -bipyridine (3.4% yield), and in a reaction akin to ones referred to with other bipyridines, 4-vinylpyridine reacts with substituted oxazoles in the presence of acid to give substituted 4,4 -bipyridines. ° ° Condensation of isonicotinaldehyde with acetaldehyde and ammonia at high temperatures in the presence of a catalyst also affords some 4,4 -bipyridine, and related processes give similar results,whereas pyran derivatives can be converted to 4,4 -bipyridine (56% conversion), for example, by reaction with ammonia and air at 350°C with a nickel-alumina catalyst. Likewise, 2,6-diphenyl-4-(4-pyridyl)pyrylium salts afford 2,6-... 

Boron phosphate is vigorously decomposed by hot concentrated alkali to give sodium borate and phosphate. For... 

E. D. Chattaway and H. P. Stevens found that phosphoric acid decomposes nitrogen iodide, producing ammonia. According to A. Geuther, when phosphoric acid is treated with phosphorus pentachloride at ordinary temp., phosphoryl chloride and hydrogen chloride are formed phosphorus trichloride furnishes meta-phosphoric and phosphorous acids and phosphoryl chloride is without action in the cold, but when hot, metaphosphoric acid is formed if the phosphoryl chloride be in excess, and phosphorous acid if only a little be present. G. Meyer, and A. Vogel prepared a complex with boric oxide or boric acid—vide boron phosphate, 5. 32, 27. 

Moffat and Neeleman (139) investigated the adsorption of ammonia on boron phosphate by means of infrared spectroscopy. Ammonia appear to dissociate on this solid. Although absorption bands arising from NH4+ and coordinated ammonia were obtained, the authors feel that the presence of NH + does not necessarily indicate that Br0nsted sites were initially present on the BP04 surface. Hydroxyl groups that might be formed when ammonia dissociates could react with dry ammonia to form NHi+. 

Attempted catalysis. A number of experiments were carried out to test the possible catalytic activity of substances such as potassium carbonate, cupric carbonate, ammonium chloride, ammonium sulfate, potassium silicate, boron phosphate, and silica gel, but in no case was there any indication that the reaction could be catalyzed. 

Boron compounds such as borax and boric acid are well-known fire retardants in cellulosic products and coatings.12 However, the use of boron compounds such as zinc borate, ammonium pent-aborate (APB), melamine borate, boric oxide, boron phosphate, and other metal borates in polymers has become prominent only since early 1980s.3 6 This chapter will review the chemical and physical properties, the end-use applications, as well as the mode of actions of major boron compounds as fire retardants in different applications. Since boron-based flame retardants are extensively used and quoted in literature, only those formulations of commercial importance and representative literature examples will be discussed and/or cited in this chapter. 

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