DE1128420B - Process for the preparation of boric acid alkyl esters - Google Patents

Description

Process for the preparation of boric acid alkyl esters The invention relates to a process for the preparation of boric acid alkyl esters from salts of boric acid.

Boron-containing, e.g. B. Borax containing ores are usually such processed so that an aqueous solution is made from the ore, the insoluble gangue filtered off and borax crystallized out. Alkyl borates are generally put through Reaction of boric acid or boron oxide with an alcohol such as methanol. This way of working is complicated by the fact that when separating the methyl borate from the azeotropic Difficulties occur when mixed with water and methanol. Other ores that do not have any Containing borax are first treated with an aqueous mineral acid and filtered; the boric acid is separated off by fractional crystallization. The quantitative Extraction of the boron content from ores by known processes has been economical up to now not feasible.

According to the method of the present invention, boron salts can be conveniently made practical can be converted quantitatively into alkyl borates. The new process avoids that with the regulated fractional crystallization and separation of the alkyl borates difficulties associated with the azeotropic mixtures with water and alcohol. The process makes use of cheap, readily available acidic substances. Primary the new process includes the use of a polyhydric alcohol Formation of high-boiling plastic polyborates by reaction with boron oxide and removal of water from the ore slurry prior to transesterification with a lower boiling point Alcohol to the desired alkyl borate. If boric acid is the desired end product, can be the azeotropic mixture of trimethyl borate and methanol, which according to one embodiment of the invention, are hydrolyzed; Boric acid is filtered off and Methanol recovered by distillation of the mother liquor for recycle.

The boric acid can then optionally by known methods in boron oxide be transferred. The present way of working is cheaper and easier to use available substances, which are largely recovered and used for further treatment Boron salt can be reused.

According to the present process one proceeds in such a way that one a mixture of sodium and / or calcium borate with a range of 175 Polyvalent, preferably divalent, boiling up to 375 "C at atmospheric pressure Alcohol with the addition of ammonium chloride or sodium bisulfate produces the mixture esterified to complete dehydration and the anhydrous mixture with a saturated aliphatic monohydric alcohol having 1 to 3 carbon atoms below Distilling off the boric acid ester formed transesterified.

It is known to combine boric acid with methyl alcohol and other aliphatic To esterify alcohols directly.

Furthermore, the production of lower alkyl borates is on the way higher alkyl borates known from alcoholysis; however, here are those as intermediates serving higher esters, esters of boric acid with monohydric alcohols, such as propyl alcohol, Isopropyl alcohol, butyl alcohol, amyl alcohol, and hexyl alcohol.

The essential feature of the present invention is alcoholysis by way of a boric acid ester of a polyhydric alcohol, which is in the area boils from 175 to 3750 C. In this esterification with a polyhydric alcohol The primary reaction products are high-boiling plastic polyborates, which complete esterification by driving off the water of reaction from the reaction mixture is made much easier.

The formation of high-boiling polymeric boric acid esters as intermediate products is therefore an essential procedural feature, which the complete course of the Implementation significantly simplified.

The following examples serve to illustrate the invention.

Example 1 This example illustrates a continuous process for the production of trimethyl borate, where one borax, ammonium chloride and ethylene glycol reacts with one another, water and ammonia by distillation overhead removed, methanol enters the reaction mixture and trimethyl borate overhead distilled off.

The device used for this consisted of a three-necked flask 1000 ml with a stirrer. A hopper was placed in one neck of the flask used. a short distillation column filled with glass beads, a changeable one The distillation head, a vacuum connector and a receiver were connected in series connected to another neck of the flask. A U-tube was attached to the vacuum leading outlet - connected; it contained a standardized acid solution during the Distillation of water and ammonia to measure the amount of ammonia released to determine which was not dissolved in the aqueous distillate.

