Boric acid production

Entry Diene R of boric acid Product yield [%] % ee (confign)... 

Boric acid production Sugar processing and refining... 

Male workers engaged in boric acid production showed weakened sexual activity, decreased seminal volume, low sperm count and motility, and increased seminal fructose. Animal studies demonstrated that the testes atrophy or degenerate if large amounts of boron are eaten or drunk these effects have not been reported in humans. Adverse effects on reproduction of laboratory animals have been reported in sensitive species fed diets... 

Boron trichloride, BCI3. Colourless mobile liquid, m.p. — 107°C, b.p. 12-5°C. Obtained directly from the elements or by heating B2O3 with pels in a sealed tube. The product may be purified by distillation in vacuo. It is extremely readily hydrolysed by water to boric acid. TetrachJoroborates containing the BCJ4 " ion are prepared by addition of BCI3 to metal chlorides. 

Boric acid is also an important boron compound with major markets in textile products. Use of borax as a mild antiseptic is minor in terms of dollars and tons. Boron compounds are also extensively used in the manufacture of borosilicate glasses. Other boron compounds show promise in treating arthritis. 

Secondary alcohols (C q—for surfactant iatermediates are produced by hydrolysis of secondary alkyl borate or boroxiae esters formed when paraffin hydrocarbons are air-oxidized ia the presence of boric acid [10043-35-3] (19,20). Union Carbide Corporation operated a plant ia the United States from 1964 until 1977. A plant built by Nippon Shokubai (Japan Catalytic Chemical) ia 1972 ia Kawasaki, Japan was expanded to 30,000 t/yr capacity ia 1980 (20). The process has been operated iadustriaHy ia the USSR siace 1959 (21). Also, predominantiy primary alcohols are produced ia large volumes ia the USSR by reduction of fatty acids, or their methyl esters, from permanganate-catalyzed air oxidation of paraffin hydrocarbons (22). The paraffin oxidation is carried out ia the temperature range 150—180°C at a paraffin conversion generally below 20% to a mixture of trialkyl borate, (RO)2B, and trialkyl boroxiae, (ROBO). Unconverted paraffin is separated from the product mixture by flash distillation. After hydrolysis of residual borate esters, the boric acid is recovered for recycle and the alcohols are purified by washing and distillation (19,20). 

Borolane products of mixed composition can be synthesized by direct addition of boric acid to pentaerythritol (23). 

Boron trifluoride [7637-07-2] (trifluoroborane), BF, was first reported in 1809 by Gay-Lussac and Thenard (1) who prepared it by the reaction of boric acid and fluorspar at duU red heat. It is a colorless gas when dry, but fumes in the presence of moisture yielding a dense white smoke of irritating, pungent odor. It is widely used as an acid catalyst (2) for many types of organic reactions, especially for the production of polymer and petroleum (qv) products. The gas was first produced commercially in 1936 by the Harshaw Chemical Co. (see also Boron COMPOUNDS). 

Cyclohexane. The LPO of cyclohexane [110-82-7] suppUes much of the raw materials needed for nylon-6 and nylon-6,6 production. Cyclohexanol (A) and cyclohexanone (K) maybe produced selectively by using alow conversion process with multiple stages (228—232). The reasons for low conversion and multiple stages (an approach to plug-flow operation) are apparent from Eigure 2. Several catalysts have been reported. The selectivity to A as well as the overall process efficiency can be improved by using boric acid (2,232,233). K/A mixtures are usually oxidized by nitric acid in a second step to adipic acid (233) (see Cyclohexanol and cyclohexanone). 

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. 

Wa.terBa.la.nce Chemicals. Water balance chemicals include muriatic acid, sodium bisulfate, and soda ash for pH control, sodium bicarbonate for alkalinity adjustment, and calcium chloride for hardness adjustment. A recent development is use of buffering agents for pH control. One of these products, sodium tetraborate, hydrolyzes to boric acid and a small amount of orthoborate (50) which provides significantly less buffering than carbonate and cyanurate alkalinity in the recommended pool pH range of 7.2—7.8 even at 100 ppm. 

