Background and overview of the preparation method of tetraethylammonium tetrafluoroborate
Tetraethylammonium tetrafluoroborate (Et4NBF4) is a white to off-white crystal with low density, high melting point, low viscosity and stability. And has good electrical conductivity. Et4NBF4 is widely used as an electrolyte salt in organic electrolytes of supercapacitors, and has applications in many aspects such as lithium-ion batteries, electrochemical experimental analysis, and pharmaceutical intermediates. Application and reporting.
Preparation method of tetraethylammonium tetrafluoroborate
Report on the preparation method of tetraethylammonium tetrafluoroborate 1.
The method for synthesizing tetraethylammonium tetrafluoroborate using a microchannel reactor includes: 150g fluoroboric acid solution (mass concentration: 25%) and passing 270g tetraethylammonium hydroxide solution (mass concentration: 40%) Enter the microchannel reactor, the volume flow ratio of the fluoroboric acid solution and the tetraethylammonium hydroxide solution is 1:2, stay at 40°C for 3 minutes to obtain the tetraethylammonium tetrafluoroborate solution, evaporate, concentrate and crystallize to obtain tetraethylammonium tetrafluoroborate. Crude ethyl ammonium tetrafluoroborate and mother liquor. The mother liquor is used to prepare fluoboric acid solution.
Mix the crude tetraethylammonium tetrafluoroborate and 2 times its mass of deionized water in a reaction kettle, heat to boil, cool down and crystallize, and obtain the tetraethylammonium tetrafluoroborate solid and primary product through a solid-liquid separator. Mother liquor, the tetraethyl ammonium tetrafluoroborate solid is detected online, and all indicators (except moisture content) meet the requirements, and the finished product is made by low-temperature vacuum drying; the mother liquor is crystallized once (i.e., heated and boiled, cooled to crystallize), and the solid-liquid process Separate and obtain the tetraethyl ammonium tetrafluoroborate solid that meets the index requirements; after the primary crystallization process continued several times, it was detected that the tetraethyl ammonium tetrafluoroborate solid could not meet the index requirements. After the primary mother liquor was treated with ion exchange resin, the obtained The filtrate is crystallized again, and the substandard tetraethyl ammonium tetrafluoroborate solid is purified twice: mix the substandard tetraethyl ammonium tetrafluoroborate solid with 2 times the mass of deionized water, heat to boil, and cool down to separate. Crystallize, obtain the secondary mother liquor and the wet product of tetraethyl ammonium tetrafluoroborate through solid-liquid separation, the secondary mother liquid undergoes primary crystallization, and the wet product of tetraethyl ammonium tetrafluoroborate is dried in a low temperature vacuum to make the finished product.
The product conversion rate obtained in this example is 99.61%, and the yield rate is 93.68%.
Preparation method report 2 of tetraethylammonium tetrafluoroborate,
(1), Refining of boric acid:
The specific operations are as follows:
Dissolve industrial boric acid in boiled deionized water, and then filter. The filtrate is brought to room temperature, crystallized, filtered, and washed with deionized water. Then the filter cake is redissolved in boiled deionized water, cooled, and crystallized. Repeat the recrystallization process three times to obtain refined boric acid with a yield of 42 to 50%;
(2) Preparation of fluoroboric acid:
Weigh 100ml of 40% (wt) hydrofluoric acid and add it to a polytetrafluoroethylene reactor equipped with stirring, condensation reflux device and cooling coil. While stirring, add 34.5 grams of boric acid in batches within 1 hour. The reaction temperature When the temperature is 35°C, add boric acid and continue stirring for half an hour, then stop stirring and let the ethoxycarbonylbenzene boric acid stand for 2 hours at room temperature. Filter to remove incompatible impurities to obtain a 33% ± concentration fluoboric acid aqueous solution;
(3) Synthesis and purification of tetraethylammonium fluoroborate:
Weigh 25g of tetraethylammonium chloride and 50g of butanol into a reactor made of tetrahydrofuranthiol and polytetrafluoroethylene, slowly add the fluoboric acid aqueous solution dropwise at 30°C within 2 hours, and then raise the temperature to 40°C to continue the reaction. 2 hours. After the reaction is completed, concentrate under reduced pressure, add 25g of butanol at room temperature, stir for 2 hours to crystallize, filter, and wash with butanol to remove the mother liquor with impurities. The resulting wet powder – tetraethyl 40g of ammonium tetrafluoroborate; put the wet powder of tetraethylammonium tetrafluoroborate into a container with a condensation reflux device containing 150 ml of ethanol solution, raise the temperature and boil, until all the solids are dissolved, cool down while stirring, and cool to room temperature. Crystallize and filter at room temperature, wash with ethanol solution at room temperature, repeat the recrystallization process twice, and dry under vacuum to obtain 21 g of qualified tetraethylammonium tetrafluoroborate product with a yield of 64.2% (mol).
References
[1][Chinese invention] CN202010619843.5 A method for preparing tetraethylammonium tetrafluoroborate assisted by bipolar membrane electrodialysis
[2][China invention, China invention authorization] CN200510086517.8 A preparation method of tetraethylammonium tetrafluoroborate