A mixture of 95.4 g (0.25 moles) of borax, a granular reagent of a Grain size of about 0.3 mm from Merck & Co., 26.8 g (0.50 mol) of granular Ammonium chloride, reagent from Mallinckrodt, and 372 g (338 ml, 6.0 mol) of the commercially available Ethylene glycol from Carbide and Carbon Chemicals Co. was added to the flask. By adding 241 g of distilled water to the mixture, it became 10% aqueous Ammonium chloride solution, corresponding to that coming from an ammonia soda plant - the Lung; manufactured. After adding the water, stirring and heating continued a. The mixture was de - @@ ilated with water at 98 to 100 ° C. under atmospheric pressure and remove ammonia overhead. The removed water composed from (1) the additional water, (2) the crystal water from the ore, (3) the esterification water. After cooling the mixture to room temperature, 268 g (838 mol) were absolute Methanol entered. Thereafter, the mixture was stirred and heated to make the azeotropic Mixture of trimethyl borate and methanol (temperature 54 ° C) to be distilled off overhead. When the vapor temperature of the distillate reached 60 ° C, the distillation stopped canceled: Sodium chloride was then in the form of well-formed crystals from the The residue from glycol and methanol was easily removed by filtering off. Excess Methanol and residual trimethyl borate were filtered off from the filtrate of the residue and made available for further use; there remained glycol with some dissolved Sodium chloride.

The amount of glycol recovered was related in cycle II used with additional borax and aqueous ammonium chloride. For cycle II was Additional methanol is used to supplement the methanol that is produced from the glycol-methanol residue of cycle I was obtained by distillation.

Table I shows the test results for seven cycles; the moles are given in gramoles. Tabel Additive Additive Removed Formed Trimethylborate Ethylene glycol methanol cycle borax NH4Cl water NH3 NaCl (as azeotrope) No. Mole mole mole mole ml mole mole mole I 0.25 0.50 6.00 8.38 314 0.42 0.96 0.77 II 0.25 0.50 6.00 3.76 332 0.47 0.46 0.88 (Cycle) (supplemented) -III 0.25 0.50 6.00 5.00 330 0.44 0.41 0.93 (Cycle) (supplemented) IV 0.25 0.50 6.00 6.63 380 - 0.55 0.62 1.28 (Cycle) (supplemented) V 0.25 0.50 6.00 6.25 25 387 0.52 0.46 1.14 (Cycle) (supplemented) VI 0.25 0.50 6.00 8.13 355 0.51 0.50 0.97 (Cycle) (supplemented) - VII 0.25 0.50 6.00 2.75 336: 0.52 0.54 0.96 (Cycle) (supplemented) Total 1.75 3.50 42.00 40.90 2434: 3.43 3.09 6.93 (Yield of trim ethyl borate: 99.0 01o) When carrying out the seven cycles according to Table I, an average of 41/2 hours was required for the removal of the water within each cycle, an average of about 5 hours for the removal of the azeotropic mixture of trimethyl borate and methanol and for the removal of the excess methanol from the Residue from glycol and methanol required an average of 2½ hours. The yield of ammonia, sodium chloride and trimethyl borate were practically quantitative for each cycle after the fifth cycle.

The chemical reactions that took place here can be presumed can be represented by the following equations: Na2B4O7-10H2O + 2NH4Cl + 12HOCH2CH2OH # # 4B (OCH2CH2OH) 32NaCl + 17H2O + 2NH3 (1) 4B (OCH2CH2OH3 + 16CH3OH # # 4B (CH3) 3 # CH3OH + 12HOCH2CH2OH (2) total equation: Na2B4O7 # 10H2O + 2NH4Cl + 16CH3OH # # 4B (OCH3) 3CH3OH + 2NaCl + 17H2O + 2NH3 (3) The product made from boron oxide and glycol is a cross-linked, plastic polymer. To simplify the explanation the formulas given above were used.

Example 2 Table II, in which moles are expressed in gramoles, gives the results of various other embodiments of the invention. In each experiment, the boron compound, ammonium chloride and ethylene glycol or diethylene glycol were initially mixed; the reaction mixture was then distilled to drive off water and ammonia overhead until it was essentially anhydrous. Methanol was then added to the reaction mixture and this was distilled again to remove the azeotropic mixture of methanol and trimethyl borate. Table II Trimethyl Boron compound solvent methanol ammonia Try mol borate No. Mole mole mole% yield% yield 1 0.25 Borax 1.0 NH4Cl 5.3 Diethylene glycol 3.11) 86.0 2 0.25 Borax 1.0 NH4Cl 8.3 Ethylene glycol 3.11) 63.5 89.0 3 0.25 Na2B4O7 0.50 NH4Cl2) 6.4 Ethylene glycol 6.4 97.0 86.5 4 0.25 Borax 0.50 NH4C12) - 6.0 Ethylene glycol - 8.0 84.5 84.0 1) The volume of methanol was kept constant during the distillation by introducing methanol.

