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Caprolactam Purification
Removal of inorganic and amine impurities

 


Introduction

 

Most commercial production of caprolactam is via the cyclohexanone oximation and Beckmann rearrangement route. Because this process involves use of oleum for the Beckmann rearrangement, followed by neutralization with ammonia or ammonium hydroxide, the process generates large quantities of ammonium sulfate as a waste.

 

The caprolactam is purified by vacuum crystallization or vacuum distillation but small quantities (ppm) of ammonium sulfate remain and contaminate the aqueous caprolactam solution product.

This product stream can be purified by treatment with ion exchange resins, using either a sequence of a Strong Base Anion (SBA) followed by a Strong Acid Cation (SAC) resin, or a SBA-SAC-SBA sequence.

 

 

 

Process Conditions

 

Typical operating conditions for the purification process are shown in the following table.

 

 

Influent Composition
 30% aqueous caprolactam solution with ppm levels of (NH4)2SO4 and amine contaminants
Influent Temperature
 < 50 °C
Flow rate
 6-7 BV/h
Regenerant Type and Sequence

SBA: 5% HNO3, rinse, 4% NaOH, and rinse (initial nitric acid contact step is for caprolactam displacement to facilitate regeneration by caustic)

SAC: 4% NaOH, rinse, 4% H2SO4 or 4% HNO3, and rinse (initial caustic contact step if for caprolactam displacement to facilitate regeneration by acid)

 

 

 

Recommended Products

 

   

Strong base anion gel
Amberlite™ IRA910 Cl     Strong base anion MR
Amberlyst™ 15Wet     Strong acid cation MR

 


For more information on our ion exchange resins, please consult our Frequently Asked Questions page.

 

For pricing, availability or more information please contact your Rohm and Haas representative.

 

 

Further Reading

 

Rohm and Haas Company Ion Exchange Resins Practical Guide "Caprolactam Purification", INF0027.