Separating HCFC-1233 from HF via Liquid Phase Split
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Solution Overview
Problem
The challenge lies in separating monochloro-trifluoropropenes, such as 1,1,1-trifluoro-3-chloro-2-propene (HCFC-1233zd), from azeotropic or near azeotropic streams with hydrogen fluoride, where the similar boiling points of these compounds complicate traditional separation methods.
Innovation Solution
The method employs chilled, liquid phase separation combined with azeotropic distillations, involving a rectification column to separate hydrogen chloride, followed by cooling to form two phases, and subsequent distillation to isolate pure monochloro-trifluoropropenes, utilizing azeotropic distillation columns to achieve separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional distillation methods are used to separate monochloro-trifluoropropenes from hydrogen fluoride, then separation is attempted, but the similar boiling points of these compounds make effective separation difficult
Solution Approach 1:
The invention changes the physical state parameter of the mixture by cooling it below its dew point temperature, transforming the vapor-phase distillation problem into a liquid-phase separation problem. This parameter change enables separation based on liquid-liquid equilibrium rather than vapor-liquid equilibrium, overcoming the limitation of similar boiling points.
Solution Approach 2:
The invention utilizes phase transition by cooling the condensed overhead stream to temperatures below its dew point, causing it to separate into two liquid phases. This phase transition creates a separation mechanism based on immiscibility rather than volatility differences, effectively bypassing the similar boiling point issue.
2Quantity of substance
If the overhead stream from the fluorination reactor is directly separated, then hydrogen chloride removal is needed, but the presence of HCl along with the azeotropic mixture complicates the separation process
Solution Approach 1:
The invention performs preliminary separation by removing hydrogen chloride through a dedicated wash column before the mixture undergoes phase separation. This preliminary action simplifies subsequent processing by eliminating the corrosive HCl component early in the process train, preventing complications in the liquid-liquid separation and downstream distillation steps.
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 effectively isolates pure monochloro-trifluoropropenes by creating phases with significant differences in composition, allowing for the separation of 1233zd from HF, even when they form azeotropes, thereby overcoming the boiling point similarity issue.
Implementation Method 1
distilling a reaction mixture including hydrogen fluoride, monochloro-trifluoropropene, and hydrogen chloride to remove hydrogen chloride as overhead
Implementation Method 2
cooling the bottoms stream to form two phases, and separating said two liquid phases in a liquid phase separator into a first light phase comprising hydrogen fluoride in excess over an azeotrope and a second heavy phase comprising an excess of monochloro-trifluoropropene over an azeotrope
Implementation Method 3
distilling said first light phase in a distillation column to produce a top stream of an azeotrope of monochloro-trifluoropropene and hydrogen fluoride and a bottoms stream of hydrogen fluoride
Data Source
Figure 1
AI summary
The invention relates to a process for separating monochloro-trifluoropropenes such as HCFC-1233 from azeotrope or azeotrope like combinations with HF. The process employs a cold, liquid phase separations and multiple azeotropic distillation trains.