1. 1032 g of orthophosphoric acid was added to a 2L four-neck flask and heated to 160-165°C. 2.
2. a mixed clarified solution consisting of 1032 g of orthophosphoric acid and 852 g of choline chloride was added slowly and dropwise, maintaining the temperature at 160°C for 2 hours, during which time it was ensured that no water vapor was generated and about 520 g of distillate was collected.
3. Transfer the reaction solution to a 50L glass reactor, cool to 30°C, add 15kg of pure water and stir until the solution becomes colorless and transparent, at which time the pH should be 1-2.
4. Add 520g of calcium chloride and stir at room temperature until completely dissolved. 5.
5. Slowly add 900g of calcium carbonate, observe a large number of foam generation and the liquid becomes white milky, stirring at room temperature for 30 minutes.
6. Add 540g of calcium hydroxide, continue to stir at room temperature for 30 minutes, adjust and maintain the pH to 8.0, the liquid is still white milky.
7. Add 2kg of purified water, make sure the pH is stabilized at 8.0, then centrifuge and filter, and wash the filter cake with purified water.
8. Calcium hydroxide was added to the filter cake, the pH was adjusted to 9-13, centrifugation was performed again, and 2.3 kg of calcium phosphate solid was obtained after drying.
9. The filtrate was filtered through a 0.2 μm PP microfiltration membrane to obtain 21 kg of colorless transparent liquid.
10. The liquid was concentrated to 4L using an experimental ultrafiltration membrane at 1.5MPa and 20-30°C. The liquid was then filtered through a 0.5μm PP microfiltration membrane.
11. Add 1.5L of 95% ethanol, stir for 30 minutes and then crystallize at 0-5°C for 3 hours and vacuum filter.
12. Wash the filter cake with 2150 ml of 75% ethanol/pure water (1:1 v/v) and stir the mixture at room temperature.
13. Add 10L of 95% ethanol, the solution gradually changed from turbid to milky white, left to drain.
14. Dry the wet product in vacuum at 60 ℃ for 3 hours to get 1052g N,N,N-trimethyl-2-(phosphonooxy)ethanaminium chloride calcium salt tetrahydrate dry product.
15. Product analysis: Chlorine content 10.7%, phosphorus content 9.5%, calcium content 12.4%, titer content 98.8%. Infrared spectrum conforms to the reference standard.
