Glycol Production via Two-Stage Reactor Segmentation
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Solution Overview
Problem
Current methods for converting saccharides to ethylene and propylene glycols result in side products like sorbitol, which decrease the yield of higher-valued MEG and MPG, and require energy-intensive separation and recycling processes.
Innovation Solution
A process involving two reactors with specific catalyst systems, where the first reactor converts saccharides to a product stream containing sugar alcohols, and the second reactor converts a portion of these alcohols back into glycols, maintaining sufficient sugar alcohols for catalyst recycling without degrading existing glycols, using a retro-aldol and hydrogenation catalyst composition with tungstates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydrogenolysis of saccharides is performed to produce MEG and MPG, then glycol production occurs, but sugar alcohols like sorbitol are formed as side products that decrease overall yield
Solution Approach 1:
The process is divided into two distinct reaction stages: first, hydrogenolysis of saccharides to produce glycols and sugar alcohols; second, conversion of sugar alcohols to additional glycols. This segmentation allows optimization of each stage independently and converts previously harmful side products into valuable additional product.
Solution Approach 2:
The sugar alcohols (sorbitol) that were previously considered harmful side products decreasing yield are now converted into beneficial additional glycol production through the second reaction stage using a different catalyst system, turning the harmful byproduct into a valuable intermediate.
2Manufacturing precision
If sugar alcohols are separated from desired products via distillation, then product purity is achieved, but energy consumption increases
Solution Approach 1:
The process changes the chemical composition parameters of the product stream by converting sugar alcohols to glycols in situ, fundamentally altering the separation requirements and reducing reliance on energy-intensive distillation to achieve the desired product purity.
3Ease of manufacture
If sugar alcohols are used as recycle solvent for homogeneous catalyst, then catalyst recycling efficiency improves, but sugar alcohol buildup occurs requiring removal via bleed
Solution Approach 1:
The second reactor continuously converts sugar alcohols back to glycols, creating a feedback mechanism that prevents sugar alcohol accumulation in the recycle stream, allowing sustained efficient catalyst recycling without buildup problems.
4Productivity
If existing glycols are degraded during sugar alcohol conversion, then sugar alcohols are converted to glycols, but product quality decreases
Solution Approach 1:
Different catalyst systems with specific selectivities are used in different reaction zones: the first catalyst system (Ru/C) selectively performs hydrogenolysis of saccharides, while the second catalyst system (Ni/C or Cu/C) selectively converts sugar alcohols to glycols without degrading existing glycols, ensuring each reaction produces its intended product with high selectivity.
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 enhances the yield and purity of ethylene and propylene glycols while reducing energy consumption and the need for complex recycling, by efficiently converting sugar alcohols into glycols without degrading the existing products, and allows for the recycling of catalysts.
Implementation Method 1
a retro-aldol catalyst composition and a hydrogenation catalyst composition
Implementation Method 2
contacting a sorbitol feed with hydrogen in a reactor in the presence of a solvent and a bi-functional catalyst system
Data Source
AI summary
The invention provides a process for the preparation of ethylene glycol and 1, 2-propylene glycol from starting material comprising one or more saccharide, wherein the process comprises the steps of: i) providing the starting material and hydrogen to a first reactor and reacting said starting material and hydrogen therein in the presence of a solvent and a first catalyst system comprising a retro-aldol catalyst composition and a hydrogenation catalyst composition; ii) continuously removing a first reactor product stream from the first reactor, said first reactor product stream comprising ethylene glycol, 1, 2-propylene glycol and in the range of from 2 to 40 wt% of sugar alcohols; iii) contacting said first reactor product stream in a second reactor in the presence of hydrogen with a second catalyst system comprising at least a hydrogenation catalyst composition; and iv) converting a portion of the sugar alcohols in the second reactor into ethylene glycol and/or 1, 2-propylene glycol to provide a second reactor product stream comprising ethylene glycol, 1, 2-propylene glycol and in the range of from 10 to 80% of the amount of sugar alcohols present in the first reactor product stream.