Preparation method of DL-proline
A technology of proline and glacial acetic acid, applied in the field of preparation of DL-proline, can solve the problems of easily affecting product quality, long production cycle, inconvenient industrial operation and the like
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Embodiment 1
[0034] 100 g of glacial acetic acid was put into the reactor, and 100 g of L-proline was added under stirring to obtain a reaction solution. Stir the reaction solution to heat up to 70-75°C, and keep stirring for 3 hours to make the racemization reaction of L-proline fully occur, so that the optical rotation of the reaction solution is 0, and the reaction solution is reddish brown at this time.
[0035] After cooling the reaction solution with optical rotation of 0 to 30°C, move it to a distillation pot for distillation under reduced pressure. The distillation temperature is 55-60°C, and the vapor pressure is 0.1MPa. Continue to distill for 30 minutes after distillation until no liquid flows out. The residue after distillation was concentrated to 10% of the original volume to obtain viscous concentrate A.
[0036] Mix the concentrated solution A with 120 g of isopropanol, stir until the crystals are completely precipitated, then cool down to 15°C, centrifuge to remove excess l...
Embodiment 2
[0040] Put 200 g of glacial acetic acid into the reaction kettle, and then add 100 g of L-proline under stirring to obtain a reaction solution. Stir the reaction solution to heat up to 70-75° C., then keep warming and stirring for 3 hours, so that the optical rotation of the reaction solution is 0, and the reaction solution is reddish-brown at this time.
[0041] After cooling the reaction solution with optical rotation of 0 to 30°C, move it to a distillation pot for distillation under reduced pressure. The distillation temperature is 55-60°C, and the vapor pressure is 0.1MPa. Continue to distill for 30 minutes after distillation until no liquid flows out. The residue after distillation was concentrated to 10% of the original volume to obtain viscous concentrate A.
[0042] Mix the concentrated solution A with 120 g of isopropanol, stir until the crystals are completely precipitated, then cool down to 15°C, centrifuge to remove excess liquid, rinse the crystals with isopropano...
Embodiment 3
[0046] Put 80 g of glacial acetic acid into the reaction kettle, and then add 100 g of L-proline under stirring to obtain a reaction solution. Stir the reaction solution to heat up to 70-75°C, keep stirring for 6 hours, and then cool to 30°C.
[0047] Move the reaction solution cooled to 30°C to a still pot for distillation under reduced pressure. The distillation temperature is 55-60°C and the vapor pressure is 0.1MPa. Continue to distill for 30 minutes after distillation until no liquid flows out, and then distill the residue after distillation Concentrate to 10% of the original volume to obtain viscous concentrate A.
[0048] Mix the concentrated solution A with 120 g of isopropanol, stir until the crystals are completely precipitated, then cool down to 15°C, centrifuge to remove excess liquid, rinse the crystals with isopropanol to obtain a crude product.
[0049] Mix 90 g of the crude product, 5 g of activated carbon, and 185 g of water, stir and raise the temperature to...
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