Glycol Production Selectivity via Segmented Reaction and Distillation
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Solution Overview
Problem
Existing methods for producing dipropylene glycol and tripropylene glycol from propylene oxide and water lack selectivity control, resulting in inadequate management of by-products.
Innovation Solution
A method involving multiple steps of reaction, separation, and recycling of propylene oxide with water, using catalysts like niobium pentoxide, to produce dipropylene glycol and tripropylene glycol with high selectivity by controlling the concentration of by-products through distillation and recycling processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If propylene oxide reacts with water to produce propylene glycol, then propylene glycol is obtained, but dipropylene glycol and tripropylene glycol are formed as unwanted by-products
Solution Approach 1:
The invention segments the reaction process into multiple stages with different water-to-oxirane ratios. The first stage uses a low ratio (0.5-2.0) to minimize by-product formation, while subsequent stages use higher ratios to convert remaining oxirane to desired glycol products, thereby controlling by-product concentration throughout the process
Solution Approach 2:
The invention changes the water-to-oxirane ratio parameter across different reaction stages. By adjusting this parameter from low (0.5-2.0) in the first stage to high (>2.0) in subsequent stages, the process optimizes selectivity while managing by-product formation dynamically
2Productivity
If excess water is present in the reaction mixture, then complete conversion of propylene oxide is achieved, but separation and purification become more difficult
Solution Approach 1:
The invention performs preliminary separation of the first reaction liquid into water-rich and glycol-rich phases before further processing. This preliminary action simplifies subsequent purification steps by pre-concentrating the desired products and removing excess water early in the process
3Quantity of substance
If the reaction proceeds to high conversion, then more propylene glycol is produced, but by-product concentration increases
Solution Approach 1:
The invention divides the conversion process into sequential stages, where the first stage operates at low water-to-oxirane ratio to limit by-product formation, and subsequent stages handle the remaining conversion with higher water ratios, thereby achieving high overall yield while controlling by-product concentration at each stage
Solution Approach 2:
The invention maintains continuous conversion of propylene oxide through multiple reaction stages, ensuring that unreacted oxirane from the first stage is fully converted in subsequent stages. This continuous action achieves complete conversion while managing by-product formation through staged water addition
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 method achieves high selectivity in producing dipropylene glycol and tripropylene glycol, improving their concentration and reducing the impact of alcohol compounds, thereby enhancing the efficiency of the production process.
Implementation Method 1
using catalysts like niobium pentoxide, to produce dipropylene glycol and tripropylene glycol
Implementation Method 2
by controlling the concentration of by-products through distillation and recycling processes
Data Source
Figure 1~2
Figure 3~4
AI summary
There is provided a method for producing dipropylene glycol and/or tripropylene glycol, the method comprising steps (A), (B), (C), (D), and (E) defined below, step (A): the step of reacting a raw material liquid comprising propylene oxide and water to obtain a reaction liquid comprising unreacted water, propylene glycol, dipropylene glycol and/or tripropylene glycol, and an alcohol compound excluding propylene glycol, dipropylene glycol, and tripropylene glycol, step (B): the step of separating, from the reaction liquid, a first liquid containing water and the alcohol compound and a second liquid containing the propylene glycol and the dipropylene glycol and/or tripropylene glycol and optionally containing the alcohol compound, step (C): the step of removing at least a part of the alcohol compound from the first liquid to obtain a third liquid containing water and optionally containing a part of the alcohol compound, step (D): the step of separating, from the second liquid, a fourth liquid containing the propylene glycol and optionally containing the alcohol compound, and a fifth liquid containing the dipropylene glycol and/or tripropylene glycol and optionally containing the alcohol compound, step (E): the step of recycling at least a part of the third liquid to step (A) as a component of the raw material liquid.