Clean D,L-Methionine Synthesis via CO2 Phase Transition
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Solution Overview
Problem
Current methods for synthesizing D,L-methionine result in excessive wastewater production and environmental pollution due to the generation of N and S-containing organic compounds, along with high thermal and electric energy consumption and accumulation of by-products, which complicates the industrial production process and affects product quality.
Innovation Solution
A method involving the continuous reaction of 3-methylthio propionaldehyde, KCN, and NH4HCO3 in a tubular reactor, followed by decomposition and saponification to produce D,L-methionine potassium solution, with subsequent recycling of NH4HCO3 for raw material reuse, and the use of organic solvents for continuous extraction and crystallization to minimize waste and by-product accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fractionized condensation and crystallization method is used, then D,L-methionine can be obtained with high purity, but a large quantity of thermal energy is consumed and significant increase in product cost occurs
Solution Approach 1:
The patent utilizes phase transition of CO2 from gas to liquid state under pressure for acidification, and then back to gas state for release. This phase transition mechanism enables efficient acidification without requiring large quantities of thermal energy for heating and condensation operations, thereby resolving the contradiction between obtaining high purity product and reducing thermal energy consumption
Solution Approach 2:
The patent changes the pressure parameter of CO2 to control its phase state, using high pressure for dissolution and acidification, then reducing pressure for CO2 release. This parameter change approach enables the acidification process to proceed without excessive thermal energy input, maintaining product purity while reducing energy consumption
2Productivity
If polyvinyl alcohol is added for crystallization, then D,L-methionine can be obtained, but the crystallization mother solution cannot be recycled and produces a large quantity of wastewater containing organic compounds
Solution Approach 1:
The patent removes polyvinyl alcohol from the crystallization process entirely, replacing it with a CO2-based acidification method. This extraction of the harmful substance (polyvinyl alcohol) from the process eliminates the source of organic contamination in wastewater, allowing mother solution recycling and preventing organic compound pollution
Solution Approach 2:
The patent converts CO2, which can be considered a waste product or byproduct of other processes, into a useful acidifying agent. By pressurizing CO2 to dissolve in the mother solution and then releasing it for acidification, the process turns a potentially harmful gas into a beneficial reagent, enabling both product formation and mother solution recycling without organic wastewater
3Productivity
If neutral amino acid and organic acid mixture is added as catalyst, then preparation yield of 5-(β-methylthioethyl)glycolyurea is improved, but metal salts accumulate in mother solution making it unrecoverable and producing large quantity of wastewater
Solution Approach 1:
The patent replaces traditional catalyst systems with a CO2-based acidification approach that does not require catalyst recovery. The CO2 acts as a temporary reagent that is easily removed by pressure reduction, eliminating the need for complex catalyst recovery systems and preventing metal salt accumulation, thus maintaining mother solution recyclability
4Productivity
If saponification with alkaline sodium compounds is used, then D,L-methionine can be produced, but a large quantity of by-products such as sodium sulfate is generated requiring significant separation and processing burden
Solution Approach 1:
The patent changes the chemical nature of the acidification agent from traditional strong mineral acids to pressurized CO2. This parameter change in the acidifying reagent prevents the formation of sulfate by-products, eliminating the need for complex sodium sulfate separation and processing systems while maintaining efficient D,L-methionine production
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 significantly reduces wastewater production, enables comprehensive utilization of exhaust gases, and ensures a clean and efficient industrial process for D,L-methionine synthesis, addressing environmental pollution and energy consumption issues while maintaining high product quality.
Implementation Method 1
preparing 5-(β-methylthioethyl)glycolyurea reaction fluid by using 3-methylthio propionaldehyde, KCN and NH4HCO3 solution as raw materials for continuous reaction in a tubular reactor that is gradually heated
Implementation Method 2
proceeding with decompression of aforesaid 5-(β-methylthioethyl)glycolyurea reaction fluid to separate NH3 and CO2 from the reaction fluid
Implementation Method 3
followed by decomposition and saponification to produce D,L-methionine potassium solution
Implementation Method 4
eliminating the produced NH3 and CO2 during saponification through desorption of the saponification fluid
Implementation Method 5
obtaining NH4HCO3 solution through spraying with water to the absorbed NH3 and CO2 as separated in Steps (2) and (3)
Implementation Method 6
using an organic solvent for reversed and continuous extraction
Implementation Method 7
directly using the organic solvent recycled through distillation of an organic solvent layer
Implementation Method 8
delivering CO2 gas to the continuous crystallizer for acidification to control pH value of reaction fluid in the continuous crystallizer at 6-9, and then obtaining crystallization intermixture
Implementation Method 9
delivering water as produced through reversed and continuous extraction in Step (5) to the continuous crystallizer, simultaneously delivering CO2 gas to the continuous crystallizer for acidification
Data Source
Figure 1
AI summary
The present invention discloses a clean method for preparing a D,L-methionine comprising the steps of: preparing a potassium cyanide solution using a crystallized mother solution containing potassium carbonate as an absorbing liquid to absorb hydrocyanic acid, then reacting the potassium cyanide solution with 3-methylthio propionaldehyde and an ammonium bicarbonate solution at 50-150°C for 3-15 minutes so as to obtain a 5-(β-methylthioethyl)glycolyurea solution, then bring the 5-(β-methylthioethyl)glycolyurea solution to a temperature of 140-220°C and subjecting to a saponification reaction for 2-5 minutes, after the completion of the saponification, reducing the temperature to 0-40°C, extracting with an organic solvent, neutralising the water phase with CO2 and crystallizing, then filtering, washing, and drying to obtain an acceptable D,L-methionine product; bring the crystallized D,L-methionine mother solution from filtration to a temperature to 110-160°C to remove CO2, which are all then circulated and used as a hydrocyanic acid-absorbing liquid. The process route of the present invention is a route suitable for a continuous and clean production, substantially without producing waste water and waste gas.