Methoxypropanol Separation via Membrane and Distillation
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Solution Overview
Problem
The separation of 1-methoxypropan-2-ol from an aqueous stream containing 1-methoxypropan-2-ol and 2-methoxypropan-1-ol is challenging due to their similarities and the presence of impurities like propylene glycol dimethyl ether, especially at low water concentrations, where existing methods fail to achieve high purity and efficiency.
Innovation Solution
A process involving distillation in a column operated at pressures ≥ 2 bar, followed by membrane separation and additional distillation steps, effectively enriches 1-methoxypropan-2-ol to ≥ 95 weight-% while minimizing water and impurity content, using a multi-stage approach with heat integration for energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional distillation methods are used to separate 1-methoxypropan-2-ol from aqueous stream, then the separation process is simple, but the purity of 1-methoxypropan-2-ol cannot reach ≥95 weight-% due to similarities between isomers and presence of impurities
Solution Approach 1:
The separation process is divided into multiple distinct stages: initial distillation to remove water and light impurities, membrane separation to concentrate the isomers, and final distillation to achieve ≥95 weight-% purity. Each stage targets specific components, breaking down the complex separation task into manageable segments that collectively achieve the desired purity.
Solution Approach 2:
A membrane separation unit is introduced as an intermediary step between initial distillation and final distillation. This membrane unit selectively concentrates the methoxypropanol isomers from the aqueous stream, creating a intermediate product that is easier to purify in the final distillation stage, thereby enabling achievement of ≥95 weight-% purity.
2Manufacturing precision
If multiple separation steps are implemented to achieve high purity, then the purity of 1-methoxypropan-2-ol reaches ≥95 weight-%, but the energy consumption increases
Solution Approach 1:
The process utilizes parameter changes by operating distillation columns at different pressures (≥2 bar in the first distillation step) and using membrane separation at controlled temperatures. These parameter optimizations minimize energy requirements while achieving the necessary separation efficiency at each stage.
Solution Approach 2:
The membrane separation unit operates continuously to concentrate the isomers from the distillate stream, providing a continuous feed to the final distillation column. This continuous operation eliminates idle time and maintains efficient energy utilization throughout the separation process.
3Productivity
If distillation is performed at atmospheric pressure, then the operation is simple, but the separation efficiency of propylene glycol dimethyl ether is insufficient
Solution Approach 1:
The first distillation column operates at elevated pressure (≥2 bar) rather than atmospheric pressure. This pressure parameter change alters the relative volatility of components, particularly improving the separation efficiency of propylene glycol dimethyl ether from the aqueous stream, while the pressure is subsequently reduced for the membrane separation step.
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 purity of 1-methoxypropan-2-ol with minimal water and impurities, demonstrating improved separation efficiency and energy efficiency through heat integration, particularly by effectively managing propylene glycol dimethyl ether removal.
Implementation Method 1
separating 1-methoxypropan-2-ol and 2-methoxypropan-1-ol from the stream S0 provided in (a) by distillation comprising subjecting the stream S0 provided in (a) to distillation conditions in a distillation unit comprising a distillation column B
Implementation Method 2
separation of the stream S1 obtained in (b) with at least one membrane unit M comprising at least one membrane module, obtaining a stream S2 which is depleted of water and further enriched in 1-methoxypropan-2-ol and 2-methoxypropan-1-ol compared to the stream S1
Implementation Method 3
the thermal energy of stream S1 is partly transferred to a heat transfer medium stream HTMS1 after (b) and before step (c), preferably in a heat exchanger H, obtaining a heat transfer medium stream HTMS1a having an increased thermal energy content compared to HTMS1
Data Source
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AI summary
A first aspect of the invention relates to a process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol, wherein the process comprises providing a stream SO comprising 1-methoxypropan-2-ol, 2-methoxypropan-1-ol and water, and having a molar ratio of 1-methoxypropan-2-ol : 2-methoxypropan-1-ol in the range of from 1 : 5 to 5 : 1; wherein the final stream S5 comprises ≥ 95 weight- % 1-methoxypropan-2-ol based on the total weight of S5. In a second aspect, the invention relates to 1-methoxypropan-2-ol or a mixture of 1-methoxypropan-2-ol and 2-methoxypropan-1-ol obtained or obtainable from the process of the first aspect.