DE1084251B - Process for the production of ammonium pentaborate from borax by converting borax and ammonium chloride in an aqueous phase - Google Patents

Description

A process for obtaining ammonium pentaborate from borax by reaction of borax and ammonium chloride in aqueous phase It is known winnen boric acid by the action of ammonium chloride solutions natural borates to overall by withdrawing cooking the appropriate calcined borates with ammonium chloride solution proportions of the liquid from this by switching off cool the boric acid deposits and returns the behind remaining mother liquor to the operation. The measure of separating the boric acid from part of the solution and recirculating the mother liquor served the purpose of reducing the boric acid concentration in the solution and thereby enabling the further course of the reaction in terms of the decomposition of the borates and ammonium chloride.

It has now been found, surprisingly, that by reaction from borax and ammonium chloride in an aqueous medium amniotic pentaborate is obtained if the mixture until the practically complete removal of what is formed in the reaction Distilled ammonia. The ammon pentaborate can then crystallize out of the mixture will. If desired, the ammonium pentaborate can then be thermally Convert decomposition into boron oxide.

If ammonium pentaborate is crystallized from the mixture in the manner that a mother liquor remains, the ammonium pentaborate and sodium chloride in solution contains, this mother liquor can be worked up by removing the sodium chloride and recirculate it to the process in order to add the ammonium pentaborate dissolved therein to win. For this purpose, the mother liquor is mixed with a lower saturated one aliphatic monohydric alcohol with 2 to 4 carbon atoms in the molecule, crystallizes Sodium chloride and the alcohol is distilled off from the mother liquor.

Ethyl alcohol is expediently used as the alcohol.

According to a preferred embodiment of the invention, the mother liquor is mixed with an ester of a lower saturated monocarboxylic acid and a lower saturated aliphatic monohydric alcohol, advantageously ethyl acetate, in amounts of up to 25 percent by weight of the alcohol in order to remove the sodium chloride. Example A three-necked flask of 1000 cc was used to convert borax into ammonium pentaborate, the central neck of which was equipped with a stirrer. A side neck was closed with a glass stopper. A simple distillation plant, which consisted of a distillation head, a condenser, a connecting pipe with a vacuum connection and a one-necked flask of 1000 ccm, was connected in series and inserted into the other side neck. A magnetic stirrer and standard acid to determine the ammonia developed were placed in the single-necked flask, which served as a template.

In cycle # I, 190.7 grams of borax (0.50 moles) and a 10 weight percent aqueous ammonium chloride solution (54.5 grams, 1.02 moles dissolved in 490.5 grams of water) were placed in the three-necked flask. The solution was heated; Ammonia and water were distilled off together at 98 to 100 ° C. in the receiver, which contained 100 cc of 6.025 N hydrochloric acid. The amount of acid in the receiver was 1 (Y, 2 g ammonia equivalent. When the color of the indicator of methylene blue and methyl red in the acid turned from purple to green, the distillation was stopped; the distillation of ammonia and water lasted about 1 Hour.

The solution remaining in the flask after the ammonia had been distilled off was cooled to 600 ° C. and further concentrated by passing a stream of air over it. After about a further 50 g of water had evaporated in this way, the solution became cloudy as a result of the formation of a white crystal precipitate. The slurry was stirred, cooled to OP C and filtered. The unwashed filter cake was dried in an oven at 90 ° C. The salt obtained was ammonium pentaborate; it showed the following analysis: 19.65 weight percent boron; 4.96 weight percent nitrogen; 31.02 weight percent H.0. The theoretical values for N H4 B, 5 08-4 H2 0 are 19.89 weight percent boron; 5.15 weight percent nitrogen; 26.46 weight percent water. 80 g of this product contained 1.3 g of sodium chloride. The crystallized ammonium pentaborate was recrystallized twice and filtered off from the mother liquor, which was concentrated by evaporation at 60 ° C. and cooled to 0 ° C. The twice recrystallized product was dried in an oven at 90 ° C. and analyzed; it contained 19.14 percent by weight boron, 4.87 percent by weight nitrogen and 26.08 percent by weight H2 0; the chloride content was negligible. If ammonium pentaborate was recrystallized with the exception that the recrystallization mother liquor at 100 'C concentrated by evaporation and 25' was cooled C, the analysis showed the twice-recrystallized salt 20, # 20 weight percent boron, 4.11 weight percent nitrogen; Chloride is negligible.

The filtration mother liquor was concentrated by passing air over it until about 75 cc of supernatant liquid remained above the salt mixture (ammon pentaborate and sodium chloride), which crystallized out on concentration. A solution of 450 cc of denatured alcohol and 50 cc of ethyl acetate was divided into two equal parts. The first 250 cem portion was added dropwise to the aqueous slurry with stirring; the resulting mixture was digested at 60 ° C. for 1/2 hour. The second portion of the alcohol-ester mixture of 250 ccm was then added, whereupon the slurry was cooled to 20 ° C. and filtered. The unwashed filter cake was dried in an oven at 110 ° C. The salt thus obtained was sodium chloride.

