Staged Hydrolysis of MGDN for Low By-Product MGDA Salts
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Solution Overview
Problem
The existing processes for preparing methylglycine-N,N-diacetic acid tri(alkali metal) salts through alkaline hydrolysis of methylglycinediacetonitrile suffer from thermal lability and high by-product formation, leading to the generation of toxic and colored by-products, which complicates the purification and reduces yield and purity.
Innovation Solution
A process involving controlled temperature stages and ammonia stripping to minimize by-product formation, where methylglycinediacetonitrile is mixed with aqueous alkali at ≤30°C, followed by staged temperature reactions and pressure hydrolysis, with subsequent ammonia removal at 90-105°C, effectively reducing by-product content and achieving high purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional alkaline hydrolysis is performed at high temperature (95°C for 5h), then hydrolysis reaction rate is improved, but thermal lability causes dissociation reactions and by-product formation increases
Solution Approach 1:
The hydrolysis reaction is divided into multiple temperature stages: initial mixing at ≤30°C, first reaction stage at 10-30°C, second stage at 30-40°C, and optional third stage at 50-80°C. This segmented temperature approach allows the reaction to proceed efficiently while avoiding thermal lability and dissociation reactions that occur at constant high temperatures, thereby reducing by-product formation.
Solution Approach 2:
The patent changes the temperature parameter dynamically during the hydrolysis process rather than maintaining a constant high temperature. By implementing staged temperature control (≤30°C → 10-30°C → 30-40°C → 50-80°C), the reaction achieves high conversion rates while minimizing thermal degradation and by-product formation through optimized temperature profiles at different reaction phases.
2Manufacturing precision
If MGDN is isolated as pure intermediate before hydrolysis, then MGDA yield and purity are improved, but process complexity and production cost increase
Solution Approach 1:
The patent performs preliminary purification of MGDN directly in the reaction mixture by adjusting pH to precipitate impurities before the hydrolysis step. This preliminary action removes contaminants without requiring complete isolation and purification of MGDN as a separate intermediate, thereby achieving high MGDA purity while simplifying the overall process and reducing production costs.
3Productivity
If ammonia stripping is performed at higher temperature, then ammonia removal efficiency is improved, but energy consumption and risk of by-product formation increase
Solution Approach 1:
The patent optimizes the ammonia stripping temperature to a specific range of 90-105°C, which provides sufficient thermal energy for efficient ammonia removal while avoiding excessive energy consumption and preventing thermal degradation or by-product formation. This optimized temperature parameter achieves the balance between removal efficiency and energy efficiency.
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
The process results in low-by-product, light-color methylglycine-N,N-diacetic acid tri(alkali metal) salts with a by-product content <5% and minimal NTA, enhancing yield and purity while reducing toxicity and color contamination.
Implementation Method 1
alkaline hydrolysis of methylglycinediacetonitrile with sodium hydroxide solution to obtain the trisodium salt of MGDA
Implementation Method 2
hydrolysis and removal of ammonia of the solution obtained in step (c), (d) or (e) by stripping at a temperature of from 90 to 105° C.
Data Source
AI summary
The invention relates to a process for preparing low-by-product, light-color methylglycine-N,N-diacetic acid tri(alkali metal) salt by alkaline hydrolysis of methylglycinediacetonitrile (MGDN), comprising the steps in the sequence (a) to (f):(a) mixing of MGDN with aqueous alkali at a temperature of ≦30° C.;(b) allowing the aqueous alkaline MGDN suspension to react at a temperature in the range from 10 to 30° C. over a period of from 0.1 to 10 h to form a solution;(c) allowing the solution from step (b) to react at a temperature in the range from 30 to 40° C. over a period of from 0.1 to 10 h;(d) optionally allowing the solution from step (c) to react at a temperature in the range from 50 to 80° C. over a period of from 0.5 to 2 h;(e) optionally allowing the solution from step (c) or (d) to react at a temperature in the range from 110 to 200° C. over a period of from 5 to 60 min;(f) hydrolysis and removal of ammonia of the solution obtained in step (c), (d) or (e) by stripping at a temperature of from 90 to 105° C.