Strecker Synthesis of MGDA Salts via HCN Concentration Control
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Solution Overview
Problem
Current methods for producing methylglycine-N,N-diacetic acid trialkali metal salts through the Strecker synthesis result in low space-time yields and high levels of toxic secondary components, particularly nitrilotriacetic acid (NTA), which fails to meet specification requirements for biodegradability and color standards.
Innovation Solution
A process involving partial neutralization of α-alanine and controlled addition of formaldehyde and hydrocyanic acid to limit free hydrocyanic acid concentration, combined with post-bleaching using hydrogen peroxide, to enhance space-time yield and reduce NTA content and color imperfections in the aqueous solution of methylglycine-N,N-diacetic acid trialkali metal salts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the Strecker synthesis is performed with conventional methods, then the production of MGDA trialkali metal salts is achieved, but the space-time yield is low and NTA content is high
Solution Approach 1:
The patent applies parameter changes by controlling the concentration of free hydrocyanic acid in the reaction mixture to not exceed 10 mol% based on the amount of hydrocyanic acid metered in. This parameter control prevents excessive NTA formation while maintaining high productivity through efficient Strecker synthesis conditions
Solution Approach 2:
The patent implements feedback control by continuously monitoring and controlling the concentration of free hydrocyanic acid during the reaction process. The addition of formaldehyde and hydrocyanic acid is controlled to maintain HCN concentration within specified limits, providing real-time feedback to prevent harmful side reactions
2Speed
If the concentration of free hydrocyanic acid is increased to improve reaction rate, then productivity increases, but harmful side reactions increase
Solution Approach 1:
The patent optimizes the parameter of free hydrocyanic acid concentration by limiting it to a maximum of 10 mol% based on the amount of hydrocyanic acid metered in. This parameter optimization maintains adequate reaction rate while preventing harmful side reactions such as formaldehyde cyanohydrin formation and HCN polymerization
Solution Approach 2:
The patent applies partial action by using controlled amounts of hydrocyanic acid - sufficient to drive the Strecker synthesis forward but limited to prevent excessive concentrations that would cause side reactions. The formaldehyde and HCN are added in controlled proportions to achieve optimal conversion without excess
3Quantity of substance
If conventional Strecker synthesis is used, then MGDA is produced, but the Hazen color number exceeds specification limits
Solution Approach 1:
The patent converts the potentially harmful high concentration of reactants that could cause side reactions into a benefit by carefully controlling the HCN concentration at ≤10 mol%. This controlled condition prevents color-forming side reactions while maintaining high productivity, turning a potential hazard into a quality assurance mechanism
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 achieves a significant increase in space-time yield while ensuring NTA content is below 0.1% and Hazen color number is reduced to acceptable levels, meeting product specifications for MGDA trialkali metal salts, thereby improving the environmental and safety aspects of the synthesis.
Implementation Method 1
by reaction with formaldehyde and hydrocyanic acid to form α-alanine-N,N-diacetonitrile
Implementation Method 2
saponification thereof with a base to give an aqueous solution of the corresponding methylglycine-N,N-diacetic acid trialkali metal salt
Implementation Method 3
post-bleaching using hydrogen peroxide
Data Source
AI summary
The invention relates to a method for producing aqueous solutions of methylglycine-N,N-diacetic acid trialkali metal salts at a high yield and purity using Strecker synthesis, starting from an aqueous solution of a-alanine, by reacting same with formaldehyde and hydrocyanic acid in an aqueous solution to form a-alanine N,N-diacetonitrile in a reaction unit, and saponifying same with a base to form the corresponding methylglycine-N,N-diacetic acid trialkali metal salt. The method is characterized in that the a-alanine is partially neutralized, and the addition of formaldehyde and hydrocyanic acid for reacting into a-alanine-N,N-diacetonitrile is controlled such that the concentration of free hydrocyanic acid in the liquid reaction mixture is limited at all times so that secondary reactions, in particular into formaldehyde cyanohydrin, including subsequent reactions of the formaldehyde cyanohydrin as well as the polymerization of hydrocyanic acid occur only to such an extent that the specification requirements for the methylglycine-N,N-diacetic acid trialkali metal salt, in particular with respect to the nitrilotriacetic acid content and color, are met.