Preparation
Step 1: Add tetramethylpiperidinone, catalyst, caustic soda flakes, and water to the high-pressure reactor and seal it.
Step 2: Purge the reactor with N2 to replace the air, then purge with H2 to replace the N2, and finally purge with H2 until the pressure reaches 0.8 MPa.
Step 3: First, maintain the pressure inside the reactor at 0.8 MPa. When the pressure drops, promptly replenish the reactor with H2 to 0.8 MPa while stirring and heating, controlling the temperature at 70-100°C. Repeat the above operation until the pressure inside the reactor remains at 0.8 MPa for a certain period of time without change, then stop the reaction.
Step 4: Purge the reactor with N2 to replace the H2, and simultaneously purge the reactor coils with cooling water to lower the temperature inside the reactor to below 50°C. Stop stirring, filter out the catalyst, and distill off some of the water.
Step 5: Stir and cool the remaining supersaturated mother liquor in an ice-water bath to crystallize, filter and wash to obtain 2,2,6,6-Tetramethyl-4-piperidinol, and recover and reuse the mother liquor.
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