2) 10% aqueous solution.

EXAMPLE 3 The ulexite used for this experiment was obtained from the Pacific Coast Borax Company as "Gerstley borate" (with a grain size of 0.074 mm). According to the information provided by the supplier, Ulexit has the following composition: equivalent to of Consisted% lements, % B2O3 .............................. 32.97 B: 10.26 Na2O .............................. 4.89 Na: 3.63 CaO .............................. 15.94 Ca: 11.39 H2O and organic parts ... 28.04 SiO2 .............................. 9.52 MgO .............................. 3.54 CO2 3, 24 3.24 Al2O3 .............................. 1.10 Fe2O3 .............................. 0.30 SO3 .............................. 0.14 P2O5 .............................. 0.066 Cl .............................. 0.008 A2O3 .............................. 0.006 Undetermined .................... 0.241 The reported composition was checked.

The ore was found to have 10.22% boron, 4.31,010 sodium, 12.96 Possessed 0 / o calcium and a total basicity (as sodium hydroxide) of 30.77 01o. Pure ulexite according to the formula na CaB5O9 # 8H2O contains 13.34% boron, 5.67% sodium, 9.87% calcium and 35,500 / 0 crystal water. The ore therefore had, based on the Boron content (10.24%), a purity of 76.8%.

The experimental set-up consisted of a three-necked round bottom flask of 1000 ml, which was equipped with a stirrer (mercury plug stirrer). In another side neck was a thermometer connector and a feed funnel used. The thermometer neck reached up to 5.1 cm from the bottom of the flask. In the A few ml of a high-boiling organic liquid (means for Heat transfer) and a thermometer. A distillation device was in the other pages neck of the piston inserted; it consisted of a distillation column, an adjustable distillation attachment, a straight vacuum connector and a feed hopper serving as a template; all parts were connected in series. Two distillation columns were needed: a column 30.5 cm long and 18.9 mm in diameter with a filling of glass beads became during the distillation used by water and ammonia. On the other hand, a Snyder column ("floating ball" type with six individual spherical sections) during the distillation of the azeotropic Mixture of trimethyl borate and methanol used. A U-tube was attached to the outlet of the vacuum connector by means of a Tygon tube piece.

During the distillation of water and ammonia, it contained standardized Acid, water distilled during the distillation of the azeotropic mixture. A Glascol heating mantle was used as a heat source for the distillation processes.

The procedure was as follows: A mixture of about 100 g of ore, 25 to 30 g of ammonium chloride, 250 to 300 ml of distilled water and 400 ml of ethylene glycol was stirred and heated in the flask. For about 5 hours at a bulb temperature of 112 to 182 ° C and a head temperature of 97 to 100 ° C distilled water and ammonia over the aqueous distillate (about 320 to 370 ml) contained the esterification water, ore crystal water and the original water added to prepare the approximately 10 0/0 aqueous ammonium chloride solution.

The reaction mixture remained during the distillation of water and ammonia in the form of a slurry.

400 ml of methanol was added to the cooled non-aqueous glycol slurry entered and then heated. At 75 ° C the reflux showed the aeotropic Mixture of trimethyl borate and methanol has a temperature of 54 ° C. The azeotropic Mixture distilled over in an amount of about 25 ml per hour. Than the temperature of the reflux vapor rose to 58 ° C, the distillation was stopped and the distillate (about 150 ml) analyzed for its trimethyl borate content. Pretty much at the end the distillation of the azeotropic mixture continued -Methanol (about 100 to 150ml) introduced, so that finally the ratio of the volume ethylene glycol to methanol was about 1: 1.

The resulting glycol / methanol slurry was brought to 20 ° C cooled and filtered through # 2 Ballston filter paper. The filtration continued l / 2 hour. The filter cake was washed with a 100 ml portion of methanol and dried in a vacuum oven at 700 C and about 300 mm pressure; it consisted of not dissolved ore and precipitated calcium and sodium chloride. The filtrate became the Destilla subject. Distilled at 64 to 65 ° C for about 4 hours 500 ml of methanol with a small amount of trimethyl borate over. Methanol and ethylene glycol, which is saturated with calcium and sodium chloride at 20 ° C were approved for use provided in further cycles. That for the formation of the azeotropic mixture spent methanol was replaced by fresh methanol from one cycle to another added.

