Glycol Production Process Using Tungsten Catalyst Buffering
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Solution Overview
Problem
Current methods for producing monoethylene glycol (MEG) and monopropylene glycol from saccharides face challenges such as saccharide degradation at elevated temperatures, leading to reduced yields and fouling, along with the susceptibility of homogeneous tungsten-based catalysts to precipitation and catalyst poisoning, which affects the selectivity and efficiency of the process.
Innovation Solution
A process involving a glucose-containing feedstock is maintained at no more than 160°C before being combined with a tungsten-based retro-aldol catalytic species and an alkali metal-containing species, with a molar ratio of alkali metal:tungsten between 0.55 and 6, to reduce saccharide degradation and enhance the selectivity towards MEG production, using a continuous flow reactor system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If saccharide-containing feedstock is held at elevated temperatures for significant periods to enable conversion to glycols, then reaction efficiency improves, but saccharide degradation increases leading to reduced yields and fouling
Solution Approach 1:
The feedstock is preheated to the reaction temperature before entering the reactor, and the residence time in feed lines and mixing zones is minimized to less than 5 seconds. This preliminary action ensures that saccharide degradation is limited to less than 5% before the actual reaction begins, preventing loss of valuable substrate while maintaining high reaction efficiency in the reactor
Solution Approach 2:
The process minimizes the time that saccharide-containing feedstock spends at elevated temperatures during heating and mixing by using rapid heating and efficient mixing systems. The feedstock is quickly brought to reaction temperature and immediately processed, rushing through the vulnerable temperature exposure period to prevent degradation
2Productivity
If homogeneous tungsten-based catalysts are used to catalyse retro-aldol reactions, then catalytic activity improves, but catalyst precipitation and poisoning occur reducing selectivity
Solution Approach 1:
A buffer system comprising an alkali metal salt and a weak acid or its conjugate base is introduced as an intermediary substance. This buffer maintains the pH in the range of 2-8, preventing tungsten catalyst precipitation and poisoning while allowing the catalyst to maintain high activity. The buffer acts as a mediator that stabilizes the chemical environment without interfering with the catalytic function
Solution Approach 2:
The process controls the pH parameter within a specific range of 2-8 using the buffer system, and maintains the temperature below 200°C. These parameter changes prevent tungsten catalyst degradation and precipitation, ensuring catalyst stability and reliability while preserving catalytic activity for the retro-aldol reaction
3Reliability
If the molar ratio of alkali metal to tungsten is optimized to maintain catalyst stability, then catalyst reliability improves, but process complexity increases
Solution Approach 1:
The process defines a specific molar ratio range of alkali metal to tungsten (0.55-6:1) and maintains pH within 2-8. By establishing these clear parameter ranges, the buffer system automatically maintains catalyst stability without requiring complex real-time adjustments or monitoring systems, simplifying the overall process control while ensuring reliability
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 increases the yield of desirable glycols, particularly MEG, by minimizing saccharide degradation and maintaining catalyst stability, enabling commercially viable production with high selectivity towards MEG.
Implementation Method 1
The first catalytic species catalyses the hydrogenolysis reaction, which is postulated to have a retro-aldol mechanism
Implementation Method 2
the hydrogenolysis reaction, which is postulated to have a retro-aldol mechanism
Implementation Method 3
the second catalytic species is present for the hydrogenation reaction
Implementation Method 4
contacting the combined feed stream with a hydrogenation catalytic species in the presence of hydrogen
Implementation Method 5
A buffer can be used in a process for the conversion of saccharides to glycols. Such buffers are used to maintain the pH in the reactor within a preferred range
Implementation Method 6
A preferred methodology for a commercial scale process would be to use continuous flow technology, wherein feed is continuously provided to a reactor and product is continuously removed therefrom
Data Source
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AI summary
The invention provides a process for the preparation of glycols from a saccharide-containing feedstock in a reactor system, said process comprising: i) providing a first feed stream comprising said saccharide-containing feedstock in a first solvent at a temperature of no more than 160°C; ii) providing a second feed stream comprising a tungsten- based retro-aldol catalytic species and an alkali metal containing species in a second solvent at a temperature in the range of from 150 to 250°C; iii) combining the first feed stream and the second feed stream, before they are provided to the reactor system, to form a combined feed stream; iv) providing the combined feed stream to the reactor system and operating the reactor at a temperature in the range of from 150°C to 250°C; and v) also contacting the combined feed stream with a hydrogenation catalytic species in the presence of hydrogen, wherein the molar ratio of alkali metal:tungsten in the combined feed stream is in the range of from 0.55 to 6.