US 2022/0089545 A1Published application

Refining process and refining system of caprolactam

AssigneeZhejiang Henglan Science & Technology Co., Ltd.

InventorsShibiao Cheng, Songlin Wang, Fei Shen, Han Wang, Xi Li, Xinping Zhang, Dejia Ma, Xiaokang Hu, Zong Li, Yixuan He

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Abstract

A refining process includes steps of subjecting crude caprolactam to a first evaporative crystallization and a first solid-liquid separation to obtain a first caprolactam crystal and a first crystallization mother liquor; washing the first caprolactam crystal to obtain a second caprolactam crystal; optionally concentrating the first crystallization mother liquor to perform a second evaporative crystallization and a second solid-liquid separation to obtain a third caprolactam crystal and a second crystallization mother liquor; subjecting the third caprolactam crystal to a second washing to obtain a fourth caprolactam; optionally concentrating the second crystallization mother liquor to perform thermostatic crystallization, performing separation to obtain a fifth caprolactam crystal and a third crystallization mother liquor; washing the fifth caprolactam crystal to obtain a sixth caprolactam crystal; and subjecting the second caprolactam crystal to a hydrogenation reaction.

Claims20

Dependent claims

A process for refining caprolactam comprising the following steps:

(1) subjecting a crude caprolactam having a caprolactam content not less than 98 wt % to a first evaporative crystallization in the presence of a first crystallization solvent, so as to obtain a first slurry;
(2) subjecting the first slurry to a first solid-liquid separation to obtain a first caprolactam crystal and a first crystallization mother liquor;
(3) subjecting the first caprolactam crystal to a first washing to obtain a second caprolactam crystal and a first washing liquid;
(4) optionally concentrating the first crystallization mother liquor and then subjecting the concentrated first crystallization mother liquor to a second evaporative crystallization to obtain a second slurry;
(5) subjecting the second slurry to a second solid-liquid separation to obtain a third caprolactam crystal and a second crystallization mother liquor;
(6) subjecting the third caprolactam crystal to a second washing to obtain a fourth caprolactam and a second washing liquid;
(7) optionally concentrating the second crystallization mother liquor, then subjecting the concentrated second crystallization mother liquor to a thermostatic crystallization to obtain a third slurry, which is subjected to a third solid-liquid separation to obtain a fifth caprolactam crystal and a third crystallization mother liquor;
(8) subjecting the fifth caprolactam crystal to a third washing to obtain a sixth caprolactam crystal and a third washing liquid;
and
(9) subjecting the second caprolactam crystal obtained in step (3) to a hydrogenation reaction;
wherein the thermostatic crystallization is carried out in the presence of a thermostatic crystallization solvent comprising solvent A and ethanol, the solubility of caprolactam in solvent A at a temperature of 20° C. is less than 5 wt %, and ethanol is less than 2 wt % of the total amount of thermostatic crystallization solvent.

8 more elements

A refining system of caprolactam comprising a first evaporative crystallizer, a first solid-liquid separation device and a first washing device connected in series, wherein an outlet of the first evaporative crystallizer is in communication with an inlet of the first solid-liquid separation device, and the solid phase outlet of the first solid-liquid separation device is in communication with an inlet of the first washing device;

the system further comprises a second evaporative crystallizer, a second solid-liquid separation device and a second washing device successively connected in series, wherein an inlet of the second evaporative crystallizer is in communication with the liquid phase outlet of the first solid-liquid separation device, an outlet of the second evaporative crystallizer is in communication with an inlet of the second solid-liquid separation device, and a solid phase outlet of the second solid-liquid separation device is in communication with an inlet of the second washing device;
optionally a first solvent recovery column is disposed at the communication pipeline between an inlet of the second evaporative crystallizer and the liquid phase outlet of the first solid-liquid separation device;
the system further comprise a thermostatic crystallizer, a third solid-liquid separation device and a third washing device connected in series, wherein an inlet of the thermostatic crystallizer is in communication with the liquid phase outlet of the second solid-liquid separation device, an outlet of the thermostatic crystallizer is in communication with an inlet of the third solid-liquid separation device, the solid phase outlet of the third solid-liquid separation device is in communication with an inlet of the third washing device;
optionally a second solvent recovery column is arranged at the communication pipeline between an inlet of the thermostatic crystallizer and the liquid phase outlet of the second solid-liquid separation device;
the system further comprise a hydrogenation reactor, an inlet of the hydrogenation reactor is in communication with the solid phase outlet of the first washing device.

2 more elements

Dependencies are inferred from the claim text.