Continuous Glycol Synthesis via Segmented Reactor Zones
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Solution Overview
Problem
Current processes for converting saccharides to ethylene and propylene glycols face challenges such as low yields due to thermal degradation and the need for multiple catalytic species, which complicates the reactor system and reduces product purity.
Innovation Solution
A continuous process using a reactor system with an external recycle loop, where saccharides are contacted with a retro-aldol catalyst in the loop and then with hydrogenation catalyst in the reactor vessel, allowing for high yields and reduced by-product formation by maintaining a high level of hydrogenation catalyst and optimizing reaction conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a continuous flow process with high degree of back mixing is used to prevent thermal degradation, then thermal degradation is reduced, but conversion of starting material is incomplete and overall yield is reduced
Solution Approach 1:
The reaction system is segmented into two distinct zones: a first reaction zone with high back-mixing for retro-aldol reaction at high temperature, and a second reaction zone with plug flow characteristics for hydrogenation at lower temperature. This segmentation allows each zone to be optimized for its specific function, preventing thermal degradation in the hydrogenation zone while achieving complete conversion through the combined effect of both zones.
Solution Approach 2:
Different local conditions are created in different zones: the first zone operates at high temperature (160-200°C) with high back-mixing to promote retro-aldol reaction, while the second zone operates at lower temperature (50-150°C) with plug flow characteristics to prevent thermal degradation and complete hydrogenation. Each zone has locally optimized conditions suitable for its specific reaction.
2Reliability
If multiple catalytic species are used to catalyse retro-aldol and hydrogenation reactions, then reaction completeness is improved, but device complexity increases
Solution Approach 1:
The reactor system is segmented into two zones, each containing a specific catalyst: the first zone contains retro-aldol catalyst (e.g., acid catalysts like H2SO4, HCl, or solid acids like Amberlyst-15), while the second zone contains hydrogenation catalyst (e.g., Raney nickel, Pd/C, or PtO2). This segmentation allows each catalyst to perform its specific function without interference, simplifying the overall system design while ensuring complete reaction.
Solution Approach 2:
The first reaction zone acts as an intermediary stage that converts saccharides to retro-aldol products, which then serve as feedstock for the second zone. This intermediary step allows the system to handle different catalyst requirements separately, with the first zone preparing the substrate for the second zone's hydrogenation reaction, thereby simplifying catalyst selection and reactor design.
3Productivity
If high concentration of starting material is used in the reactor, then productivity is improved, but thermal degradation increases and by-product formation increases
Solution Approach 1:
Different concentration conditions are applied locally in different zones: the first reaction zone operates with high starting material concentration to maximize retro-aldol reaction rate and productivity, while the second reaction zone operates with lower concentration of intermediates to minimize thermal degradation and by-product formation during hydrogenation. This local optimization allows high overall productivity while controlling harmful effects.
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 process achieves high yields of ethylene and propylene glycols with reduced thermal degradation and by-product formation, enabling efficient and flexible catalyst usage, and simplifies the reactor system by maintaining high conversion rates and product purity.
Implementation Method 1
contacting it with a retro-aldol catalyst composition to provide an intermediate stream
Implementation Method 2
contacting said intermediate stream with hydrogen in the presence of a hydrogenation catalyst composition in the reactor vessel
Data Source
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AI summary
The invention provides a continuous process for the preparation of ethylene glycol and 1, 2-propylene glycol from starting material comprising one or more saccharides, said process being carried out in a reactor system comprising a reactor vessel equipped with an external recycle loop and said process comprising the steps of: i) providing the starting material in a solvent, via an inlet, to the external recycle loop and contacting it therein with a retro-aldol catalyst composition to provide an intermediate stream; ii) then contacting said intermediate stream with hydrogen in the presence of a hydrogenation catalyst composition in the reactor vessel; iii) withdrawing a product stream comprising glycols from the reactor vessel; iv) providing a portion of said product stream, via an outlet, for separation and purification of the glycols contained therein; and v) recycling the remainder of said product stream via the external recycle loop.