Table III gives the values for all cycles of treatment of ulexite: Table III Water (ml) ammonia trimethyl borate Ulexite ethylene Cycle NH4Cl methanol glycol% Aus% Aus Remarks on off Boron mole booty (per mole booty (each g mole mole ml passed ml cycle) cycle) I 105.6 1.0 0.55 400 265 332 700 0.510 96.3 0.869 86.9 0.020 mol NH3 im 150 147 0.020 second water distillate (147 ml). No N H3im azeo- tropical mixture. II 105.6 1.0 0.55 265 335 200 0.496 94.8 0.918 91.8 8 0.003 mol NH3 im 100 100 (additional 0.024 azeotropic tongue) 0.003 mixed. 0.024 moles NH3 in the second Water distillate (100 ml). III 105.6 1.0 0.50 350 430 210 0.442 103.8 0.809 94.0 0.077 mol NH3 im (Supplementary 0.077 0.131 azeotropic tongue) mix. 0.131 moles B (OCH3) 3 (dist.) as a complex with NH3 in CH30H. IV 52.8 0.5 0.26 200 263 212 0.246 100.0 0.475 95.0 0.014 mol NH3 im (Supplementary 0.014 azeotropic tongue) mix. v 105.6 1.0 0.53 390 450 330 0.434 98.4 0.940 95.5 0.088 mol NH3 im (Supplementary 0.088 0.015 azeotropic tongue) mix. 0.015 moles B (OCH3) 3 (dist.) as a complex with NH3 in CH3OH. VI 105.6 1.0 0.50 300 380 375 0.429 96.8 0.996 99.6 0.055 mol NH3 im (Supplementary 0.055 azeotropic tongue) mix. Overall total 580.8 5.5 2.89 400 2020 2437 2027 2.838 97.9 5.153 93.7 total amount of introduced water sers includes not the rest and criticism stall water.

The column in Table III entitled "Ammonia" shows that averaged about 90.3% ammonia in each cycle during the removal of the water are distilled off. The remainder of the theoretical amount of ammonia was removed from the distillation obtained from methanol and trimethyl borate. Almost at the end of the distillation of the azeotropic mixture (54 ° C) formed a white solid (probably the Complex compound (H3N: B (OCH3) 3) on the cold insert stick. The cooling water was departed and the hot methanol vapor was used to wash the ammonia and trimethyl borate from the solid into the distillate through the pressure equalizer arm on the distillation attachment. To obtain ammonia quantitatively, it usually took about 3 or 4 hours for requires reflux and washout.

The solids consisting of undissolved ore and precipitated chlorides were combined from cycle I through VI, pulverized and used for analysis samples. the combined solids weighed 201.4 g.

Analysis indicated that the solids were 0.16% boron, 17.11% chloride, Contained 12.68% carbon dioxide, 13.81% calcium and 10.80% sodium.

A material balance for boron during the six cycles showed that within Experimental error limits (1) the solid waste 0.56%, (2) the mother liquor of the last cycle 9% and (3) the trimethyl borate distillate 94% of that in the system contained boron content introduced as ulexite. The total is around 103%.

The reason for this deviation is likely to be the addition of experimental analytical errors during the six cycles. The ammonia yield reported in Table III relates to the ammonium chloride feed for each cycle according to the following equation: Example 4 It became Colemanite of the Pacific Coast Borax Company (trademark »Debeley Colemanite«) turns. The following combination is used for this product setting specified: Component% equivalent element B2O3 .............................. 34.25 B: 10.66 CaO .............................. 35.17 Ca: 5.10 Na2O .............................. 0.39 MgO .............................. 0.96 SiO2. .................... ... 2.04 A1203 + Fe2O3 .......... 0.59 CO2 .............................. 12.30 H2O and organic parts 14.02 S O3 0.26 .............................. 0.01 Indefinite .................... 0.01 Total basicity as NaOH ... 27.05 The reported composition was checked.

