Full continuous-flow preparation method of L-carnitine

A full continuous-flow preparation method of L-carnitine using a micro-reaction system, the micro-reaction system comprising a first micromixer, a first microchannel reactor, a second micromixer, a second microchannel reactor, a third micromixer, a third microchannel reactor, a fourth micromixer and a fourth microchannel reactor communicated in sequence;

• and the method comprising:
• (S1) respectively transporting chlorine gas and a diketene reaction liquid to the first micromixer for mixing, and allowing the reaction mixture in the first micromixer to flow into the first microchannel reactor followed by a continuous chlorination reaction;
• (S2) transporting the reaction mixture flowing out from the first microchannel reactor and an alcohol solvent into the second micromixer and the second microchannel reactor in sequence fora continuous esterification reaction;
• (S3) neutralizing the reaction mixture flowing out from the second microchannel reactor with a first alkali followed by a continuous extraction and separation to collect a first organic phase;
• simultaneously transporting the first organic phase and an aqueous solution of a reductase to the third micromixer and the third microchannel reactor fora continuous reduction reaction;
• (S4) removing the reductase from the reaction mixture flowing out from the third microchannel reactor via an extraction separator followed by a continuous extraction and separation to obtain a second organic phase;
• and concentrating the second organic phase to obtain a concentrated liquid;
• (S5) simultaneously transporting the concentrated liquid obtained in step (S4) and a trimethylamine solution to the fourth micromixer and the fourth microchannel reactor in sequence fora continuous substitution and hydrolysis reaction;
• and
• (S6) neutralizing the reaction mixture flowing out from the fourth microchannel reactor with a second alkali followed by feeding the neutralized reaction mixture into a demineralization device and a concentration device to obtain the L-carnitine.