Caprolactam Production via Aqueous Ammoximation
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Solution Overview
Problem
The existing caprolactam production methods face challenges such as low yield, high byproduct ammonium sulfate production, long process flow, and high energy consumption due to limitations in the ammoximation reaction temperature and solvent usage, which restrict cyclohexanone conversion ratio and selectivity for cyclohexanone oxime.
Innovation Solution
The method involves conducting the ammoximation reaction in pure water at elevated temperatures (80-100 °C) without organic solvents, followed by extraction with an inert organic solvent to enhance cyclohexanone oxime separation and reuse, thereby improving caprolactam yield and reducing energy consumption and waste water production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an inert organic substance with low boiling point is used as reacting solvent in ammoximation reaction, then the reaction can proceed at lower temperature (60-84 °C), but the cyclohexanone conversion ratio and selectivity for cyclohexanone oxime are low, and additional separation and purification equipment is required
Solution Approach 1:
The patent changes the physical and chemical parameters of the reaction system by replacing the organic solvent with an aqueous ammonia solution, allowing the reaction temperature to be elevated from 60-84 °C to 90-110 °C. This parameter change enables higher cyclohexanone conversion ratio and selectivity for cyclohexanone oxime while avoiding the limitations of low-boiling organic solvents
Solution Approach 2:
The patent uses water as the reaction medium instead of expensive inert organic solvents. Water is abundant, cheap, and environmentally friendly, eliminating the need for complex solvent recovery systems and reducing equipment investment while achieving the desired reaction outcomes
2Ease of manufacture
If an inert organic substance is used as reacting solvent, then the ammoximation reaction can be conducted, but the temperature cannot be raised too high due to the low boiling point and flammability, resulting in low conversion ratio and requiring refinement before Beckmann rearrangement
Solution Approach 1:
The reaction system itself provides the necessary properties for both reaction and separation. The aqueous ammonia solution medium allows the cyclohexanone oxime product to be directly utilized in the subsequent Beckmann rearrangement reaction without additional purification steps, as the water and ammonia can be easily removed or are already in appropriate forms for the next reaction stage
Solution Approach 2:
The patent utilizes phase transition properties of water and ammonia to facilitate product separation and reuse. By controlling temperature and pressure, water can be evaporated or condensed, and ammonia can be stripped or absorbed, enabling efficient separation without complex equipment and reducing energy consumption compared to organic solvent systems
3Ease of operation
If the existing ammoximation process is used with organic solvent, then the reaction system has low viscosity, but the equipment investment and energy consumption for separation and purification are increased, accounting for 50 % of steam consumption
Solution Approach 1:
The patent merges the ammoximation reaction step with the product utilization step by using a reaction medium (aqueous ammonia solution) that does not require separation before the Beckmann rearrangement. The reaction mixture can be directly fed to the rearrangement reactor after simple filtration or settling, eliminating the energy-intensive distillation and purification steps that consume 50% of the steam in conventional processes
Solution Approach 2:
Aqueous ammonia solution serves as an intermediary medium that facilitates both the ammoximation reaction and the subsequent Beckmann rearrangement. The ammonia in the medium acts as both a reactant in ammoximation and a catalyst/solvent in Beckmann rearrangement, while water provides a safe, high-temperature stable environment for the reaction without requiring energy-intensive removal
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach increases caprolactam yield, shortens the production process, reduces byproduct formation, and allows for solvent recovery, resulting in significant energy savings and process improvements, with potential annual reductions of 40-50 million RMB in energy consumption and 8,000 tons of waste water.
Implementation Method 1
controlling cyclohexanone, ammonia, and hydrogen peroxide to have an ammoximation reaction in an aqueous solvent at 80-100 °C temperature in the presence of an oximation catalyst
Implementation Method 2
Extracting the obtained solution that contains cyclohexanone oxime in step (1) with an inert organic solvent, to obtain an extract phase that contains cyclohexanone oxime and a raffinate phase that contains the oximation catalyst and water
Implementation Method 3
controlling the extract phase to have a Beckmann rearrangement reaction with oleum
Implementation Method 4
controlling the product of the Beckmann rearrangement reaction to have a neutralization reaction with ammonia
Data Source
AI summary
A caprolactam preparation method provided in the present invention comprises the following steps: (1) in the presence of an oxime catalyst and absence of any organic solvent, conducting an ammoximation on cyclohexanone, ammonia, and hydrogen peroxide in an aqueous solvent and at a temperature between 50 and 200 °C to obtain a solvent containing a cyclohexanone oxime; (2) extracting the solvent containing the cyclohexanone oxime with an inert organic solvent to obtain an extract phase containing the cyclohexanone oxime and a raffinate phase containing the oxime catalyst and water; (3) conducting a Beckmann rearrangement reaction on the extract phase and an oleum, then conducting a neutralization reaction between a product of the Beckmann rearrangement reaction and the ammonia. The method preparing caprolactam increases a yield of the caprolactam and eliminates refining process of the cyclohexanone oxime, thus greatly shortening a manufacturing procedure and lead time, while recycling the inert organic solvent by a rearrangement reaction heat recovery.