The ore was found to have 9.82% boron, 21.24% calcium, 8.64% CO2 and had an overall basicity (as sodium hydroxide) of 27.05%. A value of 9.82 was taken as the percentage of boron in the colemanite. This value was in the Manner determined that an ore sample treated with strong hydrochloric acid, with sodium hydroxide neutralized, treated with mannitol and titrated for boric acid with a standardized base became. Pure colemanite of the formula Ca2b6O11 to 5 H2 O contains 15.80 0/0 boron, 19.500 / 0 Calcium and 21.9% water. "Debeley Colemanite" therefore has, based on the boron content (9.82%), a purity of 62.20 0 / o.

The apparatus used for this example corresponded to that of Example 3, with the difference that a Tru-Bor stirrer was used in place of the mercury stirrer. The procedure corresponded to that of Example 3. The values for each cycle of the experiment are given in Table IV. Table IV Ethyl water (ml) ammonia trimethyl borate Colemanite Cycle NH4Cl len- methanol Out% remarks No. Glycol prey (per prey (per boron mole mole g mole mole ml led ml cycle) cycle) I 100.0 0.907 0.530 400 256 305 700 0.481 96.2 0.782 86.2 0.029 mol NH3 im 100 100 second water style lat (100 ml). II 100.0 0.907 0.530 350 405 256 0.424 95.2 0.703 90.4 0.081 mol NH3 im (Supplementary 0.081 0.117 azeotropic mixture zung) 0.117 mol B (OCH3) 3 (dest.), separated with NH3 and CH3OH. After distilling the azeotropic mixture sches. III 50.0 0.454 0.265 200 260 112 0.236 96.9 0.392 86.3 Colemanite was 4 hrs. (Supplement - 0.021 crushed in a ball mill tongue). IV 100.0 0.907 0.500 350 423 338 0.443 111.0 0.811 89.5 0.112 mol NH3 im (Add-0.112 azeotropic mixture. tongue) V 100.0 0.907 0.500 300 350 395 0.389 100.6 0.756 83.4 Some boron and glycol (Supplementary 0.114 splashed out of the tongue) piston over. Overall total 450.0 4.082 2.325 400 1556 1843 1801 2.330 100.1 3.561 87.2 total amount of directed water does not include the esterification and Crystal water.

In each cycle, the mean was about 14.58% of the theoretical Amount of ammonia removed from trimethyl borate and methanol during the distillation, after an average of 85.42 ° / e of ammonia had been removed by distillation with water. Therefore the same problem of the formation of the complex occurred during processing, probably HN: B (OCHa) 3, as in that of the ulexite.

159.4 g solids from cycles I, II, IV, V were mixed together, pulverized and samples taken from it for analysis. The results showed 2.040% boron, 0.620% chloride, 19.24% CO2 and 25.69% calcium, but none Ammonium or sodium salts. 16.8 g of solid from the third cycle were separated analyzed because the unreacted colemanite in a ball mill 4 hours ago the insert was ground in an effort to extract more boron.

The solids of cycle III contained 0.81% boron, 0.34% chloride, 23.92% calcium, but no sodium or ammonium salts. Overall, the Salts of the five cycles an equivalent of 0.313 moles of boron or 7.0 per cent of the ore charge.

A material balance for the five cycles showed - that within experimental conditional error (1) the solid waste 8%, (2) the mother liquor from the last cycle 11 0 /, and (3) the trimethyl borate distillate 87 0 / o des in the system as colemanite Contained Bors.

There are two explanations for the total of 106 per cent. First, there were various determinations of the boron content of the colemanite; the mean of the two lowest values was used as the value for the boron content in the colemanite (9.82%). Perhaps the ore contained more boron than indicated above. Second, experimental errors in the analysis of the azeotropic distillates may have accumulated over the five cycles. The yield of ammonia according to Table IV relates to the use of ammonium chloride for each cycle according to the equation The operation of the above-mentioned examples can be modified in various ways. So borax, anhydrous sodium tetraborate and colemanite can be used as starting materials by other sodium or calcium borates or sodium or calcium borates z. B. ores containing sodium borate such as ulexite (boron sodium calcite), kernite and probertite are replaced.