Lower Oxides. A number of hard, refractory suboxides have been prepared either as by-products of elemental boron production (1) or by the reaction of boron and boric acid at high temperatures and pressures (39). It appears that the various oxides represented as B O, B O, B22O2, and B23O2 may all be the same material ia varying degrees of purity. A representative crystalline substance was determined to be rhombohedral boron suboxide, B12O2, usually mixed with traces of boron or B2O3 (39). A study has been made of the mechanical properties of this material, which exhibits a hardness... 

When boric acid is made from colemanite, the ore is ground to a fine powder and stirred vigorously with diluted mother Hquor and sulfuric acid at about 90°C. The by-product calcium sulfate [7778-18-9] is removed by settling and filtration, and the boric acid is crystallised by cooling the filtrate. 

Boric acid crystals are usually separated from aqueous slurries by centrifugation and dried in rotary driers heated indirecdy by warm air. To avoid overdrying, the product temperature should not exceed 50°C. Powdered and impalpable bode acid are produced by milling the crystalline matedal. 

Other Sodium Borates. SOLUBOR, TIM-BOR, or POLYBOR (63), proprietary products of United States Borax Chemical Corp., have the approximate composition of disodium octaborate tetrahydrate, Na20 4320 4H2O. This material is produced by spray-drying mixtures of borax and boric acid. 

Whereas there is no commercial production of sodium pentaborate pentahydrate, the compound can be prepared by crystallizing a borax-boric acid solution having a Na20 B202 mol ratio of 0.2. 

Decahydrate, Pentahydrate, and Anhydrous Borax and Bulk Calcium Borates. The bulk borate products, borax decahydrate and pentahydrate, anhydrous borax, boric acid and oxide, and upgraded colemanite and ulexite, account in both toimage and monetary terms for over 99% of sales of the boron primary products industry (6). Economic considerations for all these products are highly interrelated, and most production and trade statistics do not distinguish the various products. 

In 1986, Turkey produced nearly one million metric tons of mineral concentrate, whereas production of refined borate chemicals was 89,500 metric tons. Annual production capacities of chemicals at Eskiseher were pentahydrate borax, 160,000 t anhydrous borax, 60,000 t and decahydrate borax, 17,000 t. Capacities at Bandermes were decahydrate borax, 55,000 t boric acid, 33,000 t and sodium perborate, 64,000 t (103). 

Ammonium tetraborate tetrahydrate is prepared by crystallization from an aqueous solution of boric acid and ammonia having a B202 (NH4)20 ratio of 1.8 2.1. Ammonium pentaborate is similarly produced from an aqueous solution of boric acid and ammonia having a B202 (NH4)20 ratio of 5. Supersaturated solutions are easily formed and the rate of crystallization is proportional to the extent of supersaturation (130). A process for the production... 

In general, hydrated borates of heavy metals ate prepared by mixing aqueous solutions or suspensions of the metal oxides, sulfates, or halides and boric acid or alkali metal borates such as borax. The precipitates formed from basic solutions are often sparingly-soluble amorphous soHds having variable compositions. Crystalline products are generally obtained from slightly acidic solutions. 

From Boric Oxide and Alcohol. To avoid removing water, boric oxide, B2O3, can be used in place of boric acid. The water of reaction (eq. 4) is consumed by the oxide (eq. 5). Because boric acid reacts with borates at high temperatures, it is necessary to filter the reaction mixture prior to distillation of the product. Only 50% of the boron can be converted to ester by this method. In cases where this loss can be tolerated, the boric oxide method is convenient. This is particularly tme for methyl borate and ethyl borate preparation because formation of the undesirable azeotrope is avoided. 

Methyl borate is beheved to be the boric acid ester produced in the largest quantity, approximately 8600 metric tons per year (28). Most methyl borate is produced by Morton International and used captively to manufacture sodium borohydride [16940-66-2]. Methyl borate production was studied in detail during the 1950s and 1960s when this compound was proposed as a key intermediate for production of high energy fuels. Methyl borate is sold as either the pure compound or as the methanol azeotrope that consists of approximately a 1 1 molar ratio of methanol to methyl borate. 

---