Caprolactam Production Process

Introduction

Caprolactam (C₆H₁₁NO) is the raw material for Nylon-6 plastics and fiber engineering. 

Caprolactam is a chemical compound consisting of carbon, nitrogen, oxygen and hydrogen. It is made by using either cyclohexane or phenol. When caprolactam is at temperatures above its melting point, it becomes a colorless liquid. 

Cyclohexanone (CH₂)₅CO, an intermediate of caprolactam, is an organic ketone and has the appearance of clear water.

Chemical curve: Caprolactam R.I. per Conc% b.w. at Ref. Temp. of 20˚C

Application

Conventional caprolactam technology is based on the key intermediate cyclohexanone, which is usually produced by the oxidation of cyclohexane, but can also be made from phenol or toluene. 

Separately, hydroxylamine sulfate is manufactured by the oxidation of ammonia to nitrous oxide. This is followed by hydrogenation in the presence of sulfuric acid. Then, the hydroxylamine sulfate is reacted with the cyclohexanone to produce cyclohexanone oxime. This is followed by a Beckmann rearrangement, using oleum to yield caprolactam.

Typical end products

of Caprolactam (C₆H₁₁NO), Cyclohexanone (CH₂)₅CO:

• Nylon-6
• Cyclohexanone

Instrumentation and installation

Vaisala Polaris™ PR53GP Process Refractometer is used to measure the concentration of aqueous caprolactam solution after the initial extraction to control and maintain high extraction efficiency. 

The refractometer is also used for evaporation process control. The refractometer is mounted in the outlet of the evaporator. It provides a signal to a controller to regulate the concentration value by varying the inlet flow through the evaporators. If the concentration value increases, the inlet regulating valve increases the product flow rate through the evaporators, thereby bringing the concentration back to the required value.

Vaisala Polaris™ PR53GP Process Refractometer

Description 
The Vaisala Polaris PR53GP Process Refractometer is a heavy-duty instrument with non-weld body construction for diverse applications. The PR53GP can be installed directly into a tank or large pipelines, using either a standard ANSI, DIN or JIS flange connection, or clamp connection.

User Interface 
Vaisala Polaris process refractometers are compatible with the Indigo platform, offering plug-and-play connectivity, user-friendly interfaces and service and configuration tools. The Indigo520 transmitter adds a physical user interface, data logging, advanced diagnostics, automatic wash control, and access to measurement settings and parameters.

Measurement range 
Refractive Index (nD) 1.3200 – 1.5300, corresponding to 0-100 % by weight.