Ammonium chloride can counteract an equimolecular amount of sodium bisulfate (sodium acid sulfate). Ethylene glycol and diethylene glycol can by an equimolecular amount of a polyhydric alcohol at atmospheric pressure boiling in the range of about 175 to 3750 C, be replaced, e.g. B. propylene glycol, Trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2,4-pentanediol, 1,5-pentanediol, 1,6-hexanediol, 2,5-hexanediol, 2-methyl-1,3-pentanediol, 2-methyl-2,4-pentanediol, 2,4-heptanediol, 2,2-diethyl 1,3-propanediol, 2-ethyl-1,3-hexanediol, triethylene glycol, Dipropylene glycol, glycol, triethanolamine, etc.

The examples show that the relative amounts of sodium or calcium borate, ammonium chloride or sodium bisulfate and alcohol, in the starting reaction mixture can vary somewhat within the scope of the invention. If ammonium chloride as a starting material is chosen, the chlorine content should be approximately equivalent to the sodium or calcium content of the sodium or calcium borate used. If sodium bisulphate is a raw material the sulphate content should match the sodium or calcium content of the raw material used sodium or calcium borate be approximately equivalent. The alcohol content (Ethylene glycol or equivalent) is generally said to be about 4 to 20 gram mol each Gram atom boron of the sodium or calcium borate present in the starting material. Finally, methyl alcohol can be substituted by other lower saturated aliphatic monohydric alcohols Alcohols having 1 to 3 carbon atoms, e.g. B. ethyl alcohol or a propyl alcohol, be replaced. The amount of alcohol used can vary considerably generally about 8 gram mol per gram atom of boron of the sodium or calcium borate will be used used. - The drawing shows a flow diagram of a process which is carried out in the frame of the invention for the production of trimethyl borate falls.

Borax decahydrate, ethylene glycol and a 10 weight percent aqueous Ammonium chloride solution is poured into a reaction vessel 1 through line 2 with reflux ethylene glycol, which contains some dissolved sodium chloride, from the distillation vessel 3 through line 4 abandoned. In the reaction vessel 1, the reaction mixture is dehydrated by distillation; a mixture of water and ammonia passes overhead through line 5 and a mixture from sodium chloride, ethylene glycol, borate and excess ethylene glycol as a bottom product through line 6. The product contracts into the reaction vessel 7 through line 6 with the methanol passed overhead from the distillation vessel 3, methanol bottom product the separating vessel 8 and fresh methanol from the storage container (not shown); all methanol streams enter the reaction vessel 7 through line 9. From the Reaction vessel 7 distills the azeotropic mixture of trimethyl borate and methanol overhead through line 10 in the separating vessel 8 over, in the trimethylborate over Removing overhead through line 11 and methanol as bottoms through line 12; the separation in the separating vessel 8 takes place in a known manner.

The reaction slurry passes from the reaction vessel 7 Line 13 to filter 14, where solid sodium chloride is separated, which is passed through pipe 15 deducts; a mixture of ethylene glycol and methanol is drawn in via line 16 the distillation vessel 3. Methanol is passed from the distillation vessel 3 overhead Line 17 and ethylene glycol removed as bottom product through line 4.

Claims (1)

PATENT CLAIMS: 1. Process for the preparation of boric acid alkyl esters from salts of boric acid by esterification with a higher-boiling alcohol and transesterification of the boric acid ester formed with a lower boiling alcohol, characterized in that a mixture of sodium and / or calcium borate is used with a polyhydric alcohol boiling in the range from 175 to 375 "C with added Esterified by ammonium chloride or sodium sulfate until completely drained and the anhydrous mixture with a saturated aliphatic monohydric alcohol with 1 to 3 carbon atoms with distilling off the boric acid ester formed transesterified. -2. Method according to claim 1, characterized in that the borate salt Borax, colemanite, a mixture of calcium and sodium salts or ulexite. 3. The method according to claim 1 and 2, characterized in that the polyhydric alcohol is a dihydric alcohol, especially monoethylene glycol. 4. The method according to claim 1 to 3, characterized in that the saturated aliphatic monohydric alcohol is methyl alcohol. References considered: U.S. Patent No. 2,088 935; Journal of the American Chemical Society, 75: 213 (1953); Journal of the Applied Chemistry, 4 (1954), pp. 93 to 96.