When using ethyl alcohol alone, the process proceeds in the same way under otherwise identical conditions. - - A sample of 0.865 g guskristallisiertein ammonium pentaborate was heated in a porcelain crucible at about 800 'C over a Meekerbrenner 2 hours and the glassy residue with hot water from the crucible washed out. After analysis, the aqueous solution contained 0.91 g of boric acid, 0.51 g of boron oxide equivalent. This corresponds to an uncorrected yield of 93 percent by weight boron oxide.

The denatured alcohol and ethyl acetate were obtained by distillation of the mother liquor remaining after the sodium chloride had been separated off at 78 to 82 ° C .; the distillate from alcohol and ester was used to precipitate sodium chloride in cycle II. The residue remaining after the alcohol and ethyl acetate had been distilled off contained sodium chloride and ammonium pentaborate; this residue was added to the reaction mixture, which remained after removal of ammonia from the reaction mixture borax-aminone chloride of cycle II. This procedure was repeated in five cycles. The results are compiled in the table. MolAm- . Cycle No. Mole monium- NH4B508 - 4H20 Borax dilorid (1007oH20) 1 purity yield 1 0.50 1.02 98.8% 72.011 / o 0.50 1.02 93.0 "/ o 98.3% 0.50 1.02 97.5% 98.9.1 / 0 IV 0.50 1.92 97.3 "/ o 100.5'Ofo V 0.50 1-. 02 100.0% 97.6 "/ o, The information in the example can be modified in various ways; thus the proportions of borax, ammonium chloride and water in the initial reaction mixture can be changed. As a guideline, it should be noted that about 2.0 to about 2.2 moles of ammonium chloride are used per mole of borax; the reaction mixture generally contains about 5 to 25 percent by weight of ammonium chloride, based on the weight of ammonium chloride and water.

To crystallize out sodium chloride, the reaction mixture is expediently mixed with one or more saturated aliphatic monohydric alcohols having 2 to 4 carbon atoms. Instead of the denatured alcohol according to the example, normal propyl alcohol, isopropyl alcohol, isobutyl alcohol, etc. can be used. The alcohol can be used alone or together up to about 25 percent by weight, based on the amount by weight of alcohol, of an ester of a lower saturated monocarboxylic acid and a lower saturated monohydric alcohol or an ester mixture. The esters are generally derived from acids with 1 to 3 carbon atoms and alcohols with 1 to 3 carbon atoms, such as methyl acetate, methyl propionate, ethyl propionate and the like, in addition to ethyl acetate according to the example.

Ammon pentaborate can be decomposed to boron oxide by simply heating to a higher temperature in the range from about 600 to 1000 ° C. by methods known per se.

The schematic drawing shows the continuous operation of the process according to the invention. To carry out the process, an aqueous solution of ammonium chloride and borax is fed continuously through line 1 into the reaction vessel 2. Steam and ammonia escape from the reaction vessel through line 3; the solution is withdrawn through line 4 into evaporator 5 , from which water vapor is removed through line 6. The liquid passes from the evaporator 5 through line 7 to the filter 8, which is used to separate the crystallized ammonium pentaborate from the mother liquor, which goes through line 9 to the settling tank 10. This is charged through line 11 with a mixture of denatured alcohol and ethyl acetate. The reaction mixture goes through line 12 to filter 13, where sodium chloride is separated off. The mother liquor obtained here goes via line 14 into column 15, from which denatured alcohol and ethyl acetate are drawn off via line 11 at the top. The residue flows through line 16 into the evaporator 5. The ammonium pentaborate separated by the filter 8 passes, expediently steadily, into the furnace 17, where it is split into water and ammonia vapor (line 18) and boron oxide (line 19).

Claims (1)

PATENT CLAIMS. 1. A process for obtaining ammonia pentaborate from borax by reacting borax and ammonium chloride in the aqueous phase, characterized in that all of the ammonia formed during the reaction is distilled off from the ammonia chloride-borax-water mixture and is removed from the distillation residue, if appropriate after concentration , the ammonium pentaborate crystallized and separated from the mother liquor. 2. Continuous implementation of the process according to claim 1, characterized in that the mother liquors obtained during the separation of the pentaborate are mixed with at least one saturated aliphatic monohydric alcohol containing 2 to 4 carbon atoms, in particular ethyl alcohol, and the crystallized NaCl of the mother liquor is separated off, the alcohol is distilled off from the latter and the residue is worked up to ammonium pentaborate, preferably in connection with the concentration according to claim 1 . 3. The method according to claim 2, characterized in that the mother liquor in addition to ethyl alcohol at least one ester of a lower saturated monocarboxylic acid and a lower saturated aliphatic monohydric alcohol, in particular ethyl acetate, is added, the ester content being up to 25 percent by weight of the alcohol. Considered publications: German Patent Specifications No. 110421, 136 181, 354528.